Contrast Sensitivity Among Patients with Birdshot Chorioretinopathy

Purpose To assess contrast sensitivity in patients with birdshot chorioretinopathy; to identify relationships between contrast sensitivity, other measures of visual function, clinical findings, and quality of life. Design Single-center, cross-sectional study. Methods We measured contrast sensitivity in 63 patients (126 eyes) at four spatial frequencies (3, 6, 12, 18 cycles/degree [cpd]) using the CSV-1000E instrument (VectorVision, Greenville, Ohio, USA). Abnormal contrast sensitivity was defined as two standard deviations below the mean for population norms. Results at spatial frequency 12 cpd were compared to the following parameters in per-eye analyses: best-corrected visual acuity (BCVA); presence of eight specified symptoms; color vision; visual field parameters (foveal threshold, mean deviation); and optical coherence tomography parameters (central macular thickness, loss of the third highly reflective band). Results were compared to the National Eye Institute Visual Function Questionnaire (VFQ)-25 in per-patient analyses. Results were adjusted for age, disease duration, treatment, BCVA, and lens status. Results Contrast sensitivity (spatial frequency 12 cpd) was abnormal in 99 eyes (92%), and was related to poor BCVA ( P = .0004) and the symptom of poor contrast sensitivity ( P = .025). Among 38 eyes with normal BCVA (≥1.0), 31 eyes (82%) had abnormal contrast sensitivity. There was a positive correlation between contrast sensitivity in better eyes and the VFQ-25 composite scores ( r = 0.51; P < .001). Conclusion Decreased contrast sensitivity is common in patients with birdshot chorioretinopathy and may occur in the absence of other visual changes. Contrast sensitivity may be a useful measure for clinical studies of birdshot chorioretinopathy and for monitoring patients with the disease.