Computer Measurement of Central Visual Acuity under Mesopic and Glare Conditions in Eyes with Nuclear Cataract

Walter Gutstein,Stephen H Sinclair

doi:10.4172/jcsb.1000210

Walter Gutstein, Stephen H Sinclair

Open Access

https://doi.org/10.4172/jcsb.1000210

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Abstract

Purpose: The CVA is an interactive, automated computer device that rapidly thresholds central acuity under conditions mimicking customary photopic and mesopic activities. In sequence, the CVA may test up to 6 environments, in this series under 3 mesopic environments (98%, 50% MC against 1.6 cd/m2 background, 25% MC against 5 cd/m2), then 3 glare environments (98%, 10% and 8% MC, against 200 cd/m2). This report compares the CVA thresholded acuity with that measured with letter charts, as well as with C-Quant derived glare testing and patient responses to the Activities of Daily Vision Scale (ADVS) in eyes with nuclear cataract. Methods: In 33 eyes with nuclear cataract compared with 69 emmetropic eyes without lens opacity, best refracted acuity was measured under CVA modules and with ETDRS charts presenting similar contrast and luminance. Both groups were also tested with 15% MC charts placed outdoors with sun overhead and with sun at 15° off-axis and compared with the CVA acuty at 10% MC and 8% MC thresholded in a darkened room. In 22 of the eyes with nuclear cataract, C-Quant analysis of straylight glare was also performed along with the ADVS. Results: Acuities thresholded with CVA modules demonstrated high Pearson correlation coefficients, and Bland and Altman statistical similarity with the acuities measured from similar contrast charts. The acuities measured with CVA glare modules correlated significantly with charts placed in sun glare and with C-Quant measurements of straylight. Significant correlations were noted between CVA acuities and near vision as well as distance driving tasks. Conclusions: The CVA demonstrates the ability to accurately threshold the acuity of eyes with nuclear cataract compared with chart acuity under conditions of contrast, luminance and fixation times simulating normal photopic and mesopic activities and to provide the physician with glare evaluation and ability to function under multiple types of activities.

Highlights

Cataract lens opacification and color changes, occurring with age [1,2] and with systemic or ocular disease [3,4,5], world-wide have become the most common cause of visual complaints, primarily of glare and reduced contrast for multiple tasks in bright as well as dim light
Bailey [10] and Lasa et al [5] tested patients with cataracts using the Pelli-Robson and Vistech contrast sensitivity charts and reported that while both appear to evaluate visual function in moderate to advance cataracts, for early cataracts they and others [11] suggested that other techniques need to be developed including methods that utilize different luminance environments and off-axis glare elements in order to understand the range of visual disability under the varying environment conditions commonly presented during day and evening activities
Significant differences were noted among the eyes with nuclear cataract in comparison with normal eyes in all modules, except for the CVA 98% white-on-black mesopic module

Summary

Introduction

Cataract lens opacification and color changes, occurring with age [1,2] and with systemic or ocular disease [3,4,5], world-wide have become the most common cause of visual complaints, primarily of glare and reduced contrast for multiple tasks in bright as well as dim light. Patients having a cataract may demonstrate good visual acuity, whereas the contrast sensitivity testing demonstrates impairment even at early stages of the cataract development [3,4,5,7,8,9], especially when the eye is tested with off-axis glare. A loss of contrast sensitivity has been observed with brunescence or opalescence of the lens causing loss primarily in the middle and high spatial frequencies [12]. This causes greater difficulty in vision under unfavourable lighting conditions especially at dusk where older individuals require higher contrasts to recognize and differentiate objects [10,18,19]. Contrast sensitivity testing has been demonstrated to remain stable until the age of approximately 65 years beyond which it and overall visual function decline rapidly [12,19], thought primarily due to senile miosis and progressive nuclear sclerosis, as well as with the aging of neural elements, both retinal and brain [20]

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