Intracorneal Ring Segments Implantation for Corneal Ectasia.

PURPOSE: To provide an overview of the predictability, safety, and efficacy of intrastromal corneal ring segment (ICRS) implantation as a tool to improve visual acuity and its association with other techniques such as corneal collagen cross-linking (CXL), addressing biomechanical outcomes, models, surgical planning and technique, indications, contraindications, and complications in ectatic corneas. METHODS: Literature review. RESULTS: ICRSs have been used to regularize the corneal shape and reduce corneal astigmatism and higher order aberrations, improve visual acuity to acceptable limits, and delay, or eventually prevent, a corneal keratoplasty in keratoconic eyes. Changes in ICRS thickness and size, combination of techniques, and the addition of femtosecond lasers to dissect more foreseeable channels represent an improvement toward more predictable results. Several studies have shown, over time, the long-term efficacy and safety of ICRS treatment for keratoconus, with variable predictability, maintaining the early satisfactory outcomes regarding visual acuity, keratometry, and corneal thickness. It is just as important to ensure that the disease will not progress as it is to improve the visual acuity. Therefore, many studies have shown combined techniques using ICRS implantation and CXL. Also, further limitations of ICRS implantation can be addressed when associated with phakic intraocular lens implantation and photorefractive keratectomy. CONCLUSIONS: ICRS implantation has shown effectiveness and safety in most cases, including combined procedures. In properly selected eyes, it can improve both refraction and vision in patients with keratoconus. [J Refract Surg. 2016;32(12):829-839.].

Accelerated corneal collagen crosslinking: Technique, efficacy, safety, and applications.

Corneal collagen crosslinking (CXL) is an approach used to increase the biomechanical stability of the stromal tissue. Over the past 10 years, it has been used to halt the progression of ectatic diseases. According to the photochemical law of reciprocity, the same photochemical effect is achieved with reduced illumination time and correspondingly increased irradiation intensity. Several new CXL devices offer high ultraviolet-A irradiation intensity with different time settings. The main purpose of this review was to discuss the current use of different protocols of accelerated CXL and compare the efficacy and safety of accelerated CXL with the efficacy and safety of the established conventional method. Accelerated CXL proved to be safe and effective in halting progression of corneal ectasia. Corneal shape responses varied considerably, as did the demarcation line at different irradiance settings; the shorter the exposure time, the more superficial the demarcation line. FINANCIAL DISCLOSURE: Dr. Santhiago is a consultant to Ziemer Ophthalmic Systems AG and Alcon Laboratories, Inc. None of the authors has a financial or proprietary interest in any material or method mentioned.

Corneal Collagen Cross-linking in Advanced Keratoconus: A 4-Year Follow-up Study.

PURPOSE: To analyze the safety and efficacy of standard corneal collagen cross-linking (CXL) in advanced cases of progressive keratoconus after 4 years of follow-up. METHODS: A retrospective case series of patients with advanced progressive keratoconus (stages 3 and 4 of Amsler-Krumeich classification) underwent standard CXL treatment. The parameters examined were changes in uncorrected visual acuity (UDVA), corrected visual acuity (CDVA), keratometry values (mean, flat, steep, and apical), pachymetry, and endothelial cell count at the baseline and at 12, 24, and 48 months postoperatively. RESULTS: Forty eyes of 40 patients were enrolled in the study. The mean patient age was 22.5 years (range: 15 to 37 years). Both mean UDVA and CDVA remained stable during the time points; no statistically significant change was noted. Although a slight reduction was observed in all keratometric readings, a statistically significant reduction was only reached in the apical keratometry (P = .037) at 4 years after CXL. A significant reduction in the corneal thickness was also found (ultrasonic: 388 ± 49 to 379 ± 48 µm; slit-scanning: 362 ± 48 to 353 ± 51 µm); however, this change was likely not clinically meaningful. Endothelial cell count was not significantly different at the end of the study. Treatment failure or progression was noted in two patients (5%) over the follow-up period. CONCLUSIONS: Standard CXL treatment was safe and able to stabilize both visual acuity and topographic parameters at 4 years of follow-up in eyes with advanced keratoconus. [J Refract Surg. 2016;32(7):459-464.].

Advances in femtosecond laser technology.

Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures.

Ectasia risk factors in refractive surgery.

This review outlines risk factors of post-laser in situ keratomileusis (LASIK) ectasia that can be detected preoperatively and presents a new metric to be considered in the detection of ectasia risk. Relevant factors in refractive surgery screening include the analysis of intrinsic biomechanical properties (information obtained from corneal topography/tomography and patient's age), as well as the analysis of alterable biomechanical properties (information obtained from the amount of tissue altered by surgery and the remaining load-bearing tissue). Corneal topography patterns of placido disk seem to play a pivotal role as a surrogate of corneal strength, and abnormal corneal topography remains to be the most important identifiable risk factor for ectasia. Information derived from tomography, such as pachymetric and epithelial maps as well as computational strategies, to help in the detection of keratoconus is additional and relevant. High percentage of tissue altered (PTA) is the most robust risk factor for ectasia after LASIK in patients with normal preoperative corneal topography. Compared to specific residual stromal bed (RSB) or central corneal thickness values, percentage of tissue altered likely provides a more individualized measure of biomechanical alteration because it considers the relationship between thickness, tissue altered through ablation and flap creation, and ultimate RSB thickness. Other recognized risk factors include low RSB, thin cornea, and high myopia. Age is also a very important risk factor and still remains as one of the most overlooked ones. A comprehensive screening approach with the Ectasia Risk Score System, which evaluates multiple risk factors simultaneously, is also a helpful tool in the screening strategy.

Intense Early Flattening After Corneal Collagen Cross-linking.

PURPOSE: To report two cases of significant flattening after corneal cross-linking (CXL) for keratoconus and discuss its potential explanations and implications. METHODS: Observational case report. RESULTS: One year after standard CXL protocol (3 mW/cm(2) for 30 minutes and total energy of 5.4 J/cm(2)), a 28-year-old woman presented a flattening of greater than 14 diopters and a 14-year-old boy presented a flattening of 7 diopters. CONCLUSIONS: Although rare, a significant flattening effect may occur during the first year after CXL, probably related to intense wound healing, increase in corneal elasticity, CXL effective depth, and central cone location. These cases suggest the necessity of a patient-specific approach and a better understanding regarding the actual mechanism behind its potent effect.