Abstract
Abstract: :
Purpose:To investigate fundus autofluorescence (AF) in different forms of retinitis pigmentosa (RP). Background:In histopathological findings rod density increases rapidly and relatively uniformly outside the fovea, reaching 60 000/mm² at 2° from the fovea and highest density of 100 000/mm² in the area defined as rod ring which surrounds the fovea at around 15°. Autofluorescence (AF) enables to observe early changes in the retinal pigment epithelium due to lipofuscin accumulation in early stages of photoreceptor damage. Since in many forms of RP mainly rods are primarily affected, changes in AF at the location of the rod ring may be expected. Methods:AF imaging was studied in 19 patients aged 7–66 years (mean 31y.) suffering from different forms of RP (XLRP 4 patients, ADRP 4 patients, RPsimplex 8 patients, ARRP 3 patients,). AF (exciting wavelength 488 nm) was recorded using a confocal scanning laser ophthalmoscope (Heidelberg Retina Angiograph, HRA; Heidelberg Engineering, Heidelberg, Germany). The rectangular field of view is adjusted to 30° x 30°. The data were evaluated with respect to the inheritance pattern, the age of the patient and the duration of the disease. Results:In the patients studied we found a high degree of interocular symmetry, therefore in each patient only one eye was evaluated. Typically, an enhanced ring shaped AF was present starting in mean at 3.6° (SD± 2.6°) from the center. In the periphery it reached in mean 10° (SD± 2.2°) at the narrowest part and 15° in mean (SD± 2.6°) at the widest part of the ring. The mean diameter of the ring like structure was 9° (SD± 2.4°). In RPsimplex the mean ring diameter was largest (10.3°) compared with the other forms (XLRP 8°, ADRP 8°, ARRP 7.6°). Early disease stages and young age were associated with a more regular AF pattern. In contrast, the size of the ring shaped increased AF did not correlate with age nor with the onset of the disease. Conclusions:In all forms of RP a ring shaped enhanced AF is visible centrally at approximately 4° from the fovea and reaching 10– 15° in the periphery i.e. at the location of the rod ring. The lack of visible AF at the very center is likely due to the amount of lutein and zeaxantin which blocks the AF to 488 nm. The ring shaped enhanced AF is already present at very early stages of disease, even when other funduscopic changes are missing, and can therefore be used as an additional phenotypical criterion.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retinal degenerations: hereditary • retinal pigment epithelium