Infant eyes: optics and accommodation
作者:
HowlandHoward C.,
期刊:
Current Eye Research
(Taylor Available online 1982)
卷期:
Volume 2,
issue 3
页码: 217-224
ISSN:0271-3683
年代: 1982
DOI:10.3109/02713688208997697
出版商: Taylor&Francis
数据来源: Taylor
摘要:
Infant eyes grow rapidly in the first year of life. They exhibit considerable amounts of astigmatism, most frequently in the horizontal/vertical meridians with the horizontal meridian focused myopically relative to the vertical (i.e.“against-the-rule”). By photokeratometry it is shown that most of this astigmatism in young infants is corneal in nature. The ability to accurately focus a visual target at varying distances exists to some extent from birth, but impoves rapidly in the first 4 to 6 months of life until the net spherical error of focus is less than 0.5 diopters for targets 1.5 meters distant. At this stage, the astigmatism of the eye accounts for more than half of the defocus of the worst focused meridian. The persistence of astigmatism beyond the development of accurate focusing raises questions as to its conceivable functional significance. Because the mechanism of accommodation in adults may involve one or more of several methods for detecting the sign of defocus, including astigmatic blur, a possible role of astigmatism in infant focusing mechanisms is described.
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