Medium- to Long-Term Results of Corneal Cross-Linking for Keratoconus Using Phototherapeutic Keratectomy for Epithelial Removal and Partial Stromal Ablation

A Standardized Protocol of Simultaneous Transepithelial Phototherapeutic Keratectomy (PTK) Followed by Corneal Collagen Crosslinking for Keratoconus

PURPOSE

To report outcomes in patients with progressive keratoconus who underwent a standardized protocol of transepithelial phototherapeutic keratectomy (t-PTK) laser followed by accelerated corneal collagen crosslinking (CXL).

METHODS

All patients with progressive keratoconus undergoing our protocol at a London clinic between 2019 and 2023 were included. The protocol involved t-PTK at 58-μm central ablation depth at a 9-mm treatment zone on the Schwind Amaris 1050RS platform. Preoperative K readings of 43.0D (both K1 and K2) were inputted for all cases. Patients then underwent CXL with a pulsed-light accelerated protocol (30 mW/cm2 for 8 minutes of UVA exposure time with 1 second on/1 second off).

RESULTS

Seventy-nine eyes from 55 patients were included with an average follow-up of 12 months (range 6-24 months). Both mean uncorrected distance visual acuity (UDVA) and best spectacle-corrected visual acuity improved significantly from 0.42 preoperatively to 0.29 postoperatively (P < 0.01) and 0.11 to 0.06 postoperatively (P < 0.01), respectively. The refractive cylinder reduced significantly from -3.07D to -2.63D (P < 0.05). The mean Km improved from 46.15D to 45.44D (P < 0.01) and mean Kmax from 54.03D to 52.52D (P < 0.01). 77% of eyes (n = 61) exhibited Kmax improvement postoperatively, and 56% showed an improvement in UDVA (n = 44). 16% (n = 13) had worsening of vision, but of these, only 1 patient had visual loss of more than 2 lines. No eyes had corneal haze reported at the final follow-up, and none required additional treatment.

CONCLUSIONS

This standardized simultaneous t-PTK and CXL protocol is safe and effective for the treatment of progressive keratoconus, providing visual, refractive, and topographic improvements.

Three-years outcomes of simultaneous photorefractive surgery and customized corneal cross-linking for keratoconus

PURPOSE

To report the efficacy of customized cross-linking (CXL) in halting progression of keratoconus when combined with photorefractive procedures.

METHODS

Seven eyes from 7 patients with documented progressive keratoconus were treated with customized CXL (customized ultraviolet-A irradiance pattern centered on the maximum posterior elevation with total energy levels ranging from 5.4 up to 10 J/cm2 , and an energy fluence of 9 mW/cm2) combined with photorefractive procedures. Four patients underwent simultaneous transepithelial photorefractive keratectomy (T-PRK) plus customized CXL, and three patients underwent simultaneous transepithelial phototherapeutic keratectomy (T-PTK) plus customized CXL. Tomographic parameters (Kmax, pachymetry of the thinnest point and maximal elevation of posterior float and regularization index) and best spectacle-corrected visual acuity (BSCVA) were compared preoperatively and 3 years postoperatively.

RESULTS

All eyes showed a decrease in the maximal curvature Kmax, and none of eyes showed progression. Six eyes showed a flattening of 3 or more diopters (D). On average, Kmax decreased by - 4.8 ± 2.5 D, and the BSCVA improved by 0.04 ± 0.07 logarithm of the minimal angle of resolution. The mean value of regularization index was 8.7 ± 3.8 D. Mild corneal haze occurred in two eyes, and superficial apical scar occurred in one eye. None of the eyes had a vision-threatening complication.

CONCLUSION

Customized CXL combined with photorefractive procedure (T-PRK/T-PTK) resulted in long lasting flattening effect and strong regularization of keratoconic corneas along with improvement of BSCVA over a 3-year follow-up.

Chemically-Boosted Corneal Cross-Linking for the Treatment of Keratoconus through a Riboflavin 0.25% Optimized Solution with High Superoxide Anion Release

The purpose of this study was to evaluate the effectiveness and safety of a novel buffered riboflavin solution approved for corneal cross-linking (CXL) in progressive keratoconus and secondary corneal ectasia. Following the in vivo preclinical study performed on New Zealand rabbits comparing the novel 0.25% riboflavin solution (Safecross^®) containing 1% hydroxypropyl methylcellulose (HPMC) with a 0.1% riboflavin solution containing 0.10% EDTA, accelerated epithelium-off CXL was performed on 10 patients (10 eyes treated, with the contralateral eye used as control) through UV-A at a power setting of 9 mW/cm² with a total dose of 5.4 J/cm². Re-epithelialization was evaluated in the postoperative 7 days by fluorescein dye test at biomicroscopy; endothelial cell count and morphology (ECD) were analyzed by specular microscopy at the 1st and 6th month of follow-up and demarcation line depth (DLD) measured by anterior segment optical coherence tomography (AS-OCT) one month after the treatment. We observed complete re-epithelization in all eyes between 72 and 96 h after surgery (88 h on average). ECD and morphology remained unchanged in all eyes. DLD was detected at a mean depth of 362 ± 50 µm, 20% over solutions with equivalent dosage. SafeCross^® riboflavin solution chemically-boosted corneal cross-linking seems to optimize CXL oxidative reaction by higher superoxide anion release, improving DLD by a factor of 20%, without adverse events for corneal endothelium.

Corneal cross-linking (CXL) combined with refractive surgery for the comprehensive management of keratoconus: CXL plus

The past two decades have witnessed an unprecedented evolution in the management of keratoconus that demands a holistic approach comprising of inhibiting the ectatic progression as well as visual rehabilitation. The advent of corneal cross-linking (CXL) in the late 1990s resulted in long-term stabilization of the ectatic cornea along with limited reduction in corneal steepening and regularization of corneal curvature. However, CXL as a standalone procedure does not suffice in rehabilitating the functional vision especially in patients who are unwilling or intolerant towards contact lenses. The concept of “CXL plus” was proposed which incorporates adjunctive use of refractive procedures with CXL in order to overcome the optical inefficiency due to corneal irregularity, decrease the irregular astigmatism, correct the residual refractive error and improve functional visual outcome in keratoconus. Several refractive procedures such as conductive keratoplasty (CK), photorefractive keratectomy (PRK), transepithelial phototherapeutic keratectomy (t-PTK), intrastromal corneal ring segments (ICRS) implantation, phakic intraocular lens (PIOL) implantation and multiple other techniques have been combined with CXL to optimize and enhance the CXL outcome. This review aimed to summarize the different protocols of CXL plus, provide guidelines for selection of the optimum CXL plus technique and aid in decision-making for the comprehensive management of cases with primary keratoconus in addition to discussing the future and scope for innovations in the existing treatment protocols.

Central corneal regularization (CCR): an alternative approach in keratoconus treatment

Background

To evaluate the safety and efficacy of an approach that combines corneal customized transepithelial therapeutic ablation to treat irregular corneal optics and accelerated corneal collagen cross-linking (CXL) to strengthen the corneal tissue and stop the progression of keratoconus. The transepithelial therapeutic ablation applied a novel concept named central corneal regularization (CCR) which could correct the corneal morphological irregularities and the eye’s spherocylindrical refractive error with minimal stromal tissue removal.

Methods

Retrospective study. Eyes that underwent CCR combined with CXL were evaluated preoperatively and up to 12 months postoperatively for visual acuity, subjective refraction, corneal haze, pachymetry and maximum keratometry (Kmax).

Results

Twenty four eyes of 24 patients with a mean age of 28.92 ± 9.88 years were treated. The mean spherical equivalent (SE) refractive error changed from − 0.74 ± 1.17 D preoperatively to − 1.05 ± 1.52 D at 12 months postoperatively. The mean uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) improved. No eye lost lines of CDVA, 21 had a mean improvement of 3.21 lines. The mean cylinder error and Kmax value dropped from − 3.06 ± 1.83 D and 51.38 ± 3.29 D to − 1.04 ± 0.80 D and 48.70 ± 2.58 D, respectively. The mean haze score at 3, 6 and 12 months was 0.56, 0.19 and 0.06, respectively.

Conclusions

CCR combined with CXL offers promising results as a safe and effective treatment in keratoconic patients.

Mechanical versus transepithelial phototherapeutic keratectomy epithelial removal followed by accelerated corneal crosslinking for pediatric keratoconus: Long-term results

PURPOSE

To compare the 36-month outcomes of mechanical or transepithelial phototherapeutic keratectomy (PTK) epithelial removal before accelerated corneal crosslinking (CXL) for pediatric keratoconus.

SETTING

Atatürk Training and Research Hospital, Ankara, Turkey.

DESIGN

Retrospective case series.

METHODS

Eyes that had accelerated CXL after mechanical (Group 1) or transepithelial PTK (Group 2) epithelial removal were evaluated preoperatively and 12, 24, and 36 months postoperatively. The uncorrected (UDVA) and corrected distance visual acuities, spherical equivalent (SE), manifest astigmatism, and corneal tomographic and aberrometric parameters were assessed.

RESULTS

The study included 40 eyes of 35 consecutive keratoconus patients younger than 18 years with a 36-month follow-up. Group 1 comprised 15 patients, and Group 2 comprised 20 patients. Both groups had a significant improvement in UDVA (P = .001 and P = .02, respectively) and a significant decrease in maximum keratometry (K) and thinnest corneal thickness (all P < .001) 36 months postoperatively. The improvements in maximum K, topographic astigmatism, and spherical aberration were greater in Group 2 than in Group 1 at 12 months (P = .03, P = .01, and P = .04, respectively). After 12 months, the outcomes in the 2 groups were more similar.

CONCLUSIONS

The initial visual and topographic outcomes of transepithelial PTK ablation were better than those of mechanical epithelium removal before accelerated CXL in pediatric patients with keratoconus. Over the long-term, the results were similar between the 2 groups.