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Concept: Refractive error

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PURPOSE: To investigate the normative data of ocular axial length and its associations in Chinese. METHOD: The population-based Beijing Eye Study 2011 is a cross-sectional study performed in Greater Beijing. The study included 3468 individuals (1963 (56.6%) women) with a mean age of 64.6±9.8 years (range: 50-93 years). A detailed ophthalmic and medical examination was performed. Axial length was measured by optical low-coherence reflectometry. RESULTS: Axial length measurements were available for 3159 (91.1%) study participants. Mean axial length was 23.25±1.14 mm (range: 18.96-30.88 mm). In multivariate analysis, axial length was significantly associated with the systemic parameters of higher age (P<0.001), higher body height (P = 0.003), higher level of education (P<0.001) and urban region of habitation (P<0.001), and with the ocular parameters of thicker central cornea (P = 0.001), higher corneal curvature radius (P<0.001), deeper anterior chamber (P<0.001), thicker lens (P<0.001), more myopic refractive error (P<0.001), larger pupil diameter (P = 0.018), and higher best corrected visual acuity (P<0.001). It was additionally and negatively associated with the lens vault (P<0.001). In highly myopic eyes, axial length was significantly associated with lower level of education (P = 0.008), more myopic refractive error (P<0.001), and lower best corrected visual acuity (P = 0.034). CONCLUSIONS: Mean ocular axial length in the older adult population of Greater Beijing (23.25±1.14 mm) was similar to the value measured in other urban populations and was higher than in a rural Central Indian population. The association between axial length and older age may potentially be associated with a survival artifact. The association between axial length and body height agrees with the general association between anthropomorphic measures and eye globe size. The association with the level of education and urban region of habitation confirms with previous studies. In contrast in highly myopic eyes, axial length was negatively associated with educational level and best corrected visual acuity.

Concepts: Eye, Visual acuity, Cornea, Myopia, Contact lens, Refractive error, Length, Pupil

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Background: Refractive errors (RE) are the most common cause of avoidable visual impairment in children. But benefits of visual aids, which are means for correcting RE, depend on the compliance of visual aids by end users. Aim: To study the compliance of spectacle wear among rural school children in Pune district as part of the sarva siksha abhiyan (education for all scheme) after 6 - 12 months of providing free spectacles. Settings and Design: Cross-sectional follow-up study of rural secondary school children in western India. Materials and Methods: The students were examined by a team of optometrists who collected the demographic details, observed if the child was wearing the spectacles, and performed an ocular examination. The students were asked to give reasons for non-wear in a closed-ended questionnaire. Statistical Analysis: Chi-square test and multiple logistic regression used for data analysis. Results: Of the 2312 students who were dispensed spectacles in 2009, 1018 were re-examined in 2010. 523 students (51.4%) were female, the mean age was 12.1 years 300 (29.5%) were wearing their spectacles, 492 (68.5%) students claimed to have them at home while 211 (29.4%) reported not having them at all. Compliance of spectacle wear was positively associated to the magnitude of refractive error (P < 0.001), father's education (P = 0.016), female sex (P = 0.029) and negatively associated to the visual acuity of the better eye (P < 0.001) and area of residence (P < 0.0001). Of those that were examined and found to be myopic (N = 499), 220 (44%) wore their spectacles to examination. Factors associated with compliance to spectacle usage in the myopic population included increasing refractive error (P < 0.001), worsening visual acuity (P < 0.001), and higher academic performance (P < 0.001). The causes for not wearing spectacles were 'lost spectacles' 67(9.3%), 'broken spectacles' 125 (17.4%), 'forgot spectacles at home' 117 (16.3%), 'uses spectacles sometimes' 109 (15.2%), 'teased about spectacles' 142 (19.8%) and 'do not like the spectacles' 86 (12%). Conclusion: Spectacle compliance was poor amongst school children in rural Pune; many having significant vision loss as a result.

Concepts: Regression analysis, Refraction, Visual acuity, Ophthalmology, Myopia, Refractive error, Visual impairment, Glasses

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We present an overview of currently available toric intraocular lenses (IOLs) and multifocal toric IOLs. Relevant patient selection criteria, IOL calculation issues, and surgical techniques for IOL implantation are discussed. Clinical outcomes including uncorrected visual acuity, residual refractive astigmatism, and spectacle independency, which have been reported for both toric IOLs and multifocal toric IOLs, are reviewed. The incidence of misalignment, the most important complication of toric IOLs, is determined. Finally, future developments in the field of toric IOLs are discussed. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Concepts: Ophthalmology, Lens, Presbyopia, Contact lens, Refractive error, Intraocular lens, Cataract, Toric lens

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To examine the prevalence of refractive errors and prevalence and causes of vision loss among preschool and school children in East China.

Concepts: Refraction, Vision, Visual perception, Visual acuity, Ophthalmology, Refractive error, Eye care professional, Pinhole occluder

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Transepithelial photorefractive keratectomy (tPRK), where both the epithelium and stroma are removed in a single-step, is a relatively new procedure of laser refractive error correction. This study compares the 3-month results of myopia and compound myopic astigmatism correction by tPRK or conventional alcohol-assisted PRK (aaPRK).This prospective, nonrandomized, case-control study recruited 148 consecutive patients; 93 underwent tPRK (173 eyes) and 55 aaPRK (103 eyes). Refractive results, predictability, safety, and efficacy were evaluated during the 3-month follow-up. The main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and mean refractive spherical equivalent (MRSE).Mean preoperative MRSE was -4.30 ± 1.72 D and -4.33 ± 1.96 D, respectively (P = 0.87). The 3-month follow-up rate was 82.1% in the tPRK group (n = 145) and 86.4% in aaPRK group (n = 90), P = 0.81. Postoperative UDVA was 20/20 or better in 97% and 94% of eyes, respectively (P = 0.45). In the tPRK and aaPRK groups, respectively, 13% and 21% of eyes lost 1 line of CDVA, and 30% and 31% gained 1 or 2 lines (P = 0.48). Mean postoperative MRSE was -0.14 ± 0.26 D in the tPRK group and -0.12 ± 0.20 D in the aaPRK group (P = 0.9). The correlation between attempted versus achieved MRSE was equally high in both groups.Single-step transepithelial PRK and conventional PRK provide very similar results 3 months postoperatively. These procedures are predictable, effective, and safe for correction of myopia and compound myopic astigmatism.

Concepts: Visual acuity, Myopia, Lens, Eyeglass prescription, Refractive error, Photorefractive keratectomy

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Myopia is the most common vision disorder and the leading cause of visual impairment worldwide. However, gene variants identified to date explain less than 10% of the variance in refractive error, leaving the majority of heritability unexplained (“missing heritability”). Previously, we reported that expression of APLP2 was strongly associated with myopia in a primate model. Here, we found that low-frequency variants near the 5'-end of APLP2 were associated with refractive error in a prospective UK birth cohort (n = 3,819 children; top SNP rs188663068, p = 5.0 × 10-4) and a CREAM consortium panel (n = 45,756 adults; top SNP rs7127037, p = 6.6 × 10-3). These variants showed evidence of differential effect on childhood longitudinal refractive error trajectories depending on time spent reading (gene x time spent reading x age interaction, p = 4.0 × 10-3). Furthermore, Aplp2 knockout mice developed high degrees of hyperopia (+11.5 ± 2.2 D, p < 1.0 × 10-4) compared to both heterozygous (-0.8 ± 2.0 D, p < 1.0 × 10-4) and wild-type (+0.3 ± 2.2 D, p < 1.0 × 10-4) littermates and exhibited a dose-dependent reduction in susceptibility to environmentally induced myopia (F(2, 33) = 191.0, p < 1.0 × 10-4). This phenotype was associated with reduced contrast sensitivity (F(12, 120) = 3.6, p = 1.5 × 10-4) and changes in the electrophysiological properties of retinal amacrine cells, which expressed Aplp2. This work identifies APLP2 as one of the "missing" myopia genes, demonstrating the importance of a low-frequency gene variant in the development of human myopia. It also demonstrates an important role for APLP2 in refractive development in mice and humans, suggesting a high level of evolutionary conservation of the signaling pathways underlying refractive eye development.

Concepts: Gene, Genetics, Gene expression, Evolution, Vision, Myopia, Refractive error, Visual impairment

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To determine six-year spherical refractive error change among white children and young adults in the UK and evaluate differences in refractive profiles between contemporary Australian children and historical UK data.

Concepts: Black people, United Kingdom, Europe, England, White people, Commonwealth of Nations, Refractive error, Northern Ireland

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Refractive error is the most common eye disorder worldwide and is a prominent cause of blindness. Myopia affects over 30% of Western populations and up to 80% of Asians. The CREAM consortium conducted genome-wide meta-analyses, including 37,382 individuals from 27 studies of European ancestry and 8,376 from 5 Asian cohorts. We identified 16 new loci for refractive error in individuals of European ancestry, of which 8 were shared with Asians. Combined analysis identified 8 additional associated loci. The new loci include candidate genes with functions in neurotransmission (GRIA4), ion transport (KCNQ5), retinoic acid metabolism (RDH5), extracellular matrix remodeling (LAMA2 and BMP2) and eye development (SIX6 and PRSS56). We also confirmed previously reported associations with GJD2 and RASGRF1. Risk score analysis using associated SNPs showed a tenfold increased risk of myopia for individuals carrying the highest genetic load. Our results, based on a large meta-analysis across independent multiancestry studies, considerably advance understanding of the mechanisms involved in refractive error and myopia.

Concepts: Extracellular matrix, Meta-analysis, Refractive error, Optometry

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PURPOSE: To evaluate the refractive and corneal topographical changes of overnight orthokeratology in myopia with two brands of contact lenses. METHODS: Fourty-four eyes of 22 myopic patients with manifest refraction spherical equivalent (MRSE) of -1.00 to -5.00 D (cylinder≤-1.0) were fitted with either DreamLens (Hanita Lenses Investments, Hanita, Israel) (group A) or Rinehart-Reeves (R&R; Danker Laboratories, Sarasota, FL) (group B) reverse-geometry lenses. Each subject eye was evaluated in regards to the uncorrected and corrected distance visual acuities, manifest refraction, slit lamp biomicroscopy, and corneal topography at each follow-up examination. RESULTS: The follow-up was 1 year. For groups A and B, the mean uncorrected distance visual acuity was -0.02±0.10 logMAR (20/20) and -0.08±0.12 logMAR (20/20) respectively at year-1 examination. The mean MRSE decreased from -2.70±0.9D to -0.50±0.08D in group A and -3.1±1.1 to -0.62±0.18D in group B at week-1; and remained stable thereafter in each group. For both groups, starting with week-1, the mean anterior best-fit sphere (ABFS) was statistically significantly flatter from baseline. A high correlation was found between the change in apical corneal power (ACP) and MRSE (r(1)=0.79, r(2)=0.71), and there was a good correlation between the change in ABFS and MRSE (r(1)=0.67, r(2)=0.64) in both groups. No significant ocular adverse events were observed during study. CONCLUSIONS: Both types of contact lenses safely and effectively decreased the myopic refractive error at 1 year follow-up. The refractive effect was mainly induced by the changes in the anterior corneal shape and the ACP.

Concepts: Visual acuity, Cornea, Myopia, Lens, Orthokeratology, Contact lens, Refractive error, Keratoconus

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Objective  To compare the Welch Allyn SureSight™ wavefront autorefractor with retinoscopy in normal dogs. Animals studied  Fifty privately owned dogs (100 eyes) of 20 breeds, free of ocular disease. Mean ± SD age: 5.7 ± 3.25 years (range: 6 months-13 years). Procedures  The refractive error was determined in each eye by two experienced retinoscopists using streak retinoscopy as well as by an autorefractor operated by two different examiners. Measurements were performed before and approximately 30-45 min after cycloplegia was induced by cyclopentolate 0.5% and tropicamide 0.5% ophthalmic solutions. Results  Mean ± SD noncyclopleged retinoscopy net sphere was -0.55 ± 1.14 (range: -3.75 to 3.5) diopters (D). Mean cyclopleged retinoscopy net sphere was -0.52 ± 1.18 (range: -4.25 to 2) D. Mean ± SD noncyclopleged autorefractor spherical equivalent (SE) was -0.42 ± 1.13 D (range: -3.36 to 2.73) D. Mean cyclopleged autorefractor SE was 0.10 ± 1.47 (range: -5.62 to 3.19) D. Noncyclopleged autorefraction results were not significantly different from streak retinoscopy (whether noncyclopleged or cyclopleged, P = 0.80 and P = 0.26, respectively). Cyclopleged autorefraction results were significantly different from noncyclopleged or cyclopleged streak retinoscopy (P < 0.0001 in both states). There was no significant difference between noncyclopleged and cyclopleged streak retinoscopy (P = 0.97). Conclusions  Noncyclopleged autorefraction shows good agreement with streak retinoscopy in dogs and may be a useful clinical technique. Cycloplegia does not significantly affect streak retinoscopy results in dogs.

Concepts: Eye, Ophthalmology, Sphere, Cycloplegia, Refractive error, Welch Regiment, Compact space, Retinoscopy