Abstract
Purpose :
The traditional lensmeter is an important piece of equipment for determining ophthalmic lens power. It is, however, often bulky and expensive, which could be inconvenient to use in vision screenings. This study investigated the validity of a smartphone-based lensmeter with a simple and low-cost design, with the aim to allow for easy application outside clinical settings.
Methods :
A smartphone camera was mounted close to a lens holder where single-vision ophthalmic lenses were placed. A custom-made double-ring target was placed and captured by the camera from above. Full-aperture trial lenses with a rim diameter of 38 mm ranging from -10.00 D to +5.00 D (with a refractive index of 1.53) were used to establish the relationship between spherical lens power and the magnification/minimization of the image size. Subsequently, the accuracy of measuring spherical lens power with refractive indices of 1.50, 1.56, and 1.67, and plano-cylindrical lens power (-0.25 DC to -5.00 DC) with a refractive index of 1.53 were evaluated by comparing with standard digital auto-lensmeter measurements.
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Results :
A high correlation was found between the spherical lens power and the magnification/minimization of image size (R2=0.99). Based on this correlation, the refractive power of the ophthalmic lens made from different refractive indices was estimated using the equation. When compared with the results obtained from digital auto-lensmeter, the mean difference (mean ± SD) in spherical power was less than 0.25 D (-0.18 ± 0.13 D for plus lenses; +0.18 ± 0.25 D for minus lenses). Similarly, the mean difference of cylindrical lens power was 0.29 ± 0.21 DC. Bland-Altman plots showed no consistent bias and indicated good agreement between the smartphone-based lensmeter and the digital auto-lensmeter in measuring lens power for both spherical and cylindrical lenses.
Conclusions :
This study suggests that the lens power determined by the smartphone-based lensmeter and the digital auto-lensmeter is comparable. The smartphone-based lensmeter may be a reliable tool to verify lens power for vision screenings and clinics in remote rural areas and urban underserved communities.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.