instrument focus

Getting to the Point

Point-spread function brings new dimension to refracting.

DAVID GEFFEN, O.D.

In a world of digitized lenses, precision is key when conducting subjective refractions. Adopting the PSF Refractor from Vmax Vision (Maitland, Fla.), which uses a point-spread function, has allowed us deliver accurate prescriptions for patients measured in increments of 0.05D, and patients have taken notice.

Process

The principles of the point spread function (PSF) allow patients to use a target point and react, given the amount of visual distortion. If you’ve put in too much minus, the patient tells you that the point is blurry, and you back off. Patients can easily detect a change as you perform the subjective refraction.

My practice has the PSF Refractor in one of our exam rooms, and we use it for virtually all patients. The only exceptions being those who go beyond the limits of the device (up to -12.00D with about 5.00D of astigmatism).

Many of our older patients, particularly those who never felt comfortable choosing “one or two,” have appreciated this technology. With the PSF, patients don’t struggle to see whether the image is “right” or “wrong.”

Still, patients have occasionally not responded the way we’d like. These patients have typically been tested via a phoropter for roughly 40 years and are used to traditional methods of refraction.

Accuracy

When dealing with higher order aberrations, we optimize them, not correct them. This has been crucial toward making patients’ vision more crisp at night, particularly for those who have expressed trouble with driving.

Since instituting the PSF device, roughly 90% of our patients use the device, and I’ve never had an issue with overminusing a patient. Because of this, we’ve cut our remakes by roughly 25%. This accuracy has also led to more referrals. Patients are happy with their lenses, and they have expressed this to friends and family.

Delegating refractions

The PSF Refractor has made the delegation of the subjective refraction to technicians a smooth process. I’ve found it has worked best to train someone who doesn’t have previous experience using a phoropter. My new technicians say this a straightforward test, and that they have learned to use it quickly. New technicians have become as proficient as I am in less than two weeks.

Those who have previous phoropter experience carry biases and are accustomed to typical patient responses after years of performing subjective refractions. This can lengthen the learning period. I’ve found these technicians take about five to six refractions per day for at least two weeks to become confident with their ability to use the device.

Return on investment

The PSF device has led to efficiencies in patient exams and workflow. In my practice, it takes roughly three minutes to perform the subjective refraction with the PSF device compared with five minutes with a standard phoropter. In a busy clinic with 50 patients scheduled in a day, this can save almost two hours of exam time.

My practice prides itself on being on the cutting edge of technology. Using the PSF Refractor has differentiated our practice, and my patients and I have been impressed. OM

DR. GEFFEN PRACTICES AT THE GORDON WEISS SCHANZLIN VISION INSTITUTE WHERE HE SPECIALIZES IN FAMILY EYECARE, CONTACT LENSES, LOW VISION AND REFRACTIVE SURGERY CONSULTATIONS. SEND COMMENTS TO OPTOMETRICMANAGEMENT@GMAIL.COM.