Mechanisms of emmetropization and what might go wrong in myopia

IF 1.5 4区 心理学 Q4 NEUROSCIENCES
Frank Schaeffel , Barbara Swiatczak
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Abstract

Studies in animal models and humans have shown that refractive state is optimized during postnatal development by a closed-loop negative feedback system that uses retinal image defocus as an error signal, a mechanism called emmetropization. The sensor to detect defocus and its sign resides in the retina itself. The retina and/or the retinal pigment epithelium (RPE) presumably releases biochemical messengers to change choroidal thickness and modulate the growth rates of the underlying sclera. A central question arises: if emmetropization operates as a closed-loop system, why does it not stop myopia development? Recent experiments in young human subjects have shown that (1) the emmetropic retina can perfectly distinguish between real positive defocus and simulated defocus, and trigger transient axial eye shortening or elongation, respectively. (2) Strikingly, the myopic retina has reduced ability to inhibit eye growth when positive defocus is imposed. (3) The bi-directional response of the emmetropic retina is elicited with low spatial frequency information below 8 cyc/deg, which makes it unlikely that optical higher-order aberrations play a role. (4) The retinal mechanism for the detection of the sign of defocus involves a comparison of defocus blur in the blue (S-cone) and red end of the spectrum (L + M−cones) but, again, the myopic retina is not responsive, at least not in short-term experiments. This suggests that it cannot fully trigger the inhibitory arm of the emmetropization feedback loop. As a result, with an open feedback loop, myopia development becomes “open-loop”.

散光机制和近视可能出现的问题
对动物模型和人类的研究表明,屈光状态在出生后的发育过程中通过一个闭环负反馈系统得到优化,该系统将视网膜图像散焦作为误差信号,这种机制被称为散焦。检测散焦及其信号的传感器位于视网膜本身。视网膜和/或视网膜色素上皮(RPE)可能会释放生化信使,以改变脉络膜厚度并调节底层巩膜的生长率。这就产生了一个核心问题:如果散光是作为一个闭环系统运行的,为什么它不能阻止近视的发展?最近在年轻人身上进行的实验表明:(1) 散光视网膜可以完美地区分真正的正散光和模拟散光,并分别触发瞬时眼轴缩短或拉长。(2)令人震惊的是,近视视网膜在施加正离焦时抑制眼球增长的能力减弱。(3)散光视网膜的双向反应是由低于 8 cyc/deg 的低空间频率信息引起的,因此光学高阶像差不太可能起作用。(4) 视网膜检测散焦符号的机制包括比较光谱蓝端(S 锥)和红端(L + M 锥)的散焦模糊,但近视视网膜同样没有反应,至少在短期实验中没有反应。这表明,近视眼视网膜无法完全触发屈光反馈环路的抑制臂。因此,在开放的反馈回路中,近视的发展成为 "开环"。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Vision Research
Vision Research 医学-神经科学
CiteScore
3.70
自引率
16.70%
发文量
111
审稿时长
66 days
期刊介绍: Vision Research is a journal devoted to the functional aspects of human, vertebrate and invertebrate vision and publishes experimental and observational studies, reviews, and theoretical and computational analyses. Vision Research also publishes clinical studies relevant to normal visual function and basic research relevant to visual dysfunction or its clinical investigation. Functional aspects of vision is interpreted broadly, ranging from molecular and cellular function to perception and behavior. Detailed descriptions are encouraged but enough introductory background should be included for non-specialists. Theoretical and computational papers should give a sense of order to the facts or point to new verifiable observations. Papers dealing with questions in the history of vision science should stress the development of ideas in the field.
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