Fundus autofluorescence (FAF) imaging is an in vivo imaging method for metabolic mapping of naturally or pathologically occurring fluorophores of the ocular fundus. FAF provides information about the wellbeing of the retinal pigment epithelium (RPE).
Although the retina has many fluorophores, the fluorescence mainly derives from lipofuscin which is an ocular pigment and by-product of intracellular metabolism in the photoreceptors and RPE. Excessive lipofuscin gives excessive autofluorescence and vice versa.
63 year old male with an end-stage CNV scar tissue in the macula, visual acuity is 10/200. The scar tissue is well demarcated on the color fundus image, however, the FAF image shows the real extent of the pathology reaching out almost until the vascular arcades. The patchy hyperfluorescence around the scar indicates some remaining functional RPE.
A 39 year old female with mild visual symptoms in her left eye and a visual acuity of 20/20. Note the white spots around the macula which are showing hypofluorescence on FAF with minimal surrounding hyperfluorescent areas in some of the lesions. There are much more lesions visible on FAF compared to the color image. There was no activity seen neither on FLA nor with OCT.
35 year-old female with advanced Stargardt’s disease, visual acuity is 1mcf. The FAF image shows the excessive loss of RPE cells in the macula, which is correlated with the color fundus image. The surrounding patchy hypofluorescence is indicative of rod photoreceptor loss which is not evident on the color fundus image.
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FAF takes advantage of the fluorescent properties of lipofuscin, a normal by-product of photoreceptor metabolism. With age, lipofuscin accumulates in many types of cells throughout the body. In the eye, the retinal pigment epithelium (RPE) is particularly susceptible. Excessive build-up of lipofuscin in the RPE interferes with normal cell function, leading to photoreceptor degeneration and even cell death.
CR-2 Plus Retinal Camera
With the extra feature of fundus autofluorescence photography we have discovered retinal changes we have not seen before and which makes us learn more about retinal changes and diseases every day we use the Canon CR-2 Plus retinal camera.
Rune Brautaset BSc (Hon), MPhil, PhD, Associated professor, and Head of Unit/Director of Studies, Unit of Optometry/Optometry Education, Karolinska Institutet, St Erik's Eye Hospital, Stockholm, Sweden