CXL Procedure Research Articles

Effects of Collagen Cross-Linking on the Corneal Optical and Topographic Characteristics in Progressive Keratoconus

Aim: To determine the significant changes which occur in the corneal parameters, including pachymetry, after corneal collagen cross linking (CXL) by means of Scheimpflug imaging. Methods: Standard CXL procedure was done for 40 eyes diagnosed as progressive keratoconus (KCN). The following parameters were monitored pre, six months and 1 year post operatively: uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), refractive spherical equivalent (S.E), keratometry1 (K1) and keratometry2 (K2), apex and thinnest point pachymetries, thinnest point coordinates (X,Y) minimum (Min.), maximum (Max.), average (Avg.) pachymetric progression indices, Max. Anterior and posterior elevations. Pentacam (Oculus, Wetzlar, Germany) imaging was used to monitor the corneal parameters of the study. Paired sample T test was used for statistical analysis. Results: Following parameters of the study did not show significant changes after CXL: UCVA: (P= 0.65), BCVA: (P= 0.076), S.E: (P= 0.343), Thinnest point X coordinate: (P=0.545), Thinnest point Y coordinate: (P= 0.144), Max. Anterior elevation (P= 0.508) and the following parameters showed significant changes: K1: (P= 0.001), K2: (P= 0.015), Apex pachymerty: (P <0.001), Thinnest point pachymetry: (P <0.001), Max. Post. Elevation: (P= 0.001) and all (Max., Min., Avg.) pachymetric progression indices: (P <0.001 for all 3). The most significant changes occurred in pachymetric progression indices. Conclusion: We could show six months to 1 year after CXL procedure, the corneal thickness is lower than its baseline and keratometric changes have been settled during this period. UCVA, BCVA have not been changed significantly and the pachymetric progression indices are the most significant parameters to have changes, when evaluating them by Pentacam. Validity of Scheimpflug imaging of the corneas after CXL should be determined in further studies.

Usage of polarization-sensitive optical coherence tomography for investigation of collagen cross-linking.

To investigate morphological alternation in corneal stroma induced by collagen cross-linking (CXL) treatment, polarization-sensitive optical coherence tomography (PS-OCT) capable of providing scattering, phase retardation, and degree of polarization uniformity (DOPU) images were employed on fresh bovine cornea. Significant corneal thickness reduction was observed after the CXL procedure, and its variation was quantitatively analyzed. From the scattering contrast, a hyperscattering region was observed in the anterior of the cornea immediately after the CXL procedure and its range increased with time. Within the scattering region, a slow increase was observed in the phase retardation image, and a discriminable characteristic was found in the DOPU image. A global threshold value was empirically determined from the averaged DOPU depth profile in order to locate the effective cross-linking depth. In addition to the standard protocol, an accelerated CXL procedure shortening the treatment time with higher intensity of ultraviolet-A (UV-)A power was also performed. From the measurement results after the two different CXL protocols, different cross-linking aspects were found and their difference was discussed in terms of the effectiveness of cross-linking. Based on this study, we believe that PS-OCT could be a promising optical imaging modality to evaluate the progression and effectiveness of the riboflavin/UV-A induced corneal collagen cross-linking.

Intraocular Pressure Measurements Referring to the Corneal Thickness in Keratoconic Eyes After Corneal Crosslinking with Riboflavin and Ultraviolet A.

Aim:To determine the possible relation between intraocular pressure (IOP), central corneal thickness (CCT) and corneal resistance (CR) in kerotoconic eyes before, 3,6 and 12 months after collagen crosslinking procedure (CXL) with aim to find out does the thicker cornea means already more resistance cornea followed with higher IOP.Methods:Thirty eyes (30 patients) with central keratoconus (KC)were evaluated in retrospective cross sectional study. The corneal biomechanical parameters were taken with Wave Light Allegro Oculyzer produced by Alcon before the CXL, 3, 6 and 12 months after the procedure. IOP were checked by Goldmann applanation tonometry (GAT) before, 3, 6 and 12 months after CXL.Results:The value of IOP before the CXL was 12,0 mmHg (10,62-15,25 mmHg), 3 months later 13,5 mmHg (11,0-16,0 mmHg), 6 months 14,0 mmHg (11,0-16,0 mmHg) and 12 months later 15,0 mmHg (10,37-17,25 mmHg) and was statistically significant higher (p=0,015) comparing to the value of IOP 3 months after the CXL, IOP 12 months after CXL procedure was statistically significant higher comparing to preoperative values (p=0,010). There were no statistically significant difference between the values 3 and 6 months after CXL. The CCT before the CXL procedure was 449 (433-505,75 microns), 3 months after CXL was 420 (383-473microns, p < 0,005), 6 months later 437 (401,25-480,25, p=0,001), 12 months after CXL 437 (401-503 microns, p=0,001). However there is statistically significant difference in CCT 12 months after CXL 437 (401-503microns p=0,032) and the value of CCT 3 months later the procedure (p=0,004) and the CCT 12 months after CXL and the value of CXL 6 months after CXL (p=0,036). The value of CCT did not show any statistically significant difference 3 and 6 months postoperatively.Conclusion:After riboflavin-UVA CXL in eyes with KC there was significant decrease in central corneal thickness 3 and 6 months after the procedure and the thickness is almost the same 12 months later. However IOP is low before CXL, raising up 3 and 6 months after CXL but significant increase is seen 12 months later. It means the regular measurement of IOP could be the serious and confident indicator of increasing of corneal resistance which is the main goal of CXL treatment.

Assessment of the tomographic values in keratoconic eyes after collagen crosslinking procedure.

Goal:This study aimed to investigate the differences in values of K1 and K2 readings, the central corneal thickness (PAH) before the collagen crosslinking procedure (CXL) and 3, 6, 12 months later.Methods:64 eyes were evaluated in retrospective cross sectional study. The corneal biomechanical parameters were taken with WaveLight Allegro Oculyzer produced by Alcon before the CXL, 3,6, 12 months after the procedure. The curvature of K1 reading and K2 reading were taken and the central corneal thickness were considered due to the time after CXL.Results:The value of K1 reading before the treatment was 48.8 diopters (D) (46.65-50.50) and was statistically significant lower comparing to the value of K1 3 months after the collagen CXL procedure 46.30 D (43.57-49.45) (p=0.0006), K1 reading one year post collagen CXL procedure was 47.20 D (44.35-50.07) (p=0.002). The value of K2 reading before the collagen CXL procedure was 52.65 D (47.55-54.72), 3 months after the procedure was 51.4 (45.05-54.0), 6 months later 48.55 D (47.20-50.62), 12 months later 51.30 D (47.22-54.77). There is statistically significant lower value of K2 reading 6 months after the treatment comparing to the values 3 months postoperatively (p=0.014). However there is significantly lower values of K2 reading 12 months postoperatively comparing to preoperative period (p=0.006). The value of central corneal thickness preoperative was 431.0 microns (398.0-446.25), 3 months after collagen CXL procedure was 373.50 microns (363.25-430.75), 6 months later 435.0 microns (360.0-464.75), 12 months after the CXL procedure was 429.50 microns (357.75-496.25). There is statistically significant lower values of central corneal thickness 3 months after collagen CXL treatment comparing to the central corneal thickness preoperative (p<0.005). There is statistically significant lower values of pachymetry 12 months after the CXL procedure comparing to the values 6 months later (p=0.036) and those preoperativelly (p=0.032). There is no statistically significant difference in the values of central corneal thickness in the period from 3 and 6 months postoperatively.Conclusion:After riboflavin-UVA CXL in eyes with keratokonus there was significant decrease in central corneal thickness 3 and 6 months after the procedure and the thickness is almost the same 12 months. However, K2 (Kmax) reading is significantly changed 3 and 6 months later and is followed by changing of K1 reading.

Lens Densitometry after Corneal Cross-linking in Patients with Keratoconus Using a Scheimpflug Camera.

Purpose:To evaluate changes in crystalline lens densitometry following corneal cross-linking (CXL) in keratoconic patients.Methods:In a quasi-experimental study, three-dimensional lens densitometry was performed using the Pentacam Scheimpflug camera (Oculus Optikgerate GmbH, Wetzlar, Germany) at baseline and six months after CXL. Densitometry was performed in a fixed area of 2 inch × 1 inch of the anterior capsule and anterior lens cortex. The subject group included patients with progressive keratoconus who underwent CXL (n = 40) and the control group was comprised of aged-matched patients with non-progressive keratoconus (n = 36).Results:Mean age of the case and control groups was 25.8 ± 4.0 and 25.0 ± 4.1 years, respectively (P = 0.392). Mean lens density in the CXL group was 6.68% ± 0.58% at baseline and 6.77% ± 0.53% at the last visit (P = 0.352). Corresponding figures in the control group were 6.53% ± 0.27% and 6.39% ± 0.31%, respectively (P = 0.213). There was no significant difference between the study groups at baseline or six months later (P = 0.96).Conclusion:In this short term study with six months’ follow-up, we observed no significant impact on lens density following exposure of the crystalline lens to ultraviolet A and riboflavin free radicals in the CXL procedure.

Impact of corneal cross-linking on topical drug penetration in humans.

To analyse the influence of corneal cross-linking (CXL) with ultraviolet-A (UV-A) and riboflavin on drug permeability in human subjects. Keratoconus patients (n = 23; mean age 26.9 ± 5.8 years) undergoing a standard CXL procedure with UV-A (5.4 J/cm(2) , 30 min) and riboflavin in one eye were included in the study. The pupillary diameter, measured before and every 3 min for 30 min after the topical application of one drop of 2% pilocarpine, was used as an indirect measure of the corneal permeability. The pupillary diameter was measured with an infrared pupillometer device before (baseline) and 4 months after CXL. Prior to pilocarpine application, no significant difference in the pupillary diameter was detected before CXL and 4 months later. The mean decrease in the pupillary diameter after the application of pilocarpine was similar at baseline and the 4-month follow-up visit: mean decreases of 3.9 and 3.7 mm were observed 30 min after pilocarpine application, respectively (p > 0.05). No significant influence of CXL on the corneal penetration of topically applied pilocarpine was observed in this clinical study.

Advances in the technology of corneal cross-linking for keratoconus.

Corneal cross-linking (CXL) with ultraviolet-A (UVA) and riboflavin was introduced over 15 years ago and has been widely adopted as a treatment for keratoconus. Several studies have demonstrated the safety and efficacy of the procedure performed according to a standard protocol. Recent scientific and technological advances have highlighted the opportunity for optimization of the CXL procedure through modifications to this protocol. Advances in the technology of CXL include new riboflavin formulations, higher irradiance UVA sources, and programmable UVA illumination patterns. Several laboratory and clinical studies demonstrate that these modifications may provide equivalent treatment effect in shorter total treatment times. Additionally, although the original purpose of CXL was to stabilize the cornea and prevent further visual loss in keratoconus, patient-specific computational modeling and customized CXL with programmable UVA treatment patterns demonstrate the potential for CXL to be used as a means of improving corneal topography to maximize visual rehabilitation in patients with keratoconus. This review aims to provide an overview of these advances in CXL technology designed to optimize the efficiency or efficacy of the clinical CXL procedure.

Additive Effect of Repeated Corneal Collagen Cross-linking in Keratoconus

To report the long-term clinical outcome in a patient diagnosed as having bilateral progressive keratoconus who received a single corneal collagen cross-linking (CXL) treatment in the right eye and repeated CXL in the left eye. Observational case report. Topographical changes were assessed by high-resolution Scheimpflug imaging. The right eye underwent a standard epithelium-off CXL procedure in February 2008, followed by the left eye 4 weeks later. In 2012, the left eye was treated with CXL for a second time. Irradiation was performed in all cases at a fluence of 5.4 J/cm². Energy settings were 30 minutes @ 3 mW/cm² for the CXL procedures performed in 2008, and 10 minutes @ 9 mW/cm² for the second CXL procedure of the left eye that was performed in 2012. The right eye that underwent a single CXL procedure showed a flattening of keratometry values between 2008 and 2012, followed by stabilization. The left eye showed a similar flattening effect between 2008 and 2012, followed by another flattening effect after the second CXL procedure and accompanied by a distinct increase in corrected distance visual acuity. Following repeated CXL, the corneal stroma and endothelium remained inconspicuous, and postoperative haze and visibility of the stromal demarcation line was similar to what is usually observed after a single CXL procedure. Whether the additive flattening effect of the anterior surface observed in this single case goes along with an additive increase in biomechanical stiffness remains to be seen.

The Effect of Collagen Cross-Linking Procedure on the Material of Intracorneal Ring Segments

Purpose: To assess the potential impact of corneal crosslinking treatment (365 nm ultraviolet (UV)A irradiation with riboflavin) on the material properties of Intracorneal Rings Segments (ICRS).Materials and methods: Material properties were studied using FT-IR spectroscopy and UV-Vis spectroscopy. Rings were examined: (1) after installation of riboflavin solution, (2) after irradiation with UV-A light and (3) after instillation of riboflavin solution followed by instillation and coeval irradiation. The experiments followed the standard corneal cross-linking (CXL) protocol of corneal crosslinking treatment.Results: After instillation of riboflavin solution, a permanent intense yellow staining of the samples was observed. UV-Vis spectroscopy confirmed that a certain amount of riboflavin solution was absorbed into the samples after CXL procedure. FT-IR spectroscopic analysis showed alterations in the spectra of ICRS mainly at the 2800–3200 cm−1 spectral region [modification in band intensities of CH2 (2925 cm−1) and CH3 (2950 cm−1)].Conclusions: Our results suggest crosslinking reaction in ICRS material. This should be taken into consideration prior to any CXL treatment of post ICRS-implanted cornea.

Can the Effect of Transepithelial Corneal Collagen Cross-linking Be Improved by Increasing the Duration of Topical Riboflavin Application? An In Vivo Confocal Microscopy Study

To evaluate the effect of transepithelial corneal collagen cross-linking (CXL) with prolonged riboflavin application by in vivo confocal microscopy and to compare this effect with that of standard CXL with complete epithelial debridement. In eyes with progressive keratoconus, CXL procedure was performed with standard technique and transepithelial technique after prolonged riboflavin drop application for 2 hr. Patients were evaluated with in vivo confocal microscopic examination preoperatively and at postoperative months 1 and 6. The depth of CXL effect was similar in both groups (i.e., 380.86 ± 103.23 μm in standard CXL group and 342.2 ± 68.6 μm in transepithelial CXL group) (P=0.4). The endothelial cell counts and morphological parameters (i.e., pleomorphism and polymegathism) were not significantly affected in both groups (P>0.05 for all). In the standard CXL group, in vivo confocal microscopy revealed anterior stromal acellular hyperreflective honeycomb edema with posteriorly gradually decreasing reflectivity and increasing number of keratocytes and some sheets of longitudinally aligned filamentary deposits. The keratocytes were seen to repopulate in the posterior-to-anterior direction. In transepithelial CXL group, although the depth of CXL effect was similar, less pronounced keratocyte damage, extracellular matrix hyperreflectivity, and sheets of filamentary deposits at the posterior stroma was observed. Transepithelial CXL with prolonged peroperative riboflavin application can achieve similar depth of effect in the stroma with less pronounced confocal microscopic changes as compared with the standard CXL with complete epithelial debridement.

Customized epithelial debridement for thin ectatic corneas undergoing corneal cross-linking: epithelial island cross-linking technique.

Thin corneas with a minimum corneal thickness less than 400 μm after epithelial removal represent a contraindication to standard epithelium-off cross-linking (CXL) treatment due to a significant endothelial cell density decrease and potentiality of permanent haze development. Preoperative swelling of the cornea with hypoosmolar riboflavin solutions broadens the spectrum of CXL indications to thin corneas. However the iatrogenic swelling effect might not be durable throughout the CXL procedure increasing the risk of postoperative complications. The transepithelial CXL technique proposed for thin corneas demonstrated poor clinical results and mid- to long-term keratoconus instability. The epithelial island CXL technique with customized pachymetry-guided epithelial debridement was evaluated by means of in vivo laser scanning confocal microscopy, corneal topography, and clinical examination in a 1-year follow-up, in order to assess if it may be considered an alternative surgical option for keratoconic patients with thin corneas undergoing corneal collagen CXL. According to our clinical and in-vivo micro-morphological results the technique results safe, and efficacious in stabilizing progressive keratoconus and may be considered a valid option in the treatment of thin ectatic corneas alone or in combination with hypoosmolar or dextran-free riboflavin solutions.

Confocal Microscopy Analysis of Corneal Changes After Photorefractive Keratectomy Plus Cross-Linking for Keratoconus: 4-Year Follow-up

To analyze corneal confocal microscopy changes after combined photorefractive keratectomy (PRK) plus the cross linking (CXL) procedure. Prospective interventional case series. At the Department of Basic Medical Sciences, Neuroscience, and Sense Organs of the University of Bari, Bari, Italy, 17 eyes of 17 patients with progressive keratoconus underwent confocal microscopy examination before and after 1, 3, 6, 12, 18, and 48 months following PRK plus the CXL procedure. The main outcome measures were mean superficial epithelial cell density; mean basal epithelial cell density; mean anterior, mid and posterior keratocyte density; qualitative analysis of stromal backscatter; sub-basal and stromal nerve density parameters; and mean endothelial cell density. During the 4-year follow-up, the mean superficial epithelial cell density, mean basal epithelial cell density and mean endothelial cell density remained unchanged (P > 0.05). The anterior mid-stromal keratocyte density showed a significant decrease (P < 0.05) as compared with preoperative values, and the posterior stromal keratocyte density showed a significant increase at 1 and 3 months of follow-up. Sub-basal and stromal nerve density parameters were significantly decreased until postoperative month 6 (P < 0.05 at 1, 3, and 6 months) and then tended to increase up to preoperative values by the 18th postoperative month. Corneal changes after the PRK plus CXL procedures seem to be pronounced and long lasting as far as keratocyte density of the anterior and mid stroma is concerned. Sub-basal nerve densities tend to reach preoperative values 6 months after surgery.

Response to Vinciguerra et al

Sir, We thank Vinciguerra et al1 for their interest and valuable comments on our article.2 The rationale of our study was to determine the preoperative patient characteristics affecting visual and topographic outcomes of corneal collagen crosslinking (CXL) for progressive keratoconus. We found that patients with a worse preoperative corrected distance visual acuity (CDVA, ≤20/40 Snellen equivalent) tend to experience more visual improvement after CXL treatment (P<0.001).2 However, an older age (≥30 years) and a thinner cornea (thinnest pachymetry <450 μm) appear to be positive preoperative predictors for more flattening in maximum keratometry (P=0.024 and P=0.005, respectively).2 Similarly, Vinciguerra et al3 reported that age between 18 and 39 years has positive effect on the outcomes of CXL, and they found a significant association between the thinnest pachymetry and sphere change after CXL treatment. Unlike the studies of Vinciguerra et al3 and Greenstein et al,4 our analysis showed no significant relation between initial maximum keratometry and postoperative improvement in visual acuity and maximum keratometry.2 In our study, cut points were determined as 54 diopters (D) for the maximum keratometry and 450 μm for the thinnest pachymetry in accordance with the current literature and median values. A significant result could be found by shifting cut point to 58.5 D for maximum K, whereas inappropriate and unbalanced number of subjects between subgroups did not allow using this cut point in our study. We agree with the comments of Vinciguerra et al1 that intraoperative corneal thickness measurement is crucial and swelling riboflavin solutions should be used when the intraoperative minimum corneal thickness is <400 μm to prevent complications. However, in our study we excluded the eyes, which received swelling riboflavin solution during the CXL procedure.2 In conclusion, our results suggest that age, preoperative CDVA, and thinnest pachymetry seem to affect the outcomes of CXL treatment. Moreover, Vinciguerra et al and several studies concluded that preoperative maximum keratometry has an effect on the clinical improvement after CXL treatment.3, 4, 5, 6 However, the predictive threshold values for each preoperative factor remain to be investigated.

Evaluating In Vivo Delivery of Riboflavin With Coulomb-Controlled Iontophoresis for Corneal Collagen Cross-Linking: A Pilot Study

To evaluate the efficacy of coulomb-controlled iontophoresis (CCI) for delivery of riboflavin prior to corneal collagen cross-linking (CXL). The eyes of 20 8-week-old Lewis rats, subject to epithelium-ON (epi-ON, n = 20 eyes) or epithelium-OFF (epi-OFF, n = 20 eyes) conditions, were used to evaluate the in vivo delivery of two riboflavin solutions: 0.1% riboflavin-20% dextran T500 solution (riboflavin-dextran) and 0.1% riboflavin 5'-phosphate (riboflavin-phosphate). After systemic intramuscular anesthesia, 0.25 mL of the photosensitizing agent was delivered by either instillation or CCI (2.11 mA/cm(2) for 4 or 10 minutes) into either epithelial condition. The CCI probe on the eye without current served as control. Confocal microscopy of flat-mounted corneas was used to analyze intracorneal penetration and fluorometry was used to quantify riboflavin in the aqueous within 30 minutes of treatment. Instillation and CCI allowed for uniform delivery of riboflavin-dextran throughout the stroma after epithelial debridement. Transepithelial delivery of riboflavin-dextran was not efficacious. Riboflavin-phosphate was successfully delivered in both epithelium conditions. Complete saturation of the cornea was achieved using CCI after removing the epithelium, the epi-ON case allowed for limited diffusion. Increasing the time from 4 to 10 minutes greatly increased the amount of riboflavin detected in the cornea and aqueous humor. Coulomb-controlled iontophoresis is an effective technique for transepithelial delivery of riboflavin-phosphate into the cornea. This drug delivery method would allow clinicians to significantly shorten the time required for the CXL procedure, with or without epithelial debridement. Whether efficient crosslinking can be achieved through an intact epithelium remains to be demonstrated.

Comparison of clinical results of two pharmaceutical products of riboflavin in corneal collagen cross-linking for keratoconus

BackgroundTo compare the 6-month results of two formulations of Riboflavin provided by Sina Darou, Iran, and Uznach, Switzerland, in corneal collagen cross-linking (CXL) for keratoconus patients.FindingsConsidering the results of the previous study about the similarity of the formulations and the active ingredients of the two types of Riboflavin, they were used in the CXL procedure of 60 keratoconic eyes (30 eyes in each group). After 6 months, the mean improvement of UCVA (0.239), BCVA (0.707), and MRSE (0.513) did not differ significantly between the two groups. The mean decrease in max- K (0.731), mean- K (0.264), central corneal thickness (0.759), and Q-value (0.669) did not show any significant difference between the two groups. The two groups had no significant difference in endothelial cell count decrease (0.229). The Sina Darou formulation decreased corneal hysteresis more than the Swiss formulation (P = 0.057) but there were no significant differences in the mean decrease of corneal resistance factor between the two groups (P = 0.117).ConclusionsBased on the early results, the results of visual acuity, refraction, and corneal topography using Sina Darou and Uznach formulations of Riboflavin showed that both were effective in CXL. However, considering the relatively significant difference in corneal hysteresis changes between the two groups, this study will continue to report the long-term results.

Corneal stroma demarcation line after standard and high-intensity collagen crosslinking determined with anterior segment optical coherence tomography

To use anterior segment optical coherence tomography (AS-OCT) to compare corneal stroma demarcation line depth after corneal collagen crosslinking (CXL) with 2 treatment protocols. Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. Prospective comparative interventional case series. Corneal collagen crosslinking was performed in all eyes using the same ultraviolet-A (UVA) irradiation device (CCL-365). Eyes were treated for 30 minutes with 3 mW/cm(2) according to the standard Dresden protocol (Group 1) or for 10 minutes with 9 mW/cm(2) of UVA irradiation intensity (Group 2). One month postoperatively, 2 independent observers measured the corneal stroma demarcation line using AS-OCT. Sixteen patients (21 eyes) were enrolled. Group 1 comprised 7 patients (9 eyes) and Group 2, 9 patients (12 eyes). The mean corneal stroma demarcation line depth was 350.78 μm ± 49.34 (SD) (range 256.5 to 410 μm) in Group 1 and 288.46 ± 42.37 μm (range 238.5 to 353.5 μm) in Group 2; the corneal stroma demarcation line was statistically significantly deeper in Group 1 than in Group 2 (P=.0058, t test for unpaired data). The corneal stroma demarcation line was significantly deeper after a 30-minute CXL treatment than after a 10-minute CXL procedure with high-intensity UVA irradiation.

The Effect of Corneal Epithelium on Corneal Curvature in Patients with Keratoconus

Objective: To investigate the effects of corneal epithelium on corneal curvature in patients with keratoconus. Design: This is a prospective, nonrandomized study. Participants: Fifty-nine eyes of 47 patients diagnosed as keratoconus and for whom corneal collagen crosslinking (CXL) was recruited in this study. Methods: This study is a single-center clinical trial. Pregnancy, lactation, connective tissue disease, corneal thickness below 350 μm, severe dry eyes, or scar of corneal surgery were exclusion criteria. Before and during CXL procedure after removing the corneal epithelium, maximum values of corneal apical curvature, simulated keratometry 1 (Sim-K1), simulated keratometry 2 (Sim-K2), temporal and inferior curvature values, all of which are 1.5 mm from the corneal center, were calculated. These values before and after removal of epithelium were compared statistically. Results: Mean age of patients was 23.30 ± 5.5 (12–38) years. Twenty-eight (59%) were male while 19 (41%) were female. Mean values measured before and after removing the corneal epithelium were: apical curvature; 59.19 ± 7.2 (47.06–82.40) diopter (D) and 61.70 ± 8.8 (49.19–92.66) D (p = 0.001), SimK1; 47.57 ± 4.3 (39.14–64.57) D and 48.23 ± 4.3 (41.89–66.70) D (p = 0.001), SimK2; 52.04 ± 5.3 (43.56–69.34) D and 53.34 ± 5.6 (43.73–70.89) D (p = 0.001), inferior curvature; 53,85 ± 5.2 (43.47–76.56) D and 55.05 ± 5.8 (44.56–81.93) D (p = 0.002), temporal curvature 49.49 ± 5.1 (41.50–71.03) D and 51.53 ± 5.4 (41.58–73.34) D (p = 0.001), respectively. Conclusions: In keratoconus patients during CXL treatment, after removing the corneal epithelium, more steepness is detected in the curvature of the steeper area of the cornea. When evaluating patients with keratoconus, the masking effect of corneal epithelium on values of curvature should be taken into consideration.

Effect of the eyelid speculum on pachymetry during corneal collagen crosslinking in keratoconus patients

To compare central corneal thickness (CCT) with and without using an eyelid speculum during corneal collagen crosslinking (CXL). University Medical Center Utrecht, Utrecht, the Netherlands. Prospective nonrandomized comparative study. Eyes with progressive keratoconus were treated by CXL and consecutively divided into 2 groups. In Group A, an eyelid speculum remained in place throughout the entire CXL procedure. In Group B, the eyelids remained closed during the 30-minute riboflavin instillation. Intraoperative ultrasound pachymetry measurements were performed at different timepoints. The visual acuity, refraction, keratometry, pachymetry, and endothelium were evaluated 6 months after CXL. The main outcome measures were intraoperative CCT measurements and the clinical CXL effect after 6 months. Fifty-two eyes (50 patients) were treated. After riboflavin instillation, a statistically significant difference in CCT reduction was found between the 2 groups (P<.001), with a mean CCT decrease of 62 μm±53 (SD) (13%±11%) in Group A and 11±35 μm (2%±8%) in Group B. No statistically significant between-group differences were found after epithelial removal or ultraviolet-A (UVA) irradiation. Six months after CXL, no statistically significant between-group difference was found in the visual acuity, refraction, keratometry, pachymetry, or endothelium. Avoidance of an eyelid speculum during riboflavin instillation resulted in less CCT reduction during CXL. This finding could increase the chance of attaining the required pachymetry safety margin for applying UVA and thus decrease the chance of premature CXL treatment termination. No author has a financial or proprietary interest in any material or method mentioned.

Anterior Segment Optical Coherence Tomography in Evaluation of Severe Fungal Keratitis Infections Treated by Corneal Crosslinking

Anterior segment optical coherence tomography (OCT) is a relevant diagnostic tool in the evaluation of corneal changes following corneal crosslinking (CXL) treatment in patients infected by a severe fungal corneal infection. Two patients with severe fungal keratitis that was unresponsive to medical treatment were treated with CXL. Corneal melting was present in all cases. Anterior segment OCT showed the preoperative depth and extension of the infiltrate and the modification during the follow-up. Blockage of the melting was achieved in one patient and one patient developed a corneal perforation. Anterior segment OCT allowed control of the evolution of fungal infection and evaluation of the corneal tissue response to the CXL. It is also able to identify the extent and depth of the inflammation. This parameter seems more important than corneal pachymetry to ensure the safety of CXL procedures in infectious keratitis. The different behavior of inflamed tissue with respect to UVA irradiance could be the main point to understand the different postoperative outcome.

Fast-dissolving ocular films of riboflavin acetate conjugate for treatment of keratoconus in UVA-CXL procedure: ex vivo permeation, hemolytic toxicity and apoptosis detection

Background: Attempts to facilitate corneal epithelial penetration of riboflavin (Rb) without de-epithelization, so far, include the use of penetration enhancers, to devitalize corneal epithelium in order to disturb tight epithelial interjunctional complexes and zonulae occludentes. Though such approaches result in sufficient epithelial permeability of Rb to guarantee efficacy of CXL procedure, they lack the evidences of safety. Prodrug with improved lipophilicity targeted toward esterases and amidases has proven to be an effective and promising approach to overcome lipophilic corneal epithelial barrier.Objectives: Fast-dissolving ocular films of newly synthesized and characterized riboflavin lipid conjugate (RbLDC) were developed to overcome corneal epithelial barrier resistance for treatment of keratoconus. The safety concern of the film was assessed by in vitro hemolytic toxicity and in vitro apoptosis detection for its safe clinical use.Results: The optimized film was tough, flexible and dissolved rapidly within 36.86 s in simulated tear fluid, pH 7.4. FE-SEM/EDX showed smooth surfaces of films and evidenced the quantitative elemental similarity, indicating drug homogeneity. The permeation profile of F18 demonstrated 13.28-fold increased permeation of RbLDC relative to Rb solution across intact cornea. Safety was confirmed by 3.74% hemolysis and 10% apoptosis.Conclusion: Safe and efficient RbLDC fast-dissolving ocular films capable of overcoming corneal epithelial barrier resistance to avoid surgical intervention of corneal epithelial debridement were developed.