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Multicolor Fundus Imaging Prepares for U.S. Debut
By Robert Murphy, Contributing Editor
In February, Heidelberg Engineering introduced a new multicolor fundus imaging system at the World Ophthalmology Congress in Abu Dhabi. While awaiting FDA clearance — expected later this year, according to Heidelberg Product Manager Joerg Pintaske, PhD — the company is marketing the system internationally to ophthalmologists and optometrists.
The scanning laser technology on which it is based puts to use multiple laser colors — infrared (820 nm), green (515 nm), and blue (488 nm) — to capture and display diagnostic information deriving from various retinal structures. The system balances the colors to match the appearance seen in photos.
Heidelberg's multicolor fundus imaging is compatible with all Heidelberg Spectralis OCT systems and it allows for nonmydriatic imaging. It can also be combined with fundus autofluorescence.
While its continuous laser scanning system delivers live multicolor images, making camera alignment easy, the confocal technology with which it's designed suppresses scattered light and produces high-contrast images.
“There are some key features to multicolor,” Dr. Pintaske says. “First of all, resolution. When you are using a laser scanning system and combining that with confocal imaging technology, you get a very crisp and clear image with high image contrast.”
Another benefit is that scanning laser technology penetrates cataracts more readily than does a flash-mode fundus camera. “Since this is based on laser scanning, the images are less affected by cataracts,” Dr. Pintaske says. “You can still get high-quality images even if you have a very dense cataract.”
Heidelberg's multicolor fundus imaging system offers infrared (left), green (center), and blue (right) options.
Other features are worth mentioning. Heidelberg's noise-reduction technology with active live eye tracking and automatic real time allow for so-called image averaging with resultant clear images. A compact, spacesaving device performs simultaneous laser scanning, both for multimodal imaging and comprehensive exams.
Viewing images of individual laser colors lets you gain a better understanding of anatomic and pathologic detail at different depths within the retina. Blue reflectance produces detailed images of ERMs, RNFL thinning, and macular pigment changes. Green laser helps provide detailed views of the retinal vasculature and extravasation. Infrared reflectance is ideal for identifying drusen and RPE.
Multicolor imaging is also valuable when examining eyes with DME and multiple areas of fibrotic tissue due to laser photocoagulation. Multicolor imaging reveals areas of abnormal RPE in the macula, which may be difficult to identify with a fundus camera.
The technology is also useful in detecting hard exudates and signs of hemorrhages in diabetic retinopathy. The full extent of structural changes is visible on the multicolor images, which also show highly reflective macular alterations.
“The beauty of these lasers is that all three, with their different colors, have different penetration into tissue,” Dr. Pintaske says. “When using blue, it's reflected more superficially, and you can nicely pick up the nerve fiber layer changes or epiretinal membranes.
“Using green, you can pick up everything that's going on within the neuroreceptor retina, including bleeding. And when using infrared, you have excellent penetration into tissue, and you can pick up changes at the level of the photoreceptors and the RPE, as well as morphologic changes in the choroid.” RP