Comparison of visual and refractive results after transepithelial and mechanical photorefractive keratectomy in myopia.

PURPOSE: To compare postoperative visual outcomes and higher-order aberrations (HOAs) following transepithelial photorefractive keratectomy (t-PRK) and mechanical photorefractive keratectomy (m-PRK). METHODS: The medical records of patients who underwent photorefractive keratectomy (PRK) were retrospectively evaluated. Forty-five patients were treated with m-PRK, and 45 were treated with t-PRK. Visual acuity, subjective manifest refraction, and corneal topography were analyzed before surgery and 12 months after surgery for both groups. Total HOAs, spherical, coma, and trefoil aberrations were derived from topography data over the 6-mm corneal zone. RESULTS: In the m-PRK group, the mean preoperative spherical equivalence (SE) changed from -3.15 ± 0.70 D preoperatively to -0.24 ± 0.70 D 1 year postoperatively. Likewise, SE decreased from -3.36 ± 0.63 to -0.25 ± 0.63 D in the t-PRK group 1 year after the surgery. The number of eyes within ± 0.50 D of the target refraction was 89% for m-PRK and 87% for t-PRK groups (p = 0.20). Eighty-four percentage of eyes in the t-PRK group and 80% of eyes in the m-PRK group showed an uncorrected distance visual acuity of 20/25 or better (p = 0.24). Total HOAs, spherical aberration, coma, and trefoil aberrations increased in both groups after surgery, but no statistically significant differences were detected postoperatively among the corneal aberrations. CONCLUSIONS: t-PRK and m-PRK result in comparable refractive results for the correction of low and moderate myopia. Corneal aberrations induced by t-PRK and m-PRK were similar. Epithelial removal techniques do not affect visual, refractive results, or HOAs in PRK.

Comparison of Accelerated Corneal Collagen Cross-linking Types for Treating Keratoconus.

PURPOSE: To compare the results of different protocols for accelerated corneal collagen cross-linking (CXL) in patients with progressive keratoconus. MATERIALS AND METHOD: This prospective comparative study involved 40 patients treated with intended UV-A radiance of 5.4 J/cm2 in 74 eyes (Group 1) and 42 patients treated with radiance of 7.2 J/cm2 in 72 eyes (Group 2). Visual acuity, subjective manifest refraction and corneal topography were analyzed before and 12 months after surgery in both groups. Postoperative complications were also noted. The results of the two protocols were statistically compared. RESULTS: There were no statistically significant differences between the groups in uncorrected distance visual acuity, corrected distance visual acuity or corneal topography pre- or postoperatively. The differences in keratometric readings (K apex, SimK1 and SimK2) and refractive results were not significant. CONCLUSION: The application of total intended UV-A radiance of 5.4 J/cm2 or 7.2 J/cm2 for accelerated CXL in patients with progressive keratoconus resulted in similar refractive and topographic outcomes.

Comparison of Changes in Corneal Biomechanical Properties after Photorefractive Keratectomy and Small Incision Lenticule Extraction.

OBJECTIVES: To compare the postoperative biomechanical properties of the cornea after photorefractive keratectomy (PRK) and small incision lenticule extraction (SMILE) in eyes with low and moderate myopia. MATERIALS AND METHODS: We retrospectively examined 42 eyes of 23 patients undergoing PRK and 42 eyes of 22 patients undergoing SMILE for the correction of low and moderate myopia. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with an Ocular Response Analyzer before and 6 months after surgery. We also investigated the relationship between these biomechanical changes and the amount of myopic correction. RESULTS: In the PRK group, CH was 10.4±1.3 mmHg preoperatively and significantly decreased to 8.5±1.3 mmHg postoperatively. In the SMILE group, CH was 10.9±1.7 mmHg preoperatively and decreased to 8.4±1.5 mmHg postoperatively. CRF was significantly decreased from 10.8±1.1 mmHg to 7.4±1.5 mmHg in the PRK group whereas it was decreased from 11.1±1.5 mmHg to 7.9±1.6 mmHg in the SMILE group postoperatively. There was a significant correlation between the amount of myopic correction and changes in biomechanical properties after PRK (r=-0.29, p=0.045 for CH; r=-0.07, p=0.05 for CRF) and SMILE (r=-0.25, p=0.048 for CH; r=-0.37, p=0.011 for CRF). CONCLUSION: Both PRK and SMILE can affect the biomechanical strength of the cornea. SMILE resulted in larger biomechanical changes than PRK.

Visual and Refractive Outcomes of Photorefractive Keratectomy and Small Incision Lenticule Extraction (SMILE) for Myopia.

PURPOSE: To compare the refractive outcomes of small incision lenticule extraction (SMILE) with photorefractive keratectomy (PRK) using an aberration-free ablation profile. METHODS: One eye of patients diagnosed as having myopia for bilateral refractive correction was randomly allocated to either PRK or SMILE. The primary outcome measures included refractive efficacy, predictability, safety, stability, corneal aberrations, and adverse events. Patients were followed up for 1 year postoperatively; postoperative uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, and corneal aberrations were recorded and compared with preoperative data. RESULTS: Thirty-nine patients in the PRK group and 35 patients in the SMILE group completed the study. The mean preoperative spherical equivalent refractions were -3.27 ± 0.62 diopters (D) for the PRK group and -3.56 ± 1.12 D for the SMILE group. The average postoperative spherical equivalent refractions were -0.26 ± 0.29 and -0.43 ± 0.38 D for the PRK and SMILE groups, respectively (P = .06). Total higher order aberrations in the 6-mm central corneal zone were significantly higher in the SMILE group (0.21 ± 0.10 µm) than in the PRK group (0.09 ± 0.03 µm) (P = .01) 12 months postoperatively. However, no statistically significant differences were found among spherical, trefoil, and coma aberrations between the groups. CONCLUSIONS: The refractive results of PRK with aberration-free aspheric ablation are similar to those of SMILE in eyes with low myopia. The induction of coma, spherical, and trefoil aberrations did not statistically differ after both surgeries, but the total higher order aberrations after SMILE were significantly higher than PRK with aberration-free aspheric ablation. [J Refract Surg. 2016;32(9):604-610.].

Long-term Results of Small-incision Lenticule Extraction in High Myopia.

OBJECTIVES: To evaluate two-year results of small-incision lenticule extraction (SMILE) for correction of high myopia. MATERIALS AND METHODS: Forty-five eyes of 35 patients with mean spherical equivalent (SE) of -7.10±0.95 D who underwent routine SMILE by a single surgeon and were followed for at least 2 years were analyzed by retrospective chart review. SMILE was performed with a Visumax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). Follow-up intervals were at 1, 6, 12, and 24 months after surgery. Uncorrected and best corrected distance visual acuity (CDVA), corneal wavefront measurements, and all complications were recorded. RESULTS: After 2 years, 86% of eyes with plano target had an uncorrected distant visual acuity (VA) of 20/20 or better. Two percent of eyes lost 1 line of CDVA, while 32% gained 1 line. The mean SE after 2 years was -0.30±0.50 D. Corneal total high-order aberrations (HOA) increased from 0.43 to 0.92 µm at postoperative 12 months. There were metallic foreign bodies at the corneal interface in 1 eye of 1 patient which caused no decrease in VA. CONCLUSION: SMILE for high myopia seems safe and effective in light of two-year follow-up results. The procedure caused a moderate increase in HOA.

Fellow Eye Comparison of Nerve Fiber Regeneration After SMILE and Femtosecond Laser-assisted LASIK: A Confocal Microscopy Study.

PURPOSE: To compare postoperative corneal nerve fiber regeneration after small incision lenticule extraction (SMILE) and femtosecond laser-assisted LASIK (FS-LASIK). METHODS: The medical records of patients who underwent SMILE were retrospectively reviewed. Patients with SMILE in one eye (the SMILE group) and FS-LASIK in the fellow eye (the FS-LASIK group) and who had undergone a confocal microscopy study were retrospectively identified. Subbasal nerve fiber density was measured and compared between the groups preoperatively and at 1 week and 1, 3, and 6 months postoperatively. RESULTS: Thirty eyes of 15 patients were included in the study. Preoperative characteristics of the eyes were similar between the groups. However, there was a statistically significant difference in subbasal nerve fiber density between the groups at 1 month (SMILE group: 1,505 ± 627 µm/mm(2) [range: 625 to 2,540 µm/mm(2)], FS-LASIK group: 1,107 ± 509 µm/mm(2) [range: 595 to 2,313 µm/mm(2)], P = .003) and 3 months (SMILE group: 1,534 ± 503 µm/mm(2) [range: 650 to 2,255 µm/mm(2)], FS-LASIK group: 1,194 ± 485 µm/mm(2) [range: 530 to 1,695 µm/mm(2)], P = .004) postoperatively. No statistically significant difference was detected at 1 week and 6 months postoperatively. CONCLUSION: Eyes treated with SMILE have a higher density of subbasal nerve fibers than eyes treated with FS-LASIK in the early postoperative period (1 week to 3 months) but the two procedures are equivalent by 6 months postoperatively.

Topographic and biomechanical evaluation of corneas in patients with ocular rosacea.

PURPOSE: To compare the topographic and biomechanical properties of corneas in the eyes of patients with ocular rosacea (OR) with those of healthy individuals. METHODS: Thirty-four healthy individuals (control group) and 34 patients with OR (study group) were evaluated in this study. Topographic measurements including keratometry values, irregularity, and surface asymmetry index in the right eye of each participant were obtained using a Scheimpflug camera with a Placido disc topographer (Sirius). Corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOP), and Goldmann-related IOP were measured using the Reichert Ocular Response Analyzer. Central corneal thickness was also measured using ultrasonic pachymetry and the Sirius corneal topography system. RESULTS: Topographic parameters were not significantly different between the groups (P > 0.05). Mean CH and CRF were significantly lower in patients with OR (P = 0.003 and 0.001, respectively). Central corneal thickness was significantly lower in patients with OR compared with healthy controls (P < 0.001). Mean Goldmann-related IOP and corneal-compensated IOP were not significantly different between the groups (P = 0.09 and 0.13, respectively). CONCLUSIONS: This study demonstrated that although the eyes of patients with OR had corneal topographic findings similar to those of healthy controls, corneal biomechanical measurements (CH and CRF) were significantly lower in patients with OR. These results need to be considered when planning corneal refractive surgery in patients with OR.

Evaluation of corneal topography and biomechanical parameters after use of systemic isotretinoin in acne vulgaris.

Purpose. We report the effect of isotretinoin on corneal topography, corneal thickness, and biomechanical parameters in patients with acne vulgaris. Method. Fifty-four eyes of 54 patients who received oral isotretinoin for treatment of acne vulgaris were evaluated. All patients underwent a corneal topographical evaluation with a Scheimpflug camera combined with Placido-disk (Sirius), ultrasonic pachymetry measurements, and corneal biomechanical evaluation with an ocular response analyzer at baseline, in the 1st, 3rd, and 6th months of treatment, and 6 months after isotretinoin discontinuation. Results. The thinnest corneal thickness measured with Sirius differed significantly in the 1st, 3rd, and 6th months compared with the baseline measurement; there was no significant change in ultrasonic central corneal thickness measurements and biomechanical parameters (corneal hysteresis and corneal resistance factor) throughout the study. Average simulated keratometry and surface asymmetry index increased significantly only in the first month of treatment according to the baseline. All changes disappeared 6 months after the end of treatment. Conclusion. Basal tear secretion and corneal morphologic properties were significantly influenced during the systemic isotretinoin treatment and the changes were reversible after discontinuation. No statistical important biomechanical differences were found to be induced by isotretinoin.