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Adaptive optics for assessing the accommodation signals in the human eye

Poster Details

First Author: J.Esteve-Taboada SPAIN

Co Author(s):    A. Del Águila-Carrasco   T. Ferrer-Blasco   N. López-Gil   R. Montés-Micó     

Abstract Details



Purpose:

Emmetropization, which occurs with normal growth of the eye, can be understood as the process of interaction between the elements that the visual system use to maintain always a clear image on the retina. The elements involved in this process, determined by genetic and environmental factors, are the axial growth of the eye and the power reduction of the cornea and the lens moving towards emmetropia. There must be, therefore, a feedback mechanism between the brain and the visual system to guide the growth of the eye from the information in the retina, and whose foundations are not yet well established. Mismatches in the emmetropization process may influence the final refractive state. One of the refractive errors which today remains a public health problem is myopia, also being linked to a number of diseases directly associated (retinal detachment, open-angle glaucoma or some macular pathologies). For these reasons, it is essential to develop new procedures able to stop or slow the growth of myopia, as well as methods to early detect subjects at high risk of suffering it.

Setting:

University of Valencia, Spain

Methods:

The study of the mechanisms and optical signals that the visual system uses to respond to myopic and hyperopic defocus, along with the complete characterization of the stimuli that guide the dynamic response of accommodation, provide a good opportunity to investigate the cues that the visual system uses during emmetropization. Previous research has suggested that the visual system, in its accommodative response, is able to determine the sign of blur. Therefore the response to a given stimulus focused in front of or behind the retina does not follow a negative feedback response based on a trial and error system with the sole objective of maximizing the contrast of the retinal image. In recent years optical systems based on adaptive optics using deformable mirrors have been developed. These systems allow to completely characterize the wave aberration of the visual system employing wavefront sensors, for example, those of the Hartmann-Shack type. Furthermore, using these adaptive systems it is possible to compensate, modify or even reverse in real time, by adjusting the response of the deformable mirror, each of the components of the wavefront in order to isolate them, and thus to characterize the influence of the accommodative response to a particular defocus.

Results:

Analyses with these systems may provide results that will permit to know, for example, if the accommodative response is driven only by a trial and error system to maximize the contrast of the retinal image, or if instead it responds to certain monocular cues present in the aberrated wavefront in the retina.

Conclusions:

Adaptive optics and aberrometry provide a new method to examine the stimulus for accommodation in the absence of defocus, astigmatism and high-order aberrations (HOAs), with and without feedback from defocus and HOAs. All the outcomes obtained in the present research project are expected to be applied too for new designs of contact lenses for presbyopia correction and intraocular lenses that replace the crystalline lens to provide pseudo-accommodation. Project funded by: ERC-2012-StG 309416-SACCO FINANCIAL INTEREST: NONE

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