Effect Of Corneal Collagen Cross-linking Research Articles

Effect of corneal collagen cross-linking on quality of life in patients with bullous Keratopathy

Effect of corneal collagen cross-linking on quality of life in patients with bullous Keratopathy

Optical Coherence Tomography and Densitometry in Assessing the Effect of Corneal Collagen Cross-Linking Upon Photorefractive Ablation with Riboflavin

Optical Coherence Tomography and Densitometry in Assessing the Effect of Corneal Collagen Cross-Linking Upon Photorefractive Ablation with Riboflavin

Superior outcome of corneal collagen cross‐linking using riboflavin with methylcellulose than riboflavin with dextran as the main supplement

To compare the effect of corneal collagen cross-linking (CXL) on progressive keratoconus using 0.1% riboflavin with either dextran or methylcellulose as the main supplement. In a comparative case series, CXL was performed in 40 patients (40 eyes) using a riboflavin solution containing either dextran (dextran-riboflavin; n=20) or methylcellulose (methylcellulose-riboflavin; n=20). Changes in central corneal thickness (CCT), Scheimpflug tomography, maximal keratometry reading (Kmax ), visual acuity (VA) and endothelial cell density (ECD) were recorded. Stromal changes one month after surgery were analysed using optical coherence tomography (OCT) and invivo confocal microscopy (IVCM). The CCT was significantly higher in the methylcellulose-riboflavin group during the CXL procedure. The IVCM demarcation line depth was 274±80 (SD) μm in the dextran-riboflavin group and 442±80μm in the methylcellulose-riboflavin group (p<0.001). Complete absence of keratocytes in the pre-endothelial stroma was found in none of the corneas treated with dextran-riboflavin and in 42% of the corneas treated with methylcellulose-riboflavin. Visibility of the OCT demarcation line was significantly lower in the methylcellulose-riboflavin group. Kmax and corrected distance visual acuity were improved in the methylcellulose-riboflavin group and stable in the dextran-riboflavin group after 2years. Endothelial cell density (ECD) was stable in both groups. We found deeper structural changes in the methylcellulose-riboflavin group than in the dextran-riboflavin group. This may be explained by different riboflavin solution properties and raises safety concerns. The study also indicates improved effect using methylcellulose-riboflavin than dextran-riboflavin, possibly explained by deeper stromal CXL effect.

Assessment of Corneal Higher Order Aberrations Before and After Corneal Collagen Cross-Linking in Patients with Keratoconus

Purpose: This study aimed at assessing the shortterm effect of corneal collagen crosslinking on higher order aberrations of cornea in patients with keratoconus using corneal topography. Patients and Methods: The study was a prospective cohort study that was conducted in a private specialized eye hospital on 40 eyes of 28 keratoconus patients. Each patient was fully assessed preoperatively including doing corneal topography using Pentacam® HR. Transepithelial accelerated CXL was done to all patients. Postoperative corneal topography was done at six months and data was retrieved and analyzed. Results: RMS HOA recorded a higher mean value preoperatively, with a high statistically significant difference (p=0.00). All elements of HOAs showed lower postoperative values except for trefoil 30o. The difference was statistically significant in comma 0o, comma 90o, spherical aberrations and fifth order comma 90° (p=0.026, p= 0.003, p=0.005, and p=0.001 respectively). Conclusion: Transepithelial corneal collagen cross-linking improves corneal higher order aberrations. The maximum effect of the procedure is on comma 0o, comma 90o, spherical aberrations and fifth order comma 90° elements.

The clinical study of corneal cross-linking with preserved corneal epithelial flap in thin keratoconic corneas

Objective: To evaluate the therapeutic effect of corneal collagen cross-linking (CXL) with preserved corneal epithelial flap and isotonic riboflavin for treatment of keratoconus eyes with thin corneas. Methods: Prospective case-control study. Twenty two eyes of 20 patients (16 males and 4 females, with age of 23.5±4.9), who have been diagnosed with progressive keratoeonus and the comeal stroma thickness of whom were less than 400μm (without the epithelium), were included in this study. Corneal collagen crosslinking was performed under preserved corneal epithelial flap (8.5mm), followed by instillation of 0.1% riboflavin and then UV irradiation. The corneal epithelial flap must be restored prior to the application of UVA irradiation. Visual acuity, corneal topography and endothelial cell count were evaluated at baseline and at 12 months follow-up. Data were analyzed using paired samples t test. Results: Corneal topography results of 12m before and after the therapy revealed the significant reductions of Kmax from (54.73±4.39)D to (53.46±3.85)D and Kmin from (48.97±3.72)D to (48.41±3.17)D, and also Km from (51.67±3.77) D to (50.77±3.28) D (Kmax: t=-3.138, P<0.05; Kmin: t=-2.170, P<0.05; Km: t=-3.532, P<0.05). No statistically significant differences were found between the average corneal thickness of pre therapy [(400.6±14.9) μm] and post therapy [(396.5±16.3)μm] (t=1.973, P>0.05). Endothelial cell counts of pre therapy [(2 824±308)/mm(2)] and post therapy [(2 753±372)/mm(2)] were of no statistical significance as well (t=0.928, P>0.05). No complications such as scarring lesions in the stroma and corneal endothelial damage were observed throughout the study period. Most of the patient's vision improved after treatment. Conclusion: The application of isotonic ribonavin solution in a cross-linking procedure in thin corneas with preserved corneal epithelial flap seems to be safe and effective as keratoconus tend to be stable at 12 months after therapy and no endothelial cell damage was caused. (Chin J Ophthalmol, 2018, 54: 421-425).

Comparison of Corneal Collagen Cross-Linking Protocols Measured With Scheimpflug Tomography.

To evaluate the effectiveness of corneal collagen cross-linking with Dresden and accelerated protocols to treat keratoconus by Scheimpflug tomography. Fifty-eight eyes with manifest keratoconus were measured preoperatively at least twice with the Pentacam. The difference of relevant variables for keratoconus progression (eg, D value, thinnest pachymetry, Kmax) was established. After evident progression, patients underwent corneal cross-linking (29 eyes with the Dresden protocol and 29 eyes with the accelerated protocol). Postoperatively, variables used for defining manifest progression were compared again by measuring the difference between 2 measurements. Preoperatively, the mean D value was 9.6 ± 4.8 for the Dresden cohort and 8.3 ± 5.1 for the accelerated cohort. There was no significant difference between both cohorts in terms of the mean preoperative difference in the D value (0.59 ± 1.7 for the Dresden cohort vs. 0.4 ± 1.49, P = 1). Postoperatively, however, a significant difference (P < 0.01 for the accelerated corhort) was found (Dresden: -0.47 ± 0.88 vs. accelerated: 0.04 ± 0.67). Regression analysis showed that keratoconus progression was significant in both study groups preoperatively (with a significant reduction of corneal thickness and increase in the D value). Postoperative data show an improvement in all observed keratoconus indices in both study groups and stagnation in progression for the accelerated cohort, P = 0.774, for the D value and a regression in manifestation for the Dresden cohort (decrease in the D value, P < 0.01). Before operative intervention, Scheimpflug imaging showed signs of a progressive disease in all eyes. Both conventional Dresden protocol and accelerated pulsed corneal collagen cross-linking techniques effectively stopped this progression.

Antimicrobial efficacy of corneal cross-linking in vitro and in vivo for Fusarium solani: a potential new treatment for fungal keratitis

BackgroundFungal keratitis is one of the major causes of visual impairment worldwide. However, the effectiveness of corneal collagen cross-linking (CXL) for fungal keratitis remains controversial. In this study, we developed an in vitro and an in vivo models to assess the efficacy of CXL for Fusarium keratitis.MethodsThe effect of in vitro CXL fungicidal was evaluated on the cultures of Fusarium solani which were exposed to irradiation for different durations. Viability of fungal was appraised under four conditions: no treatment (control); CXL: UVA (365 nm)/riboflavin; riboflavin and UVA (365 nm). Each batch of sterile plate culture was irradiated for different CXL durations.The in vivo Therapeutic effect was studied on a mouse keratitis model. The animals were divided randomly into three groups: group A with no treatment (control); Group B with CXL treatment for two minutes and group C with CXL treatment for three minutes. The CXL procedure was performed 24 h post inoculation in each group. All mice with corneal involvement were scored daily for 7 days and 10 days after infection. Corneals were extracted at various time points for quantitative fungal recovery. Histological evaluations were conducted to calculate the number of polymorphonuclear cells.ResultsViability of fungal decreased significantly in CXL group with 30-min irradiation compared with that in control, riboflavin and UVA groups (P < 0.01).The colony-forming units (CFUs) of fungal solutions in culture significantly decreased with CXL treatment (P < 0.05). Clinical scores, corneal lesion, corneal opacity, neovascularization and the depth of ulceration scores in group B and group C were remarkably lower than that in group A (P < 0.05, P = 0.001, P = 0.001, P = 0.034 and P = 0.025 respectively). Scores of group C were much lower than that in group B. Histological revealed that destruction of corneal collagen fibers and infiltration of inflammatory cells into corneal tissue in group B and group C were much lower than that in group A.ConclusionsWe believe that CXL treatment may be applied to fungal keratitis, therapeutic efficacy will improve with longer treatment duration.

Evaluation of the effect of corneal collagen cross-linking for keratoconus on the ocular higher-order aberrations.

BackgroundCorneal collagen cross-linking (CXL) is the only treatment currently available to arrest the progression of keratoconus. The procedure consists of photopolymerization of stromal collagen fibers induced by combined action of a photosensitizing substance (riboflavin or vitamin B2) and ultraviolet-A light.PurposeTo determine changes in the ocular higher-order aberrations (HOAs) after CXL and its correlation with changes in visual acuity.DesignProspective interventional study.Subjects and methodsThis study was conducted on 30 eyes of 16 patients with progressive keratoconus documented between 2012 and 2014. Patients were treated with epithelium-off CXL and followed for a minimum of 6 months. The following ocular HOAs were measured and analyzed using I-Tracey Aberrometer: coma, trefoil, spherical aberration, astigmatism, and total HOAs.ResultsThere was statistically significant improvement in uncorrected visual acuity and best-corrected visual acuity between the preoperative and 6-month evaluations (P<0.001). Total HOAs and total coma were statistically significantly reduced at 6 months by 25% and 18%, respectively. Significant improvement was seen in spherical aberration by 8.71% (P<0.001), while no significant change was observed in trefoil and high order astigmatism (P=0.405 and 0.329, respectively). There was a statistically significant change in the average (K) value at the apex between the preoperative values and the 6-month values (P<0.05).ConclusionTotal HOAs, total coma, and spherical aberrations decreased after CXL. Coma has a direct relationship with the improvement of visual function.

Corneal collagen cross-linking in paediatric patients affected by keratoconus

Background/aimsTo evaluate the effectiveness of corneal collagen cross-linking (CXL) in paediatric patients.MethodsFifty-two eyes of 43 paediatric patients with progressive keratoconus were enrolled in a prospective cohort study. Corneal CXL was...

Treatment Results of Corneal Collagen Cross-Linking Combined with Riboflavin and 440 Nm Blue Light for Bacterial Corneal Ulcer in Rabbits

ABSTRACTPurpose: To study the treatment effect of corneal collagen cross-linking (CXL) combined with 440 nm blue light and riboflavin on bacterial corneal ulcer using animal experiments.Methods: A total of 21 New Zealand white rabbits that developed Staphylococcus aureus corneal ulcer were randomly divided into three groups. Seven rabbits were used as blank control groups; seven rabbits were treated with CXL combined with riboflavin and 440 nm blue light; and seven rabbits were treated with CXL combined with riboflavin and 370 nm ultraviolet A light. Necrotic tissues or secretions from the ulcer surface, eye secretions, conjunctival hyperemia, hypopyon, corneal infiltration, and pathological changes of the cornea were all observed.Results: The 1st, 3th, and 7th day after CXL treatment, a statistically significant difference was found among the inflammation scores of the three groups. The scores of 440 and 370 groups decreased gradually, significantly lower than that of the control group. Bacterial cultures of 440 and 370 groups turned to be negative while that of the control group remained positive. After 1 day of CXL treatment, pathology pictures of the three groups all showed loss of corneal epithelia with many inflammatory cells in deep stroma. After 7 days of CXL treatment, abscess formed in almost all corneal area in the control group, while in 440 and 370 groups, multilayer healing of corneal epithelia, neovascularization, and many inflammatory cells within ulcers and proliferation of a small amount of fibroblast were seen.Conclusions: CXL combined with riboflavin and 440 nm blue light is effective in treating S. aureus corneal ulcer.

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

ABSTRACT 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.

Cost-Effectiveness Analysis of Corneal Collagen Crosslinking for Progressive Keratoconus

To evaluate the cost effectiveness of corneal collagen crosslinking (CXL) for progressive keratoconus from the healthcare payer's perspective. A probabilistic Markov-type model using data from published clinical trials and cohort studies. Two identical cohorts, each comprising 1000 virtual patients with progressive bilateral keratoconus, were modeled; one cohort underwent CXL and the other cohort received no intervention. Both cohorts were modeled and evaluated annually over a lifetime. Quality-adjusted life years (QALYs), total cost, disease progression, and the probability of corneal transplantation, graft failure, or both were calculated based on data from published trials and cohort studies. These outcomes were compared between the 2 cohorts. In our base scenario, the stabilizing effect of CXL was assumed to be 10 years; however, longer durations also were analyzed. One-way sensitivity analyses were performed to test the robustness of the outcomes. Incremental cost-effectiveness ratio (ICER), defined as euros per QALY. Assuming a 10-year effect of CXL, the ICER was €54 384/QALY ($59 822/QALY). When we adjusted the effect of CXL to a lifelong stabilizing effect, the ICER decreased to €10 149/QALY ($11 163/QALY). Other sensitivity and scenario analyses that had a relevant impact on ICER included the discount rate, visual acuity before CXL, and healthcare costs. Corneal collagen crosslinking for progressive keratoconus is cost effective at a willingness-to-pay threshold of 3 times the current gross domestic product (GDP) per capita. Moreover, a longer stabilizing effect of CXL increases cost effectiveness. If CXL had a stabilizing effect on keratoconus of 15 years or longer, then the ICER would be less than the 1× GDP per capita threshold and thus very cost effective.

Why Non-contact Tonometry Tests Cannot Evaluate the Effects of Corneal Collagen Cross-linking.

To assess the feasibility of characterizing and following up the mechanical behavior of the corneal tissue after corneal cross-linking (CXL) by using a combined mechanical (in vivo indentation and in vitro uniaxial tensile tests) and morphological (immunohisto-chemistry) experimental protocol. CXL (3 mW/cm2; 370 nm) for 20 minutes (total dose 3.6 J/cm2) was performed on 12 New Zealand rabbits. The mechanical behavior of the cornea was characterized in small and large strain regimens using an in vivo indentation test with a laboratory device and an in vitro uniaxial tensile test, respectively. These tests and corneal immunohistochemistry were performed before (PreCXL) and on the 7th (PostCXL-7d) and 56th days (PostCXL-56d) after CXL. The intraocular pressure and corneal thickness were measured before each test. For the indentation tests, significant differences were found between PreCXL and PostCXL-7d and between PostCXL-7d and PostCXL-56d, but not between PreCXL and PostCXL-56d. On average, for the small strain regimen, PostCXL-7d corneas showed the most compliant behavior, with progressive recovery of the corneal stiffness over time. For the large strain regimen, significant differences in the maximum tangent modulus between PreCXL and PostCXL-7d and between PreCXL and PostCXL-56d were observed for the uniaxial tensile tests, with no significant differences between PostCXL-7d and PostCXL-56d. Immunohistochemistry showed a lack of cells in the anterior stroma at PostCXL-7d, but at PostCXL-56d the cell density and morphology were comparable to PreCXL. Indentation tests cannot characterize the changes in the corneal collagen scaffold caused by the CXL, but the uniaxial test can. However, indentation tests can assess the recovery of keratocyte density after CXL. [J Refract Surg. 2017;33(3):184-192.].

Thinner Corneas Appear to Have More Striking Effects of Corneal Collagen Crosslinking in Patients with Progressive Keratoconus.

Purpose. To analyze the outcomes and difference after UVA/riboflavin corneal collagen crosslinking (CXL) in four different corneal thickness groups of patients with progressive keratoconus. Methods. Retrospective study. Eyes with progressive keratoconus after CXL were divided into 4 subgroups as follows: group 1, thinnest corneal thickness (TCT) ≤ 400 µm; group 2, 400 µm < TCT ≤ 450 µm; group 3, 450 µm < TCT ≤ 500 µm; group 4, TCT ≥ 500 µm. Baseline, 6-month, and 12-month visual acuity, corneal topography, TCT, and endothelial cell density were evaluated. Results. The analysis included 123 eyes of 101 patients. At 6 and 12 months after CXL, there was a mean improvement about visual acuity and keratometry values in all patients. There was a reduction in the change of maximum keratometry (Kmax) with the increase of TCT. After 1 year of treatment, it was 3.04 ± 0.75 D in group 1, 2.38 ± 0.51 D in group 2, 1.57 ± 0.35 D in group 3, and 0.31 ± 0.20 D in group 4. Conclusion. CXL is successful in halting the progression of keratoconus and there was a negative linear correlation between TCT and Kmax. Advanced cases of progressive keratoconus seemed to obtain more benefits from the flatting effects of CXL.

Corneal collagen cross-linking and liposomal amphotericin B combination therapy for fungal keratitis in rabbits.

To observe the therapeutic effect of corneal collagen cross-linking (CXL) in combination with liposomal amphotericin B in fungal corneal ulcers. New Zealand rabbits were induced fungal corneal ulcers by scratching and randomly divided into 3 groups, i.e. control, treated with CXL, and combined therapy of CXL with 0.25% liposomal amphotericin B (n=5 each). The corneal lesions were documented with slit-lamp and confocal microscopy on 3, 7, 14, 21 and 28d after treatment. The corneas were examined with transmission electron microscopy (TEM) at 4wk. A rabbit corneal ulcer model of Fusarium was successfully established. The corneal epithelium defect areas in the two treatment groups were smaller than that in the control group on 3, 7, 14 and 21d (P<0.05). The corneal epithelium defect areas of the combined group was smaller than that of the CXL group (P<0.05) on 7 and 14d, but there were no statistical differences on 3, 21 and 28d. The corneal epithelium defects of the two treatment groups have been healed by day 21. The corneal epithelium defects of the control group were healed on 28d. The diameters of the corneal collagen fiber bundles (42.960±7.383 nm in the CXL group and 37.040±4.160 nm in the combined group) were thicker than that of the control group (24.900±1.868 nm), but there was no difference between the two treatment groups. Some corneal collagen fiber bundles were distorted and with irregular arrangement, a large number of fibroblasts could be seen among them but no inflammatory cells in both treatment groups. CXL combined with liposomal amphotericin B have beneficial effects on fungal corneal ulcers. The combined therapy could alleviate corneal inflammattions, accelerate corneal repair, and shorten the course of disease.

Cross-linking in children with keratoconus: a systematic review and meta-analysis.

Keratoconus can behave more aggressively in pediatric than in adult patients. We systematically reviewed the literature to determine the effectiveness of corneal collagen cross-linking (CXL) in children. For this study, MEDLINE® and Cochrane databases were searched for all studies examining the effects of standard, trans-epithelial or accelerated CXL protocols in patients age 18years or younger. Primary outcomes were; uncorrected visual acuity (UCVA) and maximum keratometry (Kmax) and secondary outcomes were; best-corrected visual acuity (BCVA), mean refractive spherical equivalent (MRSE), central corneal thickness (CCT) and endothelial cell density (ECD). Standardized mean differences (SMD) and 95% confidence intervals were calculated, comparing baseline values with those at 6, 12 and 24months. A total of 13 papers, published between May 2011 and December 2014 examining 490 eyes of 401 patients with a mean age of 15.25 (±1.5) years, were included in the qualitative analysis in this review. Nine papers were included in the meta-analysis, showing significant improvement in UCVA and BCVA and stable Kmax at 12months, and stable UCVA, improved BCVA and improved Kmax at 24months in the standard protocol group UCVA, BCVA and KMax were stable at 12months in the trans-epithelial group. Mean refractive spherical equivalent (MRSE), CCT and ECD remained stable in both groups. In conclusion it was found that standard CXL may be effective in halting progression of keratoconus in pediatric patients at 1year. However, larger, more long-term studies are required to ascertain its effectiveness.

Higher-order aberrations 1 year after corneal collagen crosslinking for keratoconus and their independent effect on visual acuity

To evaluate the effect of corneal collagen crosslinking (CXL) in progressive keratoconus patients on higher-order aberrations (HOAs) and the effect of change in HOAs on visual acuity between baseline and 1year after CXL. Tertiary academic referral center, Utrecht, the Netherlands. Prospective cohort study. This study included consecutive keratoconus patients who were treated with epithelium-off CXL and followed for a minimum of 1year. The following corneal HOAs were measured with Scheimpflug tomography (Pentacam HR type 70900): coma, trefoil, spherical aberration, and total corneal HOAs. A 2-tailed paired-samples t test was used to compare baseline and postoperative aberrations. Multivariable linear regression was applied to assess the independent effects of HOA subtypes on changes in uncorrected (UDVA) and corrected (CDVA) distance visual acuity. Overall, the degree of corneal HOAs in the patient cohort (N=187) was relatively unchanged after CXL, with a mean change of -1.34% (P=.272). Horizontal coma contributed most to the total amount of HOAs but was virtually unchanged on average. The HOA subtype of spherical aberrations decreased significantly (-15.68%) (P<.001). There was no effect of the change in HOAs on the change in CDVA; however, there was a significant effect of the change in horizontal coma on the change in UDVA (P=.003; B -0.475). Corneal HOAs in general were relatively unchanged from baseline to 1year after CXL in eyes with progressive keratoconus. A change in horizontal coma had a strong and independent effect on UDVA. None of the authors has a financial or proprietary interest in any material or method mentioned.

Effects of Corneal Collagen Crosslinking on Confocal Microscopic Findings and Tear Indices in Patients with Progressive Keratoconus.

Background:To evaluate any change in tear indices and confocal microscopic findings after corneal collagen crosslinking (CXL) in patients with progressive keratoconus.Methods:Thirty-two consecutive eyes from 23 patients having progressive keratoconus were enrolled in this prospective, interventional cohort study. The standard crosslinking surgery was performed for all patients. Visual, refractive, and topographic evaluations were done before and at 6 months after surgery. Tear function tests and confocal microscopic examination were performed before and at 1 month and 6 months after the procedure.Results:There was no significant change in Schirmer-1 test results and tear osmolarity at 1 month and 6 months after CXL. Using confocal microscopy, all eyes showed reduced or absent subepithelial nerve plexus. Differences in basal epithelial cell density, epithelial mean cell area, and keratocyte density in anterior and middle stroma and endothelial cell pleomorphism were all significant at 1 month and 6 months after CXL (P < 0.05). No significant change was noted in endothelial cell count and their polymegathism at 6 months follow-up. Significant improvement was noted in uncorrected visual acuity, best corrected visual acuity, flattest corneal meridian (K2), and maximum keratometry in Pentacam (Kmax) after 6 months of the procedure.Conclusions:While CXL would have no effect on tear indices and endothelial cell count, it can cause a significant reduction in subepithelial nerve plexus and significant alterations in epithelial cell density in the anterior and middle stroma.

Microbiologic, Pharmacokinetic, and Clinical Effects of Corneal Collagen Cross-Linking on Experimentally Induced Pseudomonas Keratitis in Rabbits.

To determine the effects of corneal collagen cross-linking (CXL) on the penetration of topical 0.5% moxifloxacin, on the number of colony-forming units (CFUs) in the cornea, and on the clinical course in a rabbit eye model of experimentally induced Pseudomonas aeruginosa keratitis. In this prospective animal study, experimental Pseudomonas corneal ulcers were induced in 56 corneas of 28 albino New Zealand rabbits. The corneas were randomly divided into the following 4 groups: the control group (14 eyes), the MOX group (moxifloxacin) (14 eyes), the MOX + CXL group (14 eyes), and the CXL group (14 eyes). On day 4 of the experiment, the eyes in the control group were enucleated and CFU counting was performed. On day 10 of the experiment, all eyes were enucleated and CFU counting was performed. In the MOX and MOX + CXL groups, the moxifloxacin level in the cornea, aqueous humor, iris, plasma, and serum was measured by reverse-phase high-performance liquid chromatography. The difference in the corneal CFU count between the MOX group and the MOX + CXL group was not significant (P = 0.317). Clinical improvement was greatest in the MOX + CXL group (P < 0.001). The mean corneal moxifloxacin level was 0.391 ± 0.09 μg·mg in the MOX group versus 0.291 ± 0.09 μg·mg in the MOX + CXL group; as such, CXL did not have a significant effect on antibiotic penetrance (P = 0.386). Clinical improvement was greatest in the MOX + CXL group. The synergistic effect of CXL on corneal ulcer treatment is not through antibiotic penetrance.

Early effects of corneal collagen cross-linking by iontophoresis in ex vivo human corneas.

The purpose was to investigate the early modifications induced by collagen cross-linking by iontophoresis of riboflavin (ionto-CXL) in ex vivo human corneas by evaluating different protocols of UVA irradiation. In this experimental study 46 ex vivo human corneas obtained from the Eye Bank of Mestre (Italy) were divided in different groups: six were utilized as control (CTL); eight were treated with ionto-CXL at 3mW/cm(2) power for 30min (I-3); eight were treated with ionto-CXL at 10mW/cm(2) for 9min (I-10); eight were treated with iontophoretic delivery of riboflavin only (I-0); eight were treated with the standard CXL at 3mW/cm(2) for 30min (S-3); and eight were treated with CXL at 10mW/cm(2) for 9min (S-10). All samples were evaluated by haematoxylin-eosin staining and immunohistochemical analysis using different markers (Connexin 43, CD34, Collagen I, TUNEL assay). Western blot analysis, utilizing Bax and Ki67 primary antibodies, for detection of keratocyte apoptosis and proliferation, respectively, was also performed. No endothelial damage was evidenced in the treated groups. In I-10 corneas the epithelial layers were not always well-preserved. Anterior stroma showed an uneven distribution and numerical reduction of keratocytes as well as increased apoptosis; a reduced subepithelial interweaving of collagen I fibers was observed. In S-3 and S-10 the changes induced by treatments were similar to I-10. I-3 and I-0 showed no significant changes with respect to the control group. In the ionto-CXL at 10mW/cm(2) group occurred the main morphological and biomolecular changes. This experimental study suggests that iontophoresis can be considered a non-invasive potential delivery tool for riboflavin penetration in corneal stroma during CXL.