Topographic Mapping Of The Ocular Fundus By Laser Contour Angiography : The Man-Machine Interaction

Jerrold M. Shapiro

doi:10.1117/12.956954

29 July 1980 Topographic Mapping Of The Ocular Fundus By Laser Contour Angiography : The Man-Machine Interaction

Jerrold M. Shapiro

Proceedings Volume 0166, NATO Symposium on Applications of Human Biostereometrics; (1980) https://doi.org/10.1117/12.956954
Event: NATO Symposium on Applications of Human Biostereometrics, 1978, Paris, France

Abstract

Laser contour angiography is a new technique which was developed by the author for topographically mapping the retina and optic nerve head of the eye. A striped pattern of laser light is projected onto the ocular fundus through one side of the patient's dilated pupil. Photographs, taken through the opposite side of the pupil, reveal the topography as parallactic displacements of the stripes. A topographic map is constructed from tracings of the stripes. The method was shown to produce highly reproducible maps. In order to further improve the reproducibility of the topographic measurements, the effects of the man-machine interaction during the stripe tracing process on measurement error were investigated. The tracing strategy of the operator is to estimate the position along the edge of a stripe at which the perceived light intensity is halfway between the local maximum and minimum. The relationship of errors in the estimates of position to those in perceived intensity was established using a theoretical model. The predictive ability of the model was tested using repeated measurements on the laser contour angiogram of a human eye. The model predicted a position error (standard deviation) of 4.3 micrometers. This agreed remarkably well with the experimental result of 4.5 micrometers. The results indicated that film grain noise and defocussing of the projected pattern are the primary contributors to measurement error. We now use a finer grain film, and have further reduced the position error to 3.4 micrometers.

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Jerrold M. Shapiro "Topographic Mapping Of The Ocular Fundus By Laser Contour Angiography : The Man-Machine Interaction", Proc. SPIE 0166, NATO Symposium on Applications of Human Biostereometrics, (29 July 1980); https://doi.org/10.1117/12.956954

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