Principles of Ray tracing aberrometry

PURPOSE: Of all transforms of an eye, aberrations are significant when high er visual acuity is to be achieved. Ray tracing aberrometry developed by th e Institute of Biomedical Engineering (Kiev) and first tested at the Vardin oyannion Eye Institute of Crete is a promising technique for eye refraction aberration and refraction mapping. METHODS: The technique uses measurement of the position of a thin laser bea m projected onto the retina. The beam is directed into the eye parallel to the visual axis. Each entrance point provides its own projection on the ret ina. A set of entrance points forms a set of projections. From these data, a refraction map is reconstructed as well as a point spread function of the eye, The total time of scanning over the whole aperture of the eye is with in 10 to 20 ms and depends on the number of test points at the eye entrance , as well as on the number of independent measurements in each point. Confi guration of the scanning pattern can be chosen by the operator. It may cont ain 60 to 400 points, each checked 1 to 5 times. RESULTS: Preliminary studies showed high reproducibility of results, Twenty pseudophakic eyes were subjected to 30 consecutive measurements each. Nine ty-five percent of all measured values were within +/-0.20 D of declination from the mean. CONCLUSIONS: Ray tracing aberrometry is a flexible technology for eye inves tigation. It can be adapted to any laser technique of vision correction its further development should be oriented on laser-linked applications of the refraction driven refractive surgery.