Optical characterisation of spectacle lenses for myopia control

Abstract

Myopia is the most common ocular disorder worldwide and the leading cause of visual impairment in children. Its progression affects the normal retinal development, increasing the risk of suffering severe ocular pathologies that lead to irreversible blindness. Although the mechanism for myopia progression is not completely elucidated yet, it is suggested that the quality of the peripheral retinal images may play a role. This produced an enormous interest in using spectacle lenses with different focusing properties for foveal and peripheral vision as a treatment to slow myopia progression. In this work, we developed a novel instrument to optically characterise spectacle lenses designed for myopia control under realistic viewing conditions. First, the testing beam impinges the spectacle under test with different eccentricities. For each eccentricity, a steering mirror guides the beam towards a liquid crystal spatial light modulator (SLM). The SLM allows for reproducing several pupil sizes, shaping the pupil according to the eccentricity, reproducing ocular aberrations for different levels of myopia, and acquiring the through-focus point spread functions (PSFs). An electrically tunable liquid lens, conjugated to the SLM, compensates the base power of the tested lens and focuses the beam into a camera’s sensor. Three spectacle lenses were tested, and different optical metrics were calculated from the PSF and the modulation transfer function.