Accommodation-Induced Higher Order Aberrations Observed in Pediatric Myopia

Accommodation-induced higher order aberrations and retinal image quality deterioration may explain myopia development and the association between near work and accommodation, according to research published in Ophthalmic and Physiological Optics.

Researchers included 18 children with myopia (mean age, 10.1 years; 11 boys; mean spherical equivalent refraction [SER], −2.08 diopters [D]) and age- and sex-matched participants without myopia (n=18; mean age, 10 years; mean SER, +0.63) in the investigation to explore accommodation-induced higher order aberrations and retinal image quality changes in children with different refractive errors. The team measured ocular higher order aberrations using a wavefront sensor during 4 accommodative demands (0, 3, 6, and 9 D) and used eighth order Zernlike polynomials, which were fitted on a 2.3 mm pupil diameter, to determine refractive power vectors and the accommodation error. The researchers also examined retinal image quality using the visual Strehl ratio based on the optical transfer function (VSOTF) for third to eighth radial orders only.

The greatest differences between participants with myopia and individuals without myopia were observed for the 6 and 9 D demands, the report shows. In children with myopia, with-the-rule astigmatism, higher order and third order root mean square values, primary vertical and horizontal coma, and several other individual Zernike coefficients experienced greater changes compared with children who did not have myopia (P ≤0.02 for all). The VSOTF degraded at the 9 D demand in both groups, and was reduced more significantly among children with myopia compared with control group participants (−0.274 vs −0.131 D; P =.001).

“There are several possible mechanisms by which refractive error development and eye growth could be influenced by the observed differences in the accommodation-induced changes between the refractive error groups,” the study authors explain. “Firstly, the degradation of the retinal image due to the greater levels of [higher order aberrations], particularly asymmetric [higher order aberrations] like coma, could provide a form deprivation-like stimulus that produces axial elongation. Secondly, the ocular growth response to imposed defocus in chicks has been shown to be due to the detection of optical vergence within the retinal image.”

Study limitations include a small sample size.