Retinal camera sheds light on disease

December 1, 2011

Non-mydriatic device detects and monitors ocular condiions in compact, portable design

"One of the things that sets this camera apart is that it has a very small footprint. It can fit into any ophthalmic setting, and more importantly, it can [be used to] go out to the community and screen for vision-threatening diseases," said Dr Bernard C. Szirth, PhD, director of teleophthalmology, Institute of Ophthalmology & Visual Science, University of Medicine and Dentistry of New Jersey, Newark. "It's a very light camera, and it can fit into the back of the car so you can go to a different office or take it to a soup kitchen, a church, or some other setting where you can screen people for diseases.

"We know that half of the people who have diabetes, glaucoma, or age-related macular degeneration (AMD) don't know they have those diseases and won't go for an eye exam until it's too late," continued Dr Szirth, also a consultant for Canon who evaluated the camera after its development. "We're trying to capture these diseases early, and this camera fits that bill."

Another feature of this new camera is a white LED lamp. The LED provides diffused light, lasts a long time, and is unbreakable - helping to save on operating costs and replacement of flash tubes.

Having images obtained is also more comfortable for the patient because the Electro-Optical System camera sensor is very sensitive to light. The low flash intensity minimizes pupil constriction and shortens the time required for taking multiple pictures.

The camera's optional automatic exposure setting also should be convenient for technicians. "If you're not sure how much light is appropriate for the patient, the camera will choose for you," Dr Szirth said. "The camera can expose each frame correctly regardless of the amount of pigmentation in the eye. It really puts you at ease," he said, adding that manual exposures also will achieve good results.

True colour

The camera's technology has been adapted to capture extremely detailed diagnostic images and produces what Dr Szirth calls 'true hue', or true colour saturation.

"In imaging, it's very important that all three colour layers or wavelengths be represented, and the sensor allows you to have correct distribution of red, green and blue," he said.

Without true colour, the person interpreting the image might miss optic nerve pallor, indicative of glaucoma. Colour is also a guide to the health of the retina. The automatic exposure helps ensure that the colours remain consistent, which is particularly important in telemedicine when the physician sees only the image and not the patient, Dr Szirth explained.

The colour layers can be separated, with each of the three colours representing a different structure of the eye and providing information about different eye diseases. Blue represents the nerve fiber layer and is helpful for diagnosing glaucoma; green represents the retinal layer and would be used for detecting diabetic retinopathy or similar conditions, whereas red could help diagnose AMD, macular holes, nevi, or choroidal melanomas.

"Unless you have the correct hue for the image, you'll never be able to make the correct diagnosis. That's why I make a distinction between [this camera] and other popular brands," said Dr Szirth, who also uses other cameras in his clinic.

He also noted that the camera is easy to use. In his experience at a large clinic with frequent staff turnover, technicians can learn to use the device in about 5 minutes, he said. The device also has an illuminated control panel so that it can be used without difficulty in darkened examination rooms.