Corneal biomechanical changes in eyes with small incision lenticule extraction and laser assisted in situ keratomileusis.

BACKGROUND: Evaluating the corneal biomechanical changes using the Ocular Response Analyzer and the Corvis ST in eyes with incision lenticule extraction (SMILE) and laser assisted in situ keratomileusis (LASIK). METHODS: This is a retrospective study that included 50 eyes equally divided into two groups. The first group included eyes that underwent SMILE procedure using VisuMax® 500 kHz laser system (Carl Zeiss Meditec, Jena, Germany) and the second group included eyes that underwent LASIK procedure using the EX500 Allegretto excimer laser platform (Wavelight GmbH, Erlangen, Germany). The Ocular Response Analyzer (ORA) and the Corvis ST (CST) measured the corneal biomechanical changes before and after the procedures. RESULTS: The ORA showed significant decrease of corneal hysteresis (CH) and corneal resistance factor (CRF) in both groups postoperatively. The percentage of change of CH and CRF were found to be significantly higher in group II. There was no significant difference in the IOP with the ORA and the CST pre and postoperatively in either group. Using CST, the deformation amplitude and HC peak distances increased significantly in both groups. It was also noted that the mean percentage of change of the deformation amplitude was nearly five times higher in group II than group I. CONCLUSION: Both LASIK and SMILE substantially decreased the corneal biomechanical properties with greater reduction in the LASIK group.

Femto-SMILE after photo-therapeutic keratectomy in an eye with failed LASIK flap: A case report.

Purpose: The aim of the study is to describe a case where Femtosecond Intrastromal Lenticule Extraction was used to address the refractive defect following topography-guided phototherapeutic keratectomy (topo-PTK) to regularise a scarred corneal surface after an initial LASIK flap formation attempt failed. Observations: A 23-year-old female experienced a thin and irregular corneal flap, during a microkeratome LASIK surgery of the right eye. Subsequently, she experienced epithelial ingrowth. Three months postoperatively the cornea showed scarring and partial flap melting. Topo-PTK was employed to ablate the scarred surface rendering it regular. Treatment with Femtosecond Intrastromal Lenticule Extraction was performed to correct the final refractive error of Sph -5.50 Cyl -2.00 Axis 180° with a happy end of uncorrected visual acuity (UCVA) of 20/20. Conclusions and Importance: Femtosecond Intrastromal Lenticule Extraction can be used for retreatment after surface ablation. Topo-PTK can be used to ablate post-operative LASIK-induced irregularities with a successful outcome.

Comparison between three different high fluence UVA levels in corneal collagen cross-linking for treatment of experimentally induced fungal keratitis in rabbits.

INTRODUCTION: The aim of this study was to compare the efficacy of Photo-Activated Chromophore for Keratitis - Corneal Collagen Cross-linking (PACK-CXL) of three different total UVA fluence levels and topical voriconazole in treatment of fungal keratitis experimentally induced in rabbits. METHODS: This is an interventional experimental study including both eyes of 16 rabbits (32 eyes). Fungal keratitis was induced by intrastromal injection of Fusarium Solani into the cornea. The rabbits were then divided into four groups (8 eyes for each) from which group A received Voriconazole eye drops and considered as control group. Group B, C, D received single PACK-CXL session with total fluence levels of 7.2, 10.0 and 15.0 J/cm2 for each respectively. Daily clinical examination was recorded and all corneas were removed for microbiology and histopathology on day ten. RESULTS: The mean clinical signs score eyes treated with high fluence PACK-CXL showed evident clinical improvement from fourth to tenth day of treatment. This improvement was equivalent to that of Voriconazole treatment. The results showed better improvement with increasing the UVA total fluence levels but this difference was not statistically significant (P < 0.05). Similarly, the median CFU/ml declined on increasing UVA fluence but with no statistically significant values. Histopathological examination revealed better improvement of inflammatory signs on higher fluence levels compared to lower ones. CONCLUSIONS: High intensity PACK-CXL (30 mW/cm2) was as effective as Voriconazole in the treatment of fungal keratitis in rabbits. Increasing the fluence of UVA was associated with slightly better clinical outcomes with no added risks. More clinical studies are needed to confirm these results.

Ten years experience of corneal collagen cross-linking : An observational study of 6120 cases.

PURPOSE: To study the effect of corneal collagen cross-linking (CXL) using riboflavin and ultraviolet rays on cases of corneal ectasia in keratoconus cases, post-laser-assisted in situ keratomileusis ectasia, and pellucid marginal degeneration and to present its long-term results over many years. METHODS: This study was conducted throughout 10 "years" experience in corneal collagen CXL, including 6120 cases. The study consists of two parts: a retrospective and a prospective part. All patients in the retrospective part were operated by epi-off, while in the prospective part, the epi-on procedure was used. Also, other machines were used as Peschke Vario, Peschke Phoenix, and different types of riboflavin. The results were analyzed using SPSS. RESULTS: The study showed stabilization ectasia in 95% of cases using our standard protocol, and this was proved by topography, pachymetry, refraction, and visual acuity. The effect of CXL was continued in 20% of cases, over a period of 3-5 years, some cases needed to repeat CXL due to the progression of corneal ectasia after cross-linking, in six eyes, that were rubbing their eyes and/or hormonal disturbance. CONCLUSION: Corneal collagen cross-linking CXL is an effective method to prevent the progression of corneal ectasia, whether primary or post-laser-assisted in situ keratomileusis, and the effect was stable over the years of study.

Safety and Indicative Effectiveness of Porcine Corneal Lenticular Implants in Patients with Advanced Keratoconus and Post Lasik Ectasia: A Retrospective Clinical Study.

PURPOSE: This study aimed to evaluate the safety and feasibility of implanting decellularized porcine corneal lenticules in a femtosecond laser-assisted pocket for patients with advanced keratoconus and post-Lasik ectasia. METHODS: This is a retrospective clinical study of implanting a porcine corneal lenticular implant in seven eyes: six with advanced keratoconus and clear cornea and one with advanced post-Lasik ectasia with a follow-up for 12 months. The lenticules are extracted from porcine tissue, subjected to a decellularization process, intensely cross-linked, sterilized and packed. They are 7 mm in diameter with at 100-120-micron thickness. The femtosecond laser was used to create an intra-stromal pocket, and then the lenticules were implanted inside the pocket followed by corneal cross-linking 3 months later for six out of seven eyes. RESULTS: Five patients had keratoconus (6 eyes) and one patient (one eye) had post-Lasik ectasia. Visual acuity improved in all patients except for one case at 6 and 12 months and this was statistically significant (P=0.002 and 0.007). At one-year follow-up, the mean central corneal thickness increased from 389.43 ± 45.41 to 429.33± 63.20 µm, the maximum keratometry decreased from 64.8 ±5.11 to 62.82± 6.16 D, the mean corneal resistance factor (CRT) increased from 5.67 to 8.42, and the total higher-order aberrations decreased from 1.80 to 1.16. Both changes in the CCT and CRF were statistically significant. One eye had wrinkles and opacified graft, and it was exchanged 3 months postoperatively. CONCLUSION: Porcine corneal lenticules implantation is immunologically safe and well tolerated in patients with advanced keratoconus and post-Lasik ectasia and may be feasible as an alternative to keratoplasty.

Long-Term Refractive Outcome of Small Incision Lenticule Extraction in Very High Myopia.

PURPOSE: To assess the stability, safety, predictability, and efficacy of small incision lenticule extraction (SMILE) in high myopia. METHODS: The study was conducted as a retrospective noncomparative analysis of the records of 495 eyes of 270 patients treated by the ReLEx SMILE technique for a mean spherical myopic error of -12.84 ± 2.47 D (range: -10.0 to -14.0 D) combined with a mean astigmatism of -1.17 ± 1.34 D (up to -4.0 D). The mean LogMAR corrected distance visual acuity (CDVA) was 0.2 ± 0.6. In this study, 225 patients had the bilateral SMILE procedure, whereas 45 patients had a single eye treated with SMILE. RESULTS: One month after surgery, the mean refractive error was 20.72 ± 0.88 D (range: +1 to 21.5 D), and the mean postoperative astigmatism was -0.83 ± 1.04 D. The mean LogMAR UDVA was 0.2 ± 0.34. In the last follow-up visit, 3 years after surgery, all the before mentioned parameters were the same or within minimal changes with no statistically significant difference from the earlier results. However, the spherical error demonstrated a significant change from -0.72 ± 0.88 D at 1 month to -1.17 ± 1.01 D at the end of the follow-up. However, this change had an insignificant visual impact. At the end of the follow-up period, approximately 94% of patients had unchanged CDVA or gained one or more lines, 6% lost one line of CDVA, and 1% lost 2 lines. CONCLUSIONS: SMILE may be effective and safe, with a stable and predictable outcome for correction of very high myopia.

Small Incision Lenticule Extraction for Postkeratoplasty Myopia and Astigmatism.

Purpose. To evaluate the visual and refractive outcomes after small incision lenticule extraction (SMILE) for treating myopia and myopic astigmatism after penetrating keratoplasty (PKP). Design. Case-series. Methods. Ten eyes of 10 patients with previous PKP and residual myopic astigmatism for whom pentacam imaging and thickness measurements were acceptable for laser vision correction. Manifest refraction (MR), uncorrected distance visual acuity (UDVA), and corrected distance visual acuity (CDVA) were obtained preoperatively and one day, one week, and one, 3, and 6 months postoperatively. Cases were operated on the VisuMax® femtosecond laser platform with 500 kHz repetition rate. Results. The mean correction ratio for spherical errors was 0.84 ± 0.19 D and for the mean refractive spherical equivalent (MRSE) was 0.79 ± 0.13 D. Vector analysis showed a mean astigmatism reduction at the intended axis of 67 ± 25.25%, a correction index of 0.81 ± 0.21, and an overall mean percentage of success of astigmatism surgery of 53 ± 37.9%. The postoperative MRSE was stable throughout the 6-month follow-up period. The efficacy index was 0.93 and the safety index was 1.12. Conclusion. SMILE for correction of post-PKP myopia and astigmatism is effective, safe, and stable with moderate accuracy and predictability. Centration of the treatment within the grafts was easily performed.

Combined femtosecond laser-assisted intracorneal ring segment implantation and corneal collagen cross-linking for correction of keratoconus.

PURPOSE: To assess the safety, predictability, and effectiveness of Keraring intrastromal corneal ring segments (ICRS) insertion assisted by femtosecond laser and corneal collagen cross-linking (CXL) for keratoconus correction. PATIENTS AND METHODS: In this prospective, noncomparative, and interventional case series, 160 eyes of 100 adult keratoconus patients with poor best-corrected visual acuity (BCVA) (less than 0.7) and intolerance to contact lens wear were included. Patients underwent femtosecond laser-assisted placement of ICRS and CXL. All patients were examined for a complete ophthalmological test: uncorrected visual acuity (UCVA), BCVA, spherical equivalent, keratometry (K1-flat and K2-steep), pachymetry, and Scheimpflug imaging with the Pentacam at 1 week and at 1, 3, and 6 months postoperatively. RESULTS: At 6 months, a significant difference was observed (P<0.001) in mean UCVA and BCVA from 0.92±0.677 and 0.42±0.600 logMAR preoperatively to 0.20±0.568 and 0.119±0.619 logMAR, respectively. Mean spherical equivalent refractions were significantly lower (P<0.001) at 6 months. Mean keratometry (K) also significantly reduced (P<0.001) from 50.93±5.53 D (K1-flat) and 55.37±5.76 D (K2-steep) to 47.32±4.61 and 51.08±5.38 D, respectively. In terms of pachymetry, no significant difference was observed preoperatively versus postoperatively (P=1.000). CONCLUSION: Keraring ICRS insertion assisted by femtosecond laser and corneal CXL provided significant improvement in visual acuity, spherical equivalent, and keratometry, which suggests that it may be effective, safe, and predictable for keratoconus correction.

Contralateral Eye Comparison Between Femtosecond Small Incision Intrastromal Lenticule Extraction at Depths of 100 and 160 µm.

PURPOSE: To compare the visual results, higher-order aberrations, and corneal biomechanical properties of femtosecond small incision lenticule extraction (SMILE) at depths of 100 and 160 µm. METHODS: A prospective comparative interventional clinical trial of a series of patients who underwent SMILE. In the right eye, a refractive lenticule was created at a depth of 100 µm, and in the left eye, a depth of 160 µm was used. Manifest refraction, uncorrected visual acuity, total high-order aberrations (THOA), and corneal biomechanical properties of both eyes were evaluated 1 month postoperatively. RESULTS: Thirty patients with bilaterally stable refractive errors were included in this study. One month postoperatively, mean corneal hysteresis was 9.71 ± 0.68 in the right eyes and 9.97 ± 0.77 in the left eyes, whereas the mean corneal resistant factor was 9.13 ± 1.04 and 9.31 ± 0.92 in the right and left eyes, respectively. Both corneal hysteresis and corneal resistant factor showed statistically significantly higher values in the left eyes (lenticule at a depth of 160 µm). No statistically significant differences were found between the right and the left eyes regarding manifest refraction, uncorrected visual acuity, and THOA. CONCLUSIONS: Creating the refractive lenticule at a depth of 160 µm in SMILE had less effect on the corneal biomechanics than did creating a lenticule at a depth of 100 µm with no statistically significant differences in the refractive outcome and THOA between both groups.