High-resolution wavefront-guided surface ablation with corneal cross-linking in ectatic corneas: a pilot study

Merging PRK and Collagen Crosslinking: An Analysis of Literature and a Guide to Prevalent Protocols

PURPOSE

The purpose of this review was to summarize the different surgical approaches combining photorefractive keratectomy (PRK) and corneal crosslinking (CXL), present each protocol template in a simple format, and provide an overview of the primary outcomes and adverse events.

METHODS

A literature review was conducted as outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Eight different databases were searched. Papers were included if PRK was immediately followed by CXL.

RESULTS

Thirty-seven papers met the inclusion criteria of a total yield of 823. The latest research into simultaneous PRK and CXL has been shown to not only stabilize the cornea and prevent keratoconus progression but also improve the visual acuity of the patient. Improvements in uncorrected distance visual acuity and (spectacle) corrected distance visual acuity were found to be significant when considering all protocols. There were also significant reductions in K1, K2, mean K, Kmax, sphere, cylinder, and spherical equivalent. Random-effects analysis confirmed these trends. Corrected distance visual acuity was found to improve by an average of 0.18 ± 1.49 logMAR (Cohen's D [CD] 0.12; P <0.02). There was also a significant reduction of 2.57 ± 0.45 D (CD 5.74; P <0.001) in Kmax. Cylinder and spherical equivalent were also reduced by 1.36 ± 0.26 D (CD 5.25; P <0.001) and 2.61 ± 0.38 D (CD 6.73; P <0.001), respectively.

CONCLUSIONS

Combining the 2 procedures appears to be of net benefit, showing stabilization and improvement of ectatic disease, while also providing modest gains in visual acuity. Since customized PRK and CXL approaches appear superior, a combination of these would likely be best for patients.

Refractive surgical approaches to keratoconus: A systematic review and network meta-analysis

Advancements in diagnostic methods and surgical techniques for keratoconus (KC) have increased non-invasive treatment options. Successful surgical planning for KC involves a combination of clinical science, empirical evidence, and surgical expertise. Assessment of disease progression is crucial, and halting the progression should be the focus if it is progressive. While surgeons used to rely on experience alone to decide the surgical method, comparing the network of primary factors, such as visual acuity, across studies can help them choose the most appropriate treatments for each patient and achieve optimal outcomes. Meticulous tabulation methods facilitate interpretation, highlighting the importance of selecting the correct surgical and rehabilitation approach based on each patient's condition and stage of the disease. We detail the outcomes of a comprehensive network meta-analysis comparing the effectiveness of various combined therapeutic refractive treatments for KC at identical stages of the disease, spanning four distinct follow-up intervals. Additionally, the comprehensive analysis suggests that for corneas with optimal best corrected visual acuity (BCVA) preoperatively (classified as regular), combining phakic intraocular lenses with intracorneal ring segments (ICRS) and corneal cross-linking (CXL) could offer the best therapeutic approach provided the disease stage does not exceed stage 3. For irregular corneas, although initial follow-ups show a significant difference in BCVA with surface ablation, longer-term follow-ups recommend combining surface ablation with ICRS and CXL, especially at higher stages.

Simultaneous Topography-guided Custom Ablation With Corneal Cross-linking for Keratoconus: 10-Year Prospective Outcomes

PURPOSE

To assess 10-year visual and tomographic outcomes of topography-guided custom ablation (T-CAT) with corneal cross-linking (CXL) in eyes with keratoconus.

METHODS

T-CAT with CXL was performed in 600 eyes (522 patients). Based on the T-CAT ablation plan, the theoretical maximum ablation depth was 50 µm after epithelium removal. After ablation, accelerated corneal cross-linking (CXL) was performed in the central 8-mm zone (9 mW/cm2 for 10 minutes in "epi-off" mode). The visual acuity and tomography were assessed.

RESULTS

There was significant improvement in uncorrected (P = .001) and corrected (P = .001) distance visual acuity after the procedure. Keratometry, root mean square lower order aberrations and higher order aberrations, defocus, coma 90°, and spherical aberration reduced significantly after surgery at 10 years of follow-up (P < .005). All Pentacam (Oculus Optikgerate GmbH) tomographic variables showed significant changes indicating regularization after T-CAT (P < .005). Flattening of greater than 5.00 diopters in maximum keratometry was noted in 6 eyes (1%). Two of 600 eyes progressed postoperatively and required repeat CXL.

CONCLUSIONS

T-CAT plus CXL is a safe and effective technique even in the long term for regularizing the anterior corneal surface with significant visual improvement and reduction in higher order corneal aberrations. [J Refract Surg. 2023;39(11):759-766.].

Combined photorefractive keratectomy and corneal collagen cross-linking for treatment of keratoconus: a 2-year follow-up study

Background:

Corneal collagen cross-linking (CXL) is considered an effective procedure for slowing down or eliminating the progression of keratoconus. New techniques, in combination with CXL, have been proposed to stop the evolution of keratoconus and improve the visual function.

Objective:

To evaluate the effectiveness of combined photorefractive keratectomy (PRK) with mitomycin-C (MMC) application and CXL in the management of grade 1–2 keratoconus over a 2-year follow-up.

Methods:

Fifteen eyes underwent topography-guided PRK with 0.02% MMC application immediately followed by standard CXL.

Results:

Best corrected visual acuity improved from 0.15 ± 0.11 logMAR to 0.08 ± 0.09 logMAR at 24 months (p < 0.0001) in treated eyes. Mean steepest meridian keratometry reduced from 48.79 ± 3.22 D at baseline to 46.16 ± 3.11 D at 24 months (p < 0.0001). Mean flattest meridian keratometry reduced from 45.18 ± 2.17 D preoperatively to 44.35 ± 2.19 D at 24 months (p < 0.0001).

Conclusion:

Simultaneous topography-guided PRK with MMC 0.02% application and standard CXL is a safe, promising and effective procedure in the treatment of mild and moderate keratoconus.

Keratoconus Management With Customized Photorefractive Keratectomy by Artificial Intelligence Ray-Tracing Optimization Combined With Higher Fluence Corneal Crosslinking: The Ray-Tracing Athens Protocol

PURPOSE

The aim of this study was to report novel ray-tracing customization of surface excimer laser ablation combined with higher fluence corneal crosslinking (CXL) in the stabilization and normalization of ectasia and visual rehabilitation of progressive keratoconus.

METHODS

A 28-year-old man with bilateral progressive keratoconus was treated with Athens protocol: CXL combined with photorefractive surface ablation customized by a novel artificial intelligence platform calculating lower- and higher-order aberrations based on wavefront, Scheimpflug tomography, and interferometry axial length data from a single diagnostic device. Visual acuity, refractive error, keratometry, optical coherence tomography and Scheimpflug tomography, and endothelial cell density were evaluated over 12 months.

RESULTS

Keratoconus stabilized in both eyes. Uncorrected distance visual acuity changed from 20/80 to 20/20 in the OD and from 20/40 to 20/25 in the OS at 12 months. Keratometry changes were as follows: from 40.7 and 42.7 at 165.1 degrees to 41.4 and 43.1 at 169.3 degrees in the OD and from 40.9 and 42.6 at 15.9 degrees to 44.1 and 44.7 at 9.8 degrees in the OS. Corneal surface normalization was as follows: index of height decentration from 0.115 to 0.099 and index of surface variance from 77 to 67 in the OD and index of height decentration from 0.066 to 0.014 and index of surface variance from 49 to 31 in the OS.

CONCLUSIONS

We introduced in this study the management of progressive keratoconus with CXL combined with novel excimer laser customization using several independent up-to-now diagnostics calculated by software, evaluating bidirectional theoretical ray tracing. It bears the potential advantage of addressing more accurately normalization of the distorted human eye optics associated with corneal ectasia, compared with using anterior corneal surface data or wavefront data alone.

Simultaneous Topography-Guided PRK/CXL Versus Topography-Assisted PTK/CXL: 1-Year Prospective Outcomes in Keratoconic Eyes

PURPOSE

To compare 1-year visual and tomographic outcomes of topography-guided photorefractive keratectomy (TGPRK) and topography-assisted phototherapeutic keratectomy (TPTK) with corneal cross-linking (CXL).

METHODS

TGPRK and TPTK were performed in 72 eyes (68 patients) and 74 eyes (71 patients), respectively. Based on the TGPRK ablation plan, the eyes underwent TPTK where the theoretical minimum corneal thickness (MCT) after surgery was less than 400 µm. In the TGPRK group, the theoretical maximum ablation depth was 50 µm after epithelium removal. In TPTK, a decentered single-step PTK was performed only in the steepest anterior curvature zone and the stromal ablation depth was limited to 25 µm. After ablation, accelerated CXL was performed in the central 8-mm zone (9 mW/cm² for 10 minutes in "epithelium-off" mode) in both TGPRK and TPTK. The visual acuity and tomography were assessed.

RESULTS

Improvement in uncorrected (P = .73) and corrected (P = .66) distance visual acuity was similar between the two groups. However, TGPRK eyes had a greater decrease in keratometry, anterior defocus, and spherical aberration (P < .001) at the cost of greater ablation of tissue (P < .001). The median MCT decreased by 27 and 52.5 µm in the TPTK and TGPRK eyes, respectively. Both groups had similar decreases in anterior root mean square of lower (P = .10) and higher (P = .12) order aberrations.

CONCLUSIONS

Both TGPRK and TPTK improved visual acuity in the keratoconic eyes at 1 year of follow-up. However, TPTK removed less volume of tissue. Further, it could be an alternative to TGPRK if the theoretical stromal ablation exceeds 50 µm in thin keratoconic corneas. [J Refract Surg. 2021;37(8):562-569.].

High-Resolution Wavefront-Guided Photorefractive Keratectomy and Accelerated Corneal Crosslinking for Stabilization and Visual Rehabilitation of Keratoconus Eyes

Purpose

To evaluate the visual and refractive outcomes after high-resolution wavefront-guided (HRWG) surface ablation with corneal crosslinking (CXL) in keratoconus eyes.

Patients and Methods

In this prospective, interventional case series, 47 eyes of 28 progressive keratoconus patients older than age 18 were enrolled. All patients underwent HRWG photorefractive keratectomy (PRK) with simultaneous accelerated CXL. The study parameters were manifest refraction spherical equivalent (MRSE), keratometric outcomes, uncorrected (UDVA) and corrected distance visual acuity (CDVA) at postoperative 6 and 12 months.

Results

There was improvement in mean MRSE from -2.39±1.89 D preoperatively to -0.13 ± 0.68 D at 12 months, with corresponding improvement in UDVA from 0.77 ± 0.35 logMAR to 0.08 ± 0.12 logMAR and CDVA from 0.10 ± 0.11 logMAR to 0.02 ± 0.04 logMAR. Preoperative flat and steep keratometry (K) were 4wct 32.49 ± 1.67 D and 45.94 ± 2.10 D, respectively, and at postoperative 12 months were 41.36 ± 2.08 D and 42.65 ± 2.78 D, respectively. At postoperative 12 months, visual and refractive outcomes were maintained. Comparisons between preoperative and postoperative 12 month timepoints were statistically significant for all parameters.

Conclusion

Simultaneous wavefront-guided PRK followed by CXL is a promising treatment for the visual rehabilitation of keratoconus patients.

Combined Protocols for Corneal Collagen Cross-Linking with Photorefractive Surgery for Refractive Management of Keratoconus: Update on Techniques and Review of Literature

With the development and gradual dissemination of corneal collagen cross-linking (CXL) in the twenty-first century as an early treatment for keratoconus, the management paradigm has shifted to include a greater focus on complete refractive correction for these patients. Though supplemental hard contact lens therapy remains a mainstay of visual rehabilitation in keratoconus, there has been increasing appeal in a completely surgical approach by combining CXL with adjuvant refractive procedures to both halt the ectatic process and enhance functional visual outcomes. Collectively termed "CXL plus" procedures, several combined protocols have been studied to various degrees in conjunction with CXL, involving photorefractive keratectomy (PRK), transepithelial phototherapeutic keratectomy (PTK), conductive keratoplasty (CK), intrastromal corneal ring segments (ICRS) implantation, phakic intraocular lens (PIOL) implantation, or multiple of these techniques together. The scope of this review aims to encompass a summary of current CXL protocols and present the current status of studies involving adjunctive keratorefractive procedures combined with CXL. By discussing the results to date of these CXL plus protocols, we can assess what further areas of investigation are necessary within this field as the next step to optimizing treatment modalities and outcomes for our keratoconus patients, regardless of disease severity.