Methods and Apparatus for Improved Visualization of Choroidal Blood Flow and Aberrant Vascular Structures in the Eye
There is very little information about the blood flow through capillary plexuses which occurs on the time scale of the cardiac cycle. In part this is because direct visualization of such plexuses usually is technologically difficult or impossible, and most blood flow measurement methodologies require that data be obtained over many cardiac cycles. Moreover, when the capillary plexuses have complex vascular geometries and are fed by many arterioles, the additional problem of sorting-out blood flow distributions arises. One example of a capillary plexus is that found in the cerebral cortex. Another example, of great interest to scientists studying the eye, is the choriocapillaris, one of three blood vessel layers of the choroid.
A method for visualizing the choriocapillaris of the eye in a sequence of ICG angiographic images comprising subtracting each image in the angiographic sequence from a succeeding image. In practice, a modified fundus camera is used to provide digitized images, which are subtracted pixel by pixel. To better visualize aberrant vascular structures such as choroidal neovascularization (CNV), a fundus camera is modified with a polarizing filter in front of the light source and an analyzing polarizer in front of the video camera. This results in the suppression of unwanted scattered fluorescence to the extent that the CNV can be better visualized. To assist the surgeon in treating aberrant vascular structures with laser photocoagulation therapy, a fundus camera is provided with two light sources and two barrier filters operating synchronously to produce and pass two different fluorescences thereby generating precisely superimposable angiographs to aid in aiming the laser.
Patent Status: U.S. patent(s) 5,394,199 issued. International patents issued.
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