IMI-The Dynamic Choroid: New Insights, Challenges, and Potential Significance for Human Myopia

Aqueous humour concentrations of HB-EGF, EGF and VEGF-A and axial length in humans

PURPOSE

To investigate relationships between the intraocular concentrations of heparin-binding epidermal growth factor (HB-EGF), epidermal growth factor (EGF) and vascular endothelial growth factor A (VEGF-A) in dependence on axial length in humans.

DESIGN

Clinical interventional cohort study.

PARTICIPANTS

Patients with cataract who underwent routine cataract surgery. Inclusion criterion was the absence of any retinal or optic nerve disease except for myopic macular degeneration (MMD) without myopic choroidal neovascularization.

METHODS

Using a Luminex system, we measured the concentrations of HB-EGF, EGF and VEGF-A in aqueous humour samples taken from patients during cataract surgery.

MAIN OUTCOME MEASURES

Intracameral concentration of EGF, HB-EGF and VEGF; Axial length.

RESULTS

The study included 68 patients (age: 61.1 ± 11 years; range: 44-85 years) with a mean axial length of 27.11 ± 3.11 mm (range: 22.09-35.64 mm). The HB-EGF concentration (mean: 3.17 ± 0.99 pg/mL) increased with longer axial length (β = 0.43; p < 0.001) and was not associated with age (p = 0.10) and intracameral EGF concentration (p = 0.22). The EGF concentration (mean: 0.22 ± 0.12 pg/mL) increased with longer axial length (β = 0.35; p = 0.004) and higher prevalence of advanced MMD (β = 0.35; p = 0.008) and was not associated with age (p = 0.28) and intracameral VEGF-A concentration (p = 0.09). The VEGF-A concentration (mean: 118 ± 150 pg/mL) decreased with longer axial length (β = -0.54; p < 0.001), higher intracameral concentration of HB-EGF (β = -0.26; p = 0.03) and lower MMD prevalence (β = -0.31; p = 0.02) and was not associated with age (p = 0.47) and intracameral EGF concentration (p = 0.09).

CONCLUSIONS

With the concentrations of HB-EGF and EGF increasing with longer axial length, the study supports a potential role of the EGFR signalling pathway activation in human axial myopia. The inverse relationship between VEGF-A concentration and longer axial length agrees with a protective effect of axial myopia against diabetic retinopathy and age-related macular degeneration.

Spatial heterogeneity of corneal biomechanical properties in myopia at nanoscale: A preliminary study

PURPOSE

To investigate the spatial heterogeneity of the corneal biomechanical properties in individuals with non-high and high myopia.

METHODS

Atomic force microscopy was used to quantify the region-dependent elastic modulus (E) of 34 corneal lenticules from keratorefractive lenticule extraction surgery. The local E values of the central region, as well as the superior, inferior, nasal, and temporal points at the pericentral region, were measured. Differences between non-high myopia (-6.0 D < spherical equivalent [SE] ≤ -0.5 D) and high myopia (SE ≤ -6.0 D) were compared.

RESULTS

E was significantly higher in the non-high myopia group than in the high myopia group (P < 0.0001). In non-high myopia, the central cornea exhibited a higher E than its pericentral counterpart (P < 0.0001), and the pericentral region E was higher in the horizontal direction than in the vertical direction (P = 0.0393). However, these values converged to be similar in high myopia (P = 0.5973, P = 0.7799). No significant differences in E were found between the superior and inferior pericentral corneas, nor between the nasal and temporal in both non-high (P = 0.0931, P = 0.1800) and high myopia (P = 0.5154, P = 0.1007). The E values of central and pericentral cornea were positively correlated with the mean radius of the posterior corneal surface (r = 0.3747, P = 0.0290; r = 0.3961, P = 0.0204).

CONCLUSION

In non-high myopia, region-dependent corneal biomechanics revealed higher stiffness centrally than pericentrally, with pericentral cornea stiffer horizontally than vertically. High myopia exhibited a reduced E and a gradual loss of spatial heterogeneity. Emphasizing spatial heterogeneity is crucial for a comprehensive understanding of the biomechanical behavior in myopia.

Unilateral Acute Serous Retinal Detachment with Pachychoroid Following Postpartum Haemorrhage: A Case Report

PURPOSE

To elucidate the development and resolution of a unilateral acute serous retinal detachment (SRD) in a healthy patient following a complicated postpartum haemorrhage. This underscores the impact of systemic volume alterations and stress-induced factors on retinal fluid balance.

BACKGROUND

Postpartum SRD is observed in individuals with pre-eclampsia and patients with previously diagnosed central serous chorioretinopathy, both attributed to hormonal and volumetric fluctuations during pregnancy.

CASE DESCRIPTION

A 33-year-old woman presented with metamorphopsia and blurry vision in her left eye 24 hours following childbirth complicated by haemorrhagic shock. Notably, the patient had pre-delivery physiological vital signs with no alterations of consciousness, arterial blood pressure, or renal function. At presentation, the visual acuity in the left eye was 1.0 decimals and the anterior segment was within normal limits, while fundoscopy revealed a slight alteration in the foveal reflex. Spectral-domain optical coherence tomography (SD-OCT) revealed the presence of a dome-shaped SRD in the foveal region with a central foveal thickness of 279 µm and pachychoroid at 410 µm retro-foveally. The examination of the right eye and SD-OCT were unremarkable, except for the presence of pachychoroid at 367 µm retro-foveally. No treatment was initiated. At 48 hours, SD-OCT scans revealed complete resorption of the SRD in the left eye with a persistent focal alteration in the foveal region of the ellipsoid zone. Retro-foveal choroid thickness (RCT) was unchanged. At one month, visual acuity remained stable, and the patient was no longer symptomatic. The left eye SD-OCT revealed a reduction in CFT (279 µm vs. 224 µm, a 20.2% reduction) and RCT (410 µm vs. 360 µm, a 14.6% reduction) compared to baseline. Remarkably, the right eye also exhibited a 14.9% reduction in RCT (367 µm vs. 309 µm).

CONCLUSION

This case highlights the role that postpartum systemic changes and complications can play in the occurrence of retinal and choroidal changes. We believe that in this specific case, the development of acute SRD was probably due to oncotic fluctuations related to the hypovolaemic status following postpartum haemorrhage. This also emphasises the utility of SD-OCT for assessment and follow-up monitoring, providing valuable insights into retinal and choroidal changes over time.

Cone mosaic in eyes with varied axial length using adaptive optics scanning laser ophthalmoscopy

BACKGROUND

Abnormalities in cone photoreceptor topography are closely associated with the development of various ocular diseases, including axial myopia. Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) enables high-resolution, single-cell imaging of the living human retina.

METHODS

This study aimed to investigate the potential relationship between cone topography and axial myopia using a commercial AOSLO system. A total of 74 participants (148 eyes; 30 men, 40.5 %) with a mean age of 31.8 ± 10.4 years were included. Cone mosaics were imaged at 3° and 5° eccentricities of the fovea centralis. The relationships between cone parameters (linear cone density, cone spacing, cone dispersion, and cone regularity) and axial length were analyzed.

RESULTS

Linear cone density significantly decreased with increasing axial length at both 3° and 5° eccentricities (all P < 0.001). Cone spacing significantly increased with greater axial length and reduced cone density. After adjusting for axial length, cone spacing was significantly associated only with linear cone density at both 3° and 5° eccentricities (all P < 0.001). Cone dispersion significantly increased with longer axial length and lower cone density. After adjusting for axial length, cone dispersion remained significantly associated with linear cone density only at the inferior 3° (β = -0.43, P = 0.014) and inferior 5° eccentricities (β=-0.4, P = 0.003). Cone regularity significantly increased with higher linear cone density at certain 3° eccentricities (nasal: β=0.34, P < 0.001; temporal: β=0.25, P = 0.006; inferior: β = 0.2, P = 0.04) and significantly decreased with longer axial length at temporal 5° eccentricity (β = -0.57, P < 0.001).

CONCLUSIONS

Linear cone density was significantly reduced in axial myopia. The uniformity of cone distribution was disrupted as a result of the reduction in cone density. Additionally, cone regularity was significantly diminished in axial myopia, potentially due to the direct effects of axial elongation at 5° eccentricity or reductions in cone density at 3° eccentricity.

Age and gender-related changes in choroidal thickness: Insights from deep learning analysis of swept-source OCT images

BACKGROUND

The choroid is a vital vascular layer of the eye, essential for maintaining ocular health. Understanding its structural variations, particularly choroidal thickness (CT), is crucial for the early detection of diseases, such as age-related macular degeneration (AMD), high myopia (HM), and diabetes mellitus (DM). Recent advancements in deep learning have significantly improved the segmentation and measurement of choroidal layers.

OBJECTIVE

This study aims to investigate age- and gender-related changes in CT and its components through deep learning analysis of swept-source optical coherence tomography (SS-OCT) images.

METHODS

A total of 262 participants (136 females and 126 males) were recruited from Peking University International Hospital. Exclusion criteria included ocular pathologies and systemic conditions. SS-OCT was utilized for CT, Sattler layer-choriocapillaris complex thickness (SLCCT), and Haller layer thickness (HLT) measurements. auto-measurement method, based on deep learning algorithms, ensured accuracy. Ethics approval and informed consent were obtained from all participants.

FINDINGS

Significant thinning of CT and SLCCT was observed after the age of 60, with HLT declining after the age of 30. Females exhibited marked thinning between the ages of 40 and 50, while males began to show thinning at age 60.

CONCLUSION AND IMPLICATIONS

This research highlights age-related changes in choroidal thickness, with a particular emphasis on gender differences. The findings suggest that females experience earlier thinning, potentially attributable to hormonal changes. Additionally, the study validates the efficiency of deep learning algorithms in measuring choroidal thickness, thereby enhancing the reliability of clinical practice.

Topical review: Potential mechanisms of atropine for myopia control

SIGNIFICANCE

Atropine is effective at slowing myopia progression in children, but the mechanism of action by which it controls myopia remains unclear. This article is an evidenced-based review of potential receptor-based mechanisms by which atropine may act to slow the progression of myopia.The rising number of individuals with myopia worldwide and the association between myopia and vision-threatening ocular pathologies have made myopia control treatments one of the fastest growing areas of ophthalmic research. High-concentration atropine (1%) is the most effective treatment for slowing myopia progression to date; low concentrations of atropine (≤0.05%) appear partially effective and are currently being used to slow myopia progression in children. While significant progress has been made in the past few decades in understanding fundamental mechanisms by which atropine may control myopia, the precise characterization of how atropine works for myopia control remains incomplete. It is plausible that atropine slows myopia via its affinity to muscarinic receptors and influence on accommodation, but animal studies suggest that this is likely not the case. Other studies have shown that, in addition to muscarinic receptors, atropine can also bind, or affect the action of, dopamine, alpha-2-adrenergic, gamma-aminobutyric acid, and cytokine receptors in slowing myopia progression. This review summarizes atropine's effects on different receptor pathways of ocular tissues and discusses how these effects may or may not contribute to slowing myopia progression. Given the relatively broad array of receptor-based mechanisms implicated in atropine control of myopia, a single mode of action of atropine is unlikely; rather atropine may be exerting its myopia control effects directly or indirectly via several mechanisms at multiple levels of ocular tissues, all of which likely trigger the response in the same direction to inhibit eye growth and myopia progression.

Retrobulbar Hyaluronidase in Hyaluronic Acid-Induced Ocular Vascular Occlusion: Efficacy, Challenges, and Implications for Clinical Practice

INTRODUCTION

Ophthalmic vascular occlusion due to hyaluronic acid (OVOH) is a rare but devastating complication of cosmetic filler injections, often resulting in severe vision loss.

MATERIALS

The methodology involved a systematic search across PubMed, NCBI, Google Scholar, and Cochrane to investigate factors influencing central retinal artery occlusion (CRAO) caused by fillers. Searches focused on "eye vascular anatomy," "ocular physiology in response to ischemia," "components AND hyaluronic acid AND inflammation," "recovery from blindness associated with fillers," "retrobulbar technique," and "hyaluronidase degradation AND fillers." This review examines the pathophysiology, clinical presentation, and management of OVOH by synthesizing findings from case reports, clinical studies, and experimental research. It elucidates retinal vascular anatomy, HA embolization mechanisms, and treatment efficacy, highlighting the critical importance of timely intervention.

RESULTS

OVOH typically presents with rapid vision loss within minutes of HA injection, often accompanied by severe ocular pain. The primary treatment, hyaluronidase (HYAL), is most effective when administered early, although retrobulbar HYAL shows limited overall success. Factors such as ischemia duration and the presence of cilioretinal arteries significantly influence retinal survival and recovery. The review discusses the complexities of retinal hypoxia and the implications of various intervention strategies.

CONCLUSION

Timely intervention is crucial for managing OVOH. Although retrobulbar HYAL remains a key treatment option, its effectiveness varies and necessitates optimization. Early and accurate diagnosis is essential, underscoring the need for further research to refine treatment strategies and improve outcomes for patients with retinal vascular occlusions.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Effectiveness of Low-Level Red Light in Controlling Myopia Progression in Children: A Systematic Review and Meta-Analysis

This study aimed to evaluate the effectiveness of low-level red light (LLRL) therapy compared to single-vision spectacles (SVS) in controlling myopia progression, focusing on spherical equivalent refraction (SER), axial length (AL), and subfoveal choroidal thickness (SFCT). A comprehensive search was conducted across PubMed, Cochrane Library, ScienceDirect, and Web of Science, including only randomized controlled trials (RCTs) involving myopic patients aged 16 years or younger. Mean differences were calculated with 95% CIs, and the I² statistic was used to assess heterogeneity among studies. The meta-analysis included 11 RCTs. At three months, significant differences were observed between LLRL and SVS in SER (estimate: 0.225; 95% CI: 0.042, 0.408; p = 0.016) and AL (estimate: -0.137; 95% CI: -0.280, 0.007; p = 0.062). At six months, significant differences were noted in SER (estimate: 0.450; 95% CI: 0.351, 0.550; p < 0.001), AL (estimate: -0.179; 95% CI: -0.278, -0.079; p < 0.001), and SFCT (estimate: 35.281; 95% CI: 23.230, 47.331; p < 0.001). By 12 months, the differences remained significant for SER (estimate: 0.806; 95% CI: 0.675, 0.937; p < 0.001) and AL (estimate: -0.294; 95% CI: -0.416, -0.172; p < 0.001). These findings suggest that LLRL therapy effectively reduces myopia progression in children, as indicated by improvements in SER, slower AL growth, and stabilization or slight increases in SFCT. However, further studies are necessary to determine the optimal dosage, long-term safety, and overall efficacy of LLRL therapy.

Comprehensive Visualization of Choroidal Alterations in Thyroid Eye Disease With Ultra-Widefield OCT Angiography

Purpose

To evaluate choroidal and optic disc alterations in eyes with thyroid eye disease (TED) compared with healthy eyes by using TowardPi widefield optical coherence tomography angiography (OCTA).

Methods

This was a retrospective cross-sectional cohort study. A total of 112 participants (60 TED patients and 52 healthy controls) underwent TowardPi widefield OCTA, which provided detailed demographic and clinical data. Three-dimensional choroidal data, including thickness, vascular metrics, and optic disc measurements, were obtained from the built-in software.

Results

The study included 24 eyes with dysthyroid optic neuropathy (DON), 24 eyes with active non-DON TED, 71 eyes with inactive TED, and 104 healthy eyes. Choroidal thickness significantly decreased in the optic disc region during the DON phase (148.71 ± 78.98 µm) compared to normal eyes (182.35 ± 51.98 µm) and inactive TED eyes (191.34 ± 58.86 µm) (P = 0.030). In DON, choroidal stromal volume was reduced (34,183.81 ± 10,649.01 × 106 µm3) compared to normal (46,339.53 ± 16,711.99 × 106 µm3) (P = 0.002), whereas the choroidal vascular index increased (42.67% ± 3.41%) compared to normal (38.53% ± 6.35%) (P = 0.002). Optic disc area increased in DON (1.99 ± 1.24 mm2) compared to inactive TED (1.39 ± 0.38 mm2) (P < 0.001), along with reduced retinal nerve fiber layer blood-flow density in DON (45.09% ± 3.07%,) compared to normal (47.84% ± 1.41%) (P < 0.001).

Conclusions

This study highlights the critical role of choroidal and optic disc alterations in TED pathophysiology and underscore the utility of widefield OCTA in identifying these changes, particularly in DON-risk patients.

Differential impact of combined therapy and monotherapy with 0.05% atropine eyedrops and dual focus contact lenses on choroid

PURPOSE

To investigate changes in the choroid and axial length (AL) during one month of combined therapy and monotherapy with 0.05% atropine and dual-focus soft contact lens (DFCL), and the impact after discontinuation.

METHODS

Myopic adults randomly received three interventions: 0.05 % atropine, DFCL, and 0.05 % atropine combined with DFCL. Choroidal thickness (ChT), choroidal vascularity index (CVI) and AL were measured at baseline, 3, 7, 14, and 30 days after intervention, and 1, 2, 7, 14, and 30 days after discontinuation.

RESULTS

The ChT thickened and AL decreased after one month of combination therapy (24.19 ± 4.13 μm, P = 0.001; -40.35 ± 9.55 μm, P = 0.024) or 0.05 % atropine (20.52 ± 4.35 μm, P = 0.008; -8.07 ± 7.22 μm, P = 0.002) but not DFCL (8.95 ± 4.25 μm, P > 0.999; -14.89 ± 7.28 μm, P > 0.999). The increase in ChT and decrease in AL persisted for 2 days after 0.05 % atropine was discontinued, persisted for 7 days and 14 days after combination therapy was discontinued. There was no significant change in the CVI after one month use or withdrawal of any intervention (P > 0.999). After one month of combination therapy, significant correlations were observed between the baseline CVI and changes in ChT (r = 0.485, P = 0.035) or AL (r = -0.589, P = 0.008).

CONCLUSION

Monotherapy involving 0.05% atropine or the combination of 0.05% atropine with DFCL significantly affected ChT thickening and AL shortening. These changes were maintained for a longer duration post combination intervention. The baseline CVI was associated with changes in ChT and AL during combination treatment.

Choroidal thickening and retinal dopamine increase in mice at high altitude

The mechanisms underlying the low incidence of myopia at high altitudes remain unclear. Choroidal thickness and the dopaminergic system have been shown to be closely associated with myopia development. This study aimed to investigate the effects of high altitude exposure on choroidal thickness and the dopaminergic system. Mice were subjected to acute hypobaric hypoxia at an altitude of 5000 m for durations ranging from 2 to 72 h, as well as chronic exposure at an altitude of 3670 m for a period of 3 months. Choroidal thickness was assessed using hematoxylin and eosin (H&E) staining of ocular tissues. The retinal dopamine (DA) levels and its primary metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), were quantified via high-performance liquid chromatography (HPLC). The expression levels of dopamine D1 receptor (D1R) and dopamine D2 receptor (D2R) were evaluated using immunofluorescence techniques. Study results indicated that choroidal thickness significantly increased after 6 h of high altitude exposure. Retinal dopamine levels showed significant increases in both the 2-10 h and 3 months high altitude groups. Conversely, retinal DOPAC levels decreased in the 2 h and 4 h groups but increased significantly at 72 h. Following high altitude exposure, D1R expression correlated positively with DA levels, while D2R expression exhibited a negative correlation. In conclusion, high-altitude exposure is associated with significant increases in choroidal thickness and retinal DA levels, with D1R and D2R expression patterns varying in response to changes in retinal DA. These findings may represent a key molecular mechanism contributing to the lower incidence of myopia observed at high altitudes.

Short-term choroidal changes as early indicators for future myopic shift in primary school children: results of a 2-year cohort study

BACKGROUND

To assess predictive value of short-term choroidal changes for future myopic shift in children.

METHODS

577 eyes of 289 primary school children were prospectively followed for 2 years. Cycloplegic refractions at baseline, 1 year and 2 years, and choroidal measurements by optical coherence tomography at baseline and 3 months, were used for analyses. Myopic shift was defined as refraction change of at least -0.50 dioptre/year, at 2 years compared with baseline.

RESULTS

228 participants (455 eyes) completed 2-year follow-up. Approximately 37.6% of 311 initially non-myopic eyes and 73.6% of 144 initially myopic eyes developed a myopic shift. Notably, at 3 months greater reductions were found in initially myopic eyes with myopic shift, than in those without myopic shift-in choroidal thickness (ChT), luminal area (LA), stromal area (SA) and total choroidal area (TCA), but no significant differences in any choroidal parameters were observed between non-myopic eyes, with and without myopic shift. Multivariable analyses showed that in myopic eyes, each percentage increase in ChT, LA, SA and TCA was associated with reduced odds of myopic shift (all p<0.001). Similar associations were observed in non-myopic eyes, with smaller effects than in myopic eyes. Adding a 3-month percentage change of each choroidal parameter to a basic model including age, gender, parental myopia and baseline refraction significantly improved the predictive performance in myopic eyes (area under the receiver operating characteristic curves increasing from 0.650 to approximately 0.800, all p<0.05), but not in non-myopic eyes.

CONCLUSION

Short-term choroidal changes could act as early indicators for future myopic shift in children.

Choroidal thickness under pilocarpine versus cyclopentolate

Bruch´s membrane (BM) is firmly connected posteriorly to the optic nerve head through the peripapillary choroidal border tissue, and anteriorly through the longitudinal ciliary muscle to the scleral spur. We assessed, whether a difference in the contractile state of the ciliary muscle influences the position of the posterior BM by lifting the posterior BM pole, i.e., induces changes in the subfoveal choroidal thickness (SFCT). Healthy young adult individuals received one drop of cyclopentolate 1% into their right eyes and one drop of pilocarpine 1% into their left eyes. Using optical coherence tomography (OCT), three examiners measured independently SFCT and choroidal thickness in the fundus midperiphery at baseline and 30 min after eye drop instillation. The study included 21 healthy individuals (age:21.9 ± 2.6 years; range:15.7-25.8 years; axial length:24.4 ± 1.2 mm). In the right eyes, SFCT changed by 8.7 ± 34.9 μm (examiner 1), -2.9 ± 18.6 μm (examiner 2), and 10.5 ± 21.8 μm (examiner 3), respectively, and the midperipheral choroidal thickness changed by -10.6 ± 25.9 μm (examiner 1), 0.9 ± 17.5 μm (examiner 2), and 4.2 ± 24.7 μm (examiner 3), respectively, without significant differences between the measurements taken before and after eye drop application (all P > 0.05). In the left eyes, SFCT changed by 5.8 ± 22.2 μm (examiner 1), 5.5 ± 36.5 μm (examiner 2), and 3.9 ± 29.5 μm (examiner 3), respectively, and the midperipheral choroidal thickness changed by -6.9 ± 47.9 μm (examiner 1), -3.5 ± 28.7 μm (examiner 2), and 16.0 ± 28.2 μm (examiner3), respectively, without significant differences between baseline and study end (all P > 0.05). Application of cyclopentolate 1% and of pilocarpine 1% did not result in a statistically significant change in choroidal thickness in young healthy adults.

The association between sleep duration and myopia among Chinese school-age students: mediation effect of physical activity

Background

This study aimed to investigate the relationship between sleep duration and myopia in school-age students, as well as to observe the role of physical activity as a mediating variable in sleep duration and myopia.

Methods

Using multistage stratified sampling, 26,020 school-age students in Jiangsu Province, ages 7-18, were selected for this cross-sectional survey. Each participant completed a standardized interview in which their were asked about their vision, level of physical activity and average hours of sleep per day over the past month. Visual acuity examinations were conducted by the testing team's ophthalmology professionals and they were categorized into two groups based on pre-set criteria: myopic and non-myopic. Sleep duration was classified into 3 categories: <8 h/d, 8-10 h/d, >10 h/d. The Pearson's chi-square tests were used to examine differences in the incidence of myopia among participants. Binary multifactorial logistic regression adjusted for potential confounding variables was used to examine the relationship between myopia and a variety of factors. The mediating effects of physical activity on sleep duration and myopia were analyzed using the AMOS model.

Results

In this study, the incidence of myopia was higher in females than in males, it also increased with age. Those who slept for <8 h/d had the greatest myopia rate (85.69%) compared with those who slept for≥8 h/d (p < 0.001). Sleep duration was found to be adversely correlated with myopia (sleep duration = 8-10 h/d: OR = 0.68, p < 0.01; sleep duration > 10 h/d: OR = 0.48, p < 0.01) after controlling for potential confounders like gender, age, and BMI-z score (Body Mass Index Score). Physical activity at a high intensity not moderate intensity was found to be protective factor against myopia. High-intensity physical activity also acted as a mediator in the negative association between sleep duration and myopia (a, b, c' all p < 0.05).

Conclusion

There is a negative correlation between sleep duration and myopia in school-age students, and that high-intensity physical activity mediates the relationship between sleep duration and myopia.

An Evidence-Based Narrative Review of Scleral Hypoxia Theory in Myopia: From Mechanisms to Treatments

Myopia is one of the dominant causes of visual impairment in the world. Pathological myopia could even lead to other serious eye diseases. Researchers have reached a consensus that myopia could be caused by both environmental and genetic risk factors. Exploring the pathological mechanism of myopia can provide a scientific basis for developing measures to delay the progression of myopia or even treat it. Recent advances highlight that scleral hypoxia could be an important factor in promoting myopia. In this review, we summarized the role of scleral hypoxia in the pathology of myopia and also provided interventions for myopia that target scleral hypoxia directly or indirectly. We hope this review will aid in the development of novel therapeutic strategies and drugs for myopia.

Evaluation of Choroidal Thickness and Choroidal Vascularity Index in Patients with Rheumatoid Arthritis

PURPOSE

To evaluate the choroidal vascularity index and choroidal thickness in patients with rheumatoid arthritis.

METHOD

This study is a case control study. Our study consists of a total of two groups, with 32 individuals diagnosed with rheumatoid arthritis (RA) and 32 healthy volunteers. The thickness of the subfoveal choroid was measured from the 500 micron (µm), 1000 µm, 1500 µm nasal aspect of the fovea, and 500µm, 1000µm, 1500 µm temporal and subfoveal thickness of the fovea. ImageJ version 1.53i (National Institutes of Health, Bethesda, MD, USA) from open access was used for choroidal vascular index calculation.

RESULTS

The mean age (p = 0.064) and gender distribution (p = 0.522) were not statistically different between these two groups. There was no difference between the groups in terms of visual acuity (p = 0.060), intraocular pressures (p=0.056), refractive errors (p = 0.418), and axial lengths (p = 0.280). Temporal 500 µm CT (p = 0.038), temporal 1000 µm CT (p = 0.010), and temporal 1500 µm CT (p = 0.005) differed significantly between the groups. The luminal area was significantly different between the RA group (842.71 ± 192.77) and the control group (957.78 ± 230.83) (p = 0.034). The choroidal vascularity index showed a significant difference between the RA group (64.99 ± 4.71) and the control group (67.34 ± 3.40) (p = 0.026). A significant difference was observed between the seronegative RA and the control group with temporal 1500 µm CT (p = 0.030), temporal 1000 µm CT (p = 0.023), and luminal area (p = 0.034).

CONCLUSION

We demonstrated thinning in CT and decreased CVI for the first time in RA patients by comparing it with the control group.

The effect of transient increase in intraocular pressure on subfoveal choroidal thickness

SIGNIFICANCE

Myopia prevalence has increased over the last few decades. Studies have documented that the choroid is considered an important biomarker in myopia development. As myopia and choroidal thinning are associated with increased glaucoma risk, understanding the role of the choroid in myopia and glaucoma is imperative.

PURPOSE

This study investigates the effect of transiently elevated intraocular pressure on axial length, subfoveal choroidal thickness, and central retinal thickness in emmetropes, low myopes, and high myopes.

METHODS

This study involved 29 young adults (23 ± 1 years), including 10 emmetropes (-0.50 D < SE < +0.50 D), 10 low myopes (-6.00 D < SE ≤ -0.50 D), and 9 high myopes (SE ≤ -6.00 D). Participants were fitted with modified swimming goggles for 5 minutes to transiently change intraocular pressure. Noncontact tonometry, optical biometry, and optical coherence tomography were used to measure intraocular pressure, axial length, central retinal thickness, and subfoveal choroidal thickness, respectively. Measurements were taken at before, during goggle wear, immediately after, and 3 minutes after goggles removal. Repeated-measures analysis of variance with Bonferroni adjustment was used to assess the effect of transiently changed intraocular pressure and to elucidate any differences between refractive groups in response to the intraocular pressure change.

RESULTS

Intraocular pressure increased by 1.7 ± 2.1 mmHg (p=0.002) from baseline, accompanied by axial elongation of 14 ± 21 μm (p = 0.012) and subfoveal choroidal thinning of 13 ± 15 μm (p=0.01). However, central retinal thickness did not change significantly (p>0.05). Most of the changes in the axial length were due to changes in the choroidal thickness. Observed changes returned to baseline immediately following goggles removal. There was no significant difference between refractive error groups' changes associated with the transient increase in intraocular pressure (p>0.05).

CONCLUSIONS

Transiently increased intraocular pressure caused temporary axial elongation and subfoveal choroidal thinning, with no significant differences between refractive groups. Further studies are required to assess the impact of long-term increased intraocular pressure on ocular components.

Efficacy in myopia control-The impact of rebound

PURPOSE

When myopia control treatment is discontinued, progression will increase, but does it revert to expected values based on the age and race of the child or does it accelerate further? The latter scenario is considered a rebound.

METHODS

A PubMed search was conducted with the words 'rebound' and 'myopia control', identifying further papers from reviews. Inclusion was limited to prospective studies with ≥6 months of treatment, ≥3 months of data following cessation and with axial length data, which allowed calculation of rebound. Nineteen studies were identified, comprising 24 treatment groups. In 10 studies, untreated control children were followed both throughout the treatment and cessation periods, allowing for a concurrent comparison group. In three studies, a control group was followed for 1 or 2 years and thereafter received the treatment under evaluation. Later, treatment ceased in the originally treated children. Finally, six studies were cross-over designs. For these latter two study designs, initial axial elongation and myopia progression in the control group were extrapolated to the cessation period, accounting for annual slowing. Values from durations of <1 year were annualised.

RESULTS

The mean annualised rebound was +0.05 ± 0.10 mm and -0.09 ± 0.24 D for axial length and myopia progression, respectively, and these were correlated (r2 = 0.59, p < 0.001). Rebound was associated with 1-year treatment efficacy (r2 = 0.43, p < 0.001). The mean annualised rebound with optical corrections was -0.01 ± 0.03 mm. Five of the six highest rebound values (≥0.14 mm) were from red light therapy and atropine studies. Rebound ranged from +0.03 to +0.14 mm for overnight orthokeratology.

CONCLUSIONS

Consistent with previous statements, no evidence for rebound was found for myopia control spectacles and soft contact lenses. Future research should explore the influence of age and magnitude of treatment efficacy on rebound.

Choroidal thickness in macular, nasal midperiphery, and temporal midperiphery regions and its relationship with axial length and refractive error

PURPOSE

This study aimed to investigate the choroidal thickness (ChT) distribution in adult myopic eyes, focusing on the macular, nasal midperiphery, and temporal midperiphery regions, and to explore its relationship with axial length (AL) and refractive error.

STUDY DESIGN

A cross-sectional, observational study.

METHODS

Twenty-nine eyes of 29 adult volunteers were examined. ChT was measured using high-speed swept-source optical coherence tomography covering an area of 50 degrees in three different regions: centered at macular, nasal side at 33 degrees, and temporal side at 33 degrees. Statistical analyses were performed to assess differences in ChT between regions and correlations with AL and spherical equivalent (SE).

RESULTS

ChT was found to be thickest in the macular region, followed by the nasal and temporal midperiphery regions. Significant correlations were observed between AL/SE and ChT in the macular and temporal regions, but not in the nasal region. The temporal midperiphery showed the strongest correlation with AL and SE.

CONCLUSION

This study revealed a nasal-temporal asymmetry in ChT distribution in myopic eyes, with the temporal midperiphery showing the thinnest ChT. The strong correlations between ChT in the temporal midperiphery and AL/SE suggest a role for the temporal choroid in axial elongation and myopia progression. These findings highlight the importance of considering peripheral ChT in understanding ocular growth and myopia management.

Association between choroidal microvasculature in the eye and Alzheimer's disease risk in cognitively healthy mid-life adults: A pilot study

INTRODUCTION

We explored associations between measurements of the ocular choroid microvasculature and Alzheimer's disease (AD) risk.

METHODS

We measured the choroidal vasculature appearing in optical coherence tomography (OCT) scans of 69 healthy, mid-life individuals in the PREVENT Dementia cohort. The cohort was prospectively split into low-, medium-, and high-risk groups based on the presence of known risk factors (apolipoprotein E [APOE] ε4 genotype and family history of dementia [FH]). We used ordinal logistic regression to test for cross-sectional associations between choroidal measurements and AD risk.

RESULTS

Choroidal vasculature was progressively larger between ordinal risk groups, and significantly associated with risk group prediction. APOE ε4 carriers had thicker choroids and larger vascularity compared to non-carriers. Similar trends were observed for those with a FH.

DISCUSSIONS

Our results suggest a potential link between the choroidal vasculature and AD risk. However, these exploratory findings should be replicated in a larger sample.

Highlights

Ocular choroidal microvasculature is of interest in relation to neurodegeneration due to its autonomic response to systemic, pathophysiological change.Choroidal changes in the prodromal stage of Alzheimer's disease (AD) are unexplored.The PREVENT Dementia cohort offers a unique, non-invasive study of the microvasculature in mid-life individuals at increased risk for developing AD.Significantly increased ocular choroidal vasculature was associated with increased risk (apolipoprotein E carrier and/or family history of dementia) for AD.These exploratory results suggest a potential association between the ocular choroidal vasculature and AD risk. However, findings should be replicated in a larger sample.

Role of caffeine in slowing progression of myopia: 1-year results from a prospective, longitudinal clinical trial

PURPOSE

To determine the role of topical caffeine in slowing progression of myopia, both as a standalone treatment and in combination with atropine.

METHODS

In a prospective, randomized, dispensing clinical trial, 96 children with myopia, aged 6-13 years, spherical equivalent (SE) from -0.50 diopters (D) to -6.00 D and astigmatism less than 2.00 D were randomly assigned to nightly use of either 2 % caffeine, 0.02 % atropine with 2 % caffeine (combination) or 0.02 % atropine eye drops. An additional 86 children with myopia were enrolled in a concurrent parallel group to wear single-vision (SV) spectacles. The primary outcomes were changes in SE and axial length (AL) over a period of 12 months for each group.

RESULTS

All groups progressed in myopia. At 12 months, the mean change in SE/AL was -0.76 ± 0.51 D / 0.37 ± 0.20 mm and -0.70 ± 0.55 D / 0.35 ± 0.23 mm with SV and 2 % caffeine, respectively. In comparison, progression was slower at -0.46 ± 0.50 D / 0.24 ± 0.19 mm and -0.47 ± 0.38 D / 0.23 ± 0.18 mm with atropine monotherapy and combination groups, respectively. Compared to the change in AL with SV, the change in AL was significantly less with 0.02 % atropine and the combination group (post hoc analysis, P = 0.024 and 0.007, respectively). Similarly, the change in SE was significantly less with 0.02 % atropine compared to the SV group (P = 0.027).

CONCLUSIONS

Used as a standalone treatment, topical 2 % caffeine did not slow myopia progression. When combined with atropine, caffeine had no impact on the efficacy of atropine in slowing myopia.

Two-year changes of macular choroidal thickness in response to 0.01% atropine eye drops: Results from the myopia outcome study of atropine in children (MOSAIC) clinical trial

PURPOSE

To investigate 2-year changes in macular choroidal thickness (ChT) in children receiving 0.01% atropine eyedrops and its relationship with spherical equivalent refraction (SER) progression and axial length (AL) elongation.

METHODS

A total of 250 myopic children aged 6-16 years (167%-0.01% atropine, 83-placebo) were enrolled in the MOSAIC (ISRCTN36732601) clinical trial. Participants with complete 2-year ChT (Topcon Triton Swept-Source OCT), SER, and AL data were included in this study. Changes in macular ChT at 2 years and associations with changes in SER and AL elongation were analysed using linear mixed models.

RESULTS

A total of 187 children (126%-0.01% atropine, 61-placebo) were included in the analysis. Choroidal thickness over 2 years was stable in the 0.01% atropine compared with placebo group, which exhibited consistent thinning in subfoveal (mean ± SE: 0.49 ± 2.22 μm vs. -9.46 ± 2.69 μm; p = 0.034), parafoveal (1.40 ± 1.73 μm vs. -8.11 ± 2.08 μm; p = 0.002), and perifoveal (0.80 ± 1.25 vs. -6.17 ± 1.69; p = 0.002) macular subfields. Choroidal thickening was observed in participants with slower axial eye growth and myopia progression, regardless of their treatment group. Mediation analysis indicated that atropine 0.01% had a significant effect on ChT, with 68.3% of the effect being direct and 31.7% mediated through axial length changes. For SER, the direct effect on ChT was 80%, with the remaining 20% mediated by SER changes.

CONCLUSIONS

Myopic participants treated with 0.01% atropine exhibited stable ChT over 2 years, whereas the placebo group showed consistent thinning. The effect of atropine 0.01% on ChT was only partially explained by axial length and SER changes, indicating a direct effect of atropine treatment on the choroid.

Structural changes in the retina and choroid in patients with different degrees of myopia

To observe the structural changes of retina and choroid in patients with different degrees of myopia. We recruited 219 subjects with different degrees of myopia for best corrected visual acuity, computer refraction, intraocular pressure, axial length (AL), optical coherence tomography (OCT) imaging, and other examinations. Central macular retinal thickness (CRT), subfoveal choroidal thickness (SFCT), nasal retinal thickness (NRT), temporal retinal thickness (TRT), nasal choroidal thickness (NCT) and temporal choroidal thickness (TCT) were measured by optical coherence tomography. ImageJ software was used to measure the retinal area and choroidal area (CA), and Niblack was used to binarize all OCT images to measure the choroidal vessel area (CVA) and choroidal matrix area (CMA). We found that CRT, SFCT, NRT, TRT, NCT, TCT, CA, CVA, and CMA were significantly reduced in the pathological myopia (PM) group. AL was negatively correlated with NRT, SFCT, CMA, CVA and choroidal stromal index. There was a significant positive correlation between AL and choroidal vascular index. The choroidal vascular index in the PM group was significantly increased compared with the other groups. We established a univariate receiver operating curve to analyze the diagnostic value of all parameters for PM. Spherical equivalent, AL, SFCT, TCT, NCT, CA, CVA, and CMA had high diagnostic value for PM, among which CMA had the highest accuracy. There are changes in choroidal structure in adults with different degrees of myopia. Choroidal thickness, CVA and CMA decrease significantly with the increase of myopia, and are correlated with AL. The decrease of CMA has higher diagnostic value in myopia.

Understanding how the immune system environment is controlled in high myopia cases

High myopia (HM) is characterized by a significant extension of the eye axis; it has emerged as a serious global public health issue recently. In addition to causing severe visual impairment, HM is associated with several problems that may compromise an individual's vision. Although genetic and environmental factors in HM have been extensively investigated, increasing evidence implicates the immune system and its microenvironment in its pathogenesis. In this review, we explore the complex interactions between cytokines, immune cells, and the eye environment to elucidate the complex processes controlling the immune response in HM. Furthermore, we investigated treatments modulating the immune response and alleviating the progression of HM and its complications. Through a review of the current relevant studies, we highlight the critical functions of the immune system in the multifactorial development of HM. With the evolving understanding of the immune system's involvement in HM, this review provides a valuable resource to clinicians and researchers to develop targeted interventions and personalized treatments for individuals with this vision-threatening condition.

Retinal glia in myopia: current understanding and future directions

Myopia, a major public health problem, involves axial elongation and thinning of all layers of the eye, including sclera, choroid and retina, which defocuses incoming light and thereby blurs vision. How the various populations of glia in the retina are involved in the disorder is unclear. Astrocytes and Müller cells provide structural support to the retina. Astrogliosis in myopia may influence blood oxygen supply, neuronal function, and axon diameter, which in turn may affect signal conduction. Müller cells act as a sensor of mechanical stretching in myopia and trigger downstream molecular responses. Microglia, for their part, may exhibit a reactive morphology and elevated response to inflammation in myopia. This review assesses current knowledge about how myopia may involve retinal glia, and it explores directions for future research into that question.

Effects of computer-generated patterns with different temporal and spatial frequencies on choroidal thickness, retinal dopamine and candidate genes in chickens wearing lenses

Purpose

Changes in choroidal thickness (ChT) are proposed to predict myopia development but evidence is mixed. We investigated time courses of choroidal responses, following different types of dynamic artificial stimulation in chicks with and without spectacle lenses, as well as changes in retinal dopamine metabolism and expression of candidate genes.

Methods

Chicks were kept in an arena surrounded by computer monitors presenting dynamic checkerboard fields of small, medium and large size. Fields were displayed with different cycle frequencies, as ON (rapid rise, slow decay) or OFF (slow rise, rapid decay) temporal luminance profile. Refractive errors, ocular biometry and ChT were assessed. Dopamine metabolism and candidate gene expression levels were also measured. Stimuli were applied for (1) 3 h with no lens, (2) 3 h and monocular treatment with -7D or +7D lenses, (3) 3 or 7 days.

Results

(1) The smallest fields caused the largest decrease in ChT. (2) Negative lens treatment induced on average 11.7 μm thinner choroids. ChT thinning was enhanced by 10 Hz-ON medium field size flicker which also reduced choroidal thickening with positive lenses. (3) With prolonged treatment, the choroid recovered from initial thinning in all groups although to varying degrees which were dependent on stimulus parameters. Relative ChT changes were positively correlated with the vitreal level of dopamine metabolites. Retinal EGR-1 mRNA level was positively correlated with choroidal thickness. Retinal melanopsin mRNA was increased by 10 Hz-ON stimulation and choroidal BMPR1A mRNA increased with 10 Hz-OFF stimulation. On average, early choroidal thinning did not predict the amount of negative lens-induced eye growth changes after 7 days, whereas later ChT changes showed a weak association.

Conclusion

Negative lenses caused long-lasting choroidal thinning, with some recovery during lens wear, especially after stimulation with 10 Hz. The dynamic stimuli modulated choroidal thinning but effects were small. There was little difference between ON and OFF stimulation, perhaps because the checkerboard patterns were too coarse. 10 Hz cycle frequency increased dopamine release. Less dopamine was correlated with thinner choroids. Result do not exclude a predictive value of choroidal thickening for future refractive development since we almost exclusively tested choroidal thinning effects.

The Macular Choroidal Thickness in Danish Children with Myopia After Two-Year Low-Dose Atropine and One-Year Wash-Out: A Placebo-Controlled, Randomized Clinical Trial

INTRODUCTION

Our aim in this work was to investigate the macular choroidal thickness (ChT) changes in 6-12-year-old Danish children with myopia during 2 years of low-dose atropine treatment and 1-year wash-out vs. placebo in an investigator-initiated, placebo-controlled, double-blind randomized clinical trial.

METHODS

Ninety-seven participants were randomized to either 0.01% for 2 years, 0.1% loading dose for 6 months followed by 0.01% for 18 months, or placebo, then a 1-year wash-out. The primary outcome was ChT in the sub-foveal and inner and outer superior, nasal, inferior, and temporal sectors. The secondary outcome was axial length (AL). Outcomes were measured at baseline and 6, 12, 24, and 36 months. One-way analysis of variance was used to detect baseline ChT differences between AL-stratified groups (< 24 mm, 24-25 mm, or > 25 mm). To determine the longitudinal changes in ChT and its effect on AL, all eyes were included in linear mixed modeling with individual eyes nested in the study ID as a random effect.

RESULTS

Longer eyes had significantly thinner ChT in all choroidal sectors (adj-P < 0.01) at baseline. There was no statistically significant change in any ChT sector after 3 years in the placebo group. Sub-foveal and nasal ChT in the 0.1% loading dose and 0.01% group were not significantly different from placebo after 2-year treatment. In the placebo group, a 1-mm increase in AL was significantly associated with a 47-µm thinner nasal ChT after 3 years (95% confidence interval (CI): - 55; - 38, adj-P < 0.001). A 10-µm thicker nasal choroid at baseline was associated with 0.13 mm (95% CI: 0.009; 0.017, adj-P < 0.001) less 3-year axial elongation.

CONCLUSIONS

The ChT in Danish children with myopia remained stable over the 3-year follow-up. A thinner choroid at myopia onset might predispose to increased axial elongation. Treatment with 0.01% atropine did not change the ChT. We speculate that low-dose atropine does not primarily reduce myopia progression via a choroidal mechanism.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT03911271.

High correlated color temperature white light-emitting diodes disrupt refractive development in guinea pigs

Ubiquitous white light-emitting diodes (LEDs) possess optical properties that differ from those of natural light. This difference can impact visual perception and biological functions, thus potentially affecting eye health. Myopia, which leads to visual impairments and potentially irreversible vision loss or blindness, is the most prevalent refractive error worldwide. Ambient light has been found to be a significant factor in refractive development. The overlap between the commonly utilized of white LEDs and the rapid increase in the prevalence of myopia raises suspicions that white LEDs may represent hidden visual cues. To clarify the potential effects of white LEDs on refractive development, we exposed guinea pigs to different forms of artificial lighting over a period of eight weeks. We found that exposure to white LEDs with a high correlated color temperature (CCT) of approximately 5000 K can induce significant myopic shifts in guinea pigs, along with a decrease in collagen accumulation in the sclera. Additionally, this exposure was found to significantly reduce choroidal tissue thickness in guinea pigs. Our study findings indicate that high CCT white LEDs disrupt refractive development in guinea pigs. These results suggest that high CCT white LEDs might similarly affect refractive development in humans, highlighting the need for further clinical investigation.

Light-sensitive Ca2+ signaling in the mammalian choroid

The choroid is the thin, vasculature-filled layer of the eye situated between the sclera and the retina, where it serves the metabolic needs of the light-sensing photoreceptors in the retina. Illumination of the interior surface of the back of the eye (fundus) is a critical regulator of subretinal fluid homeostasis, which determines the overall shape of the eye, but it is also important for choroidal perfusion. Noted for having some of the highest blood flow rates in the body, the choroidal vasculature has been reported to lack intrinsic, intravascular pressure-induced (myogenic) autoregulatory mechanisms. Here, we ask how light directly regulates choroid perfusion and ocular fluid homeostasis, testing the hypothesis that light facilitates ocular fluid absorption by directly increasing choroid endothelial permeability and decreasing choroid perfusion. Utilizing ex vivo pressurized whole-choroid and whole-eye preparations from mice expressing cell-specific Ca2+ indicators, we found that the choroidal vasculature has two intrinsically light-sensitive Ca2+-signaling mechanisms: One increases Ca2+-dependent production of nitric oxide in choroidal endothelial cells; the other promotes vasoconstriction through Ca2+ elevation in vascular smooth muscle cells. In addition, we found that choroidal flow, or pressure, modulates endothelial and smooth muscle photosensitivity and trans-retinal absorption of fluid into the choroid. These results collectively suggest that the choroid vasculature exhibits an inverted form of autoregulatory control, where pressure- and light-induced mechanisms work in opposition to regulate blood flow and maintain fluid balance in response to changes in light and dark, aligning with the metabolic needs of photoreceptors.

Biomarkers: Promising Tools Towards the Diagnosis, Prognosis, and Treatment of Myopia

The prevalence of myopia, especially high myopia, continues to increase in several parts of the world. Thus, the use of biomarkers for early myopia detection would be highly valuable for clinical practice aiding in the prevention and myopia control management. The identification of biomarkers that can predict the risk of myopia development, severity of myopia, and treatment response are of paramount significance. In this review, we present the current state of research on biomarkers and myopia, highlighting the challenges and opportunities in biomarkers research for myopia. Although myopia biomarkers may have a role as early indicators of myopia or treatment response, the adoption of biomarkers into myopia clinical practice may only be done when tests have high accuracy, are easily measurable, minimally invasive, and acceptable to parents, children, and eye care professionals. Large consortia studies are necessary to validate biomarkers and translate evidence into clinical practice.

Ocular biometric responses to simulated polychromatic defocus

Evidence from human studies of ocular accommodation and studies of animals reared in monochromatic conditions suggest that chromatic signals can guide ocular growth. We hypothesized that ocular biometric response in humans can be manipulated by simulating the chromatic contrast differences associated with imposition of optical defocus. The red, green, and blue (RGB) channels of an RGB movie of the natural world were individually incorporated with computational defocus to create two different movie stimuli. The magnitude of defocus incorporated in the red and blue layers was chosen such that, in one case, it simulated +3 D defocus, referred to as color-signed myopic (CSM) defocus, and in another case it simulated -3 D defocus, referred to as color-signed hyperopic (CSH) defocus. Seventeen subjects viewed the reference stimulus (unaltered movie) and at least one of the two color-signed defocus stimuli for ∼1 hour. Axial length (AL) and choroidal thickness (ChT) were measured immediately before and after each session. AL and subfoveal ChT showed no significant change under any of the three conditions. A significant increase in vitreous chamber depth (VCD) was observed following viewing of the CSH stimulus compared with the reference stimulus (0.034 ± 0.03 mm and 0 ± 0.02 mm, respectively; p = 0.018). A significant thinning of the crystalline lens was observed following viewing of the CSH stimulus relative to the CSM stimulus (-0.033 ± 0.03 mm and 0.001 ± 0.03 mm, respectively; p = 0.015). Differences in the effects of CSM and CSH conditions on VCD and lens thickness suggest a directional, modulatory influence of chromatic defocus. On the other hand, ChT responses showed large variability, rendering it an unreliable biomarker for chromatic defocus-driven responses, at least for the conditions of this study.

Blue light stimulation of the blind spot in human: from melanopsin to clinically relevant biomarkers of myopia

The protective effects of time spent outdoors emphasize the major role of daylight in myopia. Based on the pathophysiology of myopia, the impact of blue light stimulation on the signaling cascade, from melanopsin at the blind spot to clinically relevant biomarkers for myopia, was investigated. Parameters and site of light stimulation are mainly defined by the photopigment melanopsin, that is sensitive to blue light with a peak wavelength of 480 nm and localized on the intrinsically photosensitive retinal ganglion cells (ipRGC) whose axons converge to the optic disc, corresponding to the physiological blind spot. Blue light at the blind spot (BluSpot) stimulation provides the opportunity to activate the vast majority of ipRGC and avoids additional involvement of rods and cones which may exert incalculable effects on the signaling cascade.Experimental studies have applied anatomical, histochemical, electrophysiological, imaging, and psychophysical methods to unravel the mode of action of BluSpot stimulation. Results indicate activation of melanopsin, improvement of contrast sensitivity, gain in electrical retinal activity, and increase of choroidal thickness following BluSpot stimulation. Short-term changes of clinically relevant biomarkers lead to the hypothesis that BluSpot stimulation may exert antimyopic effects with long-term application.

In vivo assessment of cone loss and macular perfusion in children with myopia

This study evaluated cone density (CD) in the macular region and assess macular perfusion in children with varying degrees of myopia. This was a prospective, cross-sectional, observational study. Children underwent confocal scanning laser ophthalmoscopy (cSLO), optical coherence tomography (OCT), and OCT angiography (OCTA) imaging. A built-in software was used to measure mean CD (cells/mm2), retinal vessel density, choriocapillaris perfusion area, and choroidal thickness (CT). The study included 140 eyes from children categorized into four groups: emmetropia (31 eyes), low myopia (44 eyes), moderate myopia (31 eyes), and high myopia (34 eyes). The high myopia group exhibited significantly lower macular CD than the emmetropia group (P < 0.05). Additionally, the high myopia group showed thinner CT and higher choriocapillaris perfusion area in the macular region than the emmetropia group (all P < 0.01). Macular CD was significantly correlated with age, spherical equivalent, axial length, and CT (all P < 0.05). Generalized linear models revealed CT as the independent factor associated with macular CD (Wald χ2 = 9.265, P = 0.002). Children with high myopia demonstrate reduced CD in the macular region, accompanied by reduced CT. These findings may have important implications for future myopia prevention and management strategies.

Axial length reduction and choroidal thickening with short-term exposure to cyan light in human subjects

PURPOSE

Given the potential role of light and its wavelength on ocular growth, this study investigated the effect of short-term exposure to red, cyan and blue light on ocular biometry in humans.

METHODS

Forty-four young adults and 20 children, comprising emmetropes and myopes, underwent 2-h sessions of cyan (507 nm), red (638 nm) and broadband white light on three separate days via light-emitting glasses. Additionally, young adults were exposed to blue light (454 nm) on an additional day. Axial length (AL) and choroidal thickness (CT) were measured in the right eye before the light exposure (0 min), after 60 and 120 min of exposure and 30 min after light offset using an optical biometer and optical coherence tomographer, respectively.

RESULTS

Compared to broadband light, exposure to red light resulted in a significant increase in AL (mean difference between white and red light at 120 min, +0.007 mm [0.002]), but no significant change in CT, while cyan light caused a significant AL reduction (-0.010 mm [0.003]) and choroidal thickening (+0.008 mm [0.002]) in young adults (p < 0.05). Blue light caused a significant decrease of -0.007 mm (0.002) in young adult eyes at 60 min (p < 0.05). In children, cyan light led to a significant reduction in AL (-0.016 mm [0.004]) and strong sustained choroidal thickening (+0.014 mm [0.004]) compared to broadband light at 120 min (p < 0.05). The effects of cyan light on AL and CT were found to be stronger in myopic young adults and emmetropic children. The opposing effects of red and cyan light on ocular biometry were similar between the two age groups (p > 0.05).

CONCLUSIONS

Exposure to cyan light resulted in AL reduction and choroidal thickening in both young adults and children. Further research is needed to determine the application of these results in developing interventions for myopia control.

Myopia Control Effect of Repeated Low-Level Red-Light Therapy Combined with Orthokeratology: A Multicenter Randomized Controlled Trial

PURPOSE

To investigate the efficacy and safety of repeated low-level red-light (RLRL) therapy combined with orthokeratology among children who, despite undergoing orthokeratology, exhibited an axial elongation of at least 0.50 mm over 1 year.

DESIGN

Multicenter, randomized, parallel-group, single-blind clinical trial (ClinicaTrials.gov identifier, NCT04722874).

PARTICIPANTS

Eligible children were 8-13 years of age with a cycloplegic spherical equivalent refraction of -1.00 to -5.00 diopters at the initial orthokeratology fitting examination and had annual axial length (AL) elongation of ≥0.50 mm despite undergoing orthokeratology. Forty-eight children were enrolled from March 2021 through January 2022, and the final follow-up was completed in March 2023.

METHODS

Children were assigned randomly to the RLRL therapy combined with orthokeratology (RCO) group or to the orthokeratology group in a 2:1 ratio. The orthokeratology group wore orthokeratology lenses for at least 8 hours per night, whereas the RCO group received daily RLRL therapy twice daily for 3 minutes in addition to orthokeratology.

MAIN OUTCOME MEASURES

The primary outcome was AL change measured at 12 months relative to baseline. The primary analysis was conducted in children who received the assigned intervention and completed at least 1 follow-up after randomization using the modified intention-to-treat principle.

RESULTS

Forty-seven children (97.9%) were included in the analysis (30 in the RCO group and 17 in the orthokeratology group). The mean axial elongation rate before the trial was 0.60 mm/year and 0.61 mm/year in the RCO and orthokeratology groups, respectively. After 12 months, the adjusted mean AL changes were -0.02 mm (95% confidence interval [CI], -0.08 to +0.03 mm) in the RCO group and 0.27 mm (95% CI, 0.19-0.34 mm) in the orthokeratology group. The adjusted mean difference in AL change was -0.29 mm (95% CI, -0.44 to -0.14 mm) between the groups. The percentage of children achieving an uncorrected visual acuity of more than 20/25 was similar in the RCO (64.3%) and orthokeratology (65.5%) groups (P = 0.937).

CONCLUSIONS

Combining RLRL therapy with orthokeratology may offer a promising approach to optimize axial elongation control among children with myopia. This approach also potentially allows children to achieve satisfactory visual acuity, reducing daytime dependence on corrective eyewear.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

The concept of cone opponency may extend beyond accommodation, to myopiagenesis and emmetropization, for a better peripheral defocus lens

Myopia has ever-rising prevalence in the past few decades globally. Its pathogenesis is still not adequately elucidated especially at the signal transduction level. For the environmental risk factors, there is a large body of fragmented knowledge about the visual inputs for accommodation, myopiagenesis and emmetropization, with the latter two being essentially local processes. The red-green and yellow-blue chromatic pathways, together with the underlying L-M and S-(L+M) cone opponency, seem to be the common denominator amongst them. In this review, experimental and observational evidence are summarized to delineate the interplay of them. This review may establish the pivotal role of longitudinal chromatic aberration (LCA) for a mechanistic approach to future research in myopia control. This review looks into the mechanistic processes underlying myopiagenesis and emmetropization, specifically focusing on chromatic aberration and cone opponency in vision as pivotal components. The roles of longitudinal chromatic aberration (LCA) and cone contrast in myopia onset and development are intriguing. How visual input and chromatic pathways (specifically, red-green and blue-yellow cone opponency) contribute to accommodation that may trigger emmetropization mechanisms, thereby influencing eye growth patterns are explored and discussed. In brief, this manuscript delves into the physiology of visual processing and highlights a foundational aspect of visual science that may account for a "Go" or "Stop" signaling in axial eye growth. It further proposes a metric to gauge myopia-inhibiting optical devices such as the peripheral defocus lenses, for its best iteration. Future research in the above-mentioned areas is warranted.

Animal modeling for myopia

Background

Myopia is one of the most common eye diseases globally, and has become an increasingly serious health concern among adolescents. Understanding the factors contributing to the onset of myopia and the strategies to slow its progression is critical to reducing its prevalence.

Main text

Animal models are key to understanding of the etiology of human diseases. Various experimental animal models have been developed to mimic human myopia, including chickens, rhesus monkeys, marmosets, mice, tree shrews, guinea pigs and zebrafish. Studies using these animal models have provided evidences and perspectives on the regulation of eye growth and refractive development. This review summarizes the characteristics of these models, the induction methods, common indicators of myopia in animal models, and recent findings on the pathogenic mechanism of myopia.

Conclusions

Investigations using experimental animal models have provided valuable information and insights into the pathogenic mechanisms of human myopia and its treatment strategies.

Biomechanical changes occur in myopic choroidal stroma and mirror those in the adjacent sclera

Retina-derived growth signals relayed from the choroid to the sclera cause remodeling of the extracellular scleral matrix, resulting in myopic ocular elongation. However, to the best of our knowledge, no studies have assessed changes in choroidal stromal biomechanical properties during myopia progression. Here we utilized 7 µm-resolution scanning acoustic microscopy (SAM) to assess biomechanical properties (bulk modulus (K) and mass density (rho)) of choroidal stroma from guinea pig eyes with form-deprivation (FD) induced myopia. The choroidal stroma had considerable intrinsic strength arising from its biomechanical properties and these were differentially affected by myopia in central and peripheral regions. Choroidal stromal biomechanical values were also highly correlated with those in adjacent scleral regions, and the choroidal stromal-scleral association was stronger in myopic eyes. Biomechanical changes observed in the choroidal stroma of myopic eyes were mirrored to those observed in the adjacent sclera. These findings suggest that choroidal stromal remodeling may accompany myopia and open the door to the source of the signals that cause scleral remodeling in myopia.

Choroid vascular index in myopic patients - A mini review

Myopia has become a globally prevalent ocular disease. The choroid plays a vital role in myopia, and its changes tend to occur earlier than those of the retina and long-term variations in eye growth. Abnormal axial growth is an intrinsic characteristic of myopia, accompanied by ocular biomechanical changes that result in chorioretinal atrophy, thinning, and other complications particularly in the choroidal vasculature. Recent advancements in imaging technologies have provided deeper insights into these changes. This article explores key findings related to the choroid vascular index in myopia patients.

Techniques for imaging the choroid and choroidal blood flow in vivo

The choroid, which is a highly vascularized layer between the retina and sclera, is essential for supplying oxygen and nutrients to the outer retina. Choroidal vascular dysfunction has been implicated in numerous ocular diseases, including age-related macular degeneration, central serous chorioretinopathy, polypoidal choroidal vasculopathy, and myopia. Traditionally, the in vivo assessment of choroidal blood flow relies on techniques such as laser Doppler flowmetry, laser speckle flowgraphy, pneumotonometry, laser interferometry, and ultrasonic color Doppler imaging. While the aforementioned methods have provided valuable insights into choroidal blood flow regulation, their clinical applications have been limited. Recent advancements in optical coherence tomography and optical coherence tomography angiography have expanded our understanding of the choroid, allowing detailed visualization of the larger choroidal vessels and choriocapillaris, respectively. This review provides an overview of the available techniques that can investigate the choroid and its blood flow in vivo. Future research should combine these techniques to comprehensively image the entire choroidal microcirculation and develop robust methods to quantify choroidal blood flow. The potential findings will provide a better picture of choroidal hemodynamics and its effect on ocular health and disease.

Short-Term Effect of Stimulating the Pterygopalatine Ganglion Via Electroacupuncture on Choroidal Structure in Human Subjects

Purpose

Choroidal dysfunction is implicated in various ocular pathologies. The parasympathetic pterygopalatine ganglion (PPG) innervates orbital vessels supplying the choroid. While PPG stimulation has been shown to dilate cerebral blood flow, its effects on the choroid, particularly in human subjects, require further elucidation. This study aimed to investigate the short-term influence of PPG stimulation via electroacupuncture on choroidal structure.

Methods

In this crossover study, 22 healthy adults received PPG electrical stimulation and sham stimulation for one session each on two separate days in a randomized order. Measurements including choroidal thickness (ChT), choroidal vascularity index (ChVI), central subfield thickness, axial length, anterior chamber depth, and lens thickness were recorded before and at intervals (0, 15, 30, 45, and 60 minutes) postintervention.

Results

The ChT on the side receiving PPG stimulation demonstrated a sustained increase, peaking at 15 minutes poststimulation (17.2 µm, P < 0.001) and persisting for up to 60 minutes. Conversely, the ChVI exhibited a more immediate response, with a peak increase immediately poststimulation (3.8%, P = 0.003), followed by a gradual return to baseline. ChT and ChVI in the contralateral eye showed a nonsignificant trend to decrease. Additionally, a notable reduction in ipsilateral axial length was observed at specific time points poststimulation.

Conclusions

PPG activation via electroacupuncture elicited a short-term increase in ChT and ChVI in the ipsilateral eye compared to sham stimulation, with ChT increases trailing those of ChVI but displaying greater persistence.

Translational Relevance

Electrical stimulation of the PPG can produce a short-term increase in ipsilateral ChT and ChVI.

Melanopsin in the human and chicken choroid

The choroid embedded in between retina and sclera is essential for retinal photoreceptor nourishment, but is also a source of growth factors in the process of emmetropization that converts retinal visual signals into scleral growth signals. Still, the exact control mechanisms behind those functions are enigmatic while circadian rhythms are involved. These rhythms are attributed to daylight influences that are melanopsin (OPN4) driven. Recently, OPN4-mRNA has been detected in the choroid, and while its origin is unknown we here seek to identify the underlying structures using morphological methods. Human and chicken choroids were prepared for single- and double-immunohistochemistry of OPN4, vasoactive intestinal peptide (VIP), substance P (SP), CD68, and α-smooth muscle actin (ASMA). For documentation, light-, fluorescence-, and confocal laser scanning microscopy was applied. Retinal controls proved the reliability of the OPN4 antibody in both species. In humans, OPN4 immunoreactivity (OPN4-IR) was detected in nerve fibers of the choroid and adjacent ciliary nerve fibers. OPN4+ choroidal nerve fibers lacked VIP, but were co-localized with SP. OPN4-immunoreactivity was further detected in VIP+/SP + intrinsic choroidal neurons, in a hitherto unclassified CD68-negative choroidal cell population thus not representing macrophages, as well as in a subset of choroidal melanocytes. In chicken, choroidal nerve fibers were OPN4+, and further OPN4-IR was detected in clustered suprachoroidal structures that were not co-localized with ASMA and therefore do not represent non-vascular smooth-muscle cells. In the choroidal stroma, numerous cells displayed OPN4-IR, the majority of which was VIP-, while a few of those co-localized with VIP and were therefore classified as avian intrinsic choroidal neurons. OPN4-immunoreactivity was absent in choroidal blood vessels of both species. In summary, OPN4-IR was detected in both species in nerve fibers and cells, some of which could be identified (ICN, melanocytes in human), while others could not be classified yet. Nevertheless, the OPN4+ structures described here might be involved in developmental, light-, thermally-driven or nociceptive mechanisms, as known from other systems, but with respect to choroidal control this needs to be proven in upcoming studies.

Effect of virtual reality-based visual training for myopia control in children: a randomized controlled trial

BACKGROUND

To assess the efficacy and safety of virtual reality-based visual training (VRVT) in myopia control among children.

METHODS

The randomized, parallel-group, single-blind clinical trial conducted at the Department of Ophthalmology of Shanghai Tenth People's Hospital enrolled 65 low-myopic children (aged 8 to 13 years) with cycloplegic spherical equivalent (SE) between - 0.50 and - 3.00 diopters (D), astigmatism less than - 1.00 D, anisometropia less than 1.50D, and best corrected visual acuity (BCVA) more than 0.0 logarithm (LogMAR) of the minimum angle of resolution. The participants were enrolled in December 2020, and the follow-up of this study concluded on August 2021. Children were assigned randomly to the intervention group (VRVT plus single-vision spectacle [SVS]) and the control group (only SVS without receiving VRVT). The intervention group was administered for 20 min per day with VRVT under parental supervision at home. The primary outcome was changes in axial length (AL) at 3 months. Macular choroidal thickness (mCT) was regarded as a key secondary outcome.

RESULTS

Among 65 participants (mean age: 10.8 years, 52.3% male), 60 children (92.3%) who completed the 3-month intervention and 6-month follow-up were included in the analysis (30 in the intervention group and 30 in the control group). The changes of AL were 0.063 ± 0.060 mm (95% confidence interval [CI], 0.074 to 0.119 mm) in the intervention group and 0.129 ± 0.060 mm (95% CI, 0.107 to 0.152 mm) and in the control group at 3 months (t = - 2.135, P = 0.037), and the mean difference between the two groups was 0.066 mm. The change of mCT were 22.633 ± 36.171 μm (95% CI, 9.127 to 36.140 μm) in the intervention group and - 3.000 ± 31.056 μm (95% CI, - 14.597 to 8.597 μm) in the control group at 3 months (t = 2.945, P = 0.005). VR vertigo was the most common adverse event which was occurred in two children (2/30, 6.67%) in the intervention group.

CONCLUSIONS

VRVT is a promising method for myopia control in children with good user acceptability. Among children aged 8 to 13 years with low-myopia, nightly use of VRVT resulted in slowing myopia progression.

TRIAL REGISTRATION

This protocol was registered with ClinicalTrials.gov (NCT06250920), retrospectively registered on 01 February 2024.

Administration of Nicotine Can Inhibit Myopic Growth in Animal Models

Purpose

While previously investigating the mechanism by which atropine inhibits ocular growth, we observed that stimulation of nicotinic receptors can inhibit experimental myopia. This study expands on that preliminary finding and investigates the safety and efficacy of nicotinic stimulation in the inhibition of ocular growth.

Methods

Nicotine's ability to inhibit form-deprivation myopia (FDM), following intravitreal injection (9 chicks per group) or topical application (6 chicks per group), was investigated over three doses. The ability of nicotine to inhibit lens-induced myopia (LIM) was also tested (in 12 chicks). For ocular safety, following 4 weeks of topical treatment with nicotine (n = 10), pupillary reflex, intraocular pressure, corneal curvature/thickness, lens thickness, retinal health (retinal thickness/cell apoptosis), as well as retinal function (electroretinogram recordings) were assessed. We also examined the effects of nicotine on non-ocular autonomic functions in both chicks (n = 5) and mice (n = 5).

Results

Nicotine was observed to significantly inhibit the development of FDM in chicks when administered as an intravitreal injection (P < 0.05) or topical eye drops (P < 0.05), albeit not in a dose-dependent manner. Nicotine also inhibited LIM (P < 0.05) to a similar degree to that seen for FDM. Although ocular health was (for the most part) unaffected by nicotine, the highest topical dose induced a temporary reduction in cardiorespiratory output (P < 0.05).

Conclusions

Nicotine, administered as an intravitreal injection or topical eye drop, significantly inhibits the development of experimental myopia. Although the anti-myopic effects observed presently are interesting, the well-reported side effects (expanded on presently) and addictive properties of nicotine would preclude its clinical use.

Inner Retinal Microvasculature With Refraction in Juvenile Rhesus Monkeys

Purpose

To characterize inner retinal microvasculature of rhesus monkeys with a range of refractive errors using optical coherence tomography angiography.

Method

Refractive error was induced in right eyes of 18 rhesus monkeys. At 327 to 347 days of age, axial length and spherical equivalent refraction (SER) were measured, and optical coherence tomography and optical coherence tomography angiography scans (Spectralis, Heidelberg) were collected. Magnification-corrected metrics included foveal avascular zone area and perfusion density, fractal dimension, and lacunarity of the superficial vascular complex (SVC) and deep vascular complex (DVC) in the central 1-mm diameter and 1.0- to 1.5-mm, 1.5- to 2.0-mm, and 2.0- to 2.5-mm annuli. Pearson correlations were used to explore relationships.

Results

The mean SER and axial length were 0.78 ± 4.02 D (-7.12 to +7.13 D) and 17.96 ± 1.08 mm (16.41 to 19.93 mm), respectively. The foveal avascular zone area and SVC perfusion density were correlated with retinal thickness for the central 1 mm (P < 0.05). SVC perfusion density of 2.0- to 2.5-mm annulus decreased with increasing axial length (P < 0.001). SVC and DVC fractal dimensions of 2.0- to 2.5-mm were correlated with axial length and SER, and DVC lacunarity of 1.5- to 2.0-mm annulus was correlated with axial length (P < 0.05).

Conclusions

Several inner retinal microvasculature parameters were associated with increasing axial length and SER in juvenile rhesus monkeys. These findings suggest that changes in retinal microvasculature could be indicators of refractive error development.

Translational Relevance

In juvenile rhesus monkeys, increasing myopic refraction and axial length are associated with alterations in the inner retinal microvasculature, which may have implications in myopia-related changes in humans.

Smartwatch Measures of Outdoor Exposure and Myopia in Children

Importance

Time spent outdoors has been proven effective in preventing myopia, but little is known about the association of outdoor exposure patterns with myopia.

Objective

To examine the association of outdoor exposure patterns with myopic shift in children.

Design, Setting, and Participants

This 1-year prospective cohort study from December 2017 to December 2018 was a secondary analysis of a cluster-randomized trial (Shanghai Time Outside to Reduce Myopia [STORM]). STORM was a school-based intervention study, recruiting 16 schools from 8 districts in Shanghai, from October 2016 to December 2018. Children without myopia at baseline who consistently wore a smartwatch for a minimum of 6 hours daily, sustained for at least 90 days, and who had complete information were included. Data analysis was performed from December 2017 to December 2018.

Exposures

The outdoor exposure pattern was defined as the episode of time outdoors and instant sunlight intensity over a continuous period.

Main Outcomes and Measures

Myopic shift was defined as the absolute change in refraction between the initial spherical equivalence and the follow-up spherical equivalence.

Results

This study included 2976 students (mean [SD] age, 7.2 [0.6] years; 1525 girls [51.2%]). The mean (SD) daily time outdoors was 90 (28) minutes, and the mean (SD) sunlight intensity was 2345 (486) lux. Of the 12 outdoor exposure patterns, the major outdoor exposure patterns were time outdoors with at least 15 minutes, accounting for 74.9% of minutes (33 677 584 of 45 016 800 minutes). Only patterns with at least 15 minutes accompanied with no less than 2000 lux were associated with less myopic shift in refraction (for ≥15 minutes and 2000 to 3999 lux, -0.007 diopter [D] [95% CI, -0.011 to -0.002 D]; for ≥15 minutes and ≥4000 lux, -0.006 D [95% CI, -0.010 to -0.002 D]). The isotemporal substitution of patterns with at least 15 minutes and 2000 lux for other outdoor exposure patterns was positively associated with less myopic shift.

Conclusions and Relevance

In this 1-year prospective cohort study of children with smartwatches, continuous outdoor exposure with at least 15 minutes accompanied with no less than 2000 lux sunlight intensity was associated with less myopic shift. These findings suggest that future outdoor interventions should focus not only on the overall time outdoors but also on the effective outdoor exposure patterns, as a means to effectively prevent myopia in children.

Choroidal Vascularity and Axial Length Elongation in Highly Myopic Children: A 2-Year Longitudinal Investigation

Purpose

To examine the influence of subfoveal choroidal thickness (SFCT) and choroidal vascularity index (CVI) on axial length (AL) elongation over a 2-year period in highly myopic children.

Methods

In this is prospective, longitudinal, observational study, 163 participants (74%), who were 8 to 18 years of age with bilateral high myopia (sphere ≤ -6.0 D) and without pathologic myopia, completed follow-up visits over 2 years. All participants underwent baseline and follow-up ocular examinations, including swept-source optical coherence tomography (SS-OCT) and AL measurements. SFCT and CVI were derived from SS-OCT scans using a deep-learning-based program for choroidal structure assessment.

Results

The mean age of the participants at baseline was 15.0 years (±2.3), with males constituting 47% of the cohort. An inverse relationship was observed between AL elongation and increases in baseline age, baseline SFCT, and CVI, as well as a decrease in baseline AL. Adjusting for other factors, every 10-µm increase in SFCT and each 1% increase in CVI were associated with decreases in AL elongation of 0.007 mm (95% confidence interval [CI], -0.013 to -0.002; P = 0.011) and 0.010 mm (95% CI, -0.019 to 0.000; P = 0.050), respectively. The incorporation of SFCT or CVI into predictive models improved discrimination over models using only age, gender, and baseline AL (both P < 0.05, likelihood ratio test).

Conclusions

Our findings suggest a possible association between a thinner choroid and increased AL elongation over 2 years in children with high myopia, after adjusting for potential baseline risk factors such as age, gender, and initial AL.

Factors affecting choroidal circulation parameters in 4-14-year-old Chinese children measured by SS-OCT/OCTA

PURPOSE

To measure the choroidal circulatory parameters Han Chinese children aged 4-14 years from Southwest China, and to explore the relationships between these parameters and age, axial length (AL), and choroidal thickness (ChT).

METHODS

284 eyes from 142 subjects were included in this cross-sectional study. All participants underwent cycloplegic refraction and IOLMaster500 examination. Swept-source optical coherence tomography (SS-OCT) was used to measure submacular choroidal thickness, choroidal vascular volume (CVV), choroidal stromal volume (CSV), choroidal vascularity index (CVI), and CVV/CSV ratio.

RESULTS

In this population, the mean CVV was 2.92 ± 0.55 mm3, CSV was 4.69 ± 0.68 mm3, CVI was 38.22 ± 2.46 %, and CVV/CSV ratio was 62.11 ± 6.44 %. Multivariable regression analyses showed that both CVV and CSV were negatively correlated with AL (both P < 0.001) and positively correlated with ChT (both P < 0.001), while age showed no significant correlation with them (both P > 0.05). However, the correlations between CVI and age were not uniform rectilinear. Among participants aged ≤8 years, CVI showed no correlation with age (P > 0.05), while among those aged >8 years, it was positively correlated with age (P < 0.01). CVV/CSV ratio was positively correlated with ChT and age (both P < 0.01).

CONCLUSION

After the age of 8, age was positively correlated with CVI. ChT was well correlated with CVI. Longer AL and thinner ChT were associated with reduced CVV and CSV, with CVV decreasing more rapidly than CSV.

High correlated color temperature artificial lighting impairs retinal pigment epithelium integrity and chloride ion transport: A potential mechanism for choroidal thinning

Among the environmental factors contributing to myopia, the role of correlated color temperature (CCT) of ambient light emerges as a key element warranting in-depth investigation. The choroid, a highly vascularized and dynamic structure, often undergoes thinning during the progression of myopia, though the precise mechanism remains elusive. The retinal pigment epithelium (RPE), the outermost layer of the retina, plays a pivotal role in regulating the transport of ion and fluid between the subretinal space and the choroid. A hypothesis suggests that variations in choroidal thickness (ChT) may be modulated by transepithelial fluid movement across the RPE. Our experimental results demonstrate that high CCT illumination significantly compromised the integrity of tight junctions in the RPE and disrupted chloride ion transport. This functional impairment of the RPE may lead to a reduction in fluid transfer across the RPE, consequently resulting in choroidal thinning and potentially accelerating axial elongation. Our findings provide support for the crucial role of the RPE in regulating ChT. Furthermore, we emphasize the potential hazards posed by high CCT artificial illumination on the RPE, the choroid, and refractive development, underscoring the importance of developing eye-friendly artificial light sources to aid in the prevention and control of myopia.