Microcomputer applications in retinal research

Assessment of angiographic retinal capillary nonperfusion in central retinal vein occlusion

We studied the reproducibility and accuracy of eight retinal specialists in assessing the extent of retinal capillary nonperfusion on fluorescein angiograms of 26 central retinal vein occlusions. Each specialist was asked to classify the retinal capillary perfusion status on every angiogram as nonischemic, minimally ischemic, moderately ischemic, markedly ischemic, or uncertain. Criteria for classification of each angiogram were specified in advance for each reviewer. Each examiner individually reviewed every angiogram on two separate occasions separated by at least one month. Intraexaminer and interexaminer reproducibility were both substantially better than the agreement predicted by chance alone (P less than .05); however, the proportion of agreement with the correct classification was less than 60% for all eight specialists.

Microcomputer applications in pathology research

In a study of over 700 cases of uveal melanoma on file in the Department of Pathology of Wills Eye Hospital, a low-cost microcomputer using commercially available software (without modification) was used to: word process and edit this manuscript, create a patient file storage and retrieval system including the ability to create subfiles, merge files, and interchange file types, plot data points in several different graphic formats, transcribe and store information from microscopic tissue sections containing intraocular melanomas, and solve complex equations including statistical analysis. The results showed that over 150 different ophthalmologists contributed specimens to this data base. The mean age of the patients studied was 57 years and the tumors were evenly distributed according to sex and laterality of the eye. This study illustrates the feasibility of using a low-cost microcomputer and commercially available software in the study of a large patient data base.

Retinal ischemia and risk of neovascularization following central retinal vein obstruction

The predominant risk factor for the development of neovascular complications involving the retina (NVR), the optic disc (NVD), and iris (NVI) following central retinal vein obstruction (CRVO) is the extent, location, and duration of retinal ischemia (ischemic drive). The extent of retinal capillary nonperfusion (ischemic index) was quantitated by microcomputer analysis of 200 standard fundus-iris fluorescein angiograms. The results were correlated with the development of neovascularization in eyes not receiving prophylactic argon laser panretinal photocoagulation (PRP). Of the 85 eyes with intact capillary perfusion (hyperpermeable group), none developed NVR/NVD and only one eye (1%) developed neovascular glaucoma (NVG). Twenty-nine eyes exhibited moderate degrees of retinal ischemia (indeterminate group), and three eyes (10%) developed NVR/NVD, with two eyes (7%) developing NVG. Of the 86 eyes with extensive retinal capillary nonperfusion (ischemic group), 28 eyes (33%) developed NVR/NVD and NVG occurred in 39 eyes (45%). The inherent difficulties in following high risk patients clinically and angiographically at frequent intervals over extended periods of time, the tendency for rapid progression of early NVI to NVG, and the relatively poor results following treatment in advanced cases make the early recognition of eyes at high risk to develop NVG essential and the initiation of prophylactic PRP as the treatment of choice in this disorder.

Efficacy of panretinal photocoagulation in preventing neovascular glaucoma following ischemic central retinal vein obstruction

Ninety-three percent of eyes that develop neovascular glaucoma (NVG) following central retinal vein obstruction (CRVO) have an ischemic index greater than 50%. An ischemic index (percentage of retinal capillary nonperfusion) of 50% represents approximately 10 disc areas of retinal ischemia as determined by computer analysis of standard 30 degrees fluorescein angiograms. The difficulties of following patients clinically and angiographically at frequent intervals over extended periods of time, and the tendency for iris neovascularization (NVI) to develop and to progress rapidly to NVG with painful loss of vision emphasizes the importance of early recognition and treatment of high-risk eyes. In this prospective study (1976--81), 100 consecutive eyes with an ischemic CRVO pattern (average ischemic index 82%) received early argon laser panretinal photocoagulation (PRP) and none developed NVG unless another ischemic event occurred following treatment. Prophylactic PRP in high-risk ischemic CRVO eyes appears to eliminate virtually the devastating complications of NVG.