As one of professional eye care’s most versatile diagnostic screening techniques, fundus autofluorescence imaging has helped to preserve the vision of several thousand patients throughout its relatively short existence.
This dynamic imaging process has origins in fluorescein angiography, a procedure first performed fifty years ago, when ophthalmologists recognized that the retina of the human eye contained fluorophores – chemical structures that, when exposed to light of an appropriate wavelength, revealed fluorescent properties.
Fluorophores form as retinal photoreceptors containing light-sensing molecules shed their damaged outer segments, which are then ingested by the retinal pigment epithelium (RPE) through phagocytosis to form lipofuscin; lipid-based pigment granules that build up in RPE cells as a metabolic byproduct of cell function. Several factors including age, disease and oxidative damage affect the rate of lipofuscin production.
Recognizing that fluorescent emissions could help monitor retina circulation and diagnose disease, medical equipment manufacturers developed fundus cameras equipped to identify highly fluorescent ocular structures that could cause damage.
Due to the very low levels of fluorescence output however, the results of examinations using this equipment were often inconsistent and unreliable, prompting research for a new instrument that could effectively capture this potential symptom.
Two methods answered the call to record autofluorescence in the eye: confocal scanning laser ophthalmoscopy and standard fundus camera photography.
Thoroughly scanning the retina using a laser, confocal scanning laser ophthalmoscopy collects a rapid succession of images at near video rate to reduce background noise and improve the probability of detecting relatively weak autofluorescent structures over a large assortment of images.
While the confocal pinhole isolates a signal to provide greater resolution, the conditions that increase fluorescence on multiple planes are not detected as well when using confocal scanning laser ophthalmoscopy based systems compared to fundus camera photography.
In contrast, the fundus camera can image fluorescence from both the retina and the RPE. The signal strength is also strong enough to require only photography to procure sufficient information about the health and function of the central retina and the periphery of the eye.
Autofluorescence imaging’s ability to capture the RPE offers valuable information in diagnosing conditions that provide symptoms in this area of the eye. By recording metabolic changes from the accumulation of toxic fluorophores in the retinal pigment RPE, an eye care professional can detect potential degenerative changes, oxidative injuries and lesions.
In addition, using longer wavelengths of light, usually in the green and near infrared spectra, is less likely to be absorbed by the eye’s crystalline lens and provide added detail in the fovea to further aid retinal diagnosis. Fundus autofluorescence imaging can also use light from outside of the visible spectrum to extend its functions by recording the distribution of melanin in the eye.
By providing functional information about retinal cells, fundus autofluorescence imaging can help detect a variety fundus disorders including age-related macular degeneration (AMD), central serous chorioretinopathy, retinal detachment, vitelliform dystrophy (Best disease) and acute zonal occult outer retinopathy (AZOOR).
Figure 1: Images of the human retina highlighting Geographic Atrophy, captured using Fundus Autofluorescence imaging equipment. Photo courtesy of Fundus Photo, LLC.
Speaking on fundus autofluorescence imaging’s contributions to eye care, Dale Brodsky, CEO of Fundus Photo, revealed the company’s intentions to support and further develop advances of this important screening technique:
“Like most technology, fundus autofluorescence imaging continues to evolve. Its place in the worlds of ophthalmology and optometry is already well established by the ability to offer unique information about a patient’s RPE lipofuscin accumulation and anatomic information.”
“Providing supportive resources like the New Vision Ophthalmic Imaging Software, Fundus Photo strives to accelerate and simplify the integration of fundus autofluorescence imaging with other methods of eye care diagnosis and monitoring.
“In doing so, we hope to empower ophthalmologists and optometrists, enabling them to acquire a greater understanding of a patient’s medical condition through less invasive and affordable methods to administer faster and more effective treatment.”
Fundus Photo’s New Vision Ophthalmic Imaging Software helps ophthalmologists, optometrists and primary care physicians performing fundus autofluorescence image screenings improve their analysis, diagnosis and management of patient information across the wider healthcare network.
In addition to image viewing and editing tools including automatic zoom, contrast, brightness, negative image, emboss and annotation, New Vision PRO version software includes video, .doc, .pdf, and .xls support. These features allow professionals to transfer images and data to any workstation, PC, exam room, electronic medical record or electronic health record database in the world. Fundus Photo also maintains zero cost technical support for its clients.
For a full list of New Vision Ophthalmic Imaging Software’s capabilities and guarantees, click here.
As research continues to define the crucial role of lipofuscin in various retinal disease processes, interest in retinal imaging equipment is likely to grow. Retaining its position at the forefront of retinal diagnostics, fundus autofluorescence imaging will help to monitor new, interventional strategies designed to slow the accumulation of lipofuscin compounds for years to come.
About Fundus Photo
Fundus Photo is the only ophthalmic digital imaging provider in this segment to earn US FDA 510(k) and ISO clearance for commercial distribution in the United States in accordance with Medicare program requirements. The company’s technology also offers system versions in full compliance with DICOM standards. To read Fundus Photo’s DICOM conformance statement, click here. For more information about Fundus Photo’s complete imaging solutions, click www.fundusphoto.com.