Moreira H, Garbus J J, Fasano A, Lee M, Clapham T N, McDonnell P J
Doheny Eye Institute, Los Angeles, CA 90033.
Arch Ophthalmol. 1992 Jul;110(7):994-9. doi: 10.1001/archopht.1992.01080190100036.
Excimer laser photorefractive keratectomy can flatten the central cornea, thereby eliminating myopic refractive errors; in older patients, however, presbyopia limits satisfaction. Computer-assisted topographic analysis of corneas after refractive surgery indicates that a minority of patients achieve a multifocal lens effect, such that they maintain reasonable acuity over a range of defocus. We have purposefully attempted to create a multifocal refractive effect and have analyzed the subsequent topographies quantitatively to determine if multifocality was achieved. In corneas not operated on and plastic hemispheres, a fairly small range of corneal powers is observed; the range of powers is increased after a monofocal ablation. After multifocal ablations, a greater spread of surface powers is observed, often with a bimodal distribution, indicative of an apparent multifocal effect. These observations suggest that in some patients undergoing photorefractive keratectomy for myopia, it may be possible to reduce symptoms of presbyopia, although a decrease in image contrast or monocular diplopia may complicate this approach.
准分子激光原位角膜磨镶术可以使中央角膜变平，从而消除近视屈光不正；然而，在老年患者中，老花眼会影响手术满意度。屈光手术后角膜的计算机辅助地形图分析表明，少数患者可实现多焦点晶状体效应，从而在一定范围的散焦情况下保持合理的视力。我们有意尝试创造多焦点屈光效果，并对随后的地形图进行了定量分析，以确定是否实现了多焦点效果。在未手术的角膜和塑料半球体中，观察到的角膜屈光力范围相当小；单焦点消融后屈光力范围增加。多焦点消融后，观察到表面屈光力的分布更分散，通常呈双峰分布，这表明存在明显的多焦点效应。这些观察结果表明，对于一些接受近视准分子激光原位角膜磨镶术的患者，有可能减轻老花眼症状，尽管图像对比度降低或单眼复视可能会使这种方法复杂化。
