Depth Maps From Stereo Images of the Optic Disc-Phase II

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It is estimated that 3 million Americans have glaucoma,and 67 million peopleworldwidewill have glaucomaby2005. At least half do not know they have it because glaucoma usually has no symptoms in the early stages. Current research is aimed at developing methods of early diagnosis to detect the disease in the early stages, when treatment is most effective in minimizing irreversible vision loss. The identification of early pathologic changes at the Optic Nerve Head (ONH) is crucial to the diagnosis of glaucoma. The current gold standard for measuring these changes is through clinical stereoscopic observation of the ONH. From the American Academy of Ophthalmology (AAO) 2000, "Previous studies have found that the diagnostic precision of qualitative evaluation of stereoscopic ONHphotographs by experienced clinical observers is superior to any other currently available method of optic disc assessment" (Identifying Early Glaucomatous Changes, Wollstein, Health, 2000 AAOO). The major drawback to the stereoscopic evaluation is the subjectivity that creates inter- and intra-reader observer variability. A new method for evaluating the stereoscopic photographs is needed for consistent analysis of the changes on the ONH. This can be brought about by the use of quantitative analysis of the ONH changes. The Phase I project demonstrated a technique for calculating 3-dimensional topology of the ONH based on a pair of stereoscopic images. High correlations (> 0.9) between the manually annotated cup and disc and the automatically generated iso-disparity contours was documented. The principal aim of Phase II is to validate the technique by performing correlations with multiple readers and with existing clinical instruments such as the Heidelberg Retina Tomographer (HRT), and GDx Nerve Fiber Analyzer. The disparity algorithm's accuracy will be evaluated based on a phantom in the form of a model retina which has been machined with precise optic disc-like features. Such phantoms are used in radiology to calibrate tomography equipment. A second aim of the Phase II is to develop an interface for the use of the algorithm and to be tested in a clinical environment to demonstrate the software as a commercial grade product. Data for testing and validation will consist of traditional stereo fundus photography, digital stimultaneous photography, GDx nerve fiber analyzer, HRT,Goldman and Humphrey visual fields, and Inter Occular Pressure.