Comparison of changes in corneal volume and corneal thickness after myopia correction between LASIK and SMILE.

Myopia is the most common refractive error. Surgical correction with laser is possible. LASIK and SMILE are the techniques currently most used. Aim of the study was to compare changes in corneal volume and thickness after the respective laser treatment. 104 eyes of 52 patients were matched based on refractive error into two equally sized groups, either treated with LASIK or SMILE. Measurements were obtained from the Scheimpflug camera (Pentacam) preoperatively and at 3 and 12 months postoperatively. 3 months postoperatively, the flapless SMILE procedure resulted in a significant overall greater loss of corneal volume (P < 0.01) and corneal thickness (P < 0.01) compared to LASIK. No significant difference was found when comparing the 3 to 12-months values in each group. Within the currently used ranges of refractive error correction, loss in central corneal thickness and corneal volume with SMILE is higher in comparison to LASIK. As greater loss in corneal volume and thickness might contribute to higher level of corneal instability maximum ranges of refractive error correction with SMILE should not supersede those set currently for LASIK until more long-term results on corneal ectasia are available for SMILE.

Comparison of femtosecond laser-assisted cataract surgery and conventional cataract surgery: a meta-analysis and systematic review.

PURPOSE: To compare the efficacy and safety of femtosecond laser-assisted cataract surgery (FLACS) with conventional cataract surgery (CCS). SETTING: Department of Ophthalmology, Goethe-University, Frankfurt am Main, Germany. DESIGN: Meta-analysis. METHODS: PubMed, Cochrane Library, and EMBASE were systematically searched for studies comparing FLACS and CCS. Outcomes were efficacy and safety parameters. The effect measures were weighted mean differences or odds ratios with 95% CIs. RESULTS: A total of 73 studies (25 randomized controlled, 48 observational) were reviewed with a total of 12 769 eyes treated with FLACS and 12 274 eyes treated with CCS. In eyes treated with FLACS, uncorrected and corrected distance visual acuities and spherical equivalent after 1 month to 3 months (P = .04, P = .005, and P = .007, respectively) were better, total and effective phacoemulsification times were shorter (P < .001 each), cumulative dissipated energy was less (P < .001), circularity was more accurate (P < .001), central corneal thickness after 1 day and 1 month to 3 months was less (P < .001 and P = .004, respectively), and endothelial cell loss after 3 to 6 weeks and 3 months was less (P = .002 and P < .001, respectively) compared with CCS. Anterior capsule ruptures occurred more often with FLACS. No significant differences among groups were found in visual acuity at 1 week and after 6 months or in posterior capsule rupture rates and endothelial cell loss after 6 months. CONCLUSIONS: Both FLACS and CCS are effective and safe. FLACS required less ultrasound energy and a more precise treatment. However, mid-term visual acuity did not show any difference between both methods.

Characteristics of preoperative and postoperative astigmatism in patients having Descemet membrane endothelial keratoplasty.

PURPOSE: To evaluate the characteristics of preoperative and postoperative astigmatism in patients having Descemet membrane endothelial keratoplasty (DMEK). SETTING: Department of Ophthalmology, Goethe University, Frankfurt, Germany. DESIGN: Retrospective case series. METHODS: Measurements were obtained using a Scheimpflug camera (Pentacam AXL) preoperatively and 3 months and 12 months postoperatively. Values of front and back astigmatism and total astigmatism in the central 4.0 mm diameter zone (TCA4) were analyzed. RESULTS: Fifty-three eyes of 45 patients were included. The prevalence of TCA4 above 1.0 diopter (D) was considerably higher (79%) and with-the-rule astigmatism was less frequent in this cohort of European patients with Fuchs endothelial dystrophy (mean age 65 years) than that reported in a meta-analysis of healthy European eyes. The TCA4 values correlated with anterior astigmatism preoperatively and postoperatively (P < .001) and with posterior astigmatism at the 1-year follow-up (P < .01). Although, no correlation was found between the preoperative and 1-year results for anterior astigmatism (P = .12), posterior astigmatism (P = .35), or total corneal astigmatism (P = .47), the difference in vector analysis between the two measurements was only 0.01 at 109 degrees, 0.03 at 98 degrees, and 0.02 at 157 degrees, respectively. However, the greater the difference between the preoperative TCA3 and preoperative TCA5 values, the greater the decrease in corneal astigmatism (P < .001). CONCLUSIONS: The percentage of eyes with corneal astigmatism above 1.0 D was higher preoperatively and postoperatively in patients with Fuchs endothelial dystrophy than in a healthy population. Predicting postoperative astigmatism based on preoperative results is not possible; however, in eyes with a high difference between TCA3 and TCA5, a reduction in corneal astigmatism after DMEK is likely.

Comparison of standard and accelerated corneal cross-linking for the treatment of keratoconus: a meta-analysis.

PURPOSE: To compare results between standard and accelerated corneal collagen cross-linking (CXL) for the treatment of progressive keratoconus. METHODS: We performed literature searches in PubMed, Cochrane Library, Web of Science, ISRCTN registry, ClinicalTrials.gov, and EMBASE for studies comparing conventional Dresden (C-CXL) and accelerated CXL (A-CXL). Outcomes were clinical results and changes in corneal properties. Weighted mean differences were used to evaluate the effects. RESULTS: Here, 22 studies with 1158 eyes (C-CXL: 577 eyes; A-CXL: 581 eyes) were included. At the last follow-up, C-CXL was superior regarding minimum keratometry (p < 0.00001) and demarcation line depth (p < 0.00001), whereas A-CXL should be favoured when considering minimum corneal thickness (p = 0.0005). No differences in uncorrected and corrected distance visual acuity (p = 0.09 and 0.98), spherical equivalent (p = 0.11), spherical and cylindrical error (p = 0.29 and 0.32), maximal and average keratometry (p = 0.05 and 0.65), central corneal thickness (p = 0.15), corneal biomechanical properties (p ≥ 0.21 respectively), time of reepithelialization (p = 0.76), subbasal nerve density (p = 0.69), endothelial cell density (p = 0.30) and morphology (p ≥ 0.40 respectively) were found among both groups. CONCLUSION: Consideration of less corneal thinning favours A-CXL, whereas the deeper demarcation line and greater changes in minimum keratometric values in C-CXL may indicate a higher treatment efficacy. Altogether, C-CXL, as well as A-CXL, provides successful results in the strengthening of corneal tissue.

Comparison of 9 modern intraocular lens power calculation formulas for a quadrifocal intraocular lens.

PURPOSE: To evaluate the accuracy of 9 formulas (Barrett Universal II, Haigis, Hill-Radial Basis Function [RBF], Hoffer Q, Holladay 1, Holladay 2, Olsen, Sanders-Retzlaff-Kraff/theoretical [SRK/T], and T2) calculating the power of the quadrifocal Acrysof IQ Panoptix TFNT00 intraocular lens (IOL). SETTING: Department of Ophthalmology, Goethe University, Frankfurt, Germany. DESIGN: Retrospective case series. METHODS: The study included patients having cataract surgery with insertion of a quadrifocal IOL over 15 months. Preoperative biometry measurements were obtained from an IOLMaster 500. Optimized IOL constants were calculated to reduce the mean refractive prediction error. The primary outcomes were differences in mean absolute prediction error between the formulas. Median and maximum absolute prediction errors were evaluated as well as percentages of eyes within prediction errors of ±0.25 diopters (D), ±0.50 D, ±1.00 D, and ±2.00 D. RESULTS: The study comprised 75 eyes of 38 patients. The formulas were ranked by the mean absolute refractive prediction error as follows: Barrett Universal II (0.294 D), Hill-RBF (0.332 D), Olsen (0.339 D), T2 (0.351 D), Holladay 1 (0.381 D), Haigis (0.382 D), SRK/T (0.393 D), Holladay 2 (0.399 D), and Hoffer Q (0.410 D). The differences in absolute errors between the formulas were significant (P < .001). The lowest maximum absolute prediction error was obtained with the Barrett Universal II. CONCLUSION: The most accurate predictions of actual postoperative refraction were achieved using the Barrett Universal II, Hill-RBF, Olsen, or T2 formula. Thus, one of these formulas should be used for IOL power calculation of the quadrifocal IOL.