Recovery From Form-Deprivation Myopia in Chicks Is Dependent Upon the Fullness and Correlated Color Temperature of the Light Spectrum.

Purpose: The purpose of this study was to evaluate the impact of full-spectrum light-emitting diodes mimicking sunlight (Sunlike LEDs) on ocular growth and refractive error development in a chicken model of myopia. Methods: One-day old chicks (n = 39) were distributed into 3 groups and raised for 28 days in isoluminant (approximately 285 lux) fluorescent (n = 18, [FL-4000], correlated color temperature [CCT] = 4000 K) or Sunlike LED (n = 12, [SL-4000], CCT = 4000 K; n = 9, [SL-6500], CCT = 6500 K) white lighting environments. Form-deprivation myopia was induced monocularly from day 1 post-hatching (D1) until D14. On D14, form deprivation was halted and the recovery of form-deprived (FD) eyes was monitored until D28. Axial length (AL), refraction, choroidal thickness, and anterior chamber depth were measured in vivo on D1, D7, D14, D22, and D28. Differences in outcome measures between eyes and groups were compared using 2-way repeated-measures ANOVA. Results: AL and myopic refraction of FD eyes increased similarly among groups during form-deprivation. FD eyes of animals raised under SL-4000 (D22: P < 0.001 and D28: P < 0.001) and SL-6500 (D22: P = 0.006 and D28: P < 0.001) recovered faster from axial elongation compared with animals raised under FL-4000. The refractive status of FD eyes reared under SL-6500, not under FL-4000 or SL-4000, was similar to control eyes on D28 (P > 0.05). However, SL-4000 and SL-6500 exhibited similar refraction on D28 than FL-4000 (P > 0.05). Choroidal thickness was significantly greater in FD eyes of chickens raised under SL-6500 than in animals raised under FL-4000 (P = 0.03). Conclusions: Compared to fluorescent light, moderate intensities of full-spectrum Sunlike LEDs can accelerate recovery from form-deprivation myopia in chickens, potentially through a change in the choroid-mediated pathway.

Intraocular Pressure and Its Relation to Ocular Geometry: Results From the Gutenberg Health Study.

Purpose: The purpose of this study was to investigate the association between intraocular pressure (IOP) and ocular geometry. Methods: The Gutenberg Health Study is a population-based cohort study in Mainz, Germany. Study participants underwent a comprehensive ophthalmologic examination including noncontact tonometry, objective refraction, optical biometry, and Scheimpflug imaging of the anterior segment at the first 5-year follow-up examination (in 2012-2017). Multivariable linear regression analysis was carried out to determine associations of IOP and geometric parameter of the human phakic eye, namely central corneal thickness (CCT), corneal curvature, anterior chamber depth (ACD), lens thickness, and axial length. In addition, the relationship of IOP and the anterior chamber angle (ACA) width was analyzed. Results: There were 6640 participants with phakia (age 57.3 ± 10.2 years, 49.1% women) that were included in this cross-sectional analysis. Mean IOP was 14.8 ± 2.9 mm Hg in the right eyes and 14.9 ± 2.9 mm Hg in the left eyes. IOP increased with higher CCT, greater posterior segment length, higher age (all P < 0.001), thicker lens (P = 0.003), and female sex (P = 0.05), whereas the ACD was not associated with higher IOP. The IOP increased with a narrower ACA in univariable analysis (P < 0.001), but not in adjusted analysis in subjects with an open angle. Conclusions: IOP values are related to ocular geometry, as shown in this population-based study on Caucasian subjects. Thus, knowledge of the architecture of the eye is an important factor when measuring IOP. Longitudinal evaluation will analyze whether some of these parameters are also risk factors for the development of glaucoma.

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

High myopia is among the most common causes of vision impairment, and it is mainly characterized by abnormal elongation of the axial length, leading to pathologic changes in the ocular structures. Owing to the close relationship between high myopia and glaucoma, the association between intraocular pressure (IOP) and high myopia progression has garnered attention. However, whether lowering IOP can retard the progression of high myopia is unclear. On reviewing previous studies, we suggest that lowering IOP plays a role in progressive axial length elongation in high myopia, particularly in pathologic myopia, wherein the sclera is more remodeled. Based on the responses of the ocular layers, we further proposed the potential mechanisms. For the sclera, lowering the IOP could inhibit the activation of scleral fibroblasts and then reduce scleral remodeling, and a decrease in the scleral distending force would retard the ocular expansion like a balloon. For the choroid, lowering IOP results in an increase in choroidal blood perfusion, thereby reducing scleral hypoxia and slowing down scleral remodeling. The final effect of these pathways is slowing axial elongation and the development of scleral staphyloma. Further animal and clinical studies regarding high myopia with varied degree of IOP and the changes of choroid and sclera during IOP fluctuation in high myopia are needed to verify the role of IOP in the pathogenesis and progression of high myopia. It is hoped that this may lead to the development of a prospective treatment option to prevent and control high myopia progression.

Differences in Retinal and Choroidal Vasculature and Perfusion Related to Axial Length in Pediatric Anisomyopes.

Purpose: The purpose of this study was to evaluate the interocular differences in choroidal vasculature, choriocapillaris perfusion, and retinal microvascular network, and to explore their associations with interocular asymmetry in axial lengths (ALs) in children with anisomyopia. Methods: Refractive error, AL, and other biometric parameters were measured in 70 children with anisomyopia. Using optical coherence tomography (OCT) and OCT-angiography, we measured the submacular choroidal thickness (ChT), total choroidal area (TCA), luminal area (LA), stromal area (SA), choroidal vascularity index (CVI), choriocapillaris flow deficit (CcFD), retinal vessel density (VD), and foveal avascular zone (FAZ) area. Results: The mean interocular differences in spherical equivalent refraction and AL were -2.26 ± 0.94 diopters and 0.95 ± 0.46 mm, respectively. Submacular ChT, TCA, LA, SA, and CVI were all significantly lower in the more myopic (longer AL) eyes than in the less myopic (shorter AL) fellow eyes. In eyes with longer ALs, both the CcFD and FAZ areas were significantly greater, whereas the superficial and deep retinal VDs were significantly less. After adjusting for corneal power and intraocular pressure, interocular differences in LA (ß = -0.774), SA (ß = -0.991), and CcFD (ß = 0.040) were significantly associated with interocular asymmetry in AL (all P < 0.05). Conclusions: In pediatric anisomyopes, eyes with longer ALs tended to have lower choroidal vascularity and choriocapillaris perfusion than the contralateral eyes with shorter ALs. Longitudinal investigations would be useful follow-ups to test for a causal role of choroidal circulation in human myopia.

The Association between Fourier Parameters and Clinical Parameters in Myopic Children Undergoing Orthokeratology.

Purpose: To explore how Fourier parameters are associated with axial length growth (ALG) and clinical parameters in children who underwent orthokeratology.Materials and Methods: A total of 267 children received orthokeratology. Baseline cycloplegic autorefraction was performed. Axial length was measured at baseline and one year after the lens dispatch, and the difference was defined as ALG. Corneal topography was performed at the same two visits. Central treatment zone (CTZ) was identified from the difference between the two tangential maps, and its center distance to corneal center was defined as decentration. A relative refractive corneal power (RCRP) map was derived by subtracting the center value from every point on the one-year axial map. It was decomposed into 3 Fourier components: a mean (F0), a single-cycle sinewave (F1), and a double-cycle sinewave (F2). Linear regressions were used to reveal the association between ALG and these parameters.Results: At baseline, the age was 10.18 ± 1.48 year, spherical equivalent (SE) was - 3.10 ± 1.15D, astigmatism was 1.17 ± 0.58D, and axial length was 24.69 ± 0.81 mm. The mean ALG was 0.181 ± 0.22 mm. In multiple regression, ALG was negatively associated with F1 (p < .001), not F0 and F2. Amplitude-wise, F0 and F1 were correlated with decentration (p < .01) and SE (p < .01), and F2 was associated with astigmatism (p < .001). Direction-wise, F1 was correlated with decentration (p < .001) and F2 was associated with astigmatism (p < .001).Conclusions: Among Fourier parameters, F0 and F1 were negatively associated with ALG in myopic children undergoing orthokeratology. Their associations to SE and CTZ decentration may partially explain the effect on ALG retardation.

Association of Aberrant Posterior Vitreous Detachment and Pathologic Tractional Forces With Myopic Macular Degeneration.

Purpose: The purpose of this study was to assess whether the tractional elements of pathologic myopia (PM; e.g. myopic traction maculopathy [MTM], posterior staphyloma [PS], and aberrant posterior vitreous detachment [PVD]) are associated with myopic macular degeneration (MMD) independent of age and axial length, among highly myopic (HM) eyes. Methods: One hundred twenty-nine individuals with 239 HM eyes from the Myopic and Pathologic Eyes in Singapore (MyoPES) cohort underwent ocular biometry, fundus photography, swept-source optical coherence tomography, and ocular B-scan ultrasound. Images were analyzed for PVD grade, and presence of MTM, PS, and MMD. The χ² test was done to determine the difference in prevalence of MMD between eyes with and without PVD, PS, and MTM. Multivariate probit regression analyses were performed to ascertain the relationship between the potential predictors (PVD, PS, and MTM) and outcome variable (MMD), after accounting for possible confounders (e.g. age and axial length). Marginal effects were reported. Results: Controlling for potential confounders, eyes with MTM have a 29.92 percentage point higher likelihood of having MMD (P = 0.003), and eyes with PS have a 25.72 percentage point higher likelihood of having MMD (P = 0.002). The likelihood of MMD increases by 10.61 percentage points per 1 mm increase in axial length (P < 0.001). Subanalysis revealed that eyes with incomplete PVD have a 22.54 percentage point higher likelihood of having MMD than eyes with early PVD (P = 0.04). Conclusions: Our study demonstrated an association between tractional (MTM, PS, and persistently incomplete PVD) and degenerative elements of PM independent of age and axial length. These data provide further insights into the pathogenesis of MMD.

Axial length targets for myopia control.

PURPOSE: Both emmetropic and myopic eyes elongate throughout childhood. The goals of this study were to compare axial elongation among untreated progressing myopes, progressing myopes treated with a myopia control contact lens and emmetropes, in order to place axial elongation in the context of normal eye growth in emmetropic children, and to consider whether normal physiological eye growth places limits on what might be achieved with myopia control. METHODS: Axial elongation data were taken from the 3-year randomised clinical trial of a myopia control dual-focus (MiSight® 1 day) contact lens. These were compared with data for myopic and emmetropic children in two large cohort studies: the Orinda Longitudinal Study of Myopia (OLSM) and the Singapore Cohort Study of the Risk Factors for Myopia (SCORM). Each study's published equations were used to calculate annual axial elongation. Four virtual cohorts-myopic and emmetropic for each model-were created, each with the same age distribution as the MiSight clinical trial subjects and the predicted cumulative elongation calculated at years 1, 2 and 3 for myopes and emmetropes using both the OLSM and SCORM models. RESULTS: The untreated control myopes in the MiSight clinical trial showed mean axial elongation over 3 years (0.62 mm) similar to the virtual cohorts based on the OLSM (0.70 mm) and SCORM (0.65 mm) models. The predicted 3-year axial elongation for the virtual cohorts of emmetropes was 0.24 mm for both the OLSM and SCORM models-similar to the mean 3-year elongation in MiSight-treated myopes (0.30 mm). CONCLUSIONS: The 3-year elongation in MiSight-treated myopes approached that of virtual cohorts of emmetropes with the same age distribution. It is hypothesised that myopic axial elongation is superimposed on an underlying physiological axial elongation observed in emmetropic eyes, which reflects increases in body stature. We speculate that optically based myopia control treatments may minimise the myopic axial elongation but retain the underlying physiological elongation observed in emmetropic eyes.

Ocular biometry in children and adolescents from 4 to 17 years: a cross-sectional study in central Germany.

PURPOSE: To evaluate ocular biometry in a large paediatric population as a function of age and sex in children of European descent. METHODS: Children were examined as part of the LIFE Child Study (Leipzig Research Centre for Civilization Disease), a population-based study in Leipzig, Germany. Altogether, 1907 children, aged from 4 to 17 years, were examined with the Lenstar LS 900. Data from the right eye was analysed for axial length, central corneal thickness, flat and steep corneal radii, aqueous depth, lens thickness and vitreous depth. Wavefront-based autorefraction was employed for analysis. RESULTS: Axial length increased in girls from 21.6 mm (4 years) up to 23.4 mm (17 years); this increase (0.174 mm per year) was statistically significant up to age 14 (23.3 mm). Axial length increased in boys from 22.2 mm (4 years) up to 23.9 mm (17 years); this increase (0.178 mm per year) was statistically significant up to age 10 (23.3 mm). No change was observed for central corneal thickness (average: girls 550 µm; boys 554 µm). Corneal curvature in girls was somewhat flatter at age 4 (7.70 mm) compared to age 10 (7.78 mm), whereas it was constant in boys (7.89 mm). Aqueous depth at age 4 was 2.73 mm for girls and 2.86 mm for boys, with the same rate of increase per year (girls: 0.046 mm; boys: 0.047 mm) from age 4 to 10. At age 17, aqueous depth was 3.06 mm in girls and 3.20 mm in boys. Lens thickness was reduced from age 4 (3.75 mm) to age 10 (3.47 mm) in girls and from age 4 (3.73 mm) to age 10 (3.44 mm) in boys, with the same rate of decrease per year of 0.046 and 0.047 mm, respectively. At age 17, lens thickness was 3.52 mm in girls and 3.50 mm in boys. Vitreous depth at age 4 was 14.51 mm for girls and 15.08 mm for boys; with 0.156 mm (girls) or 0.140 mm (boys) increase per year until age 14 (girls: 16.08 mm; boys: 16.48 mm). At age 17, vitreous depth was 16.29 mm in girls and 16.62 mm in boys. CONCLUSIONS: Eye growth (axial length) in girls showed a lag of about four years compared to boys. Aqueous depth increase matches the lens thickness decrease from ages 4 to 10 years in girls and boys. Lens thickness minimum is reached at 11 years in girls and at 12 years in boys. All dimensions of the optical ocular components are closely correlated with axial length. These data may serve as normative values for the assessment of eye growth in central European children and will provide a basis for monitoring refractive error development.

Longitudinal analysis of axial length growth in a German cohort of healthy children and adolescents.

PURPOSE: To generate continuous growth curves for axial length (AL) in German children. We hypothesise that percentile curves of AL can be used as a predictive measure of myopia. METHODS: In this longitudinal and cross-sectional LIFE Child Study, children's non-cycloplegic refraction data was collected using the Zeiss i.Profiler plus while AL was measured using the Haag-Streit Lenstar. Reference growth curves were estimated as a continuous non-parametric function of age. RESULTS: Data from 4511 visits of 1965 participants (1021 boys and 944 girls) between 3 and 18 years of age were analysed. For all ages and percentiles, the estimated AL was higher in boys than girls. AL differences between boys and girls were most pronounced in the 98th percentile at 3 years of age, being 0.93 mm longer eyes in boys. This difference decreased to 0.21 mm at 18 years of age. While the lower percentiles of AL reach their final value around age 13, the 50th percentile was still increasing by 0.05 mm per year until the end of the observation period. While, in general, children with longer eyes are more likely to develop myopia, this relationship is weaker between the ages of 5 and 8. CONCLUSION: The LIFE Child Study data provides European AL data. In both Germany and China, AL has comparable growth rates when the baseline ALs are compared as percentiles. Thus, percentile curves of AL can be used as a predictive measure for the likelihood of developing as well as the progression of myopia.

Emmetropic, But Not Myopic Human Eyes Distinguish Positive Defocus From Calculated Blur.

Purpose: Defocus blur imposed by positive lenses can induce hyperopia, whereas blur imposed by diffusers induces deprivation myopia. It is unclear whether the retina can distinguish between both conditions when the magnitude of blur is matched. Methods: Ten emmetropic (average 0.0 ± 0.3 diopters [D]) and 10 subjects with myopia (-2.7 ± 0.9 D; 24 ± 4 years) watched a movie on a large screen (65 inches at 2 meters (m) distance. The movie was presented either unfiltered ("control"), with calculated low-pass filtering equivalent to a defocus of 2.5 D, or with binocular real optical defocus of +2.5 D. Spatial filtering was done in real-time by software written in Visual C++. Axial length was followed with the Lenstar LS-900 with autopositioning system. Results: Watching unfiltered movies ("control") caused no changes in axial length. In emmetropes, watching movies with calculated defocus caused axial eye elongation (+9.8 ± 7.6 µm) while watching movies with real positive defocus caused shorter eyes (-8.8 ± 9.2 µm; difference between both P < 0.0001). In addition, in myopes, calculated defocus caused longer eyes (+8.4 ± 9.0 µm, P = 0.001). Strikingly, myopic eyes became also longer with positive defocus (+9.1 ± 11.2 µm, P = 0.02). The difference between emmetropic and myopic eyes was highly significant (-8.8 ± 9.2 µm vs. +9.1 ± 11.2 µm, respectively, P = 0.001). Conclusions: (1) In emmetropic human subjects, the retina is able to distinguish between real positive defocus and calculated defocus even when the modulation transfer function was matched, (2) in myopic eyes, the retina no longer distinguishes between both conditions because the eyes became longer in both cases. Results suggest that the retina in a myopic eye has reduced ability to detect positive defocus.

Age Effect on Treatment Responses to 0.05%, 0.025%, and 0.01% Atropine: Low-Concentration Atropine for Myopia Progression Study.

PURPOSE: To investigate the effect of age at treatment and other factors on treatment response to atropine in the Low-Concentration Atropine for Myopia Progression (LAMP) Study. DESIGN: Secondary analysis from a randomized trial. PARTICIPANTS: Three hundred fifty children aged 4 to 12 years who originally were assigned to receive 0.05%, 0.025%, or 0.01% atropine or placebo once daily, and who completed 2 years of the LAMP Study, were included. In the second year, the placebo group was switched to the 0.05% atropine group. METHODS: Potential predictive factors for change in spherical equivalent (SE) and axial length (AL) over 2 years were evaluated by generalized estimating equations in each treatment group. Evaluated factors included age at treatment, gender, baseline refraction, parental myopia, time outdoors, diopter hours of near work, and treatment compliance. Estimated mean values and 95% confidence intervals (CIs) of change in SE and AL over 2 years also were generated. MAIN OUTCOME MEASURES: Factors associated with SE change and AL change over 2 years were the primary outcome measures. Associated factors during the first year were secondary outcome measures. RESULTS: In 0.05%, 0.025%, and 0.01% atropine groups, younger age was the only factor associated with SE progression (coefficient of 0.14, 0.15, and 0.20, respectively) and AL elongation (coefficient of -0.10, -0.11, and -0.12, respectively) over 2 years; the younger the age, the poorer the response. At each year of age from 4 to 12 years across the treatment groups, higher-concentration atropine showed a better treatment response, following a concentration-dependent effect (Ptrend <0.05 for each age group). In addition, the mean SE progression in 6-year-old children receiving 0.05% atropine (-0.90 diopter [D]; 95% CI, -0.99 to -0.82) was similar to that of 8-year-old children receiving 0.025% atropine (-0.89 D; 95% CI, -0.94 to -0.83) and 10-year-old children receiving 0.01% atropine (-0.92 D; 95% CI, -0.99 to -0.85). All concentrations were well tolerated in all age groups. CONCLUSIONS: Younger age is associated with poor treatment response to low-concentration atropine at 0.05%, 0.025%, and 0.01%. Among concentrations studied, younger children required the highest 0.05% concentration to achieve similar reduction in myopic progression as older children receiving lower concentrations.

The Epidemiological and Clinical Findings from the Latvian Registry of Primary Congenital Glaucoma and Evaluation of Prognostic Factors.

Background and objectives: primary congenital glaucoma (PCG) is a rare, potentially blinding disease that affects children worldwide. The aim of the study was to describe the epidemiological and clinical characteristics, outcomes for newly diagnosed patients with PCG, as well as evaluate the prognostic factors that are related to the outcomes. Materials and Methods: a retrospective cohort study was conducted at a tertiary referral centre among patients diagnosed with PCG. Evaluation of the clinical data was performed preoperatively at three, six, and 12 months after the surgery and at the last follow-up. Results: during the 15 years of follow-ups, 24 eyes of 18 patients were diagnosed with PCG. Unilateral and bilateral PCG constituted 50% of cases each. A slight male predominance was observed (55.6% vs. 44.4%), with a relative risk of 1.3. The incidence of PCG was 1:19,033 live births. The mean age of the patients at the time of diagnosis was 10.1 ± 10.0 months, with a diagnostic delay of 2.0 ± 1.9 months. Furthermore, 75% of patients indicated an enlargement of an eyeball, followed by excessive tearing (58.3%) and corneal opacity (41.7%). After 85.9 ± 51.2 months, the mean intraocular pressure (IOP) value was 14.6 ± 4.9 mmHg. Surgical treatment provided sufficient IOP control in 75% of PCG cases at the last follow-up visit. The only prognostic factor that was related to the outcome of IOP control that was statistically significant was axial length at the time of diagnosis. Conclusions: the incidence of PCG in Latvia was 5.3 patients per 100,000 live births. PCG was more common among males than females with a relative risk of 1.3. The enlargement of an eyeball was the leading clinical sign.

Rebound Effect in the Misight Assessment Study Spain (Mass).

PURPOSE: To investigate whether cessation of MiSight contact lens (CLs) wear for myopia control produces rebound effect. MATERIAL AND METHODS: This study recruited participants who had just completed the MASS Study, a two-year randomized clinical trial designed to assess the efficacy of MiSight® CLs versus distance single vision (SV) spectacles in myopic children. To assess the rebound effect, axial length progression was taken into account in those children that continued one more year of follow-up. At this visit, children were divided into three groups: MiSight-C group, in which children from the original study group continued MiSight CLs wear for the duration of the study; MiSight-D group, in which children from the original study group discontinued MiSight CLs wear in the last year; and SV-C group, in which children from the original control group continued wearing single-vision spectacles for the duration of the study. The last group was considered as the control group. RESULTS: Of the 74 children who completed the MASS study, 55 children completed the 1-year follow-up and were included in the analysis. Thirteen children were included in the MiSight-C group, 18 in the MiSight-D group, and 24 in the Single Vision-C group. Axial length and myopia progression in the last year were 0.15± 0.11 mm, 0.22± 0.11 mm, 0.21± 0.10 mm and -0.37±0.44D, -0.46±0.39D and -0.55±0.45D for the three groups, respectively. No significant differences in axial elongation and myopia progression were found among the three groups of participants. CONCLUSIONS: Over a one-year period, neither myopia progression nor eye growth was faster for the subjects who discontinued MiSight contact lens wear compared to those who continued to wear MiSight contact lenses or those who continued to wear single-vision spectacles, indicating no rebound effect with MiSight contact lenses for 2 years.ClinicalTrials.gov Identifier: NCT01917110.

Association between ocular biometrical parameters and diabetic retinopathy in Chinese adults with type 2 diabetes mellitus.

PURPOSE: The influence of myopia and ocular biometry parameters on diabetic retinopathy (DR) needs further clarification. We aimed to investigate the association between ocular biometrical parameters and DR in Chinese people with diabetes mellitus (DM) without any ocular intervention. METHODS: This cross-sectional study recruited type 2 DM patients with no history of ocular treatment in Guangzhou, China. The ocular biometrical parameters were obtained by Lenstar (LS900, Haag-Streit AG, Koeniz, Switzerland), including corneal diameter, central corneal thickness (CCT), corneal curvature (CC), anterior chamber depth (ACD), lens thickness (LT) and axial length (AL). The lens power and axial length-to-cornea radius ratio (AL/CR ratio) were calculated. Spherical equivalent (SE) was determined by auto-refraction after pupil dilation. Multivariate logistic regression analyses were performed to explore the associations of ocular biometry with any DR and vision threatening DR (VTDR). RESULTS: A total of 1838 patients were included in the final analysis, involving 1455 (79.2%) patients without DR and 383(20.8%) patients with DR. After adjusting confounding factors, any DR was independently associated with AL (odds ratio (OR) 0.84 per 1 mm increase, 95% confidence interval (CI): 0.74, 0.94) and AL/CR ratio (OR 0.26 per 1 increase, 95%CI: 0.10, 0.70). Similarly, the presence of VTDR was independently related to AL (OR 0.67 per 1 mm increase, 95%CI: 0.54, 0.85) and AL/CR ratio (OR 0.04 per 1 increase, 95%CI: 0.01, 0.25). The lens power may not be significantly correlated with presence of any DR or VTDR. The CC, corneal diameter and refractive status were not significantly correlated with presence of DR or VTDR. CONCLUSION: Longer AL and higher AL/CR ratio may be protective factors against the occurrence and progression of DR. Further longitudinal studies are warranted to verify if refractive status and AL-associated parameters contribute to the occurrence and progression of DR in type 2 DM.

Refractive Errors, Ocular Biometry and Diabetic Retinopathy: A Comprehensive Review.

Purpose: To summarize the association between diabetic retinopathy and refractory status as well as ocular biometric parameters; To review the theories of the protective effect of high myopia against diabetic retinopathy. Methods: A comprehensive literature search on MEDLINE, EMBASE, Web of Science and Scopus databases as well as reference list search, and systematic review of relevant publications.  Results: Myopia may delay the onset and progression of diabetic retinopathy. Increased axial length in myopia is associated with reduced risk of any diabetic retinopathy and vision-threatening diabetic retinopathy. The possible mechanisms for the protective effect of myopia against diabetic retinopathy may include posterior vitreous detachment, change in retinal blood flow and oxygen demand, choroidal thinning and altered cytokine profiles.  Conclusions: High myopia may be a protective factor against the onset and progression of diabetic retinopathy. Further studies about the mechanisms of how myopia, axial length and ocular biometrics influence the onset and progression of DR are needed.

Long-term longitudinal changes in axial length in the Caucasian myopic and hyperopic population with a phakic intraocular lens.

PURPOSE: To determine the long-term longitudinal axial length changes in myopic and hyperopic adults with an iris-fixated phakic intraocular lens (pIOL). METHODS: The medical records of patients aged ≥18 years with myopia or hyperopia who were treated with pIOL implantation between 1996 and 2011 for refractive correction with a minimum follow-up of 5 years after pIOL implantation were analyzed. The main outcome measure was change in ocular axial length over time. RESULTS: 149 eyes of 149 myopic patients and 27 hyperopic eyes of 27 patients were included in this study. Mean patient age was 37.1 ± 10.4 years (35% male) in the myopic group and 39.4 ± 9.4 years (4% male) in the hyperopic group. The eyes of the myopic patients showed a significant mean increase in axial length of 0.45 ± 0.61 mm after a mean follow-up time of 144 ± 38 months (p < 0.001). In 26 eyes (17%), the axial length had increased by ≥1 mm. The mean annual axial length increase was 0.04 ± 0.06 mm. Axial elongation was associated with a higher degree of myopia (p < 0.001) and younger age (p = 0.02). The eyes of the hyperopic patients showed no change in axial length over time. CONCLUSIONS: Myopic eyes corrected with an iris-fixated pIOL show continuous increase in axial length at an adult age. Although this study is limited to subjects with a pIOL, this is the first time myopization in Caucasian adults has been reported in a large long-term longitudinal study.

Temporal color contrast guides emmetropization in chick.

As a result of longitudinal chromatic aberration (LCA), longer wavelengths are blurred when shorter wavelengths are in focus, and vice versa. As a result, LCA affects the color and temporal aspects of the retinal image with hyperopic defocus. In this experiment, we investigated how the sensitivity to temporal color contrast affects emmetropization. Ten-day-old chicks were exposed for three days to sinusoidal color modulation. The modulation was either blue/yellow flicker (BY) (n = 57) or red/green flicker (RG) (n = 60) simulating hyperopic defocus with and without a blue light component. The color contrasts tested were 0.1, 0.2, 0.3, 0.4, 0.6, and 0.8 Michelson contrast. The mean illuminance of all stimuli was 680 lux. Temporal modulation was either of a high (10 Hz) or low (0.2 Hz) temporal frequency. To test the role of short- and double-cone stimulation, an additional condition silenced these cones in RG_0.4 (D-) and was compared with RG_0.4 (D+) (n = 14). Changes in ocular components and refractive error were measured using Lenstar and a photorefractometer. With high temporal frequency BY representing an in-focus condition for shorter-wavelengths, we found that high temporal frequency BY contrast was positively correlated with vitreous expansion (R2 = 0.87, p < 0.01), expanding the vitreous to compensate for hyperopic defocus. This expansion was offset by low temporal frequency RG, which represented blurred longer wavelengths. The reduction in vitreous expansion in RG_0.4, was enhanced in D+ compared to D- (p < 0.001), indicating a role for short- and/or double-cones. With high temporal frequency RG representing an in-focus condition for longer-wavelengths, we found that high temporal frequency RG contrast was also positively correlated with a linear increase in vitreous chamber depth (R2 = 0.84, p < 0.01) and eye length (R2 = 0.30, p ≤ 0.05), required to compensate for hyperopic defocus, but also with RG sensitive choroidal thickening (R2 = 0.18: p < 0.0001). These increases in the vitreous and eye length were enhanced with D+ compared to D- (p = 0.003) showing the role of short- and double-cones in finessing the vitreous response to hyperopic defocus. Overall, the increase in vitreous chamber depth in RG was offset by reduced expansion in BY, indicating sensitivity to the shorter focal length of blue light and wavelength defocus. Predictable changes in cone contrast and temporal frequency of the retinal image that occur with LCA and defocus result in homeostatic control of emmetropization.

Categorisation of myopia progression by change in refractive error and axial elongation and their impact on benefit of myopia control using orthokeratology.

AIMS: To compare the value of pre-treatment axial elongation (AE) and changes in refractive sphere (M change) for predicting the success in orthokeratology (ortho-k), in order to better identify suitable candidates for myopia control. METHODS: This study further analysed the data of 66 subjects receiving 7-month ortho-k treatment, following a 7-month observation period, during which single-vision spectacles were worn. Rate of myopia progression was determined by AE and M change and subjects categorised as slow, moderate, or rapid progressors based on these changes. Outcomes of myopia control, based on the AE reduction after ortho-k, were classified as 'ineffectual', 'clinically insignificant', or 'beneficial'. RESULTS: Of the 20 subjects, initially categorised as slow by AE and, of whom 95% were similarly categorised by M change, none benefitted from ortho-k. In contrast, of the 22 subjects with moderate AE, 77% and 23% displaying slow and moderate M change, respectively, the majority (73%) benefitted from ortho-k lens wear. The 24 subjects with rapid AE were poorly identified by M change, with only 21% correctly categorised. The vast majority of rapid progressors showed significant benefit after ortho-k. CONCLUSION: Progression of AE is a good indicator of subsequent success of ortho-k treatment. Delaying commencement of therapy is prudent for children with slow progression as results indicate that they would be unlikely to benefit from this intervention. As change in refractive error frequently underestimates rapid progression of AE, its value for identifying appropriate candidates for myopia control is poor.

Form-Deprivation and Lens-Induced Myopia Are Similarly Affected by Pharmacological Manipulation of the Dopaminergic System in Chicks.

Purpose: Animal models have demonstrated a link between decreases in retinal dopamine levels and the development of form-deprivation myopia (FDM). However, the consistency of dopamine's role in the other major form of experimental myopia, that of lens-induced myopia (LIM), is less clear, raising the question as to what extent dopamine plays a role in human myopia. Therefore, to better define the role of dopamine in both forms of experimental myopia, we examined how consistent the protection afforded by dopamine and the dopamine agonist 6-amino-5,6,7,8-tetrahydronaphthalene-2,3-diol hydrobromide (ADTN) is between FDM and LIM. Methods: Intravitreal injections of dopamine (0.002, 0.015, 0.150, 1.500 µmol) or ADTN (0.001, 0.010, 0.100, 1.000 µmol) were administered daily to chicks developing FDM or LIM. Axial length and refraction were measured following 4 days of treatment. To determine the receptor subtype by which dopamine and ADTN inhibit FDM and LIM, both compounds were coadministered with either the dopamine D2-like antagonist spiperone (0.005 µmol) or the D1-like antagonist SCH-23390 (0.005 µmol). Results: Intravitreal administration of dopamine or ADTN inhibited the development of FDM (ED50 = 0.003 µmol and ED50 = 0.011 µmol, respectively) and LIM (ED50 = 0.002 µmol and ED50 = 0.010 µmol, respectively) in a dose-dependent manner, with a similar degree of protection observed in both paradigms (P = 0.471 and P = 0.969, respectively). Coadministration with spiperone, but not SCH-23390, inhibited the protective effects of dopamine and ADTN against the development of both FDM (P = 0.214 and P = 0.138, respectively) and LIM (P = 0.116 and P = 0.100, respectively). Conclusions: pharmacological targeting of the retinal dopamine system inhibits FDM and LIM in a similar dose-dependent manner through a D2-like mechanism.