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Click here to download a PDF of Refraction Revisited.

Even as eyecare professionals acquire ever more sophisticated diagnostics that enable them to evaluate the corneal surface (corneal topography) and the retinal and macular layers (optical coherence tomography), the refraction still remains the centerpiece of the comprehensive eye exam.

And technology to perform both the objective and subjective refraction has kept pace with advancements in digitization, automation and interoperability with other devices in the exam lane and the electronic medical record. That has meant more accurate measurements of refractive errors and faster exams. Whereas the traditional, manual phoropter can measure to within 0.25D of refractive error, newer digital technologies can achieve measurements to within 0.05D.

“Digital refraction is not only here to stay but it is the future,” said Paul Karpecki, OD, FAAO, a prominent optometric practitioner, educator and author who serves as clinical and education conference advisor for Review of Optometry.


“Technology has simply caught up to where manufacturing more precise lenses is now possible. The idea of a 0.25D difference isn’t always the lowest resolution for all patients. There are many patients that actually have a refraction that may be –3.00-0.75 x 180 but the majority will have something like –3.10 –0.38 x 112 and therefore more refinement via digital refraction systems is valuable to that patient. These new systems that include point spread function resolution and other advances are changing the landscape and providing better vision to a large subset of patients.”

Recently, two technologies have emerged that offer new options for patients who want the flexibility of having a refraction done in their home, or conceivably, anywhere, either by the patient themselves or with the assistance of a practitioner: online refraction and smartphone-based refraction. These technologies are raising questions among some eyecare professionals about the accuracy of a prescription that skips a full subjective refraction at a phoropter or a phoropter-like device. Online refraction is particularly contentious, and has drawn the ire of optometrists who believe a self-administered vision test does not provide adequate patient care.

This article, together with VM’s July, 2014 cover story, “Refraction Reboot,” offers an overview of current refraction technologies designed for in-office or mobile use.