PSF technology shows promise

La Jolla, CA-A new point spread function (PSF)-based refraction system (PSF Refractor, VMax Vision) has been found to be a useful tool that provides better or equal accuracy and reliability in refractive endpoints, according to a study presented by Alison Gordon, MD.

The study, a multicenter clinical study designed to assess initial user experiences with the new refraction system, also found that the PSF refractor had a higher patient acceptability compared with a standard phoropter, said Dr. Gordon, private practice, Gordon-Weiss-Schanzlin Vision Institute, La Jolla, CA.

The study enrolled 900 patients at five clinical sites. Patients had a standard manifest refraction performed using the PSF refractor and a phoropter.

Patient and clinician satisfaction were also assessed using a Likert scale to rate such variables as speed of exam, ease of use, fatigue, and ability to respond confidently.

Compared with the standard phoropter manifest refraction, the PSF refractor provided equal or better visual acuity results: 67% of patients had better visual acuity results with the PSF refractor and 33% had equal results with the two techniques.

None of the 900 patients had a better refraction with the phoropter, Dr. Gordon said.

Patient preference ratings showed a strong trend in favor of the new refractor, with 90% of patients reporting that they liked undergoing the refraction better with the PSF device and only 3% liking the phoropter better.

“This new device using PSF offers the potential for more accurate subjective refractions in less time than with a standard phoropter,” Dr. Gordon said. “Changes in the specific targets are easier for patients to detect-the average refraction time is just 90 seconds, and the testing works well in complicated eyes, such as those with age-related macular degeneration or keratoconus.”

The system is also easy to adopt, she said.

“Technicians can get the feel of how to do the test properly after only 2 hours of training and conducting testing in about 10 patients,” Dr. Gordon said.

However, the PSF refractor can be sensitive for 0.05 D increments of myopia or hyperopia across the range from -17 to +20 D, which is 5-fold better than that of a standard phoropter, she said.

 The sensitivity of the PSF refractor for cylinder correction is in increments of 0.03 D over the range from -6 to +6 D and in 0.2° increments for axis.

Dr. Gordon has no financial interest in the product she discussed.

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