CASNET: a glaucoma model before ophthalmologists
At IJCAI-77 in Cambridge (22-25 August 1977) S. M. Weiss, C. A. Kulikowski and A. Safir described CASNET, a program for the long-term management of glaucoma that reasons through a causal network of disease states. At the 1976 meeting of the American Academy of Ophthalmology and Otolaryngology 49 ophthalmologists rated its advice: 95% found it clinically acceptable, 77% expert or very competent.
Why it matters
A medical program's advice was rated by a large group of ophthalmologists, not only by its builders. The program rests not on a list of rules but on a model of the disease's course from pathophysiological states to findings, and the authors themselves contrast it with MYCIN's purely normative, rule-based approach.
The model describes glaucoma as a network of pathophysiological states joined by causal links and ties observations, diagnoses and treatments to them; the advice concerns long-term management. The program is written in FORTRAN and runs in 35K words of memory on a PDP-10. Since 1975 researchers at five medical centres, joined in the ONET network, had been testing it; it has over 200 diagnosis and therapy statements. On an early sample of 40 difficult cases the model, as it improved, came to diagnose all 40 correctly. The ONET members estimate, by personal communications the paper cites, that the program reaches reasonable and often sophisticated judgments in about 75% of difficult cases. The 1976 survey table: expert 25%, very competent 52%, acceptably competent 18%, inadequate 5%. Weiss and Safir were at Mount Sinai School of Medicine, Kulikowski at Rutgers University. What the record does not claim: the day of the 1976 survey, which the paper does not give; figures from the 1978 journal paper, which adds Amarel as an author and was not read. The figures come from the re-typeset text of the proceedings, not from a scan of the print.