Simon G, Ren Q, Parel J M
Department of Ophthalmology, University of California, Irvine, CA 92715.
J Refract Corneal Surg. 1994 Sep-Oct;10(5):519-28.
Noncontact laser photothermal keratoplasty may provide a new alternative for the treatment of myopia, hyperopia, and astigmatism. The purpose of this article is to study the refractive effect that laser photoablation keratoplasty is capable of producing on a normal human cadaver cornea, including the relationship between the keratometric changes and laser treatment parameters.
The human cadaver eyes were treated with a holmium laser (pulsed Ho:YAG, 2.10 microns, 250 microseconds) coupled to a maskable, polyprismatic delivery system mounted on either an optical bench or a slit-lamp microscope. Using a topographic videokeratography system, we first investigated the refractive effect that noncontact laser photothermal keratoplasty would produce on a normal cadaver cornea. We then studied the keratometric changes produced by different radiant exposure levels at a fixed treatment pattern, as well as by different treatment patterns at a fixed radiant exposure level. Finally, we studied the possible therapeutic application of laser photothermal keratoplasty for correcting high postoperative astigmatism on a cadaver eye model.
For the single-pulse 3-millimeter ring of eight-spot treatment, the keratometric power of the cornea initially increased with the radiant exposure and peaked at 26 J/cm2. The refractive effect was increased by projecting an additional set of eight spots equidistant between the first eight spots on the same diameter ring. Eighteen J/cm2 was the minimal radiant exposure required to produce consistent and predictable keratometric changes. The corneas were flattened using treatment patterns smaller than or equal to 3 mm in diameter and steepened using treatment patterns larger than or equal to 5 mm in diameter. A transition zone between 4 and 5 mm was observed in which minimal and unpredictable keratometric changes of the central cornea occurred. The surgically-induced astigmatism (> 10.00 D) was corrected by progressive laser photothermal keratoplasty treatments.
Laser photothermal keratoplasty can acutely steepen and flatten the cornea in human cadaver eyes.
非接触式激光光热角膜成形术可能为近视、远视和散光的治疗提供一种新的选择。本文的目的是研究激光光消融角膜成形术对正常人类尸体角膜产生的屈光效应，包括角膜曲率计测量变化与激光治疗参数之间的关系。
使用与安装在光具座或裂隙灯显微镜上的可屏蔽多棱镜输送系统相连的钬激光（脉冲Ho:YAG，2.10微米，250微秒）治疗人类尸体眼。使用地形图视频角膜曲率计系统，我们首先研究了非接触式激光光热角膜成形术对正常尸体角膜产生的屈光效应。然后，我们研究了在固定治疗模式下不同辐射暴露水平以及在固定辐射暴露水平下不同治疗模式所产生的角膜曲率计测量变化。最后，我们研究了激光光热角膜成形术在尸体眼模型上矫正术后高度散光的可能治疗应用。
对于八点治疗的单脉冲3毫米环，角膜的角膜曲率计测量值最初随辐射暴露增加而增加，并在26 J/cm²时达到峰值。通过在同一直径环上的前八个点之间等距投射另一组八个点，屈光效应增强。18 J/cm²是产生一致且可预测的角膜曲率计测量变化所需的最小辐射暴露。使用直径小于或等于3毫米的治疗模式可使角膜变平，使用直径大于或等于5毫米的治疗模式可使角膜变陡。在4至5毫米之间观察到一个过渡区，其中中央角膜出现最小且不可预测的角膜曲率计测量变化。通过逐步激光光热角膜成形术治疗可矫正手术引起的散光（>10.00 D）。
激光光热角膜成形术可使人类尸体眼的角膜迅速变陡和变平。
