Assessment of the Predictive Ability of Theranostics for Corneal Cross-linking in Treating Keratoconus: A Randomized Clinical Trial.

PURPOSE: To validate the ability of theranostic imaging biomarkers in assessing corneal cross-linking (CXL) efficacy in flattening the maximum keratometry (Kmax) index. DESIGN: Prospective, randomized, multicenter, masked clinical trial (ClinicalTrails.gov identifier, NCT05457647). PARTICIPANTS: Fifty patients with progressive keratoconus. INTERVENTION: Participants were stratified to undergo epithelium-off (25 eyes) and epithelium-on (25 eyes) CXL protocols using an ultraviolet A (UV-A) medical device with theranostic software. The device controlled UV-A light both for performing CXL and assessing the corneal riboflavin concentration (riboflavin score) and treatment effect (theranostic score). A 0.22% riboflavin formulation was applied onto the cornea for 15 minutes and 20 minutes in epithelium-off and epithelium-on protocols, respectively. All eyes underwent 9 minutes of UV-A irradiance at 10 mW/cm2. MAIN OUTCOME MEASURES: The primary outcome measure was validation of the combined use of theranostic imaging biomarkers through measurement of their accuracy (proportion of correctly classified eyes) and precision (positive predictive value) to classify eyes correctly and predict a Kmax flattening at 1 year after CXL. Other outcome measures included change in Kmax, endothelial cell density, uncorrected and corrected distance visual acuity, manifest spherical equivalent refraction and central corneal thickness 1 year after CXL. RESULTS: Accuracy and precision of the theranostic imaging biomarkers in predicting eyes that had >0.1 diopter (D) of Kmax flattening at 1 year were 91% and 95%, respectively. The Kmax value significantly flattened by a median of -1.3 D (IQR, -2.11 to -0.49 D; P < 0.001); both the uncorrected and corrected distance visual acuity improved by a median of -0.1 logarithm of the minimum angle of resolution (logMAR; IQR, -0.3 to 0.0 logMAR [P < 0.001] and -0.2 to 0.0 logMAR [P < 0.001], respectively). No significant changes in endothelial cell density (P = 0.33) or central corneal thickness (P = 0.07) were noted 1 year after surgery. CONCLUSIONS: The study demonstrated the efficacy of integrating theranostics in a UV-A medical device for the precise and predictive treatment of keratoconus with epithelium-off and epithelium-on CXL protocols. Concentration of riboflavin and its UV-A light mediated photoactivation in the cornea are the primary factors determining CXL efficacy. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Real-time monitoring of riboflavin concentration using different clinically available ophthalmic formulations for epi-off and epi-on corneal cross-linking.

PURPOSE: To assess the feasibility of theranostics to determine the riboflavin concentration in the cornea using clinically available ophthalmic formulations during epithelium-off (epi-off) and transepithelial (epi-on) corneal cross-linking procedures. METHODS: Thirty-two eye bank human donor corneas were equally randomized in eight groups; groups 1 to 3 and groups 4 to 8 underwent epi-off and epi-on delivery of riboflavin respectively. Riboflavin ophthalmic solutions were applied onto the cornea according to the manufacturers' instructions. The amount of riboflavin into the cornea was estimated, at preset time intervals during imbibition time, using theranostic UV-A device (C4V CHROMO4VIS, Regensight srl, Italy) and expressed as riboflavin score (d.u.). Measurements of corneal riboflavin concentration (expressed as µg/cm3) were also performed by spectroscopy absorbance technique (AvaLight-DH-S-BAL, Avantes) for external validation of theranostic measurements. RESULTS: At the end of imbibition time in epi-off delivery protocols, the average riboflavin score ranged from 0.77 ± 0.38 (the average corneal riboflavin concentration was 213 ± 190 µg/cm3) to 1.79 ± 0.07 (554 ± 103 µg/cm3). In epi-on delivery protocols, the average riboflavin score ranged from 0.17 ± 0.01 to 0.67 ± 0.19 (corneal riboflavin concentration ranged from 6 ± 5 µg/cm3 to 122 ± 39 µg/cm3) at the end of imbibition time. A statistically significant linear correlation (P ≤ 0.05) was found between the theranostic and spectrophotometry measurements in all groups. CONCLUSIONS: Real-time theranostic imaging provided an accurate strategy for assessing permeation of riboflavin into the human cornea during the imbibition phase of corneal cross-linking, regardless of delivery protocol. A large variability in corneal riboflavin concentration exists between clinically available ophthalmic formulations both in epi-off and epi-on delivery protocols.

Effect of accelerated high-fluence riboflavin and rose bengal-mediated corneal cross-linking on resistance to enzymatic digestion.

PURPOSE: This study evaluated the effect of high-fluence accelerated corneal cross-linking on the resistance to enzymatic digestion, assessing two chromophore/light combinations: riboflavin/UV-A light (RF/UV-A) and rose bengal/green light (RB/green). METHODS: Freshly prepared ex-vivo porcine corneas (n = 189) were divided into 8 groups groups. Group A corneas were unirradiated controls without chromophore soaking (A0), or soaked with riboflavin (A1) or rose bengal (A2). Group B corneas underwent accelerated epi-off RF/UV-A CXL at fluences of 5.4 J/cm² (B1), 10 J/cm² (B2), or 15 J/cm² (B3). Group C corneas underwent accelerated epi-off RB/green CXL at fluences of either 10 J/cm² (C1) or 15 J/cm² (C2). Following CXL, all corneas were digested in 0.3% collagenase-A solution, and the time until complete dissolution was measured. RESULTS: Non-irradiated controls exposed to RF and RB enhanced corneal resistance to collagenase digestion, with RB having a stronger effect than RF. RF/UV-A-treated corneas showed significantly increased digestion resistance with increasing fluence levels. RB/green-treated corneas displayed enhanced digestion resistance with each increase in fluence up to 10 J/cm²; a 15 J/cm² fluence yielded similar digestion resistance times to a 10 J/cm² fluence, suggesting a plateau effect in accelerated RB/green CXL protocols. CONCLUSIONS: When compared to standard-fluence treatments, high-fluence accelerated epi-off CXL using both riboflavin and rose bengal significantly increases resistance to enzymatic digestion. The optimal settings for clinical protocols might be 15 J/cm² (30 mW/cm² for 8 min 20 s) for RF/UV-A and 10 J/cm² (15 mW/cm² for 11 min 7 s) for RB/Green Light.

Evaluation of photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) in feline infectious keratitis-patient demographics, treatment protocols, risk factors, and treatment outcome: a retrospective study.

OBJECTIVES: To describe patient demographics and treatment protocols in a population of feline patients undergoing photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) as an adjunctive treatment for infectious keratitis. Furthermore, to determine the proportion of PACK-CXL treatment success in the population studied, explore risk factors for treatment failure, and provide recommendations for future PACK-CXL clinical studies. MATERIALS AND METHODS: Records from four veterinary ophthalmology practices were reviewed to identify eligible patients and extract data. Recorded variables included patient-related factors, ocular examination findings, PACK-CXL protocol parameters, and treatment outcome. RESULTS: Records for 153 cats (154 eyes) were included. Median age in the treatment success group was 8 years (interquartile range (IQR) 4-12), with a median ulcer depth of 30% (IQR 30-40). Median age in the treatment failure group was 10.5 years (IQR 4.75-12) with a median ulcer depth of 45.9% (IQR 30-75). Persian cats were the most represented brachycephalic breed (52 out of 64 cats). Modified PACK-CXL protocols were used, including fast energy delivery (134 eyes), and increased fluence (52 eyes). The overall proportion of success was 88% (95% CI 84-93), which was variable between clinics. Eighty-two of 89 mesocephalic cat eyes (92%), and 54 of 65 brachycephalic cat eyes (83%) were classified as treatment successes. CONCLUSIONS: PACK-CXL appeared to be a useful, adjunctive therapeutic modality for the treatment of infectious keratitis in the feline patient population presented here. Brachycephalic cats, older cats, and those with deeper ulcers may be at increased risk for treatment failure.

Analysis of Cytokine and Chemokine Level in Tear Film in Keratoconus Patients before and after Corneal Cross-Linking (CXL) Treatment.

Keratoconus (KC) is a degenerative corneal disorder whose aetiology remains unknown. The aim of our study was to analyse the expressions of cytokines and chemokines in KC patients before and after specified time intervals after corneal cross-linking (CXL) treatment to better understand the molecular mechanisms occurring before and after CXL in KC patients process of corneal regeneration.; Tear samples were gathered from 52 participants immediately after the CXL procedure and during the 12-month follow-up period. All patients underwent a detailed ophthalmological examination and tear samples were collected before and after CXL at regular intervals: 1 day before and after the surgery, at the day 7 visit, and at 1, 3, 6, 9, and 12 months after CXL. The control group consisted of 20 healthy people. 10 patients were women (50%) and 10 were men (50%). The mean age was 30 ± 3 years of age. Tear analysis was performed using the Bio-Plex 3D Suspension Array System. Corneal topography parameters measured by Scheimpflug Camera included: keratometry values (Ks, Kf), PI-Apex, PI-Thinnest, Cylinder.; All the 12 months post-op values of the KC patients' topographic measurements were significantly lower than the pre-op. As for the tear cytokine levels comparison between the patient and control groups, cytokine levels of TNF-α, IL-6, and CXCL-10, among others, were detected in lower amounts in the KC group. The pre-op level of IL-6 exhibited a significant increase the day after CXL, whereas comparing the day after the procedure to 12 months after CXL, this showed a significant decrease. Both TNF-α and IL-1 showed a significant decrease compared to the day before and after CXL. We observed significantly higher levels of IL-1ß, IL-10, IFN-γ and TNF-α in moderate and severe keratoconus than in mild keratoconus (p < 0.05). We also demonstrated a statistically significant positive correlation between both pre-op and 12 months after CXL TNF-α, IFN-γ, IL-6 and Ks and Kf values (p < 0.05, r > 0); Alterations of inflammatory mediators in tear fluid after CXL link with topographic changes and may contribute to the development and progression of KC.

Corneal biomechanical stiffness and histopathological changes after in vivo repeated accelerated corneal cross-linking in cat eyes.

Corneal cross-linking (CXL) has been proved efficiency for treating progressive keratoconus and other corneal ectasia diseases by stabilizing corneal geometry and biomechanics. However, the necessity of repeated CXL treatment in patients is unknown. This study aimed to investigate corneal biomechanical stiffness and change in corneal histopathological characteristics after repeated accelerated CXL (A-CXL) in cat eyes. A-CXL was performed with 0.1% riboflavin applied for 10 min, followed by ultraviolet A irradiation at 30 mW/cm2 for 3 min at 365 nm in 15 domestic cats. Corneas (n = 30) were divided into three groups: one-time accelerated corneal cross-linking (A-CXL*1 group), repeated accelerated corneal cross-linking (A-CXL*2 group), and an untreated control group. In A-CXL*2 group, A-CXL was repeated at 1-month intervals. In vivo ocular examinations were performed pre- and postoperatively. Biomechanical analysis was performed using a biotester biaxial testing system. We used the Mooney-Rivlin strain-energy function to describe corneal material properties. No infection in any case after A-CXL was observed. Biomechanical tests showed that the stress-strain curves of the two A-CXL groups were significantly different from those of the control group (P < 0.01), whereas stress-strain curve of the A-CXL*2 group was similar to that of the A-CXL*1 group (P > 0.05). Delayed epithelial healing and haze were observed 1 month after surgery. Stromal demarcation line depth measured with anterior spectral-domain optical coherence tomography was 187.6 ± 20.4 and 197.1 ± 11.5 µm for the A-CXL*1 and A-CXL*2 groups, respectively (P > 0.05). These results show that A-CXL can increase corneal biomechanics in cat eyes. The biomechanical enhancement of cat corneas treated with repeated A-CXL at 1-month intervals was similar to that of performing a one-time A-CXL. Repeated cross-linking procedures at short intervals may increase the risk of adverse reactions, and more caution should be taken in clinical applications.

The impact of UV cross-linking on corneal stromal cell migration, differentiation and patterning.

Previous studies have demonstrated that UV cross-linking (CXL) increases stromal stiffness and produces alterations in extracellular matrix (ECM) microstructure. In order to investigate how CXL impacts both keratocyte differentiation and patterning within the stroma, and fibroblast migration and myofibroblast differentiation on top of the stroma, we combined CXL with superficial phototherapeutic keratectomy (PTK) in a rabbit model. Twenty-six rabbits underwent a 6 mm diameter, 70 µm deep phototherapeutic keratectomy (PTK) with an excimer laser to remove the epithelium and anterior basement membrane. In 14 rabbits, standard CXL was performed in the same eye immediately after PTK. Contralateral eyes served as controls. In vivo confocal microscopy through focusing (CMTF) was used to analyze corneal epithelial and stromal thickness, as well as stromal keratocyte activation and corneal haze. CMTF scans were collected pre-operatively, and from 7 to 120 days after the procedure. A subset of rabbits was sacrificed at each time point, and corneas were fixed and labeled in situ for multiphoton fluorescence microscopy and second harmonic generation imaging. In vivo and in situ imaging demonstrated that haze after PTK was primarily derived from a layer of myofibroblasts that formed on top of the native stroma. Over time, this fibrotic layer was remodeled into more transparent stromal lamellae, and quiescent cells replaced myofibroblasts. Migrating cells within the native stroma underneath the photoablated area were elongated, co-aligned with collagen, and lacked stress fibers. In contrast, following PTK + CXL, haze was derived primarily from highly reflective necrotic "ghost cells" in the anterior stroma, and fibrosis on top of the photoablated stroma was not observed at any time point evaluated. Cells formed clusters as they migrated into the cross-linked stromal tissue and expressed stress fibers; some cells at the edge of the CXL area also expressed α-SM actin, suggesting myofibroblast transformation. Stromal thickness increased significantly between 21 and 90 days after PTK + CXL (P < 0.001) and was over 35 µm higher than baseline at Day 90 (P < 0.05). Overall, these data suggest that cross-linking inhibits interlamellar cell movement, and that these changes lead to a disruption of normal keratocyte patterning and increased activation during stromal repopulation. Interestingly, CXL also prevents PTK-induced fibrosis on top of the stroma, and results in long term increases in stromal thickness in the rabbit model.

Evaluation of risk factors for treatment failure in canine patients undergoing photoactivated chromophore for keratitis - corneal cross-linking (PACK-CXL): a retrospective study using additive bayesian network analysis.

BACKGROUND: Infectious keratitis is a common ophthalmic condition in canine patients. Sequelae can include keratomalacia and corneal perforation, a vision threatening outcome. Photoactivated chromophore for keratitis - corneal cross-linking (PACK-CXL) is a non-surgical, adjunctive treatment method for infectious keratitis. The goal of this retrospective, multicenter study was to determine risk factors for treatment failure following PACK-CXL in canine patients suffering from suspected infectious keratitis. Medical records from four veterinary ophthalmology services were reviewed, and information related to patient demographics, ophthalmic findings, the PACK-CXL protocol used, and epithelialization time was collected and analyzed. Due to the potential for intervariable relationships, an additive Bayesian network (ABN) analysis was performed to evaluate these complex relationships. RESULTS: Records for 671 eyes (668 dogs) were included in the analysis. Based on the ABN, in the population included here, patients who underwent an accelerated PACK-CXL protocol were less likely to experience treatment failure versus patients treated with a slow protocol. Mutual dependencies between exposure variables were identified by ABN, which would have been overlooked using classical regression. Corneal re-epithelialization time was shortened following PACK-CXL combined with topical medical therapy compared to PACK-CXL alone. CONCLUSIONS: No risk factors associated with treatment failure were identified in the population included in the present study. Canine patients may benefit from the use of accelerated PACK-CXL protocols, especially when combined with topical antibiotics and anti-collagenolytic therapy. The reasons for this apparent positive impact on treatment outcome remain unclear.

Corneal cross-linking in patients with keratoconus: up to 13 years of follow-up.

INTRODUCTION: To evaluate long-term safety and efficacy of corneal collagen cross-linking (CXL) in patients with keratoconus up to 13 years. MATERIALS AND METHODS: In this mono-centre exploratory study, we included all consecutive patients who underwent CXL in our cornea centre from 01/01/2007 to 12/30/2011 and met the inclusion criteria. CXL was performed in all patients according to the Dresden protocol. Evaluation included best-corrected visual acuity (BCVA), topographic keratometry by Scheimpflug corneal tomography and endothelial cell count (ECC). Follow-up measurements were taken up to 13 years after treatment were compared with baseline values. RESULTS: The study enrolled 168 eyes. The mean age of our patients was 26.3 years ± 7.8 years. A complete topographic dataset was available 1 year postoperatively for 142 eyes, 5 years postoperatively for 105 eyes, 10 years postoperatively for 61 eyes and 13 years postoperatively for 9 eyes. BCVA increased statistically significant after 1 year, 5 years and 10 years and non-significantly after 13 years. All keratometric parameters with exception of posterior astigmatism showed a statistically significant decrease after 1 year, 5 years and 10 years. After 13 years, the decrease was statistically significant only in Kmax, K2 and thinnest cornea. No significant changes in ECC were detected. Three eyes received Re-CXL, none of the eyes received penetrating keratoplasty and no infections occurred in this cohort. CONCLUSIONS: CXL can slow down or even stop the progression of keratoconus in the majority of cases. The effect is long-lasting with excellent safety.

Repeated sessions of PACK-CXL WA for the treatment of resistant bacterial keratitis: a retrospective study.

OBJECTIVE: The aim of this work is to evaluate the safety and efficacy of repeated sessions of photo-activated chromophore for keratitis-cross linking (PACK-CXL) window absorption (WA) for the treatment of resistant bacterial keratitis (BK). PATIENTS AND METHODS: This is a retrospective clinical cohort study. Thirty eyes with clinically suspected and lab-confirmed bacterial keratitis, resistant to appropriate antibiotic therapy- which was modified by sensitivity reports- for 2 weeks with failure of epithelialization for 4 weeks after the standard anti-microbial therapy (SAT) together with one setting of PACK-CXL WA were included. If after the first session of PACK-CXL, there is a start of improvement in the form of reduction of the size of corneal ulcer and stromal infiltrates together with the start of epithelialization on clinical examination and AS-OCT, another session of PACK-CXL WA was performed after one week, and so on, till the complete healing and resolution of bacterial keratitis and confirmation by negative bacterial culture. Identification of the micro-organisms was done by lab study before and after treatment. Corneal healing was evaluated by corneal examination and anterior segment OCT (AS-OCT). RESULTS: Thirty eyes of 30 patients were recruited in this study. They were 16 males and 14 females, their mean age was 44.3 ± 5.38 years. The mean ulcer size was 3.96 ± 1.87 (mm3), while the mean size of stromal infiltrates was 4.52 ± 2.24 (mm3). PACK-CXL WA treatment was performed an average of 2.87 times for the 30 eyes. Complete healing and resolution (Successful treatment) was observed in 27 eyes (90%) of cases and failure of epithelialization was observed only in 3 eyes (10%). Complete corneal healing was reported in the second month postoperatively in 90% of eyes. CONCLUSION AND RECOMMENDATION: PACK-CXL WA may be a promising, non-invasive treatment option for resistant bacterial keratitis. It may have a synergistic effect with standard antimicrobial treatment (SAT). Also, it can overcome the antibiotics resistance that has become rapidly spreading worldwide. Repeated sessions of PACK-CXL WA may be more effective for the treatment of resistant bacterial keratitis till complete epithelialization and resolution of BK than a single session with few complications. However, further prospective and comparative studies to support the results are needed.

In vitro susceptibility of canine corneal bacterial pathogens to three cross-linking protocols.

OBJECTIVE: To assess in vitro antibacterial efficacy of three cross-linking (XL) protocols on bacteria associated with canine ulcerative keratitis. METHODS: Three XL protocols: UVA 3 mW/cm2 for 60 min, UVA 3 mW/cm2 for 30 min, and UVA 30 mW/cm2 for 3 min with and without application of riboflavin and a riboflavin-only protocol were performed in vitro on the four most common bacterial genera isolated from cases of canine ulcerative keratitis treated at Dick White Referrals, UK. Zones of bacterial growth inhibition (GIZ) associated with treatment were measured and compared. RESULTS: The four most common isolates were Pseudomonas aeruginosa (PA) (48/140, 34.3%), Streptococcus spp. (32/140, 22.9%), Staphylococcus spp. (24/140, 17.1%) and Escherichia coli (EC) (11/140, 7.9%). PA, EC, Streptococcus canis (SC), and Staphylococcus pseudintermedius (SP), isolated from canine corneas, were selected for testing. EC and SC demonstrated growth inhibition following all UVA/riboflavin protocols. PA and SP only displayed growth inhibition following the 60 min UVA/riboflavin protocol. GIZ areas for 60 min UVA/riboflavin protocols were significantly greater than 30 and 3 min UVA/riboflavin protocols (p < .01) and there was no significant difference between 30 and 3 min UVA/riboflavin protocols. In respect to GIZ areas, EC was significantly more susceptible to XL than SP (p = <.01). CONCLUSIONS: All UVA/riboflavin XL protocols caused growth inhibition of EC and SC in vitro. PA and SP did not show clear growth inhibition in vitro following exposure to XL protocol settings of UVA 3 mW/cm2 for 30 min and UVA 30 mW/cm2 for 3 min.

A randomized clinical trial assessing theranostic-guided corneal cross-linking for treating keratoconus: the ARGO protocol.

The Assessment of theranostic guided riboflavin/UV-A corneal cross-linking for treatment of keratoconus (ARGO; registration number NCT05457647) clinical trial tests the hypothesis that theranostic-guided riboflavin/UV-A corneal cross-linking (CXL) can provide predictable clinical efficacy for halting keratoconus progression, regardless of treatment protocol, i.e., either with or without epithelial removal. Theranostics is an emerging therapeutic paradigm of personalized and precision medicine that enables real-time monitoring of image-guided therapy. In this trial, the theranostic software module of a novel UV-A medical device will be validated in order to confirm its accuracy in estimating corneal cross-linking efficacy in real time. During CXL procedure, the theranostic UV-A medical device will provide the operator with an imaging biomarker, i.e., the theranostic score, which is calculated by non-invasive measurement of corneal riboflavin concentration and its UV-A light mediated photo-degradation. ARGO is a randomized multicenter clinical trial in patients aged between 18 and 40 years with progressive keratoconus aiming to validate the theranostic score by assessing the change of the maximum keratometry point value at 1-year postoperatively. A total of 50 participants will be stratified with allocation ratio 1:1 using a computer-generated stratification plan with blocks in two treatment protocols, such as epithelium-off or epithelium-on CXL. Following treatment, participants will be monitored for 12 months. Assessment of safety and performance of theranostic-guided corneal cross-linking treatment modality will be determined objectively by corneal tomography, corneal endothelial microscopy, visual acuity testing and slit-lamp eye examination.

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

PURPOSE: To assess long-term efficacy and safety of iontophoresis-assisted transepithelial corneal cross-linking (I-CXL) for keratoconus. PATIENTS AND METHODS: Twenty-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. SETTING: Ophthalmology Clinic, University Hospital of Messina, Messina, Italy. RESULTS: At 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. CONCLUSIONS: Iontophoresis-assisted transepithelial CXL resulted to be safe and effective to stabilize progressive keratoconus in adults at a long-term follow-up.

One-year non-comparative observational study to evaluate corneal tomographic, densitometric, and aberrometric features following accelerated corneal cross-linking in progressive keratoconus.

PURPOSE: To evaluate the 12 months' changes in tomographic, densitometric, and aberrometric parameters in keratoconic eyes after accelerated corneal cross-linking (CCL) and classify a densitometric course in different stages of the keratoconus separately (mild, moderate, and severe). METHODS: In a prospective observational study, 67 keratoconic eyes of 67 patients that underwent accelerated epithelium-off corneal cross-linking (9 mW/cm2 and 10 min) for treatment of progressive keratoconus were included. Corneal tomographic, densitometric, and aberrometric values obtained using the Pentacam HR were recorded at the baseline and 3, 6, and 12 months post-operatively. RESULTS: One year after treatment, corrected distance visual acuity (CDVA) was improved, and maximum keratometry, thinnest pachymetry, higher order, and total root mean square (RMS) were significantly decreased (p < 0.001). Corneal densitometry values showed a significant elevation 3 months post-surgery compared to baseline and then decreased to baseline values at 1 year. Only the Anterior 0-2 mm zone densitometry at the 3rd month was different between the three groups. RMS at 1 year correlated with Anterior 0-2 mm, Anterior 2-6 mm, total corneal 0-2 mm, and total corneal 2-6 mm densitometry values in the 3rd month. Final CDVA at 12th month follow-up correlated with the Anterior 0-2 mm corneal densitometry in the 3rd month. CONCLUSION: Anterior 0-2 mm zone densitometry at the 3rd-month post-accelerated CCL is different in various stages of keratoconus. Due to the correlation between final aberrometric and peak densitometric values in keratoconic eyes, peak densitometric values can be used as a prognostic factor for the final visual outcomes after accelerated CCL.

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

PURPOSE: 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. METHODS: 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. RESULTS: 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 ± 0.44 days (range 2-4 days) in the DP/SH group and 3.43 ± 0.60 days (3 to 5 days) 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 1 month: 1.13 ± 1.51, 3 months: 3.53 ± 2.55, 6 months: 7.07 ± 1.42) compared to the SH group (postoperative 1 month: 0.87 ± 1.43, 3 months: 2.89 ± 2.62, 6 months 6.33 ± 1.29). The DP/SH group revealed faster subbasal nerve regeneration and less edema compared to the SH group. CONCLUSION: 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.

Repeated application of riboflavin during corneal cross-linking does not improve the biomechanical stiffening effect ex vivo.

PURPOSE: To evaluate whether repeated application of riboflavin during corneal cross-linking (CXL) has an impact on the corneal biomechanical strength in ex-vivo porcine corneas. DESIGN: Laboratory investigation. METHODS: Sixty-six porcine corneas with intact epithelium were divided into three groups and analyzed. All corneas were pre-soaked with an iso-osmolar solution of 0.1% riboflavin in a phosphate-buffered saline (PBS) solution ("riboflavin solution"). Then, the corneas in Groups 1 and 2 were irradiated with a standard epi-off CXL (S-CXL) UV-A irradiation protocol (3 mW/cm2 for 30 min); while the corneas in Group 3 were not irradiated and served as control. During irradiation, Group 1 (CXL-PBS-Ribo) received repeated riboflavin solution application while corneas in Group 2 (CXL-PBS) received only repeated iso-osmolar PBS solution. Immediately after the procedure, 5-mm wide corneal strips were prepared, and elastic modulus was calculated to characterize biomechanical properties. RESULTS: Significant differences in stress-strain extensiometry were found between two cross-linked groups with control group (P = 0.005 and 0.002, respectively). No significant difference was observed in the normalized stiffening effect between Groups 1 and 2 (P = 0.715). CONCLUSIONS: The repeated application of riboflavin solution during UV-A irradiation does not affect the corneal biomechanical properties achieved with standard epi-off CXL. Riboflavin application during CXL may be omitted without altering the biomechanical stiffening induced by the procedure.

Predictive factors of the accelerated transepithelial corneal cross-linking outcomes in keratoconus.

BACKGROUND: This study aimed to evaluate the clinical outcomes and assess preoperative characteristics that may predict outcomes in keratoconus 1 year after accelerated transepithelial corneal cross-linking (ATE-CXL). METHODS: This prospective study included 93 eyes of 84 consecutive keratoconus patients with 1-year follow-up after ATE-CXL. Preoperative characteristics included corneal astigmatism, anterior chamber depth, anterior chamber volume, radius of curvature, posterior elevation, central corneal thickness (CCT), thinnest corneal thickness, steepest meridian keratometry, flattest meridian keratometry, and the maximum keratometry (Kmax). Data were obtained preoperatively and at 1, 3, 6, and 12 months postoperatively. The patient eyes were grouped into 3 subgroups according to CCT and Kmax values to observe the changes of keratoconus progression. RESULTS: All patients were successfully operated without complications at any follow-up time point. Mean changes of Kmax from baseline at 6 and 12 months were - 0.60 ± 2.21 D (P = 0.011) and - 0.36 ± 1.58 D (P = 0.030), respectively. Eyes with a thinner CCT and higher Kmax values exhibited a tendency for topographic flattening of ≥1.0 D (P = 0.003; P = 0.003). In the subgroup comparison, the Kmax values decreased significantly at 6 and 12 months after ATE-CXL in the group with CCT ≤ 450 µm (P = 0.018 and P = 0.045); the Kmax values of the group with Kmax > 65.0 D decreased significantly at 6 months postoperatively (P = 0.025). CONCLUSION: ATE-CXL is a safe and effective treatment for keratoconus patients. Patients with thinner CCT and higher Kmax values are more likely to benefit from ATE-CXL.

Corneal higher-order aberration changes after accelerated cross-linking for keratoconus.

AIM: To evaluate changes in corneal higher-order aberrations (HOAs) following epithelium-off accelerated corneal cross-linking (A-CXL) and to explore the impact on visual acuity. METHODS: In this retrospective case series, 32 eyes of 24 patients with keratoconus (KC) underwent A-CXL. Treatment was delivered at 10 mW/cm2 for 9 min with a total dose of 5.4 J/cm2. The following anterior corneal HOAs: total corneal HOAs, trefoil, secondary trefoil, coma, secondary coma, secondary astigmatism and spherical aberrations were analysed using the Scheimpflug-Placido Sirius (CSO, Italy) corneal topographer at baseline and 12 months following treatment. Multivariate analysis was used to evaluate the independent effect of HOA subtypes on changes in uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA). RESULTS: At one year post CXL, UDVA and CDVA were significantly improved, -0.13 ± 0.19 LogMAR (P = 0.0005) and -0.08 ± .0.11 LogMAR (P = 0.0003), respectively. The mean preoperative trefoil, secondary trefoil, secondary coma and secondary astigmatism were 0.95 ± 0.46; µm, 0.20 ± 0.11; µm, 0.29 ± 0.19; µm and 0.42 ± 0.17 µm, respectively. At one year, the mean values decreased significantly to 0.77 ± 0.47 µm, 0.15 ± 0.11 µm, 0.25 ± 0.18 µm and 0.34 ± 0.18 µm, respectively (P < 0.05, for all). No independent relationship between any HOA changes and change in UDVA was observed. A reduction in secondary coma aberration was associated with a change in CDVA (95% CI 0.01-1.34, P = 0.048; ß = 0.67). CONCLUSION: A 9-min protocol of Accelerated corneal cross-linking is an effective treatment in improving corneal HOAs at 12 months follow up, in eyes with progressive keratoconus at one year follow-up. A change in secondary coma had a statistically significant and independent effect on CDVA.

Adverse events after riboflavin/UV-A corneal cross-linking: a literature review.

BACKGROUND: Riboflavin/UV-A corneal cross-linking (CXL) for treating keratoconus and iatrogenic corneal ectasia has been well-established as first treatment option to stabilize corneal tissue biomechanical instability. Although the plethora of clinical studies has been published into the field, there is no systematic review assessing the type and frequency of adverse events after CXL. METHODS: A systemic literature review on clinical safety and adverse events after CXL in patients with keratoconus and corneal ectasia was performed using PubMed. A literature search was performed for relevant peer-reviewed publications. The main outcome measures extracted from the articles were adverse events, endothelial cell density, corrected distance visual acuity and maximum simulated keratometry. RESULTS: The most frequent adverse events after CXL were corneal haze and corneal edema, which were mild and transient. The severe adverse events were infrequent (cumulative incidence: < 1.3%) after CXL. The clinical benefits of CXL highly outweighed the risks for the treatment of keratoconus and corneal ectasia. CONCLUSIONS: The severe adverse events with permanent sequelae are infrequent after CXL and all are associated with corneal de-epithelialization, such as infectious keratitis and corneal scarring.

Long-term evaluation of posterior corneal surface parameters after accelerated corneal cross-linking with a comparison with uncross-linked keratoconic eyes.

PURPOSE: To evaluate the 36 months changes in posterior corneal surface parameters in keratoconic eyes after accelerated corneal cross-linking and to compare the data with uncross-linked progressive and non-progressive keratoconic eyes. METHODS: Thirty five cross-linked, 30 uncross-linked progressive, and 30 uncross-linked non-progressive keratoconic eyes were included. Maximum keratometry (Kmax), thinnest pachymetry, minimum radius of curvature back (Rminback), asphericity back, posterior elevation and corneal densitometry, back corneal higher order aberrations (HOAs), back surface deviation (Db), final D, posterior radius of curvature (PRC) and 'B' unit values were recorded at baseline and at the 12, 24, 36 months follow-up. Data were analyzed with repeated measures ANOVA and paired t-tests. RESULTS: Kmax and thinnest pachymetry were significantly changed in the cross-linked and progressive uncross-linked groups. Rminback, asphericity back, and HOAs did not change in either group. Total posterior corneal densitometry improved; posterior elevation, Db and B unit worsened in the cross-linked group and did not change in the uncross-linked groups. PRC and final D worsened in the cross-linked and progressive uncross-linked groups, and did not change in the non-progressive group. CONCLUSION: Despite a decreased Kmax, the posterior corneal surface parameters, posterior elevation values were determined to have significantly worsened in the cross-linked group and this increase was higher than in progressive uncross-linked eyes.