Corneal collagen cross-linking for treating keratoconus

Sykakis, Evripidis; Karim, Rushmia; Evans, Jennifer R; Bunce, Catey; Amissah-Arthur, Kwesi N; Patwary, Showrob; McDonnell, Peter J.; Hamada, Samer

doi:10.1002/14651858.cd010621.pub2

Cited by 87 publications

(88 citation statements)

References 79 publications

(1 reference statement)

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“…Our results for isotonic riboflavin show that at 12 months, 41.8% of patients had improved UCVA and 29.7% had improved BSCVA, whereas only 13.4% lost lines of UCVA and 14.9% lost BSCVA. The smaller study by Rechichi et al 11 also demonstrated improvement in the keratometry of treated eyes at 12 months; although modest improvement was demonstrated compared with our treated cohort, a direct comparison with our data cannot be performed 13 as a Placido-disk topographer was used in their study.…”

Section: Discussioncontrasting

confidence: 75%

Corneal collagen crosslinking for keratoconus or corneal ectasia without epithelial debridement

Hirji

Sykakis

Lam

et al. 2015

Eye

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Purpose Corneal collagen crosslinking (CXL) is a relatively new technique to reduce the progression of keratoconus. The technique can be performed with or without complete debridement of the corneal epithelium. We describe a novel intermediate technique involving mechanical disruption of the epithelium, and evaluate its safety and efficacy. Methods The case notes of 128 eyes with progressive keratoconus or iatrogenic corneal ectasia who had undergone CXL using the epithelial disruption technique were retrospectively reviewed. Thin corneas were treated with hypotonic riboflavin. All others were treated with an isotonic solution. Note was made of preoperative and postoperative parameters, including uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, endothelial cell count, and corneal tomography. Occurrence of procedure-related complications was recorded. Statistical analyses were performed using the paired sample t-test and Wilcoxon signedrank test, with a level of Po0.05 being accepted as statistically significant. Results At 12 months, 41.8% of patients treated with isotonic riboflavin had improved UCVA and 29.7% had improved BSCVA. Only 13.4% lost lines of UCVA and 14.9% lost BSCVA. Of the patients treated with hypotonic riboflavin, at 12 months, 75% demonstrated stability of BSCVA and 25% had stable Kmax. In addition, 25% showed improved visual acuity at 12 months, and 58.3% showed regression of their Kmax. Our rate of short-term complications was comparable to studies using complete epithelial removal. Conclusions CXL with epithelial disruption is a safe and effective treatment for keratoconus or iatrogenic corneal ectasia, and may be better tolerated by patients than the epithelium-off technique.

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Section: Discussioncontrasting

confidence: 75%

Corneal collagen crosslinking for keratoconus or corneal ectasia without epithelial debridement

Hirji

Sykakis

Lam

et al. 2015

Eye

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“…[24][25][26] The most commonly used parameter being maximum anterior sagittal curvature (Kmax), which is also frequently applied with respect to determining cross-linking efficacy 27,28 and progression of keratoconus postoperatively. [29][30][31] A number of newly proposed systems use complex keratometric indices to describe progression. 22,26 For example, Kanellopoulos et al looked at seven anterior surface pentacam-derived topometric indices: The index of surface variance (ISV), demonstrating corneal surface irregularity; index of vertical asymmetry (IVA) measuring curvature symmetry with respect to the horizontal meridian; keratoconus index, the ratio of mean radius value in the upper segment to mean radius value in the lower segment; central keratoconus index, the ratio of mean radius value in a peripheral ring to mean radius value in a central ring; index of height asymmetry, a calculation of height data symmetry between the superior and inferior areas with respect to the horizontal meri dian; index of height decentration (IHD), representing the amount of decentration of elevation data in the vertical direction; and minimum radius of curvature, the smallest radius of sagittal corneal curvature, representing the maximum steepness of the cone.…”

Section: Documenting Ectatic Progressionmentioning

confidence: 99%

Assessing Progression of Keratoconus and Cross-linking Efficacy: The Belin ABCD Progression Display

Belin¹,

Meyer²,

Duncan³

et al. 2017

International Journal of Keratoconus and Ectatic Corneal Diseases

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Several methods have been described to both evaluate and document progression in keratoconus and to show efficacy of cross-linking, however, there are no consistent generally accepted parameters. Modern corneal tomography, including both anterior and posterior elevation and pachymetric data can be used to screen for ectatic progression, be employed to detect earlier change and additionally to show efficacy of new treatment modalities, such as crosslinking.To describe specific quantitative values that can be used as progression and efficacy determinants, the normal noise measurements of the three parameters used in the ABCD keratoconus classification (corneal thickness at the thinnest point, anterior and posterior radius of curvature taken from the 3.0 mm optical zone centered on the thinnest point), were determined. Values were obtained from both a normal population and a known keratoconic population. The 80 and 95% one-sided confidence intervals for all three parameters were surprisingly small, suggesting that they may perform well as progression and efficacy determinants.

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“…In contrast, the Cochrane Database of Systematic Reviews conclusion was less convincing and stated that the evidence for the use of CXL in the management of KC was limited due to the lack of properly conducted randomized controlled trials. 53 However, these considerations may still be insufficient to discourage ophthalmologists performing CXL in patients with progressive KC. A recent editorial in the journal Ophthalmology concluded that the recent United States Food and Drug Administraton approval for the technique might have been triggered more by an unmet medical need rather than evidence based medicine.…”

Section: What Is the Place Of CXL Today And In The Future?mentioning

confidence: 99%

Reevaluating the Effectiveness of Corneal Collagen Cross-linking and Its True Biomechanical Effect in Human Eyes

Gatinel¹

2017

International Journal of Keratoconus and Ectatic Corneal Diseases

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The induction of cross-links in corneal tissue appears to be a promising technique to increase its stiffness and this has been the basis of treatment of keratoconus (KC) and corneal ectatic disease. However, there exists a striking discrepancy between the reported biomechanical effects of corneal collagen cross-linking (CXL) in vitro compared to in vivo, and this has not received much attention in the literature. Despite the documentation of an increase in corneal stiffness in vitro by many investigators, reports that provide evidence of measurable and consistent biomechanical changes in corneal rigidity in vivo after CXL are lacking. Indeed, the absence of documented in vivo biomechanical improvement in CXL-treated corneas is a conundrum, which needs to be further explored. To explain this discrepancy, it has been postulated that biomechanical changes induced by CXL are too subtle to be measured by currently available diagnostic tools or have characteristics not discernible by these technologies. However, the dynamic bidirectional applanation device (Ocular Response Analyzer) and dynamic Scheimpflug analyzer instruments (Corvis ST) have demonstrated the ability to quantify even subtle biomechanical differences in untreated KC corneas of different ectatic degree, and document the reduction in corneal hysteresis (CH) and corneal resistance factor (CRF) in situations where the corneal stiffness is reduced, such as after laser in situ keratomileusis and surface ablation procedures. It has also been possible to demonstrate an altered CH and CRF in patients with diabetes, smoking habit, glaucoma, Fuchs’ dystrophy, and corneal edema. It is puzzling that these diagnostic tools could document subtle biomechanical changes in these situations, yet fail to measure the purported changes induced by CXL on corneas with progressive KC. This failure to document significant and consistent biomechanical changes in corneal rigidity could suggest that CXL does not induce a simple reversal of the particular biomechanical deficits that characterize KC, or make the cornea significantly more resistant to bending forces as has been widely postulated. The absence of measurable biomechanical change in living KC corneas after CXL could be a consequence of biomechanical strengthening which is insignificant compared to the marked weakening caused by preexisting alteration of the collagen structure, disorganization of collagen fiber intertwining, and compromised structural–mechanical homogeneity that are hallmarks of keratoconic disease, especially in corneas with progressive KC. The changes in the cornea induced by CXL that have been described in vivo may instead be driven by a wound healing process in response to the removal of the corneal epithelial layer and subsequent exposure to riboflavin and ultraviolet-A (UVA). This paper will present evidence that sustains this hypothesis. How to cite this article Gatinel D. Reevaluating the Effectiveness of Corneal Collagen Cross-linking and Its True Biomechanical Effect in Human Eyes. Int J Kerat Ect Cor Dis 2017;6(1):34-41.

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Corneal collagen cross-linking for treating keratoconus

Cited by 87 publications

References 79 publications

Corneal collagen crosslinking for keratoconus or corneal ectasia without epithelial debridement

Corneal collagen crosslinking for keratoconus or corneal ectasia without epithelial debridement

Assessing Progression of Keratoconus and Cross-linking Efficacy: The Belin ABCD Progression Display

Reevaluating the Effectiveness of Corneal Collagen Cross-linking and Its True Biomechanical Effect in Human Eyes

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