Screening for CMV retinitis using chromatic discrimination thresholds and achromatic contrast sensitivity

Background-Many patients with cytomegalovirus retinitis (CMVR) are unaware of visual disturbance so screening is advocated for patients with HIV and l ow CD4 counts. Many tests of retinal function have been recommended but few are effective at detecting CMVR. We assess the potential of chromatic disc rimination thresholds and achromatic contrast sensitivity as screening test s for patients with CMVR. Method-11 HIV+ patients with CMVR, 16 age matched HIV+ patients, and 29 age matched controls were recruited. Visual acuity, chromatic discrimination t hresholds, and achromatic contrast sensitivity were measured. Fundal examin ation was performed by slit lamp biomicroscopy for HIV+ patients. Those wit h CMVR were photographed and the CMVR graded from the photographs. Results-Loss of chromatic discrimination was found in patients with CMVR (t ritan p<0.0005, red/green p<0.05). The same group had deterioration in achr omatic contrast sensitivity at 2.2, 3.4, and 10 cpd (p<0.05). There was cor relation between the zone of CMVR with chromatic gratings (tritan r=0.83, p <0.005). No statistically significant difference was found between the HIV patients and the controls for all tests (p>0.1). Conclusions-HIV+ patients with CMVR have a loss of chromatic discrimination and achromatic contrast sensitivity and this may be used to screen HIV+ pa tients for CMVR.