Abstract
Abstract: :
Purpose:To develop a method for predicting the manifest refraction, from objective measurements using wavefront sensing. We test the hypothesis that when the eye is at the optimal refractive correction, the quality of vision is at the most stable state, with the least amount of fluctuation and hence least amount of standard deviation (STDEV) in the wavefront total RMS error. Methods:Five (5) patients were enrolled for this study, age from 33 to 55, all male. All measurements were performed using a non–Hartmann Shack, grating–based wavefront instrument (Ophthonix, Inc., San Diego, CA.). The test procedure involves adding defocus power binocularly in the line of sight of the patient. Five (5) diopter powers were used for the study: plano (no add), +1.00 diopter, +0.50 diopters, –0.50 diopters and –1.00 diopter. The complete data set for each patient was taken in 5 sessions. Only the right eye of each patient was used for the study, and the eyes were undilated. The measurement was repeated for a different defocus power at different times and different days over a period of a week. With this particular wavefront instrument, the patient had a binocular view and was asked to focus on a picture at 20 feet. The patient’s manifest refraction is used as the reference point for all later tests (the +/– added powers are relative to this "plano" power). For each patient, the STDEV is calculated from wavefront data when patient is viewing the target through the added diopter power. Results:From graphic plots of STDEV of the total RMS against the added diopter power, data from four out of the five patients show a minimum at the plano power position. One patient (DR) has a minimum between plano and +0.50 diopters. Patient (CM) shows a drop off of the STDEV when he was fogged at 1.0 diopter. Conclusions:Even though we have a limited sample size, data from all five subjects support the hypothesis put forth in this paper. The method predicts that the manifest power position is at the subjects’ most stable vision in terms of wavefront changes. The hypothesis suggests that by measuring the fluctuation of the quality of vision, one may virtually "tap" into the subjective response of the patient, using objective measurement, without verbal response from the patient.
Keywords: refraction • refractive surgery