Evaluation of Intrastromal Riboflavin Concentration in Human Corneas after Three Corneal Cross-Linking Imbibition Procedures: A Pilot Study

A fluorophotometric comparison of anterior chamber riboflavin delivery via corneal application and fornix instillation

INTRODUCTION AND OBJECTIVES

We investigated whether riboflavin self-administration by patients could be a feasible option for corneal cross-linking, given the considerable resources required to impregnate the cornea with riboflavin. We analysed whether administering riboflavin in the inferior fornix (the site of self-administration) results in non-inferior riboflavin concentrations as when applied directly on the cornea (the site of administration by medical personnel).

PATIENTS AND METHODS

We conducted a prospective study to evaluate riboflavin concentrations at six time-points (baseline, 5, 15, 30, 45 and 60min) in 18 healthy volunteers for each of two application sites: cornea and fornix. Anterior chamber riboflavin (Peschke® TE 0.25%) concentrations were measured by fluorophotometry (Fluorotron™ Master FM-2).

RESULTS

For the two application sites cornea and fornix, participants did not differ in terms of age and sex. At baseline, the autofluorescence in the anterior chamber was 16.7ng/mL (SD 5.5) and 14.6ng/mL (SD 4.6) (P=.221). After 30min, anterior chamber fluorescein concentrations had risen to 55.1ng/mL (SD 25.5) and 46.1ng/mL (SD 25.1) (P=.293) without a further relevant increase by 60min.

CONCLUSIONS

This study found that applying riboflavin drops in the inferior fornix was non-inferior to applying it directly to the cornea, based on fluorophotometric measurements of anterior chamber riboflavin concentrations. This suggests that self-application of riboflavin is feasible in terms of corneal riboflavin impregnation.

Progressive high-fluence epithelium-on accelerated corneal crosslinking: a novel corneal photodynamic therapy for early progressive keratoconus

Purpose

To assess the preliminary clinical results of a new, progressively higher fluence-pulsed light Epi-On accelerated crosslinking nomogram (PFPL M Epi-On ACXL) in the treatment of progressive keratoconus (KC).

Setting

Siena Crosslinking Center, Siena, Italy.

Methods

A prospective pilot open, non-randomized interventional study, including 32 eyes of 32 young-adult patients over 26 years old with Stages I-III progressive KC undergoing PFPL M Epi-On ACXL, was conducted. Riboflavin loading was performed by using Paracel I 0.25% for 4 min and Paracel II 0.22% for 6 min. The Avedro KXL System (Glaukos-Avedro, Burlington, USA) was used for pulsed-light accelerated crosslinking (ACXL) at air room 21% oxygenation and 13 min of UV-A irradiation. The treatment fluence was set at 7.2 J/cm2, 8.6 J/cm2, and 10.0 J/cm2 in corneas with baseline pachymetry <420 μm (group 1: 8 eyes), ≥ 420 μm <460 μm (group 2, 11 eyes), and ≥ 460 μm (group 3, 13 eyes), respectively. Uncorrected distance visual acuity (UDVA), best-spectacle corrected visual acuity (BSCVA), Scheimpflug corneal tomography, and anterior segment OCT (AS-OCT) data were collected at baseline and postoperatively at 1, 3, and 6 months.

Results

UDVA and BSCVA improved in all groups (P ≤ 0.05). Maximum keratometry values (K max) showed a significant decrease in the 10.0 J/cm2 group (Δ -1.68 D). The coma (HOAs) value improved significantly by the sixth month in all groups. OCT average demarcation lines were 211 ± 19 μm in group 1, 245 ± 23 μm in group 2, and 267 ± 21 μm in group 3.

Conclusions

The preliminary results show that pachymetry-based PFPL M Epi-On ACXL nomogram stabilizes ectasia progression. Higher fluence Epi-On ACXL increases CXL penetration, with better functional outcomes in the absence of complications.

Current clinical practice in corneal crosslinking for treatment of progressive keratoconus in four Nordic countries

PURPOSE

To evaluate clinical practice in the diagnosis and treatment of progressive keratoconus with corneal crosslinking (CXL) in four Nordic countries.

METHODS

A questionnaire was sent to all centres at which keratoconus patients are evaluated and CXL is performed in Sweden, Denmark, Norway and Iceland. Nineteen of 20 centres participated.

RESULTS

CXL is performed approximately 1300 times per year in these four Nordic countries with a population of around 21.7 million (2019). In most cases, progression is evaluated using the Pentacam HR, and the maximum keratometry reading (K_max ) is considered the most important parameter. The most frequently used treatment protocol in Scandinavia is the 9 mW/cm² epi-off protocol, using hydroxylpropyl methylcellulose riboflavin (HPMC-riboflavin). The participants deemed the following areas to be in most need of improvement: adaptation of the CXL protocol to individual patients (5/19), the development of effective epi-on treatment protocols (4/19), optimal performance of CXL in thin corneas (4/19), improvement of the definition of progression (2/19), and diagnosis of the need for re-treatment (2/19).

CONCLUSIONS

We concluded that the diagnosis of progressive keratoconus and the diagnostic equipment used are similar. Treatment strategies are also similar but are suitably different to provide an interesting basis for the comparison of treatment outcomes. The high degree of participation in this survey indicates the possibility of future scientific collaboration on CXL focusing on the areas deemed to need improvement. It would also be of interest to evaluate the possibility of creating a Nordic CXL Registry. The high number of CXL treatments performed ensures sufficient statistical power to solve many questions. Such a registry could be an important contribution to evidence-based care and would allow for longitudinal evaluation.

Transepithelial Enhanced Fluence Pulsed Light M Accelerated Crosslinking for Early Progressive Keratoconus with Chemically Enhanced Riboflavin Solutions and Air Room Oxygen

Purpose: To assess the 3-year clinical results of the 18 mW 7 J/cm² transepithelial enhanced fluence pulsed light M accelerated crosslinking in the treatment of progressive keratoconus (KC) with chemically enhanced hyper-concentrated riboflavin solutions without iontophoresis and with air-room oxygenation. Setting: Siena Crosslinking Center, Siena, Italy. Methods: Prospective pilot, open non-randomized interventional study including 40 eyes of 30 young adult patients over 21 years old (10 simultaneous bilateral) with early (Stage I and II) progressive KC undergoing TE-EFPL 18 mW/7 J/cm² ACXL (EFPL M TECXL). The 12 min and 58 s pulsed light (1 s on/1 s off) UV-A exposure treatments were performed with a biphasic corneal soaking using Paracel I 0.25% for 4 min and Paracel II 0.22% for 6 min riboflavin solutions and New KXL I UV-A emitter (Glaukos-Avedro, Waltham, USA) at an air room of 21% oxygenation. All patients completed the 3-year follow-up. Results: CDVA showed a statistically significant improvement in the third postoperative month (Δ + 0.17 d. e.) with a final gain of +0.22 d. eq. AK showed a statistically significant decrease in the sixth postoperative month (Δ − 1.15 diopters). K itmax showed a statistically significant decrease at 1-year follow-up (Δ − 1.3 diopters). The coma value improved significantly by the sixth month (Δ − 0.54 µm). MCT remained stable during the entire follow-up. No adverse events were recorded. Corneal OCT revealed a mean demarcation line depth at 282.6 ± 23.6 μm. Conclusions: Transepithelial enhanced fluence pulsed light M accelerated crosslinking with chemically enhanced riboflavin solution halted KC progression in young adult patients without iontophoresis and no intraoperative oxygen supplementation addressing the importance of increased fluence.

The Effect of Sodium Iodide on Stromal Loading, Distribution and Degradation of Riboflavin in a Rabbit Model of Transepithelial Corneal Crosslinking

Purpose

To evaluate effects of sodium iodide (NaI) on riboflavin concentration in corneal stroma before and during ultraviolet A (UVA) light exposure using a novel transepithelial corneal collagen crosslinking (CXL) procedure (EpiSmart CXL system, CXL Ophthalmics, Encinitas CA).

Methods

Riboflavin solutions with NaI (Ribostat, CXL Ophthalmics, Encinitas CA) and without NaI were used for CXL in rabbits using EpiSmart. A pilot study determined sufficient riboflavin loading time. Four rabbits were dosed and monitored. Riboflavin fluorescence intensity was assessed from masked slit-lamp photos. A 12 min loading time was selected. Sixteen additional rabbits received the two formulae in contralateral eyes for CXL. Riboflavin uptake was assessed at 0, 10, 15, 20, 25, and 30 min of UVA exposure using a scale for riboflavin fluorescence previously validated against stromal concentration. Post sacrifice, corneal stromal samples were analyzed for concentrations of riboflavin and riboflavin 5ʹ-phosphate.

Results

Eyes dosed with NaI riboflavin had higher riboflavin grades compared to eyes dosed with the NaI-free riboflavin formulation immediately after riboflavin loading and persisting throughout UVA exposure, with significantly higher (P < 0.01 to < 0.05) riboflavin grades from 15 through 25 min of UVA exposure. Riboflavin grades decreased more slowly in eyes dosed with NaI riboflavin through 25 minutes of UVA exposure. Minor conjunctival irritation was noted with or without NaI.

Conclusion

The addition of NaI to riboflavin solution is associated with increased riboflavin concentration in corneal stroma throughout a clinically relevant time course of UVA exposure. This effect may be a combination of enhanced epithelial penetration and reduced riboflavin photodegradation and should enhance intrastromal crosslinking.

Iontophoresis Corneal Cross-linking With Enhanced Fluence and Pulsed UV-A Light: 3-Year Clinical Results

PURPOSE

To assess 3-year safety and efficacy of enhanced-fluence pulsed-light iontophoresis cross-linking (EF I-CXL) in patients with progressive keratoconus.

METHODS

This prospective interventional pilot study included 24 eyes of 20 patients, with a mean age of 23.9 years (range: 15 to 36 years). Iontophoresis with riboflavin solution was used for stromal imbibition. The treatment energy was optimized at 30% (7 J/cm²) and ultraviolet-A power set at 18 mW/cm² × 6.28 minutes of pulsed-light on-off exposure, with a total irradiation time of 12.56 minutes. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), corneal tomography, and corneal optical coherence tomography (OCT) at baseline and 1, 3, 6, 12, 24, and 3 years postoperatively were evaluated.

RESULTS

At 3 years, average UDVA decreased from 0.50 ± 0.10 to 0.36 ± 0.08 logMAR (P < .05), average maximum keratometry decreased from 52.94 ± 1.34 to 51.4 ± 1.49 diopters (D) (Delta: -1.40 ± 0.80 D; P < .05), average coma improved from 0.24 ± 0.05 to 0.12 ± 0.02 µm (P = .001), and symmetry index decreased from 4.22 ± 1.01 to 3.53 ± 0.90 D. Corneal OCT showed demarcation line detection at 285.8 ± 20.2 µm average depth in more than 80% at 1 month postoperatively.

CONCLUSIONS

The 3-year results of EF I-CXL showed satisfactory I-CXL functional outcomes, increasing the visibility and the depth of demarcation line closer to epithelium-off standard CXL. [J Refract Surg. 2020;36(5):286-292.].

Chemically-Boosted Corneal Cross-Linking for the Treatment of Keratoconus through a Riboflavin 0.25% Optimized Solution with High Superoxide Anion Release

The purpose of this study was to evaluate the effectiveness and safety of a novel buffered riboflavin solution approved for corneal cross-linking (CXL) in progressive keratoconus and secondary corneal ectasia. Following the in vivo preclinical study performed on New Zealand rabbits comparing the novel 0.25% riboflavin solution (Safecross^®) containing 1% hydroxypropyl methylcellulose (HPMC) with a 0.1% riboflavin solution containing 0.10% EDTA, accelerated epithelium-off CXL was performed on 10 patients (10 eyes treated, with the contralateral eye used as control) through UV-A at a power setting of 9 mW/cm² with a total dose of 5.4 J/cm². Re-epithelialization was evaluated in the postoperative 7 days by fluorescein dye test at biomicroscopy; endothelial cell count and morphology (ECD) were analyzed by specular microscopy at the 1st and 6th month of follow-up and demarcation line depth (DLD) measured by anterior segment optical coherence tomography (AS-OCT) one month after the treatment. We observed complete re-epithelization in all eyes between 72 and 96 h after surgery (88 h on average). ECD and morphology remained unchanged in all eyes. DLD was detected at a mean depth of 362 ± 50 µm, 20% over solutions with equivalent dosage. SafeCross^® riboflavin solution chemically-boosted corneal cross-linking seems to optimize CXL oxidative reaction by higher superoxide anion release, improving DLD by a factor of 20%, without adverse events for corneal endothelium.

Transepithelial versus epithelium-off corneal crosslinking for progressive keratoconus

BACKGROUND

Keratoconus is the most common corneal dystrophy. It can cause loss of uncorrected and best-corrected visual acuity through ectasia (thinning) of the central or paracentral cornea, irregular corneal scarring, or corneal perforation. Disease onset usually occurs in the second to fourth decade of life, periods of peak educational attainment or career development. The condition is lifelong and sight-threatening. Corneal collagen crosslinking (CXL) using ultraviolet A (UVA) light applied to the cornea is the only treatment that has been shown to slow progression of disease. The original, more widely known technique involves application of UVA light to de-epithelialized cornea, to which a photosensitizer (riboflavin) is added topically throughout the irradiation process. Transepithelial CXL is a recently advocated alternative to the standard CXL procedure, in that the epithelium is kept intact during CXL. Retention of the epithelium offers the putative advantages of faster healing, less patient discomfort, faster visual rehabilitation, and less risk of corneal haze.

OBJECTIVES

To assess the short- and long-term effectiveness and safety of transepithelial CXL compared with epithelium-off CXL for progressive keratoconus.

SEARCH METHODS

To identify potentially eligible studies, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2020, Issue 1); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature database (LILACS); ClinicalTrials.gov; and World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not impose any date or language restrictions. We last searched the electronic databases on 15 January 2020.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) in which transepithelial CXL had been compared with epithelium-off CXL in participants with progressive keratoconus.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodology.

MAIN RESULTS

We included 13 studies with 723 eyes of 578 participants enrolled; 13 to 119 participants were enrolled per study. Seven studies were conducted in Europe, three in the Middle East, and one each in India, Russia, and Turkey. Seven studies were parallel-group RCTs, one study was an RCT with a paired-eyes design, and five studies were RCTs in which both eyes of some or all participants were assigned to the same intervention. Eleven studies compared transepithelial CXL with epithelium-off CXL in participants with progressive keratoconus. There was no evidence of an important difference between intervention groups in maximum keratometry (denoted 'maximum K' or 'Kmax'; also known as steepest keratometry measurement) at 12 months or later (mean difference (MD) 0.99 diopters (D), 95% CI -0.11 to 2.09; 5 studies; 177 eyes; I² = 41%; very low certainty evidence). Few studies described other outcomes of interest. The evidence is very uncertain that epithelium-off CXL may have a small (data from two studies were not pooled due to considerable heterogeneity (I² = 92%)) or no effect on stabilization of progressive keratoconus compared with transepithelial CXL; comparison of the estimated proportions of eyes with decreases or increases of 2 or more diopters in maximum K at 12 months from one study with 61 eyes was RR 0.32 (95% CI 0.09 to 1.12) and RR (non-event) 0.86 (95% CI 0.74 to 1.00), respectively (very low certainty). We did not estimate an overall effect on corrected-distance visual acuity (CDVA) because substantial heterogeneity was detected (I² = 70%). No study evaluated CDVA gain or loss of 10 or more letters on a logarithm of the minimum angle of resolution (logMAR) chart. Transepithelial CXL may result in little to no difference in CDVA at 12 months or beyond. Four studies reported that either no adverse events or no serious adverse events had been observed. Another study noted no change in endothelial cell count after either procedure. Moderate certainty evidence from 4 studies (221 eyes) found that epithelium-off CXL resulted in a slight increase in corneal haze or scarring when compared to transepithelial CXL (RR (non-event) 1.07, 95% CI 1.01 to 1.14). Three studies, one of which had three arms, compared outcomes among participants assigned to transepithelial CXL using iontophoresis versus those assigned to epithelium-off CXL. No conclusive evidence was found for either keratometry or visual acuity outcomes at 12 months or later after surgery. Low certainty evidence suggests that transepithelial CXL using iontophoresis results in no difference in logMAR CDVA (MD 0.00 letter, 95% CI -0.04 to 0.04; 2 studies; 51 eyes). Only one study examined gain or loss of 10 or more logMAR letters. In terms of adverse events, one case of subepithelial infiltrate was reported after transepithelial CXL with iontophoresis, whereas two cases of faint corneal scars and four cases of permanent haze were observed after epithelium-off CXL. Vogt's striae were found in one eye after each intervention. The certainty of the evidence was low or very low for the outcomes in this comparison due to imprecision of estimates for all outcomes and risk of bias in the studies from which data have been reported.

AUTHORS' CONCLUSIONS

Because of lack of precision, frequent indeterminate risk of bias due to inadequate reporting, and inconsistency in outcomes measured and reported among studies in this systematic review, it remains unknown whether transepithelial CXL, or any other approach, may confer an advantage over epithelium-off CXL for patients with progressive keratoconus with respect to further progression of keratoconus, visual acuity outcomes, and patient-reported outcomes (PROs). Arrest of the progression of keratoconus should be the primary outcome of interest in future trials of CXL, particularly when comparing the effectiveness of different approaches to CXL. Furthermore, methods of assessing and defining progressive keratoconus should be standardized. Trials with longer follow-up are required in order to assure that outcomes are measured after corneal wound-healing and stabilization of keratoconus. In addition, perioperative, intraoperative, and postoperative care should be standardized to permit meaningful comparisons of CXL methods. Methods to increase penetration of riboflavin through intact epithelium as well as delivery of increased dose of UVA may be needed to improve outcomes. PROs should be measured and reported. The visual significance of adverse outcomes, such as corneal haze, should be assessed and correlated with other outcomes, including PROs.

Iontophoretic Transepithelial Collagen Cross-Linking Versus Epithelium-Off Collagen Cross-Linking in Pediatric Patients: 3-Year Follow-Up

PURPOSE

To compare 3-year iontophoretic transepithelial corneal cross-linking (I-ON CXL) outcomes with epithelium-off collagen cross-linking (epi-off CXL) in pediatric patients.

METHODS

Forty eyes of 28 consecutive pediatric patients [mean age 14.3 ± 2.5 (SD) years; range, 9-18 years] with keratoconus were evaluated. Twenty eyes of 15 patients underwent I-ON and 20 eyes of 13 patients epi-off CXL. Mean corrected distance visual acuity, spherical equivalent, maximum keratometry (Kmax), posterior elevation of the thinnest point, and thickness of the thinnest point were evaluated. The Student t test was used to compare baseline and postoperative data. Keratoconus progression as a function of preoperative Kmax and cone location was evaluated.

RESULTS

At 36 months, corrected distance visual acuity statistically improved (from 0.18 ± 0.1 to 0.10 ± 0.1 logarithm of the minimum angle of resolution) in epi-off CXL, whereas spherical equivalent and posterior elevation of the thinnest point did not significantly change. Mean Kmax increased from the baseline +0.8 diopters (D) in epi-off and +2.9D in I-ON. In both groups, the thinnest point decreased. Keratoconus progression, defined by an increase of Kmax reading of the anterior corneal surface of at least 1.00D, occurred in 25% of epi-off and 50% of I-ON CXL over the 3-year period. Kmax value in I-ON, and cone location in both groups, seemed to be factors influencing the disease progression.

CONCLUSIONS

In pediatric patients, 3 years after treatment, epi-off CXL halted keratoconus progression in 75% of eyes, whereas I-ON CXL seemed to slow down keratoconus progression in 50% of eyes, mainly in those with highest Kmax and paracentral cone.

Transepithelial versus epithelium-off corneal crosslinking for corneal ectasia

This review compared the clinical results of transepithelial corneal crosslinking (CXL) to epithelium-off (epi-off) CXL in progressive corneal ectasia using a metaanalysis. The Cochrane databases and Medline were searched for randomized controlled trials (RCTs). Seven RCTs involving 505 eyes that met the eligibility criteria were identified. The epi-off CXL group showed significantly better outcomes in postoperative changes in maximum keratometry (K) during 1-year observation periods. Transepithelial CXL resulted in significantly greater post-treatment central corneal thickness and best spectacle-corrected visual acuity (BSCVA). The presence of a postoperative demarcation line was significantly more frequent after epi-off CXL than that after transepithelial CXL. No statistically significant difference was found between other parameters. Although patients in the transepithelial CXL group demonstrated a greater improvement in BSCVA compared with patients in the epi-off CXL group at the 1 year follow-up, transepithelial CXL had less impact on halting progressive corneal ectasia in terms of maximum K than epi-off CXL.

Efficacy of iontophoresis-assisted epithelium-on corneal cross-linking for keratoconus

Corneal cross-linking (CXL) is a noninvasive therapeutic procedure for keratoconus that is aimed at improving corneal biomechanical properties by induction of covalent cross-links between stromal proteins. It is accomplished by ultraviolet A (UVA) radiation of the cornea, which is first saturated with photosensitizing riboflavin. It has been shown that standard epithelium-off CXL (S-CXL) is efficacious, and it has been recommended as the standard of care procedure for keratoconus. However, epithelial removal leads to pain, transient vision loss, and a higher risk of corneal infection. To avoid these disadvantages, transepithelial CXL was developed. Recently, iontophoresis has been adopted to increase riboflavin penetration through the epithelium. Several clinical observations have demonstrated the safety and efficacy of iontophoresis-assisted epithelium-on CXL (I-CXL) for keratoconus. This review aimed to provide a comprehensive summary of the published studies regarding I-CXL and a comparison between I-CXL and S-CXL. All articles used in this review were mainly retrieved from the PubMed database. Original articles and reviews were selected if they were related to the I-CXL technique or related to the comparison between I-CXL and S-CXL.

Standard, transepithelial and iontophoresis corneal cross-linking: clinical analysis of three surgical techniques

BACKGROUND

To evaluate the clinical results of standard, transepithelial (TE) and iontophoresis (I) corneal cross-linking (CXL), in patients with progressive keratoconus.

METHODS

Thirty eyes of 30 patients with progressive keratoconus treated by CXL (10 by standard-CXL, 10 by TE-CXL and 10 by I-TE-CXL) with 12 months of follow-up. Pre- and postoperative ophthalmologic testing were: uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive examination (spherical error, spherical equivalent), corneal topography (corneal astigmatism, simulated maximum, minimum and average keratometry), aberrometry (coma and spherical aberration), pachymetry and endothelial cell density.

RESULTS

In all groups, UDVA and CDVA improved significantly after treatment. Furthermore, a significant improvement in spherical error, spherical equivalent, topographic and aberrometric outcomes was observed in 3 groups at 1 year posttreatment. No significant variations were recorded in corneal thickness and endothelial cellular density.

CONCLUSION

Our results showed efficacy, clinical and refractive stability after standard-CXL, TE-CXL and iontophoresis-CXL.

Systematic review and Meta-analysis comparing modified cross-linking and standard cross-linking for progressive keratoconus

AIM

To compare the effectiveness and safety between modified cross-linking (MC) and standard cross-linking (SC) in mild or moderate progressive keratoconus.

METHODS

Eligible studies were retrieved from four electronic databases, including CENTRAL, Clinical Trials gov, PupMed and OVID MEDLINE. We set post-surgical maximum K value (Kmax) as the primary outcome. In addition, uncorrected and corrected distant visual acuity (UDVA and UDVA), spherical equivalent (SE), endothelial cell density (ECD), central cornea thickness (CCT) and depth of demarcation line (DDL) were Meta-analyzed as secondary outcomes. Mean differences for these outcomes were pooled through either a random-effect model or fixed-effect model according to data heterogeneity.

RESULTS

Twenty-four comparative studies either on accelerated cross-linking (AC) compared with SC or on trans-epithelial cross-linking (TC) compared with SC were included and pooled for analysis. The results indicated that MC was significantly inferior to SC at delaying Kmax deterioration [AC vs SC 0.49 (95% CI: 0.04-0.94, I²=75%, P=0.03); TC vs SC 1.15 (95% CI: 0.54-1.75, I²=50%, P=0.0002)]. SE decreased significantly for SC when compared to AC [0.62 (95% CI: 0.38-0.86, I²=22%, P<0.00001)]. DDL of SC was more significantly deeper than that of TC [-133.49 (95% CI: -145.94 to -121.04, I²=33%, P<0.00001)]. Other outcomes demonstrated comparable results between MC and SC.

CONCLUSION

SC is more favorable at halting the progression of keratoconus, but visual acuity improvement showed comparable results between MCs and SC.

Iontophoresis-assisted corneal crosslinking using 0.1% riboflavin for progressive keratoconus

AIM

To report the clinical results of iontophoresis-assisted epithelium-on corneal crosslinking (I-CXL) using 0.1% riboflavin in distilled water for progressive keratoconus.

METHODS

In this prospective clinical study, we examined 94 eyes of 75 patients with progressive keratoconus who were treated with I-CXL using 0.1% riboflavin in distilled water. Best correct visual acuity (BCVA), Scheimpflug tomography, corneal topography, anterior segment optical coherence tomography, intraocular pressure, and endothelial cell density were evaluated at baseline and 1, 3, 6, 12, and 24mo after I-CXL.

RESULTS

After 24mo I-CXL, compared to the level at baseline, BCVA significantly improved 0.14±0.07 (P=0.010); mean keratometry signifi-cantly decreased 0.72±1.97 (P=0.021); maximum keratometry significantly reduced 2.30±5.01 (P=0.014); central keratoconus index significantly reduced 0.04±0.08 (P=0.007). The demarcation line was visible in 83.1% of eyes at 1mo after treatment, with a depth of 298.95±51.97 µm, and gradually indistinguishable. One eye had repeat treatment. Intraocular pressure and endothelial cell density did not change significantly.

CONCLUSION

I-CXL using 0.1% riboflavin halts keratoconus progression within 24mo, resulting in a significant improvement in visual and topographic parameters. Moreover, the depth of the demarcation line is similar to that previously reported in standard epithelium-off CXL procedures.