EFFECT OF A CATARACT SIMULATION ON CLINICAL AND REAL-WORLD VISION

Aims/background - Many reports have indicated that some patients with cataract can retain good visual acuity but complain of significant vis ual problems. This is the first in a series of papers trying to determ ine what causes these symptoms and whether other clinical tests can pr edict the real world vision loss. Methods - The effect of a cataract s imulation with a similar angular distribution of Light scatter as real cataract on clinical (visual acuity, contrast sensitivity, and disabi lity glare) and real world vision (face recognition, reading speed, an d mobility orientation) was investigated. Results - The simulation had a relatively small effect on visual acuity (6/6 with the simulation), but much larger effects on contrast sensitivity and low contrast acui ty with and without glare. The simulation had no effect on high lumina nce and high contrast real world tasks, such as mobility orientation i n room light and optimal reading speed. A small, but significant deter ioration was found for the slightly lower contrast task of face and ex pression recognition. However, under low luminance conditions, substan tial defects in mobility orientation were obtained (despite 6/6 acuity ). Conclusions - Although the relative effect of the cataract simulati on on acuity and contrast tasks is not typical of the average cataract , it can be found in those cataract patients with visual problems desp ite good visual acuity. This corroborates the suggestion that it is la rge amounts of wide angle Light scatter (forward and/or backward) whic h are at least partly responsible for visual disability in cataract pa tients with good visual acuity. A patient's reported visual disability may depend on the percentage of time he or she spends under low contr ast and/or low luminance conditions, such as walking or reading in dim illumination, and walking or driving at night, in fog, or heavy rain.