Non-penetrating femtosecond laser intrastromal astigmatic keratotomy in patients with mixed astigmatism after previous refractive surgery.

PURPOSE To report the outcomes of the correction of mixed astigmatism with non-penetrating femtosecond laser intrastromal astigmatic keratotomy in patients with previous refractive surgery. METHODS One hundred twelve eyes that had low mixed astigmatism after excimer laser surgery, refractive lens exchange, or phakic intraocular lens implantation underwent intrastromal astigmatic keratotomy using paired symmetrical non-penetrating intrastromal arcuate keratotomies created 60 μm from the surface to 80% depth at 7 mm diameter. Outcome measures included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), subjective refraction, and keratometry. A coupling ratio was calculated to assess the change in spherical equivalent. Average follow-up was 7.6 ± 2.9 months. Patients were divided into two groups: no excimer laser corneal ablation and previous excimer laser surgery. Preoperative and postoperative data were compared between groups and analyses were performed on the whole group of eyes. RESULTS Overall, the mean UDVA improved significantly from 0.18 ± 0.14 to 0.02 ± 0.12 logMAR (6/9 to ≈6/6 Snellen) (P < .01). The mean absolute subjective cylinder decreased significantly from 1.20 ± 0.47 diopters (D) preoperatively to 0.55 ± 0.40 D postoperatively (P < .01). Subjective sphere decreased significantly from +0.61 ± 0.33 to +0.17 ± 0.36 D (P < 0.01). The mean CDVA was -0.03 ± 0.08 logMAR (≈ 6/6 Snellen) preoperatively and -0.05 ± 0.09 logMAR (≈ 6/5 Snellen) postoperatively (P = .06). The coupling ratio was 0.92 ± 0.45. There was no statistically significant difference in the preoperative and postoperative sphere, cylinder, UDVA, CDVA, and coupling ratio between groups. No surgical complications occurred. CONCLUSIONS Femtosecond laser intrastromal astigmatic keratotomy was effective at reducing refractive error in patients where other surgical options were exhausted. Predictability and efficacy could be improved with nomogram refinement.