Penetrating keratoplasty versus intrastromal corneal ring segments to correct bilateral corneal ectasia: Preliminary study

Corneal Collagen Crosslinking for Ectasia After Refractive Surgery: A Systematic Review and Meta-Analysis

Introduction

Corneal ectasia leads to progressive irregular corneal curvature and reduced visual acuity.

Objective

To assess the safety and effectiveness of corneal collagen cross-linking (CXL) for managing corneal ectasia resulting from refractive laser surgery (RSL).

Methods

A systematic review and meta-analysis were realized according to PRISMA guidelines. We searched PubMed, EMBASE, Cochrane, and Web of Science databases for studies on CXL in patients with ectasia after RLS. The outcomes of interest included visual acuity, refractive outcomes, topographic parameters (Kmax, index surface variance (ISV), index of Vertical Asymmetry (IVA), keratoconus index (KI), central keratoconus index (CKI), index of height asymmetry (IHA), index of height decentration (IHD) and Rmin (minimum sagittal curvature)), central corneal thickness, endothelial cell count, and possible adverse events. Statistical analysis was performed using the R software (version 4.2.3, R Foundation for Statistical Computing, Vienna, Austria).

Results

15 studies encompassing 421 patients (512 eyes) were included. The mean age was 32.03 ± 4.4 years. The pooled results showed a stable uncorrected visual acuity post-CXL, with a significant improvement in corrected distance visual acuity (SMD = 0.09; 95% CI: -0.07 to 0.26). The spherical equivalent decreased significantly (SMD = -0.09; 95% CI: -0.35, -0.02). The topographic parameter Kmax decreased significantly (SMD = 0.15; 95% CI:0.01 to 0.28); however, the other parameters, ISV, IVA, KI, CKI, IHA, IHD, and Rmin, did not change significantly. Central corneal thickness decreased significantly (SMD = 0.24; 95% CI:0.07 to 0.41), and the endothelial cell count remained stable The complications were rare.

Conclusion

CXL is a safe and effective technique for managing corneal ectasia after RLS.

Visual and Topographic Outcomes of Corneal Collagen Cross Linking for Post LASIK Ectasia

Purpose

To assess the topographic and visual outcomes of corneal cross-linking (CXL) for post-LASIK ectasia.

Methods

A retrospective case series of patients who had progressive post-LASIK ectasia, with at least 2 years of follow-up. They had epithelium-off CXL. Topographical and visual changes were recorded.

Results

The study included 21 eyes of 11 patients. At month 24, the final logMAR corrected distance visual acuity (CDVA) and spherical equivalent (SE) were stable compared to baseline (0.16, and −2.0 diopter (D), respectively). The final Kmean and Kmax were 42.5 and 47.4 D, respectively. Stability or improvement in CDVA, SE, and Kmax was seen in 17 eyes (81%). Significant corneal thinning was seen (438 vs 457 microns, p = 0.003). Thinning by 2% or more was seen in 12 eyes (57.1%). Failure of CXL was seen in 4 eyes (19%). No other ocular complications were seen.

Conclusion

CXL for post LASIK ectasia is a safe and effective modality. Despite corneal thinning, there was stability or improvement in topographic parameters and CDVA over the 2-year follow-up period.

Why a dedicated section on keratoconus in the European Journal of Ophthalmology?

Keratoconus is emerging as a new subspecialty in ophthalmology. The literature is booming with publications on the topic as we have better understanding of the pathophysiology, treatment and prognosis of the disease over the past two decades. Advances in diagnostic tools as well as genuine increase in prevalence have shifted perspective of the disease from being a rare one. Early diagnosis is of public health interest as early treatment arrests progression. With the view to encourage research, increase awareness and to reflect the evolution of knowledge related to keratoconus, the European Journal of Ophthalmology has dedicate a special section on keratoconus in its journal.

A review and meta-analysis of corneal cross-linking for post-laser vision correction ectasia

PURPOSE

The aim of this study was to review the safety and stability of cornea cross-linking (CXL) for the treatment of keratectasia after Excimer Laser Refractive Surgery.

METHODS

Eligible studies were identified by systematically searching PubMed, Embase, Web of Science and reference lists. Meta-analysis was performed using Stata 12.1 software. The primary outcome parameters included the changes of corrected distant visual acuity (CDVA), uncorrected visual acuity (UCVA), the maximum keratometry value (Kmax) and minimum keratometry value (Kmin), the surface regularity index (SRI), the surface asymmetry index (SAI), the keratoconus prediction index (KPI), corneal thickness, and endothelial cell count. Efficacy estimates were evaluated by weighted mean difference (WMD) and 95% confidence interval (CI) for absolute changes of the interested outcomes.

RESULTS

Seven studies involving 118 patients treated with CXL for progressive ectasia after laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) (140 eyes; the follow-up time range from 12 to 62 months) were included in the meta-analysis. The pooled results showed that there were no significant differences in Kmax and Kmin values after CXL (WMD = 0.584; 95% CI: -0.289 to 1.458; P = 0.19; WMD = 0.466; 95% CI: -0.625 to 1.556; P = 0.403, respectively). The CDVA improved significantly after CXL (WMD = 0.045; 95% CI: 0.010 to 0.079; P = 0.011), whereas UCVA did not differ statistically (WMD = 0.011; 95% CI: -0.055 to 0.077; P = 0.746). The changes were not statistically significant in SRI, SAI, and KPI (WMD = 0.116; 95% CI: -0.090 to 0.322; P = 0.269; WMD = 0.240; 95% CI: -0.200 to 0.681; P = 0.285; WMD = 0.045; 95% CI: -0.001 to 0.090; P = 0.056, respectively). Endothelial cell count and corneal thickness did not deteriorate (WMD = 12.634; 95% CI: -29.460 to 54.729; P = 0.556; WMD = 0.657; 95% CI: -9.402 to 10.717; P = 0.898, respectively).

CONCLUSION

The study showed that CXL is a promising treatment to stabilize the keratectasia after Excimer Laser Refractive Surgery. Further long-term follow-up studies are necessary to assess the persistence of the effect of the CXL.

Treatment options for advanced keratoconus: A review

Traditionally, the mainstay of treatment for advanced keratoconus (KC) has been either penetrating or deep anterior lamellar keratoplasty (PK or DALK, respectively). The success of both operations, however, has been somewhat tempered by potential difficulties and complications, both intraoperatively and postoperatively. These include suture and wound-healing problems, progression of disease in the recipient rim, allograft reaction, and persistent irregular astigmatism. Taken together, these have been the inspiration for an ongoing search for less troublesome therapeutic alternatives. These include ultraviolet crosslinking and intracorneal ring segments, both of which were originally constrained in their indication exclusively to eyes with mild to moderate disease. More recently, Bowman layer transplantation has been introduced for reversing corneal ectasia in eyes with advanced KC, re-enabling comfortable contact lens wear and permitting PK and DALK to be postponed or avoided entirely. We offer a summary of the current and emerging treatment options for advanced KC, aiming to provide the corneal specialist useful information in selecting the optimal therapy for individual patients.

Continuous corneal intrastromal ring implantation for treatment of keratoconus in an Iranian population

PURPOSE

To evaluate the effect of mechanical implantation of a continuous intrastromal ring in keratoconus.

DESIGN

Prospective, interventional, nonrandomized, case series.

METHODS

The MyoRing (Dioptex GmbH) was implanted after creation of an intrastromal pocket for 95 eyes of 95 patients with moderate and advanced keratoconus. All patients had at least 12 months of follow-up. Preoperative and postoperative visual acuity, keratometry, aberrometry, and refraction were the main outcome measures of the study.

RESULTS

A significant improvement in uncorrected and corrected distance visual acuity was observed 1 month after surgery, which was consistent with the significant reduction in sphere (5.74 diopters [D]) and cylinder (3.02 D). No significant changes were detected in these parameters afterward. Furthermore, a significant corneal flattening of a mean value of 9.78 D was found. Both spherical myopia and astigmatism underwent reduction, but the reduction in myopia was more remarkable than astigmatism. Higher-order aberrations and coma-like aberrations decreased significantly, but spherical aberrations increased after surgery. No significant change in central corneal thickness was observed at any point after operation. There were no significant differences between 2 keratometry groups (higher or lower than 53 D) in visual gain after the procedure. There were no major complications during or after surgery. MyoRing explantation was performed in 4 eyes (4%). The refraction, visual acuity, and corneal topography returned to the preoperative status 1 month later for all 4 eyes.

CONCLUSIONS

MyoRing implantation has an acceptable efficacy profile in moderate and advanced keratoconus.

Evaluation of intrastromal corneal ring segments for treatment of post-LASIK ectasia patients with a mechanical implantation technique

Aim:

To evaluate the clinical outcomes of Keraring segment implantation in patients with post- laser-assisted in situ keratomileusis (LASIK) ectasia, using a mechanical implantation technique.

Materials and Methods:

Twelve eyes of 10 patients with post-LASIK ectasia were enrolled. Intracorneal ring segments (ICRS) were implanted after dissection of the tunnel using Tunc's specially designed dissector under suction. A complete ophthalmic examination was performed, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent, keratometric (K) readings, inferosuperior asymmetry index (ISAI), and ultrasound pachymetry. All 3, 6, and 12-month follow-ups were completed, and statistical analysis was performed.

Results:

The mean preoperative UDVA for all eyes was 1.28 ± 0.59 logMAR. At 12 months, the mean UDVA was 0.36 ± 0.19 logarithm of the Minimum Angle of Resolution (logMAR) (P=0.002), and the mean preoperative CDVA was 0.58 ± 0.3 logMAR, which improved to 0.15 ± 0.12 (P=0.002) at 1 year. There was a significant reduction in cylindrical refractive and spherical equivalent refractive error from –5.29 ± 2.47 diopters (D) and –5.54 ± 5.04 D preoperatively to –1.47 ± 0.71 D and –0.74 ± 1.07 D (P=0.001, P=0.002), respectively, at 1 year. In the same period, the mean K- readings improved from 47.93 ± 4.84 D to 40.87 ± 2.36 D (P=0.002), and the mean ISAI improved from 5.34 ± 3.05 to 2.37 ± 1.68 (P=0.003). No significant changes in mean central corneal thickness were observed postoperatively. There were no major complications during or after surgery.

Conclusion:

ICRS implantation using a unique mechanical dissection technique is a safe and effective treatment for post-LASIK ectasia. All parameters showed improvement at 1-year follow-up.

Intracorneal continuous ring implantation for keratoconus: One-year follow-up

PURPOSE

To evaluate intracorneal continuous ring (ICCR) implantation for the treatment of keratoconus.

SETTING

Eye specialist centers, Europe and Middle East.

METHOD

This study assessed the results of implantation of a MyoRing ICCR in 15 eyes with keratoconus. Outcome measures included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA) (spectacle correction), refraction, complications, and side effects. Postoperative follow-up was up to 1 year.

RESULTS

The study evaluated 15 eyes of 11 patients (8 men, 3 women) with a mean age of 35 years +/- 12 (SD) (range 22 to 60 years). Preoperatively, the mean central corneal thickness was 435 +/- 41 mum (range from 350 to 485 mum) and the mean keratometry (K) readings, 48.96 +/- 3.4 diopters (D) (range 43.75 to 56.62 D). Postoperatively, there was a statistically significant improvement in the UDVA, CDVA, K readings, manifest spherical and cylindrical refractive errors, and spherical equivalent (P<.05). The mean UDVA improved by almost 10 lines, from 0.07 (1.24 +/- 0.35 logMAR) to 0.56 (0.27 +/- 0.17 logMAR), and the mean CDVA improved by almost 3 lines, from 0.42 (0.40 +/- 0.17 logMAR) to 0.77 (0.12 +/- 0.10 logMAR). The mean K reading decreased by 5.76 D, from 48.96 D to 43.20 D. No serious intraoperative complications occurred. Side effects included glare and night-vision problems.

CONCLUSIONS

Treatment of keratoconus with ICCR implantation significantly improved visual function. The nomogram requires grading the disease using the K readings only. The UDVA and CDVA also improved during the first postoperative year.

FINANCIAL DISCLOSURE

Drs. Mahmoud and Venkateswaran have no financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes.

Treatment strategies for corneal ectasia

PURPOSE OF REVIEW

To review the most recent management strategies for corneal ectasia after keratorefractive surgery.

RECENT FINDINGS

Management options for postoperative ectasia include conservative management with various types of contact lenses such as rigid gas permeable lenses, custom wave front-guided soft contact lenses, hybrid lenses and tandem soft contact lens-rigid gas permeable lenses. Minimally invasive surgical options including corneal ring segment implantation with Intacs, KeraRings or Ferrara rings have shown to have good results in the initial period after insertion. However, there appears to be some evidence that this initial effect may regress with time. Collagen cross-linking is also minimally invasive and has been documented to stop the progression of ectasia and in some cases may cause regression. Recently, techniques combining collagen cross-linking with intracorneal ring segments or with topography-guided excimer laser treatments have shown to have promising results.

SUMMARY

Early management of ectasia is essential to prevent its progression and to preserve visual potential. There are several management options that are available that may be used to reduce the need for corneal transplantation for these patients.

Implantation of a complete corneal ring in an intrastromal pocket for keratoconus

PURPOSE

to evaluate the refractive and visual results of a new treatment for keratoconus using the corneal intrastromal implantation system (CISIS).

METHODS

six eyes of four patients with keratoconus were treated with CISIS. Follow-up was 1, 3, and 6 months. After creating an intracorneal pocket of 9-mm diameter and 300-microm depth, a flexible full-ring implant was inserted via a 4-mm-wide corneal tunnel.

RESULTS

no eyes showed loss of lines in uncorrected distance visual acuity (UDVA) or spectacle corrected distance visual acuity (CDVA) at any follow-up examination. Uncorrected and distance corrected visual acuity, keratometry, spherical and cylindrical refractive error as well as spherical equivalent refraction improved significantly (P<.05). Mean UDVA improved from 20/260 to 20/48 and mean CDVA improved from 20/41 to 20/27. A significant centralization and decrease of the corneal apex was found. No intra- or postoperative complications were observed.

CONCLUSIONS

the corneal intrastromal implantation system using a complete ring implanted in a stromal pocket can achieve significant improvements in the visual function of patients with keratoconus. Uncorrected distance visual acuity improved by more than seven lines on average and CDVA improved by two lines.