Wide-field choroidal thickness and vascularity index in myopes and emmetropes

Macular choroidal thickness in keratoconus

CLINICAL RELEVANCE

Expanding practitioner knowledge regarding potential changes in ocular structure of keratoconic eyes will improve the eye care practice and patient management.

BACKGROUND

This study aimed to compare the difference in choroidal thickness between keratoconus patients and two control groups of myopic-astigmatism and emmetropic subjects.

METHODS

A case-control study was undertaken which included 50 patients with keratoconus, 50 with myopic-astigmatism, 30 with emmetropia aged between 18 and 39 years. Choroidal thickness was measured at three different locations, including the subfoveal, nasal, and temporal (750 micrometres) to the fovea, using a spectral-domain optical coherence tomography with an enhanced depth imaging technique.

RESULTS

The mean spherical equivalents were 0.03 ± 0.05, -3.00 ± 0.2, and -3.00 ± 0.3 dioptre in emmetropic, myopic-astigmatism and keratoconus subjects, respectively. The choroid was significantly thicker in keratoconus patients than in myopic-astigmatism and emmetropic subjects in the subfoveal (396 ± 14, 314 ± 12, and 320 ± 18 μm, respectively, p < 0.001), temporal (405 ± 14, 317 ± 12, and 328 ± 19 μm, respectively, p < 0.001) and nasal (376 ± 14, 285 ± 12, and 311 ± 18 μm, respectively; p < 0.001).

CONCLUSION

Choroidal thickness is increased in keratoconus. The exact mechanism for choroidal thickening in individuals with keratoconus is unknown, but inflammatory responses could be the reason.

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.

Choroidal Perfusion Changes After Vitrectomy for Myopic Traction Maculopathy

BACKGROUND

The choroidal vasculature supplies the outer retina and is altered in many retinal diseases, including myopic traction maculopathy (MTM). Choroid health is typically assessed by measuring the choroidal thickness; however, this method has substantial limitations. The choroidal vascularity index (CVI) was recently introduced to provide quantitative information on the vascular flow in the choroid. This index has been evaluated in a wide range of diseases but has not been extensively used to characterize MTM.

AIM

This study aimed to investigate the CVI across different stages of MTM and the influence of macular surgery on choroidal perfusion markers in different surgically resolved MTM stages.

METHODS

Eighteen healthy myopic eyes in the control group and forty-six MTM eyes in the surgical group were evaluated using enhanced optical coherence tomography (OCT) imaging. Binarized OCT images were processed to obtain the luminal choroidal area (LCA) and stromal choroidal area (SCA), which were used to calculate CVI in the form of a percentage ratio. CVI data were collected at baseline, one and four months postoperatively, and at the final clinical visit. MTM eyes were divided into four stages based on disease severity. The choriocapillaris flow area (CFA) and central subfield thickness (CSFT) were measured along side the CVI.

RESULTS

No significant differences were observed between the two groups at baseline, except for visual acuity (p  < 0.0001). Surgery significantly improved vision at all postoperative time points (p  < 0.0001). At baseline, there were no significant differences in CVI, CFA, or CSFT scores between the control and surgical groups. However, all three measurements were lower at the final visit in the surgical group (p ≤0.0001). No significant differences were found in any of the parameters among the four stages of MTM (p  > 0.05). Ultimately, correlation and multivariate linear regression analyses did not reveal any significant association between CVI and visual acuity.

CONCLUSIONS

This study did not find significant preoperative differences in CVI between healthy myopic eyes and eyes with MTM. However, the postoperative CVI and CFA values were significantly lower than those of the control eyes. Thus, CVI may not be a good biomarker for surgical outcomes, as the correlation between CVI and visual acuity was not statistically significant.The CVI and CFA decreased after surgery, providing evidence of choroidal changes after surgical management.

Variations in choroidal thickness between emmetropic and myopic eyes after caffeine intake

PURPOSE

To investigate the variations in choroidal thinning between emmetropic and myopic subjects after caffeine intake.

METHODS

Forty-five healthy participants (age mean ± standard deviation [SD]: 20.75 ± 1.6 years) recruited in a prospective cross-sectional study. They were divided into three groups, based on refractive error status, emmetropes (spherical equivalent [SE] -0.25 to +0.25D), myopes (SE ≥-0.50D to ˂-6.00D), and high myopes (SE ≥-6.00D). The participants underwent choroidal thickness [ChT] measurements using optical coherence tomography [OCT] (Topcon 3D OCT-1 Maestro System) at baseline, 20, 40, and 60 minutes after consuming 200 mg of caffeine. The measurements of ChT were taken from five different areas horizontally.

RESULTS

Compared to baseline measurement, the ChT significantly decreased after 200 mg caffeine intake in all conditions ( P < 0.001). There was a statistically significant difference in ChT at baseline between the refractive groups ( χ2 (2)=6.548, P = 0.038) as the high myope group showed lesser horizontal ChT within Nasal at (1 mm) area compared to the myope group ( P = 0.032), however, no other significant differences in mean scores of horizontal ChT at baseline were found. The thinning in ChT in the high myope group was lesser compared to both emmetrope and myope groups; however, it was not statistically significant ( P > 0.05).

CONCLUSION

The results of this study suggest that the reduction in ChT due to caffeine consumption is not significantly affected by the refractive status of the eye. Thus, it is safe to hypothesize that the vascular part of the choroid behaves identically to vasoconstrictive in both emmetropic and myopic eyes. The choroidal thinning found in myopic and high myopic eyes and/or the reduced choroidal vascularity index were not apparent in this study. Therefore, further longitudinal studies recruiting greater numbers of participants, including myopes and high myopes, and measuring both vascular and stromal layers to investigate such variations are warranted.

Macular and peripapillary Choroidal Vascularity Index in children with different refractive status

OBJECTIVES

To characterize choroidal vascular changes in children with different refractive status.

METHODS

A study including 5864 children aged 6-9 years was performed to investigate the choroidal vascular index (CVI) in myopic, emmetropic and hyperopic eyes. Each participant had a comprehensive ocular examination with cycloplegic autorefraction performed, axial length (AL) measured and Swept Source-Optical Coherence Tomography (SS-OCT) scans acquired. Choroidal thickness (ChT) was measured by built-in software, and CVI was calculated using a previously validated self-developed algorithm.

RESULTS

The mean ChT and CVI were 275.88 ± 53.34 μm and 34.91 ± 3.83 in the macula region, and 191.96 ± 46.28 μm and 32.35 ± 4.21 in the peripapillary region. CVI was significantly lowest for myopes, followed by emmetropes and hyperopes (P < 0.001). CVI varied between different sectors separated by the Early Treatment of Diabetic Retinopathy Study (ETDRS) grid (P < 0.001). Macular CVI decreased horizontally from nasal to temporal quadrant with lowest in center fovea, and vertically from superior to inferior quadrants. Peripapillary CVI was highest in the nasal and lowest in the inferior sector. Multiple regression showed that spherical equivalent (SE), AL, intraocular pressure (IOP), ChT, age, and gender were significantly related to CVI (P < 0.05).

CONCLUSIONS

In children, the distribution of CVI in the posterior pole is not uniform. A decreased CVI was observed from hyperopia to myopia and was associated with decreased SE, elongated AL, and choroidal thinning. Further study of changes in CVI during myopia onset and progression is required to better understand the role of the choroidal vasculature in myopia development.

Defocus-induced spatial changes in choroidal thickness of chicks observed by wide-field swept-source OCT

Choroid has been claimed to be of importance during ocular development. However, how the choroid responds spatially to different visual cues has not been fully understood. The aim of this study was to investigate defocus-induced spatial changes in choroidal thickness (ChT) in chicks. Eight 10-day-old chicks were fitted monocularly with -10 D or +10 D lenses (day 0), which were removed seven days later (day 7). The ChT was measured on days 0, 7, 14, and 21 using wide-field swept-source optical coherence tomography (SS-OCT) and analyzed with custom-made software. Comparisons of the ChT in the central (1 mm), paracentral (1-3 mm), and peripheral (3-6 mm) ring areas and the ChT in the superior, inferior, nasal, and temporal regions were conducted. Axial lengths and refractions were also evaluated. In the negative lens group, the global ChT of the treated eyes was significantly less than that of the fellow eyes on day 7 (interocular difference: 179.28 ± 25.94 μm, P = 0.001), but thicker on day 21 (interocular difference: 241.80 ± 57.13 μm, P = 0.024). These changes were more pronounced in the central choroid. The superior-temporal choroid changed more during induction but less during recovery. In the positive lens group, the ChT of both eyes increased on day 7 and decreased on day 21, with most changes occurring in the central region, too. The inferior-nasal choroid of the treated eyes changed more during induction but less during recovery. These results provide evidence for regionally asymmetric characteristics of the choroidal response to visual cues and insights into the underlying mechanisms of emmetropization.

Longitudinal Changes in Choroidal Structure Following Repeated Low-Level Red-Light Therapy for Myopia Control: Secondary Analysis of a Randomized Controlled Trial

PURPOSE

Repeated low-level red-light (RLRL) therapy has been confirmed as a novel intervention for myopia control in children. This study aims to investigate longitudinal changes in choroidal structure in myopic children following 12-month RLRL treatment.

MATERIALS AND METHODS

The current study is a secondary analysis from a multicenter, randomized controlled trial (NCT04073238). Choroidal parameters were derived from baseline and follow-up swept-source optical coherence tomography scans taken at 1, 3, 6, and 12 months. These parameters included the luminal area (LA), stromal area (SA), total choroidal area (TCA; a combination of LA and SA), and choroidal vascularity index (CVI; ratio of LA to TCA), which were automatically measured by a validated custom choroidal structure assessment tool.

RESULTS

A total of 143 children (88.3% of all participants) with sufficient image quality were included in the analysis (n=67 in the RLRL and n=76 in the control groups). At the 12-month visit, all choroidal parameters increased in the RLRL group, with changes from baseline of 11.70×10 3  μm 2 (95% CI: 4.14-19.26×10 3  μm 2 ), 3.92×10 3  μm 2 (95% CI: 0.56-7.27×10 3  μm 2 ), 15.61×10 3  μm 2 (95% CI: 5.02-26.20×10 3  μm 2 ), and 0.21% (95% CI: -0.09% to 0.51%) for LA, SA, TCA, and CVI, respectively, whereas these parameters reduced in the control group.

CONCLUSIONS

Following RLRL therapy, the choroidal thickening was found to be accompanied by increases in both the vessel LA and SA, with the increase in LA being greater than that of SA. In the control group, with myopia progression, both the LA and SA decreased over time.

Compartmental analysis of three-dimensional choroidal vascularity and thickness of myopic eyes in young adults using SS-OCTA

Purpose: We aimed to investigate the change of three-dimensional (3D) choroidal thickness (ChT), choroidal vessel volume (CVV), and choroidal vessel index (CVI) in young myopic adults using swept-source optical coherence tomography angiography (SS-OCTA) and compare the difference of these indicators in different quadrants of the macula and optic disc.

Methods: A total of 248 eye samples from 135 participants were used in this cross-sectional study. Each participant underwent detailed history taking and ocular examinations. Based on axial length (AL), patients were divided into the emmetropia (EM) group, mild-myopia (MIM) group, moderate-myopia (MOM) group, and high-myopia (HM) group. 6 mm × 6 mm (1,024 × 1024 B-scans) SS-OCTA scans were performed centered on the fovea and optic disc. 3D ChT, CVV, and CVI were measured based on a built-in deep learning algorithm. Differences in ChT, CVV, and CVI were analyzed in different regions and different myopic groups.

Results: Significant reduction in the global CVV were found in the HM group (1.930 ± 0.865) in comparison with the EM (3.486 ± 0.992), MIM (3.238 ± 1.033), and MOM (2.589 ± 1.083) groups (p < 0.001). The global CVI was also lower in the HM group (0.258 ± 0.061) than in the EM (0.320 ± 0.055), MIM (0.320 ± 0.051), and MOM (0.286 ± 0.066) groups (p < 0.001). The ChT was thinner in eyes with HM (242.753 ± 65.641) than in eyes with EM (377.532 ± 80.593), MIM (348.367 ± 78.191), or MOM (300.197 ± 87.175) (p < 0.001). Compartmental analysis revealed that ChT, CVV, and CVI in the nasal quadrant of the macula and temporal and inferior quadrants of the optic disc were much lower than those in other quadrants (p < 0.05). Correlation analyses found that ChT, CVV, and CVI were negatively correlated with AL and spherical equivalence.

Conclusion: 3D ChT, CVV, and CVI gradually decreased as the degree of myopia increased. The changes were more dramatic on the nasal side of the macula and the temporal and inferior sides of the optic disc. These findings demonstrated the 3D choroidal change and highlighted the papillo-macular bundle as a sensitive region in myopic development.

The status of the choroid in patients with optic disc drusen

PURPOSE

To investigate the subfoveal and peripapillary choroidal thickness (CT) and the choroidal vascularity index (CVI) in patients with optic disc drusen (ODD).

METHODS

This cross-sectional study examined the eyes of 17 patients with ODD and 18 healthy control subjects. The CT values were calculated manually from the images captured by enhanced depth imaging-optical coherence tomography (EDI-OCT). The CVI was defined as the proportion of the vascular area to the total choroidal area at the subfoveal and peripapillary areas after binarization of the EDI-OCT images.

RESULTS

It was found that the mean subfoveal CVI value in the ODD group was significantly lower than that in the control group (p = 0.006). The mean peripapillary CVI values were significantly lower in all of the quadrants in the ODD group when compared with the control group (p = 0.008 for the temporal quadrant, p = 0.014 for the nasal quadrant, p = 0.024 for the superior quadrant, and p = 0.038 for the inferior quadrant). Regarding the CT, there were no significant differences in the subfoveal and peripapillary CT values between the ODD group and the control group (p >  0.05 for all values).

CONCLUSION

The findings of this study indicate ODD to be associated with decreased subfoveal and peripapillary CVI, even though the subfoveal and peripapillary CT values were within the normal range. This result may prove important in relation to identifying a choroidal vascular network that appears to be morphologically normal but microstructurally impaired due to ODD. Further studies are required to verify the significance of CVI in the pathogenesis and complications of ODD.

How does anisometropia affect the choroidal vascularity index?

Purpose:

To investigate the choroidal vascularity index (CVI) and morphological features of the choroid in anisometropic amblyopia.

Methods:

In this prospective cross-sectional study, 39 patients with unilateral anisometropic amblyopic patients and 33 eyes of 33 healthy control participants were involved. These participants were examined in terms of axial length (AL), spherical equivalent (SE), central macular thickness (CMT), choroidal thickness (CT), total choroidal area (TCA), luminal area (LA), stromal area (SA), LA/SA ratio, and CVI. All parameters were compared between amblyopic eyes, healthy fellow eyes, and healthy control eyes. The Shapiro–Wilk tests, Chi-square test, the paired t-test, Wilcoxon signed-rank test, Mann–Whitney U test, Kruskal–Wallis test, and Pearson/Spearman correlation tests were used.

Results:

In the hyperopic patients; SE, subfoveal CT, nasal CT, temporal CT, TCA, LA, SA, and CMT were greater in amblyopic eyes than in healthy fellow eyes and control eyes (P < 0.001, P < 0.001, P < 0.001, P < 0.001, P < 0.001, P < 0.001, and P < 0.001, respectively), and CVI, LA/SA ratio, and AL were smaller in amblyopic eyes than in healthy fellow eyes and control eyes ([P < 0.001, P = 0.006], P < 0.001, and P < 0.001, respectively). In the myopic patients, subfoveal CT, nasal CT, temporal CT, TCA, LA, SA values were statistically smaller in amblyopic eyes than in healthy eyes and control eyes ([P < 0.001, P = 0.002), [P = 0.004, P = 0.012], [P = 0.012, P = 0.032], [P < 0.001, P = 0.013], [P < 0.001, P = 0.024], and [P < 0.001, P = 0.047], respectively). The differences in the AL and choroidal parameters were due to myopia and hyperopia.

Conclusion:

The choroidal structural parameters of the amblyopic eyes were different from that of the healthy eyes.

Retinal and Choroidal Thickness in Myopic Young Adults

The retinal and the choroidal thickness were measured at four locations along the horizontal direction (foveola, one nasal to the fovea and two temporal) in a group of 43 young adults (mean age: 27.1 ± 3.9 years), with ocular refraction ranging from emmetropia to high myopia (0 to −10D). Thickness values were obtained from OCT images centered at the foveal depression. The retinal thickness exhibited a correlation with refraction at all eccentricities but not at the fovea. When different subgroups of refraction were considered, the analysis of such correlations indicated that only the retinal thickness in the group of high myopia (refraction ≤ −6D) was statistically different from the other two groups (emmetropes: [−0.5, 0] D, and myopes: (−6, −0.5) D). No significant differences were found between emmetropic and myopic groups. In contrast to the retina, the choroidal thickness exhibited a significant correlation with refraction at the fovea, although such dependency only stood for high myopes (the choroid of myopes and emmetropes exhibited similar thickness). Correlation with refraction was also found at the nasal location, arising between emmetropic and high myopia groups. Other choroidal locations among groups did not exhibit relationship with the refraction. It is concluded that the differences in the choroid and retina thickness along the horizontal meridian as a function of refraction do not characterize the onset and progression of myopia at early stages, since they only manifest in the group of high myopia.

Quantitative evaluation of retinal and choroidal vascularity and retrobulbar blood flow in patients with myopic anisometropia by CDI and OCTA

AIMS

To investigate the association between the myopic severity and retinal microvascular density, choroidal vascularity and retrobulbar blood flow in adult anisomyopes.

METHODS

This study comprised 90 eyes of 45 myopic anisomyopes who were recruited for Colour Doppler imaging (CDI) and optical coherence tomography angiography (OCTA). The superficial vessel density (SVD), deep vessel density (DVD), choroidal thickness (ChT) and choroidal vascularity, including total choroidal area (TCA), luminal area (LA), stromal area (SA) and Choroidal Vascularity Index (CVI), were measured using OCTA. Moreover, the Pulsatile Index, peak systolic velocity (PSV) and end diastolic velocity (EDV) of posterior ciliary artery (PCA), central retinal artery (CRA) and ophthalmic artery (OA) were quantified by CDI, and all parameters were compared between two eyes and the correlations among parameters were analysed.

RESULTS

The mean difference of spherical equivalent (SE) and axial lengths (AL) between eyes were -6.00±2.94 D and 2.48±1.31 mm, respectively. The SVD, DVD, ChT, TCA, LA, SA and CVI were significantly lower in more myopic eyes compared with the contralateral eyes. In more myopic eyes, CDI parameters of CRA and PSV and EDV of PCA were also significantly lower. After adjusting for age and sex, the binocular asymmetry in LA and ChT was independent risk factor affecting interocular difference in both AL and SE.

CONCLUSION

Retinal microvascular density, choroidal vascularity and retrobulbar blood flow were simultaneously lower in adult myopic anisomyopes with more myopic eyes and disturbed choroid circulation was related to the severity of myopia. Further longitudinal study was helped to identify the effect of choroidal parameters for myopic progression.

Spatiotemporal Dynamics of Covert Attention With Different Degrees of Central Visual Field Defects: An ERP and sLORETA Study

Purpose

The present study aimed to investigate the spatiotemporal dynamics of covert attention by simulating different degrees of central visual field defects in healthy subjects.

Methods

An electroencephalogram (EEG) was recorded while 40 normal-sighted subjects performed a target discrimination task. Target stimuli simulated different defect degrees of the central visual field by artificially central scotomas (5, 10, 20, and 30 degrees of visual angle) masked on the center of black-and-white checkerboards. Event-related potentials (ERPs) and standardized low-resolution brain electromagnetic tomography (sLORETA) based on ERPs were analyzed.

Results

ERP results indicated that during early perceptual processes, compared with 5-degree and 10-degree defects, N1 amplitudes of 20-degree and 30-degree defects decreased, whereas P2 amplitudes significantly reduced in 30-degree defects. During later discrimination and decision processing, N2 amplitudes gradually increased from 5-degree to 30-degree defects, whereas P3 amplitudes gradually decreased. Source localization indicated that 5-degree and 10-degree defects had stronger activations than 20-degree and 30-degree defects from the occipital cortex to the ventral stream and dorsal streams. Especially, 30-degree defects primarily recruited additional activations in the ventrolateral prefrontal cortex and ventral stream and later caused the disconnection of dorsolateral prefrontal-posterior parietal cortices in the dorsal stream.

Conclusions

Different degrees of central visual field defects differed in distinct spatiotemporal characteristics at multiple stages of covert attention, from top-down forward feedback and attentional allocation to executive controls through ventral and dorsal processing streams, suggesting that the combination of ERP and source localization can reveal the spatiotemporal control capacity of the cortex on central visual field defects.

Assessment of Choroidal Vascularity and Choriocapillaris Blood Perfusion After Accommodation in Myopia, Emmetropia, and Hyperopia Groups Among Children

Purpose

To investigate choroidal vascularity (CV) and choriocapillaris blood perfusion before and after accommodation in myopia, emmetropia, and hyperopia groups among children.

Methods

This study included 39 myopic eyes from 22 subjects, 17 emmetropic eyes from 11 subjects, and 18 hyperopic eyes from 10 subjects. All subjects were children. Choroidal thickness (CT) and CV, including total choroidal area (TCA), luminal area (LA), and stromal area (SA) were measured using swept-source optical coherence tomography (SS-OCT). Choriocapillaris luminal area (CLA) was measured using SS-OCT-angiography before and after accommodation (near reading with an additional −3 diopter lens).

Results

For baseline results, except horizontal CV (showing no significant differences between myopia and emmetropia groups), both horizontal and vertical CT and CV were significantly smaller in the myopia group than in the emmetropia or hyperopia groups. In terms of CLA, no significant differences were observed among the myopia, emmetropia, and hyperopia groups. In addition, only myopic eyes showed significant decreases in CT and CV, whereas most CT and CV of emmetropic and hyperopic eyes showed non-significant decreases after accommodation. Furthermore, accommodation induced no significant changes in CLA in the myopia, emmetropia, or hyperopia groups.

Conclusion

Myopia had thinner baseline choroid and lower baseline choroidal blood perfusion. Furthermore, myopic eyes were more prone to choroidal thinning and blood perfusion decreases after accommodation.

Choroidal thickness and choriocapillaris vascular density in myopic anisometropia

BACKGROUND

This study aims to examine interocular differences in the choroidal thickness and vascular density of the choriocapillaris in anisometropic myopes and to further explore the relationship between choroidal blood flow and myopia.

METHODS

The sample comprised 44 participants with anisometropic myopia, aged 9 to 18 years, with normal best-corrected visual acuity. All participants underwent a series of examinations, including spherical equivalent refraction (SER) and axial length (AL), measured by a Lenstar optical biometer and optical coherence tomography angiography (OCTA) scanner. OCT measured the choroidal thickness, vascular density, and flow voids of the choriocapillaris, and a customized algorithm was implemented in MATLAB R2017a with the post-correction of AL. The choroidal thickness was measured at the fovea and 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm nasally, temporally, inferiorly, and superiorly to the fovea. The vascular density and the flow voids of the choriocapillaris were measured at a 0.6-mm-diameter central circle, and the 0.6-2.5 mm diameter circle in the nasal, temporal, inferior, and superior regions. Repeated-measured ANOVAs were used to analyze the interocular differences. Partial correlations with the K value and age adjustments were used to study the relationships between the choroidal thickness, the choriocapillaris vascular density and flow voids, the SER and AL.

RESULTS

The choroidal thickness of the more myopic eyes was significantly thinner than less myopic eyes (P ≤ 0.001), and the flow voids in the more myopic eyes were more than less myopic eyes (P = 0.002). There was no significant difference in the vascular density of the choriocapillaris between the more and less myopic eyes (P = 0.525). However, when anisometropia was more than 1.50 D, the vascular density of choriocapillaris in the more myopic eyes was significantly less than the less myopic eyes (P = 0.026). The interocular difference of the choroidal thickness was significantly correlated with the interocular difference in SER and AL in the center, superior, and inferior regions but not in the nasal or temporal regions. The interocular differences of the vascular density and the flow voids of the choriocapillaris were not correlated with the interocular difference of SER and AL.

CONCLUSIONS

The choroidal thickness is thinner in the more myopic eyes. The flow void is increased, and the vascular density of the choriocapillaris is reduced in the more myopic eyes of children with anisometropia exceeding 1.50 D.

Retinal OFF-Pathway Overstimulation Leads to Greater Accommodation-Induced Choroidal Thinning

Purpose

To examine the interactions between accommodation and overstimulation of the retinal ON- and OFF-pathways, and their association with changes in choroidal thickness (ChT) and vascularity.

Methods

Optical coherence tomography imaging of the choroid of twenty young adults (ages 25 ± 5 years) was performed before and after a series of 30-minute-long viewing tasks, including reading a bright text on dark background (ON-pathway overstimulation) and dark text on bright background (OFF-pathway overstimulation), and a control task of viewing a movie with unbiased ON-/OFF-pathway activation. The viewing tasks were performed with relaxed, and 5 diopter (D) accommodation (induced by soft contact lenses) demands. Both reading texts were matched for the mean luminance (35 cd/m²), luminance contrast (87%), and letter size (approximately 11.8 arc minutes). The change in ChT from baseline associated with contrast polarity and accommodation was examined using linear mixed model analysis.

Results

The subfoveal ChT decreased significantly by −7 ± 1 µm with 5 D accommodation compared with relaxed accommodation (−3 ± 1 µm; P < 0.001), and by −9 ± 1 µm with OFF-pathway compared with ON-pathway overstimulation (−4 ± 1 µm; P = 0.002) and the control condition (−2 ± 1 µm; P < 0.001). Overstimulation of the OFF-pathway, but not the ON-pathway, resulted in a significantly greater choroidal thinning compared with the control condition, both at relaxed (−7 ± 1 µm; P = 0.003) and 5 D (−11 ± 1 µm; P = 0.005) accommodation levels. Similar changes were also observed for macular total, stromal, and luminal ChT.

Conclusions

Retinal OFF-pathway stimulation enhanced the choroidal thinning associated with accommodation, thereby providing a potential mechanism that involves accommodation and the retinal OFF-signaling pathway, linking near work and myopia.