Konrad Pesudovs, BSc Optom, Douglas J Coster, FRACO, Department of Ophthalmology, Flinders Medical Centre, Bedford Park, South Australia, Australia.

Purpose. This study aims to find the nexus between objective measures of visual function (especially, contrast sensitivity and glare disability) and the cataract patient's subjective visual disability.

Method. The measures of visual function employed were high contrast visual acuity (VA), low contrast (25%) visual acuity (LCVA), LCVA under glare conditions (LCVA glare), near visual acuity (Near VA), Pelli-Robson contrast sensitivity (PRCS), PRCS under glare conditions (PRCS glare) and spatial contrast sensitivity. Subjective visual disability was assessed by questionnaire. The relationship for each measure of visual function was explored by linear regression for each disability activity independently and grouped by activity type.

Results. Binocular visual functions were always better related to visual disability than single eye findings. The strength of the relationship between overall disability and all measures of visual function was not significantly different. However, the associations varied greatly for specific activities. Near visual disability was most strongly associated with Near VA (0.56), significantly better than any other measure (P<0.01). Mobility was most strongly associated with PRCS (-0.61), significantly better than any other measure (P<0.01) except PRCS glare (-0.57). Crossing the road was most strongly associated with PRCS (-0.64), significantly better than any other measure (P<0.01). Disability of seeing in bright light was most strongly associated LCVA glare (0.35) and PRCS glare (-0.31), significantly better than all non-glare measures (P<0.01).

Conclusions. Visual disability is a province of binocular vision. No single test of visual function can fully subjective disability. Visual acuity is a very useful measure of visual function, but other measures of visual function are needed to confirm patient's subjective disability. These other tests can be selected on the basis of symptoms. The pattern of functional loss may help in the pre-surgical work up of the cataract patient if the symptoms cannot be explained on the basis of VA findings, or the extent of the symptoms seems inconsistent with the ocular pathology.