Fundus autofluorescence (FAF) images the natural fluorescence of lipofuscin and other fluorophores within the retinal pigment epithelium, producing a map of RPE health that requires no dye and no injection.
Where a fundus photograph shows what the retina looks like, autofluorescence shows something closer to how metabolically stressed or depleted the RPE actually is at each point, which is information a colour photograph alone cannot provide.
How Fundus Autofluorescence Works
Lipofuscin accumulates within RPE cells as a natural by-product of the RPE’s ongoing task of processing shed photoreceptor outer segments, and it fluoresces when excited by light of an appropriate wavelength, typically blue or near-infrared depending on the system used.
A specific excitation wavelength is used to stimulate this fluorescence, and the emitted light is captured to build an image, entirely without any exogenous dye or intravenous injection.
The resulting signal reflects RPE cell activity and lipofuscin content rather than blood flow, which is the fundamental difference from angiography, and is what makes autofluorescence so useful for tracking degenerative and atrophic disease specifically.
Interpreting the Signal
Hyperautofluorescence
Increased signal reflects excess lipofuscin accumulation within stressed or dysfunctional RPE cells, seen in conditions including some pattern dystrophies, drusen, and the junctional zone at the margin of areas of geographic atrophy, where RPE cells are under metabolic stress before they die.
Hypoautofluorescence
Reduced or absent signal indicates loss of RPE cells and their lipofuscin content, most classically seen as the sharply demarcated dark patches of geographic atrophy, but also in areas of chorioretinal scarring, dense haemorrhage blocking the underlying signal, or RPE atrophy from other degenerative and inherited retinal diseases.
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From Choroida — the team behind this siteClinical Applications
Age-Related Macular Degeneration
Autofluorescence precisely delineates the borders of geographic atrophy, often more clearly than colour photography, and the hyperautofluorescent junctional zone surrounding an atrophic lesion is used as a marker of RPE tissue at risk of imminent progression.
Inherited Retinal Disease
Conditions such as Stargardt disease, retinitis pigmentosa, and gyrate atrophy show characteristic autofluorescence patterns that often reveal the true extent of RPE involvement well beyond what is visible on colour fundus photography alone, and serial imaging over time is used to track disease progression in these conditions.
Central Serous Chorioretinopathy
Autofluorescence can help distinguish acute from chronic disease and outline the extent of RPE change from long-standing or recurrent subretinal fluid, complementing OCT findings.
Monitoring Drug Toxicity
Hydroxychloroquine retinopathy produces a characteristic pattern of parafoveal or, in some populations, more peripheral autofluorescence change, and FAF is one of the recommended screening modalities used alongside visual fields and OCT for patients on long-term treatment.
Advantages Over Other Imaging
Being entirely non-invasive with no dye or injection required, autofluorescence can be repeated as often as needed for monitoring, without the allergic reaction risk or contraindications relevant to fluorescein or indocyanine green angiography.
It is fast, typically taking only seconds to acquire, and reveals RPE-level pathology that is often not obvious, or not obvious to the same degree, on standard colour fundus photography.
Limitations
Media opacity, including cataract or vitreous haemorrhage, degrades image quality and can obscure the underlying autofluorescence signal.
Autofluorescence does not show vascular flow or leakage, so it cannot replace fluorescein angiography when the clinical question is specifically about active leakage or neovascularisation rather than RPE status.
Interpretation requires correlation with other imaging and clinical findings, since hyperautofluorescence and hypoautofluorescence each have multiple possible causes, and the pattern alone does not always point to a single diagnosis without additional clinical context.
Clinical Impact
Autofluorescence has become a standard part of monitoring geographic atrophy, including in clinical trials of complement inhibitor therapy, where precise measurement of lesion size and growth rate over time depends heavily on this imaging modality.
In inherited retinal disease, it contributes meaningfully to diagnosis, prognostic counselling, and increasingly to trial eligibility assessment as gene therapy and other treatments reach clinical use for specific conditions.
As a non-invasive, repeatable, and information-rich technique, autofluorescence has moved from a research tool to a routine part of retinal imaging across a wide range of conditions, sitting alongside OCT as a standard component of a comprehensive retinal imaging workup.
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From Choroida — the team behind this siteReferences
- Schmitz-Valckenberg S, Holz FG, Bird AC, Spaide RF. Fundus autofluorescence imaging: review and perspectives. Retina. 2008.
- Holz FG, Bindewald-Wittich A, Fleckenstein M, et al. Progression of geographic atrophy and impact of fundus autofluorescence patterns in age-related macular degeneration. American Journal of Ophthalmology. 2007.
- Marmor MF, Kellner U, Lai TY, et al. Recommendations on screening for chloroquine and hydroxychloroquine retinopathy. Ophthalmology. 2016.
- Fundus Autofluorescence. EyeWiki, American Academy of Ophthalmology.
- Fundus Autofluorescence Imaging. StatPearls, NCBI Bookshelf.
