Higher order aberrations and visual function in a young Asian population of high myopes.

Purpose: To examine the associations between higher order aberrations (HOAs), visual performance, demographics, and ocular characteristics in a young Asian population with high myopia. Methods: This was a retrospective review of military pre-enlistees conducted between March 2014 to September 2018. Visual acuity and contrast sensitivity were tested under photopic, mesopic and simulated night conditions. Ocular, corneal and internal HOAs were measured with a Hartmann-Shack wavefront aberrometer (KR-1W, Topcon Co., Tokyo, Japan). Results: 522 eyes of 263 consecutive subjects with severe high myopia (defined as spherical equivalent refraction [SER] ≤ -10.00D) in at least one eye, and high myopia (SER ≤ -6.00D) in the fellow eye, [mean (SD) SER -11.85 (2.03D)] were analysed. The mean (SD) age of subjects was 18.5 (1.6) years. Chinese eyes had significantly greater internal total HOA root-mean-square (RMS) compared to Malay eyes [mean difference (SD) 0.0246 (0.007) µm, p < 0.001). More negative SER was associated with greater ocular total HOA (p = 0.038), primary coma (p = 0.003) and tetrafoil (p = 0.025) RMS, as well as more positive ocular (p = 0.003) and internal primary spherical aberration (p = 0.009). Greater ocular total HOAs was associated with reduced visual acuity in simulated night conditions and low contrast, decreased contrast sensitivity under mesopic and simulated night conditions (all p < 0.05). Conclusions: Greater HOAs were associated with Chinese ethnicity and more negative SER in a young Asian population with high myopia. Greater HOAs were associated with poorer visual performance in low luminance and reduced contrast conditions.

A Preliminary Study on Normalized Pattern-Reversal Peripheral Field SSVEPs as a Potential Objective Indicator of Useful Field of View Performance.

PURPOSE: Currently, the test for useful field of view (UFOV) typically relies on subjective feedback for detecting peripheral targets while attending to a central target. Steady-state visual evoked potential (SSVEP) recorded from the occipital region of the brain has been frequently used as an objective alternative to replace subjective responses. Our aim was to investigate if a short screening test can approximate UFOV performance objectively. METHODS: We recorded SSVEPs during a simple peripheral task and a UFOV task with and without distractors as well as 30-second offline SSVEPs for eight participants. In all tasks, a peripheral annulus ring of checkered reversal pattern was concurrently presented to the participants to elicit SSVEPs. RESULTS: Orthogonal linear regression analysis found that normalized SSVEP during the UFOV task is predictive of peripheral target detection accuracy (F(1,6) = 16.250, P < 0.01, n = 8) for a task with peripheral distractors. However, this is not the case for a task without distractors (F(1,6) = 0.397, P = 0.552), possibly due to near-perfect accuracy across most participants. Offline normalized SSVEPs also only predicted the peripheral target detection accuracy (F(1,6) = 26.799, P < 0.01) for the UFOV task with peripheral distractors. CONCLUSIONS: Difficult peripheral target detection with distractors is required to differentiate UFOV performance in healthy young adults. The results suggested that offline normalized SSVEPs elicited by 30 seconds of pattern-reversal checkered annulus from the peripheral vision field can identify individuals with good UFOV performance under the stress of a difficult peripheral task.

Correlation of structural and electrophysiological changes in the retina of young high myopes.

PURPOSE: Despite a high prevalence of myopia among young East Asian adults, there is a lack of data on the myopic retina structure-function relationship in this group. We examined the association between optical coherence tomography (OCT) and electroretinogram (ERG) measurements in highly myopic young Asian adults to provide this information and also determined if OCT can be used as an alternative screening tool to assess retinal function in young myopic adults. METHODS: This was a prospective study comprising young adults aged between 18 and 25 years with spherical equivalent refraction of worse than -6.00 D. A comprehensive ophthalmic examination comprising fundus examination and grading, ocular biometry, time-domain OCT (fovea, macular and retinal nerve fibre layer thickness) and ERG (full field and multifocal) were performed for all the eyes. RESULTS: A total of 32 eyes (mean spherical equivalent ± standard deviation -10.17 ± 1.51 D, mean age 23.8 ± 1.3 years) were included. None of the eyes showed visible myopic retinopathy and the central retina thickness of all eyes was classified as within the normal range. Full-field ERG amplitude and multifocal ERG P1 amplitudes in the outer rings (R3-R5) were, however, inversely associated with axial length. The multifocal ERG P1 amplitudes were also positively correlated with mean retinal nerve fibre layer thickness in R2, 4, 5 rings and outer macular thickness in R 2-5 rings. CONCLUSION: These findings suggest that full field ERG changes may precede fundus and OCT changes in highly myopic young adults. Although there was some correlation between multifocal ERG amplitudes with OCT outer macular and retinal nerve fibre layer thickness, the OCT may not be useful as a retinal function screening tool, being within normal limits in all eyes. Further longitudinal studies are required to determine how the relationship between ERG and OCT will evolve over time.

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.

Pathologic changes in highly myopic eyes of young males in Singapore.

INTRODUCTION: This study describes the pathologic changes in the retina of a group of young Asian subjects with myopia worse than -10 diopters spherical equivalent (SE) refraction. MATERIALS AND METHODS: The study population consists of 20 male subjects undergoing preemployment screening for public service for a 1-year period from 2009 to 2010. A detailed series of visual tests of function, fundus examination and grading, ocular biometry and posterior segment optical coherence tomography were performed for all eyes. RESULTS: A total of 21 eyes with mean SE of -10.88 diopters, [standard deviation (SD) , 1.28 diopters], and mean age of 21.8 years (SD, 1.3 years) were included. Out of 21 eyes, 17 (81.0%) had beta peripapillary atrophy, 10 (47.6%) had clinically detectable optic disc tilt, 1 (4.8%) had positive T-sign and 18 (85.7%) had retinal tessellation, 4 (19.0%) had posterior vitreous detachment and 14 (66.7%) had peripheral retina degeneration. The mean retinal nerve fibre layer (RNFL) thickness was 92.48 mm (SD, 9.99 mm). CONCLUSION: None of the 21 highly myopic eyes had features of myopic retinopathy but most of these young males had clinically visible myopia-associated abnormalities of the optic disc, vitreous and peripheral retina. Generally, these eyes had thinner RNFL. Further longitudinal studies are required to investigate if these eyes will eventually develop complications of pathological myopia.