Multispectral imaging screens for eye diseases

A new multispectral imaging system uses six wavelengths to illuminate the interior of the eyeball (ocular fundus), potentially paving the way for doctors to easily screen patients for common eye diseases such as age-related macular degeneration and diabetic retinopathy.

Currently, when optometrists and ophthalmogists visualize 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 and colleagues at University College London and the University of Birmingham allows doctors to distinguish between the different light absorbing characteristics of biological molecules called chromophores.

In the new work, the researchers describe a device combining a high-sensitivity CCD camera with wavelength-specific illumination from LEDs that provides multispectral images of the ocular fundus. The system consists of a Zeiss RCM250 ocular microscope, custom LED light source, and 35-mm SLR camera back with a Hamamatsu C9100-13 back-illuminated EMCCD camera controlled by an Active Silicon PHX-C24CL frame grabber.

The system can acquire a sequence of multispectral images at a fast enough rate (0. 5 seconds) to reduce image shifts caused by natural eye movements. In contrast with snapshot systems, the system's images retain full spatial resolution. Also, the system uses only the specific wavebands that are required for the subsequent analysis, minimizing the total light exposure of the subject, ensuring patient safety and improving image quality.

According to the researchers, the long term goal is to develop a system for chromophore quantification that is an integral part of the standard fundus camera, and therefore could be used routinely by both optometrists and opthalmologists.

SOURCE: Multispectral Imaging of the Ocular Fundus using LED Illumination by Nicholas Everdell, Iain B. Styles, Antonio Calcagni, Jonathan Gibson, Jeremy C. Hebden, and Ela Claridge will appear in the journal Review of Scientific Instruments, published by the American Institute of Physics.

Posted by Vision Systems Design