Comparison of front-surface corneal topography and Bowman membrane specular topography in keratoconus

Touboul, David; Trichet, Elodie; Binder, Perry S.; Praud, Delphine; Seguy, C.; Colin, Joseph

doi:10.1016/j.jcrs.2012.01.026

Cited by 33 publications

(32 citation statements)

References 24 publications

(27 reference statements)

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“…21 The shape mapped in topography therefore corresponds more closely with the epithelial surface than with the stromal surface. 22 Transepithelial treatment requires an estimation of the epithelial thickness and assumes that the epithelial ablation rate matches that of the stroma. Based on ultrasound biomicroscopic data suggesting a mean central corneal epithelial thickness of 53.4 G 4.6 mm, 23 we used a standard 60 mm PTK as a starting point for treatment.…”

Section: Discussionmentioning

confidence: 99%

“…Although this aberrometry method is not limited by aliasing and scans can be obtained in the presence of significant corneal irregularity, measurement repeatability was poor and our data did not suggest obvious gains in the accuracy of refraction outcomes in topographic PRK from using aberrometry data to help guide the attempted spherocylindrical correction. Because the manifest refraction endpoint is often not clear in the presence of significant irregular astigmatism and because variable thickness epithelial masking 21,22 and differential ablation rates may contribute additional uncertainty, several authors recommend deliberate spherocylindrical undercorrection in topographic PRK. 4 This cautious approach is particularly relevant to topographic PRK combi-ned with corneal collagen crosslinking for keratoconus, 26,27 in which postoperative shape changes induced by crosslinking may compound a trend toward hyperopic overcorrection.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Topography-guided transepithelial photorefractive keratectomy for irregular astigmatism using a 213 nm solid-state laser

Allan¹,

Hassan²

2013

Journal of Cataract and Refractive Surgery

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Topography-guided transepithelial photorefractive keratectomy for irregular astigmatism using a 213 nm solid-state laser

Allan¹,

Hassan²

2013

Journal of Cataract and Refractive Surgery

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“…In addition to halting the ectatic process [22][23][24], CXL results in decrease of corneal curvature irregularity, manifested as central anterior corneal flattening [25,26]. In other words, the overall increase in corneal biomechanics (the stiffening effect over the entire cornea) is invariably accompanied by corneal curvature reduction [27][28][29][30][31].…”

Section: Corneal Collagen Cross-linking For Presbyopia: a Novel Approachmentioning

confidence: 99%

Presbyopic PiXL Cross-Linking

Kanellopoulos

Asimellis

2015

Curr Ophthalmol Rep

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We describe principles and initial clinical findings regarding a novel application of topographically customized collagen cross-linking (CXL) aiming to achieve a modest, nevertheless predictable hyperopic and presbyopic refractive changes. CXL is implemented in a specific, annular section mid-peripherally, employing differential response and biomechanical change, inducing central corneal steepening and asphericity changes. Efficacy, safety, and predictability of this procedure are also presented. This non-laser, minimally invasive technique may be applied either with epithelial removal, offering a more stable result or with a purely non-ablative and non-incisional approach, offering a minimally invasive alternative.

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“…In eyes with KC, this compensatory effect of the corneal epithelium was found to be more pronounced. 52 Interestingly, in these diseased corneas, the magnitude of the reported changes in keratometry after de-epithelialization were higher than that reported after cross-linking. In these keratoconic eyes, the central epithelium was never totally removed before the advent of the CXL procedure, and yet, could remodel itself to provide the anterior corneal surface with an improved contour.…”

Section: Could Epithelial Wound Healing Account For Most Of the Changmentioning

confidence: 71%

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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Comparison of front-surface corneal topography and Bowman membrane specular topography in keratoconus

Cited by 33 publications

References 24 publications

Topography-guided transepithelial photorefractive keratectomy for irregular astigmatism using a 213 nm solid-state laser

Topography-guided transepithelial photorefractive keratectomy for irregular astigmatism using a 213 nm solid-state laser

Presbyopic PiXL Cross-Linking

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

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