Test-Retest, within-visit variability of Goldmann visual fields in retinitis pigmentosa

Purpose. Reliable outcome measures are needed to estimate changes in peripheral vision during future treatment clinical trials for retinal degeneration patients. The authors examined the short-term variability of Goldmann visual field (GVF) results converted to retinal areas in retinitis pigmentosa (RP) subjects. Methods. Two within-visit GVFs were obtained from one eye each of 37 RP subjects with visual acuity better than 20/400 by a single experienced operator using the V4e (n = 28) or III4e (n = 12) target, or both. Planimetric GVF measures were digitized and converted to retinal areas in square millimeters by a single independent user. The 95% coefficient of repeatability (CR. ₉₅) for percentage change in central retinal area was determined from the test-retest difference. Results. There were no significant systematic trends toward either increase or decrease between the first and second GVF. For the III4e target, the CR. ₉₅ was 23.7% on average across all 12 subjects. For the V4e target, the CR. ₉₅ was 32.8% on average across all 28 subjects. However, 3 of 8 subjects with a geometric mean retinal area <10 mm ² (~7° radius) for the V4e target exhibited unusually large variability (50%-100%), and the CR. ₉₅ was 19.2% when these three subjects were excluded. Variability was not statistically significantly related to visual acuity, age, presence of cystoid macular edema, or subjects' stress or anxiety levels. Conclusions. Inherent test-retest variability (CR. ₉₅) of functional retinal areas derived from GVF results in a clinical RP population can be limited to <20% by using a single experienced operator, making the GVF the measure of choice for changes in peripheral vision.