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.

Neovascular Age-Related Macular Degeneration (nAMD): A Review of Emerging Treatment Options.

Neovascular age-related macular degeneration (nAMD) is a common world-wide cause of visual loss. Intravitreal anti-vascular endothelial growth factor (anti-VEGF) agents are an effective means to treat nAMD and reduce its impact on vision compared to either sham treatment or photodynamic therapy. Currently, the approved anti-VEGF drugs include ranibizumab, aflibercept and brolucizumab. In addition, bevacizumab, used as an off-label drug, and has been shown to be effective in treating nAMD. While anti-VEGF agents are effective, its limitations include the requirement for frequent, often monthly injections, and the need for long-term treatment of nAMD. These present significant burdens on the healthcare system and on the patients. In addition, reviews of patients with nAMD treated with anti-VEGF have reported deterioration of vision over time with progression of geographic atrophy. These limitations are partly addressed by exploring different treatment regimens that reduce the frequency of treatments. Newer anti-VEGF drugs have been shown in Phase III clinical trials to have injection intervals as long as 12 or even 16 weeks for a proportion of patients. There is research on newer drugs that affect other pathways, such as the angiopoietin pathway, which may impact nAMD by extending the treatment interval and reducing the burden of treatment. Other measures include the use of sustained-release implants that release the drug regularly over a period of time, and can be refilled periodically, as well as hydrogel platforms that serve to release the drug. The use of biosimilars will also serve to reduce the cost of treatment for nAMD. A new frontier of gene therapy, primarily targeting genes involved in the transduction of retinal cells to produce anti-VEGF proteins intraocularly, also opens a new avenue of therapeutic approaches that can be used for treatment. This review paper will discuss both current treatment options and the newer treatments under development.

Independent Factors of Choroidal Thickness.

We read with interest the article by Agarwal et al. reporting that mean choroidal thickness was significantly higher in HIV patients, especially those with HIV microangiopathy, compared to healthy controls matched for age, ethnicity, and gender. We would like to highlight two important factors which may affect choroidal thickness assessment, namely diurnal variation and myopia, which should be taken into consideration. It is important to know that mean choroidal thickness is likely to be higher among HIV patients, especially those with HIV microangiopathy, compared to healthy subjects. However, it is also important to note and account for other factors, such as timing of image acquisition and refractive errors of subjects, as these could potentially affect the study results.

Cone Contrast Test for Color Vision Deficiency Screening Among a Cohort of Military Aircrew Applicants.

PURPOSE: To evaluate the use of the Cone Contrast Test (CCT) as a color vision screening tool in an Asian population of aircrew applicants and compare it against the Ishihara Psuedo Isochromatic Plates (PIP) - Edridge Lantern Test (ELT) screening pathway, assessing its impact on attrition with CCT cut-off scores of 55 and 75.METHODS: This is a retrospective review of 862 Republic of Singapore Airforce aircrew applicants tested with CCT and Ishihara PIP-ELT combination as screening. CCT repeatability was analyzed by comparing the subject's interocular (right vs. left eye) scores measured as the coefficient of repeatability (COR), with COR differing by ≥15 points considered to be outside normal limits.RESULTS: Of the applicants, 17 (1.97%) failed to achieve a CCT score of ≥55 (5 protan, 12 deutan), while 26 (3.02%) applicants failed to achieve a score ≥75 (5 protan, 21 deutan). Of the 17 applicants who obtained a CCT score of <55, 16 failed the Ishihara PIP test. The only applicant who passed the Ishihara PIP test had a CCT score of 50. Of all applicants, 1.7% had a COR of ≥15, with 93.3% of them identified as color vision deficient (CVD). Our results demonstrated excellent test repeatability, with 99.9% (835 out of 836) of color vision normal (CVN) applicants achieving a COR of <15 points.CONCLUSION: Our study demonstrated a high correlation between the CCT (passing score of ≥55) and the Ishihara PIP. Employing the CCT with a passing score of ≥75, instead of the Ishihara PIP-ELT combination, led to an increase in attrition rate of 0.7-3.0%.Chay IW, Lim SWY, Tan BBC. Cone Contrast Test for color vision deficiency screening among a cohort of military aircrew applicants. Aerosp Med Hum Perform. 2019; 90(2):71-76.

Optical Coherence Tomography Angiography Evaluation of the Parafoveal Vasculature and Its Relationship With Ocular Factors.

PURPOSE: To determine the size and characteristics of the superficial and deep foveal avascular zone (FAZ) in healthy adults by using optical coherence tomography angiography (OCT-A), and to ascertain the effects of demographic and ocular parameters on the FAZ size. METHODS: In a prospective cohort study of 117 healthy volunteers, foveal-centered 3 × 3-mm OCT-A scans were manually graded by certified graders to determine the size of the superficial and deep FAZ. Multiple linear regression analyses were performed to evaluate the impact of demographics and ocular factors, including central retinal thickness (CRT), choroidal thickness, axial length (AL), and spherical equivalent (SE) on superficial and deep FAZ areas. RESULTS: The mean age of the participants was 22.5 years, with mean AL of 25.4 mm and mean SE of -4.3 diopters. The mean CRT was 262.8 µm (range, 220-316 µm). The mean superficial FAZ area was 0.24 mm2, while the deep FAZ area was 0.38 mm2 (P < 0.001). Females had a larger superficial (P < 0.001) and deep FAZ (P < 0.001). On univariate linear regression, both superficial and deep FAZ areas had significant correlations with CRT, sex, AL, and SE, but not with age. By multiple linear regression analysis, in normal eyes, superficial FAZ area varied significantly with CRT and sex. Among eyes with high myopia, both superficial and deep FAZ varied significantly with CRT, sex, and choroidal thickness. CONCLUSIONS: The superficial and deep FAZ areas varied significantly among healthy eyes. Factors such as CRT, sex, SE, AL, and choroidal thickness influence the size of the FAZ.