小学生
角膜
集中
固定(群体遗传学)
光学
入学学生
放射状角膜切开术
镜头(地质)
视力
验光服务
眼科
医学
折射误差
物理
人口
环境卫生
作者
Aaron Fay,Stephen L. Trokel,Joseph A. Myers
出处
期刊:Journal of Cataract and Refractive Surgery
[Ovid Technologies (Wolters Kluwer)]
日期:1992-07-01
卷期号:18 (4): 348-351
被引量:82
标识
DOI:10.1016/s0886-3350(13)80069-7
摘要
Placement of the surgical zone is critical in refractive procedures that alter a portion of the corneal curve. An improperly centered optical zone may produce glare, decrease best corrected visual acuity, and decrease contrast sensitivity. For proper placement, the new surface should be centered around the line of sight, which is the principal ray from the object of regard that passes through the image of the patient's pupil as projected on the cornea. This point is not necessarily at the geometric center of the cornea and is found by locating the center of the pupil while the patient is maintaining fixation coaxially with the surgeon. However, the pupil does not dilate concentrically and its geometric center moves as the pupil diameter changes. We have found a shift up to 0.7 mm in the geometric center of the pupil as it dilates. Therefore, centration of an ablated or a radial keratotomy zone is most efficiently done when the diameter of the modified corneal optical zone is centered around the line of sight and is superimposed upon the entrance pupil. This will minimize extension of the edge of the large pupil beyond the ablated zone and reduce unwanted secondary optical effects from degrading vision.
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