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Jennie Weinkle, Cameron Pole, Benjamin Thomas, Joyce Schiffman, Wei Shi, Richard K Lee; A method for patient self-refraction and on-site eyeglass assembly. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2713.
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Refractive error is a leading cause of visual impairment worldwide that can be largely avoided with non-invasive, inexpensive treatment with eyeglasses. Based on WHO data from 2012, approximately 285 million people experience visual impairment (visual acuity (VA) < 20/60 in the better eye); refractive error is the primary cause in 43% of cases. Yet, only 20% of people have access to refractive correction, with the greatest lack of access in the developing world. Access to refractive services could be improved with portable devices, teaching basic self-refraction techniques, and low-cost frames. The I-test Vision Screener is a manual self-refractor device used to measure refractive power. Our purpose is to evaluate patients’ ability to self-refract using the I-test compared to professional refraction, and compare the subsequent VA outcomes between ready-made spectacles and best-fit donated spectacles.
Twenty-three subjects were recruited during visits at the Free Spectacles Clinic at the Bascom Palmer Eye Institute, which provides used glasses that are best fit to a patient's professionally manifest refraction. After explanation of the study and demonstration of the I-test auto-refractor, consented subjects were asked to adjust the lens power for each eye until the clearest image was achieved. The spherical equivalents from the I-test were matched with pre-made spherical lenses inserted into ready-made frames. The patient's VA was measured and then compared to their VA wearing a pair of best-fit glasses from the Free Spectacles Clinic library of over 10,000 donated glasses.
Initial data reveals that 88% of subject’s eyes were self-refracted within 1.0 Diopter of their spherical equivalent using the I-test. The VA using best-fit donated glasses was 0.10 LogMAR units better in the best eye (p=0.003) than with ready-made spectacles.The difference in LogMAR acuity between ready-made and glasses library in eyes with little or no astigmatism (Cylinder ≤0.5 D) is smaller than when all eyes are included: 0.07 LogMAR unit in the best eye (p=0.14) and 0.09 logMAR unit in the worse eye (p=0.35).
Preliminary results show that most patients are capable of using the I-test to measure their refractive error. The VA outcomes with ready-made spectacles give similar (within about 1 line) acuity results to the best-fit donated glasses.
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