Instant vision assessment device accurately measures refraction in low vision patients
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There was no statistically significant difference in mean visual acuity or mean spherical equivalent refraction in low vision patients when measured by instant vision assessment device vs. subjective refraction, according to a study.
In a cross-sectional study of low vision and normal vision individuals published in Clinical and Experimental Optometry, Desmond Cheng, OD, MSc, PhD, of the School of Optometry at Hong Kong Polytechnic University, and colleague found that at least 80% of refraction components measured with an instant vision assessment device were within 0.50 D of subjective refraction measurements.
Described as “a stenopaeic slit refraction system in a binocular telescopic optometer calibrated to measure spherical and cylindrical refractive errors,” the device was used to measure refractive error in 35 individuals with normal vision, aged 9 to 69 years, recruited from an eye care clinic at Hong Kong Polytechnic University, and in 20 with low vision, aged 60 to 90 years, recruited from a low vision clinic at the University of Waterloo in Ontario, Canada. One week after the first measurement, subjective refraction was measured in the same individuals for comparison.
Conditions reported in the low vision group included age-related macular degeneration (the most common cause of vision loss in participants), glaucoma, optic neuropathy, diabetic retinopathy and retinitis pigmentosa.
In normal vision participants, the difference in mean spherical equivalent refraction measured with the device vs. subjective refraction was 0.16 D, which was not statistically significant. Similarly, the difference in low vision participants was 0.11 D, also not statistically significant.
Although clinically insignificant, the mean difference in J0 measured by the instant vision assessment device (0.03 D) and by subjective refraction (0.07 D) was 0.10 D, which was statistically significant (P = .04).
For low vision patients, the instant vision assessment device “is a practical and valid refraction method,” the authors wrote.
Perspective
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Many of us encounter patients with low vision in our practices, defined as vision loss that cannot be corrected by medical treatment, surgical treatment or conventional eyeglasses. In these patients a multidisciplinary vision rehabilitation approach improves visual function and quality of life. Correction of refractive error is essential, and trial frame refraction is the standard; however, this article provides insight into another potential method for determining refraction.
Trial frame refraction in patients with visual impairment requires technical skills and appropriate chair time. This study aimed to validate the use of a stenopaeic slit refraction system in a binocular telescopic optometer as a possible alternative when measuring refractive error.
Overall, this device is manipulated by the patient, which could increase access to care, as it does not require a provider to be present for the entirety of the testing. It could be implemented in geographic areas with limited providers and could play a role in telehealth. However, additional studies are needed to validate this device in the low vision population given significant limitations of this study including bias secondary to unmasked investigators and a small sample size. It would also be beneficial to assess the efficiency as compared to trial frame refraction.
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