Wavefront-guided ablation retreatment using Iris registration.

PURPOSE: To evaluate the efficacy, predictability, safety, and intraoperative and postoperative complications of laser in situ keratomileusis (LASIK) retreatment in myopic eyes using wavefront-guided ablation with iris registration (IR). METHODS: Retrospective analysis was used to evaluate wavefront-guided retreatment with IR in a consecutive cohort of 77 eyes (57 patients) after LASIK. The eyes were divided into two groups: no previous retreatment group (group 1) (n = 63) and previous LASIK retreatment group (group 2) (n = 14). The primary outcome variables assessed postoperatively at 1, 3, and 6 months were uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and pre- and postretreatment changes in manifest refraction. RESULTS: The mean preretreatment spherical equivalent in group 1 was reduced from -0.5 +/- 1.0 diopter (D) (range -3 to 2.4) to 0.06 +/- 0.3 (range -0.9 to 0.6) (P < 0.002) at 6 months. In group 2, the mean preretreatment spherical equivalent was reduced from -0.9 +/- 1.24D (range -3.1 to -0.5) to 0.04 +/- 0.5 (range -1.0 to 1.1) (P < 0.049) at 6 months. At 6 months, UCVA was 20/20 or better in 92% in group 1 and 64% in group 2, of patients, respectively. No eyes lost more than one line of BCVA in group 1 and one eye (7%) lost two lines of BCVA in group 2. CONCLUSION: Wavefront-guided LASIK retreatment with IR after LASIK is an effective, predictable, and safe procedure in cases requiring a single retreatment. In contrast, eyes with previous retreatments showed less predictability and lower percentage of eyes with postoperative 20/20 UCVA.

Intraocular lens power calculation after radial keratotomy: estimating the refractive corneal power.

PURPOSE: To evaluate the most accurate method for corneal power determination in patients with previous radial keratotomy (RK). SETTING: University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA. METHODS: A retrospective review of data for 16 eyes of 14 patients with a history of RK and subsequent phacoemulsification and posterior chamber intraocular lens (IOL) implantation was performed. Outcome measures included axial length, postoperative topography, type and power of IOL implanted, and postoperative spherical equivalent (SE) refraction at 3 to 6 months. Average central corneal power (ACCP) was defined as the average of the mean powers of the central Placido rings. For each eye, simulated K-readings and different values of ACCP computed corresponding to different central corneal diameters were used in each case, along with the implanted IOL power, to back-calculate the SE refraction (Ref) via the double-K adjusted Holladay 1 IOL formula. The predicted refractive error was hence computed as (Ref - SE), both in algebraic and absolute values. RESULTS: The ACCP over the central 3.0 mm (ACCP(3mm)) yielded the lowest absolute predicted refractive error (0.25 +/- 0.38 diopters [D]), which was statistically lower than the error for ACCP(1mm) (P<.001) and for the simulated K-value (P = .033). It also resulted in 87.5% of eyes being within +/-0.50 D and 100% within +/-1.00 D of the actual postoperative refraction. CONCLUSIONS: Corneal refractive power after RK was best described by averaging the topographic data of the central 3.0 mm area. Applying this method, together with a double-K IOL formula, achieved excellent IOL power predictability.