Myopia control spectacle lenses have varying sagittal power and consistent curvature power from lenslet to lenslet, according to research published in Ophthalmic and Physiological Optics. This lenslet arrangement determines image characteristics, and the blur created by the fragmented base optic contributes to the image quality, according to the report.
Investigators from the Indiana University school of optometry examined 2 novel myopia control spectacle lens designs — 1 with defocus incorporated multiple segments (DIMS) and 1 with highly aspheric lenslet technology (HALT) — with plano power using an aberrometer and an experimental 4f optical imaging system. The team determined optical power, point-spread functions (PSFs), and modulation transfer functions (MTFs), which were calculated using PSF-derived optical transfer functions.
The design using DIMS included 9 hexagon lenslets while the lens with HALT had 11 ring lenslets. Dioptric power was assessed in 1 lenslet per lens, but others were evaluated to confirm consistency. Both lens designs had lenslets with similar half-width at half-maximum sizes (0.45-0.46 mm). The measurement areas were centered in hexagon 3 of the lens with DIMS and ring 2 of the lens with HALT. As such, the focal planes were located 4.00 diopters (D) and 6.00 D anterior to the distance of the focal plane for the DIMS and HALT lenses, respectively.
Overall, the average lenslet power was 3.95 D for the DIMS hexagons. For the lenses with HALT, the first 5 rings had a mean power of 6.00 D. Each subsequent ring decreased in power by 0.42 D and the final ring had a power of 3.50 D.
The PSF assessment indicated that the base optics and lenslets simultaneously contributed to the point spread.
During MTF assessment, a decrease in contrast comparable to 0.25 D was observed at low spatial frequencies.
“The present study examined imaging characteristics of two myopia control spectacle lenses by means of different approaches […],” according to the researchers. “Novel and complex spectacle optical designs call for the use of different techniques to explore their characteristics and performance in optical myopia treatments.”
Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
Gantes-Nuñez J, Jaskulski M, López-Gil N, Kollbaum PS. Optical characterisation of two novel myopia control spectacle lenses. Ophthalmic Physiol Opt. Published online February 4, 2023. doi:10.1111/opo.13098