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.
Another clinical trial presented early outcomes of Intracor femtosecond laser treatment for presbyopia. The investigators treated the nondominant eye of 25 patients using the Technolas Perfect Vision femtosecond laser (Technolas Perfect Vision GmbH). The procedure involves the creation of five consecutive intrastromal rings around the line of sight. Treatment times were approximately 20 seconds. The mean gain in UCVA was 4.42 lines, with a range of 0 to 9 lines of improvement. The mean loss of distance BCVA was -0.46 ±0.83.9 Similarly, Ruiz et al evaluated 83 eyes of 45 patients with 6- to 12-month follow-up. 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. This technology has the advantage of being minimally invasive, with a rapid effect manifesting within minutes to several hours. Further investigation of long-term stability is ongoing.
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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