Glare testing in cataract patients: Instrument evaluation and identification of sources of methodological error

Abstract

This study sought to determine the relative sensitivity of two commercially available glare testers in predicting outdoor acuity in a population of patients with minimal cataracts. Two target optotypes were evaluated: high contrast letters and varying contrast sinusoidal gratings. Although both instruments demonstrated a significant correlation between indoor and outdoor acuity, they showed a significant difference between predicted outdoor acuity and obtained visual acuity. The brightness acuity tester on high intensity was inaccurate in predicting outdoor vision regardless of test optotype, overpredicting glare disability in 76% (average) of the study population. Glare disability overpredictions fell to 8% on the medium setting with +/- 2 lines of vision classified as "no change." Using the same criterion, the Miller-Nadler glare tester overpredicted glare disability in 2% of the cataract population but underpredicted glare disability in 62%. In this study, letter optotypes resulted in less variability than sinusoidal grating stimuli. In addition, we identify several methodological factors to consider before designing a glare experiment. These potential sources of error can influence the outcome of any glare study that compares indoor and outdoor acuity and include the study population, visual stimuli (optotypes), and elements of the outdoor testing situation.

Prospective randomised double-masked trial of bilateral multifocal, bifocal or monofocal intraocular lenses

“…VA was measured in the right and left eyes without and with the BAT at its brightest setting (400 ft. Lamberts, equivalent to bright sunlight on a white sand beach). 22 Glare was calculated as the difference between the two scores.…”

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

“…The outcomes of glare testing in clinical studies, however, most often have correlated poorly with various validity measures such as outdoor visual acuity in bright sunlight, [34,36], questionnaires assessing perceived visual disability, [23,24,35,38] or measured forward light scatter [23,35,38]. In addition, the repeatability, as well as the discriminative ability of those glare tests that have been studied were often found to be inadequate [24,39].…”

“…Other authors, as noted in the introduction, have attempted to evaluate whether there is a correlation between the degree of lens opacification (reflected dispersion), that is perceived by the clinician on slit lamp examination, and the reduction in vision measured by high contrast acuity [25,[30][31][32] or by contrast sensitivity [33][34][35][36][37][38][39], or whether it is correlated with the increased measure of straylight assessed by the C-Quant [25,34,[45][46][47][48][49][50][51][52]. In the study presented here, this was difficult to assess because the cohort was small and consisted primarily of eyes with moderate nuclear cataracts.…”

“…In addition, the repeatability, as well as the discriminative ability of those glare tests that have been studied were often found to be inadequate [24,39]. Because of these deficiencies, a standard method of glare measurement has never been adopted, as discussed in several papers [25,34,[43][44][45][46][47][48][49][50][51][52].…”

“…Multiple models of clinical glare testers have been introduced that most often consist of the patient reading a standard visual acuity chart [25,[30][31][32] or contrast sensitivity chart (e.g., sinusoidal gratings, [33][34][35][36], Landolt rings, [34,37] or Pelli-Robson charts [38,39]) with and without a glare source presented at some angular distance from the targets visualised at fixation. Various methods that have been developed [6,40] differ with respect to test targets, glare light sources and luminance levels, but in most, the glare was produced by surrounding the discriminated targets with glare sources ranging between 6,000 and 25,000 cd/m².…”