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Shui T Lai; Comparison of two methods for performing subjective refractions. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2720.
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To determine if a new method for performing subjective refractions, using point spread function (PSF) provides a more accurate refraction while reducing the time taken to complete the exam. A secondary purpose of the prospective study was to determine if patients benefitted from a subjective refractive exam under nighttime vision conditions.
None, randomized, prospective comparison of speed of subjective refraction, as well as refraction obtained in 8 patients who presented for a routine visual examination in a private optometric practice. The eight patients underwent a subjective refraction first with a standard phoropter, followed by a subjective refraction with a system that utilizes point spread function for the visual target (PSF Refractor, Vmax Vision, Maitland, FL). A third exam was then performed using a nighttime target to assess any differences in the manifest refraction. All exams were performed by the same person. The amount of time for each exam was recorded, as well as the manifest refraction and visual acuity obtained. Patient subjective response to the exam was also recorded.
The mean age of patients included in this study was 25.75 (range, 16 to 38). No patients had any pre-existing ocular diseases or had undergone refractive surgery. In a head-to-head time comparison, the PSF refraction system yielded a substantially quicker refraction by almost 2-to-1: Phoropter exam: average of 2.14 minutes per eye compared to an average of 1.19 minutes with the PSF device. The fastest exam times were achieved using the nighttime visual targets with an average exam time of 58 seconds per eye. On average, there was not a significant difference between the refractive measurements obtained. All patients indicated that they found the PSF subjective refraction fast than the phoropter refraction.
The use of a subjective refraction device that uses PSF targets rather than Snellen letters results in substantially quicker exam times, while not reducing the accuracy of the manifest refraction and visual acuity that is obtained. The use of nighttime visual targets enables clinicians to develop a thorough understanding of the patient’s visual performance to determine if nighttime vision issues are reducing quality of vision.
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