Purpose: To compare psychophysically determined spatial variations in photopic and scotopic sensitivity across the macula in patients with retinitis pigmentosa (RP) and normal visual acuity who manifest an abnormal high-density ring of fundus autofluorescence (AF).
Methods: Eleven patients with a clinical diagnosis of RP were examined. All had rod-cone dystrophy (International Society for Clinical Electrophysiology of Vision [ISCEV]-standard ERGs), visual acuity of 6/9 or better, and an abnormal parafoveal annulus of high density AF. Fine-matrix mapping (FMM) was performed over macular areas of abnormal high-density AF under photopic and dark-adapted conditions. Pattern ERGs (PERGs) were performed in 9 of 11 patients, by using different sizes of circular checkerboards.
Results: Rings of high-density AF varied between patients (approximately 3 degrees -18 degrees in diameter). Photopic sensitivity was preserved over central macular areas, but there was a gradient of sensitivity loss over high-density segments of the ring and severe threshold elevation outside the arc of the ring. Scotopic sensitivity losses were more severe, and they encroached on areas within the ring. The radius of the high-density ring correlated with the lateral extent of preserved photopic sensitivity (r=0.86) and PERG data.
Conclusions: High-density rings of AF, which are present in some patients with RP with normal visual acuity, demarcate areas of preserved central photopic sensitivity. Scotopic sensitivity losses encroach on areas within the ring of high density and may reflect dysfunction before accumulation of lipofuscin.