A recent study shows that the accommodation error does not lead to future eye growth in chickens and therefore, myopia. On the other hand, some studies do not find any relationship between myopia and the accommodative lag. Some studies show that there is a relationship between the lag of accommodation and myopia. The accommodative lag, or insufficient amount of accommodation, causes hyperopic defocus on the retina, which, if sustained over long periods, might prompt axial elongation in the eye and therefore stimulate the onset of myopia during childhood. The link between myopia and accommodation has been intensively investigated and still this is uncertain. Īccommodation is the ability of the crystalline lens to alter its focus to maintain a sharp image on the retina. Other risk factors of myopia are near work, insufficient outdoor activities in children, and low luminance conditions. Genetics is a strong factor however, a recent study of twins suggests that refractive error is mostly affected by a shared environment rather than heritability.
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There are several theories regarding the cause and prevalence of myopia. In addition, myopia and specifically high myopia can lead to Myopic Macular Degeneration (MMD), retinal detachment and less frequently to glaucoma, and cataracts. For instance, in some East Asian communities, 96.5% of the young population is myopic. Recently, there has been an increasing interest in the study of myopia since it became a global epidemic. This refractive error is due to axial elongation of the eyeball and flattening of the crystalline lens in myopes, while corneal power seems to remain the same. People with spherical refractive errors ≤ -0.50 diopters (D) and ≤ -6 D are considered myopes and high myopes, respectively. Myopia is a refractive error in which light from distant objects is focused in front of the retina when accommodation is relaxed. Additionally, our data suggests that the faster the accommodation, the faster and longer the convergence and the larger the pupil miosis. On the other hand, increased lag of accommodation tends to be associated to larger refractive errors. Only miosis speed was found to be correlated to refractive error with p < 0.05, being slower for myopes. We did not find strong evidence of a link between myopia and altered dynamics of the accommodation process. Additionally, correlation values with p-value < 0.05 were found between accommodation speed and convergence duration (R = 0.57, p = 0.014), convergence speed (R = 0.48, p = 0.044), and pupil miosis amplitude (R = 0.47, p = 0.049). Correlation coefficients with refractive error had non-zero values for several parameters of the accommodative response but p-values were higher than 0.05 except in two cases: with pupil miosis speed (R = –0.49, p = 0.041) and with lag of accommodation (R = –0.57, p = 0.014). Additionally, the speed of accommodation was correlated with all the other parameters in the study. Correlation coefficients were calculated between refractive error and each computed variable. Measurements were performed in real time (25 Hz) with an open-view binocular Hartmann-Shack (HS) sensor using a GPU-based processing unit. Parameters related to the speed and amplitude of accommodation, convergence, miosis, and change in high-order aberrations were measured during the accommodative process for 2.8 D demand in 18 young healthy subjects (mean age 25.0 ± 4.7 years) with a range of refractive errors between 0 and -7.5 D (spherical equivalent). A secondary goal was to establish potential relationships between the speed of accommodation and other parameters in the accommodation process. The purpose of this work is to study the dynamics of the accommodative response as a function of the subject's refractive error, as a first step in determining whether an anomalous accommodative function could affect emmetropization or trigger myopia progression.