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

BACKGROUND/AIMS: There is a paucity of useful information on the level of visual disability suffered by glaucoma patients. The aims of this study were to determine and rank the frequency of self reported visual disability in daily tasks performed by glaucoma patients; to examine the interrelation between disabilities using factor analysis; to study the relation between perceived visual difficulty and a measure of the severity of visual field loss; to develop a glaucoma specific subgroup of questions; and examine the validity and reliability of this subgroup of questions.
METHODS: 63 glaucoma patients completed a questionnaire containing 62 questions covering 10 broad aspects of daily life activities using a five point answer scale. Patients were classified into three groups as having mild, moderate, and severe field loss on the basis of the perimetric results. The relation between a measure of the severity of visual field loss and subjective visual disability in the three groups was examined.
RESULTS: Using factor analysis, the most frequently reported problems were grouped into the following four categories: outdoor mobility, glare and lighting conditions and activities demanding functional peripheral vision, household tasks, and personal care. These four factors accounted for 72% of the variability in the patients' questionnaire responses. With increasing severity of binocular visual field loss there was an increase in the number of self reported visual problems. A loss of confidence in performing some routine daily tasks tended to precede self reported specific visual disabilities. The factor "glare and lighting and activities demanding functional peripheral vision" was found to have a significant relation with a measure of visual field loss and was used to create a glaucoma specific subset of questions. Cronbach's alpha showed a high degree of reliability and internal consistency (alpha =0.96) in this glaucoma specific subset of questions. Furthermore, the validity of this new subset of questions was shown to be significant (r=0.037, p<0.05) for the correlation between a measure of the severity of binocular visual field loss and the mean score of the variables used in the glaucoma specific subgroup of questions.
CONCLUSIONS: Outcome measures and quality of life issues need to be addressed in glaucoma. This pilot study identified common problems encountered by patients 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 quality of life of glaucoma patients is to be achieved.