Ocular Autofluorescence – More Than Just the Fundus

Over the past decade, fundus autofluorescence imaging has become a commonly used diagnostic technique to document the presence of fluorescent structures in the eye.1-2 The term “autofluorescence” is used to differentiate fluorescence that may occur naturally from fluorescence that is derived from application of dyes such as fluorescein or indocyanine green.

Autofluorescence is most commonly used to document fluorescence of lipofuscin, a fluorescent pigment that accumulates in the retinal pigment epithelium (RPE) as a normal byproduct of cell function.3 Lipofuscin deposition normally increases with age, but may also intensify in certain retinal abnormalities. It is used to document progression of macular degeneration, central serous chorioretinopathy, Stargardt disease, drug toxicities, and several hereditary retinal dystrophies.

In addition to the documentation of lipofuscin in the RPE, there are other fluorescent findings that may occur in the eye. One of the initial uses of autofluorescence was documenting optic disc drusen and astrocytic hamartomas as early as the 1970’s.4 Both of these entities are calcified lesions that are highly fluorescent and can be documented with standard fluorescein excitation and barrier filters.

Fig 1 small
Left: optic disc drusen. Right: astrocytic hamartoma, a calcific tomor associated with tuberous sclerosis

The aging crystalline lens is also known to be fluorescent. In fact, lens autofluorescence was the inspiration for the development of fluorescein angiography by Novotny and Alvis.

LENS faf2
Dense cataract that fluoresces with the standard fluorescein excitation and barrier filter combination in a fundus camera. This image illustrates how fluoresence from the lens can compromise the qulaity of a fluorescein angiogram by adding unwanted fluorescence.

In addition to these well-known entities, there are some additional autofluorescent findings you may encounter in the eye. In 2009, Utine et al reported autofluorescence of pingueculae on the ocular surface.5 This finding may interfere with photo-documentation of topical fluorescein staining patterns in patients with conjunctival lesions.

pinguecula2
Autofluorescence image of a pinguela taken with a fundus camera in external mode. Note that the crystalline lens of this eye also fluoresces.

Certain emboli, presumably calcific, exhibit fluorescence.

plaque3
Patient with a branch retinal artery occlusion. Left image demonstrates classic retinal whitening from the occlusion. Right image identifies the fluorescent calcific plaque associated with the arterial blockage.

We’ve also had a case of corneal blood staining that fluoresced. As it turns out, hemoglobin and hemosiderin are known to be fluorescent and that’s what fluoresced in this case.

hemosiderin
A case of corneal blood staining after a long standing hyphema. Autofluorescence is presumably from either hemoglobin or hemosiderin.
angioid
Another case where blood is hyperfluorescent in a patient with angioid streaks.

There may be other ocular findings that exhibit autofluorescence when excited with light of specific wavelengths. Have you noticed anything else that fluoresces? If so, I encourage you to share them.

  1. von Ruckman A, Fitzke FW, Bird AC. Distribution of fundus autofluorescence with a scanning laser ophthalmoscope. Br J Ophthalmol 1995;79:407-412.
  2. Spaide RF. Fundus autofluorescence and age-related macular degeneration.
    Ophthalmology 2003;110:392-9.
  3. Delori FC, CK Dorey CK, G Staurenghi G, et al. In vivo fluorescence of the ocular fundus exhibits retinal pigment epithelium lipofuscin characteristics. Invest Ophthalmol Vis Sci 1995;36:718-729.
  4. Kelly JS. Autofluorescence of drusen of the optic nerve head. ArchOphthalmol 1974;92: 263-264.
  5. Utine CA, Tatlipinar S, Altunsoy M, et al. Autofluorescence imaging of pingueculae. Br J Ophthalmol 2009;93:396–399.

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