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Ran He, Hilary Gaiser, Nadine Solaka, Li Deng, Bruce D Moore; Quality of Functional Vision Through Adjustable Spectacles [FocusSpecs] Phase II. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2712.
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© ARVO (1962-2015); The Authors (2016-present)
Uncorrected refractive error is the leading cause of visual impairment. The use of Variable Focus Lens spectacles (VFL’s) can benefit populations lacking access to refractive eye care. The results of Phase I1 showed that functional vision was similar between AdSpecs VFL’s and habitual correction (HC). The AdSpecs design injects silicone fluid to change lens curvature and power. In Phase II, we evaluate vision through FocusSpecs (FS) VFL’s, which change lens power through two Alvarez-type lenses that move horizontally with respect to each other. Our study provides insight into the functional quality of FS and their level of comfort when worn as corrective devices.
Subjects were 30 adults 22-44 years of age. Distance VA (DVA) was measured at 4M. using a Good-Lite ETDRS chart and near VA (NVA) at 40cm. using a Precision Vision ETDRS near card. Contrast sensitivity (CS) was measured at 50cm. using MARS CS test. Lateral and vertical phoria were measured by Modified Thorington at 40cm. All measurements except DVA were also taken in down gaze (45° below primary gaze) with FS and HC. Subjects also completed a Convergence Insufficiency Symptom Survey (CISS). Inclusion criteria were: Hyperopia +1.50 to +4.50 D, Myopia -0.75 to -5.00 D, Astigmatism <2.00 D, Anisometropia <1.00 D and VA cc ≥20/25 in each eye.
Means of right eye measurements were compared within subjects between the two conditions (HC vs. FS). The difference in DVA means was -0.079±0.12 logMAR, p = 0.0017 (HC = -0.097 logMAR, FS = -0.017 logMAR). The difference in NVA means was -0.061±0.085 logMAR, p = 0.00043 (HC = -0.12 logMAR, FS = -0.06 logMAR). The difference in CS means was 0.011±0.026 log CS, p = 0.030 (HC = 1.80 log CS, FS = 1.79 log CS). The difference in lateral phoria means was -0.28±1.34 PD, p = 0.26 (HC = -2.42 PD, FS = -2.13 PD). The difference in vertical phoria means was 0.017±0.16 PD, p = 0.57 (HC = 0.017 PD, FS = 0 PD). The difference in CISS means was 1.77±9.24, p = 0.30 (HC = 13.47, FS = 11.70).
VA and CS were slightly reduced through FocusSpecs. This may be due to the FS multiple-lens design and inherent power error. These differences were not considered clinically significant and would not substantially impair functional vision. Means of phoria and CISS were similar between HC and FS. This suggests that FocusSpecs can potentially serve as a screening tool in the developing world.
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