Corneal Cross-linking Research Articles

First Experience of Combined Treatment of Corneal and Graft Ulcers in Preschool Children Using Local Ultraviolet Crosslinking (Clinical Cases)

Purpose: to evaluate the results of a new combined method for the treatment of corneal and graft ulcers in preschool children, including local ultraviolet crosslinking (UVA CL) of corneal collagen and amniotic membrane transplantation (AMT).Methods. 1 patient 4 years old with a corneal ulcer and transplant disease after penetrating subtotal keratoplasty and 1 child 6 years old with a corneal ulcer of herpetic etiology was under observation for 1 year. The treatment included 3–5 consecutive procedures of local UVA CL of the cornea lasting 5 min. and amniotic membrane transplantation (AMT) after the first CL procedure. Biomicroscopy with fluorescein test and optical coherence tomography (OCT Spectralis, Heidelberg Engineering, Germany) were used to dynamically monitor the clinical course of corneal and graft ulcers. Local CL was performed using a new Keratolink device (OA Elatomsky Instrument Plant, Russia). Immediately after the 1st CL procedure, a TAM operation was performed under operating conditions under anesthesia, after which 2–4 more local CL procedures were performed sequentially every 3 days.Results. During treatment with each subsequent CL procedure, the clinical condition of the eyes improved: inflammation was relieved, photophobia, lacrimation, blepharospasm disappeared, a gradual increase in the epithelium from the periphery of the cornea with the formation of a gentle translucent opacification was noted, vascular activity decreased, and visual acuity significantly increased. After 2–10 months, in both cases there are no active complaints, the eyes are calm, infiltrates were not determined, in their place a gentle cloud-like translucent opacity formed, including in a child after keratoplasty. Vessels are empty.Conclusion. Combined treatment of corneal and graft ulcers in children (local UVA CL together with TAM) demonstrated high therapeutic efficacy, ensured stable corneal epithelialization in a short time and improved visual functions at the end of the inflammatory process. This method can significantly expand the possibilities of treating ulcerative lesions of the cornea and graft in preschool children.

Five-year results of iontophoresis-assisted transepithelial corneal cross-linking for keratoconus

PurposeTo assess long-term efficacy and safety of iontophoresis-assisted transepithelial corneal cross-linking (I-CXL) for keratoconus.Patients and methodsTwenty-seven eyes of 21 patients (15 M, 6F) affected by progressive keratoconus were evaluated. All subjects were treated with iontophoresis-assisted transepithelial CXL. The patients were examined at baseline and each 6 months after the CXL procedure. Only subjects who completed the follow-up of 5 years were considered in this study. The main outcome measures were uncorrected visual acuity (UCVA), corrected visual acuity (CDVA), corneal transparency and corneal parameters such as K-max, central corneal thickness (CCT) and at the thinnest point, and high-order ocular aberrations (HOAs). The ABCD system was used to determine the progression and re-progression of ectasia.SettingOphthalmology Clinic, University Hospital of Messina, Messina, Italy.ResultsAt 5 years, significant improvements of UCVA from 0.53 ± 0.33 logMAR to 0.4 ± 0.33 logMAR (p = 0.001) and HOAs (p = 0.01) were registered. No significant changes of CDVA (p = 0.4), K-max (p = 0.75), CCT (p = 0.5) were observed at the end of follow-up period.The ABCD system showed re-progression in 25.9% of eyes after 5 years. No adverse events such as corneal opacities and infections were reported.ConclusionsIontophoresis-assisted transepithelial CXL resulted to be safe and effective to stabilize progressive keratoconus in adults at a long-term follow-up.

A Novel Procedure for Keratoconus/Corneal Ectasia Treating Epithelial Compensation of Higher-Order Aberrations, Topographic Guided Ablation, and Corneal Cross Linking - The CREATE+CXL Protocol.

To present the outcomes of a retrospective study in keratoconus/corneal ectasia patients of treating the higher order aberrations compensated for the corneal epithelium in addition to topographic guided ablation followed by corneal cross linking. Twenty-seven eyes of 14 patients were treated for keratoconus/corneal ectasia utilizing trans-epithelial topographic guided ablation photorefractive keratectomy (PRK) for treatment of corneal higher order aberrations and lower order astigmatism followed immediately by 15-minute cross linking were examined retrospectively. Six-month results were analyzed via measurement of vision, refraction, residual higher-order aberrations (HOAs), residual lower-order and higher-order aberrations, as well as for loss or gains of lines of best corrected visual acuity. All eyes save one had reduction in K1, K2, K Max, and K Mean. All eyes had reduction in manifest astigmatism, Contoura measured astigmatism, 57% reduction of higher-order aberrations (HOA), and 53% reduction of higher-order aberrations grouped with lower-order aberrations (Grouped). Nearly all (96.3%) eyes achieved 20/40 vision or better, 20 eyes had 1-7 lines gained of vision, and no eyes had any loss of lines of vision. Use of the CREATE+CXL protocol combined with 15-minute corneal cross linking results in a significant increase in HOA reduction, as well as a significant improvement in corrected distance visual acuity over past procedures.

Long Term Corneal Flattening After Corneal Crosslinking in Patients with Progressive Keratoconus.

We evaluate the long-term visual, refractive, and keratometric outcomes after corneal crosslinking (CXL) in patients with progressive keratoconus (KC) and the incidence of an extreme corneal flattening effect. Oftalmosalud Institute of Eyes, Lima, Perú. Retrospective cohort study. Forty-five eyes that underwent CXL with epithelial removal between June 2006 and September 2011. Data analysis was performed at preoperative evaluation, 1 year postoperatively, and at least 10 years or more postoperatively. Outcome measures included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and Scheimpflug (Pentacam) analysis. Progression was defined by an increase in steep keratometry (Ks) of 1.5D or greater between 2 examinations. Extreme flattening effect was defined as a decrease in K values equal to or greater than 5 diopters (D). Mean follow-up time was 11 ± 1.07 years (range 10-13 years). There was a significant improvement in Ks, UCVA, CDVA, and spherical equivalent at the last visit. The overall rate of progression was 2.22% (1/45). Extreme flattening was observed in 15.5% (7/45) of the eyes, and this was associated with a loss of CDVA in 4.44% (2/45) of the eyes. One eye with corneal flattening of 11.5 D lost 7 lines of CDVA and required corneal transplantation. CXL is a safe and effective procedure to stop the progression of KC with a good overall long-term success rate. Extreme corneal flattening may be more common than commonly recognized, and severe corneal flattening associated with a decrease in CDVA may occur.

A "T.E.S.T." hydrogel bioadhesive assisted by corneal cross-linking for in situ sutureless corneal repair.

Corneal transplantation is an effective clinical treatment for corneal diseases, which, however, is limited by donor corneas. It is of great clinical value to develop bioadhesive corneal patches with functions of "Transparency" and "Epithelium & Stroma generation", as well as "Suturelessness" and "Toughness". To simultaneously meet the "T.E.S.T." requirements, a light-curable hydrogel is designed based on methacryloylated gelatin (GelMA), Pluronic F127 diacrylate (F127DA) & Aldehyded Pluronic F127 (AF127) co-assembled bi-functional micelles and collagen type I (COL I), combined with clinically applied corneal cross-linking (CXL) technology for repairing damaged cornea. The patch formed after 5min of ultraviolet irradiation possesses transparent, highly tough, and strongly bio-adhesive performance. Multiple cross-linking makes the patch withstand deformation near 600% and exhibit a burst pressure larger than 400mmHg, significantly higher than normal intraocular pressure (10-21mmHg). Besides, the slower degradation than GelMA-F127DA&AF127 hydrogel without COL I makes hydrogel patch stable on stromal beds in vivo, supporting the regrowth of corneal epithelium and stroma. The hydrogel patch can replace deep corneal stromal defects and well bio-integrate into the corneal tissue in rabbit models within 4 weeks, showing great potential in surgeries for keratoconus and other corneal diseases by combining with CXL.

Current Surgical Options in the Management of Cataract in Keratoconus Patients

Abstract An ectatic cornea presents unique challenges at the time of cataract surgery. Keratoconus is the most common corneal ectasia, affecting 2–54.5 per 100,000 people. Cataract surgery in keratoconus often yields suboptimal visual outcomes, with < 50% achieving within +/−0.5D of the desired refractive target in mild–moderate disease and worsening to 0%–18% in severe disease. Improving postsurgical visual outcomes requires a multifaceted approach, starting with modification of risk factors and patient education. Disease progression should be halted prior to any final surgical plan, often requiring the use of corneal crosslinking to create long-term stability in keratometry prior to cataract surgery. Inaccurate keratometry is a common and significant source of postoperative refractive error, and recent developments in keratoconus-specific intraocular lens (IOL) power calculations have attempted to address this. Despite the above strategies, correction of postsurgical refractive error may be done using corrective lenses or IOL-based techniques. Additionally, surgical strategies such as topography-guided photorefractive keratectomy, intrastromal ring segments, or corneal allogenic intrastromal ring segments can be performed pre- or postoperatively to enhance vision. This review seeks to provide an overview of the considerations and available strategies for cataract surgery in patients with keratoconus.

Transepithelial corneal crosslinking with oxygen enhancement and pulsed light for progressive ectasia: one-year results.

To evaluate the efficacy and safety of transepithelial accelerated crosslinking (TE-ACXL) using pulsed light and supplemental oxygen. Thirty eyes of 30 consecutive patients with progressive keratoconus or post-LASIK ectasia were enrolled in a prospective non-comparative study conducted at the Magrabi Eye Center (Jeddah, Saudi Arabia). All eyes underwent TE-ACXL with supplemental oxygen. Primary outcome measures were the mean change in corrected distance visual acuity (CDVA) (logMAR) and maximum keratometry (max K) from preoperatively to 12months postoperatively. Secondary outcome measures included change in manifest refractive spherical equivalent (MRSE), refractive cylinder, keratometry, symmetry index (SI), center-surrounding index (CSI) and ectasia index (EI) of the anterior and posterior corneal surfaces, corneal and epithelial thickness at corneal vertex and thinnest location, corneal densitometry, corneal high order aberrations (HOA) and endothelial cell density (ECD). Mean age was 29.6 ± 8.2years. At 1year, the follow up rate was 93.3%. CDVA improved statistically significantly at 12months (p = 0.027). Measures of corneal keratometry or pachymetry did not change significantly (p < 0.05). Postoperatively, a demarcation line was documented in 78.6% eyes at 1month, and in 12 (42.9%) eyes at 12months. The mean depth of the demarcation line was 341.9 ± 49.4µm. Corneal densitometry increased significantly at 1- and 3-months (p < 0.05) and returned to normal levels at 6- and 12-months postoperatively. TE-ACXL with oxygen supplement is effective at halting the progression of corneal ectasia for at least 1year and can be a refractive neutral procedure.

Comparison of standard versus accelerated corneal collagen cross-linking for keratoconus: 5-year outcomes from the Save Sight Keratoconus Registry

ObjectiveTo compare long-term effectiveness of Standard (UV intensity: 3 mW/cm2, duration: 30 min) vs Accelerated (UV intensity: 9 mW/cm2, duration: 10 min) corneal cross-linking (CXL) for stabilising keratoconus.MethodsData for this observational study were captured through a web-based registry system from the routine clinical practice (15 sites across Australia, New Zealand and Italy). The outcomes were compared using mixed-effects regression models. A total of 100 eyes (75 patients) who had standard CXL and 76 eyes (66 patients) who had accelerated CXL, with a follow-up visit at five-year post-CXL were included.ResultsBoth CXL protocols were effective and safe in stabilising keratoconus and improving outcomes. The adjusted mean changes (95% CI) in outcomes were better in standard CXL than in accelerated CXL [visual acuity gain, 10.2 (7.9–12.5) vs 4.9 (1.6–8.2) logMAR letters; pinhole visual acuity 5.7 (3.5–7.8) vs 0.2 (−2.2 to 2.5) logMAR letters; Kmax −1.8 (−4.3 to 0.6) vs 1.2 (−1.5 to 3.9)D; K2 −0.9 (–2.2 to 0.3) vs 0.1 (−1.3 to 1.6)D; MCT –3.0 (−13.7 to 7.7) vs −11.8 (−23.9 to 0.4) µm (p values for visual acuity, pinhole visual acuity, Kmax: <0.05; for K2 and MCT: >0.05)]. The frequency of adverse events at the 5-year follow-up visit was low in both groups [standard, 5 (5%; haze 3; scarring 1, epithelial defect 1) and accelerated 3 (3.9%; haze 2, scarring 1)].ConclusionsBoth standard and accelerated CXL were safe and effective procedures for stabilising keratoconus in the long term. The standard CXL resulted in greater improvements in visual acuity and keratometry.

Management of keratoconus: an updated review.

Keratoconus is the most common corneal ectatic disorder. It is characterized by progressive corneal thinning with resultant irregular astigmatism and myopia. Its prevalence has been estimated at 1:375 to 1:2,000 people globally, with a considerably higher rate in the younger populations. Over the past two decades, there was a paradigm shift in the management of keratoconus. The treatment has expanded significantly from conservative management (e.g., spectacles and contact lenses wear) and penetrating keratoplasty to many other therapeutic and refractive modalities, including corneal cross-linking (with various protocols/techniques), combined CXL-keratorefractive surgeries, intracorneal ring segments, anterior lamellar keratoplasty, and more recently, Bowman's layer transplantation, stromal keratophakia, and stromal regeneration. Several recent large genome-wide association studies (GWAS) have identified important genetic mutations relevant to keratoconus, facilitating the development of potential gene therapy targeting keratoconus and halting the disease progression. In addition, attempts have been made to leverage the power of artificial intelligence-assisted algorithms in enabling earlier detection and progression prediction in keratoconus. In this review, we provide a comprehensive overview of the current and emerging treatment of keratoconus and propose a treatment algorithm for systematically guiding the management of this common clinical entity.

Safety and Efficacy of Corneal Cross-Linking in Patients Affected by Keratoconus: Long-Term Results.

The present study evaluated the effectiveness and safety of corneal collagen cross-linking (CXL). A total of 886 eyes with progressive keratoconus were enrolled in a retrospective cohort study in a tertiary care university hospital. CXL was performed using a standard epithelium-off Dresden protocol. Visual outcomes, maximum keratometry (Kmax), demarcation line measurements, and complications were recorded. Visual outcomes and keratometric data were analyzed in a subgroup comprising 610 eyes. Uncorrected distance visual acuity (UDVA) improved from 0.49 ± 0.38 LogMAR to 0.47 ± 0.39 LogMAR (p = 0.03, n = 610) three years after the procedure, while corrected distance visual acuity (CDVA) improved from 0.15 ± 0.14 LogMAR to 0.14 ± 0.15 LogMAR (p = 0.007, n = 610). A significant reduction of Kmax from 56.28 ± 6.10 to 54.98 ± 6.19 (p < 0.001, n = 610) was observed three years after CXL. In five eyes (0.82%, 5/610) keratoconus progression continued after CXL. Three eyes were retreated successfully with documented refractive and topographic stability after five years. In the 35 eyes that completed 10 years of follow-up, mean visual acuity and topographic parameters remained stable. In conclusion, CXL is a safe and effective treatment for avoiding keratoconus progression. Long-term data are encouraging, supporting a high safety profile for this procedure.

Dexpanthenol/sodium hyaluronate eye drops for corneal epithelial healing following corneal cross-linking in patients with keratoconus.

To evaluate the effect of dexpanthenol 2%/sodium hyaluronate 0.15% eye drops on corneal epithelial healing and corneal microstructural changes following corneal cross-linking (CXL) in patients with keratoconus. The study included 42 eyes of 21 patients with keratoconus who underwent CXL on both eyes. One eye of each patient was instilled dexpanthenol 2%/sodium hyaluronate 0.15% eye drops (DP/SH group) and the fellow eye was instilled unpreserved sodium hyaluronate 0.15% eye drops (SH group). The epithelial healing process was assessed every day until complete reepithelialization was achieved. The in vivo confocal microscopy (IVCM) findings were also recorded. The mean epithelial defect size 48.6 ± 6.7 mm2 for the DP/SH group and 48.2 ± 5.3 mm2 for the SH group. Complete reepithelialization was seen after 2.24 ± 0.44days (range 2-4days) in the DP/SH group and 3.43 ± 0.60days (3 to 5days) in the SH group. Posterior keratocyte density and endothelial cell density were similar in both groups. The mean subbasal nerve plexus density was significantly higher in the DP/SH group (postoperative 1month: 1.13 ± 1.51, 3months: 3.53 ± 2.55, 6months: 7.07 ± 1.42) compared to the SH group (postoperative 1month: 0.87 ± 1.43, 3months: 2.89 ± 2.62, 6months 6.33 ± 1.29). The DP/SH group revealed faster subbasal nerve regeneration and less edema compared to the SH group. Dexpanthenol 2%/sodium hyaluronate 0.15% eye drops were effective and safe for corneal epithelial healing, and promoted faster corneal reepithelialization, nerve regeneration, and keratocyte repopulation with reduced corneal edema compared to sodium hyaluronate eye drops.

Diagnosis and management of keratoconus in the paediatric age group: a review of current evidence.

The diagnosis and management of keratoconus in the paediatric age group presents additional challenges to those encountered in adults. The most significant of these, encountered in some young patients, are delayed presentation of unilateral disease, more advanced disease at diagnosis, difficulty in obtaining reliable corneal imaging, faster rates of disease progression and challenges in contact lens management. The stabilisation effect of corneal cross-linking (CXL), more extensively studied in adults with randomised trials and long-term follow-up, has been much less rigorously examined in children and adolescents. The high heterogeneity of published studies in younger patients, particularly in the choice of tomography parameters designated as primary outcome measures and the definitions of progression, indicates that improved standardisation for future studies on CXL will be necessary. There is no evidence that corneal transplant outcomes in young patients are poorer than those in adults. This review provides a current perspective on the optimal diagnosis and treatment of keratoconus in children and adolescents.

Donor Endothelial Cell Density Not Changed Immediately After Ex Vivo Corneal Cross-Linking

Purpose: The aim of this study was to evaluate the effect of corneal cross-linking on central endothelial cell density (ECD) by comparing masked measurements before and immediately after preparation of cross-linked (CXL) and non–cross-linked (non-CXL) donor corneas. Methods: Thirty donor corneas were randomized 1:1 to either CXL or non-CXL using a modified Dresden protocol. Specular microscopic images of the central corneal endothelium were obtained within 36 hours of recovery and within 3 hours of preparation completion. Images were sent to a central cornea image analysis reading center for ECD determination in a masked, dual-graded manner. Results: Before and after preparation, the mean ECD was 2567 ± 305 cells/mm2 and 2525± 339 cells/mm2 for the CXL group (n =15) and 2652 ± 365 cells/mm2 and 2572 ± 513 cells/mm2 for the non-CXL group (n =15), respectively. The mean difference in ECD before and after preparation was not statistically significant for the CXL and non-CXL groups (P = 0.36; P = 0.31, respectively). In addition, an independent sample t test showed no statistically significant difference in the ECD change between the CXL and non-CXL groups (P = 0.67). Conclusions: Our specular microscopic findings show that ex vivo cross-linking of donor corneas does not seem to produce acute decrease of central endothelial cell density. These findings are encouraging and assist in warranting a clinical trial examining its value in reducing refractive errors and improving postoperative visual outcomes in eyes with keratoconus that undergo keratoplasty.

The Biomechanical E-Staging: In Vivo Biomechanics in Keratoconus.

Belin's ABCD keratoconus classification system allows keratoconus staging based on the criteria of anterior (A) and posterior (B) corneal curvature, thinnest corneal thickness (C), and best spectacle-corrected visual acuity (D). These parameters also provide a progression assessment, but do not take corneal biomechanics into account. The analysis of corneal biomechanics by the Corvis ST (Oculus, Wetzlar, Germany) allows for separation of healthy and keratoconus corneas, based on the Corvis Biomechanical Index (CBI) and the Tomographic Biomechanical Index (TBI). As Corvis ST measurements are highly reliable and are independent of keratoconus severity, a biomechanical parameter was developed for keratoconus corneas based on the linear term of the CBI. This provides biomechanical keratoconus staging. The Corvis Biomechanical Factor (CBiF) is the basis for the introduction of the biomechanical E-staging, which augments the ABCD classification to the ABCDE classification, thus including the cornerstone of corneal biomechanics. This article highlights strengths and limitations of the ABCDE classification. "Unilateral keratoconus" supposedly turns out to be mostly a snapshot of a highly asymmetric keratectasia. Regular astigmatism is sometimes an important differential diagnosis to keratectasia and may be difficult to differentiate from it. Furthermore, the use of the biomechanical E-staging in daily practice for progression assessment of keratoconus and after its treatment by corneal cross-linking or implantation of intracorneal ring segments will be demonstrated and discussed.

Brillouin Spectroscopy in Ophthalmology.

Information about corneal biomechanics is crucial for achieving satisfactory outcomes after surgical corneal interventions, e.g., for astigmatic keratotomies, but also to identify corneas that are at risk for postoperative complications such as corneal ectasia. Hitherto, approaches to characterize corneal biomechanics in an in vivo setting have yielded only minor success, demonstrating the unmet medical need for a diagnostic technique to measure ocular biomechanics. This review shall explain the mechanism of Brillouin spectroscopy and summarize the current scientific knowledge for ocular tissue. PubMed research of relevant experimental and clinical publications, as well as reporting of own experience using Brillouin spectroscopy. Brillouin spectroscopy can measure different biomechanical moduli with a high spatial resolution. Currently, available devices are able to detect focal corneal weakening, e.g., in keratoconus, as well as stiffening after corneal cross-linking. Also, the mechanical properties of the crystalline can be measured. Corneal anisotropy and hydration, together with the dependence on the angle of the incident laser beam in Brillouin spectroscopy, are challenges in the precise interpretation of measured data. A clear advantage in the detection of subclinical keratoconus compared to corneal tomography, however, has not been shown yet. Brillouin spectroscopy is a technique to characterize biomechanical properties of ocular tissue in vivo. Published results confirm ex vivo data of ocular biomechanics; however, further improvements in the acquisition and interpretation of measured data are required until this technique can be used in a clinically viable setting.

Predicting corneal cross-linking treatment efficacy with real-time assessment of corneal riboflavin concentration.

To assess predictability of tissue biomechanical stiffening induced by UV-A light-mediated real-time assessment of riboflavin concentration during corneal crosslinking (CXL) of human donor tissues. Studio Italiano di Oftalmologia, Rome, Italy. Laboratory study. 20 sclerocorneal tissues were randomly stratified to undergo CXL with either the epithelium intact (n = 12) or removed (n = 8). Samples underwent corneal soaking with 0.22% riboflavin formulation (RitSight) with dosing time of t = 10 minutes and t = 20 minutes in epithelium-off and epithelium-on protocols, respectively. All tissues underwent 9-minute UV-A irradiance at 10 mW/cm 2 using theranostic device (C4V CHROMO4VIS). The device used controlled UV-A light irradiation to induce both imaging and treatment of the cornea, providing a real-time measure of corneal riboflavin concentration and treatment efficacy (ie, theranostic score) during surgery. Tissue biomechanics were assessed with an air-puff device (Corvis), which was performed before and after treatment. A 3-element viscoelastic model was developed to fit the corneal deformation response to air-puff excitation and to calculate the mean corneal stiffness parameter (k c ). Significant corneal tissue stiffening ( P < .05) was induced by the theranostic UV-A device in either CXL treatment protocol. Significant correlation was found between the theranostic score and the increase in k c ( R = 0.75; P = .003). The score showed high accuracy (94%) and precision (94%) to predict correctly samples that had improved tissue biomechanical strengthening. Real-time assessment of corneal riboflavin concentration provided a predictive and precise approach for significant improvement of tissue strength on individual corneas, regardless of CXL treatment protocol.

Acoustic Micro-Tapping Optical Coherence Elastography to Quantify Corneal Collagen Cross-Linking

To evaluate changes in the anisotropic elastic properties of exvivo human cornea treated with ultraviolet cross-linking (CXL) using noncontact acoustic micro-tapping optical coherence elastography (AμT-OCE). Acoustic micro-tapping OCE was performed on normal and CXL human donor cornea in an exvivo laboratory study. Normal human donor cornea (n=22) divided into 4 subgroups. All samples were stored in optisol. Elastic properties (in-plane Young's, E, and out-of-plane, G, shear modulus) of normal and ultraviolet CXL-treated human corneas were quantified using noncontact AμT-OCE. A nearly incompressible transverse isotropic model was used to reconstruct moduli from AμT-OCE data. Independently, cornea elastic moduli were also measured with destructive mechanical tests (tensile extensometry and shear rheometry). Corneal elastic moduli (in-plane Young's modulus, E, in-plane, μ, and out-of-plane, G, shear moduli) can be evaluated in both normal and CXL treated tissues, as well as monitored during the CXL procedure using noncontact AμT-OCE. Cross-linking induced a significant increase in both in-plane and out-of-plane elastic moduli in human cornea. The statistical mean in the paired study (presurgery and postsurgery, n=7) of the in-plane Young's modulus, , increased from 19 MPa to 43 MPa, while the out-of-plane shear modulus, G, increased from 188 kPa to 673 kPa. Mechanical tests in a separate subgroup support CXL-induced cornea moduli changes and generally agree with noncontact AμT-OCE measurements. The human cornea is a highly anisotropic material where in-plane mechanical properties are very different from those out-of-plane. Noncontact AμT-OCE can measure changes in the anisotropic elastic properties in human cornea as a result of ultraviolet CXL.

CUSTOMIZED CORNEAL CROSSLINKING WITH EXCIMER LASER ASSISTED EPITHELIUM REMOVAL FOR PROGRESSIVE KERATOCONUS - ONE YEAR RESULTS.

To evaluate the one year visual and tomographic results of customized cross-linking using excimer laser assisted epithelium removal and topography-guided irradiation in the treatment of progressive keratoconus. Coimbra Ophthalmology Unit. Private practice. Coimbra, Portugal. Prospective non-randomized clinical trial. Eyes with documented progressive keratoconus were enrolled. Following de-epithelization with PTK, customized UV irradiation was performed, designed as 3 concentric circular areas centered on the thinnest point (Mosaic System, Avedro, USA). Energy exposure was 5.4J/cm2 in the outer circle and then increased centripetally to 7.2 J/cm2 and 10 J/cm2 . Corrected distance visual acuity (CDVA), refractive outcomes, and Scheimpflug tomographies (Allegro Oculyzer (WaveLight, Germany) were assessed at baseline, and 6 and 12 months postoperatively. This prospective study enrolled 37 eyes of 32 patients. Mean diameter for treated areas was 6.17 ± 0.80, 4.45 ± 0.47, and 2.58 ± 0.14 mm for the outer, medium, and inner circle, respectively. At the 1 year follow-up, mean CDVA improved significantly from 0.38 ± 0.19 to 0.20 ± 0.16 logMAR (p<0.01), with 34 of the 37 eyes (91.89%) retaining or improving CDVA. Mean pre-operative minimum pachimetry decreased from 449.26 ± 41.62 μm to 443.26 ± 41.06 μm (p=0.02). The maximal curvature (Kmax) decreased significantly from 58.50 ± 7.84 D to 57.05 ± 7.27 D (p<0.01). After 1 year, 34 eyes (91.89%) showed no signs of progression. One year after surgery, patients showed a significant improvement in visual acuity while achieving stabilization of disease progression.

Случаи отсутствия лечебного эффекта кросслинкинга при лечении кератоконуса

Purpose. Study of changes in morphometric parameters of cornea in keratoconus before and after corneal collagen crosslinking (CXL). Material and methods. 35 patients (35 eyes) with progressive keratoconus stages 1–3. The indexes of photokeratoscopy were studied in depth (topographer Pentacam (Oculus, Germany). CXL was performed according to the Dresden protocol. A corneal lenticule was used in 6 eyes. The analysis of the studied parameters was carried out initially and after 12 months. Results. By the end of the observation, in all patients, the average values of maximum keratometry (Kmax) decreased statistically significantly from 54.5 to 53.1 diopters, which indicated positive trend. Most indices of keratoconus according to topographer data (ISV, IVA, KI, CKI, IHA, Rmin), as well as the central corneal thickness, on average, significantly decreased. But in 5 patients (all men, mean age 25 years), the Kmax exceeded initial values (from 61.7 to 64.5 diopters), which indicated further progression of keratoconus. The initial values of Kmax in 3 out of 5 of these patients exceeded 57 diopters, which is risk of further progression of keratoconus. Conclusion. With a follow-up period of one year, it was found that CXL in 5 patients (14 %) with keratoconus stages 2-3 turned out to be ineffective. Keywords: keratoconus, photokeratoscopy, corneal collagen crosslinking

Short-Term Effect of Conventional Versus Accelerated Corneal Cross-Linking Protocol on Corneal Geography and Stability.

Purpose: To determine the 6-month effect of conventional (CXL30) and accelerated cross-linking with a UVA intensity of 9 mW/cm2 (CXL10) on corneal stability and to investigate whether there was a difference in ABCD grading system parameters regarding the two different procedures. Methods: Twenty-eight eyes of 28 patients with a documented keratoconus (KN) progression were included. Patients were selected to undergo either epi off CXL30 or CXL10. At the baseline and the follow-up visits after one (V1), three (V2), and six months (V3), the patients underwent complete ophthalmic examination and corneal tomography. Results: In the CXL30 group, all the parameters from the ABCD grading system significantly changed from baseline to V3; parameter A decreased (p = 0.048), B and C increased (p = 0.010, p < 0.001), and D decreased (p < 0.001). In the CXL10 group, there were no changes in parameters A (p = 0.247) and B (p = 0.933), though parameter C increased (p = 0.001) and D decreased (p < 0.001). After an initial decline after one month, visual acuity (VA) recovered on V2 and V3 (p < 0.001), and median maximal keratometry (Kmax) decreased in both groups (p = 0.001, p = 0.035). In the CXL30 group, there were significant changes in other parameters; average pachymetric progression index (p < 0.001), Ambrósio relational thickness maximum (ARTmax) (p = 0.008), front and back mean keratometry (p < 0.001), pachymetry apex (PA) (p < 0.001), and front elevation (p = 0.042). However, in the CXL10 group, there were significant changes only in ARTmax (p = 0.019) and PA (p < 0.001). Conclusion: Both epi-off CXL protocols showed similar short-term efficacy in improving VA and Kmax, halting the progression of KN, and both similarly changed tomographic parameters. However, the conventional protocol modified the cornea more significantly.