Photopigment bleaching is often characterized by an artifactual increase in fundus autofluorescence (FAF) due to intense blue light exposure, such as short-wavelength fundus autofluorescent imaging.1–3 This phenomenon can appear similar to other conditions resulting in apparent hyperautofluorescence, including the perifoveal ring with retinitis pigmentosa, multiple evanescent white dot syndrome, active or resolved central serous chorioretinopathy, and retinal detachment after repair, typically manifesting with diseases or conditions affecting the outer retina.1,3 In contrast to photopigment bleaching, these diseases result in hyperautofluorescence from loss of photopigment within the photoreceptor outer segments or loss of macular luteal pigment. Herein, the authors demonstrate photopigment bleaching producing an artefactual increase in choroidal fluorescence during scanning laser ophthalmoscopy (SLO) fluorescein angiography (FA).
A 30-year-old white woman presented for routine ophthalmic examination. Her history was significant for multiple sclerosis, relapsing-remitting type, diagnosed on basis of paresthesia and characteristic brain lesions with neuroimaging, but not optic neuritis. Current medications included natalizumab (Tysabri; Biogen, Cambridge, MA) for 2 years, glatiramer acetate, and dimethyl fumarate (Tecfidera; Biogen, Cambridge, MA).
Snellen visual acuity was 20/30 both eyes. Anterior and posterior segment examinations were normal, aside from trace anterior vitreous debris. FA was performed on the Spectralis HRA+OCT (Heidelberg Engineering, Heidelberg, Germany), a scanning laser ophthalmoscopy (SLO)-based system using a 488-nm excitation wavelength and barrier filter at 500 nm. The initial transit, arterial, and venous phase images of both eyes were acquired with the 55° lens and found to be normal in both eyes (Figure 1). Subsequent images in the recirculation phase were acquired using the 102° lens, which demonstrated bilateral well-circumscribed circular areas of hyperfluorescence centered on the macula, consistent with an artifactual increase in choroidal hyperfluorescence (Figure 2) due to photobleaching in the region previously imaged with 55° lens. The patient has remained asymptomatic without any new retinal changes at last follow-up.
Late arterial phase fluorescein angiography at 55° acquired with scanning laser ophthalmoscopy shows normal retinal and choroidal perfusion of right (left panel) and left (right panel) eyes.
Widefield recirculation phase fluorescein angiography at 102° captured with scanning laser ophthalmoscopy demonstrates round areas of central choroidal hyperfluorescence in right (left panel) and left (right panel) eyes. This circular, well-circumscribed pattern is due to photobleaching from intense, short-wavelength light emission during earlier acquisition with the 55° lens, contrasted with adjacent, unaffected peripheral retina.
Observed hyperautofluorescence corresponding to small field fundus illumination with continuous 488-nm light, prior to imaging a wider field of view, has been an experimentally demonstrated, clinically relevant phenemon.1,2 This finding can easily mimic a vision-threatening disease process,1 particularly for a patient who has pertinent medical history, such as multiple sclerosis. To the authors' knowledge, however, this case describes the first photopigment bleaching artifact occurring during routine FA.
The intense blue light (488 nm) emitted with the SLO effectively bleached the photopigment in the area subtended by the 55° lens. The photopigment molecules in the outer segments subsequently isomerized from 11-cis retinal to all trans retinal upon concentrated exposure of photons relative to the surrounding retina.2,3 Consequently, there was enhanced penetration of excitatory 488-nm light and the fluorescent wavelengths greater than 500 nm originating from the fluorescein dye in this fundus region. This enhanced signal became visible with the 102° lens, as a relative window defect within the central 55°.
In conclusion, artifactually enhanced signal due to photopigment bleaching following blue-light emission, can occur during both FAF and FA imaging. Clinicians should remain aware of these imaging artifacts, which can easily be mistaken as pathologic in certain settings.
- Freund KB, Mrejen S, Jung J, Yannuzzi LA, Boon CJF. Increased fundus autofluorescence related to outer retinal disruption. JAMA Ophthalmol. 2013;131(12):1645–1648. doi:10.1001/jamaophthalmol.2013.5030 [CrossRef]24136134
- Theelen T, Berendschot TTJM, Boon CJF, Hoyng CB, Klevering BJ. Analysis of visual pigment by fundus autofluorescence. Exp Eye Res. 2008;86:296–304. doi:10.1016/j.exer.2007.10.022 [CrossRef]
- Joseph A, Rahimy E, Freund KB, Sorenson JA, Sarraf D. Fundus autofluorescence and photoreceptor bleaching in multiple evanescent white dot syndrome. Ophthalmic Surg Lasers Imaging Retina. 2013;44:588–592. doi:10.3928/23258160-20131105-08 [CrossRef]24221465