We thank DR Hirneiss for his interest in our study. We agree that the absolute value of the difference in correlation coefficients was small when comparing visual field (VF) scores with the total Assessment of Disability Related to Vision score and the 25-item National Eye Institute Visual Function Questionnaire score in the better and worse eye. However, we find it noteworthy that after adjusting for age, race, and visual acuity, the VF score in the better eye was correlated more highly with visual functioning across all VF staging systems, Assessment of Disability Related to Vision subtest scores, and 25-item National Eye Institute Visual Function Questionnaire scores. The findings of Gothwal and associates corroborate ours with regard to the ability of mean defect (MD) in the better eye to predict functional ability.

Dr Hirneiss suggests that his findings, from the study by Khadka and associates, contradict ours because of the higher correlation of MD in the worse eye rather than the better eye with regard to scores on their 9-item Glaucoma Activity Limitation (GAL-9) questionnaire. These correlations do not seem to be adjusted for visual acuity (VA). Although it is true that patients with mild glaucoma typically retain good central VA, the range of Snellen VA in the study by Khadka and associates was 6/6 to 6/6000 in the worse eye, indicating that patients with significant loss of VA indeed were included. Not only that, but VA in the worse eye was correlated more highly with GAL-9 scores than VA in the better eye in their study. Is the seemingly higher correlation of MD in the worse eye with GAL-9 scores, at least in part, a reflection of VA in the worse eye in this case? We would be very interested to see the correlations of MD in the better and worse eye when compared with GAL-9 scores after adjusting for VA.

We agree with Dr Hirneiss that the quality-of-life research in medicine and ophthalmology is just beginning and that the influence of patterns of VF defects on functional impairment is just one of many important questions that remain to be answered through future quality-of-life research in glaucoma.