Excimer laser treatment combined with riboflavin ultraviolet-A (UVA) collagen crosslinking (CXL) in keratoconus: a literature review

A Clinical Decision Tree to Support Keratoconus Patients Considering Corneal Cross-Linking Combined with Refractive Treatment

BACKGROUND

To develop a fast and frugal decision tree to identify keratoconus patients most likely to benefit visually from the combination of corneal cross-linking (CXL) with topography-guided photorefractive keratectomy ("CXL plus").

PATIENTS AND METHODS

The outcome of interest was an improvement in uncorrected distance visual acuity (UDVA) by at least two lines at the 12-month follow-up. Preoperative and 12-month follow-up data from patients who received CXL plus (n = 96) and CXL only (n = 96) were used in a recursive partitioning approach to construct a frugal tree with three variables (corneal thickness [>/< 430 um], patient interest in CXL plus [yes/no], and tomographic cylinder [</> 3 D]). In addition, we estimated the probability of the outcome from a multivariate logistic regression model for each combination of variables used in the decision tree.

RESULTS

In the complete sample, 101/192 (52.6%) patients improved by at least two lines at the 12-month follow-up. Patients affirmative in all three answers had a 75.6% (34/45) probability of gaining at least two lines of improvement in UDVA by CXL plus. The statistical model estimated a 66.0% probability for a successful outcome.

CONCLUSION

A fast and frugal tree consisting of three variables can be used to select a patient group with a high likelihood to benefit from CXL plus. The tree is useful in the preoperative counseling of keratoconus patients contemplating the CXL plus option, an intervention that is not fully covered by many health insurances.

Indications for keratoplasty in management of corneal ectasia

PURPOSE OF REVIEW

The current review aims to describe recent advancements in treatment of corneal ectasias and its effect on indications for corneal transplantation.

RECENT FINDINGS

The majority of patients affected by ectatic corneal disease use contact lenses to correct resulting astigmatism. Patients who are intolerant of contact lenses or cannot achieve acceptable vision through conservative measures could consider keratoplasty. However, continuing advancements in both nonsurgical and surgical treatments are either reducing or delaying the need for keratoplasty in patients affected by ectatic corneal disease.

SUMMARY

Corneal transplantation has been the mainstay of treatment for patients with advanced ectatic corneal disease. In the past decade, numerous improvements have been occurred to make contact lenses not only more effective for visual correction, but also more comfortable. Although corneal cross-linking is the only proven treatment known to prevent progression of disease, several other therapies show early potential for those in which cross-linking is contraindicated. Patients now have access to a wider range of therapies before considering keratoplasty.

Excimer Laser Corneal Refractive Surgery in the Clinic: A Systematic Review and Meta-analysis

Objective

To systematically evaluate the efficacy, safety, recovery speed, and long-term visual quality of excimer laser corneal refractive surgery and to provide evidence-based medicine for the promotion and use of excimer laser corneal refractive surgery.

Methods

Randomized controls on excimer laser refractive surgery in Web of science, PubMed, EMBASE, ScienceDirect, Cochrane Library, China Knowledge Network (CNKI), China VIP Database, Wan Fang Database, and China Biomedical Literature Database (CBM) were searched by the computer. Randomized controlled trial (RCT) data were extracted independently by two researchers, and the risk of bias of each included RCT was assessed according to the Cochrane Handbook 5.1.0 criteria. Meta-analysis of the collected data was performed using RevMan5.4 statistical software.

Results

In the end, 9 high-quality literatures were included, with a total of 4366 samples, and meta-analysis was used. There was no significant difference in uncorrected visual acuity WMD after excimer laser keratorefractive surgery, but there was a statistically significant difference in WMD in the safety of excimer laser keratorefractive surgery. The results of uncorrected visual acuity (close) indicated the following: Chi2 = 13.56, DF = 5, P = 0.02, and I2 = 100%; the results of uncorrected visual acuity (distance) indicated the following: Chi2 = 34.44, DF =5 (P < 00000), and I2 = 85%; the results of best corrected visual acuity (myopia) indicated the following: Chi2 = 0.65, DF = 3, P = 088 > 0.05, and I2 = 0%; the results of best corrected visual acuity (hyperopia) indicated the following: Chi2 = 1.80, DF = 3, P = 0.61 > 0.05, and I2 = 0%.

Conclusion

Excimer laser corneal refractive surgery is safe and effective, with faster recovery and better long-term visual acuity treatment effect. However, more studies and follow-up with higher methodological quality and longer intervention time are needed for further validation.

Evaluation of the effectiveness of combined staged surgical treatment in patients with keratoconus

Purpose

This study performs comparative assessment of the results of different types of two-stage surgical treatment in patients with keratoconus, including combination of corneal collagen cross-linking with intrastromal corneal ring segments followed by topography-guided photorefractive keratectomy.

Materials and methods

Prospective review of 101 patients (101 eyes) with keratoconus was performed. Patients underwent corneal collagen cross-linking (32 patients), intrastromal corneal ring segments (48 patients), and a combination of these two procedures (21 patients). Transepithelial topography-guided photorefractive keratectomy was performed as the second stage of treatment in all patients with obtained stable refractive results at 8 months after first stage. Main outcome measures were visual acuity (uncorrected distance and corrected distance) and corneal topographic indices.

Results

Comparison of the studied parameters after first stage surgical treatment between non-combined CXL and combined groups demonstrated a statistically significant difference for uncorrected distance visual acuity, corrected distance visual acuity, and cylindrical refraction values (p<0.05). We observed significant improvement of visual acuity and key corneal topographic indices after topography-guided photorefractive keratectomy in all study groups (p<0.05). In 50 (49.5%) patients customized excimer laser ablation gave the possibility of full spherical and cylindrical corrections. Ten eyes (10%) had delayed epithelial healing, no corneal stromal opacities developed.

Conclusions

This study shows that combined two-stage surgical treatment of keratoconus, consisting of intrastromal corneal ring segment implantation with corneal collagen cross-linking followed by topography-guided photorefractive keratectomy, is clinically more effective to prevent keratectasia progression and increase visual acuity than the use of non-combined two-stage techniques.

[Changes in the quality of vision after intrastromal allokeratoplasty for keratoconus (clinical observation)]

Scleral lenses, corneal collagen crosslinking, corneal implants and deep anterior keratoplasty are used to correct deforming changes in the cornea at advanced stages of keratoconus, which improves the quality of vision (QoV). The article presents an analysis of changes in QoV in a 30-year-old patient with stage III keratoconus who underwent intracorneal implantation of an allograft with a width of 2.75 mm and thickness of 300 µm at a depth of 370 µm. The following parameters were measured before and 6 months after the procedure: uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), VA with glare, higher order aberrations (HOA), thickness of the lipid layer of the tear film, spatial contrast sensitivity, visual productivity. Observation results show that the K_max index decreased from 55.9 D to 48.0 D, K_min - from 39.8 D to 39.4 D, UCVA increased from 0.1 to 0.8 and BCVA - from 0.35 to 0.8. Thickness of the lipid layer of the tear film remained the same. The glare effect with different degrees of brightness did not affect visual acuity. Spatial contrast sensitivity in photopic conditions at medium frequencies increased from 19 to 37 dB, at high frequencies from - 0.5 to 22.5 dB, in mesopic conditions at medium frequencies from 11 to 28 dB, at high frequencies from - 0.5 to 12 dB. The «coma» and «spherical» aberrations decreased by 2 and 3 times, respectively, while «trefoil» increased by 3 times. Visual productivity increased by 36.8%. It may be concluded that the use of a wide intrastromal allograft in keratoconus improves the patient's visual quality and visual productivity. At the same time, the «vignetting» effect from the graft side is negligible in photopic conditions and is significant in mesopic conditions.

Excimer laser treatment combined with riboflavin ultraviolet-A (UVA) collagen crosslinking (CXL) in keratoconus: a literature review

PURPOSE

To review the clinical outcome of keratoconus patients after excimer laser treatment with combined riboflavin UV-A collagen crosslinking (CXL) treatment was reviewed in light of the UDVA, CDVA and HOA.

METHODS

Following a PubMed-based literature review of studies on excimer laser treatment with combined riboflavin UV-A CXL published between 2009 and 2018, peer-reviewed English-written studies were evaluated using the GRADE approach ( www.gradeworkinggroup.org ). The current review focused on the change in the (un)corrected distance visual acuity (UDVA; CDVA) and higher-order aberrations (HOA) as well as the prevalence of postoperative complications.

RESULTS

Five studies with a total of 573 eyes were included, thereby reporting on 479 eyes were treated with the aforementioned combination therapy. The control group consisted of 94 eyes in total. Changes between pre- and postoperative CDVA and/or UDVA were statistically significant in all five studies after at least a 24-month follow-up period for the combined excimer laser-assisted CXL treatment in comparison with the CXL-only treatment option. Three studies described statistically significant reduction in the number of total HOA, in particular, those related to coma and spherical aberration. Corneal haze was reported in four studies, but the condition was successfully treated in all cases.

CONCLUSION

Current studies suggest that CDVA, UDVA and HOA in low-to-moderate keratoconic patients improved in a combined treatment without sacrificing biomechanical stability of the cornea. However, long-term results are needed, as the studies in our review have a follow-up period of 68 months or less.