Hyperacuity test to evaluate vision through dense cataracts; research preliminary to a clinical study. II. Initial trials of the India instrument and HASP protocol at Aravind Eye Hospital, Madurai, India.

BACKGROUND. Our purpose is to develop a clinical test capable of assessing vision through dense cataracts (and other advanced media opacities) before surgery. Because such anomalies are endemic in the developing world, it was desirable to conduct a clinical study of a prototype India instrument and HyperAcuity Study Protocol (HASP) in such a setting. This investigation, preliminary to a planned clinical study, was conducted at the Aravind (Free) Eye Hospital, Madurai, India. EXPERIMENTAL. The preliminary HASP protocol, developed in Berkeley, was adapted to existing clinical practices in Madurai. Included was a new test of visual acuity, the Gap "VA" test, developed as part of the revised protocol. The rational for this test, methods used, and sample data are presented. A Vernier alignment test (one of the hyperacuities) is used to assess vision through dense ocular media disorders. The task of the patient is to align vertically three high luminance, discrete visual stimuli. The revised HASP protocol and adapted India instrument were tested upon patients with advanced cataracts. The cataract grading system used in these studies (provided by Drs. N. V. Projna and G. Rohini) is defined. Patients were tested before and shortly after surgery. This investigation allowed us to refine the test protocol and instrument design preparatory for a clinical study of HASP. A much simpler/cheaper version of the India instrument will be used in the planned clinical study. Additional experiments are scheduled in order to address issues which require resolution before initiation of next-stage testing. In part, in these papers, we seek to help others understand some problems encountered when conducting research in a developing world environment, even a very good one!