Assessment of axial length before and after myopic LASIK with the IOLMaster.

PURPOSE: To assess the relationship between theoretical ablation depth and axial length change after LASIK with the IOLMaster (Carl Zeiss Meditec, Dublin, CA). METHODS: Ninety-nine eyes were examined preoperatively and 1 and 3 months after LASIK. RESULTS: Mean ± standard deviation (SD) spherical equivalent before LASIK was -4.06 ± 1.91 diopters (D). Mean ± SD ablation depth was 83.13 ± 30.31 µm. Mean ± SD postoperative axial length of 25.11 ± 0.14 mm at 1 month was significantly shorter than mean ± SD preoperative axial length of 25.20 ± 0.14 mm (P < .001) with no subsequent change thereafter (P = .450). An increase in ablation depth of 1 µm led to a decrease in axial length of 0.00118 ± 0.00005 mm. Ablation depth correlated strongly with change in axial length (adjusted R(2) = 0.9039). CONCLUSIONS: The IOLMaster showed a decrease in axial length after LASIK that correlated well with theoretical ablation depth.

Mitomycin C in photorefractive keratectomy.

PURPOSE: To evaluate the outcome of primary or retreatment photorefractive keratectomy (PRK) or phototherapeutic keratectomy (PTK) with mitomycin C (MMC) 0.02% applied prophylactically intraoperatively for the prevention of haze and regression in cases of significant haze and regression after primary PRK, due to previous radial keratotomy (RK), in primary PRK eyes with high myopia, and in comeas with a previous superficial foreign body scar. METHODS: This was a retrospective evaluation of 34 eyes treated with PRK or PTK and intraoperative MMC. Mitomycin C was applied immediately after laser ablation. Postoperative examinations were conducted 3 and 7 days after surgery and monthly for 6 months. Haze was graded on a standard 0+ (clear cornea) to 4+ (total opacity) scale. Visual acuity was measured as a general baseline indicator. RESULTS: Postoperatively, uncorrected visual acuity (UCVA) was 20/20 or better in 21 eyes and 20/25 in 5 eyes with best spectacle-corrected visual acuity (BSCVA) of 20/20 or better. Three eyes achieved UCVA of 20/30 with BSCVA of 20/20 or better; and 5 eyes had UCVA of 20/40 with BSCVA of 20/20 or better. Nineteen (56%) eyes had grade 0+ haze and 15 (44%) eyes had grade 0.5+ haze (trace haze) at 6-month follow-up. CONCLUSIONS: Mitomycin C 0.02% used prophylactically during PRK or PTK retreatment was effective in preventing significant recurrent haze from developing. In eyes with high myopia or previous RK or scarring, MMC was effective in preventing significant haze formation.

Correction of high astigmatism: case studies using the mixed-cylinder approach.

PURPOSE: To explain the use of the mixed-cylinder approach in treating moderate to high astigmatism with the NIDEK EC-5000 excimer laser system. METHODS: Retrospective case series report. RESULTS: Three patients with bilateral moderate to high astigmatism were treated successfully using the mixed cylinder approach. CONCLUSIONS: The use of the mixed-cylinder approach with the NIDEK EC-5000 excimer laser may be a safe and predictable option for treating moderate to high astigmatism.

Estimation of corneal power after myopic laser refractive surgery: comparison of methods against back-calculated corneal power.

PURPOSE: To compare methods of corneal power estimation after myopic laser refractive surgery with back-calculated corneal power (K). SETTING: Private practice, Edmonton, Alberta, Canada. DESIGN: Case series. METHODS: Patients with previous myopic laser surgery followed by cataract extraction were studied. Back-calculated K obtained with the Holladay IOL Consultant was compared with that obtained by the clinical history method (CHM), the modified Maloney method, an adaptation of the Maloney method using individualized Orbscan IIz-derived posterior corneal power values, Orbscan IIz quantitative area topography, and the Gaussian optics formula. A mixed effects linear model was used for analysis. RESULTS: The mean spherical equivalent (SE) before laser treatment was -6.43 diopters (D) ± 3.52 (SD). The estimated means of all methods except those obtained with the CHM, modified Maloney method, 2.0 mm total axial map, 1.5 mm total mean map, and 1.5 mm total optical map were significantly different from the mean of the back-calculated K. Estimates from the 1.5 mm total mean map were generally 0.06 D higher. The 2.0 mm total axial map, modified Maloney method, 1.5 mm total optical map, and CHM underestimated corneal power by 0.11 D, 0.13 D, 0.22 D, and 0.26 D, respectively. Unit increases in optical zone and pre-laser myopic SE were associated with decreases in corneal power of 1.58 D (P = .047) and 0.55 D (P = .0001), respectively. CONCLUSION: The modified Maloney method, 2.0 mm total axial map, 1.5 mm total mean map and 1.5 mm total optical map of the Orbscan IIz may provide estimates closer to the back-calculated K than the CHM. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.