A new imaging system using six different wavelengths to illuminate the interior of the eyeball (ocular fundus) may pave the way for doctors to easily screen patients for common diseases of the eye, such as age-related macular degeneration (AMD) and diabetic retinopathy.
The system is described in the journal Review of Scientific Instruments, published by the American Institute of Physics.
Currently, when optometrists and ophthalmologists visualise the ocular fundus, they typically take snapshot images of the eye in two or three wavelengths (red, green and blue), which can reveal some visually-apparent abnormalities.
But an added dimension made possible with the imaging system described by Nicholas L. Everdell, of University College, London, allows doctors to distinguish between the different light absorbing characteristics of biological molecules called chromophores.
According to the paper’s co-author, Iain Styles of the University of Birmingham, five of these light-absorbing compounds are prevalent in the eye: retinal hemoglobins, choroidal hemoglobins, choroidal melanin, RPE (retinal pigment epithelium) melanin, and macular pigment. In a separate paper (Medical Image Analysis 10 (2006) 578-597), Styles said that each of these has been shown to give rise to distinct variations in tissue coloration that can be discriminated in multispectral images.
In the new work, Everdell and Styles describe a device combining a high-sensitivity CCD camera with wavelength-specific illumination from LEDs (light-emitting diodes) that provides multispectral images of the ocular fundus.
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