Myriam Cassagne

Iontophoresis Transcorneal Delivery Technique for Transepithelial Corneal Collagen Crosslinking With Riboflavin in a Rabbit Model.

PURPOSE We compared an iontophoresis riboflavin delivery technique for transepithelial corneal collagen crosslinking (I-CXL) with a conventional CXL (C-CXL). METHODS We designed three experimental sets using 152 New Zealand rabbits to study riboflavin application by iontophoresis using charged riboflavin solution (Ricrolin+) with a 1-mA current for 5 minutes. The first set was to compare riboflavin concentration measured by HPLC in corneas after iontophoresis or conventional riboflavin application. The second set was to analyze autofluorescence and stromal collagen modification immediately and 14 days after I-CXL or C-CXL, by using nonlinear two-photon microscopy (TP) and second harmonic generation (SHG). In the third set, physical modifications after I-CXL and C-CXL were evaluated by stress-strain measurements and by studying corneal resistance against collagenase digestion. RESULTS Based on HPLC analysis, we found that iontophoresis allowed riboflavin diffusion with 2-fold less riboflavin concentration than conventional application (936.2 ± 312.5 and 1708 ± 908.3 ng/mL, respectively, P < 0.05). Corneal TP and SHG imaging revealed that I-CXL and C-CXL resulted in a comparable increased anterior and median stromal autofluorescence and collagen packing. The stress at 10% strain showed a similar stiffness of corneas treated by I-CXL or C-CXL (631.9 ± 241.5 and 680.3 ± 216.4 kPa, respectively, P = 0.908). Moreover, we observed an increased resistance against corneal collagenase digestion after I-CXL and C-CXL (61.90% ± 5.28% and 72.21% ± 4.32% of remaining surface, respectively, P = 0.154). CONCLUSIONS This experimental study suggests that I-CXL is a promising alternative methodology for riboflavin delivery in crosslinking treatments, preserving the epithelium.

Whole exome sequencing identifies a mutation for a novel form of corneal intraepithelial dyskeratosis

Background Corneal intraepithelial dyskeratosis is an extremely rare condition. The classical form, affecting Native American Haliwa-Saponi tribe members, is called hereditary benign intraepithelial dyskeratosis (HBID). Herein, we present a new form of corneal intraepithelial dyskeratosis for which we identified the causative gene by using deep sequencing technology. Methods and results A seven member Caucasian French family with two corneal intraepithelial dyskeratosis affected individuals (6-year-old proband and his mother) was ascertained. The proband presented with bilateral complete corneal opacification and dyskeratosis. Palmoplantar hyperkeratosis and laryngeal dyskeratosis were associated with the phenotype. Histopathology studies of cornea and vocal cord biopsies showed dyskeratotic keratinisation. Quantitative PCR ruled out 4q35 duplication, classically described in HBID cases. Next generation sequencing with mean coverage of 50× using the Illumina Hi Seq and whole exome capture processing was performed. Sequence reads were aligned, and screened for single nucleotide variants and insertion/deletion calls. In-house pipeline filtering analyses and comparisons with available databases were performed. A novel missense mutation M77T was discovered for the gene NLRP1 which maps to chromosome 17p13.2. This was a de novo mutation in the probands mother, following segregation in the family, and not found in 738 control DNA samples. NLRP1 expression was determined in adult corneal epithelium. The amino acid change was found to destabilise significantly the protein structure. Conclusions We describe a new corneal intraepithelial dyskeratosis and how we identified its causative gene. The NLRP1 gene product is implicated in inflammation, autoimmune disorders, and caspase mediated apoptosis. NLRP1 polymorphisms are associated with various diseases.

Risk Factors for Progressive Myopia in the Atropine Therapy for Myopia Study

PURPOSE To investigate variables associated with myopic progression despite treatment in the Atropine in the Treatment of Myopia Study. DESIGN Retrospective cohort study. METHODS Two hundred of 400 children were randomized to receive atropine 1% in 1 eye only in this institutional study. Children were followed up with cycloplegic autorefraction every 4 months over 2 years. Children whose myopia progressed by more than 0.5 diopter (D) in the atropine-treated eye at 1 year were classified as being progressors. RESULTS Among the 182 children still in the study at 1 year, 22 (12.1%) were classified as progressors. Univariate analysis suggested these children tended to be younger (8.5 ± 1.4 years vs 9.3 ± 1.5 years; P = .023), to have higher myopic spherical equivalent (SE) at baseline (-3.6 ± 1.3 D vs -2.8 ± 1.4 D; P = .015), and to have 2 myopic parents (77.3% vs 48.1%; P = .012). In nonprogressors, the myopia progression at 1 year was less in the atropine-treated eyes compared with the untreated fellow eye (+0.16 ± 0.37 D vs -0.73 ± 0.48 D; P < .001), but in progressors, progression was more similar between eyes (-0.92 ± 0.31 D vs -1.06 ± 0.44 D; P = .363). Regression analysis showed that the risk of being a progressor was 40% lower with each year of increased age, 43% lower for every 1.0 D less in myopia at baseline, and 59% lower for every 1.0 D less in myopic change in the untreated eyes over the first year. CONCLUSIONS Doctors and parents need to be aware that there is a small group of children (younger, with higher myopia, and greater tendency of myopic progression) who may still progress while receiving atropine treatment.

Customized Topography-Guided Corneal Collagen Cross-linking for Keratoconus

PURPOSE To compare the efficacy and safety of topography-guided corneal collagen cross-linking (TG-CXL) to conventional corneal CXL (C-CXL) in progressive keratoconus. METHODS In this prospective, nonrandomized clinical trial, 60 eyes of 60 patients were scheduled to receive either TG-CXL (30 eyes with deepithelialization focused on the cone, riboflavin application for 10 minutes, and 30 mW/cm2 pulsed ultraviolet-A irradiance pattern according to topography) or C-CXL (30 eyes treated in accordance with the Dresden protocol). Patients were observed for 1 year postoperatively. Maximum keratometry (Kmax), mean keratometry in the inferior part of the cornea (I index), corrected distance visual acuity (CDVA), demarcation line observed in optical coherence tomography, and nerves and cell densities analyzed by confocal microscopy were compared preoperatively and at 1 year postoperatively. RESULTS The difference was significant for both Kmax (P < .01) and I index (P < .01) between the two groups. CDVA improved significantly in the TG-CXL (0.2162 ± 0.2495 logMAR, P < .05) versus the C-CXL (0.2648 ± 0.2574 logMAR, P = .104) group. A stromal demarcation line was observed in both treatment groups, with similar depth at the top of the cone (P = .391), but it was shallower at the surrounding area in the TG-CXL group (P < .0001). Stromal evaluation by confocal microscopy showed less damage and faster healing in the surrounding area than on the cone area in the TG-CXL group. CONCLUSIONS At 1 year postoperatively, TG-CXL seems to be as safe as C-CXL with stronger flattening in Kmax and I index and better improvement in CDVA. TG-CXL induces a biological gradient between the cone and the surrounding area that facilitates nerve and cell recovery. [J Refract Surg. 2017;33(5):290-297.].

First Experience With the ICD 16.5 Mini-Scleral Lens for Optic and Therapeutic Purposes.

Objectives: To evaluate the success rate, efficacy, and safety of the ICD 16.5 mini-scleral gas permeable (GP) contact lens. Methods: This prospective study included referred consecutive patients with irregular corneas and severe ocular surface disease (OSD) in treatment failure. All patients were fitted with the ICD 16.5 mini-scleral GP lens. Even though we had some limited experience with scleral lenses, it was our first experience with the ICD 16.5 mini-scleral GP lens. Efficacy was assessed by comparing best-corrected visual acuity (BCVA) with the mini-scleral lens to baseline BCVA. A subjective visual functioning questionnaire (comfort score, visual quality score, handling rating, and wearing time) was administered in a face-to-face structured interview. Results: Thirty-nine eyes of 23 patients with a mean age of 43±16 years were included. Fitting indications were keratoconus (46%), post-penetrating keratoplasty (21%), other irregular astigmatism (15%), and severe OSD (18%). Twenty-five eyes (64%) were successfully fitted with an 18-month follow-up. The mini-scleral GP lens BCVA was 0.16 logarithm of the minimum angle of resolution (logMAR; 20/25) versus a baseline BCVA of 0.44 logMAR (20/63; P<0.001). Comfort and visual quality scores were 8.5/10 and 7.5/10, respectively. No complications were detected in 96% of the eyes (95% confidence interval, 76.1%–99.4%). One eye experienced corneal graft swelling. Conclusions: The present findings suggest that the ICD 16.5 mini-scleral GP lens is an effective and safe alternative for managing challenging corneas in a therapeutic impasse.

Tomography-Guided Customized CXL.

Tomography-Guided Customized CXL Cassagne et al. should be congratulated for their work on customized corneal cross-linking (CXL) in the May 2017 issue.1 This novel technique has the potential to replace the standard protocol, and that is why we need a clear and contradiction-free presentation of parameters and results. However, the study has some flaws that need to be discussed. First, the maximally used radiant exposure was 15 J/cm2, which clearly exceeds the official exposure limit of 1 J/cm2 as published by the International Commission on Non-Ionizing Radiation Protection.2 Even assuming an absorption of the ultraviolet light by riboflavin, which has been reported to be maximally 90%,3,4 the energy load for intraocular structures is still substantially too high. Second, this is by far not the first report of customized CXL. Our group presented nearly identical results already at the CXL Expert Meeting 2014 and the ESCRS 2015 meeting, and published in the American Journal of Ophthalmology in March 2016.5 Other groups have published similar results regarding customized CXL.6 Third, the presentation of the technique of ultraviolet application is contradictive: on page 291, it reads “superimposed concentric circular zones,” but Figure 1 presents sectorial areas. Which customization was really used? Finally, the title itself includes two misnomers: “topography-guided” and “collagen cross-linking.” Because the authors centered the treatment on the posterior elevation obtained by the Oculyzer, the technique presented would be better characterized as “tomography-guided.” Since 2013, we know that the CXL procedure established additional chemical bonds not only within the collagen molecules of the cornea but also well (and maybe even more important) in the interfibrillar space between proteoglycans forming bridges between the collagen fibers.7 When using the term “collagen cross-linking,” do the authors really refer only to the new chemical bonds within the collagen molecule or to the entire CXL process?

Corneal Collagen Crosslinking Techniques: Updates

Corneal collagen crosslinking (CXL) is usually practiced on keratoconic corneas to strengthen the corneal biomechanical structure. The conventional CXL procedure, with riboflavin and ultraviolet A (UVA), initially involves corneal de-epithelialization to allow riboflavin penetration into the stroma. Discomfort and complications are related to this corneal debridement. Thus, transepithelial CXL has emerged to substitute for the conventional method. This technique preserves the epithelium and tends to ensure the same efficiency of corneal stiffening. To allow riboflavin penetration through the epithelial barrier, several chemical modifications to riboflavin, such as addition of enhancers (EDTA, benzalkonium chloride or 20% alcohol), and osmolar modifications have been applied. The most studied transepithelial riboflavin is Ricrolin TE®, which combines two enhancers: amino alcohol and EDTA. The results of clinical studies have not demonstrated effectiveness yet. Moreover, the iontophoresis technique, a noninvasive procedure during which a low-intensity electric current is applied to enhance the penetration of riboflavin into the stroma, stands out as being as efficient as conventional application of riboflavin, based on a pre-clinical study. Another area of improvement of CXL is modification of the UVA irradiation profile or shortening of the UVA irradiation time while increasing the irradiation power. A longer follow-up and more investigations are still necessary to define the future of transepithelial CXL, but it is an exciting and rapidly evolving area.