Patients' perception of visual impairment in glaucoma: a pilot study

Background/aims-There is a paucity of useful information on the level of vi sual disability suffered by glaucoma patients. The aims of this study were to determine and rank the frequency of self reported visual disability in d aily tasks performed by glaucoma patients; to examine the interrelation bet ween disabilities using factor analysis; to study the relation between perc eived visual difficulty and a measure of the severity of visual field loss; to develop a glaucoma specific subgroup of questions; and examine the vali dity and reliability of this subgroup of questions. Methods-63 glaucoma patients completed a questionnaire containing 62 questi ons covering 10 broad aspects of daily life activities using a five point a nswer scale. Patients were classified into three groups as having mild, mod erate, and severe field loss on the basis of the perimetric results. The re lation between a measure of the severity of visual field loss and subjectiv e visual disability in the three groups was examined. Results-Using factor analysis, the most frequently reported problems were g rouped into the following four categories: outdoor mobility, glare and ligh ting conditions and activities demanding functional peripheral vision, hous ehold tasks, and personal care. These four factors accounted for 72% of the variability in the patients' questionnaire responses. With increasing seve rity of binocular visual field loss there was an increase in the number of self reported visual problems. A loss of confidence in performing some rout ine daily tasks tended to precede self reported specific visual disabilitie s. The factor "glare and lighting and activities demanding functional perip heral vision" was found to have a significant relation with a measure of vi sual field loss and was used to create a glaucoma specific subset of questi ons. Cronbach's alpha showed a high degree of reliability and internal cons istency (alpha = 0.96) in this glaucoma specific subset of questions. Furth ermore, the validity of this new subset of questions was shown to be signif icant (r = 0.037, p < 0.05) for the correlation between a measure of the se verity of binocular visual field loss and the mean score of the variables u sed in the glaucoma specific subgroup of questions. Conclusions-Outcome measures and quality of life issues need to be addresse d in glaucoma. This pilot study identified common problems encountered by p atients which at the present time are not assessed in routine glaucoma care . it also identified a subgroup of questions that seems to be specific for glaucoma. Further research is required if a significant impact on the quali ty of life of glaucoma patients is to be achieved.