Hersh P S, Patel R
Department of Ophthalmology, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY 10467.
J Refract Corneal Surg. 1994 Mar-Apr;10(2 Suppl):S250-4.
Most excimer laser refractive procedures use a computer driven mechanical diaphragm to shape the laser beam. Studies are currently underway using an ablatable polymethylmethacrylate (PMMA) mask to transfer a new spherical or toric curve to the cornea for the correction of myopia and astigmatism; it may leave a smoother corneal surface than diaphragm procedures.
As part of a Phase IIb FDA clinical study, 25 eyes of 25 patients underwent excimer laser photorefractive keratectomy using a hand held ablatable mask. Fifteen eyes had attempted spherical corrections of up to 6.00 diopters (D) and 10 had toric corrections of up to 6.00 D of sphere and 2.75 D of astigmatism.
Seventy-four percent of all eyes achieved uncorrected visual acuity of 20/40 or better--86% in the spherical group and 63% in the astigmatism group. Sixty-nine percent of eyes were within +/- 1 D of the attempted correction. In eyes treated for astigmatism, mean astigmatism decreased from 1.48 D preoperatively to 0.86 D postoperatively. Approximately one half of the eyes treated for astigmatism had a decrease in cylinder of more than 0.5 D. One eye lost 2 Snellen lines of best spherical corrected visual acuity. Video keratography showed toric ablations to result in an elliptical optical zone. Analysis of centration of the procedure showed 66% of ablations centered within 1.0 mm of the center of the pupil aperture.
The ablatable mask represents a promising modality for the treatment of eyes with both myopia and myopic astigmatism.
大多数准分子激光屈光手术使用计算机驱动的机械光阑来塑形激光束。目前正在进行一些研究，使用可消融的聚甲基丙烯酸甲酯（PMMA）面罩将新的球面或复曲面曲线转移到角膜上，以矫正近视和散光；与光阑手术相比，它可能会使角膜表面更光滑。
作为美国食品药品监督管理局（FDA）IIb期临床研究的一部分，25例患者的25只眼睛接受了使用手持可消融面罩的准分子激光屈光性角膜切削术。15只眼睛尝试进行了高达6.00屈光度（D）的球面矫正，10只眼睛进行了高达6.00 D的球面和2.75 D散光的复曲面矫正。
所有眼睛中有74%的未矫正视力达到20/40或更好，球面组为86%，散光组为63%。69%的眼睛在尝试矫正的±1 D范围内。在接受散光治疗的眼睛中，平均散光从术前的1.48 D降至术后的0.86 D。接受散光治疗的眼睛中约有一半的柱镜降低超过0.5 D。一只眼睛的最佳球面矫正视力下降了2行Snellen视力表。视频角膜地形图显示复曲面消融导致椭圆形光学区。手术中心定位分析显示，66%的消融位于瞳孔孔径中心1.0 mm范围内。
可消融面罩是治疗近视和近视散光眼睛的一种有前景的方式。
