Excimer Lasers and Multifocal Corneal Ablations

Alarcón et al evaluated different theoretical models of a multifocal cornea for the correction of presbyopia by laser ablation using ray tracings. Because the pupil’s size decreases with accommodation, the investigators preferred the central model to obtain optimal multifocality with the achievement of a 2.4-mm central zone diameter to the peripheral model with a 2.9-mm central zone. It should be noted that, although near vision is better, the quality of distance vision provided by these models is worse than that of a presbyopic emmetropic eye.

In a clinical trial conducted over 12-months showed results of aspheric wavefrontguided LASIK to treat hyperopic presbyopia. They treated 66 eyes of 33 patients using the Visx Star S4 IR (Abbott Medical Optics Inc.). Six months postoperatively, mean corrected distance visual acuity was 20/20+1, and distance corrected near visual acuity was 2.7 ±1.7, with a maximum of a 6-line improvement in near vision. At 12 months, 100{0730eed075b45d9e50c00d6cd42dd08773e0164f29a45151808bf89051290974} of patients achieved a binocular simultaneous UCVA of 20/25 or better and J3. Negative spherical aberration highly correlated with a postoperative improvement in distance corrected near visual acuity. In their conclusions, the researchers stated that patients who had a larger amount of preoperative hyperopia or a greater decrease in preoperative distance-corrected near visual acuity were more likely to have overall satisfaction.

A chart review of 178 consecutive patients underwent bilateral presby-LASIK (or progressive multifocal LASIK) using the WaveLight Allegretto excimer laser (Alcon Laboratories, Inc.). The patients had a preoperative refractive error of emmetropia, myopia of up to -5.00 D, or hyperopia of up to +3.00 D and no more than 3.00 D of astigmatism. Of 102 patients with at least 3 months’ postoperative follow-up, 81{0730eed075b45d9e50c00d6cd42dd08773e0164f29a45151808bf89051290974} had a binocular distance UCVA of 20/20 or better, and 98{0730eed075b45d9e50c00d6cd42dd08773e0164f29a45151808bf89051290974} saw 20/25 or better. Additionally, 44{0730eed075b45d9e50c00d6cd42dd08773e0164f29a45151808bf89051290974} achieved J1 binocular near acuity, 60{0730eed075b45d9e50c00d6cd42dd08773e0164f29a45151808bf89051290974} J2, and 96{0730eed075b45d9e50c00d6cd42dd08773e0164f29a45151808bf89051290974} J3 or better.

另一种临床试验呈现了对老龄景观的颅骨飞秒激光治疗的早期结果。调查人员使用Technolas Perfect Vision Femtosecond激光（Technolas Perfect Vision GmbH）治疗了25名患者的Nondominant Eye。该程序涉及在视线周围创建五个连续的内部戒指。治疗时间约为20秒。UCVA的平均增益为4.42线，改善范围为0至9行。类似地，距离BCVA的平均损失为-0.46±0.83.9，Ruiz等人评估了45名患者的83只患者6至12个月的随访。Of the 83 eyes, 89.2{0730eed075b45d9e50c00d6cd42dd08773e0164f29a45151808bf89051290974} achieved both J2 and 20/25 or better, and 69.9{0730eed075b45d9e50c00d6cd42dd08773e0164f29a45151808bf89051290974} achieved a near UCVA of J1.该技术具有微创的优势，在几分钟内显示出快速效果。进一步调查长期稳定性正在进行。

Related data from a safety study performed in the Philippines by Harvey S. Uy, MD. Fourteen patients were between 45 and 60 years of age with 20/40 or better BCVA, had no greater than grade 2 cataracts, and had originally consented to cataract surgery. All underwent unilateral treatment with the option to proceed to cataract surgery after 1 month of follow-up. Early results showed no progressive cataract formation at 1 month.

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