Visual acuity and contrast sensitivity in cataract: Summation and inhibition of visual performance

Abstract

SummaryPatients exhibiting uniocular cataract often report an improvement in vision on closing their cataractous eye. Such qualitative evidence suggests the presence of bin ocular inhibition-the converse of binocular summation (that is the normal superior ity of binocular over monocular vision). To quantify the extent of inhibition in cataract, binocular and monocular visual acuity and contrast sensitivity were measured in 28 patients. Twelve patients showed binocular inhibition for visual acuity whilst 11 showed inhibition for contrast sensitivity measured at four cycles per degree (c.deg-1 ). Contrast sensitivity for 8 c.deg-1 targets was further recorded in a subset of 14 patients in whom seven showed inhibition. In patients who demonstrated inhibition, the mean decrement in performance for visual acuity was 13%. For con trast sensitivity at 4 and 8 c.deg-1 the mean decrement was 25% and 32% respect ively. The clinical significance of these findings is discussed with respect to the assessment of visual function and management of the cataract patient.

Long-time results and associations between subjective visual difficulties with car driving and objective visual function 5 years after cataract surgery

“…It is well known that unilateral cataract may cause binocular inhibition, which has been found to occur in up to 40% of these patients. 12 In addition to visual acuity, the role of contrast and glare disability are other factors to address in the context of cataract surgery and driving. Compared with daytime driving, a significantly larger percentage of drivers (P!.0000) experienced problems while driving in darkness 4 months as well as 5 years after surgery (36% and 43%, respectively).…”

White Paper Utilization, appropriate care, and quality of life for patients with cataracts

“…[35][36][37][38][39][40] Patients who had surgery in both eyes were significantly more satisfied with their visual function than patients who had surgery in only one eye. 36,41 Another study demonstrated that the cataractous eye interfered with the visual function of the pseudophakic eye, and after second-eye surgery, complaints of visual disability were eliminated.…”

Impact of differences between eyes on binocular measures of vision in patients with cataracts

“…Small studies in cataract patients 7,8,11 found evidence of binocular inhibition in contrast sensitivity and visual acuity. However, other populational studies 12,13 found a high correlation between binocular and the better-seeing eye measures, but differed in their results on the existence of binocular summation and inhibition.…”

“…4,6,7 Binocular summation and inhibition phenomena have been described for visual acuity and contrast sensitivity. [7][8][9] These phenomena are based on the difference between the values of the better eye and the binocular value, that is, with both eyes open. Summation is present when the binocular value is higher than the better eye value, and inhibition when it is lower.…”

“…Although closely related to visual acuity, contrast sensitivity has recently been shown to be an important dimension of vision because of its association with an increased risk of motor vehicle crash, 10 and because it is strongly affected by binocular summation and inhibition phenomena. 8 Thus, when cataract surgery causes differences between eyes, impairment in contrast sensitivity may play an important role in visual disability.…”