Medical hypothesis discovery and innovation in ophthalmology

Editorial/No abstract

Age-related macular degeneration (AMD) is becoming the leading cause of blindness in developed countries. The exact etiology and pathophysiology of AMD is still unclear. A number of risk factors of AMD have been recognized, such as cigarette smoking, a family history of AMD and being Caucasian. On the other hand, aspirin is a widespread medication, which is thought to be associated with the prevalence or the survival of myocardial infarction and cancers. However, the evidence from the epidemiological studies has been contradictory and no persuasive conclusions have been made. Several problems, such as the parameters of aspirin use, the inclusion and exclusion of the participants and the required long-term follow-up, made it hard to conclude a definite relationship between aspirin use and AMD. Aspirin, as an anti-inflammatory agent, could prevent the inflammation and decrease the inflammatory damage, and might act as a deterrent for the progression of AMD. However, aspirin is an anticoagulant which might increase the risk of ocular hemorrhage in AMD patients. Decades ago, the use of aspirin was reported associated with decreased rates of CNV among AMD patients nevertheless recently, the association between aspirin use and increased risk of neovascular AMD was identified. Therefore, these current results should be challenged and acknowledged by well-designed, large-scale and long term follow-up studies. A consultation might be needed when aspirin is used in the neovascular AMD patients. To Download this article online, scan this QR code with your Smartphone

Investigations of choroidal vasculature have been of particular interest given choroidal vascular dysfunction are thought to be related with a number pathologic conditions such as central serous chorioretinopathy and various forms of AMD, including polypoidal choroidal vasculopathy. On the other hand, en face imaging of the choroid allows an exceptional alternative to histopathologic evaluation of the choroid, and can be used to quantify choroidal vascular structures. Our former study verified differences in the macular choroid in AMD and control patients previously noted on histopathologic studies. The use of phase-resolved approaches in larger population longitudinal studies reveal the sequence of RPE and choroidal changes in the pathogenesis of various AMD subtypes, which cannot be done using histopathology. Issues with lateral resolution of the OCT system in measuring choriocapillaris size could be solved by incorporating the axial dimension of the choriocapillaris into choriocapilaris diameter assessment (assuming the choriocapillaris are round in vivo), and by correcting for anisometric pixel resolution. Forthcoming studies are required to determine whether areas of choriocapillaris correlate with areas of RPD lesions.

Years ago, it was thought that a genetic component was the fundamental cause of a number retinopathy diseases including age related macular degeneration (AMD). Since then, information has emerged about novel genes that contribute to various forms of AMD and other retinopathies that have been eluding researchers for years. In the genetic sense, only the APOE 2 and 4 genes have been found to be a risk factor for sporadic AMD. But, a recent Genome wide association study (GWAS) revealed that an alteration of five SNIPs on the X chromosome in a gene named DIAPH2 may be a susceptibility gene for AMD. Furthermore, the gene DIAPH2 showed to have a polygenic pleiotropy for premature ovarian failure (POF) and AMD in a cohort of women. POF is highly associated with X chromosome skewing, an epigenetic alteration of the inactivation process of the X chromosome. These findings suggest a hypothesis that an epigenetic alteration on the inactivation centres of the X chromosome (or skewing) relates not only to aging, but might be a novel property that affects women with AMD more often than men.

Congenital colour vision defects affect about 8% and 0.5% of the male and female population, respectively. Pseudoisochromatic Ishihara plates have shown to be successful in an early diagnosis of colour vision defects. This commonly used colour vision test was initially intended to identify those who suffered from red-green aspect of congenital colour blindness; however, it may be of use to reveal acquired colour vision defects as well. Despite the Ishihara plates’ value, there are a number of shortcomings in their current layout. We proposing a new colour plate modified from original Ishihara test. To best assist illiterates who are not able to read English, standard Ishihara plates have been translated to Eastern Arabic numerals, which are used in most parts of the Middle East, Central Asia and Africa populations. The purpose of the present modification was to present the new plates to these regions, but more research and study is required to work on the validity, reliability, and repeatability of these new plates.

To analyse the effect of congenital unilateral ptosis on the ocular higher order aberrations (HOA) and to compare these eyes with normal fellow eyes this study has been performed. In this observational comparative case series, 16 eyes of 16 patients less than 15 years old with congenital unilateral upper eyelid ptosis were included. Corrected distance visual acuity (CDVA), corneal topography, ocular HOA’s with Zywave workstation was recorded. The amount of ptosis was measured from marginal reflex distance (MRD1). The ocular HOA’s were compared between the ptosis and the normal fellow eyes after making necessary corrections to avoid errors due to enantiomeric midline symmetry. The mean age was 12.5±2.7years (range7-15years). The mean MRD1 was -0.9±1.8mm in the ptosis eyes. There was significant difference noted in the mean 6mm Zernicke coefficients Z3−3 (p=0.002), Z4−2 (p=0.034), Z42 (p=0.008), Z5−5 (p=0.044), Z51 (p=0.039), Z53 (p=0.036), Z55 (p=0.044) between the ptosis and the fellow eyes. The mean Z3−3 was -0.17±0.15 and 0.07±0.12 in the ptosis and the normal eyes respectively. There was a significant difference (p=0.023) in total RMS (root mean square) between the ptosis and the normal eyes. Total coma aberration correlated with CDVA (p=0.004) and MRD (p=0.030) in the ptosis eyes. There was no correlation (p=0.815) between the age (duration of ptosis) and total RMS. In conclusion, Eyes with congenital ptosis differed from their normal fellow eyes in the higher order aberrations. None of the HOA’s which differed between the two groups affected the visual acuity in the ptosis eyes.