Grosvenor T, Goss D A
School of Optometry, Indiana University, Bloomington, USA.
Optom Vis Sci. 1998 Feb;75(2):132-45. doi: 10.1097/00006324-199802000-00017.
The purpose of this paper is to review the available evidence concerning the role of the cornea in achieving and maintaining emmetropia, as well as its role in the development and progression of myopia. The role of the cornea in emmetropization is most evident at the two extremes of life. During infancy, when the axial length increases rapidly, both the cornea and the lens become flatter, moving the refractive state of the eye toward emmetropia; during the later years of life, when the axial length remains constant or even shortens, the cornea appears to steepen somewhat. When myopia develops, in some cases the cornea may undergo a "paradoxical" steepening, which accelerates, rather than retards, the development of myopia. The effect of the cornea on the development and progression of myopia is evident when the ratio of axial length to corneal radius--the AL/CR ratio--is considered. Recent studies suggest that a high AL/CR ratio, which has a value of approximately 3.0 in the emmetropic eye, is a risk factor for youth-onset myopia. Several studies have shown that myopic eyes have greater mean corneal powers than emmetropic eyes; this may be mostly due to greater corneal powers being a risk factor for youth-onset myopia.
本文旨在综述关于角膜在实现和维持正视化过程中的作用，以及其在近视发生和发展中的作用的现有证据。角膜在正视化过程中的作用在生命的两个极端最为明显。在婴儿期，当眼轴长度迅速增加时，角膜和晶状体都会变得更扁平，使眼睛的屈光状态趋向正视化；在生命后期，当眼轴长度保持不变甚至缩短时，角膜似乎会稍有变陡。当近视发生时，在某些情况下角膜可能会出现“反常”变陡，这会加速而不是延缓近视的发展。当考虑眼轴长度与角膜半径的比值——AL/CR比值时，角膜对近视发生和发展的影响就很明显了。最近的研究表明，高AL/CR比值（在正视眼中约为3.0）是青少年近视的一个危险因素。几项研究表明，近视眼睛的平均角膜屈光力比正视眼睛更大；这可能主要是因为更高的角膜屈光力是青少年近视的一个危险因素。
