Efficacy of Femtosecond Intrastromal Corneal Incisions Made During Cataract Surgery
To evaluate the effectiveness of femtosecond laser intrastromal (IS) incisions made during cataract surgery to reduce or prevent increase in corneal astigmatism.
Using the Catalys laser (Abbott Medical Optics), IS incisions were created according to the nomogram proposed by Julian Stevens, modified to take into account posterior corneal astigmatism. The incisions were placed at diameter of 8 mm and a depth of 20% from both anterior and posterior corneal surfaces. Corneal astigmatism was measured before and 3 weeks or more after the surgery with Lenstar, Cassini, and Atlas. Inclusion criteria are consecutive cases with post-operative follow-up of 3 weeks or longer and best-corrected visual acuity of 20/25 or better. OCT scans (RTVue, Optovue) were also obtained postoperatively to assess the location of the IS incisions.
Twenty-four eyes of 21 patients were included with paired incisions (30° - 60°) in 19 eyes and a single incision (35° - 60°) in 5 eyes. Preoperatively, 4.2%, 16.7%, 45.8% and 62.5% of eyes had corneal astigmatism (Lenstar) within 0.25 D, 0.50 D, 0.75 D, and 1.0 D, respectively; postoperatively, the percentages of eyes with manifest cylinder in each bin significantly increased to 54.2%, 87.5%, 100%, and 100%, respectively (all P<0.01). With OCT, the IS incision locations were 16.7% ± 5.9% (SD, range 8.4-28.9%) depth anteriorly and 35.7% ± 9.1% (range 16.8-52.7%) depth posteriorly.
IS incisions with femtosecond laser significantly decreased corneal astigmatism. However, some femtosecond laser incisions were located more anteriorly than planned. More eyes will be enrolled, a nomogram will be developed, and effects of new software will be assessed.