A novel tool for quantitative measurement of distortion in keratoconus

Abstract

Background Keratoconus is associated with thinning and anterior protrusion of the cornea resulting in the symptoms of blurry and distorted vision. The commonly used clinical vision tests such as visual acuity and contrast sensitivity may not reflect the symptoms experienced in keratoconus and there are no quantitative tools to measure visual distortion. In this study, we used a quantitative test based on vernier alignment and field matching techniques to quantify visual distortion in keratoconus and assess its relation to corneal structural changes. Methods A total of 50 participants (25 keratoconus and 25 visually normal) completed the experiment where they aligned supra-threshold white target circles in opposite field in reference to guidelines and circles to complete a square structure monocularly. The task was repeated five times and the global distortion index (GDI) and global uncertainty index (GUI) were calculated as the mean and standard deviation respectively of local perceived misalignment of target circles over five trials. Results Both GDI and GUI were higher in participants with keratoconus compared to controls ( p < 0.01). Both parameters correlated with the best corrected visual acuity, maximum corneal curvature (K max ), topographical keratoconus classification (TKC) and central corneal thickness (CCT). Conclusion Our findings show that the quantitative measure of distortion could be a useful tool for behavioural assessment of progressive keratoconus.

Investigation into the relationship between Parallel Visual Task Processing Ability and Academic Performance in School-Age Children

“…In the examination, subjects need to judge whether adjacent lines are aligned (similar to cursor scales), and human cursor thresholds can be as low as 2 to 5 arcseconds. This method, capable of quantitatively measuring visual distortion, is often used to detect ne-level visual distortions and is frequently seen in eye diseases such as macular degeneration, glaucoma, and keratoconus [22] . Simultaneous vision, fusion vision, and stereopsis are three important functions for achieving binocular vision, widely used in clinical pediatric ophthalmology.…”

An investigation into the correlation between visual performance in simulated complex environments and academic attainment among primary school students

“…This program builds upon clinically common classic visual function test indicators by incorporating binocular rivalry tasks, creating a comprehensive binocular vision task mode (rivalry-state visual task). Specifically, it utilizes the cursor acuity test 27 and a three-level binocular vision function test (simultaneous vision, fusion vision, and stereoscopic vision) 28 as base indicators, combined with binocular rivalry-state tasks, to construct a complete visual function screening program that can assess the presence of visual distortion and risks of binocular imbalance in complex or poor visual environments. This program includes four key tests: Rivalry-cursor visual acuity test, Rivalry-simultaneous vision test, Rivalry-fusion vision test, and Rivalry-stereoscopic vision test (Fig.…”

Forward‐scattered and backward‐scattered light in moderate keratoconus

“…The effect of glare sensitivity resulting in visual impairment is called disability glare, which is defined by the CIE ( Commission Internationale d'Eclairage ) as retinal straylight, a result of studies that showed that disability glare can be understood on the basis of light scattering in the eye 9 . This disability glare represents the loss of retinal image contrast as a result of intraocular light scatter, or straylight, and it is one of the most widely reported symptoms by patients with KC 10 …”

“…9 This disability glare represents the loss of retinal image contrast as a result of intraocular light scatter, or straylight, and it is one of the most widely reported symptoms by patients with KC. 10 For those reasons, as KC progresses, not only is the perceived vision altered but also the optical quality of the eye and the patient's quality of life are affected. It is important to highlight that in moderate and advanced KC, in many cases, the loss of visual function as perceived by the patient is disproportionate to that reflected by clinical measurements.…”