Abstract
Purpose: :
to evaluate the change in the level of fundus autofluorescence in different retinal adaptation states ( mesopic, photopic and scotopic) and to analyse the time–course of recovery of retinal sensitivity after bleaching in normal subjects .
Methods: :
ten young normal subjects (mean age: 30 yrs) were included in the study. The fundus AF imaging was performed with a Heidelberg scanning laser ophthalmoscope (HRA1). Subjects were divided in two groups according to their refractive state: the first group included five subjects without refractive errors; the second group five subjects with low myopia < –6 D. For every subject we obtained AF images in steady condition of SLO lighting after: mesopic adaptation state, standard dark adapted state (30 min), bleaching and subsequently mesopic background. Image recording was extended for at least one hour.
Results: :
In the first group all individuals showed similar AF changes in different retinal adaptation states; AF intensity appeared similar when comparing mesopic and after–bleaching conditions. Conversely; AF intensity appeared decreased after scotopic adaptation, to be almost completely resumed after 30 minutes of mesopic steady state condition. In the second group all individuals showed similar AF changes in different retinal adaptation state; we observed slight modifications of AF after mesopic state compared with the bleaching state; conversely in these individuals we observed a higher loss of signal after bleaching and scotopic adaptation than in the first group individuals. In myopic individuals we did not observe normal AF recovery after a 30 minutes of observation.
Conclusions: :
This study emphasizes the dynamic aspect of AF fundus images in vivo.It is suggested that chemical changes linked to the visual cycle, which occur among various retinal adapted states, may create "masking effects" in the spectral emission of lipofuscin or generate spectral emissions similar to those of lipofuscin.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • photoreceptors