Abstract
Purpose: :
To characterize and monitor abnormal fundus autofluorescence (AF) in patients with retinitis pigmentosa (RP) who have good visual acuity.
Methods: :
Fifty patients with a clinical diagnosis of RP, including 10 cases of Usher syndrome, were examined retrospectively. All had rod–cone dystrophy (ISCEV–standard ERGs), normal visual acuity and manifested a parafoveal ring of high density fundus autofluorescence. Repeat autofluorescence images, obtained after periods of between 2 and 5 years in 12 patients, were examined. Pattern ERG (PERG) was performed in all cases. Multifocal ERG (mfERG) and visual fields (VF) were performed in representative cases.
Results: :
The rings of high density autofluorescence varied in size between patients (from 4°–18° diameter). Pattern ERG P50 components correlated with ring radius in patients with RP (r= 0.77, N=40) and in patients with Usher syndrome (r=0.86, N=10). MfERGs showed relative preservation over the central macular area. The mean eccentricity at which significant mfERG reduction occurred varied between subjects. There was a positive relationship between ring size and the maximum mean eccentricity of response preservation for both mfERG P1 (slope = 1.4, correlation coefficient r = 0.73, N=20) and N1 (slope=1.4, r=0.74) components. Progressive constriction of the AF ring was demonstrated at follow–up in 3 of 12 patients. Serial PERG, mfERG and VFs, performed in one of these cases, showed evidence of deteriorating function concordant with ring constriction.
Conclusions: :
High density rings of autofluorescence, seen in some patients with RP or Usher syndrome with normal visual acuity, demarcate areas of preserved central photopic function. MfERGs correlate with the area encircled by high density AF and the PERG data. The size of the ring of AF can show progressive constriction that is accompanied by increasing macular dysfunction.
Keywords: retinal degenerations: hereditary • electroretinography: clinical • imaging/image analysis: clinical