Lowering Intraocular Pressure: A Potential Approach for Controlling High Myopia Progression

Association of physical activity, sedentary behaviour, sleep and myopia in children and adolescents: a systematic review and dose-response meta-analysis

PURPOSE

This study aimed to systematically evaluate the dose-response relationships between physical activity (PA), sedentary behavior(SB) (including near work [NW] and screen time [ST]), sleep duration (SD), and myopia risk among children and adolescents.

DESIGN

Systematic review and dose-response meta-analysis.

METHODS

We systematically searched PubMed, EMBASE, Cochrane Library, and Web of Science up to November 19, 2024. Methodological quality was assessed using Joanna Briggs Institute (JBI) and ROBINS-I tools. Random-effects meta-analyses were used to estimate categorical and continuous dose-response relationships. Subgroup analyses and sensitivity analyses were performed to explore heterogeneity sources and test robustness.

RESULTS

A total of 45 observational studies (766,848 participants aged 5-19 years) were included. Categorical analyses showed that, compared with the lowest exposure categories, higher PA levels (highest: OR = 0.77, 95% CI: 0.63-0.96; intermediate: OR = 0.76, 95% CI: 0.63-0.93) and longer SD (highest: OR = 0.67, 95% CI: 0.48-0.92; intermediate: OR = 0.82, 95% CI: 0.73-0.92) significantly reduced myopia risk. Conversely, higher levels of NW (highest: OR = 1.71, 95% CI: 1.28-2.27; intermediate: OR = 1.34, 95% CI: 1.19-1.50) and ST (highest: OR = 1.59, 95% CI: 1.14-2.22; intermediate: OR = 1.29, 95% CI: 1.12-1.49) were associated with significantly increased risk. In the continuous dose-response meta-analysis, a linear association was observed between PA, ST, and myopia. Each additional hour of PA per day reduced the risk of myopia by 12%, while each additional hour of ST increased the risk by 31%. Nonlinear associations were found between NW, SD, and myopia. Among children and adolescents, 1.5 and 2.5 h/day of NW increased the risk of myopia by 25% and 29%, respectively. Although longer SD was associated with a reduced risk of myopia, this effect did not reach statistical significance at any exposure level.Subgroup analyses revealed that protective effects of PA were more evident in low- and middle-income countries, smaller sample sizes, and cross-sectional studies, while increased risks related to ST and NW were stronger in low-income settings. No subgroup significantly modified the association between SD and myopia risk.

CONCLUSION

Increasing PA, while limiting ST and NW, effectively reduces the risk of myopia among children and adolescents. The association between sleep duration and myopia remains inconclusive, warranting further investigation.

Progress in clinical characteristics of high myopia with primary open-angle glaucoma

High myopia (HM) is a significant risk factor for the occurrence and progression of primary open-angle glaucoma (POAG). Identification with POAG in the HM population is an emergent challenge. Patients with HM have a significantly higher probability of complicating POAG than those without HM. When HM is associated with POAG, the changes to the fundus caused by both of them are confused with each other, making the diagnosis of early glaucoma difficult. This article reviews available researches on HM with POAG, summarizing the characteristics of the fundus structure such as epidemiology, intraocular pressure, optic disc, ganglion cell layer, retinal nerve fiber layer, vascular density, and visual field.

Novel compound heterozygous variants in LTBP2 associated with relative anterior microphthalmos

PURPOSE

Relative anterior microphthalmos (RAM) is a rare congenital defect associated with severe vision impairment that is primarily caused by genetic alterations. The purpose of this study was to identify the causative genetic variants in two Chinese families with RAM with an autosomal recessive inheritance pattern.

METHODS

DNA samples were obtained from two probands and their family members. Targeted next-generation sequencing (NGS) was used to screen 425 genes associated with inherited eye diseases to identify possible disease-causing variants in the two patients. Sanger sequencing was subsequently used to validate the results in both families.

RESULTS

The targeted NGS panel identified potentially causative novel variants of the latent transforming growth factor beta binding protein 2 (LTBP2) gene in the two RAM families: a missense variant (c.2771C > T; p.Ala924Val) and an intronic variant (c.4582 + 9A > G) in Family A and a different missense variant (c.5239C > A; p.Arg1747Ser) and a synonymous variant (c.951G > A; p.Pro317Pro) in Family B. These four novel variants all cosegregated with the disease phenotype.

CONCLUSION

To our knowledge, this is the first study to report novel LTBP2 gene variants related to RAM. Considering the importance of LTBP2 in ocular development, we provide initial insights into the potential pathogenic mechanisms of LTBP2 in RAM.

Axial elongation in nonpathologic high myopia: Ocular structural changes and glaucoma diagnostic challenges

Axial elongation continues in highly myopic adult eyes, even in the absence of pathologic changes such as posterior staphyloma or chorioretinal atrophy. This ongoing axial elongation leads to structural changes in the macular and peripapillary regions, including chorioretinal thinning, reduced vascular perfusion and optic disc tilting and rotation, among others. These alterations can affect the acquisition and interpretation of optical coherence tomography, optical coherence tomography angiography and fundus photographs, potentially introducing artifacts and diminishing the accuracy of glaucoma diagnosis in highly myopic eyes. In this review, we compared the progression patterns of axial elongation across populations with varying demographic characteristics, genetic and environmental backgrounds and ocular features. We also discussed the implications of axial elongation-induced ocular structural changes for diagnosing glaucoma in nonpathologic high myopia. Finally, we highlighted the prospects for enhancing the diagnostic efficacy of glaucoma in nonpathologic highly myopic populations.

Progression Patterns and Risk Factors of Axial Elongation in Young Adults With Nonpathologic High Myopia: Three-Year Large Longitudinal Cohort Follow-Up

PURPOSE

To investigate the progression patterns and risk factors of axial elongation in young adults with nonpathologic high myopia.

DESIGN

Prospective, clinical observational cohort study with 2- to 4-year follow-up.

METHODS

A total of 1043 eyes of 563 participants (3515 medical records) aged 18 to 50 years with nonpathologic high myopia (axial length [AL] ≥ 26 mm; myopic maculopathy < diffuse chorioretinal atrophy; without posterior staphyloma) were included from 1546 participants (6318 medical records). Annual axial elongation was calculated via linear mixed-effect models. The associated risk factors of axial elongation were determined by ordinal logistic regression analysis, with generalized estimate equations for eliminating an interocular correlation bias.

RESULTS

Based on 5359 times of AL measurements, the annual axial elongation of participants (mean [SD] age 31.39 [9.22] years) was 0.03 mm/year (95% confidence interval [CI], 0.03-0.04; P < .001) during a 30.23 (6.06) months' follow-up. Severe (>0.1 mm/year), moderate (0.05-0.09 mm/year), mild (0-0.049 mm/year), and nil (≤0 mm/year) elongation was observed in 122 (11.7%), 211 (20.2%), 417 (40.0%), and 293 (28.1%) eyes. The following risk factors were significantly associated with axial elongation: baseline AL ≥ 28 mm (odds ratio [OR], 4.23; 95% CI, 2.95-6.06; P < .001); age < 40 years (OR, 1.64; 95% CI, 1.18-2.28; P = .003); axial asymmetry (OR, 2.04; 95% CI, 1.26-3.29; P = .003), and women (OR, 1.52; 95% CI, 1.13-2.2.05; P = .006). Using antiglaucoma medications was a protective factor (OR, 0.46; 95% CI, 0.27-0.79; P = .005), which slowed 75% of axial elongation from 0.04 (0.06) to 0.01 (0.06) mm/y (P < .001).

CONCLUSIONS

Axial elongation continued in young adults with nonpathologic myopia. Risk factors included longer baseline AL and axial asymmetry, younger age, and woman. Topical use of antiglaucoma medications may be useful to reduce ongoing axial elongation.

The lack of causal link between myopia and intraocular pressure: Insights from cross-sectional analysis and Mendelian randomization study

OBJECTIVE

This study aimed to explore the potential causal relationship between intraocular pressure (IOP) and myopia.

METHODS

The study included 3,459 patients who underwent corneal refractive surgery at our institution between 2021 and 2023. Preoperative data on IOP, spherical equivalent (SE), axial length (AL), and corneal thickness (CCT) were collected. The association between IOP and myopia was investigated through rank correlation analysis, and causal inference was examined using Mendelian randomization (MR) methods, including MR-Egger, weighted median, mode-based estimation, simple mode, and inverse variance weighted (IVW) approaches. Utilizing summary statistics from genome-wide association studies (GWAS), IOP was considered as the exposure, with myopia as the outcome variable. IVW method was employed for the primary analysis, supplemented by sensitivity analyses.

RESULTS

Cross-sectional analysis revealed a non-significant association between corrected IOP (cIOP) and myopia (r = -0.019, P = 0.12). MR analysis indicated a non-significant genetic causal relationship between cIOP and myopia under the IVW method (OR = 1.001; 95 % CI [0.999-1.003], P = 0.22), a finding corroborated in replication samples (OR = 0.98; 95 % CI [0.96-1.00], P = 0.099).

CONCLUSION

This study did not find a direct causal link between IOP and the development of myopia. These findings challenge the traditional role attributed to IOP in the progression of myopia and highlight the complex, multifactorial process of myopia development. This provides a new perspective on understanding the intricate mechanisms behind myopia progression.

Intraocular pressure and its association with ocular biometrics in Iranian children

PURPOSE

To determine the mean value and normative distribution of intraocular pressure (IOP) in children and their association with demographic and ocular biometrics.

METHODS

Cluster sampling was done to select the students in urban areas of Shahroud, northeast Iran, while all students living in rural areas were selected. IOP was measured in mmHg using a non-contact tonometer, along with corneal and retinal imaging and ocular biometric measurement.

RESULTS

After applying the exclusion criteria, 9154 eyes of 4580 students were analyzed, of whom 2377 (51.9 %) were boys. The mean age of the participants was 12.35±1.73 years (range: 9-15 years). The mean IOP was 15.58±2.83 (15.47-15.69) in total, 15.31±2.77 (15.17-15.46) in boys, and 15.88±2.86 (15.73-16.03) in girls (p < 0.001). The mean IOP was 15.07 and 15.49 in students aged 9 and 15 years, respectively. The mean IOP was 15.7 ± 2.64 (15.58-15.81) in urban and 14.52±4.05 (14.27-14.77) in rural students (p < 0.001). In the multiple generalized estimating equation model, IOP had a positive association with female sex (β=0.84, P < 0.001), systolic blood pressure (β=0.02, P < 0.001), cup volume (β=0.99, P < 0.001), corneal thickness (β=0.04, P < 0.001) and anterior chamber volume (β=0.007, P < 0.001) and a negative association with living in the rural area (β=-0.65, P < 0.001), rim area (β=-0.39, P < 0.001), and corneal diameter (β=-0.18, P = 0.045). Furthermore, individuals with myopia exhibited a significantly higher IOP (β=0.35, P < 0.001) compared to those with emmetropia.

CONCLUSION

This study showed the normative distribution of IOP and its associated factors in children. The results can be used in diagnosis and management of glaucoma.

The Mirror Theory: Parallels between Open Angle and Angle Closure Glaucoma

Glaucoma is a widespread ophthalmological disease, with a high impact and frequent visual morbidity. While the physiopathology of the two types of primary glaucoma (open angle and angle closure) has been studied, there seems to be little relationship between the two. In this study, we gather clinical and preclinical data to support the idea that the two primary glaucomas are "mirrored" in terms of morphological parameters and disease physiopathology. In short, primary angle closure glaucoma (PACG) is associated with hyperopia and low axial length, and primary open angle glaucoma (POAG) is associated with myopia and high axial length. Moreover, in PACG and in primary angle closure or primary angle closure suspect cases, while there is extensive iridotrabecular contact, the intraocular pressure (IOP) is still maintained in the lower half of the normal range throughout the evolution of the disease, which suggests a baseline trabecular hyperfiltration in PACG. In the opposite case, myopic eyes with open angles and a higher risk of developing POAG often have a baseline IOP in the upper half of the normal range, suggesting a baseline trabecular hypofiltration. As we explore clinical, genetic and animal model data regarding these opposing aspects, we hypothesize the existence of a mirroring relationship between PACG and POAG. Defining the relationship between the two potentially blinding diseases, with a high prevalence worldwide, may aid in understanding the mechanisms better and refining diagnosis and treatment. Thus, our theory has been named the Mirror Theory of Primary Glaucomas.

Progression to bilaterality in unilateral primary congenital glaucoma

PURPOSE

To evaluate the incidence of rise in intraocular pressure (IOP) in fellow eyes of patients with unilateral primary congenital glaucoma (PCG) and to identify risk factors for IOP increase over long-term follow-up.

METHODS

The medical records of unilateral PCG patients who had completed at least 5 years of follow-up were reviewed retrospectively. The incidence of developing ocular hypertension / glaucoma in fellow eyes was analyzed. Fellow eye progressors were those which showed an increase in optic nerve cupping by at least 0.2 since the first presentation or had IOP of >21 mm Hg on two occasions. The risk factors for progression that were analyzed included IOP, visual acuity, axial length, central corneal thickness (CCT), corneal diameters (CD), presence or absence of angle dysgenesis on high-resolution anterior segment optical coherence tomography (AS-OCT), and morphology of aqueous outflow pathways.

RESULTS

After a median follow-up of 8.2 years (range, 5-25.5) progression to bilateral disease was found in 17 of 54 patients (32%), of whom 8 (15%) developed ocular hypertension and 9 (17%) developed glaucoma in the fellow eye. Among the unaffected fellow eyes, those with a larger CD (>12 mm), measured after at least 5 years' follow-up, were ten times more likely to progress (P = 0.01; OR = 9.5 [95% CI, 1.7-54.3]). The presence of a patent supraciliary channel was significantly more frequently associated in fellow eyes compared with affected eyes on AS-OCT (OR = 1.4 [95% CI, 0.46-4.68]).

CONCLUSIONS

One-third of unaffected fellow eyes of unilateral PCG eventually progress over time, most often after 5 years. Larger CD at follow-up in the fellow eye is strongly predictive for progression.

Intraocular pressure reduction and progression of highly myopic glaucoma: a 12-year follow-up cohort study

AIMS

To investigate any association between intraocular pressure (IOP) reduction amount and open-angle glaucoma (OAG) progression in highly myopic eyes and to determine the associated risk factors.

METHODS

One hundred and thirty-one (131) eyes of 131 patients with highly myopic OAG, all of whom had received topical medications and been followed for 5 years or longer, were enrolled. Based on the IOP reduction percentage, patients were categorised into tertile groups, and subsequently, the upper-tertile and lower-tertile groups were compared for the cumulative probability of glaucoma progression. Kaplan-Meier survival analysis and log-rank testing were applied in the comparison, and multivariate analysis with Cox's proportional hazard model, additionally, was performed to identify progression risk factors.

RESULTS

Throughout the average 11.6±4.4 year follow-up on the 131 eyes (mean age, 41.2 years at initial visit; baseline IOP, 16.4 mm Hg), 72 eyes (55.0%) showed glaucoma progression. The upper-tertile group (IOP reduction percentage>23.7%) showed a high cumulative probability of non-progression relative to the lower-tertile group (IOP reduction percentage<11.0%; p=0.034), according to the Kaplan-Meier analysis. Presence of disc haemorrhage (DH; HR=2.189; p=0.032) was determined by the multivariate Cox's proportional hazard model to be significantly associated with glaucoma progression. For progressors, the average rate of retinal nerve fibre layer thickness thinning was -0.88±0.74 µm/year, while the MD change was -0.42±0.36 dB/year.

CONCLUSIONS

Glaucoma progression is associated with amount of IOP reduction by topical medications in highly myopic eyes, and DH occurrence is a glaucoma progression risk factor.

Seasonal variations in anterior segment angle parameters in myopes and emmetropes

CLINICAL RELEVANCE

Seasonal variations are known to occur in a range of ocular parameters and in conditions including refractive error and glaucoma. It is of clinical importance to know if seasonal changes also occur in anterior segment angle parameters, given that they can influence these conditions.

BACKGROUND

The study aimed to examine the seasonal variations in anterior segment angle parameters in healthy young adults.

METHODS

Twenty-three emmetropic participants with a mean age of 26.17 ± 4.43 years and 22 myopic participants with a mean age of 27.27 ± 4.47 years completed four seasons of data collection. Anterior segment angle parameters were measured using swept-source anterior segment optical coherence tomography. Intraocular pressure (IOP) and objective refraction were also measured. Repeated-measures analysis of variance was used to determine the effect of season and refractive error on the various ocular parameters.

RESULTS

A significant main effect of season was found for the majority of anterior segment angle parameters, including the angle opening distance at 500 and 750 µm from the scleral spur (p = 0.02, p = 0.006, respectively), angle recess area at 500 and 750 µm from the scleral spur (both p = 0.002), and trabecular iris space area at 500 and 750 µm from the scleral (p = 0.02, p = 0.008, respectively). However, measures of anterior chamber depth and trabecular iris angle did not exhibit statistically significant seasonal variations (all p > 0.05). A significant main effect of season was also found for the changes in IOP (p = 0.004) and objective refraction (p < 0.001). There was no season by refractive group interaction for any anterior segment angle parameter or IOP (all p > 0.05).

CONCLUSION

There is a small but significant seasonal changes in the anterior segment angle parameters, refractive error, and IOP in healthy young adult males, in which the anterior segment angle dimensions are narrower, the IOP is higher, and the refraction is more myopic during winter.

Factors associated with pathologic myopia onset and progression: A systematic review and meta-analysis

PURPOSE

To synthesise evidence across studies on factors associated with pathologic myopia (PM) onset and progression based on the META-analysis for Pathologic Myopia (META-PM) classification framework.

METHODS

Findings from six longitudinal studies (5-18 years) were narratively synthesised and meta-analysed, using odds ratio (OR) as the common measure of association. All studies adjusted for baseline myopia, age and sex at a minimum. The quality of evidence was rated using the Grades of Recommendation, Assessment, Development and Evaluation framework.

RESULTS

Five out of six studies were conducted in Asia. There was inconclusive evidence of an independent effect (or lack thereof) of ethnicity and sex on PM onset/progression. The odds of PM onset increased with greater axial length (pooled OR: 2.03; 95% CI: 1.71-2.40; p < 0.001), older age (pooled OR: 1.07; 1.05-1.09; p < 0.001) and more negative spherical equivalent refraction, SER (OR: 0.77; 0.68-0.87; p < 0.001), all of which were supported by an acceptable level of evidence. Fundus tessellation was found to independently increase the odds of PM onset in a population-based study (OR: 3.02; 2.58-3.53; p < 0.001), although this was only supported by weak evidence. There was acceptable evidence that greater axial length (pooled OR: 1.23; 1.09-1.39; p < 0.001), more negative SER (pooled OR: 0.87; 0.83-0.92; p < 0.001) and higher education level (pooled OR: 3.17; 1.36-7.35; p < 0.01) increased the odds of PM progression. Other baseline factors found to be associated with PM progression but currently supported by weak evidence included age (pooled OR: 1.01), severity of myopic maculopathy (OR: 3.61), intraocular pressure (OR: 1.62) and hypertension (OR: 0.21).

CONCLUSIONS

Most PM risk/prognostic factors are not supported by an adequate evidence base at present (an indication that PM remains understudied). Current factors for which an acceptable level of evidence exists (limited in number) are unmodifiable in adults and lack personalised information. More longitudinal studies focusing on uncovering modifiable factors and imaging biomarkers are warranted.

Effect of intraocular pressure reduction on progressive high myopia (PHM study): study protocol of a randomised controlled trial

BACKGROUND

In adult patients with high myopia (HM), progressive axial elongation poses a significant risk for the development of subsequent ocular complications that may lead to visual impairment. Effective strategies to reduce or prevent further axial elongation in highly myopic adult patients have not been available so far. Recent studies suggested that medically lowering intraocular pressure (IOP) may reduce axial elongation.

OBJECTIVE

This clinical randomised controlled trial (RCT) aims to evaluate the efficacy of medical IOP reduction in adult patients with progressive HM (PHM).

TRIAL DESIGN

Single-centre, open-label, prospective RCT.

METHODS

This RCT will recruit 152 participants with PHM at the Zhongshan Ophthalmic Center (ZOC). Randomised in a ratio of 1:1, participants will receive IOP-lowering eyedrops (intervention group) or will be followed without treatment (control group) for 12 months. Follow-up visits will be conducted at 1, 6 and 12 months after baseline. Only one eye per eligible participant will be included for analysis. The primary outcome is the change in axial length (AL) within the study period of 12 months. Secondary outcomes include the incidence and progression of visual field (VF) defects, changes in optic disc morphology and incidence and progression of myopic maculopathy. Difference in AL changes between the two groups will be analysed using linear regression analysis. For the secondary outcomes, a multifactor Poisson regression within a generalised linear model will be used to estimate the relative risk of progression in VF defects and myopic maculopathy, and the rate of thinning in retinal nerve fibre layer and ganglion cell-inner plexiform will be assessed through Kaplan-Meier curves and log-rank tests.

ETHICS AND DISSEMINATION

Full ethics approval for this trial has been obtained from the Ethics Committee of ZOC, Sun Yat-sen University, China (ID: 2023KYPJ110). Results of this trial will be disseminated through peer-reviewed journals and conference presentations.

TRIAL REGISTRATION NUMBER

NCT05850936.

Myopia prevalence and ocular biometry in children and adolescents at different altitudes: a cross-sectional study in Chongqing and Tibet, China

OBJECTIVE

To investigate the differences in myopia prevalence and ocular biometry in children and adolescents in Chongqing and Tibet, China.

DESIGN

Cross-sectional study.

SETTING

The study included children and adolescents aged 6-18 years in Chongqing, a low-altitude region, and in Qamdo, a high-altitude region of Tibet.

PARTICIPANTS

A total of 448 participants in Qamdo, Tibet, and 748 participants in Chongqing were enrolled in this study.

METHODS

All participants underwent uncorrected visual acuity assessment, non-cycloplegic refraction, axial length (AL) measurement, intraocular pressure (IOP) measurement and corneal tomography. And the participants were grouped according to age (6-8, 9-11, 12-14 and 15-18 years group), and altitude of location (primary school students: group A (average altitude: 325 m), group B (average altitude: 2300 m), group C (average altitude: 3250 and 3170 m) and group D (average altitude: 3870 m)).

RESULTS

There was no statistical difference in mean age (12.09±3.15 vs 12.2±3.10, p=0.549) and sex distribution (males, 50.4% vs 47.6%, p=0.339) between the two groups. The Tibet group presented greater spherical equivalent (SE, -0.63 (-2.00, 0.13) vs -0.88 (-2.88, -0.13), p<0.001), shorter AL (23.45±1.02 vs 23.92±1.19, p<0.001), lower prevalence of myopia (39.7% vs 47.6%, p=0.008) and flatter mean curvature power of the cornea (Km, 43.06±1.4 vs 43.26±1.36, p=0.014) than the Chongqing group. Further analysis based on age subgroups revealed that the Tibet group had a lower prevalence of myopia and higher SE in the 12-14, and 15-18 years old groups, shorter AL in the 9-11, 12-14 and 15-18 years old groups, and lower AL to corneal radius of curvature ratio (AL/CR) in all age subgroups compared with the Chongqing group, while Km was similar between the two groups in each age subgroup. Simple linear regression analysis showed that SE decreased with age in both the Tibet and Chongqing groups, with the Tibet group exhibiting a slower rate of decrease (p<0.001). AL and AL/CR increased with age in both the Tibet and Chongqing groups, but the rate of increase was slower in the Tibet group (p<0.001 of both). Multiple linear regression analysis revealed that AL had the greatest effect on SE in both groups, followed by Km. In addition, the children and adolescents in Tibet presented thinner corneal thickness (CCT, p<0.001), smaller white to white distance (WTW, p<0.001), lower IOP (p<0.001) and deeper anterior chamber depth (ACD, p=0.015) than in Chongqing. Comparison of altitude subgroups showed that the prevalence of myopia (p=0.002), SE (p=0.031), AL (p=0.001) and AL/CR (p<0.001) of children at different altitudes was statistically different but the Km (p=0.189) were similar. The highest altitude, Tengchen County, exhibited the lowest prevalence of myopia and greatest SE among children, and the mean AL also decreased with increasing altitude.

CONCLUSIONS

Myopia prevalence in Tibet was comparable with that in Chongqing for students aged 6-8 and 9-11 years but was lower and myopia progressed more slowly for students aged 12-14 and 15-18 years than in Chongqing, and AL was the main contributor for this difference, which may be related to higher ultraviolet radiation exposure and lower IOP in children and adolescents at high altitude in Tibet. Differences in AL and AL/CR between Tibet and Chongqing children and adolescents manifested earlier than in SE, underscoring the importance of AL measurement in myopia screening.

Brimonidine as a possible treatment for myopia

BACKGROUND

Myopia is becoming a huge burden on the world's public health systems. The purpose of this study was to explore the effect of brimonidine in the treatment of form-deprivation myopia (FDM) and the relationship between intraocular pressure (IOP) and myopia development.

METHODS

Monocular form deprivation myopia (FDM) was induced in three-week-old pigmented male guinea pigs. They were treated with 3 different methods of brimonidine administration (eye drops, and subconjunctival or intravitreal injections). Four different concentrations of brimonidine were tested for each method (2µg/µL, 4µg/µL, 20µg/µL, and 40µg/µL). All treatments continued for a period of 21 days. Tonometry, retinoscopy, and A-scan ultrasonography were used to monitor intraocular pressure, refractive error and axial length (AL), respectively.

RESULTS

Treatment with subconjunctival brimonidine at 40µg/µL, and intravitreal brimonidine at 2µg/µL and 4µg/µL, inhibited the development of FDM. The myopic refraction, excessive axial length, and elevation of IOP were significantly decreased. Brimonidine in eye drops was ineffective.

CONCLUSION

Brimonidine at appropriate doses significantly reduced the development of FD myopia in guinea pigs. The IOP may change with FD myopia.

Higher intraocular pressure is associated with slower axial growth in children with non-pathological high myopia

OBJECTIVES

To investigate the association between intraocular pressure (IOP) and axial elongation rate in highly myopic children from the ZOC-BHVI High Myopia Cohort Study.

METHODS

162 eyes of 81 healthy children (baseline spherical equivalent: -6.25 D to -15.50 D) aged 7-12 years with non-pathological high myopia were studied over five biennial visits. The mean (SD) follow-up duration was 5.2 (3.3) years. A linear mixed-effects model (LMM) was used to assess the association between IOP (at time point t-1) and axial elongation rate (annual rate of change in AL from t-1 to t), controlling for a pre-defined set of covariates including sex, age, central corneal thickness, anterior chamber depth and lens thickness (at t-1). LMM was also used to assess the contemporaneous association between IOP and axial length (AL) at t, controlling for the same set of covariates (at t) as before.

RESULTS

Higher IOP was associated with slower axial growth (β = -0.01, 95% CI -0.02 to -0.005, p = 0.001). There was a positive contemporaneous association between IOP and AL (β = 0.03, 95% CI 0.01-0.05, p = 0.004), but this association became progressively less positive with increasing age, as indicated by a negative interaction effect between IOP and age on AL (β = -0.01, 95% CI -0.01 to -0.003, p = 0.001).

CONCLUSIONS

Higher IOP is associated with slower rather than faster axial growth in children with non-pathological high myopia, an association plausibly confounded by the increased influence of ocular compliance on IOP.

Reversal of severe myopia by 24 years of hypotony with subsequent stable refraction after 2 years of normal intraocular pressure

Purpose

To report sustained axial length shortening and hyperopic shift (refraction changed from -8 to -2 diopters) induced by 24 years of profound IOP (intraocular pressure) reduction with subsequent refractive stability 2 years after IOP rose to 11-17 mm Hg.

Observations

A 25-year-old woman with elevated episcleral venous pressure glaucoma underwent non-penetrating trabeculectomy and subsequent laser goniopuncture in her left eye. She had chronically low IOP (1-12 mm Hg) for the next 24 years. Hypotony maculopathy was present in postoperative years 13-14 and 18-24 but resolved at age 49 when emesis-induced iris prolapse obstructed the filtering passage and transiently raised IOP to 40. Medical management and iridectomy with flap suturing stabilized IOP between 11 and 17 mm Hg.Refraction before OS trabeculectomy was OD -7.50/OS -9.00. In postoperative year 24 spherical equivalent phakic refraction was OD -9.00/OS -1.50. Biometry 1 year after resolution of hypotony showed axial lengths OD 24.8, OS 22.6 mm. Cataract surgery was performed in postoperative years 24/26 (OD/OS) with Tecnis DCBOO intraocular lenses of powers 14.0/21.5 diopters; postoperative refractions, 2 years after OS IOP rose to 11-17 mm Hg, were OD +0.25-0.50 x 015/OS -0.75-1.25 x 160 with 20/25 corrected acuity in each eye.Cardiovascular symptoms 24 years after the onset of her glaucoma led to a diagnosis of severe pulmonary hypertension.

Conclusions and importance

This case demonstrates that 2 decades of chronic IOP reduction can reverse myopia (by > 2 mm reduction in axial length) with subsequent refractive stability 2 years after IOP normalization. In addition, the case shows that ocular signs of pulmonary hypertension may precede cardiovascular signs by 2 decades.

Optic neuropathy in high myopia: Glaucoma or high myopia or both?

Due to the increasing prevalence of high myopia around the world, structural and functional damages to the optic nerve in high myopia has recently attracted much attention. Evidence has shown that high myopia is related to the development of glaucomatous or glaucoma-like optic neuropathy, and that both have many common features. These similarities often pose a diagnostic challenge that will affect the future management of glaucoma suspects in high myopia. In this review, we summarize similarities and differences in optic neuropathy arising from non-pathologic high myopia and glaucoma by considering their respective structural and functional characteristics on fundus photography, optical coherence tomography scanning, and visual field tests. These features may also help to distinguish the underlying mechanisms of the optic neuropathies and to determine management strategies for patients with high myopia and glaucoma.

Common mechanisms underlying diabetic vascular complications: focus on the interaction of metabolic disorders, immuno-inflammation, and endothelial dysfunction

Diabetic vascular complications (DVCs), including macro- and micro- angiopathy, account for a high percentage of mortality in patients with diabetes mellitus (DM). Endothelial dysfunction is the initial and role step for the pathogenesis of DVCs. Hyperglycemia and lipid metabolism disorders contribute to endothelial dysfunction via direct injury of metabolism products, crosstalk between immunity and inflammation, as well as related interaction network. Although physiological and phenotypic differences support their specified changes in different targeted organs, there are still several common mechanisms underlying DVCs. Also, inhibitors of these common mechanisms may decrease the incidence of DVCs effectively. Thus, this review may provide new insights into the possible measures for the secondary prevention of DM. And we discussed the current limitations of those present preventive measures in DVCs research. Video Abstract.

Agreement of intraocular pressure measurement with Corvis ST, non-contact tonometer, and Goldmann applanation tonometer in children with ocular hypertension and related factors

AIM

To access the agreement of intraocular pressure (IOP) values obtained from biomechanically corrected tonometer [Corvis ST (CST)], non-contact tonometer (NCT), and Goldmann applanation tonometer (GAT) in children with NCT measured-IOP (NCT-IOP) values of 22 mm Hg or more, and related factors.

METHODS

A total of 51 eyes with NCT-IOP≥22 mm Hg in children aged 7 to 14y were examined and IOP was measured by CST, NCT, and GAT. Based on GAT measured IOP (GAT-IOP), ocular hypertension (OHT) group (≥22 mm Hg, 24 eyes) and the non-OHT group (<22 mm Hg, 27 eyes) were defined. We compared the agreement of the three measurements, i.e., CST measured IOP (CST-IOP), GAT-IOP, and NCT-IOP, and further analyzed the correlation between the differences in tonometry readings, central corneal thickness (CCT), axial length (AL), optic disc rim volume, and age.

RESULTS

Compared with the OHT group, thicker CCT, larger rim volume, and higher differences between NCT-IOP and GAT-IOP, were found in the non-OHT group. The differences between CST-IOP and GAT-IOP were lower than the differences between NCT-IOP and GAT-IOP in both groups. The mean differences in CST-IOP and GAT-IOP were 1.26 mm Hg (95% limit of agreement ranged from 0.1 to 2.41 mm Hg, OHT group) and 1.20 mm Hg (95% limit of agreement ranged from -0.5 to 3.00 mm Hg, non-OHT group), and the mean differences in NCT and GAT were 3.90 mm Hg (95% limit of agreement ranged from -0.19 to 9.70 mm Hg, OHT group) and 6.00 mm Hg (95% limit of agreement ranged from 1.50 to 10.50 mm Hg, non-OHT group). The differences between CST-IOP and GAT-IOP were not related to CCT, age, and AL in both groups; while the differences between NCT-IOP and GAT-IOP were related to CCT in the OHT group (r=0.93, P<0.001) and to CCT and AL in the non-OHT group (r=0.66, P<0.001, r=-0.81, P<0.001).

CONCLUSION

The accuracy of NCT in the diagnosis of pediatric OHT is low. The agreement of CST-IOP and GAT-IOP was significantly higher in children with and without OHT than in those with NCT-IOP and GAT-IOP. Therefore, CST can be used as a good alternative for IOP measurement in children. The impacts of CCT and AL on NCT measurement need to be fully considered when managing childhood IOP.

Diurnal Variation and Effects of Dilation and Sedation on Intraocular Pressure in Infant Rhesus Monkeys

PURPOSE

Intraocular pressure (IOP) is an important factor in numerous ocular conditions and research areas, including eye growth and myopia. In infant monkeys, IOP is typically measured under anesthesia. This study aimed to establish a method for awake IOP measurement in infant rhesus monkeys, determine diurnal variation, and assess the effects of dilation and sedation.

METHODS

Awake IOP (iCare TonoVet) was measured every 2 h from 7:30 am to 5:30 pm to assess potential diurnal variations in infant rhesus monkeys (age 3 weeks, n = 11). The following day, and every 2 weeks to age 15 weeks, IOP was measured under three conditions: (1) awake, (2) awake and dilated (tropicamide 0.5%), and (3) sedated (ketamine and acepromazine) and dilated. Intraclass correlation coefficient (ICC) was used to determine intersession repeatability, and repeated measures. ANOVA was used to determine effects of age and condition.

RESULTS

At age 3 weeks, mean (±SEM) awake IOP was 15.4 ± 0.6 and 15.2 ± 0.7 mmHg for right and left eyes, respectively (p=.59). The ICC between sessions was 0.63[-0.5 to 0.9], with a mean difference of 2.2 ± 0.3 mmHg. Diurnal IOP from 7:30 am to 5:30 pm showed no significant variation (p=.65). From 3 to 15 weeks of age, there was a significant effect of age (p=.01) and condition (p<.001). Across ages, IOP was 17.8 ± 0.7 mmHg while awake and undilated, 18.4 ± 0.2 mmHg awake and dilated, and 11.0 ± 0.3 mmHg after sedation and dilation.

CONCLUSIONS

Awake IOP measurement was feasible in young rhesus monkeys. No significant diurnal variations in IOP were observed between 7:30 am and 5:30 pm at age 3 weeks. In awake monkeys, IOP was slightly higher after mydriasis and considerably lower after sedation. Findings show that IOP under ketamine/acepromazine anesthesia is significantly different than awake IOP in young rhesus monkeys.

M. R, K. R. V, M. R. S, Gopi A. A cross-sectional study of association between ocular pressures and different grades of myopia in young adults

Introduction and Aim: My­opia is one of the most common refractive errors causing visual disability worldwide. Uncorrected refractive error poses a public health challenge especially in young adults who have to spend most of their time in literary works. Intra ocular pressure (IOP) is one of the crucial factors intertwined in the pathophysiology of myopia. Ocular perfusion pressure (OPP) determines ocular blood flow. Studies done on association between IOP and refractive errors are contradictory. There is paucity of literature on relationship between OPP and myopia. Hence this original article aimed to assess the association of IOP and OPP changes with myopia and to analyze the relationship between ocular pressures with severity of myopia.   Materials and Methods: Hundred normal adults in the age group of 18-24 years of either gender were recruited for the present study. Voluntary written and informed consent was sought from all participants and the refractive power of their eyes was noted. They were categorised into three groups based on the severity of myopia. Controls were the emmetropes. All participants were asked to relax for 5-10 minutes and the resting BP and IOP were recorded using sphygmomanometer and rebound tonometer respectively. OPP was calculated.   Results: IOP values were comparatively higher in myopes than emmetropes.  A significant reduction in OPP values were observed in moderate myopes.   Conclusion: Myopes have a higher IOP suggesting myopia is one of the major risk factor for ocular hypertension. Low OPP values in moderate myopes indicate reduced ocular perfusion, making the progressive myopes highly susceptible to glaucoma. 

Optic nerve injury models under varying forces

PURPOSE

To explore the pathological changes in optic nerve injury models under varying forces.

METHODS

The rats were classified into 4 groups: sham operation (SH), 0.1, 0.3, and 0.5 N. Modeling was performed using the lateral optic nerve pulling method. Seven days after modeling, Brn3a immunofluorescence was used to detect retinal ganglion cell (RGC) number, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was used to detect RGC apoptosis, and flash visual evoked potential (FVEP) was used to detect the optic nerve function on days 1, 3, and 7 after modeling. In addition, LC3 II and P62 expression levels in retinal tissues were detected by western blotting to observe the changes in autophagy levels.

RESULTS

RGC number decreased 7 d after modeling, and it showed a downward trend with increasing damaging force. The number of apoptotic RGCs in ganglion cell layer in the 0.3 and 0.5 N groups was increased and was higher than that in the 0.1 N group. The difference in FVEP of rats in each group was mainly reflected in the P2 peak latency. LC3 II and P62 expression levels in retinal tissue of 0.3 and 0.5 N groups were higher than those of the SH and 0.1 groups; however, the difference between the 0.1 N and SH groups was not statistically significant.

CONCLUSION

Precisely controlling the force of the optic nerve clamping injury model is necessary because different forces acting on the optic nerve will lead to differences in the loss of optic neurons, the conduction function of the optic nerve, and autophagy level in retinal tissues.

Multiple Factors Causing Myopia and the Possible Treatments: A Mini Review

The myopia epidemic has become a global public health problem. Although myopia is progressing worldwide, the recent coronavirus infections 2019 (COVID-19) outbreak has spurred myopia progression. The current evidence-based treatments for humans are atropine eye drops, optical treatment with defocus, use of orthokeratology, extending proximity working distance, pausing from near work every half hour and increased time outside the home. Studies on myopia using animal models have been conducted for more than 40 years. In recent years, new mechanisms of myopia suppression have been revealed from animal experiments such as inflammation control, intraocular pressure control, light control, and the activity of early growth response protein 1 control. This mini-review provides a summary of the scientific evidence currently available on the control of myopia, and the possible treatments mitigating myopia.

Masticatory Muscle Thickness and Activity Correlates to Eyeball Length, Intraocular Pressure, Retinal and Choroidal Thickness in Healthy Women versus Women with Myopia

This study aims to examine the correlations between masticatory and neck muscle thickness and activity versus eyeball length, retinal thickness, choroidal thickness, and intraocular pressure in healthy women versus women with myopia. The study group consisted of 21 women aged 24 years and a control group of 19 women (mean age 23 years). For bioelectrical activity analysis within the temporalis anterior, the superficial part of the masseter muscle, the middle part of the sternocleidomastoid muscle, and the anterior belly of the digastric muscle, an eight-channel BioEMG III electromyograph were used. An M-Turbo ultrasound machine was used to analyze masticatory and neck muscle thickness. The eyeball length was examined by IOL Master 500; choroidal and retinal thickness by Optovue Angiovue; and intraocular pressure by Tono-Pen XL. Refractive errors are related to differences in muscle thickness and electromyographic activity. Bioelectrical activity within the temporalis anterior seems to be associated with ocular length, retinal thickness, and choroidal thickness in women with myopia.