Changes in posterior corneal elevations after combined transepithelial photorefractive keratectomy and accelerated corneal collagen cross-linking: retrospective, comparative observational case series

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.

Comparison of refractive surgeries (SMILE, LASIK, and PRK) with and without corneal crosslinking: systematic review and meta-analysis

Corneal crosslinking (CXL) is used for treating keratoconus and post-laser in situ keratomileusis ectasia. However, refractive surgery is not usually performed with prophylactic CXL. Therefore, we performed a meta-analysis comparing outcomes of refractive surgeries with vs without prophylactic CXL. We systematically searched databases for studies comparing refractive surgeries for myopic correction with vs without prophylactic corneal crosslinking. Review Manager 5.4.1 was used to perform statistical analysis. We included 2820 eyes from 28 studies. Compared with refractive surgery alone, surgery with prophylactic CXL resulted in decreased central corneal thickness, corrected distance visual acuity logMAR, and safety and efficacy indices. There were no significant differences in postoperative uncorrected distance visual acuity of 20/20 or better at ≥12 months and other visual outcomes among both groups. More randomized controlled trials with standard crosslinking protocols are needed to analyze the prophylactic use of crosslinking with refractive surgeries.

Ten-year follow-up of corneal cross-linking and refractive surface ablation in patients with asymmetric corneal topography

Purpose

Compare the safety and efficacy of wavefront-guided photorefractive keratotomy (PRK) 6 months after cross-linking (CXL) to wavefront-guided PRK alone for refractive correction in patients with bilateral asymmetric corneal topography.

Methods

Prospective randomized clinical trial with 16 patients (32 eyes). CXL with subsequent PRK after 6 months in one eye, and PRK alone was performed in contralateral eyes. The follow-up was 10 years. We analyzed visual outcomes, Scheimpflug topography, and corneal haze evaluation.

Results

Eyes in the PRK group showed better results than in the CXL + PRK group. Mean postoperative CDVA was 0.044 logmar (SD, 0.073) in the PRK group and 0.1 logmar (SD, 0.21) in the CXL + PRK group, the mean sphere was + 0.21 (SD, 0.6) D in the PRK group and 0.87 (SD, 2.3) D in the CXL + PRK group, and mean SE was -0.35 (SD, 0.65) D in the PRK group and 0.62 (SD, 2.32) D in the CXL + PRK group. In one patient, a steepening of 2.5 D and a thinning of 17 μm occurred in PRK alone group. Two patients in the CXL + PRK group presented corneal haze. The overall complication rate was 18,75% (haze and ectasia).

Conclusion

Non-simultaneous CXL and PRK procedures yielded good refractive results, but worse than those obtained with PRK alone. Although one patient in the PRK group developed corneal ectasia, the CXL + PRK group had a higher loss of vision lines, indicating less safety.

Laser In Situ Keratomileusis (LASIK) Combined with Prophylactic Corneal Cross-Linking for Correction of Myopia: Regional Analysis of Corneal Morphology

Introduction

Methods

Results

Conclusions

Comparison of safety and efficiency of corneal topography-guided photorefractive keratectomy and combined with crosslinking in myopic correction: An 18-month follow-up

To compare the safety and efficiency of simple corneal topography-guided (T-CAT) photorefractive keratectomy (PRK) and T-CAT PRK combined with crosslinking (CXL) to correct myopia with borderline suspicious tomography.Eyes with suspicious tomography (not classified as forme fruste keratoconus) underwent PRK combined with CXL. The suspicious tomography showed irregular posterior corneal morphology or maximum elevation value of the central 6 mm zone of the posterior surface (MEL) >15 μm, or Belin/Ambrósio Enhanced Ectasia Index (BAD-D) was >1.6. The PRK group was generated and matched within 2 μm for MEL, 0.3 for BAD-D value, and 0.5 D for manifest refractive spherical equivalent (MRSE) compared with the PRK-CXL group.PRK-CXL exhibited a larger MRSE (0.09 ± 0.22 D vs -0.03 ± 0.24 D, P = .02) and a larger sphere (0.14 ± 0.22 D vs 0.01 ± 0.21 D, P = .002) compared with PRK alone at 18 months postoperatively. The magnitude change and relative change rate of stiffness parameter A1 in the PRK-CXL were smaller than in the PRK group (-15.72 ± 14.56 vs -19.95 ± 14.37, P = .04, for magnitude change and -0.16 ± 0.15 vs -0.20 ± 0.14, P = .02, for relative change rate). In the PRK-CXL and PRK groups, 4.8% and 6.9% of eyes suffered grade 0.5 haze at postoperative 18-month. No cases of ectasia were reported in either group.PRK in combination with prophylactic crosslinking showed comparable safety and efficacy, but higher biomechanical stability compared to PRK alone, thus, the additional CXL plays a measurable role in reducing the change in corneal biomechanical properties after PRK in suspicious eyes.

Simultaneous photorefractive keratectomy and accelerated collagen cross-linking in high-risk refractive surgery (Tehran protocol): 3-year outcomes

PURPOSE

To evaluate safety and efficacy of performing simultaneous photorefractive keratectomy (PRK) and collagen cross-linking (CXL) in myopic patients with preoperative risk factors for developing keratectasia.

METHODS

Seventeen eyes of 15 patients with at least one of the following risk factors were recruited: central keratometry (K_max) between 48 and 50, difference between inferior, superior corneal power (I-S value) between 1.4 and 1.9 and corneal thickness between 450 and 480 µm. Upon final stage of standard PRK, 0.02% mitomycin was applied for 30-50 s, and then, accelerated CXL was performed for 5 min. Pre- and postoperative Oculus Pentacam^® imaging for keratometry values, measurement of uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were done for all patients.

RESULTS

Mean follow-up time was 32.08 ± 7.79 months (range 25-49 months). Mean age of patients was 28.78 ± 3.80 years. Mean postoperative spherical equivalent was + 0.19 ± 0.42 (- 0.5 to + 1.0 [D]). Mean UDVA and CDVA improved from 0.9062 ± 0.485 log MAR and 0.0148 ± 0.043 log MAR to 0.0173 ± 0.040 log MAR and 0.0057 ± 0.023 log MAR, respectively (P = 0.011, P = 0.735). Mild degree of early postoperative stromal haze was seen which did not persist more than 6 months. There was no late stromal haze, corneal ectasia or other major postoperative complication in the follow-up period.

CONCLUSION

Combined PRK and accelerated CXL is an efficient and safe procedure for high-risk refractive surgery candidates, with no increased risk of persistent corneal haze.

Two-year follow-up of corneal cross-linking and refractive surface ablation in patients with asymmetric corneal topography

Aims

To evaluate the safety and efficacy of corneal cross-linking (CXL) followed by photorefractive keratectomy (PRK) for refractive correction in patients with bilateral asymmetric topography.

Methods

Forty-four patients (88 eyes) were enrolled in this prospective randomised clinical trial. CXL with subsequent PRK after 6 months was performed in one eye (study group), and PRK alone was performed in contralateral eyes (control group). Patients were followed for 24 months after PRK. Outcome measures investigated included visual acuity (VA), refraction, aberrometry, topography, pachymetry and endothelial cell count. Groups were compared with linear mixed regression and repeated measures logistic regression. Multiple comparison adjustment with the Holm procedure was performed.

Results

At baseline, the logMAR VA (best spectacle corrected) in study and control groups was 0.12±0.13 (mean±SD) and 0.08D±0.14, respectively, and axial inferior–superior index (IS) (topographic IS) in study and control groups were 0.59D±0.31D and 0.58D±0.32D, respectively. After 24 months, a mean under correction of −0.50D was observed in both groups. Change from baseline in logMAR VA in study and control groups was 0.00D±0.08D and −0.02D±0.10D, respectively. Frequency of haze at 30 months in study and control group eyes was, respectively, 18.2% and 4.6% (p=0.05). There was no statistical difference between groups in spherical aberration and coma after adjustment for multiple comparisons.

Conclusions

Non-simultaneous CXL followed by PRK may be performed safely, and refractive results over a 2-year follow-up are highly similar in virgin and previously cross-linked corneas. Despite using mitomycin C, corneal haze can be significantly higher in the first year after PRK in eyes pretreated with CXL.

Standard, transepithelial and iontophoresis corneal cross-linking: clinical analysis of three surgical techniques

BACKGROUND

To evaluate the clinical results of standard, transepithelial (TE) and iontophoresis (I) corneal cross-linking (CXL), in patients with progressive keratoconus.

METHODS

Thirty eyes of 30 patients with progressive keratoconus treated by CXL (10 by standard-CXL, 10 by TE-CXL and 10 by I-TE-CXL) with 12 months of follow-up. Pre- and postoperative ophthalmologic testing were: uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive examination (spherical error, spherical equivalent), corneal topography (corneal astigmatism, simulated maximum, minimum and average keratometry), aberrometry (coma and spherical aberration), pachymetry and endothelial cell density.

RESULTS

In all groups, UDVA and CDVA improved significantly after treatment. Furthermore, a significant improvement in spherical error, spherical equivalent, topographic and aberrometric outcomes was observed in 3 groups at 1 year posttreatment. No significant variations were recorded in corneal thickness and endothelial cellular density.

CONCLUSION

Our results showed efficacy, clinical and refractive stability after standard-CXL, TE-CXL and iontophoresis-CXL.

Corneal collagen cross-linking. A review of its clinical applications

OBJECTIVE

To perform a literature review of the current clinical applications of corneal collagen cross-linking.

METHODS

An exhaustive literature search was made, including the main biomedical databases, and encompassing all years since the introduction of cross-linking in ophthalmology practice.

RESULTS

Corneal collagen cross-linking using UVA irradiation and riboflavin is a surgical technique that is currently being optimised, and is supported by a good amount of pre-clinical and clinical studies. These papers found show the beneficial effect of the surgery on preventing the progression of corneal ectasia, especially keratoconus, but also on pellucid marginal degeneration and keratectasia after refractive surgery. The effect of cross-linking on avoiding the occurrence of iatrogenic keratectasia when combined with a photo-ablative procedure is less clear to date. Additionally, it appears that cross-linking may have a considerable beneficial effect on controlling corneal infection caused by fungi, bacteria and amoebae. However, its effect on viral keratitis can be detrimental. The benefit on bullous keratopathy seems to be rather transient.

CONCLUSIONS

Corneal collagen cross-linking may be used with relative safety and efficacy in patients with progressive keratoconus. Its use could also be considered in patients with other corneal ectasias or with corneal infections of non-viral origin. Currently, there is still a need for more studies as regards its effect on preventing iatrogenic keratectasia.