Changes of the ocular refraction among freshmen in National Taiwan University between 1988 and 2005

Link between parental myopia and early-onset high myopia: Insights from a clinical retrospective analysis

INTRODUCTION

Genetic aetiology is suspected in the development of early-onset high myopia (spherical equivalent refractive error [SER] ≤-6.00 D at ≤6 years of age), considering that the role of environmental factors in inducing high myopia is improbable at an early age. Therefore, we aimed to understand if early-onset high myopia is associated with parental myopia in a clinical setting.

METHODS

A retrospective study was conducted in which information about demographics, age of apparent onset of myopia, refractive error, axial length, number of myopic parents, time spent outdoors and time spent on near-work was obtained from electronic medical records (EMR). It included 195 myopic individuals categorised into (1) Early-onset high myopes (EOHM): SER ≤ -6.00 D with age of presentation ≤6 years, (2) Early-onset low myopes (EOLM): SER > -6.00 D with age of apparent onset ≤6 years, (3) Late-onset high myopes (LOHM): SER ≤ -6.00 D with age of presentation and age of apparent onset >6 years and (4) Late-onset low myopes (LOLM): SER > -6.00 D with age of apparent onset >6 years.

RESULTS

Overall, 63% of individuals were found to have parental myopia. The proportion of individuals with EOHM, EOLM, LOHM and LOLM with parental myopia was 57%, 74%, 53% and 64%, respectively. After adjustment for age, gender and environmental factors, the odds of development of EOHM (Odds ratio: 0.78, 95% confidence interval: 0.25-2.48), EOLM (1.54, 0.65-3.67) or LOHM (0.70, 0.30-1.65) were similar in the presence of myopic parents, when compared with LOLM. The SER and axial length did not differ based on the number of myopic parents in any of these categories.

CONCLUSION

This retrospective analysis reveals that the presence of parental myopia, which was self-reported, did not induce additional risk for early-onset high myopia.

High myopia at high altitudes

Background: Optic nerve sheath diameter (ONSD) increases significantly at high altitudes, and is associated with the presence and severity of acute mountain sickness (AMS). Exposure to hypobaria, hypoxia, and coldness when hiking also impacts intraocular pressure (IOP). To date, little is known about ocular physiological responses in trekkers with myopia at high altitudes. This study aimed to determine changes in the ONSD and IOP between participants with and without high myopia (HM) during hiking and to test whether these changes could predict symptoms of AMS. Methods: Nine participants with HM and 18 without HM participated in a 3-day trek of Xue Mountain. The ONSD, IOP, and questionnaires were examined before and during the trek of Xue Mountain. Results: The ONSD values increased significantly in both HM (p = 0.005) and non-HM trekkers (p = 0.018) at an altitude of 1,700 m. In the HM group, IOP levels were greater than those in the non-HM group (p = 0.034) on the first day of trekking (altitude: 3,150 m). No statistically significant difference was observed between the two groups for the values of ONSD. Fractional changes in ONSD at an altitude of 1,700 m were related to the development of AMS (r pb = 0.448, p = 0.019) and the presence of headache symptoms (r pb = 0.542, p = 0.004). The area under the ROC curve for the diagnostic performance of ONSD fractional changes at an altitude of 1,700 m was 0.859 for predicting the development of AMS and 0.803 for predicting the presence of headache symptoms. Conclusion: Analysis of changes in ONSD at moderate altitude could predict AMS symptoms before an ascent to high altitude. Myopia may impact physiological accommodation at high altitudes, and HM trekkers potentially demonstrate suboptimal regulation of aqueous humor in such environments.

Whole-Exome Sequencing Among School-Aged Children With High Myopia

Importance

High myopia (HM) is one of the leading causes of visual impairment worldwide. Genetic factors are known to play an important role in the development of HM.

Objective

To identify risk variants in a large HM cohort and to examine the implications of genetic testing of schoolchildren with HM.

Design, Setting, and Participants

This cohort study retrospectively reviewed whole-exome sequencing (WES) results in 6215 schoolchildren with HM who underwent genetic testing between September 2019 and July 2020 in Wenzhou City, China. HM is defined as a spherical equivalent refraction (SER) of -6.00 diopters (D) or less. The study setting was a genetic testing laboratory and a multicenter school census. Data were analyzed from July 2021 to June 2022.

Main Outcomes and Measures

The frequency and distribution of positive germline variants, the percentage of individuals with HM in both eyes, and subsequent variant yield for common high myopia (CHM; -8.00 D ≤ SER ≤ -6.00 D), ultra myopia (UM; -10.00 D ≤ SER < -8.00 D), and extreme myopia (EM; SER < -10.00 D).

Results

Of the 6215 schoolchildren with HM, 3278 (52.74%) were male. Their mean (SD) age was 14.87 (2.02) years, including 355 students in primary school, 1970 in junior high school, and 3890 in senior high school. The mean (SD) SER was -7.51 (-1.36) D for the right eye and -7.46 (-1.34) D for the left eye. Among schoolchildren with HM, genetic testing yielded 271 potential pathogenic variants in 75 HM candidate genes in 964 diagnoses (15.52%). A total of 36 known variants were found in 490 HM participants (7.88%) and 235 protein-truncating variants (PTVs) in 506 participants (8.14%). Involved variant yield was significantly positively associated with SER (Cochran-Armitage test for trend Z = 2.5492; P = .01), which ranged from 7.66% in the CHM group, 8.70% in the UM group, to 11.90% in the EM group. We also found that primary school students with EM had the highest variant yield of PTVs (8 of 35 students [22.86%]), which was 1.77 and 4.78 times that of the UM and CHM, respectively.

Conclusions and Relevance

In this cohort study of WES for HM, several potential pathogenic variants were identified in a substantial number of schoolchildren with HM. The high variation frequency in younger students with EM can provide clues for genetic screening and clinical examinations of HM to promote long-term follow-up assessment.

The underestimated role of myopia in uncorrectable visual impairment in the United States

We estimate the US prevalence of uncorrectable visual impairment in 2050 accounting for the changing distribution of both age and myopia. Age projections of the US population (from an estimated total of 379 million in 2050), were taken from the US census website. The distribution of myopia, by severity, was calculated from literature-derived prevalence estimates of 58.4% (≤ - 0.50 D, 2050 projection) and 33.1% (≤ - 1.00 D, 1999-2004 estimate) to provide predicted and conservative estimates, respectively. Uncorrectable visual impairment as a function of age and refractive error was modelled by multiple linear regression. Finally, the likely number of individuals in the US with visual impairment in 2050 was calculated. For a projected myopia prevalence of 58.4%, 222 million are projected to be myopic and 48 million will have high myopia (- 5 D or worse). The projected total number with uncorrectable visual impairment is 11.4 million of which 4.9 million cases (43%) of visual impairment will be directly attributed to increased risk of eye disease associated with myopia. For a projected myopia prevalence of 33.1%, 8.9 million are projected to have uncorrectable visual impairment of which 2.4 million cases (27%) will be directly attributed to myopia. It is predicted that between 27 and 43% of uncorrectable visual impairment in the US population in 2050 will be directly attributable to myopia. Failure to account for the increasing prevalence of myopia among the aging population leads to a substantial underestimate of the prevalence of visual impairment.

Long-Term Efficacy of Orthokeratology to Control Myopia Progression

OBJECTIVES

To assess the efficacy of orthokeratology in controlling the rate of myopia progression in children and investigate the factors associated with axial length (AL) growth rate with an average of 48 months of orthokeratology lens wear.

METHODS

As a retrospective study, 84 subjects underwent relatively complete ophthalmologic examinations. After initial lens wear, AL was measured on average every 12 months. The linear mixed-effects model (LMM) was used to compare the differences in AL growth rates at each time interval. The contribution of the independent variables to AL change was assessed using multiple linear regression.

RESULTS

In the LMM, there was a significant difference in the AL growth rate ( P <0.001) at each follow-up. The growth rate of AL was associated with initial AL, spherical equivalent refractive errors (SERs) and diameter of lens ( P =0.045, 0.003 and 0.037, respectively). When the baseline age was included as a factor, the influence of initial AL and SER became insignificant in the analysis, whereas age and diameter of lens were significantly correlated with the growth rate of AL ( P< 0.001 and P< 0.001, respectively). There were significant differences in growth rates among different age groups.

CONCLUSIONS

Results of the study demonstrated that the factors associated with lower growth rate in AL were older age and longer diameter of lens.

Stereopsis after bilateral implantation of Toric intraocular lenses in high myopic cataract patients with astigmatism

Purpose

To evaluate near, intermediate, distance visual acuity and stereopsis after bilateral implantation of Toric intraocular lenses (IOLs) in high myopic patients with astigmatism.

Methods

Bilateral Toric or non-Toric IOL implantation (n ​= ​40 eyes each) was performed on high myopic cataract eyes with astigmatism. Best-corrected distance visual acuity (BCDVA), uncorrected intermediate visual acuity (UCIVA), uncorrected near visual acuity (UCNVA), residual refractive astigmatism (RRA), and near, intermediate, and distance stereoacuity were measured postoperatively at 7 days, 1 month, and 3 months.

Results

The three-month postoperative BCDVA, UCIVA, and UCNVA of the Toric group were 0.08 ​± ​0.07, 0.30 ​± ​0.11, and 0.23 ​± ​0.14 LogMAR. All improved over the preoperative assessments (P ​< ​0.05). The RRA, UCIVA, and UCNVA were significantly better in the Toric group than the non-Toric group at all follow-up examinations (all P ​< ​0.05). At 3 months, the median near and intermediate stereoacuity of the Toric group were 100 (range 40 - 400) and 120 (range 50 - 400) arcsec, which were better than the non-Toric group (both P ​< ​0.05). Fine near stereopsis ≥100 arcsec was present in 65% of the Toric patients, and 50% had good intermediate stereopsis of ≥100 arcsec. However among non-Toric patients, only 15% and 5% achieved fine near and intermediate stereopsis. The postoperative BCDVA and best-corrected distance stereoacuity were similar in the two groups (P ​> ​0.05).

Conclusions

In bilateral high myopic cataract patients with astigmatism, Toric IOLs not only improved UCIVA, UCNVA, and RRA, but also enhanced near and intermediate stereopsis acuity.

Meandered and muddled: a systematic review on the impact of air pollution on ocular health

From the years 1970-2023, a systematic overview of the diverse consequences of particulate matter on eye health and a disease classification according to acute, chronic, and genetic are presented using the PubMed, Research Gate, Google Scholar, and Science Direct databases. Various studies on medical aspects correlate with the eye and health. However, from an application perspective, there is limited research on the ocular surface and air pollution. The main objective of the study is to uncover the relationship between eye health and air pollution, particularly particulate matter, along with other external factors acting as aggravators. The secondary goal of the work is to examine the existing models for mimicking human eyes. The study is followed by a questionnaire survey in a workshop, in which the exposure-based investigation was tagged based on their activity. This paper establishes a relationship between particulate matter and its influence on human health, leading to numerous eye diseases like dry eyes, conjunctivitis, myopia, glaucoma, and trachoma. The results of the questionnaire survey indicate that about 68% of the people working in the workshop are symptomatic with tears, blurred vision, and mood swings, while 32% of the people were asymptomatic. Although there are approaches for conducting experiments, the evaluation is not well defined; empirical and numerical solutions for particle deposition on the eye are needed. There prevails a broad gap in the arena of ocular deposition modeling.

The prevalence of refractive errors in college students in Israel

PURPOSE

To determine the prevalence of refractive errors in Jewish and Arab college students in Israel and associations with ethnicity and sex.

METHODS

In this retrospective cross-sectional study, first-year college students underwent non-cycloplegic autorefraction and answered a questionnaire to assess age, sex, and self-identified ethnicity. Spherical equivalent refractive error (SER) was calculated, and the prevalence of hyperopia (>+0.50 Diopter, D), emmetropia (>-0.50 to +0.50 D), myopia (≤-0.50D, low ≤-0.50 to >-3.0D, moderate <-3.0 to >-6.0D, high ≤-6.0D), and astigmatism (>0.50D) were determined. Groups were compared using Chi-square or Fisher test. Univariate and multivariate analyses were conducted to identify factors associated with refractive errors.

RESULTS

Participants (n = 807) had a mean age of 22.1 ± 2.6 years (range: 17-30 years) and SER of -1.7 ± 2.2D (range: -13.3 to +5.7D). The prevalence and 95% confidence internal of myopia was 66.3% (63.0-69.6). Jewish students had a higher prevalence than Arab students for myopia (69.2% vs 60.3%), moderate (18.5% vs 12.2%) and high myopia (5.9% vs 1.9%) and astigmatism (51.4% vs 43.9%, p<0.05 for all), but not low myopia or hyperopia. Females had a higher prevalence of myopia than males (68.1% vs 58.7%, p<0.03). Jewish ethnicity was associated with myopia (OR=1.48, p = 0.01) and moderate myopia (OR=1.72, p = 0.01), and studying optometry was associated with moderate myopia (OR=1.63, p = 0.02). Sex and age were not associated with myopia.

CONCLUSION

Myopia prevalence in Israeli college students is high, showing associations with Jewish, but not Arab, ethnicity, suggesting that ethnic factors may play a role in the refractive differences between Arabs and Jews.

Modelling the refractive and imaging impact of multi-zone lenses utilised for myopia control in children's eyes

PURPOSE

To develop an optical model of a child's eye to reveal the impact of target distance and accommodative behaviour on retinal image quality when fitted with multi-zone lenses.

METHODS

Pupil size, aberration levels and accommodative lag were adjusted for models viewing stimuli at 400, 100, 33 and 20 cm. Distributions of defocus across the pupil and simulated retinal images were obtained. An equivalent 16-point letter was imaged at near viewing distances, while a 0.00 logMAR (6/6) letter was imaged at 400 cm. Multi-zone lenses included those clinically utilised for myopia control (e.g., dual-focus, multi-segmented and aspherical optics).

RESULTS

Viewing distance adjustments to model spherical aberration (SA) and pupil radius resulted in a model eye with wider defocus distributions at closer viewing distances, especially at 20 cm. The increasing negative SA at near reduced the effective add power of dual-focus lenses, reducing the amount of myopic defocus introduced by the centre-distance, 2-zone design. The negative SA at near largely compensated for the high positive SA introduced by the aspheric lens, removing most myopic defocus when viewing at near. A 0.50 D accommodative lag had little impact on the legibility of typical text (16-point) at the closer viewing distances.

CONCLUSIONS

All four multi-zone lenses successfully generated myopic defocus at greater viewing distances, but two failed to introduce significant amounts of myopic defocus at the nearest viewing distance due to the combined effects of pupil miosis and negative SA. Typical 16-point type is easily legible at near even in presence of the multi-zone optics of lenses utilised for myopia control and accommodative lag.

Choriocapillaris Changes in Myopic Macular Degeneration

Purpose

Myopic macular degeneration (MMD) can cause irreversible vision loss. Thinner choroid is associated with increased MMD severity. This cross-sectional study analyzed choriocapillaris (CC) alterations in MMD.

Methods

Axial length (AL), best-corrected visual acuity (BCVA), fundus photography, and swept-source optical coherence tomography angiography (SS-OCTA) were assessed in controls and high myopes (spherical equivalent ≤ −6 diopters). Myopic patients with grade 2 MMD (macular diffuse chorioretinal atrophy [MDCA]), high axial myopia (AL ≥ 26.5 mm), and BCVA ≥ 20/40 were compared with controls without MMD. CC mean thickness was measured from 3 × 3-mm SS-OCTA scans by identifying CC peaks in A-scan intensity profiles. CC flow deficit percent (CC FD%) was quantified using a fuzzy C-mean local thresholding method on en face OCTA images. Multivariate regressions compared CC thickness and CC FD% between myopic patients and controls, correcting for age and other confounders.

Results

Sixteen eyes with MDCA (AL, 26.96–33.93 mm; ages, 40–78 years) were compared with 51 control eyes (AL, 21.65–25.84 mm; ages, 19–88 years). CC thickness in patients with MDCA was 66% lower than that in controls (5.23 ± 0.68 µm [mean ± SD] vs. 15.46 ± 1.82 µm; P < 0.001). CC FD% in patients with MDCA was 237% greater than in controls (26.5 ± 4.3 vs. 11.2 ± 4.6; P < 0.001).

Conclusions

Patients with MDCA with good visual acuity had thinner CC and increased CC FD%, or reduced CC flow, compared with controls. Patients with grade 2 MMD and good visual acuity demonstrated significant choriocapillaris alterations, suggesting that choriocapillaris perfusion defects contribute to the pathogenesis of MMD.

Translational Relevance

Given the potential vascular etiology for MMD, current research about revascularization of ischemic retina likely has implications for the treatment of MMD.

Relationship Between Myopia and Other Risk Factors With Anxiety and Depression Among Chinese University Freshmen During the COVID-19 Pandemic

Purpose: To investigate the association of myopia and other risk factors with anxiety and depression among Chinese university freshmen during the coronavirus disease 2019 (COVID-19) pandemic.

Methods: This cross-sectional study was conducted at the Tianjin Medical University from October 2020 to December 2020. Ophthalmic examination of the eyes was performed by an experienced ophthalmologist. Detailed information on depression, anxiety, and other risk factors was collected via the Self-rating Anxiety Scale and Self-rating Depression Scale.

Results: The overall prevalence of anxiety and depression in our study was 10.34 and 25.13%, respectively. The prevalence of myopia and high myopia as 92.02 and 26.7%, respectively. There were significant associations between anxiety and spectacle power [odds ratios (OR) = 0.89; 95% CI: 0.81–0.98, P = 0.019], sphere equivalent (OR = 0.89; 95% CI: 0.81– 0.98, P = 0.025), sleep time (OR = 0.53; 95% CI: 0.35–0.79, P = 0.002), and body mass index (OR = 0.93; 95% CI: 0.86–0.99, P = 0.047). In the multivariable linear regression models, spectacle power (β = −0.43; 95% CI: −0.68 to −0.19, P = 0.001) and sphere equivalent (β = −0.36; 95% CI: −0.60 to −0.11, P = 0.005) were negatively associated with anxiety scores, whereas axial length (β = 0.54; 95% CI: 0.02–1.07, P = 0.044) was positively correlated with anxiety scores. Every 1 h decrease in sleep time was associated with a 0.12-point increase in depression score.

Conclusion: Myopia was associated with anxiety and anxiety scores. The greater the degree of myopia, the higher the anxiety score. However, myopia was not found to be associated with depression. The results highlight the importance of providing psychological support to students with myopia during the COVID-19 pandemic.

Ocriplasmin for treatment of vitreomacular traction and macular hole: A systematic literature review and individual participant data meta-analysis of randomized, controlled, double-masked trials

Ocriplasmin is used to treat vitreomacular traction (VMT), with or without full-thickness macular hole (MH). We systematically reviewed the evidence on ocriplasmin's effect on vitreomacular adhesion resolution (VMAR), MH closure, vitrectomy, and best-corrected visual acuity (BCVA) and investigated the effect of baseline covariates on outcome. We applied individual participant data meta-analyses to the entire population and to subgroups defined by MH or epiretinal membrane (ERM) presence. Safety data were pooled and tabulated. Five randomized controlled trials (1,067 participants) were included. Six months after treatment, ocriplasmin achieved higher rates of VMAR and MH closure versus control, lowered vitrectomy odds, and increased the likelihood of a ≥10-letter BCVA increase. VMAR rates were lower when ERM, broad VMA (> 1500 µm), diabetic retinopathy, or pseudophakia were present and higher in younger participants, women, and eyes with MHs. Ocriplasmin-treated participants experienced more short-term visual impairment that was not predictive of final BCVA, as well as vitreous floaters, photopsia, photophobia, eye pain, blurred vision, and dyschromatopsia. The most common serious adverse events for ocriplasmin and control, respectively, were MH progression (22.5%, 17.3%), new MH (1.5%, 3.4%) and retinal detachment (0.8%, 1.2%). Ocriplasmin promotes VMAR and MH closure. Transient visual phenomena are not uncommon.

IMI Impact of Myopia

The global burden of myopia is growing. Myopia affected nearly 30% of the world population in 2020 and this number is expected to rise to 50% by 2050. This review aims to analyze the impact of myopia on individuals and society; summarizing the evidence for recent research on the prevalence of myopia and high myopia, lifetime pathological manifestations of myopia, direct health expenditure, and indirect costs such as lost productivity and reduced quality of life (QOL). The principal trends are a rising prevalence of myopia and high myopia, with a disproportionately greater increase in the prevalence of high myopia. This forecasts a future increase in vision loss due to uncorrected myopia as well as high myopia-related complications such as myopic macular degeneration. QOL is affected for those with uncorrected myopia, high myopia, or complications of high myopia. Overall the current global cost estimates related to direct health expenditure and lost productivity are in the billions. Health expenditure is greater in adults, reflecting the added costs due to myopia-related complications. Unless the current trajectory for the rising prevalence of myopia and high myopia change, the costs will continue to grow. The past few decades have seen the emergence of several novel approaches to prevent and slow myopia. Further work is needed to understand the life-long impact of myopia on an individual and the cost-effectiveness of the various novel approaches in reducing the burden.

Biological Mechanisms of Atropine Control of Myopia

Myopia is a global problem that is increasing at an epidemic rate in the world. Although the refractive error can be corrected easily, myopes, particularly those with high myopia, are susceptible to potentially blinding eye diseases later in life. Despite a plethora of myopia research, the molecular/cellular mechanisms underlying the development of myopia are not well understood, preventing the search for the most effective pharmacological control. Consequently, several approaches to slowing down myopia progression in the actively growing eyes of children have been underway. So far, atropine, an anticholinergic blocking agent, has been most effective and is used by clinicians in off-label ways for myopia control. Although the exact mechanisms of its action remain elusive and debatable, atropine encompasses a complex interplay with receptors on different ocular tissues at multiple levels and, hence, can be categorized as a shotgun approach to myopia treatment. This review will provide a brief overview of the biological mechanisms implicated in mediating the effects of atropine in myopia control.

Visual Performance of Center-distance Multifocal Contact Lenses Fit Using a Myopia Control Paradigm

PURPOSE

The purpose of this study was to examine the visual performance of center-distance MFCLs in nonpresbyopic adults under different illumination and contrast conditions compared with a single-vision contact lens (SVCL).

METHODS

Twenty-five adult subjects were fit with three different lenses (CooperVision Biofinity D MFCL +2.50 add, Visioneering Technologies NaturalVue MFCL, CooperVision Biofinity sphere). Acuity and reading performance were evaluated.

RESULTS

A statistically significant difference in high-contrast distance acuity was observed (Biofinity, -0.18 ± 0.06; Biofinity MFCL, -0.14 ± 0.08; NaturalVue MFCL, -0.15 ± 0.03; repeated-measures [RM] ANOVA, P = .02). Under mesopic, high-contrast conditions, MFCLs performed worse than SVCLs (Biofinity, -0.05 ± 0.091; Biofinity MFCL, +0.03 ± 0.09; NaturalVue MFCL, +0.05 ± 0.091; RM-ANOVA, P < .0001). Under low-contrast conditions, MFCLs performed one line worse in photopic lighting and two lines worse under mesopic conditions (RM-ANOVA, P < .0001). Glare reduced acuity by 0.5 logMAR for all lenses (RM-ANOVA, P < .001). A statistically significant difference in near acuity was observed (RM-ANOVA, P = .02), but all lenses achieved acuity better than -0.1 logMAR (Biofinity, -0.16 ± 0.06; Biofinity MFCL, -0.17 ± 0.04; NaturalVue MFCL, -0.13 ± 0.08). Reading performance in words per minute (wpm) was worse with MFCLs (Biofinity MFCL, 144 ± 22 wpm; NaturalVue MFCL, 150 ± 28 wpm) than with SVCLs (156 ± 23 wpm; RM-ANOVA, P = .02) regardless of letter size (RM-ANOVA, P = .13). No difference in acuity between the MFCLs was detected (RM-ANOVA: all, P > .05).

CONCLUSIONS

Multifocal contact lenses perform similarly to SVCLs for high-contrast targets and display reduced low-contrast acuity and reading speed. Practitioners should recognize that high-contrast acuity alone does not describe MFCL visual performance.

Paecilomyces/Purpureocillium keratitis: A consecutive study with a case series and literature review

Paecilomyces/Purpureocillium species is an emerging pathogen of fungal keratitis; the risk factor, clinical course, and outcome of Paecilomyces/Purpureocillium keratitis need more exploration. We retrospectively reviewed 12 patients with culture-proven Paecilomyces/Purpureocillium keratitis in our hospital from 2003 to 2017 and combined them with 50 previous cases reported after the review conducted by Yuan et al. in 2009. Clinical features between the previously and newly reported cases were compared using the publication by Yuan et al. as a cutoff point. The mean age of the 62 newly reported patients with Paecilomyces/Purpureocillium keratitis was 52.7 years. Of these, contact lens wear was the most common predisposing factor (n = 32, 52%), followed by a preexisting corneal disease or previous ocular surgery (n = 12, 19%), and trauma (n = 8, 13%). Fifty eyes (81%) were treated with voriconazole, of which 31 (63%) were medically cured. Twenty-one of 62 eyes (34%) required therapeutic surgery. Compared with the 42 patients reported by Yuan et al., the patients were younger (P = .025); a higher proportion of the patients were contact lens wearers (P = .005); more patients were treated with voriconazole (P = .000); fewer patients required therapeutic surgery (P = .000) in recent reports. Contact lens use has become the major risk factor for Paecilomyces/Purpureocillium keratitis. The surgical rate has been significantly lower in recent publications, probably because of the prevalent use of voriconazole.

The Effect of Relative Corneal Refractive Power Shift Distribution on Axial Length Growth in Myopic Children Undergoing Orthokeratology Treatment

PURPOSE

To quantify the spatial distribution of relative corneal refractive power shift (RCRPS) to investigate its association with axial length growth.

METHODS

Eighty myopic children were randomly assigned for fitting with type A or B lenses. Axial lengths and corneal topographies were measured at baseline and the 1-, 6-, and 12-months follow-up visits. Treatment-zone decentrations and sizes were derived from tangential maps. RCRPSs were computed by taking the difference between after-treatment and baseline axial maps and then subtracting the apex value. Values at the same radius were averaged to obtain an RCRPS profile, from which four distributional parameters were extracted: the peak value (Rmax), the location where the profile first reached its half peak (X50), and the powers summed within 4- and 8-mm diameter areas (Sum4 and Sum8, respectively). Linear mixed models were used to analyse the correlation between the AL growth and the distributional parameters.

RESULTS

At baseline, no significant differences were observed between the two groups. After treatment, Axial length growth was significantly smaller in subjects fitted with type-B lenses (0.15 ± 0.16 vs 0.25 ± 0.22 mm, P = .028). Smaller treatment-zones (1.56 ± 0.14 vs 1.75 ± 0.13 mm, P < .01), smaller X50 values (1.56 ± 0.39 vs 1.98 ± 0.28 mm, P < .01), and greater Sum4 values (11.83 ± 6.47 vs 8.14 ± 5.06 D, P = .01) were also observed in subjects wearing type-B lenses. Among the distributional parameters, only X50 was significantly associated with AL growth in the multiple regression analysis (P = .005).

CONCLUSION

The spatial distribution of RCRPS is critical in retarding AL growth, and the ones reaching peak within a shorter distance from the apex may provide better myopia control.

Corneal biomechanical properties in myopic eyes evaluated via Scheimpflug imaging

Background

To investigate the biomechanical properties of the cornea in myopic eyes using corneal visualization Scheimpflug technology (Corvis ST). The relationships between the biomechanical properties of the cornea and the degree of myopia were also investigated.

Methods

265 eyes of 265 subjects were included. Based on spherical equivalent (SE) in diopters (D), participants were divided into four groups: low myopia/control (SE: − 0.50 to − 3.00D), moderate myopia (SE: − 3.00 to − 6.00D), high myopia (SE: − 6.00 to − 10.00D) and severe myopia (SE greater than − 10.00D). Axial length (AL), anterior segment parameters, and corneal biomechanical properties were obtained with the Lenstar LS900, Pentacam HR and Corvis ST, respectively.

Results

Mean (±SD) SE was − 7.29 ± 4.31D (range: − 0.63 to − 25.75D). Mean AL was 26.31 ± 1.82 mm (range: 21.87 to 31.94 mm). Significant differences were detected within the four groups in terms of six corneal biomechanical parameters: deformation amplitude (DA), time from start until second applanation (A2-time), length of flattened cornea at the second applanation (A2-length), corneal velocity during the first and second applanation (A2-velocity), time from start to highest concavity (HC-time), and central curvature at highest concavity (HC radius). AL was positively associated with DA whereas negatively associated with A1-velocity and A2-length. SE was positively associated with A2-time, HC-time and A2-velocity, whereas negatively associated with DA. IOP was positively associated with four corneal biomechanical parameters and negatively associated with three parameters.

Conclusions

Eyes with severe myopia showed greater DA, lesser A2 time, HC time, and faster A2-velocity compared to low to high myopia. This suggests the cornea becomes weaker and more deformable with elongation of axial length with corresponding increases in myopia. DA, A2-time and A2-velocity could be useful corneal biomechanical indicators in patients with myopia.

Thirty-five-year trend in the prevalence of refractive error in Austrian conscripts based on 1.5 million participants

Background

To quantify the current burden of myopia and hyperopia in Austrian young men and the time trend of myopia in the past 35 years by individual and social correlates.

Method

We included data on all Austrian military conscripts from 1983 to 2017 (n=1 507 063) from six medical investigation stations. Young men provided data on education, weight and height for calculating body mass index, blood pressure and resting heart rate. Non-cycloplegic refractions were measured by an autorefractometer. Spherical equivalent was calculated by standard formula (sphere+cylinder/2, unit dioptres (D)). Myopic refractive error was defined as <−0.5 D). Hyperopic refractive error was defined as >0.5 D.

Results

The largest burden of refractive error in Austria is myopia, which rose from 13.8% to 24.4% over 35 years, with less than 5% hyperopic population. Over time, the prevalence of myopia was constantly lower yet increased more rapidly among those with low education levels (11.4%–21.7%) compared with those with higher education (24.5%–29.6%) in all medical investigation stations. We found consistent associations of some unfavourable health indicators (underweight: ORs 1.1–1.4, higher resting heart rate: all p trend <0.001) with higher myopia prevalence, which point towards lifestyle factors playing an important role in the development of myopia.

Conclusion

Primary preventive measures are needed to curb the observed trend in myopia among Austrian young men. Future research should investigate the impact of modifiable factors on myopia development and progression, particularly lifestyle factors that are dramatically shifting.

Mental health status of parents of young patients with high myopia

Objective

The study aim was to investigate the mental health status of parents of patients with high myopia using the Symptom Checklist-90 (SCL-90).

Methods

The parents of 160 young patients with high myopia (high myopia group) and 80 healthy children (control group) participated in the study. The SCL-90 was used to evaluate mental health status. The SCL-90 total score and scores on each factor were calculated and compared between the two groups.

Results

The total SCL-90 score, total mean score, positive score and scores on somatization, interpersonal sensitivity, depression, anxiety, hostility, psychosis, diet and sleep were significantly higher in fathers and mothers of patients with high myopia than in parents of control group children. There were statistically significant between-group differences in the above indices.

Conclusion

Parents of children with high myopia are more likely to develop mental health problems than parents of healthy children. This suggests that mental health interventions for parents should not be ignored in the treatment and control of high myopia patients.

Accommodation and its role in myopia progression and control with soft contact lenses

PURPOSE

To examine the impact of contact lens optical design on accommodative behaviour of children and the correlation between myopia progression and the accommodative response of the eye while wearing a contact lens designed for myopia control.

METHODS

A post-hoc analysis was conducted on data from a previously published myopia control trial. A total of 109 subjects (aged 8 to 11 years, myopia: -0.75 to -4.00 D) wore either a Control (single-vision, n = 57) or a Test (with positive spherical aberration, +SA, n = 52) soft contact lens, binocularly for 1 year. Accommodative response was measured as the subject observed targets at -1.00 to -4.00 D vergence using the Grand Seiko WAM-5500 open-field autorefractor (www.grandseiko.com). Slope of accommodative response (SAR) as well as distance and near phoria and stimulus accommodative convergence/accommodation (AC/A) were compared between each group at baseline without study lenses and at 1-week and 1-year visits with study lenses. The SAR was also compared to changes in axial length (AL) and spherical equivalent cycloplegic auto refraction (SECAR).

RESULTS

At baseline, there was no significant difference in SAR between the two study groups (ΔSAR = -0.039, p = 0.84). At 1 week, mean SAR of the Test group was significantly less than for the Control group (ΔSAR = -0.203, p < 0.0001), an effect that persisted to 1 year (ΔSAR = -0.129, p < 0.0001). In the Test group, greater SAR was associated with less change in AL (regression coefficient: -0.59 mm, p < 0.0001) and SECAR (regression coefficient: 1.12 D, p = 0.006) at 1 year. In the Control group, associations between SAR and change in AL and SECAR were not statistically significant. Compared to the Control group, eyes of the Test group appeared to be more exophoric with study lenses, however, the difference between the two groups was only significant at 1 week for distance phoria and 1 year for near phoria.

CONCLUSION

The soft contact lens with +SA for controlling myopia progression resulted in an apparent decrease in mean accommodation. Within the Test group, reduced accommodative response correlated with greater myopia progression, suggesting some subjects in the Test group utilised the +SA for near viewing, inducing hyperopic defocus at the retina. Accordingly, the potential impact of a lens optics on accommodative function should be considered during design of myopia control lenses.

PM2.5 and NOx exposure promote myopia: clinical evidence and experimental proof

Myopia is caused by complex genetic and environmental factors. However, information regarding the effect of long-term exposure to air pollutants on the risk of development of myopia is lacking. We collected data from two linked databases: the Taiwan National Health Insurance Research Database (NHIRD) and the Taiwan Air Quality-Monitoring Database (TAQMD). A total of 15,822 children (16.3%) were diagnosed with myopia within the cohort. The incidence rate of myopia increased with exposure to increasing concentrations of particulate matter (PM2.5) and nitrogen oxides (NOx), increasing from 15.8 to 24.5 and from 13.7 to 34.4, per 1000 person-years, respectively. The adjusted hazard ratio for myopia increased with elevated PM2.5 and NOx exposure concentrations in Q4 to 1.57 and 2.60, respectively, compared to those exposed to the corresponding concentrations in Q1. In the animal experiments, PM2.5 induced myopia in hamsters by enhancing inflammation and was inhibited by resveratrol treatment compared to the control group. The change in axial length in the PM2.5 group was 0.386 ± 0.069 mm versus 0.287 ± 0.086 mm in the control group and 0.257 ± 0.059 mm in the PM2.5 + resveratrol group. We provide both clinical and experimental correlations that exposure to ambient air pollutants is associated with the pathogenesis of myopia.

High Myopia and Its Associated Factors in JPHC-NEXT Eye Study: A Cross-Sectional Observational Study

The increasing prevalence of high myopia has been noted. We investigated the epidemiological characteristics and the related factors of high myopia in a Japanese adult population. Japan Public Health Center-Based Prospective Study for the Next Generation (JPHC-NEXT) Eye Study was performed in Chikusei-city, a rural area in mid-east Japan, between 2013 and 2015. A cross-sectional observational analysis was conducted to investigate prevalence and related factors of high myopia. A total of 6101 participants aged ≥40 years without a history of ocular surgeries was included. High myopia was defined as a spherical equivalent refraction of ≤−6.00 diopters according to the American Academy of Ophthalmology. Potential high myopia-related factors included intraocular pressure (IOP), corneal structure, corneal endothelial cell density, age, height, body mass index, heart rate, blood pressure, biochemical profile, and current history of systemic and ocular disorders. The odds ratios of high myopia were estimated using the logistic regression models adjusted for the associated factors. The prevalence of high myopia was 3.8% in males and 5.9% in females with a significant difference. Age was inversely associated, IOP was positively associated, and none of other factors were associated with high myopia in both sexes. In conclusion, only age and IOP were associated with high myopia in this community-based sample.

Refractive Errors in University Students in Central China: The Anyang University Students Eye Study

Purpose

To assess the prevalence of refractive errors and associated factors in university students in urban areas of Anyang, Central China.

Methods

This is a cross-sectional university-based study of 16- to 26-year-old students in China. Subjects from two universities were invited to undergo a comprehensive eye examination. Cycloplegic refraction was acquired by autorefractor with two drops of 1% cyclopentolate. The prevalence of myopia, high myopia, hyperopia, astigmatism, and anisometropia was calculated. Only data from right eyes were included in analysis.

Results

A total of 7732 eligible subjects were included, with an average age of 20.2 ± 1.4 years. Overall, the mean spherical equivalent (SE) was -2.92 ± 2.48 diopters (D). The prevalence of myopia (SE ≤ -0.50 D), emmetropia, and hyperopia (SE ≥ +0.50 D) was 83.2%, 9.5%, and 7.3%, respectively. Female sex (OR = 1.542; P < 0.001) and science and engineering students (OR = 1.219; P = 0.004) were more likely to be myopic. The prevalence of high myopia, defined using SE ≤ -5.0 D, ≤ -6.0 D, and ≤ -10.0 D, respectively, occurred in 20.2%, 11.1 %, and 0.5%. High myopia (SE ≤ -6.0 D) was statistically associated with female sex (OR = 1.202; P = 0.029) and younger age (OR = 0.896; P = 0.001). The prevalence of astigmatism (cylinder of ≤ -0.75 D) was 28.8%. Astigmatism was associated with male sex (OR = 0.824; P = 0.001) and younger age (OR = 0.925; P = 0.001).

Conclusions

A prevalence of 83.2% for myopia and 11.1% for high myopia (SE ≤ -6.0 D) was found in central Chinese university students. In the future, this generation of university students may encounter long-term, vision-threatening effects, especially pathologic myopia.

The Adenosine Receptor Antagonist, 7-Methylxanthine, Alters Emmetropizing Responses in Infant Macaques

Purpose

Previous studies suggest that the adenosine receptor antagonist, 7-methylxanthine (7-MX), retards myopia progression. Our aim was to determine whether 7-MX alters the compensating refractive changes produced by defocus in rhesus monkeys.

Methods

Starting at age 3 weeks, monkeys were reared with −3 diopter (D; n = 10; 7-MX −3D/pl) or +3D (n = 6; 7-MX +3D/pl) spectacles over their treated eyes and zero-powered lenses over their fellow eyes. In addition, they were given 100 mg/kg of 7-MX orally twice daily throughout the lens-rearing period (age 147 ± 4 days). Comparison data were obtained from lens-reared controls (−3D/pl, n = 17; +3D/pl, n = 9) and normal monkeys (n = 37) maintained on a standard diet. Refractive status, corneal power, and axial dimensions were assessed biweekly.

Results

The −3D/pl and +3D/pl lens-reared controls developed compensating myopic (−2.10 ± 1.07 D) and hyperopic anisometropias (+1.86 ± 0.54 D), respectively. While the 7-MX +3D/pl monkeys developed hyperopic anisometropias (+1.79 ± 1.11 D) that were similar to those observed in +3D/pl controls, the 7-MX −3D/pl animals did not consistently exhibit compensating myopia in their treated eyes and were on average isometropic (+0.35 ± 1.96 D). The median refractive errors for both eyes of the 7-MX −3D/pl (+5.47 D and +4.38 D) and 7-MX +3D/pl (+5.28 and +3.84 D) monkeys were significantly more hyperopic than that for normal monkeys (+2.47 D). These 7-MX–induced hyperopic ametropias were associated with shorter vitreous chambers and thicker choroids.

Conclusions

In primates, 7-MX reduced the axial myopia produced by hyperopic defocus, augmented hyperopic shifts in response to myopic defocus, and induced hyperopia in control eyes. The results suggest that 7-MX has therapeutic potential in efforts to slow myopia progression.

Ocular biometric characteristics of cataract patients in western China

BACKGROUND

We aimed to measure ocular biometric characteristics in older cataract patients from western China.

METHODS

Ocular biometry records were retrospectively analyzed for 6933 patients with cataracts (6933 eyes) at least 50 years old who were treated at West China Hospital of Sichuan University.

RESULTS

Partial coherence laser interferometry gave the following population averages: axial length (AL), 24.32 ± 2.42 mm; anterior chamber depth (ACD), 3.08 ± 0.47 mm; keratometric power (K), 44.23 ± 1.66 diopters; and corneal astigmatism (CA), 1.00 ± 0.92 diopters. The percentage of individuals with AL > 26.5 mm was 13.66%, while the percentage with CA > 1.0 diopters was 35.54%. Mean AL and ACD showed a trend of decrease with increasing age (P < 0.001). AL correlated positively with ACD (Spearman coefficient, 0.542) and CA (0.111), but negatively with K (- 0.411) (all P < 0.01). K also correlated negatively with ACD (- 0.078, P < 0.01).

CONCLUSIONS

These results show, for the first time, that older cataract patients from western China have similar ocular biometric characteristics as other populations. The high prevalence of severe axial myopia warrants further investigation.

Effect of Orthokeratology on myopia progression: twelve-year results of a retrospective cohort study

BACKGROUND

Several studies reported the efficacy of orthokeratology for myopia control. Somehow, there is limited publication with follow-up longer than 3 years. This study aims to research whether overnight orthokeratology influences the progression rate of the manifest refractive error of myopic children in a longer follow-up period (up to 12 years). And if changes in progression rate are found, to investigate the relationship between refractive changes and different baseline factors, including refraction error, wearing age and lens replacement frequency. In addition, this study collects long-term safety profile of overnight orthokeratology.

METHODS

This is a retrospective study of sixty-six school-age children who received overnight orthokeratology correction between January 1998 and December 2013. Thirty-six subjects whose baseline age and refractive error matched with those in the orthokeratology group were selected to form control group. These subjects were followed up at least for 12 months. Manifest refractions, cycloplegic refractions, uncorrected and best-corrected visual acuities, power vector of astigmatism, corneal curvature, and lens replacement frequency were obtained for analysis.

RESULTS

Data of 203 eyes were derived from 66 orthokeratology subjects (31 males and 35 females) and 36 control subjects (22 males and 14 females) enrolled in this study. Their wearing ages ranged from 7 years to 16 years (mean ± SE, 11.72 ± 0.18 years). The follow-up time ranged from 1 year to 13 years (mean ± SE, 6.32 ± 0.15 years). At baseline, their myopia ranged from -0.5 D to -8.0 D (mean ± SE, -3.70 ± 0.12 D), and astigmatism ranged from 0 D to -3.0 D (mean ± SE, -0.55 ± 0.05 D). Comparing with control group, orthokeratology group had a significantly (p < 0.001) lower trend of refractive error change during the follow-up periods. According to the analysis results of GEE model, greater power of astigmatism was found to be associated with increased change of refractive error during follow-up years.

CONCLUSIONS

Overnight orthokeratology was effective in slowing myopia progression over a twelve-year follow-up period and demonstrated a clinically acceptable safety profile. Initial higher astigmatism power was found to be associated with increased change of refractive error during follow-up years.

The effect of transient glare on shape discrimination threshold in myopic adults

BACKGROUND

The aim was to evaluate the effect of transient glare on shape discrimination threshold (SDT) in myopic adults.

METHODS

A total of 162 myopic subjects were enrolled. Of these, 121 had low to mid myopia (-1.00 D to -6.00 D) and 41 had high myopia (-6.13 D to -10.25 D). All subjects had corrected visual acuity of 6/6 or better, and only data for the right eye were included in the study. SDTs were measured with circular D4 (fourth derivative of Gaussian) radial frequency patterns with a radial frequency of four, peak spatial frequency of three cpds, and mean radius of 1.5 degrees. SDTs were measured under two conditions, with and without the presence of transient glare while the stimulus was displayed (duration = 500 ms).

RESULTS

Without transient glare, SDTs were not different between the low-mid (23.84 ± 6.02 arcsec) and high myopia groups (25.17 ± 5.98 arcsec, p = 0.16, Mann-Whitney test). With transient glare, SDTs in all subjects became significantly higher (p < 0.001, Wilcoxon signed-rank test). SDTs in the high myopia group (55.53 ± 18.59 arcsec) became significantly higher than those in the low to mid myopia group (47.55 ± 15.06 arcsec, p = 0.014, Mann-Whitney test). The increments were significantly higher in the high myopia group (28.94 arcsec versus 20.88 arcsec, p = 0.031, Mann-Whitney test). Multiple regression showed that SDTs with glare were significantly associated with SDTs without glare (p < 0.001) and the presence of high myopia (p = 0.015).

CONCLUSIONS

Transient glare significantly increased SDTs in all myopic subjects, with the increment in subjects with high myopia being significantly larger than those in subjects with low to mid myopia.

Refractive errors characteristic of the patients at the Children's Ophthalmology Outpatient Department of Kauno klinikos Hospital (Lithuanian University of Health Sciences) from 1 January 2012 to 31 December 2012

BACKGROUND

The purpose of our study was to assess the distribution and patterns of refractive errors in children for the proper planning of paediatric eye care at the centre.

MATERIAL AND METHODS

The study was conducted in the hospital of the Lithuanian University of Health Sciences in Kaunas, from 1 January 2012 to 31 December 2012. During this period, a total of 11,406 children, aged 0-18 years, were evaluated at the outpatient department of paediatric ophthalmology, Kauno klinikos, the Lithuanian University of Health Sciences. All the children underwent a complete ophthalmic examination with cycloplegic refraction.

RESULTS

Myopia increased from 1.5% (95% CI:1.2, 1.8) in the age group of 0-1 to 44.7% (95% CI:43.46, 45.94) in the age group of 14-18 (p < 0.001). Myopia was associated with older age, female gender (20.3%; 95% CI:19.3, 21.3; p < 0.001). Hypermetropia decreased from 84.6% (95% CI:83.7, 85.5) in the cohort of 0-1 to 11.4% (95% CI: 10.61, 12.19) in the 14-18 age group (p < 0.001). Hypermetropia was associated with younger age, male gender (43.4%; 95% CI:42.16, 44.64; p < 0.001), preterm birth (56.1%; 95% CI:54.86, 57.34; 43.4%; p < 0.001), low birth weight (61.8%; 95% CI:60.59, 63.01; p < 0.001), and birth by Caesarean section (57.1%; 95% CI: 55.87; 58.33) (p < 0.001). The prevalence of astigmatism was 25.5% (95% CI: 24.41; 26.59) (p < 0.001). Astigmatism was associated with female gender (20.1%; 95%. CI: 19.1; 21.1) and too big pregnancy weight (22.1%.; 95%. CI: 21.06; 23.14) (p < 0.001).

CONCLUSIONS

Of the 14-18 age group, 44.7% of the patients were myopic. Of the 0-1 age group, 84.6% were hypermetropic. Astigmatism was detected in about 25.5% of children. The prevalence of refractive errors was associated with age, gender, gestation age, gestation weight, and parental refractive error.

Relationship between higher-order wavefront aberrations and natural progression of myopia in schoolchildren

This study investigated the relationship between higher-order aberrations (HOAs) and myopia progression as well as axial elongation in schoolchildren. We examined cycloplegic refraction, axial length, and wavefront aberrations prospectively in 71 myopic children. Changes in cycloplegic refraction and axial length during a 2-year study period were assessed, and their correlations with HOA components were analyzed. Sixty-four subjects ([mean ± SD] 9.2 ± 1.6 years) completed the 2-year examinations. Cycloplegic refraction was significantly changed after 2 years (P < 0.0001), and the average change (myopia progression) was -1.60 ± 1.04 D. Axial length also increased significantly (P < 0.0001), and the average increase (axial elongation) was 0.77 ± 0.40 mm. Myopia progression and axial elongation showed significant correlations with many components of corneal HOA (P < 0.0001 to P = 0.0270). Multivariate analysis showed that the total HOA of the cornea was the most relevant variable to myopia progression and axial elongation (P < 0.0001). Eyes with larger amounts of corneal HOAs showed less myopia progression and smaller axial elongation, suggesting that corneal HOAs play a role in the refractive and ocular developments in children.

Exome Sequence Analysis of 14 Families With High Myopia

Purpose

To identify causal gene mutations in 14 families with autosomal dominant (AD) high myopia using exome sequencing.

Methods

Select individuals from 14 large Caucasian families with high myopia were exome sequenced. Gene variants were filtered to identify potential pathogenic changes. Sanger sequencing was used to confirm variants in original DNA, and to test for disease cosegregation in additional family members. Candidate genes and chromosomal loci previously associated with myopic refractive error and its endophenotypes were comprehensively screened.

Results

In 14 high myopia families, we identified 73 rare and 31 novel gene variants as candidates for pathogenicity. In seven of these families, two of the novel and eight of the rare variants were within known myopia loci. A total of 104 heterozygous nonsynonymous rare variants in 104 genes were identified in 10 out of 14 probands. Each variant cosegregated with affection status. No rare variants were identified in genes known to cause myopia or in genes closest to published genome-wide association study association signals for refractive error or its endophenotypes.

Conclusions

Whole exome sequencing was performed to determine gene variants implicated in the pathogenesis of AD high myopia. This study provides new genes for consideration in the pathogenesis of high myopia, and may aid in the development of genetic profiling of those at greatest risk for attendant ocular morbidities of this disorder.

Factors related to axial length elongation and myopia progression in orthokeratology practice

Purpose

To investigate which baseline factors are predictive for axial length growth over an average period of 2.5 years in a group of children wearing orthokeratology (OK) contact lenses.

Methods

In this retrospective study, the clinical records of 249 new OK wearers between January 2012 and December 2013 from the contact lens clinic at the Eye and ENT Hospital of Fudan University were reviewed. The primary outcome measure was axial length change from baseline to the time of review (July-August 2015). Independent variables included baseline measures of age at initiation of OK wear, gender, refractive error (spherical equivalent), astigmatism, average keratometry, corneal toricity, central corneal thickness, white-to-white corneal diameter, pupil size, corneal topography eccentricity value (e-value), intraocular pressure (IOP) and total time in follow-up (months total). The contributions of all independent variables on axial length change at the time of review were assessed using univariate and multivariable regression analyses.

Results

Univariate analyses of the right eyes of 249 OK patients showed that smaller increases in axial length were associated with older age at the onset of OK lens wear, greater baseline spherical equivalent myopic refractive error, less time in follow-up and a smaller e-value. Multivariable analyses of the significant right eye variables showed that the factors associated with smaller axial length growth were older age at the onset of OK lens wear (p<0.0001), greater baseline spherical equivalent myopic refractive error (p = 0.0046) and less time in follow-up (p<0.0001).

Conclusions

The baseline factors demonstrating the greatest correlation with reduced axial length elongation during OK lens wear in myopic children included greater baseline spherical equivalent myopic refractive error and older age at the onset of OK lens wear.

Risk factors for myopia progression in second-grade primary school children in Taipei: a population-based cohort study

PURPOSE

To evaluate the 1-year progression of myopia and associated risk factors in second-grade primary school children.

METHODS

The myopia investigation study in Taipei provided semiannual visual acuity testing and cycloplegic refraction for all second-grade primary school children (mean age: 7.49 years) in Taipei who provided parental consent. A questionnaire was distributed to the participants' parents before the first and third examinations. We evaluated 1-year follow-up data for children noted to have myopia on the first examination. Multinomial logistic regression models were applied to assess risk factors associated with myopia progression. Myopia progression was categorised, based on the change in spherical equivalent (ΔSE) over 1 year, as slow (ΔSE>-0.5 dioptres (D)), moderate (-1.0 D<ΔSE≤-0.5 D) or fast (ΔSE≤-1.0 D). Of the 4214 myopic children, data were analysed for 3256 (77.3%) who completed the 1-year follow-up evaluation.

RESULTS

The baseline SE was -1.43±1.1 D. The average ΔSE was -0.42±0.85 D, with 46.96%, 28.50% and 24.54% of the study subjects showing slow, moderate and fast myopia progression, respectively. When compared with slow myopia progression, fast myopia progression was associated with a greater myopic SE at baseline (OR: 0.67, 95% CI: 0.61 to 0.72) and a shorter eye-object distance when doing near work (OR: 1.45, 95% CI: 1.18 to 1.78). More outdoor activity time and self-reported cycloplegic treatment were not associated with slow myopia progression.

CONCLUSIONS

Children with fast annual myopia progression were more myopic at baseline and had a shorter reading distance. Our study results highlight the importance of having children keep a proper reading distance.

Epidemiology of Myopia

Myopia is not a simple refractive error, but an eyesight-threatening disease. There is a high prevalence of myopia, 80% to 90%, in young adults in East Asia; myopia has become the leading cause of blindness in this area. As the myopic population increases globally, the severity of its impact is predicted. Approximately one fifth of the myopic population has high myopia (≥-6 diopters), which results in irreversible vision loss such as retinal detachment, choroidal neovascularization, cataracts, glaucoma, and macular atrophy. The increasing prevalence of school myopia in the past few decades may be a result of gene-environment interactions. However, earlier school myopia onset would accompany faster myopia progression and greater risk of high myopia later in life. Recently, there have been effective interventions to delay the onset of myopia, such as outdoor activity and decreasing the duration of near work. Hyperopia (≤0.5 diopters) is a predictor of myopia. Pharmacological agents and optic interventions such as low-concentration atropine and orthokeratology may slow progression in myopic children. Novel surgeries and anti-vascular endothelial growth factor drugs could deal with some myopic complications. From available evidence, the prevention, control, and treatment of myopia seem to be promising. However, to reduce the impact of myopia in future decades, more work and effort are still needed, including that by governments and intercountry eye health organizations.

Evaluation of high myopia complications prevention program in university freshmen

High myopia is a global eye health problem because of its high incidence of sight-threatening complications. Due to the role of awareness, self-examination, and preventive behavior in prevention of morbidity of high myopia complications, promoting knowledge, capabilities, and attitude of high myopic personnel are required in this regard.In this quasi-experiment study, 31 freshmen with high myopia in a national university were enrolled in 2014. The data were collected by validated and reliable questionnaire based on health belief model (HBM) and self-efficacy theory. The intervention program consisted of 1 educational session lasting 150 minutes by lecturing of high myopia complications, virtual reality experiencing, similarity modeling, and quibbling a film made on high myopia complications preventive concepts.Implementing the educational program showed immediate effect in knowledge, perceived susceptibility, perceived severity, self-efficacy, and preventive behavior intention. While 6 weeks after the educational program, significant increases were observed in cues to action, self-efficacy, and preventive behavior intention.This article provided that, after a single session, there was positive improvement in high myopia complication prevention behavior intention among participants. These positive effects confirmed the efficacy of the education program and will probably induce behavior change.

Soft Contact Lenses with Positive Spherical Aberration for Myopia Control

PURPOSE

To determine whether soft contact lenses with positive spherical aberration (+SA) can slow myopia progression.

METHODS

Eligible subjects (N = 127, primarily Asian) aged 8 to 11 years were randomized to wear either control (spherical design) or test (with +SA) soft daily disposable contact lenses for a minimum of 1 and up to 2 years (treatment phase). Subjects from the initial cohorts (N = 82) were then followed for an additional 1.5 years while wearing a marketed spherical daily disposable contact lens (withdrawal phase). Axial length and spherical equivalent cycloplegic autorefraction (SECAR) were measured at baseline and every 6 months in both phases.

RESULTS

During the first year of treatment, lens type (test vs. control) had a statistically significant impact on axial elongation (p = 0.0409). Eyes wearing test lenses increased in length by 0.11 (65.3%) and 0.14 (38.6%) mm less than eyes wearing control soft lenses at 6 and 12 months, respectively (p < 0.05 at both time points). The principal control of axial elongation occurred during the first 6 months. Spherical equivalent cycloplegic autorefraction change from baseline was significantly less in the test cohort than the control cohort by 0.21D (54.0%) at 6 months (p < 0.05) but not at 12 months (0.14D, p > 0.05). Lens type was not overall a significant factor affecting refractive error change (p = 0.0677). After ceasing treatment, neither the rate of axial elongation nor change in SECAR was significantly different between the initial two cohorts.

CONCLUSIONS

The soft contact lens with +SA slowed axial growth of the eye, although this did not translate into a sustained statistically significant effect on SECAR. The majority of the treatment effect occurred in the initial 6 months of wear. No evidence of rebound effect was observed after ceasing treatment.

Changes in Myopia Prevalence among First-Year University Students in 12 Years

PURPOSE

The aim of this study is to compare the changes in myopia prevalence among Portuguese first-year university students in 2002 and 2014 at the University of Minho.

METHODS

The refractive status and axial length of first-year students at the School of Sciences, University of Minho, were measured in 2014. Refractive error was measured with subjective refraction under cycloplegia and axial length was measured by optical biometry. The data were compared with those obtained from a similar cohort of 111 students in 2002. Myopia was defined as a mean spherical equivalent of ≤-0.50D. A survey was conducted to know the routine of the participants. They were asked how many hours per week (hrs/wk) they had spent, on average in the previous year, watching TV, using the computer, studying, participating in manual hobbies, and participating in outdoor activities.

RESULTS

In 2014, 75 students were assessed (15 male and 60 female) with a mean age (mean ± SD) of 19.8 ± 1.6 years (ranging from 18 to 24 years). The mean refractive error M (spherical equivalent) was -0.77 ± 1.79D and the axial length was 23.74 ± 1.19 mm. The prevalence of myopia was 41.3% (31 of 75). In 2002, the mean refractive error M was 0.01 ± 1.53D, the axial length was 23.40 ± 0.93 mm, and the myopia prevalence was 23.4% (26 of 111). The differences between myopia prevalence and mean refractive error are statistically significant (p < 0.05). A statistically significant increase in the number of hrs/wk spent on near activities (p < 0.05) was found.

CONCLUSIONS

In 12 years, the prevalence of myopia among first-year university students at the School of Sciences of the University of Minho rose from 23.4 to 41.3%. This increase in myopia prevalence could be related to the lifestyle changes of the studied population.

Global Prevalence of Myopia and High Myopia and Temporal Trends from 2000 through 2050

PURPOSE

Myopia is a common cause of vision loss, with uncorrected myopia the leading cause of distance vision impairment globally. Individual studies show variations in the prevalence of myopia and high myopia between regions and ethnic groups, and there continues to be uncertainty regarding increasing prevalence of myopia.

DESIGN

Systematic review and meta-analysis.

METHODS

We performed a systematic review and meta-analysis of the prevalence of myopia and high myopia and estimated temporal trends from 2000 to 2050 using data published since 1995. The primary data were gathered into 5-year age groups from 0 to ≥100, in urban or rural populations in each country, standardized to definitions of myopia of -0.50 diopter (D) or less and of high myopia of -5.00 D or less, projected to the year 2010, then meta-analyzed within Global Burden of Disease (GBD) regions. Any urban or rural age group that lacked data in a GBD region took data from the most similar region. The prevalence data were combined with urbanization data and population data from United Nations Population Department (UNPD) to estimate the prevalence of myopia and high myopia in each country of the world. These estimates were combined with myopia change estimates over time derived from regression analysis of published evidence to project to each decade from 2000 through 2050.

RESULTS

We included data from 145 studies covering 2.1 million participants. We estimated 1406 million people with myopia (22.9% of the world population; 95% confidence interval [CI], 932-1932 million [15.2%-31.5%]) and 163 million people with high myopia (2.7% of the world population; 95% CI, 86-387 million [1.4%-6.3%]) in 2000. We predict by 2050 there will be 4758 million people with myopia (49.8% of the world population; 3620-6056 million [95% CI, 43.4%-55.7%]) and 938 million people with high myopia (9.8% of the world population; 479-2104 million [95% CI, 5.7%-19.4%]).

CONCLUSIONS

Myopia and high myopia estimates from 2000 to 2050 suggest significant increases in prevalences globally, with implications for planning services, including managing and preventing myopia-related ocular complications and vision loss among almost 1 billion people with high myopia.

Altered functional connectivity density in high myopia

Abnormal visual experience can affect the brain structure and function. Visual functional performances of high myopia (HM) individuals were observed to be abnormal in contrast to emmetropics, even with a corrected visual acuity. Attention deficits and brain morphological changes have been revealed in the HM, but it is unknown whether there are functional connectivity (FC) alterations. The current study combined the resting-state functional connectivity density (FCD) mapping and seed-based correlation analysis to investigate FC alterations in the brain of HM. In our results, the HM exhibited decreased short- and long-range FCD in the posterior cingulate cortex/precuneus and decreased long-range FCD in the inferior temporal gyrus, supramarginal gyrus and rostrolateral prefrontal cortex. Specially, long-range FCD in the rostrolateral prefrontal cortex showed a significant positive correlation with the uncorrected visual acuity in the HM. Moreover, the HM showed significantly decreased FC not only between the supramarginal gyrus and rostrolateral prefrontal cortex, but also between networks they belong to, the ventral attention and frontoparietal control networks. These results provide evidence for the FC changes in the HM and may help to understand the attention deficits in myopes.

Refraction data survey: 2nd generation correlation of myopia

The objective herein is to provide refraction data, myopia progression rate, prevalence, and 1st and 2nd generation correlations, relevant to whether myopia is random or inherited. First- and second-generation ocular refraction data are assembled from N = 34 families, average of 2.8 children per family. From this group, data are available from N = 165 subjects. Inter-generation regressions are performed on all the data sets, including correlation coefficient r, and myopia prevalence [%]. Prevalence of myopia is [M] = 38.5 %. Prevalence of high myopes with |R| >6 D is [M-] = 20.5 %. Average refraction is <R> = -1.84 D ± 3.22 (N = 165). For the high myopes, |R| >6 D, prevalence for the parents is [M-] = 25 %, for the 2nd generation [M-] = 16.5 %. Average myopia level for the high myopes, both generations, is <S> = -7.52 D ± 1.31 D (N = 33). Regression parameters are calculated for all the data sets, yielding correlation coefficients in the range r = 0.48-0.72 for some groups of myopes and high myopes, fathers to daughters, and mothers to sons. Also of interest, some categories show essentially no correlation, -0.20 < r < 0.20, indicating that the refractive errors occur randomly. Time series results show myopia diopter rates = -0.50 D/year.

Risk factors for myopia in a discordant monozygotic twin study

PURPOSE

Monozygotic (MZ) twin pairs discordant for disease allow careful examination of environmental factors whilst controlling for genetic variation. The purpose of this study was to examine differences in environmental risk factors in MZ twins discordant for myopia.

METHODS

Sixty four MZ twin pairs discordant for refractive error were interviewed. Discordant twins were selected from 1326 MZ twin pairs from the TwinsUK adult twin registry with non-cycloplegic autorefraction. Discordancy was defined as ≥ 2 Dioptres (D) difference in spherical equivalent (SphE) and discordant for class of refractive error. In a 35-item telephone questionnaire twins were separately asked (and scored) about the risk factors urban/rural residence, occupational status and highest educational level. They responded with more (1), less (-1) or the same (0) as their twin on time spent outside, playing outdoor sport, and on close work aged <16 and 16-25 years. The lower SphE twin's score was subtracted from the higher SphE twin's score, and mean values of the difference calculated for each variable.

RESULTS

Sixty four twin pairs were included (mean age 56, range 30-79 years; mean difference in refraction 3.35 D, S.D. 1.55 D, median difference 2.78 D). Within discordant MZ twin pairs, the more myopic twin was associated with having a higher occupational status (mean score between 16 and 25 years -0.11; 95% CI -0.19 to -0.04; mean score aged >25 years -0.23, 95% CI -0.28 to -0.17), being resident in urban area (mean score -0.26; 95% CI -0.33 to -0.18) and performing more close work (mean score <16 years -0.11; 95% CI -0.18 to -0.05; mean score aged 16-25 years -0.17, 95% CI -0.24 to -0.10) than their twin. The twins who spent more time outdoors (mean score <16 years 0.09; 95% CI 0.03-0.15; mean score aged 16-25 years 0.28, 95% CI 0.15-0.41) or performed more outdoors sports (mean score <16 years 0.13; 95% CI 0.04-0.21; mean score aged 16-25 years 0.23, 95% CI 0.10-0.36) were less likely to be myopic than their twin.

CONCLUSIONS

This study has confirmed known environmental risk factors for myopia. These data will allow selection of discordant twins for epigenetic analysis to advance knowledge of mechanisms of refractive error development.

Controlling myopia progression in children and adolescents

Myopia is a common disorder, affecting approximately one-third of the US population and over 90% of the population in some East Asian countries. High amounts of myopia are associated with an increased risk of sight-threatening problems, such as retinal detachment, choroidal degeneration, cataracts, and glaucoma. Slowing the progression of myopia could potentially benefit millions of children in the USA. To date, few strategies used for myopia control have proven to be effective. Treatment options such as undercorrection of myopia, gas permeable contact lenses, and bifocal or multifocal spectacles have all been proven to be ineffective for myopia control, although one recent randomized clinical trial using executive top bifocal spectacles on children with progressive myopia has shown to decrease the progression to nearly half of the control subjects. The most effective methods are the use of orthokeratology contact lenses, soft bifocal contact lenses, and topical pharmaceutical agents such as atropine or pirenzepine. Although none of these modalities are US Food and Drug Administration-approved to slow myopia progression, they have been shown to slow the progression by approximately 50% with few risks. Both orthokeratology and soft bifocal contact lenses have shown to slow myopia progression by slightly less than 50% in most studies. Parents and eye care practitioners should work together to determine which modality may be best suited for a particular child. Topical pharmaceutical agents such as anti-muscarinic eye drops typically lead to light sensitivity and poor near vision. The most effective myopia control is provided by atropine, but is rarely prescribed due to the side effects. Pirenzepine provides myopia control with little light sensitivity and few near-vision problems, but it is not yet commercially available as an eye drop or ointment. Several studies have shown that lower concentrations of atropine slow the progression of myopia control with fewer side effects than 1% atropine. While the progression of myopic refractive error is slowed with lower concentration of atropine, the growth of the eye is not, indicating a potentially reversible form of myopia control that may diminish after discontinuation of the eye drops. This review provides an overview of the myopia control information available in the literature and raises questions that remain unanswered, so that eye care practitioners and parents can potentially learn the methods that may ultimately improve a child’s quality of life or lower the risk of sight-threatening complications.

Geographic mapping of choroidal thickness in myopic eyes using 1050-nm spectral domain optical coherence tomography

PURPOSE

To provide a geographical map of choroidal thickness (CT) around the macular region among subjects with low, moderate and high myopia.

METHODS

20 myopic subjects (n = 40 eyes) without other identified pathologies participated in this study: 20 eyes of ≤ 3 diopters (D) (low myopic), 10 eyes between -3 and -6D (moderate myopic), and 10 eyes of ≥ 6D (high myopic). The mean age of subjects was 30.2 years (± 7.6 years; range, 24 to 46 years). A 1050 nm spectral-domain optical coherence tomography (SD-OCT) system, operating at 120 kHz imaging rate, was used in this study to simultaneously capture 3D anatomical images of the choroid and measure intraocular length (IOL) in the subject. The 3D OCT images of the choroid were segmented into superior, inferior, nasal and temporal quadrants, from which the CT was measured, representing radial distance between the outer retinal pigment epithelium (RPE) layer and inner scleral border. Measurements were made within concentric regions centered at fovea centralis, extended to 5 mm away from fovea at 1 mm intervals in the nasal and temporal directions. The measured IOL was the distance from the anterior cornea surface to the RPE in alignment along the optical axis of the eye. Statistical analysis was performed to evaluate CT at each geographic region and observe the relationship between CT and the degree of myopia.

RESULTS

For low myopic eyes, the IOL was measured at 24.619 ± 0.016 mm. The CT (273.85 ± 49.01 µm) was greatest under fovea as is in the case of healthy eyes. Peripheral to the fovea, the mean CT decreased rapidly along the nasal direction, reaching a minimum of 180.65 ± 58.25 µm at 5 mm away from the fovea. There was less of a change in thickness from the fovea in the temporal direction reaching a minimum of 234.25 ± 42.27 µm. In contrast to the low myopic eyes, for moderate and high myopic eyes, CTs were thickest in temporal region (where CT = 194.94 ± 27.28 and 163 ± 34.89 µm, respectively). Like the low myopic eyes, moderate and high myopic eyes had thinnest CTs in the nasal region (where CT = 100.84 ± 16.75 and 86.64 ± 42.6 µm, respectively). High myopic eyes had the longest mean IOL (25.983 ± 0.021 mm), while the IOL of moderate myopia was 25.413 ± 0.022 mm (**p < 0.001). The CT reduction rate was calculated at 31.28 µm/D (diopter) from low to moderate myopia, whilst it is 13.49 µm/D from moderate to high myopia. The similar tendency was found for the IOL reduction rate in our study: 0.265 mm/D from low to moderate myopia, and 0.137 mm/D from moderate to high myopia.

CONCLUSION

The CT decreases and the IOL increases gradually with the increase of myopic condition. The current results support the theory that choroidal abnormality may play an important role in the pathogenesis of myopic degeneration.

The Charles F. Prentice Award Lecture 2014: A 50-Year Research Journey: Giants and Great Collaborators

This article, an edited version of the 2014 Charles F. Prentice Medal presentation, recounts my 50-year journey in research, from graduation in 1965 to PhD to 2015. The most important lessons I have learned are that great people, "Giants" as I call them, are generous of spirit, creative, insightful, sharing, and caring, and second, that collaboration is really the only way to do what I want to get done. I have been very fortunate to have worked with many outstanding people. As someone said to me at the Prentice Medal presentation, "I don't like you very much but the people you work with are wonderful."My journey started with a PhD investigation into seeing if orthokeratology could control myopia at the City University London in 1966. It then moved to Australia where all aspects of contact lenses were researched to try to make contact lenses safer and more effective by understanding the cornea and anterior eye systems. That journey has now turned to making contact lenses the best they can be to slow the progress of myopia. An extremely high proportion of people who are involved with global eye care initiatives and ambitious projects to develop treatments and interventions for the major vision problems impacting the world are a joy to work with. Evidence-based systems for delivering vision to the more than 600 million people globally that are blind or vision impaired because of uncorrected refractive error have involved amazing people and collaborations. This article pays tribute to the generosity and humanity of my family and the Giants in and outside the field, and many more not so well known, and the people I work with, who have punctuated and greatly enriched this journey and made many of the scientific advances documented here possible.

Concise Review: Using Stem Cells to Prevent the Progression of Myopia-A Concept

The prevalence of myopia has increased in modern society due to the educational load of children. This condition is growing rapidly, especially in Asian countries where it has already reached a pandemic level. Typically, the younger the child's age at the onset of myopia, the more rapidly the condition will progress and the greater the likelihood that it will develop the known sight-threatening complications of high myopia. This rise in incidence of severe myopia has contributed to an increased frequency of eye diseases in adulthood, which often complicate therapeutic procedures. Currently, no treatment is available to prevent myopia progression. Stem cell therapy can potentially address two components of myopia. Regardless of the exact etiology, myopia is always associated with scleral weakness. In this context, a strategy aimed at scleral reinforcement by transplanting connective tissue-supportive mesenchymal stem cells is an attractive approach that could yield effective and universal therapy. Sunlight exposure appears to have a protective effect against myopia. It is postulated that this effect is mediated via local ocular production of dopamine. With a variety of dopamine-producing cells already available for the treatment of Parkinson's disease, stem cells engineered for dopamine production could be used for the treatment of myopia. In this review, we further explore these concepts and present evidence from the literature to support the use of stem cell therapy for the treatment of myopia.

Prevalence of refractive error in Europe: the European Eye Epidemiology (E(3)) Consortium

To estimate the prevalence of refractive error in adults across Europe. Refractive data (mean spherical equivalent) collected between 1990 and 2013 from fifteen population-based cohort and cross-sectional studies of the European Eye Epidemiology (E(3)) Consortium were combined in a random effects meta-analysis stratified by 5-year age intervals and gender. Participants were excluded if they were identified as having had cataract surgery, retinal detachment, refractive surgery or other factors that might influence refraction. Estimates of refractive error prevalence were obtained including the following classifications: myopia ≤-0.75 diopters (D), high myopia ≤-6D, hyperopia ≥1D and astigmatism ≥1D. Meta-analysis of refractive error was performed for 61,946 individuals from fifteen studies with median age ranging from 44 to 81 and minimal ethnic variation (98 % European ancestry). The age-standardised prevalences (using the 2010 European Standard Population, limited to those ≥25 and <90 years old) were: myopia 30.6 % [95 % confidence interval (CI) 30.4-30.9], high myopia 2.7 % (95 % CI 2.69-2.73), hyperopia 25.2 % (95 % CI 25.0-25.4) and astigmatism 23.9 % (95 % CI 23.7-24.1). Age-specific estimates revealed a high prevalence of myopia in younger participants [47.2 % (CI 41.8-52.5) in 25-29 years-olds]. Refractive error affects just over a half of European adults. The greatest burden of refractive error is due to myopia, with high prevalence rates in young adults. Using the 2010 European population estimates, we estimate there are 227.2 million people with myopia across Europe.

Influence of ocular wavefront aberrations on axial length elongation in myopic children treated with overnight orthokeratology

PURPOSE

To determine ocular optical parameters that affect axial length elongation in myopic children undergoing overnight orthokeratology.

DESIGN

Prospective, noncomparative study.

PARTICIPANTS

Fifty-nine subjects who met the inclusion criteria were enrolled in this study.

METHODS

Axial length and ocular wavefront aberration were assessed before and 1 year after the start of orthokeratology. Corneal topography was performed, and then corneal multifocality was calculated for a 4-mm pupil. After evaluating simple correlations between axial elongation and optical parameters, multiple linear regression analysis was performed to identify explanatory variables with a statistically significant contribution to axial elongation.

MAIN OUTCOME MEASURES

Axial length and ocular wavefront aberration before and 1 year after the start of orthokeratology.

RESULTS

Fifty-five subjects completed the 1-year follow-up examinations. At baseline, their age ranged from 7.2 to 12.0 years. The manifest spherical equivalent refractive error ranged from -3.50 to -0.75 diopters. The mean axial length significantly increased from 24.20 mm at baseline to 24.43 mm 1 year after treatment. The axial elongation showed significant simple correlations with the change in C2(0), change in second-order aberration, change in coma-like aberration, change in spherical-like aberration, change in total higher-order aberrations, change in corneal multifocality, baseline age, and baseline spherical equivalent refractive error, but not C4(0). Multiple linear regression analysis showed that the change in coma-like aberration was the most relevant variable.

CONCLUSIONS

Asymmetric corneal shapes, rather than concentric and radially symmetric shapes, have a considerable effect on retardation of axial elongation, suggesting that the inhibitory effect of orthokeratology on myopia progression is caused by mechanisms other than the reduction in peripheral hyperopic defocus.