Purpose
To determine the relationship between iso-, hypo- & hyper-autofluorescence (AF) observations and the corresponding layer-by-layer findings as revealed by SD OCT in a wide variety of retinal disorders as imaged with ultra-widefield AF (UWAF).
Methods
Retrospective analysis of 80 cases of retinal disorders imaged with both Optos UWAF & SD OCT. 39 had an inherited retinal degeneration (IRD), including cone-rod dystrophies, & various forms of RP, Stargardt, fundus flavi, Best; 41 had: infections, inflammations, drug toxicity, CHRPE, angioid streaks, AZOOR, trauma, central serous chorioretinopathy, pathologic myopia, geographic atrophy (GA) of RPE or a variety of drusen. OCT sections were within the arcades or between arcades/equator. All had color fundus imaging; some had fluorescein angiography (when indicated). ERGs & various forms of perimetry (including microperimetry, mp) were obtained when appropriate. Genetic testing has been obtained for many of the patients with IRDs. AF of the posterior pole was also obtained with Spectralis OCT in select cases.
Results
1) In 78 cases, SD OCT of iso-AF (normal AF) zones were normal when OCT analysis was limited to the outer retina (4 outer retinal bright bands intact). 2) In 79 cases, SD OCT of hypo-AF zones reveals loss of the Inner Segment ellipsoid line (ISe, aka IS/OS junction or Photoreceptor Integrity Line, PIL). ISe loss accompanied by subtle (in early RP) to dramatic RPE loss (in GA). 3) In 71 cases, SD OCT of hyper-AF zones reveals normal or near normal RPE but attenuated, fenestrated, disorganized or even absent ISe. 4) In CHRPE, the hypertrophic RPE is visualized with OCT as a hyper-reflective outer band but appears dark with AF. However, the ISe line is not visualized above the CHRPE on OCT; mp reveals a scotomatous area. 5) In retinal toxicity, either OCT or AF may provide the earliest indication of abnormality.
Conclusions
Although AF is generally considered to be due to lipofuscin in the RPE, hyper-AF is detected in conditions & locations where RPE appears normal on SD OCT but ISe does not. Hence, AF may also indicate photoreceptor (rod&cone) integrity. Studies of novel therapeutic approaches should consider both AF & SD OCT. Future devices capable of simultaneous acquisition of AF & OCT at any retinal location may prove helpful in such studies.
Keywords: 550 imaging/image analysis: clinical •
648 photoreceptors •
701 retinal pigment epithelium