We have offered Optos Wide Angle Retinal scanning since 2013, but the new instrument with its ability to detect the natural autoflourescence of the cells of the retina allows us to see the activity of cells undergoing degenerative changes, as in cancer, and which hopefully can be treated, and also identify cells that have died.
Autofluorescence (AF) is caused by the presence of lipofuscin, an aging pigment fluorophore thought to be produced by the outer segments of the photoreceptors and stored at the level of the retinal pigment epithelium (RPE).
Autoflouescense is defined as the spontaneous emission of a wavelength of light by a substance, such as lipofuscin, after illumination with light of a different wavelength. AF uses the excitation of fluorophores, which are inherent in the retina, and also a barrier filter, which blocks most of the light that would reflect off the retina in a typical photo. Different AF systems use different excitation sources and barrier filters, but all demonstrate a uniform glow to the normal retina.
AF often reveals when a disorder is progressing before the cells have actually died. Two abnormal states of lipofuscin exist, hyperautofluorescence (hyper AF) and hypoautofluorescence (hypo AF).
In hyper AF, the image in the area that’s affected will be brighter than the corresponding normal zones, and this is typically thought to be due to the increased metabolic activity of the retinal pigment epithelium. Hyper AF highlights cells that are exhibiting abnormal activity and indicates an early state of disease. This can be seen in early stages of macular degeneration, Best’s disease, Stargardt’s disease, cone dystrophy, retinitis pigmentosa and melanoma.
In contrast, with hypoautofluorescence, there’s no normal glow of the fluorescence; it’s actually just completely dark or even black. This suggests that there’s no lipofuscin present because the retinal pigment epithelial cells have died, along with the corresponding photoreceptors. Hypo AF is a marker for dead cells.
Lipofuscin cells, in normal, healthy tissue, show luminance in themselves, and will appear gray in the images. This is the way it should look in normal healthy patients.
When differentially diagnosing a metabolically active melanoma vs. an inert choroidal nevus. nevi are invisible with AF because the RPE is intact, but melanomas are typically hyper AF.
The Optos Daytona AF provides a wide angle autoflourenscent image to detect abnormal cell activity over a large area of the retina in a quarter of a second. I am very exited to have this new technology in my office.
The Daytona with AF reveals a layer of the retina not visible with the previous instrument. Anyone who has had the previous Optos imaging done in our office this year can have the imaging done with the new instrument at no additional charge. We will be making autoflourescense part of Optos exam starting July, 2017.