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      Updates on Managements for Keratoconus

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          Abstract

          Purpose

          Keratoconus is a progressive disease of the cornea which can lead to blindness as irregular astigmatism increases. Currently, a variety of methods are available for the treatment of keratoconus, and in certain cases, it may be difficult to choose the most appropriate option. This article reviews available treatment modalities for keratoconus to provide the practitioner with practical and useful information for selecting the most suitable option for each individual patient.

          Methods

          To review treatment methods for different stages of keratoconus, PubMed (United States National Library of Medicine) and Scopus (Elsevier BV) databases were searched using the keywords “keratoconus”, “contact lens”, “cross-linking”, “Intacs”, “keratoplasty”, “gene therapy”, and “irregular astigmatism”, and related articles were reviewed based on disease assessment parameters and treatment methods.

          Results

          Various methods are available for the treatment of keratoconus: eyeglasses and contact lenses in the early stages, cross-linking for stabilizing disease progression, intrastromal corneal ring segments (ICRS) for reducing refractive errors or flattening the cornea, and penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK), conductive keratoplasty, gene therapy and more recently, bowman layer transplantation (BL transplantation) in advanced stages of the disease. To achieve optimum results, it is essential to choose the best option for each individual patient.

          Conclusions

          A commonality of the reviewed papers was the advancement of novel diagnostic and treatment methods in ophthalmology, which can delay the need for corneal grafting. A better understanding of keratoconus treatment options can help enhance visual rehabilitation and prevent blindness in keratoconus patients.

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          Most cited references188

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          Stress-strain measurements of human and porcine corneas after riboflavin-ultraviolet-A-induced cross-linking.

          To evaluate the biomechanical effect of combined riboflavin-ultraviolet A (UVA) treatment on porcine and human corneas. Department of Ophthalmology, Technical University of Dresden, Dresden, Germany. Corneal strips from 5 human enucleated eyes and 20 porcine cadaver corneas were treated with the photosensitizer riboflavin and irradiated with 2 double UVA diodes (370 nm, irradiance = 3 mW/cm2) for 30 minutes. After cross-linking, static stress-strain measurements of the treated and untreated corneas were performed using a microcomputer-controlled biomaterial tester with a prestress of 5 x 10(3) Pa. There was a significant increase in corneal rigidity after cross-linking, indicated by a rise in stress in treated porcine corneas (by 71.9%) and human corneas (by 328.9%) and in Young's modulus by the factor 1.8 in porcine corneas and 4.5 in human corneas. The mean central corneal thickness was 850 microm +/- 70 (SD) in porcine corneas and 550 +/- 40 microm in human corneas. Riboflavin-UVA-induced collagen cross-linking led to an increase in mechanical rigidity in porcine corneas and an even greater increase in human corneas. As collagen cross-linking is maximal in the anterior 300 microm of the cornea, the greater stiffening effect in human corneas can be explained by the relatively larger portion of the cornea being cross-linked in the overall thinner human cornea.
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            The Genetic and Environmental Factors for Keratoconus

            Keratoconus (KC) is the most common cornea ectatic disorder. It is characterized by a cone-shaped thin cornea leading to myopia, irregular astigmatism, and vision impairment. It affects all ethnic groups and both genders. Both environmental and genetic factors may contribute to its pathogenesis. This review is to summarize the current research development in KC epidemiology and genetic etiology. Environmental factors include but are not limited to eye rubbing, atopy, sun exposure, and geography. Genetic discoveries have been reviewed with evidence from family-based linkage analysis and fine mapping in linkage region, genome-wide association studies, and candidate genes analyses. A number of genes have been discovered at a relatively rapid pace. The detailed molecular mechanism underlying KC pathogenesis will significantly advance our understanding of KC and promote the development of potential therapies.
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              A randomized, controlled trial of corneal collagen cross-linking in progressive keratoconus: three-year results.

              To report the refractive, topographic, and clinical outcomes 3 years after corneal collagen cross-linking (CXL) in eyes with progressive keratoconus. Prospective, randomized controlled trial. One hundred eyes with progressive keratoconus were randomized into the CXL treatment or control groups. Cross-linking was performed by instilling riboflavin 0.1% solution containing 20% dextran for 15 minutes before and during the 30 minutes of ultraviolet A irradiation (3 mW/cm(2)). Follow-up examinations were arranged at 3, 6, 12, 24, and 36 months. The primary outcome measure was the maximum simulated keratometry value (Kmax). Other outcome measures were uncorrected visual acuity (UCVA; measured in logarithm of the minimum angle of resolution [logMAR] units), best spectacle-corrected visual acuity (BSCVA; measured in logMAR units), sphere and cylinder on subjective refraction, spherical equivalent, minimum simulated keratometry value, corneal thickness at the thinnest point, endothelial cell density, and intraocular pressure. The results from 48 control and 46 treated eyes are reported. In control eyes, Kmax increased by a mean of 1.20±0.28 diopters (D), 1.70±0.36 D, and 1.75±0.38 D at 12, 24, and 36 months, respectively (all P <0.001). In treated eyes, Kmax flattened by -0.72±0.15 D, -0.96±0.16 D, and -1.03±0.19 D at 12, 24, and 36 months, respectively (all P <0.001). The mean change in UCVA in the control group was +0.10±0.04 logMAR (P = 0.034) at 36 months. In the treatment group, both UCVA (-0.15±0.06 logMAR; P = 0.009) and BSCVA (-0.09±0.03 logMAR; P = 0.006) improved at 36 months. There was a significant reduction in corneal thickness measured using computerized videokeratography in both groups at 36 months (control group: -17.01±3.63 μm, P <0.001; treatment group: -19.52±5.06 μm, P <0.001) that was not observed in the treatment group using the manual pachymeter (treatment group: +5.86±4.30 μm, P = 0.181). The manifest cylinder increased by 1.17±0.49 D (P = 0.020) in the control group at 36 months. There were 2 eyes with minor complications that did not affect the final visual acuity. At 36 months, there was a sustained improvement in Kmax, UCVA, and BSCVA after CXL, whereas eyes in the control group demonstrated further progression. Copyright © 2014 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.
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                Author and article information

                Contributors
                Journal
                J Curr Ophthalmol
                J Curr Ophthalmol
                Journal of Current Ophthalmology
                Elsevier
                2452-2325
                06 December 2017
                June 2018
                06 December 2017
                : 30
                : 2
                : 110-124
                Affiliations
                [a ]Eye Research Center, Ophthalmology Department, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
                [b ]Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
                [c ]Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran
                Author notes
                []Corresponding author. No. 96 Esfandiar Blvd., Vali'asr Ave., Tehran, Iran. zahra.heidari77@ 123456Yahoo.com
                Article
                S2452-2325(17)30141-5
                10.1016/j.joco.2017.11.002
                6034171
                29988906
                148f223f-b946-44f7-b1ad-db11f6a91310
                © 2017 Iranian Society of Ophthalmology. Production and hosting by Elsevier B.V.

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                History
                : 2 July 2017
                : 7 October 2017
                : 5 November 2017
                Categories
                Article

                keratoconus,contact lens,cross-linking,intacs,keratoplasty,keraflex,gene therapy,bowman layer transplantation

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