Abstract
Purpose:
Glaucoma presents bilaterally in many patient, with a lag between presentation in the right and left eyes. In this analysis performed on the prospective data collected in an observational study, we assessed whether the overlap in the location of abnormal visual field (VF) between the right and left eyes increases over time.
Methods:
The dataset included 97 patients diagnosed with primary open-angle glaucoma were selected from the Diagnostic Innovations in Glaucoma Study (DIGS) and from the African Descent and Glaucoma Evaluation Study (ADAGES). The eye with the more advanced visual defect was selected as the reference eye (RE). The RE had a repeatable defect defined as a cluster of at least three points and no more than 26 abnormal points on the patter deviation plot (PDP). The fellow eye (FE) had at least ten follow up visits separately by at least 5 months. The VF of the RE was compared to each consecutive VF in the FE. The inter-eye concordance (IEC) ratio was calculated using this formula: 2C/(A+B+2C), where A represents locations abnormal in the right eye only, B represents locations abnormal in the left eye only, and C represents locations abnormal in both eyes (Boden et al, Ophthalmology, 2006; 113:918-23). The slopes for the IEC ratio over time were calculated for each patient.
Results:
Overall, a slightly positive mean slope was obtained (0.00003). Although the mean slope was small, it was positive as expected if the IEC increases over time. Furthermore, of the 97 patients included in the study, 71 (73.2%) had positive slopes.
Conclusions:
Inter-eye concordance increased slightly over time and more patients positive than negative slopes. The small slopes we obtained are in part due to the strict criteria we used for concordance given the known variability present in visual fields: the exact same location had be abnormal. Our results suggest that defects may develop in the same location in both eyes over time. In patients with unilateral glaucoma, particular attention should be given to the location showing defect in the affected eye.