Abnormal fundus autofluorescence in relation to retinal function in patients with retinitis pigmentosa

Background: Fundus autofluorescence (AF) in some patients with retinitis pigmentosa is characterized by a parafoveal ring of increased AF which surrounds the centre as hypofluorescent changes appear at the periphery. The aim of this study was to evaluate the AF patterns in relation to retinal function measured by electroretinography and visual fields. Methods: Thirty-two patients with RP were included in the study. AF imaging of the macular area was performed with the scanning laser ophthalmoscope. Patients were divided in two groups according to their fundus AF patterns. All patients from group 1 had a ring of increased AF of different size but no atrophic areas inside vascular arcades. Patients with a ring of increased AF and round atrophic changes at different eccentricities from their fovea were selected in group 2. Visual fields were tested with kinetic, automated perimetry and microperimetry; the radius of the hyperfluorescent ring and the smallest distance of hypofluorescent areas from the fovea were compared to visual fields, PERG P50 and N95 and mfERG P1 amplitudes of the inner three rings. Results: A linear relationship was found in group 1 between the radius of the ring of increased AF and both the automated (r=0.82) and kinetic perimetry (r=0.80). The radius of the AF ring correlated highly with the PERG P50 (r=0.72) and N95 (r=0.74) amplitudes. In all patients, mfERG responses were reduced at all retinal locations, more pronounced at periphery. There was a good correlation between the ring of increased AF and the P1 amplitude of ring 2 of mfERG (r=0.62). Patients from group 2 had significantly reduced or non-recordable PERGs and mfERGs. The eccentricities of hypofluorescent changes did not correlate with any type of perimetry. Conclusions: Our results show that in stages of retinitis pigmentosa, before atrophic lesions spread inside the vascular arcades, the pattern of fundus autofluorescence correlates well with functional tests such as perimetry and electroretinography. The ring of increased AF appears to represent the border between functional and dysfunctional retina. This shows that autofluorescence, as a quick and non-invasive imaging tool, may be related to retinal function as well.