Association of SNTB1 with High Myopia.

PURPOSE: To investigate the associations of Single Nucleotide Polymorphisms (SNPs) in the SNTB1 gene with high myopia in a Han Chinese population. MATERIALS AND METHODS: Based on previous studies, four SNPs from the SNTB1 gene were chosen for genotyping. This is a case-control genetic association study comprising 193 high myopia participants and 135 normal emmetropic controls from a Han Chinese population. Allelic frequencies of the SNPs and haplotypes were compared to assess the associations of the SNPs with high myopia and axial length (AL). RESULTS: The SNPs rs7839488 (effect allele: A; OR = 0.685), rs4395927 (effect allele: T; OR = 0.692), and rs6469937 (effect allele: A; OR = 0.683) displayed significant associations with high myopia initially (P = .044, 0.049, and 0.035, respectively), but did not withstand permutation testing (all Ppermutation>0.05). rs6469937 displayed associations with high myopia in the dominant model (AG+AA: OR = 0.609) against GG (reference). rs6469937 was also associated with AL in the dominant model (AG+AA: Beta = -0.58) against GG (reference). The haplotype analysis demonstrated ATGA as the protective haplotype against high myopia, which remained statistically significant in permutation testing (Ppermutation = 0.045). CONCLUSIONS: Our findings are suggestive that SNTB1 is associated with high myopia in a Han Chinese population.

Correlation of myopia severity with visual performance.

PURPOSE: To describe visual performance in high myopia. METHODS: In this cross-sectional study, 148 emmetropes [spherical equivalent (SE) - 0.50 to + 1.00 D] and 564 high myopes [SE ≤ - 6.00 D] were categorised into three groups (Group 1: SE - 6.00 to > - 8.00 D; Group 2: SE - 8.00 to > - 10.00 D; and Group 3: SE ≤ - 10.00 D). Multivariate regression analyses adjusting for age and ethnicity examined the relationship between corrected distance visual acuity (CDVA) [photopic, mesopic and super vision test-night vision goggles (SVT-NVG)] and contrast sensitivity (CS)] (mesopic and SVT-NVG) with SE and axial length (AL). RESULTS: Mean age of subjects was 21.07 ± 1.17 years, and majority were Chinese (91.9%). Mean SE was 0.10 ± 0.23 D (emmetropes) and - 8.76 ± 2.04 D (high myopes), p < 0.001. Higher degrees of myopia were associated with reduced CDVA and CS, and increased AL (all p < 0.001). Among high myopes, Group 1 had the highest proportion of subjects with good CDVA (photopic ≤ 0.00 LogMAR, mesopic ≤ 0.00 LogMAR and NVG ≤ 0.10 LogMAR) and CS (mesopic ≥ 0.75 LogCS and NVG ≥ 0.35 LogCS) compared with Groups 2 and 3 (all p < 0.001). Among high myopes with good VA (photopic ≤ 0.00 LogMAR, mesopic ≤ 0.00 LogMAR and NVG ≤ 0.10 LogMAR), Group 1 also had the highest proportion of subjects who achieved mesopic ≥ 0.75 LogCS and NVG ≥ 0.35 LogCS (both p < 0.001). Multivariate analyses demonstrated that reduced VA and CS were associated with decreased SE and increased AL (all p < 0.001). CONCLUSIONS: High myopia is associated with reduced VA and reduced CS.

Refractive outcomes, corneal haze and endothelial cell loss after myopic photorefractive keratectomy in an Asian population: The Singapore Armed Forces' experience.

IMPORTANCE: This study reports outcomes of myopic photorefractive keratectomy (PRK) in a mainly ethnic Chinese population in Singapore. BACKGROUND: To assess the incidence and associations of corneal haze and endothelial cell count (ECC) loss up to 12 months after PRK. DESIGN: This was a retrospective case series conducted in a tertiary eye centre. PARTICIPANTS: A total of 158 patients (309 eyes) with a mean age of 22.1 ± 3.4 years were included. The majority was Chinese (97.4%) and male (97.4%). Mean preoperative spherical equivalent was -3.33 ± 1.15 D. METHODS: Eyes were categorized based on postoperative haze severity. A multivariate analysis adjusting for age and use of intraoperative mitomycin-C (MMC), preoperative sphere and cylinder was performed. MAIN OUTCOME MEASURES: Refractive outcomes and corneal haze 3 and 12 months after PRK were assessed. ECC measurements were obtained before PRK and at variable periods postoperatively. RESULTS: At 12 months, overall efficacy index was 0.98, and safety index was 1.09. Eight (2.5%) eyes underwent enhancement surgery. An analysis was performed on 295 eyes that did not undergo enhancement and had complete clinical data, which demonstrated a decrease in the incidence of haze from 38.2% at 3 months to 9.3% at 12 months. Higher myopia was associated with increased haze severity at 3 months (OR, 1.36; P = .005). Higher astigmatism was associated with increased haze severity at 3 (OR, 1.65; P = .018) and 12 months (OR, 2.32; P = .015). Intraoperative MMC was not associated with haze severity or ECC loss. CONCLUSIONS AND RELEVANCE: Myopia and astigmatism were associated with increased corneal haze severity. Intraoperative MMC did not accelerate ECC loss. Overall, PRK is effective, predictable and safe in Asian eyes.

Association of VIPR2 and ZMAT4 with high myopia.

Background: To investigate the associations of Single Nucleotide Polymorphisms (SNPs) in the VIPR2 and ZMAT4 genes with high myopia in a Han Chinese population.Materials and Methods: In this case-control genetic association study comprising 193 high myopia participants and 135 normal emmetropic controls from a Han Chinese population, 15 SNPs from the VIPR2 and ZMAT4 genes were selected for genotyping based on previous studies. Allelic frequencies of the SNPs and haplotypes were compared for association with high myopia and axial length (AL).Results: RS885863 (G-reference/A-effect) and RS7829127 (A-reference/G-effect) were significantly associated with high myopia (OR = 1.832, P = .045; OR = 0.539, P = .023 respectively). The associations of RS885863 with high myopia were observed under the dominant (GA+AA: OR = 1.972, P < .05) and co-dominant models (Heterozygous GA: OR = 1.874; Homozygous AA: OR = 5.310; P < .05) against GG (reference). The mean AL of GG was 25.94 mm, compared with that in GA and AA of 26.64 mm and 27.48 mm respectively. The associations of RS7829127 with high myopia were observed under the dominant (AG+GG: OR = 0.512, P < .05) and co-dominant models (Heterozygous AG: OR = 0.524; Homozygous GG: OR = 0.307; P < .05) against AA (reference). The mean AL of AA was 26.35 mm, compared with that in AG and GG of 25.62 mm and 25.17 mm respectively. The importance of RS885863 and RS7829127 were also highlighted by their being the constituent SNPs in the haplotypes (ACGA, P = .002; and GA, P = .008 respectively) that were significantly associated with high myopia.Conclusions: Our findings agree that RS885863 from VIPR2 and RS7829127 from ZMAT4 are significantly associated with high myopia in a Han Chinese population.

Risk factors for early-onset corneal haze after photorefractive keratectomy in an Asian population: Outcomes from the Singapore Armed Forces Corneal Refractive Surgery Programme 2006 to 2013.

PURPOSE: To assess the incidence and risk factors for early corneal haze after myopic photorefractive keratectomy (PRK). SETTING: Tertiary eye center, Singapore. DESIGN: Retrospective case series. METHODS: The refractive results and corneal haze severity 3 months after PRK were analyzed. Eyes were categorized into 4 groups based on haze severity. Multivariate ordinal logistic regression analysis adjusting for age, ethnicity, sex, use of intraoperative mitomycin-C (MMC), preoperative sphere, and preoperative cylinder was performed. RESULTS: The study reviewed data from 177 patients (347 eyes) with a mean age of 22.6 years ± 4.1 (SD). The majority of the patients were Chinese (98.3%) and men (98.3%). The mean preoperative spherical equivalent (SE) was -3.34 ± 1.19 diopters (D). One hundred thirty-five eyes (38.9%) had PRK with MMC. Ten eyes (2.9%) had enhancement surgery. The overall efficacy index was 0.88 and the safety index was 1.07. At 3 months, 187 eyes (53.9%) had no haze, 76 eyes (21.9%) had a haze grade of more than 0 and less than 1, 76 eyes (21.9%) had a haze grade of 1 or more and less than 2, and 8 eyes (2.3%) had grade 2 haze. Higher degrees of myopia (odds ratio [OR], 1.36; 95% confidence interval [CI], 1.13-1.63; P = .001) and astigmatism (OR, 1.56; 95% CI, 1.09-2.24; P = .014) were associated with increased severity of corneal haze, whereas older age (OR, 0.94; 95% CI, 0.88-0.99; P = .023) had a protective effect. CONCLUSION: Myopia and astigmatism were associated with increased severity of haze, and older age was protective against early corneal haze development after PRK in an Asian population. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Differences in prevalence of refractive errors in young Asian males in Singapore between 1996-1997 and 2009-2010.

PURPOSE: To determine the differences in prevalence rates of refractive errors in young Singaporean males over a 13-year period between 1996-1997 and 2009-2010 METHODS: Non-cycloplegic autorefraction data were obtained in a survey of 15,085 young male subjects (mean age 19.5 ± 1.4 years, range 16-25 years) in 1996-1997 using a Nikon NRK-8000 autorefractor. A second survey of 28,908 male subjects (mean age 19.8 ± 1.2 years, range 17-29 years) was conducted in 2009-2010 using a Huvitz MRK-3100 autorefractor. RESULTS: The overall prevalence of myopia (spherical equivalent, SEq, worse than -0.5 diopters, D) was similar in 2009-2010 (81.6%) and 1996-1997 (79.2%; odds ratio 1.38, 95% confidence interval 1.31-1.46; p < 0.001). The prevalence of high myopia (SEq worse than -6.0D) increased from 13.1% in 1996-1997 to 14.7% in 2009-2010 (p < 0.001). The prevalence of refractive astigmatism increased significantly from 41.4% in 1996-1997 to 50.9% in 2009-2010 (p < 0.001). CONCLUSIONS: Our results show that the prevalence of myopia and high myopia remained high and the prevalence of astigmatism increased in young male adults in Singapore over a 13-year period after controlling for age, education and ethnicity.