A continuing clinical need exists to find diagnostic tools that will detect and characterize the extent of retinal abnormalities as early as possible with non-invasive, highly sensitive techniques. The objective of this paper was to demonstrate the utility of a Hyperspectral Fundus Imager and related analytical tools to detect and characterize retinal tissues based on their spectral signatures. In particular, the paper shows that this system can measure spectral differences between normal retinal tissue and clinically significant macular edema. Future work will lead to clinical studies focused on spectrally characterizing retinal tissue, its diseases, and on the detection and tracking of the progression of retinal disease.
A Fourier Transform hyperspectral imager was integrated onto a standard clinical fundus camera, a Zeiss FF3, for the purposes of spectrally characterizing normal anatomical and pathological features in the human ocular fundus. To develop this instrument an existing FDA approved retinal camera was selected to avoid the difficulties of obtaining new FDA approval. Because of this, several unusual design constraints were imposed on the optical configuration. Techniques to calibrate the sensor and to define where the hyperspectral pushbroom stripe was located on the retina were developed, including the manufacturing of an artificial eye with calibration features suitable for a spectral imager. In this implementation the Fourier transform hyperspectral imager can collect over a hundred 86 cm-1 spectrally resolved bands with 12 micro meter/pixel spatial resolution within the 1050 nm to 450 nm band. This equates to 2 nm to 8 nm spectral resolution depending on the wavelength. For retinal observations the band of interest tends to lie between 475 nm and 790 nm. The instrument has been in use over the last year successfully collecting hyperspectral images of the optic disc, retinal vessels, choroidal vessels, retinal backgrounds, and macula diabetic macular edema, and lesions of age-related macular degeneration.
The goal of this study was to determine the utility of red, green and blue color information in segmenting fundus images for two general categories of retinal tissue: anatomically normal and pathological. The pathologies investigated were microaneurysms and dot blot hemorrhages.
An optical imaging device of retina function (OID-RF) has been developed to perform measurements of changes in blood perfusion due to neural activity resulting from visual stimulation of the photoreceptors in the human retina. Experiments were performed by measuring the changes in reflected long wave visible (700 nm) light from the retina caused by the retinal activation in response to a visual stimulus. The problem being addressed is that of detecting the signal from the retinal activation in the presence of noise from other sources, including the unstimulated retinal background and other unknown physiological changes. Preprocessing of the raw data was done to eliminate unwanted artifacts, such as blinking or excessive eye movement. Principal Component Analysis (PCA) was used to isolate the functional signal. The results of the analysis showed that regions of the retina that were stimulated could be detected using PCA.
