Comparative Evaluation of Subjective Point-Spread Function Refraction Results With Subjective Phoropter Results on Keratoconus Patients
Purpose
To evaluate whether a different refraction method, in this case, point spread function refraction, can provide more reliable and accurate endpoint in keratoconus patients when compared to phoropter results.
Methods
A comparative study of 14 patients (28 eyes), refracting patients first with a standard phoropter, and then using a PSF (point spread function) Refractor. For the PSF refraction, patients were asked to look at a single target with a bright point (which is totally symmetrical), while various optical powers of sphere and cylinders were presented to the patient. Subjective responses were required to ensure a reliable endpoint using both patients’ eye optics and its neural processing of the brain. Visual acuity was recorded using EDTRS eye charts.
Results
Mean SE was -4.38±5.55 D (range: −16.25 to +2.00 D) in the Phoropter group, and −4.55±6.64 D (range: −18.63 to +2.46 D) in the PSF group. The accuracy of the data was assessed by comparing the best-corrected VA. To set a level of standard and maintain accuracy, we considered 3 letters or less to be equal. Two eyes were excluded from the data set because they did not meet the inclusion criteria. Of 26 eyes, 18 eyes achieved higher level of VA using the PSF refraction than that of Phoropter. The 8 remaining eyes achieved an equal level of VA.
Conclusion
Using a new point spread function method to refract produces a more reliable and accurate refraction outcome in visually challenged patients such as keratoconus and cataracts. It is easier for the patient and provides the best corrected visual acuity when compared to a Phoropter.