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Corneal haze and visual outcome after collagen crosslinking for keratoconus: A comparison between total epithelium off and partial epithelial removal methods.

ABSTRACT: BACKGROUND:Keratoconus is an asymmetric, bilateral, progressive noninflammatory ectasia of the cornea that affects approximately 1 in 2000 of the general population. This may cause a significant negative impact on quality of life. Corneal collagen crosslinking (CXL) is one of the recently introduced methods that have been used to decrease the progression of keratoconus, in particular, as well as other corneal-thinning processes. MATERIALS AND METHODS:A total of 44 keratoconic eyes of 22 patients were enrolled in this randomized prospective study, after obtaining informed consent. In the first group, the corneal epithelium were totally removed and in the second group, the central 3 mm of epithelium was kept intact and partial removal was performed. After collagen crosslinking in both groups, comprehensive ophthalmologic examination was performed on all patients before and 6 months after the surgery. This article is registered at www.clinicaltrial.gov with registration number NCT01809977. RESULTS:The difference between the two groups was not statistically significant regarding postoperative corneal haziness, refraction, and visual acuity (P > 0.05). However, comparison of pre- and postoperative parameters within each group revealed that total removal of the cornea has resulted in significant improvement of K-max (P value: 0.01) and Q-value (P value: 0.009); while eyes in partial removal group had better improvement of corrected vision (P value: 0.006). Both methods had significant and similar increase in optical corneal density (P < 0.0001). CONCLUSION:In our study, keeping the central corneal epithelium intact was not beneficial for decreasing corneal haziness, however, this method caused better improvement in corrected vision. Total epithelium off technique resulted in better improvement of K-max and Q-value.

SUBMITTER: Razmjoo H

PROVIDER: S-EPMC4260293 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Corneal haze and visual outcome after collagen crosslinking for keratoconus: A comparison between total epithelium off and partial epithelial removal methods.

Razmjoo Hasan H Rahimi Behrooz B Kharraji Mona M Koosha Nima N Peyman Alireza A

Advanced biomedical research 20141129

<h4>Background</h4>Keratoconus is an asymmetric, bilateral, progressive noninflammatory ectasia of the cornea that affects approximately 1 in 2000 of the general population. This may cause a significant negative impact on quality of life. Corneal collagen crosslinking (CXL) is one of the recently introduced methods that have been used to decrease the progression of keratoconus, in particular, as well as other corneal-thinning processes.<h4>Materials and methods</h4>A total of 44 keratoconic eyes ...[more]

PMID: 25538907

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Project description:Corneal collagen crosslinking with riboflavin photosensitization and ultraviolet irradiation is a novel approach to limiting the progression of keratoconus in patients by increasing the elastic modulus of the degenerate cornea. Beneficial reductions in corneal steepness and aberrations after crosslinking also frequently occur. In a previous study, we described a computational modeling approach to simulating topographic progression in keratoconus and regression of disease with corneal collagen crosslinking. In the current study, this model has been expanded and applied to the inverse problem of estimating longitudinal time-dependent changes in the corneal elastic modulus after crosslinking using in vivo measurements from 16 human eyes. Topography measured before crosslinking was used to construct a patient-specific finite element model with assumed hyperelastic properties. Then the properties of the cornea were altered using an inverse optimization method to minimize the difference between the model-predicted and in vivo corneal shape after crosslinking. Effects of assumptions regarding sclera-to-cornea elastic modulus ratio and spatial attenuation of treatment effect due to ultraviolet beam characteristics on the predicted change in elastic modulus were also investigated. Corneal property changes computed by inverse finite element analysis provided excellent geometric agreement with clinical topography measurements in patient eyes post-crosslinking. Over all post-treatment time points, the estimated increase in corneal elastic modulus was 110.8 ± 48.1%, and slightly less stiffening was required to produce the same amount of corneal topographic regression of disease when the sclera-to-cornea modulus ratio was increased. Including the effect of beam attenuation resulted in greater estimates of stiffening in the anterior cornea. Corneal shape responses to crosslinking varied considerably and emphasize the importance of a patient-specific approach.

Project description:PurposeKeratoconus (KC) is characterized by progressive vision loss due to corneal thinning and structural abnormalities. It is hypothesized that KC is caused by deregulated collagen levels and collagen fibril-maturating enzyme lysyl oxidase (LOX). Further, it is currently not understood whether the gene expression deregulated by the corneal epithelium influences KC pathogenesis. We studied (i) the expressions of the LOX, collagen I (COL IA1), collagen IV (COL IVA1), MMP9, and IL6 genes in KC corneal epithelia, (ii) validated their expression levels in patient tissues, and (iii) correlated expression levels with KC disease severity. The primary goal of this study was to evaluate the importance of these genes in the progression of KC.MethodsWe analyzed the gene expression levels of the key proteins LOX, collagens (COL IA1 and COL IVA1), MMP9, and IL6 in debrided corneal epithelia from a large cohort of KC patients (90 eyes) and compared them to control patients (52 eyes) without KC. We measured the total LOX activity in the tears of KC patients compared to controls. We also correlated the protein expression levels of LOX and collagens by immunohistochemistry (IHC) in primary tissues from KC patients (27 eyes) undergoing keratoplasty compared to healthy donor corneas (15 eyes).ResultsWe observed a significant reduction in LOX transcript levels in KC corneal epithelia, and LOX activity in KC tears correlated with disease severity. Collagen transcripts were also reduced in KC while MMP9 transcript levels were upregulated and correlated with disease severity. IL6 was moderately increased in KC patients. IHC demonstrated a reduction in the protein expression levels of LOX in the epithelium and collagen IV in the basement membrane of KC patients compared to healthy donor corneas.ConclusionsThe data demonstrates that the structural deformity of the KC cornea may be dependent on reduced expressions of collagens and LOX, as well as on MMP9 elevated by the corneal epithelium.

Dataset Information

Corneal haze and visual outcome after collagen crosslinking for keratoconus: A comparison between total epithelium off and partial epithelial removal methods.

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Corneal haze and visual outcome after collagen crosslinking for keratoconus: A comparison between total epithelium off and partial epithelial removal methods.

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