Abstract
Purpose: :
To compare the refractive correction of vision in hyperopes using standard manifest refraction (MR) to the FirstSight Refraction (FSR) System; a portable refraction and lens-frame dispensing system with low cost of production and accessible materials for potential use in remote areas with little or no access to equipment for standard refraction and refractive error correction.
Methods: :
Forty-one subjects 18 years and older underwent autorefraction (AR) and uncorrected visual acuity (UCVA) testing using the ETDRS chart. A single examiner, blinded to the AR results, performed and recorded standard phoropter manifest refraction (MR) and best corrected visual acuity (BCVA) using trial frames. Examiners blinded to both AR and MR results performed screening and refraction using the FSR system. UCVA was measured using a "Tumbling E" chart at 20 feet. A FSR trial Lens flipper with +0.5 D and -0.50 (and +1.00 and - 1.00 D) lenses was used to determine if the patient has grossly myopic or hyperopic. Subjects determined to be hyperopic underwent testing with FSR lenses organized into a hyperopic lens bar in +0.50 D increments. FSR lens power was determined by improvement in VA. If the subject read a Snellen Equivalent of 20/25 or better the correcting lens was recorded. If the subject read 20/30 or worse, FSR astigmatism kit screening was performed. Adjusting for spherical equivalent, FSR astigmatism lenses were "dialed-in" to the correct astigmatism axis to obtain BCVA. The corresponding lenses were placed in the appropriately sized FSR Frames and BCVA using ETDRS chart was recorded. Autorefraction, MR, and FSR results were compared using repeated measures ANOVA. T-test was used to compare BCVA results of MR and FSR. Tukey test post hoc test was used to further compare AR, MR and FSR.
Results: :
Fifteen eyes from 11 subjects had hyperopic spherical equivalents on MR. Spherical equivalent (mean ±SD) by AR was +1.55±1.86 D, MR +1.43±1.81 D, and FSR +0.48±1.73 D (repeated measures ANOVA p = 0.002). Spherical equivalent of refractive correction obtained using FS was significantly lower than either MR or AR (Tukey post hoc test). The Logmar BCVA among hyperopic subjects with MR was 0.09 ± 0.41 compared to 0.20 ± 0.51 with FSR (Wilcoxson p value = 0.002).
Conclusions: :
FSR system underestimated refractive error by approximately 1 diopter in subjects with hyperopia. BCVA obtained using the FSR system was one line worse than MR. The FSR system demonstrates potential for use in remote areas with little access to equipment necessary for standard manifest refraction but an increase in the number of hyperopia correction lens options is needed.
Keywords: refraction • hyperopia • astigmatism