A randomized, controlled trial of corneal collagen cross-linking in progressive keratoconus: three-year results

Keratometry Changes Between Year One to Seven After Corneal Cross-Linking in Patients With Keratoconus

PURPOSE

We evaluated the timing at and extent to which midterm to long-term keratometric changes can occur in year 1 to 7 after corneal collagen cross-linking (CXL) in patients with keratoconus.

METHODS

We conducted a subgroup analysis of a retrospective cohort study of all consecutive patients who underwent CXL at our cornea center between 2007 and 2011. The inclusion criteria comprised CXL according to the Dresden protocol and a full set of keratometry parameters collected by Scheimpflug tomography preoperatively and at year 1, 3, 5, and 7 after CXL. In addition, best-corrected visual acuity was evaluated.

RESULTS

Sixty-three eyes of 47 patients were enrolled. Mean age was 25.46 years ±7.39 years (80.9% male patients). All relevant keratometric parameters showed significant improvement at year 1 after CXL (except for posterior astigmatism). According to mixed-effects model analysis, they all showed further significant change at different points in time between year 1, 3, 5, and 7 (except for K1). In addition, best-corrected visual acuity improved statistically significant between year 1, 3, 5, and 7. Suspected disease progression was noted in 22.2% of patients, mostly between year 1 and 3 after CXL.

CONCLUSIONS

After initial improvement 1 year after CXL, keratometric and functional parameters were stable until year 5 after CXL in most cases; further improvement can take place even after up to 7 years post-CXL. By contrast, in case of disease progression, changes seem to occur already between year 1 and 3 after CXL.

Reproducibility of Manifest Refraction in Patients With Keratoconus Compared With Healthy Subjects: A Prospective Cohort Study

PURPOSE

To measure and compare the inter-examiner reproducibility of manifest refraction in patients with keratoconus.

DESIGN

Prospective, inter-examiner reliability analysis comparing cases and controls.

METHODS

Patients with keratoconus (KC) and healthy subjects had undergone manifest refraction by the same 2 skilled optometrists; each was masked to the refraction of the other, on the same day. The KC group comprised patients with KC, who were recruited from the cornea clinic. The control group consisted of healthy individuals who wore spectacles and did not have KC. Participants for the control group were recruited from the clinic's staff, including doctors, technicians, nurses, and medical students. The study took place in 1 tertiary medical center in Israel from April 2021 to May 2022. The results of the manifest refraction and achieved corrected distance visual acuity (CDVA) were compared between groups.

RESULTS

A total of 120 eyes of 60 patients were enrolled in the study, 30 in the keratoconus group and 30 in the control group. A difference of 0.67 ± 0.83 diopters (D) and 0.19 ± 0.21 D in the absolute manifest cylinder was observed between the optometrists in the keratoconus (95% LoA, -0.96, 2.30) and control group (95% LoA, -0.22, 0.61), respectively (P < .001). Multivariate analysis revealed a 22-fold higher likelihood of an error exceeding 0.75 D in cylinder measurements (odds ratio = 22.24; 95% CI = 2.39-206.95) and a 10-fold likelihood of a difference of at least 1 row on the Snellen chart for corrected distance visual acuity (odds ratio = 10.32; 95% CI = 2.39-44.44) in the KC group.

CONCLUSIONS

When compared to healthy subjects, patients with KC exhibited greater variability in manifest refraction. This discrepancy has the potential to influence the decision-making process when managing patients with KC.

A pilot study on Langerhans cells in keratoconus patients by in vivo confocal microscopy before and after corneal cross-linking and correlation with eye rubbing

PURPOSE

The aim of this study was to investigate the corneal microstructure and Langerhans cells using in vivo confocal microscopy in keratoconus patients before and after cross-linking, and to correlate the morphologic findings with clinical and patient-reported outcomes, including eye rubbing (ER) behavior.

METHODS

Patients with progressive keratoconus undergoing iontophoresis-assisted epithelium-on cross-linking (I-CXL) were consecutively enrolled. In vivo confocal microscopy was performed before and 6 months after treatment. Patients were asked to quantify their ER behavior on a Visual Analogue Scale (VAS) and completed the Keratoconus Outcomes Research Questionnaire and the Ocular Surface Disease Index questionnaires at the same time points. Visual acuity, tear osmolarity, topography, aberrometry, and pachymetry of both eyes were assessed.

RESULTS

Thirteen patients were included in this pilot study. Preoperatively, the mean Langerhans cells density was 35,615 cells per mm2, and the median morphology was 3. The mean ER VAS before treatment was 7,077 out of 10. The ER VAS showed significant positive correlations with both Langerhans cells density and morphology of the study eye. After treatment, a statistically significant reduction in ER VAS and in Langerhans cells variables was observed. The mean sub-basal plexus nerve density was comparable to pre-operative values 6 months after I-CXL.

CONCLUSIONS

Based on this preliminary evidence, the presence of high density of mature Langerhans cells in the central cornea of keratoconus patients and its correlation with eye rubbing support the role of inflammation in keratoconus. The reduction in these markers after treatment may suggest a potential of CXL in moderating immune-related inflammation and eye rubbing in the medium term.

Could Automated Objective Measurements Acquired at the Preoperative Stage Estimate the Corrected Distance Visual Acuity after Corneal Cross-Linking in Keratoconus?

INTRODUCTION

Objective markers describing corneal optical density (COD), thinnest corneal thickness (TCT), and anterior (ARC) and posterior (PRC) surface radii over the 3 mm thinnest region of the cornea were investigated to provide a model for estimating corrected distance visual acuity (CDVA) after corneal cross-linking (CXL) in keratoconus.

METHODS

CDVA, COD, TCT, ARC, and PRC were monitored (using Pentacam™) over 1 year in patients with (1) keratoconus treated with routine CXL (2) relatively stable untreated keratoconus, and (3) age/gender-matched controls.

RESULTS

In group 1 (n = 77), the median logMAR CDVA (mode, interquartile range) improved significantly (p < 0.01) from 0.26 (0.22, 0.12-0.65) to 0.07 (0.00, 0.02-0.21). The mean (± standard deviation, 95% confidence interval) COD (in 0-100 grey scale units) in the 0-2 mm central anterior corneal region (0-2 ant), TCT (µm), ARC (mm), and PRC (mm) changed significantly (p < 0.01), from 21.2 (± 3.70, 20.4-22.0), 454 (± 40.0, 446-462), 6.49 (± 0.71, 6.33-6.65), and 4.81 (± 0.65, 4.66-4.96) to 31.5 (± 9.19, 29.5-33.6), 423 (± 49.3, 412-434), 6.78 (± 0.80, 6.60-6.98), and 4.74 (± 0.64, 4.59-4.88), respectively, but remained stable in groups 2 (n = 23) and 3 (n = 24). Significant relationships (p < 0.01) were uncovered between postop CDVA and preop values of COD, TCT, ARC, and PRC. Multilinear regression revealed significant correlations between CDVA at 1 year and preop COD, TCT, ARC, and PRC (r2 = 0.533, r20-2ant = 0.126, r2TCT = 0.321, r2ARC = 0.506, r2PRC = 0.467). Including preop CDVA further enhanced this correlation (r2 = 0.637, r2LogMAR CDVApreop = 0.566).

CONCLUSION

CXL improved CDVA, increased COD and ARC, and reduced TCT and PRC. The chance of correctly estimating the CDVA at 1 year after CXL using preoperative markers of COD, TCT, ARC, and PRC is 53%, improving to 64% with the inclusion of preoperative CDVA. Objective measurements taken at the preoperative screening stage may be useful to estimate the likely postoperative CDVA when preoperative CDVA measures are unreliable or unobtainable.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT06522789.

Prediction model for treatment outcomes 3 years after corneal cross-linking for keratoconus

PURPOSE

This study aimed to identify preoperative factors that predict visual acuity and Kmax 3 years after corneal cross-linking (CXL) in patients with keratoconus (KC), and to develop a prediction model.

METHODS

We enrolled 68 patients with KC and followed up on 100 eyes that received CXL for at least 3 years. Preoperative data, including age, UDVA, CDVA, cylinder, SE, and the parameters of tomography including Kmax were collected as predictors. The primary outcomes were changes in CDVA (Delta CDVA) and Kmax (Delta Kmax) postoperatively. Univariate and multivariate linear regression were used to identify the correlation between the primary outcomes and predictors and establish prediction models.

RESULTS

Both CDVA and Kmax remained stable from baseline to 3 years after CXL: from 0.25 ± 0.18 to 0.22 ± 0.20 (P = 0.308) and from 58.70 ± 9.52 D to 57.02 ± 8.83 D (P = 0.187), respectively. Multivariate analysis showed that worse preoperative CDVA (ß coefficient - 0.668, P < 0.001) and lower preoperative Kmean (ß coefficient 0.018,P < 0.001) were associated with greater improvement in CDVA after CXL. A smaller preoperative eccentricity (ß coefficient 8.896, P = 0.01) and a higher preoperative Kmean (ß coefficient - 1.264, P < 0.001) predicted a more flattening of postoperative Kmax. The prediction model for CDVA (R2 = 0.43) and Kmax (R2 = 0.37) could accurately estimate treatment outcomes.

CONCLUSIONS

CXL is highly effective in halting or preventing further progression of KC. The preoperative factors CDVA and Kmean were able to predict visual acuity changes 3 years after CXL. And preoperative eccentricity and Kmean could predict Kmax changes 3 years after CXL.

Crosslinking with UV-A and riboflavin in progressive keratoconus: From laboratory to clinical practice - Developments over 25 years

Changes in the biomechanical and biochemical properties of the human cornea play an important role in the pathogenesis of ectatic diseases. A number of conditions in primarily acquired (keratoconus or pellucid marginal degeneration) or secondarily induced (iatrogenic keratectasia after refractive laser surgeries) ectatic disorders lead to decreased biomechanical stability. Corneal collagen cross-linking (CXL) represents a technique to slow or even halt the progression of ectatic pathologies. In this procedure, riboflavin is applied in combination with ultraviolet A radiation. This interaction induces the production of reactive oxygen species, which leads to the formation of additional covalent bonds between collagen molecules and subsequent biomechanical corneal strengthening. This procedure is so far the only method that partially interferes etiopathogenetically in the treatment of ectatic diseases that slows or stops the process of corneal destabilization, otherwise leading to the need for corneal transplantation. Besides, CXL process increases markedly resistance of collagenous matrix against digesting enzymes supporting its use in the treatment of corneal ulcers. Since the discovery of this therapeutic procedure and the first laboratory experiments, which confirmed the validity of this method, and the first clinical studies that proved the effectiveness and safety of the technique, it has been spread and adopted worldwide, even with further modifications. Making use of the Bunsen-Roscoe photochemical law it was possible to shorten the duration of this procedure in accelerated CXL and thus improve the clinical workflow and patient compliance while maintaining the efficacy and safety of the procedure. The indication spectrum of CXL can be further expanded by combining it with other vision-enhancing procedures such as individualized topographically-guided excimer ablation. Complementing both techniques will allow a patient with a biomechanically stable cornea to regularize it and improve visual acuity without the need for tissue transplantation, leading to a long-term improvement in quality of life.

Assessment of Corneal Cross-Linking Effect on Progressive Keratoconus by Using the ABCD Grading System

Purpose

The aim of this study was to assess changes in corneal parameters 6 months after corneal cross-linking for progressive keratoconus, using the ABCD system.

Patients and Methods

This retrospective study was conducted at the King Khaled Eye Specialist Hospital (Riyadh, Saudi Arabia) between January 1 and July 30, 2022. This study included 16 eyes of 16 patients with keratoconus who underwent corneal cross-linking at the same hospital and were at least 18 years old. At least one preoperative (T0) and one postoperative examination was performed for each patient. Six months after the procedure (T1), patients underwent corneal tomography. The parameters A, B, C, and D were also evaluated. Other parameters monitored included maximal keratometry (Kmax) (K1 and K2), Belin/Ambrósio Enhanced Ectasia Display, and index vertical asymmetry. The progression of ectasia was identified by a consistent change in at least two parameters: steepening of the anterior corneal surface or the posterior corneal surface, thinning or an increase in the rate at which the corneal thickness changed from the periphery to the thinnest point, where the magnitude of the change was greater than the normal noise of the testing system.

Results

Among the patients, 68.8% were men. The patients' average age was 25.8±5 years. Throughout the 6-month postoperative follow-up, parameters A, B, and C exhibited substantial changes (P = 0.000 for parameters A, B, and C). Parameter A increased 6 months after surgery, whereas parameters B and C decreased. Preoperatively and 6 months after surgery, Kmax, K1, and Belin/Ambrosio-enhanced ectasia demonstrated substantial differences. However, parameter D, K2, and the average pachymetric progression index did not change significantly.

Conclusion

Anterior and posterior corneal curvatures and corneal thickness profiles can be useful for monitoring the progression of keratoconus and the success of the corneal cross-linking operation.

Conventional Epithelial-Off Corneal Crosslinking in Patients With Progressive Keratoconus: 10-Year Outcomes

PURPOSE

Corneal crosslinking (CXL) is the standard treatment of progressive keratoconus (KC). We evaluated the safety and 10-year outcomes of conventional "epithelial-off" CXL for progressive KC for the first time in a cohort in France.

METHODS

We conducted a retrospective review of patients undergoing conventional CXL (Dresden protocol) in our tertiary ophthalmology department from 2006 to 2011 with 10-year follow-up. The primary outcome was change in preoperative versus postoperative keratometry measured by maximum keratometry (Kmax), steep keratometry (K2), flat keratometry (K1), mean keratometry (Km), and topographic cylinder. Secondary outcomes were changes in visual and refractive outcomes. We report postoperative complications and adverse events.

RESULTS

Eighty-nine eyes from 76 patients (67% male patients, mean age 22.7 ± 7.6 years) were included. Mean Kmax (-2.31 ± 2.98 diopters (D); P < 0.00001), K2 (-2.07 ± 3.15 D; P < 0.00001), K1 (-1.00 ± 2.29 D; P = 0.00008), Km (-1.53 ± 2.47 D; P < 0.00001), and topographic cylinder (-1.15 ± 2.53 D; P = 0.00004) significantly decreased 10 years after CXL compared with preoperative baseline. Significant decreases were still observed between 5 and 10 years after for mean Kmax, mean K2, mean K1, and mean Km. Mean distance best spectacle-corrected visual acuity and mean manifest refraction spherical equivalent were significantly improved after 10 years versus before CXL. The 10-year rate of repeat CXL was n = 3/76 patients (4%) (all younger than 18 years at first CXL) and of loss of >3 lines in best spectacle-corrected visual acuity was n = 1/76 patients (1%).

CONCLUSIONS

Progressive KC was effectively stabilized with a prolonged flattening and maintenance of functional vision improvements after 10 years. Repeat CXL was rare and only required among younger patients.

Safety and Efficacy of Epithelium-Off Corneal Collagen Cross-Linking for the Treatment of Corneal Ectasia: A Report by the American Academy of Ophthalmology

PURPOSE

To review the evidence on the safety and effectiveness of epithelium-off corneal collagen cross-linking (CXL) for the treatment of progressive corneal ectasia.

METHODS

A literature search of the PubMed database was most recently conducted in March 2024 with no date restrictions and limited to studies published in English. The search identified 359 citations that were reviewed in abstract form, and 43 of these were reviewed in full text. High-quality randomized clinical trials comparing epithelium-off CXL with conservative treatment in patients who have keratoconus (KCN) and post-refractive surgery ectasia were included. The panel deemed 6 articles to be of sufficient relevance for inclusion, and these were assessed for quality by the panel methodologist; 5 were rated level I, and 1 was rated level II. There were no level III studies.

RESULTS

This analysis includes 6 prospective, randomized controlled trials that evaluated the use of epithelium-off CXL to treat progressive KCN (5 studies) and post-laser refractive surgery ectasia (1 study), with a mean postoperative follow-up of 2.4 years (range, 1-5 years). All studies showed a decreased progression rate in treated patients compared with controls. Improvement in the maximum keratometry (Kmax) value, corrected distance visual acuity (CDVA), and uncorrected distance visual acuity (UDVA) was observed in the treatment groups compared with control groups. A decrease in corneal thickness was observed in both groups but was greater in the CXL group. Complications were rare.

CONCLUSIONS

Epithelium-off CXL is effective in reducing the progression of KCN and post-laser refractive surgery ectasia in most treated patients with an acceptable safety profile.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Intereye Asymmetry as a Predictor of Progression in Patients With Untreated Keratoconus: Findings From a Longitudinal Study

PURPOSE

The purpose of this study was to evaluate interocular predictors of progression in patients with untreated keratoconus.

METHODS

This is a multicenter longitudinal observational study with real-world data collected through the Save Sight Keratoconus Registry. Patients between the period of June 2000 and September 2022 were included in this study. Parameters such as patient age, sex, ocular history, visual acuity, K2, Max-K, and thinnest corneal thickness pachymetry (TCT) were analyzed.

RESULTS

There were 4342 untreated eyes from 2171 patients with keratoconus. A total of 333 patients showed progression of either Max-K, TCT, or both, whereas 1838 patients showed stable parameters. Factors associated with a higher incidence of progression in Max-K were younger baseline age (HR 0.96 per year older; 95% CI 0.95-0.98, P < 0.0001) and a higher baseline intereye asymmetry in Max-K (HR 1.02 per higher diopter; 95% CI 1.00-1.04, P = 0.04). A younger baseline age was the only predictor of progression in TCT (HR 0.97 per year older; 95% CI 0.95-0.99, P = 0.001).

CONCLUSIONS

Age is the most significant predictor of progression for both corneal thinning and progression of Max-K. Interocular asymmetry in Max-K at baseline could be used as part of an algorithm for determining the risk of keratoconus progression. It is recommended that patients with higher interocular asymmetry in Max-K have a closer follow-up of both eyes as they are at a higher risk of progression.

The impact of interrupted corneal collagen crosslinking (CXL) treatment

PURPOSE

To evaluate progression of keratoconus in patients where CXL treatment was interrupted due to insufficient swelling of the cornea.

METHODS

A retrospective review was conducted of all patients with keratoconus diagnosis who underwent CXL at the Department of Ophthalmology, Örebro University Hospital (USÖ) during the years 2010-2017. In total 377 eyes of 280 patients were screened for inclusion. In 17 eyes (15 patients), the treatment was interrupted due to insufficient swelling of the cornea. Patient journals were reviewed and keratometry examinations were analysed for long-term progression.

RESULTS

Eleven eyes (nine patients) were included in the study. Five eyes showed no signs of progression after the interrupted CXL treatment. In one eye progression continued, however, first after a period of a number of years, indicating a delayed course of clinical progression.

CONCLUSION

This study indicates that debridement of the corneal epithelium and riboflavin administration without intense UVA radiation may slow or arrest the progression of keratoconus, likely due to photosensitisation from ambient light.

Dramatic Reduction in Corneal Transplants for Keratoconus 15 Years After the Introduction of Corneal Collagen Crosslinking

PURPOSE

The aim of this study was to investigate the effect of the implementation of corneal collagen crosslinking (CXL) on the frequency of corneal transplants among patients with keratoconus (KC) in the same region.

METHODS

Before the introduction of CXL in 2007, 55 primary corneal transplants had been conducted in patients with KC (2005 and 2006) at the Department of Ophthalmology, Oslo University Hospital, Norway. We collected data from our corneal transplant registry for 2021 and 2022. The primary outcome was the number of corneal transplants performed in patients with KC. Age, sex, visual acuity (logarithm of the minimal angle of resolution), KC stage according to the Amsler-Krumeich classification system, and steepest keratometry reading (maximum keratometry, Pentacam, HR) were recorded. Furthermore, we registered the annual number of CXL treatments conducted from 2007 to 2022.

RESULTS

A total of 352 corneal transplants were performed in 2021 and 2022. Among them, 11 (3.1%) were transplants for patients with KC. All included patients were male; further, 90.1% and 9.1% of the patients were graded stages 4 and 3, respectively. The mean maximum keratometry was 79.0 diopter (range 61.0-109). The mean best-corrected visual acuity (logarithm of the minimal angle of resolution) was 1.3 (range 0.2-3.0). In 2021 to 2022, 431 CXL treatments were performed.

CONCLUSIONS

There was a significant decrease in the number of corneal transplants performed in patients with KC 15 years after the introduction of CXL. This indicates that the availability of CXL treatment over many years may considerably reduce the need for keratoplasties in this group of patients.

Accelerated Corneal Crosslinking to Arrest Progression of Corneal Ectasia: A Prospective Multicenter Study

OBJECTIVES

To report the results of epithelium-off accelerated corneal collagen crosslinking (accelerated corneal crosslinking [ACXL]) in patients with progressive keratoconus.

METHODS

This prospective, nonrandomized, noncomparative, interventional, multicenter clinical study included all patients who underwent ACXL, either continuous (c-ACXL; 9 mW/cm 2 , 10', 5.4 J/cm 2 ) or pulsed (p-ACXL; 2″ON/1″OFF, 30 mW/cm 2 , 4.5', 5.4 J/cm 2 ) between January 2014 and May 2017. Best-corrected visual acuity, sphere, cylinder, spherical equivalent, and topographical keratometry data were collected preoperatively and at 1, 3, 6, 12, 18, and 24 months postoperatively.

RESULTS

Ninety-six eyes of 78 patients were included. The mean age was 20.8±4.4 years (14-33) for c-ACXL and 26.7±7.7 years (12-37) for p-ACXL. The mean best-corrected visual acuity was 0.4±0.4 for c-ACXL and 0.01±0.1 for p-ACXL preoperatively, and 0.3±0.3 ( P =0.0014) and -0.01±0.1 ( P =0.1554), respectively, at the last follow-up. The subjective sphere and spherical equivalent did not show statistically significant differences between the time points ( P >0.05). The subjective cylinder showed significant differences ( P =0.0013 for c-ACXL; P =0.0358 for p-ACXL). Keratometric values (K steep , K flat , and SimK) remained stable, with no statistically significant differences ( P >0.05). No major complications were noted.

CONCLUSIONS

Both c-ACXL and p-ACXL are equally safe and effective ACXL protocols in stabilizing the progression of keratoconus and can be considered alternatives to the conventional Dresden protocol.

An in vitro investigation into the impact of corneal rinsing on riboflavin/UVA corneal cross-linking

BACKGROUND

Corneal cross-linking (CXL) using riboflavin and ultraviolet-A light (UVA) is a treatment used to prevent progression of keratoconus. This ex vivo study assesses the impact on CXL effectiveness, as measured by tissue enzymatic resistance and confocal microscopy, of including a pre-UVA corneal surface rinse with balanced salt solution (BSS) as part of the epithelium-off treatment protocol.

METHODS

Sixty-eight porcine eyes, after epithelial debridement, were assigned to six groups in three experimental runs. Group 1 remained untreated. Groups 2-6 received a 16-min application of 0.1% riboflavin/Hydroxypropyl methylcellulose (HPMC) drops, after which Group 3 was exposed to 9 mW/cm2 UVA for 10 min, and Groups 4-6 underwent corneal surface rinsing with 0.25 mL, 1 mL or 10 mL BSS followed by 9 mW/cm2 UVA exposure for 10 min. Central corneal thickness (CCT) was recorded at each stage. Central 8.0 mm corneal buttons from all eyes were subjected to 0.3% collagenase digestion at 37 °C and the time required for complete digestion determined. A further 15 eyes underwent fluorescence confocal microscopy to assess the impact of rinsing on stromal riboflavin concentration.

RESULTS

Application of riboflavin/HPMC solution led to an increase in CCT of 73 ± 14 µm (P < 0.01) after 16 min. All CXL-treated corneas displayed a 2-4 fold greater resistance to collagenase digestion than non-irradiated corneas. There was no difference in resistance between corneas that received no BSS rinse and those that received a 0.25 mL or 1 mL pre-UVA rinse, but each showed a greater level of resistance than those that received a 10 mL pre-UVA rinse (P < 0.05). Confocal microscopy demonstrated reduced stromal riboflavin fluorescence after rinsing.

CONCLUSIONS

All protocols, with and without rinsing, were effective at enhancing the resistance to collagenase digestion, although resistance was significantly decreased, and stromal riboflavin fluorescence reduced with a 10 mL rinse. This suggests that a 10 mL surface rinse can reduce the efficacy of CXL through the dilution of the stromal riboflavin concentration.

Lenticule addition keratoplasty for the treatment of keratoconus: A systematic review and critical considerations

Keratoconus is a corneal disorder characterized by the progressive thinning and bulging of the cornea. Currently, the major goal of management is to halt its progression, restore normal corneal strength, prevent acute complications, and save vision. Penetrating keratoplasty and deep anterior lamellar keratoplasty as conventional surgical methods for advanced keratoconus are limited by relatively high rates of immune intolerance, slow post-operational recovery, high costs, and shortage of donor corneas. Recently, the development of lenticule addition keratoplasty enables the restoration of corneal thickness simply by implanting a lenticule into the stromal pocket created with the femtosecond laser, which can originate from cadaver corneas or more appealing, be extracted from patients via a small-incision lenticule extraction (SMILE) surgery. As the first systematic review in this field, we critically review publications on lenticule addition keratoplasty and provide our perspectives on its clinical application and the focus of future research.

Development of a Web-Based Algorithm for Understanding the Intraocular Lens-Based Surgery in Stable and Progressing Keratoconus for Non-Specialist Ophthalmologists

PURPOSE

To propose an algorithm to facilitate lens-based surgery in keratoconus.

METHODS

A literature review was performed to prepare a software algorithm based on cone location, stability, best spectacle-corrected distance visual acuity (BSCVA) level and whether there is a clear or cataractous lens. The software usability was assessed through a 10-question questionnaire and two hypothetical keratoconus case histories (moderately simple and moderately complex) given to 15 trainees. The usability questionnaires were graded on a Likert scale (1 = strongly disagree to 5 = strongly agree) and two case histories (1 = very difficult to 7 = very easy).

RESULTS

The algorithm can be found at https://www.sussexeyelaserclinic.co.uk/keratoconus/. Thirteen trainees completed the questionnaire. 91.9% would frequently use it; for 100%, it was easy to use independently without technical support; for 63.7%, it was strongly integrated; for 100%, it was consistent; 100% thought that most people would learn to use it quickly, 91.9% found the system not cumbersome to use, felt very confident to use it and need not learn a lot to use it. The first case was found easy by 63.7% and the second by 45%.

CONCLUSION

We present an algorithm as a guide for lens-based surgery in stable and progressing keratoconus, which is classified based on cone location. This algorithm will help trainee and "non-specialist" ophthalmic surgeons understand the pre-operative planning for the surgery and referral to the "specialist" corneal surgeon, considering factors such as progression, BSCVA, keratometry, topography and apex location of the cone in keratoconus patients.

Photo-controllable drug releasing bulk polyacrylic intraocular lens material for safer posterior capsular opacification prevention

Posterior capsular opacification (PCO) is the most common complication that occurs after intraocular lens (IOL) implantation in cataract therapy. In recent years, IOLs have been developed as drug delivery platforms, but concerns over the safety of uncontrolled proliferative drug release have arisen. Therefore, a controlled drug release strategy is needed for safer PCO prevention. In this study, a new monomer contained coumarin group was introduced in material preparation, and poly(ethylene glycol phenyl ether methacrylate-co-2-(2-ethoxyethoxy) ethyl acrylate-co-7-(2-methacryloyloxyethoxy)-4-methylcoumarin) (PEEC) acrylic IOL materials were synthesized. The antiproliferative drug 5-fluorouracil (5-FU) could be chemically grafted to the PEEC IOL materials easily via a light induced [2 + 2] cycloaddition reaction with the coumarin group, getting drug-loaded IOL (PEEC@5-FU IOL). The PEEC@5-FU IOL exhibited excellent optical and mechanical properties and biocompatibility. More importantly, the loaded 5-FU could be easily controlled from release by light irradiation via photo-dissociation of the cyclobutane ring that was obtained by the [2 + 2] cycloaddition reaction of 5-FU and coumarin. The in vitro and in vivo experiments demonstrated that such photo-controllable drug release IOL could effectively prevent PCO after implantation in a safe way.

Corneal Fourier and Belin-Ambrósio Enhanced Ectasia Analysis in Healthy 4-Year-Old White Children

PURPOSE

The aim of this study was to provide normative databases of Fourier analysis (FA) and Belin-Ambrósio enhanced ectasia display (BAD) in healthy White 4-year-old emmetropic children.

METHODS

FA parameters analyzed were spherical component (SRmin), spherical eccentricity (SEcc), maximal decentration (MD), regular astigmatism at the center (Astigm. C) and periphery (Astigm. P), and irregularity (I). The parameters obtained by BAD included summary indicator BAD D, anterior corneal curvature (K1 and K2, D), maximal keratometry (Kmax, D), maximal Ambrósio relational thinnest (ART max), and pachymetric and BAD indices.

RESULTS

Eighty-nine eyes of eighty-nine 4-year-old children were included. The mean values of FA parameters were the following: SRmin 7.77, SEcc 0.600, MD 0.160, Astigm. C 0.070, Astigm. P 0.050, and I 0.019. The mean K1 and K2 in our study group were 42.92 ± 1.29 D and 43.75 ± 1.41 D, with the mean BAD D value 0.42 ± 0.67. The mean PPI min 0.629 ± 0.117, PPI max 1.059 ± 0.155, PPI avg 0.847 ± 0.103, Kmax 44.10 ± 1.39, and median of ART max 515.0 were recorded. No statistically significant differences between male and female sex in any of FA or BAD parameters were found.

CONCLUSIONS

This is the first study providing large normative data on FA and BAD in 4-year-old White emmetropic children. We proposed a cutoff D value for early ectasia and clinical keratoconus in 4-year-old children.

Effect of intrastromal corneal ring segments on in vivo corneal biomechanics in keratoconus: 1-year results

PURPOSE

To evaluate the 1-year effects of the implantation of intrastromal corneal ring segments (ICRS) in keratoconus (KC) on the dynamic corneal response (DCR) parameters obtained with the Corvis.

SETTING

Fernández-Vega Ophthalmological Institute, Oviedo, Spain.

DESIGN

Prospective, single-center, clinical study.

METHODS

Included were patients who underwent ICRS implantation for KC over a period of 1 year. On the day of the surgery and at least 6 months after ICRS implantation, the following measurements were made: corrected distance and uncorrected distance visual acuity, corneal tomography indices with the Pentacam, biomechanically corrected intraocular pressure and the Corvis DCRs (integrated inverse concave radius, deformation amplitude ratio, stiffness parameter at first applanation, stress-strain index [SSI] and the highest concavity radius).

RESULTS

30 eyes were included with a mean follow-up time of 15 months. Statistical analysis showed that ICRS implantation induced significant improvements in corneal biomechanics measurements between preoperative and long-term follow-up as demonstrated by a significant increase in SSI (P = .003). To confirm that this difference was actually induced due to a stiffening between early postoperative (previously published) and long-term an additional t-test was done between month 1 and late follow-up which confirmed a significant stiffening in the value of SSI (P = .01).

CONCLUSIONS

Patients implanted with ICRS alone for KC showed a significantly stiffer response due to increased structural support compared with preoperative values and 1 month postoperative.

Corneal Collagen Cross-Linking for Progressive Keratoconus in Pediatric Patients: Up to 14 Years of Follow-up

PURPOSE

To assess the long-term outcomes of corneal collagen cross-linking according to the Dresden protocol (S-CXL) in progressive pediatric keratoconus (KC).

DESIGN

Retrospective, single-center noncomparative interventional study.

METHODS

Patients aged <18 years who underwent S-CXL from June 2007 to January 2011 in Humanitas Clinical and Research Center, Rozzano, Milan, Italy, and completed at least 10 years of follow-up were included. Corrected distance visual acuity (CDVA), refraction, and tomography were evaluated at baseline and ≥10 years after S-CXL. Meeting 2 of the following 3 criteria indicated reprogression: progression above 95% CI for post-CXL population of A or B values or a decrease in minimal thickness C evaluated with the ABCD display.

RESULTS

Thirty-eight eyes of 24 patients fulfilled inclusion criteria. At a mean of 11.6 years postoperation (maximum 14 years), the CDVA improved significantly (from 0.703 ± 0.33 decimal fraction to 0.887 ± 0.2, P < .001). Similarly, the A value significantly improved from 2.550 ± 1.7 to 1.627 ± 1.68 (P = .019). Thirteen eyes (34%) showed significant postoperative progression in 2 of the 3 parameters A, B, and C. Of these, only 3 eyes (7.9%) of 3 patients showed a statistically significant change in the A value.

CONCLUSIONS

S-CXL proved to be a safe treatment for progressive KC in pediatric patients with an anterior curvature progression rate of up to 7.9% at ≥10 years of follow-up.

Evaluation of Biomechanical Changes After Accelerated Cross-Linking in Progressive Keratoconus: A Prospective Follow-Up Study

PURPOSE

The aim of this study was to analyze the biomechanical effect of accelerated corneal cross-linking (9*10) in progressive keratoconus (KC) in comparison to untreated fellow eyes using Scheimpflug-based tonometry (Corvis ST, CVS).

METHODS

Forty-three eyes of 43 patients with KC showed progressive KC and were treated using accelerated corneal cross-linking. Twenty-five untreated fellow eyes were used as the control group. All eyes were examined biomechanically (CVS) and tomographically (Pentacam) at baseline, after 1-month, 6-month, and 12-month follow-up. Statistical analysis was performed using a linear mixed model. A logistic regression was performed to attribute the effects of changes in each parameter to treatment status (treated or untreated).

RESULTS

Maximum keratometry values decreased statistically significantly at 12 months by -1.1 D (95 confidence interval: -2.0 to -0.1, P = 0.025) compared with baseline. Thinnest corneal thickness decreased significantly after 1 month ( P < 0.001) and recovered to baseline after 12 months ( P = 0.752). In the corneal cross-linking (CXL) group, biomechanical changes were observed by an increased bIOP, a shorter A2 time, and a lower integrated radius after 1 month (all P < 0.05). No biomechanical and tomographical changes were observed in the control group (all P > 0.05). Logistic regression pointed out that treated eyes can be separated from untreated eyes by differences in bIOP, corneal thickness, A1 velocity, integrated radius, and Kc mean at 1, 6, and 12 months.

CONCLUSIONS

The alterations in biomechanical parameters indicated a corneal stiffening effect after CXL treatment, which was mostly detectable 1 month after treatment, although corneal thickness was reduced. The logistic regression model showed an adequate separation between CXL-treated and untreated eyes.

Effects of femtosecond laser-assisted minimally invasive lamellar keratoplasty (FL-MILK) on mild-to-moderate and advanced keratoconus

PURPOSE

To compare the outcomes of femtosecond laser-assisted minimally invasive lamellar keratoplasty (FL-MILK) for mild-to-moderate keratoconus (KC) and advanced KC.

METHODS

Prospective case series study. Sixty-three eyes of 56 patients with progressive KC underwent FL-MILK were divided into group 1 [mean keratometry (Kmean) ≤ 53D] and group 2 (Kmean > 53D). Best spectacle-corrected visual acuity (BSCVA), Kmean, maximum keratometry (Kmax), anterior central corneal elevation (ACE), stiffness parameter A1 (SP-A1) and deformation amplitude (DA) were evaluated preoperatively and up to 24 months postoperatively.

RESULTS

Mean BSCVA improved from 0.34 ± 0.13 logMAR preoperatively to 0.25 ± 0.13 logMAR at 24 months postoperatively in group 1 (F = 10.10, P < .0001), and from 0.54 ± 0.31 logMAR to 0.40 ± 0.26 logMAR (F = 9.06, P = .0002) in group 2. Group 2 showed an average Kmax reduction of 10.9 D and an average Kmean reduction of 3.9 D at 24 months postoperatively (both P < .0001), whereas no significant change was observed in group 1. Average ACE decreased from 19.2 ± 10.0 to 5.2 ± 8.4 at 24 months postoperatively in group 1 (F = 28.5, P < .0001), and from 46.2 ± 16.3 to 19.1 ± 9.0 (F = 49.6, P < .0001) in group 2; SP-A1 increased from 53.8 ± 12.7 mmHg/mm to 95.9 ± 20.2 mmHg/mm in group 1 (F = 70.0, P < .0001), and from 38.6 ± 13.4 mmHg/mm to 89.3 ± 18.2 mmHg/mm (F = 96.9, P < .0001) in group 2; DA decreased from 1.30 ± 0.14 mm to 1.17 ± 0.13 mm in group 1 (F = 14.0, P < .0001), and from 1.40 ± 0.16 mm to 1.18 ± 0.10 mm (F = 27.6, P < .0001) in group 2.

CONCLUSIONS

FL-MILK can stabilize progressive KC in mild-to-moderate cases and advanced cases at 24-month follow-up. Steeper corneas are more likely to undergo flattening after FL-MILK.

CLINICAL TRIAL

Date of registration: July 16, 2017. The title of the trail: www.

CLINICALTRIALS

gov Trial registration number: NCT03229239. The name of the trial registry: ClinicalTrials.gov.

Network meta-analysis comparing efficacy and safety of different protocols of corneal cross-linking for the treatment of progressive keratoconus

PURPOSE

This study aimed to determine the preferred protocol of corneal collagen cross-linking (CXL) in the treatment of progressive keratoconus.

METHODS

Relevant studies were retrieved in PubMed, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL). Maximum keratometry value (Kmax), best spectacle-corrected visual acuity (BSCVA), manifest refraction spherical equivalent (MRSE), and endothelial cell density (ECD) were evaluated in network meta-analysis.

RESULTS

Eight randomized controlled trials (RCTs) were included. Low-level evidence suggested that aCXL with 30mW/cm2 for 3 min (aCXL-3) might be the best protocol for reducing BSCVA (65.22%) but worst protocol for reducing MRSE (51.53%). aCXL with 18mW/cm2 for 5 min (aCXL-5) might be the best protocol for reducing Kmax (39.58%) and MRSE (77.85%) but might be the worst for preserving ECD (50.98%). aCXL with 9mW/cm2 for 10 min (aCXL-10) might be the best protocol for preserving ECD (31.53%).

CONCLUSION

Overall, three protocols of aCXL are comparable in therapeutic efficacy and safety for treating progressive keratoconus. Despite no direct data comparing the efficacy of each technique according to different patients' profiles, it is reasonable to state that aCXL-5 may be the best for patients at early-stage to reduce Kmax and MRSE, aCXL-3 may be the best for patients at mid-stage to improve BSCVA, and aCXL-10 may be the best for patients at late-stage to preserve DEC.

Rate of fractional change in corneal tomography parameters in keratoconus using a combination of predictive parameters

BACKGROUND

To compare the rate of fractional change for multiple corneal tomographic factors in progressive keratoconus (KC).

METHODS

In this retrospective case series, 40 eyes (40 patients) with progressive KC (increase in central keratometry of 1.00 D or maximum keratometry of 1.50 D on two visits at least six months apart) were included. Cases with previous history of ocular surgery, poor scans, corneal scars, severe dry eyes, post-excimer ectasia, pellucid marginal degeneration were excluded. Medical records, corneal tomography and anterior corneal wavefront (8 mm) (Scheimpflug tomography, Pentacam, Oculus, Germany) were analyzed. Rate of fractional change (Rx = (x1 - x0)/(|x0|tm)); where, x1 = value at follow-up, x0 = value at initial visit and tm = time in months, was measured.

RESULTS

The mean age of the patients was 30.0 ± 8.4 years. The mean follow-up duration was 8.9 ± 4.2 months. Coma (0.076 ± 1.4) had the largest rate of fractional change (P = 1.7 × 10-14, Kruskal-Wallis test). The rate of fractional change was higher for aberrometric parameters (anterior corneal higher-order aberrations root mean square and anterior coma) compared to pachymetric and keratometric parameters (P values ranging from 1.4 × 10-4 to 7.4 × 10-10, Mann-Whitney test, effect size ranging from 0.4-0.7). The rate of fractional change was comparable between pachymetric and keratometric factors (P > 0.05 for all comparisons, Mann-Whitney test).

CONCLUSIONS

Anterior corneal wavefront, especially anterior coma, were noted to have higher rate of fractional change compared to single point keratometric and pachymetric indices in progressive KC. This information can be used for decision-making when monitoring patients with KC.

Three-years outcomes of simultaneous photorefractive surgery and customized corneal cross-linking for keratoconus

PURPOSE

To report the efficacy of customized cross-linking (CXL) in halting progression of keratoconus when combined with photorefractive procedures.

METHODS

Seven eyes from 7 patients with documented progressive keratoconus were treated with customized CXL (customized ultraviolet-A irradiance pattern centered on the maximum posterior elevation with total energy levels ranging from 5.4 up to 10 J/cm2 , and an energy fluence of 9 mW/cm2) combined with photorefractive procedures. Four patients underwent simultaneous transepithelial photorefractive keratectomy (T-PRK) plus customized CXL, and three patients underwent simultaneous transepithelial phototherapeutic keratectomy (T-PTK) plus customized CXL. Tomographic parameters (Kmax, pachymetry of the thinnest point and maximal elevation of posterior float and regularization index) and best spectacle-corrected visual acuity (BSCVA) were compared preoperatively and 3 years postoperatively.

RESULTS

All eyes showed a decrease in the maximal curvature Kmax, and none of eyes showed progression. Six eyes showed a flattening of 3 or more diopters (D). On average, Kmax decreased by - 4.8 ± 2.5 D, and the BSCVA improved by 0.04 ± 0.07 logarithm of the minimal angle of resolution. The mean value of regularization index was 8.7 ± 3.8 D. Mild corneal haze occurred in two eyes, and superficial apical scar occurred in one eye. None of the eyes had a vision-threatening complication.

CONCLUSION

Customized CXL combined with photorefractive procedure (T-PRK/T-PTK) resulted in long lasting flattening effect and strong regularization of keratoconic corneas along with improvement of BSCVA over a 3-year follow-up.

Development and validation to predict visual acuity and keratometry two years after corneal crosslinking with progressive keratoconus by machine learning

Purpose

To explore and validate the utility of machine learning (ML) methods using a limited sample size to predict changes in visual acuity and keratometry 2 years following corneal crosslinking (CXL) for progressive keratoconus.

Methods

The study included all consecutive patients with progressive keratoconus who underwent CXL from July 2014 to December 2020, with a 2 year follow-up period before July 2022 to develop the model. Variables collected included patient demographics, visual acuity, spherical equivalence, and Pentacam parameters. Available case data were divided into training and testing data sets. Three ML models were evaluated based on their performance in predicting case corrected distance visual acuity (CDVA) and maximum keratometry (Kmax) changes compared to actual values, as indicated by average root mean squared error (RMSE) and R-squared (R2) values. Patients followed from July 2022 to December 2022 were included in the validation set.

Results

A total of 277 eyes from 195 patients were included in training and testing sets and 43 eyes from 35 patients were included in the validation set. The baseline CDVA (26.7%) and the ratio of steep keratometry to flat keratometry (K2/K1; 13.8%) were closely associated with case CDVA changes. The baseline ratio of Kmax to mean keratometry (Kmax/Kmean; 20.9%) was closely associated with case Kmax changes. Using these metrics, the best-performing ML model was XGBoost, which produced predicted values closest to the actual values for both CDVA and Kmax changes in testing set (R2 = 0.9993 and 0.9888) and validation set (R2 = 0.8956 and 0.8382).

Conclusion

Application of a ML approach using XGBoost, and incorporation of identifiable parameters, considerably improved variation prediction accuracy of both CDVA and Kmax 2 years after CXL for treatment of progressive keratoconus.

Management of keratoconus: an updated review

Keratoconus is the most common corneal ectatic disorder. It is characterized by progressive corneal thinning with resultant irregular astigmatism and myopia. Its prevalence has been estimated at 1:375 to 1:2,000 people globally, with a considerably higher rate in the younger populations. Over the past two decades, there was a paradigm shift in the management of keratoconus. The treatment has expanded significantly from conservative management (e.g., spectacles and contact lenses wear) and penetrating keratoplasty to many other therapeutic and refractive modalities, including corneal cross-linking (with various protocols/techniques), combined CXL-keratorefractive surgeries, intracorneal ring segments, anterior lamellar keratoplasty, and more recently, Bowman's layer transplantation, stromal keratophakia, and stromal regeneration. Several recent large genome-wide association studies (GWAS) have identified important genetic mutations relevant to keratoconus, facilitating the development of potential gene therapy targeting keratoconus and halting the disease progression. In addition, attempts have been made to leverage the power of artificial intelligence-assisted algorithms in enabling earlier detection and progression prediction in keratoconus. In this review, we provide a comprehensive overview of the current and emerging treatment of keratoconus and propose a treatment algorithm for systematically guiding the management of this common clinical entity.

Characterization of the Immediate and Delayed Biomechanical Response to UV-A Crosslinking of Human Corneas

PURPOSE

Keratoconus leads to visual deterioration due to irregular astigmatism and corneal thinning. Riboflavin-based corneal UV-A crosslinking (CXL) induces novel intramolecular and intermolecular links resulting in corneal tissue stiffening, thereby halting disease progression. The purpose of this study was to analyze the immediate and delayed biomechanical responses of human donor corneas to CXL.

METHODS

CXL was performed according to the Dresden protocol to corneas not suitable for transplantation. Biomechanical properties were subsequently monitored by measuring the Young modulus using nanoindentation. The immediate tissue response was determined after 0, 1, 15, and 30 minutes of irradiation. Delayed biomechanical effects were investigated with follow-up measurements immediately and 1, 3, and 7 days after CXL.

RESULTS

Young's modulus indicated a linear trend in direct response to increasing irradiation times (mean values: total 61.31 kPa [SD 25.53], 0 minutes 48.82 kPa [SD 19.73], 1 minute 53.44 kPa [SD 25.95], 15 minutes 63.56 kPa [SD 20.99], and 30 minutes 76.76 kPa [SD 24.92]). The linear mixed model for the elastic response of corneal tissue was 49.82 kPa + (0.91 kPa/min × time [minutes]); P < 0.001. The follow-up measurements showed no significant delayed changes in the Young modulus (mean values: total 55,28 kPa [SD 15.95], immediately after CXL 56,83 kPa [SD 18.74], day 1 50.28 kPa [SD 14.15], day 3 57.08 kPa [SD 14.98], and day 7 56.83 kPa [SD 15.07]).

CONCLUSIONS

This study suggests a linear increase of corneal Young modulus as a function of CXL timing. No significant short-term delayed biomechanical changes posttreatment were observed.

Predictive accuracy of the ABCD progression display among patients with keratoconus: A historic cohort analysis

OBJECTIVE

To evaluate the accuracy of the ABCD Progression Display and the ABCD grading system in a population of adult patients with keratoconus.

METHODS

A retrospective cohort analysis of all adult patients with keratoconus followed at the Shamir Medical Center between 2012 and 2017. A recommendation by the cornea specialist to undergo corneal crosslinking (CXL) was used as a surrogate of ectasia progression. The ABCD grading was not available to the treating physician and was computed post-hoc. Sensitivity and specificity of the ABCD Progression Display was calculated, and multivariate regression was used to estimate the risk to undergo CXL when the ABCD Progression Display indicated progression. The ABCD grading was compared between patients who required CXL to those who did not. A single eye of each patient was included. Sensitivity and specificity of the ABCD Progression Display were 82% and 73%, respectively. A multivariable model adjusted for possible confounders, found that ABCD Progression was associated with a 7-fold risk of undergoing CXL compared to a patient in whom progression was not recorded in the ABCD Progression Display (OR = 7.55; 95% CI = 3.82-14.93, p < 0.001).

RESULTS

293 eyes of 293 patients were analysed. Mean age at presentation was 26.92 ± 6.12 years. In 68 eyes, progression of keratoconus was recorded and CXL was performed (CXL-group).

CONCLUSION

The ABCD Progression Display demonstrated adequate sensitivity and specificity and high predictive capabilities of keratoconus progression. It can be effectively utilized as an initial screening test in adults with keratoconus.

Customized corneal crosslinking with excimer laser-assisted epithelium removal for progressive keratoconus: 1-year results

PURPOSE

To evaluate the 1-year visual and tomographic results of customized crosslinking using excimer laser-assisted epithelium removal and topography-guided irradiation in the treatment of progressive keratoconus.

SETTING

Coimbra Ophthalmology Unit, Private Practice, Coimbra, Portugal.

DESIGN

Prospective nonrandomized clinical trial.

METHODS

Eyes with documented progressive keratoconus were enrolled. After de-epithelialization with phototherapeutic keratectomy, customized UV irradiation was performed, designed as 3 concentric circular areas centered on the thinnest point (Mosaic System). Energy exposure was 5.4 J/cm 2 in the outer circle and then increased centripetally to 7.2 J/cm 2 and 10 J/cm 2 . Corrected distance visual acuity (CDVA), refractive outcomes, and Scheimpflug tomographies (Allegro Oculyzer) were assessed at baseline, and 6 months, and 12 months postoperatively.

RESULTS

37 eyes of 32 patients were enrolled in this prospective study. The mean diameter for treated areas was 6.17 ± 0.80 mm, 4.45 ± 0.47 mm, and 2.58 ± 0.14 mm for the outer, medium, and inner circle, respectively. At the 1-year follow-up, the mean CDVA improved significantly from 0.38 ± 0.19 to 0.20 ± 0.16 logMAR ( P < .01), with 34 (91.89%) of the 37 eyes retaining or improving CDVA. The mean preoperative minimum pachymetry decreased from 449.26 ± 41.62 to 443.26 ± 41.06 μm ( P = .02). The maximum keratometry decreased significantly from 58.50 ± 7.84 to 57.05 ± 7.27 diopters ( P < .01). After 1 year, 34 eyes (91.89%) showed no signs of progression.

CONCLUSIONS

1 year postoperatively, patients showed a significant improvement in visual acuity while achieving stabilization of disease progression.

Medium to long term follow up study of the efficacy of cessation of eye-rubbing to halt progression of keratoconus

Purpose

To study the progression of keratoconus after cessation of eye rubbing with a minimum follow up of three-years.

Design

Retrospective, monocentric, longitudinal cohort study of keratoconus patients with a minimum of 3 years follow-up.

Participants

One hundred fifty three eyes of seventy-seven consecutive patients with keratoconus were included.

Methods

Initial examination consisted of anterior and posterior segment evaluation using slit-lamp biomicroscopy. At the initial visit, patients were thoroughly informed of their pathology and instructed to stop rubbing their eyes. Eye rubbing cessation was assessed at all the follow-up visits at 6 months, 1 year, 2 years, 3 years, and yearly afterward. Corneal topography using the Pentacam® (Oculus®, Wetzlar, Germany) was used to obtain maximum and average anterior keratometry readings (Kmax and Kmean), as well as thinnest pachymetry (Pachymin, μm) in both eyes.

Main outcome measures

The main outcomes measured were maximum keratometry (Kmax), mean keratometry (Kmean), and thinnest pachymetry (Pachymin) values at various time points to assess for keratoconus progression. Keratoconus progression was defined as a significant augmentation of Kmax (>1D), Kmean (>1D), or significant diminution of Pachymin (>5%) throughout the total follow-up duration.

Results

One hundred fifty three eyes of seventy-seven patients (75.3% males) aged 26.4 years old, were followed for an average of 53 months. Over the course of the follow-up, there was no statistically significant variation of ∆Kmax (+0.04 ± 0.87; p = 0.34), ∆ Kmean (+0.30 ± 0.67; p = 0.27) nor ∆Pachymin (-4.36 ± 11.88; p = 0.64). Among the 26 of the 153 eyes which had at least one criterion of KC progression, 25 admitted continuing eye rubbing, or other at-risk behaviors.

Conclusion

This study suggests that a significant proportion of keratoconus patients are likely to remain stable if close monitoring and strict ARB cessation are achieved, without the need for further intervention.

Determination of efficacy of repeated CXL and probable risk factors in patients with progressive keratoconus

PURPOSE

To evaluate the efficacy of Repeated CXL (Re-CXL) and determine probable risk factors that lead to Re-CXL in patients with progressive keratoconus.

METHOD

In this retrospective study, the medical records of patients who had been re-operated in our center between 2014 to 2020 due to progressive keratoconus were evaluated; seven eyes of seven patients had undergone Re-CXL procedure. Pre- and post-treatment variables were recorded and analyzed using IBM SPSS Statistics software.

RESULTS

The mean interval between the 1st and 2nd CXL was 49.71 months (range 12-72 months). Out of 7 patients for whom Re-CXL was considered necessary, eye rubbing was detected in 6 patients. Six patients were very young with a mean age of 13 years at primary CXL and 16.83 years at Re-CXL. Visual acuity and astigmatism did not change significantly after the Re-CXL procedure (p-values = 0.18, 0.91, respectively). When measurements of these indices prior to Re-CXL and post Re-CXL were compared, K1 (p-value = 0.01), K2 (p-value = 0.01), Kmean (p-value = 0.01), and Kmax (p-value = 0.008) changed significantly. As to pachymetry (p-value = 0.46), it did not change significantly. Kmax value regressed in all eyes after Re-CXL.

CONCLUSION

Re-CXL procedure was effective in halting the progression of disease. As to the risk factors, eye rubbed-related mechanism like eye rubbing and VKC, lower age, and pre-operative Kmax value > 58 D are the risk factors of Re-CXL procedure.

[Keratoconus: biomechanics ex vivo]

BACKGROUND

Keratoconus is associated with an impairment in corneal biomechanics. Using nanoindentation, spatially resolved measurement of biomechanical properties can be performed on corneal tissue. The aim of this study is to assess the biomechanical properties of corneas with keratoconus in comparison to healthy controls.

METHODS

17 corneas with keratoconus and 10 healthy corneas unsuitable for transplantation were included in the study. After explantation, corneas were kept in culture medium containing 15% dextran for at least 24 h. Nanoindentation was then performed to a depth of 25 µm at a force increase of 300 µN/min.

RESULTS

A total of 2328 individual indentations were performed for this study. In the keratoconus group; the mean modulus of elasticity was 23.2 kPa (± 15.0 kPa) for a total of 1802 indentations. In the control group, the mean modulus of elasticity was 48.7 kPa (± 20.5 kPa) with a total of 526 indentations. The Wilcoxon test showed that the differences were statistically significant.

CONCLUSION

Using nanoindentation, a significantly lower elastic modulus was found in corneas with keratoconus compared to corneas without keratoconus. Further studies are needed to gain a better understanding of how keratoconus affects corneal biomechanics.

Outcomes of accelerated collagen cross linking in progressive paediatric keratoconus

Purpose

To determine the efficacy and safety of pediatric accelerated cross linking (CXL).

Methods

A prospective study on progressive keratoconus (KC) cases under ≤18 years of age. Sixty four eyes of thirty nine cases underwent epithelium-off accelerated CXL protocol. Visual acuity (VA), slit-lamp examination, refraction, pentacam reading of keratometry (K), corneal thickness, and thinnest location pachymetry were noted. Cases were followed up on days 1, 5, and at 1^st, 3^rd, 6^th, and 12th-month post procedure.

Results

Statistically, significant improvement of the mean aided VA, K, and mean corneal astigmatism (p < 0.0001) was noted. Mean Kmax reading reduced from 55.5 ± 5.64 (47.4-70.4) diopter (D) preoperatively to 54.41 ± 5.51 (46-68.3) D at 12 months postaccelerated CXL. Two cases had progression. Complications encountered were sterile infiltrate and persistent haze.

Conclusion

Accelerated CXL is effective and efficacious in pediatric KC.

Repeatability of corneal deformation response parameters by dynamic ultra-high-speed Scheimpflug imaging before and after corneal crosslinking

PURPOSE

To evaluate the repeatability of deformation corneal response (DCR) parameters before and after corneal crosslinking (CXL) compared with their untreated fellow eyes (uFEs).

SETTING

University Hospital Carl Gustav Carus, Dresden, Germany; IRCCS Humanitas Research Hospital, Rozzano, Milan, Italy.

DESIGN

Multicenter, interventional reliability analysis.

METHODS

53 eyes of 53 patients with keratoconus who received CXL treatment after the disease progression (CXL group) were included. Patients were measured 3 times using a dynamic Scheimpflug analyzer to determine repeatability before and 1 month after CXL treatment. The uFEs were measured in the same way (uFE group). Reliability of DCR parameters was assessed by a coefficient of repeatability, coefficient of variation, and intraclass correlation coefficient (ICC).

RESULTS

The repeatability of DCR parameters did not change after CXL compared with the preoperative values for all investigated DCR parameters ( P > .05). In the uFE group, no statistically significant shift was observed regarding the repeatability ( P > .05). An ICC greater than 0.75 was achieved in both groups for almost all parameters. Concerning the biomechanical stiffening induced by CXL, integrated inverse radius and stress-strain index were found to be statistically significantly decreased and increased ( P < .001), respectively, both indicating stiffening. No changes were observed for the uFE group.

CONCLUSIONS

The study demonstrated highly repeatable measurements of the dynamic Scheimpflug analyzer before and after CXL. The improvement of certain DCR parameters after CXL confirmed the capability of the device to detect the stiffening effect.

Detecting True Change in Keratoconus after Intracorneal Ring Segment Implantation

Confirming the progression of keratoconus is of paramount relevance to providing the appropriate treatment. Real change should be considered consistent over time. It must be greater than the variability of the measurement of the device used to monitor the cornea. The present study aimed to assess the intraobserver repeatability and intersession reproducibility of a Scheimpflug camera in measuring corneal parameters in virgin keratoconus and intrastromal corneal ring segments (ICRS) implantation eyes to discriminate real change from measurement noise. Sixty keratoconus and 30 ICRS eyes were included. Corneal parameters were determined in three consecutive measurements and were repeated 2 weeks later. The precision within the same session for all parameters was better in the keratoconic eyes, with mean repeatability limits 33% narrower (range 13% to 55%) compared with ICRS eyes. Mean reproducibility limits were 16% narrower (range +48% to -45%) compared with ICRS eyes. The cutoff values to consider a real corneal shape change were lower for virgin keratoconic than for ICRS, except for the thinnest corneal thickness and Stage C (ABCD system), which were the opposite. Corneal tomography measurements in ICRS eyes showed worse accuracy than in virgin keratoconus, which should be taken into account by practitioners in patients' follow up.

Natural history and predictors for progression in pediatric keratoconus

We studied the demographic and clinical predictors associated with keratoconus progression in a pediatric population. Retrospective cohort study. We evaluated 305 eyes without previous surgeries from 168 patients, 9 to < 18 years old, and with a minimum 36-month follow-up in a hospital corneal ambulatory. We used Kaplan-Meyer survival curves; the dependent variable (main outcome measure) was the interval time (months) until the event, defined as an increase of 1.5 D in the maximum keratometry (Kmax), obtained with Pentacam. We evaluated the predictors: age (< or ≥ 14 years), sex, keratoconus familial history, allergy medical history, and the baseline tomographic parameters: mean keratometry (Km), Kmax (< or ≥ 55 D); and thinnest pachymetry (TP). We used log-rank tests and compared median survival times for right (RE)/left eyes (LE) and better (BE)/worse eyes (WE). A p value < 0.05 was considered significant. The patients' mean ± SD age was 15.1 ± 2.3 years old; 67% were boys, 30% were < 14 years, 15% had keratoconus familial history, and 70% were allergic. The general Kaplan-Meyer curves showed no differences between RE/LE or BE/WE. RE with allergy and LE with Kmax ≥ 55 D had smaller survival times ((95%CI 9.67-32.1), p 0.031 and (95%CI 10.1-44.1), p 0.042, respectively). For BE and WE, Kmax ≥ 55 D had smaller survival times ((95% CI 6.42- ), p 0.031 and (95%CI 8.75-31.8), p 0.043, respectively). Keratoconus progression was similar between RE/LE and BE/WE. Steepest corneas are predictors of faster progression. Allergy is also a predictor of keratoconus progression in RE.

Innovations in Corneal Crosslinking

PURPOSE

Corneal Crosslinking (CXL) strengthens the keratoconus cornea and prevents further disease progression. Modified crosslinking protocols and different riboflavin solutions have been proposed to optimize the procedure and improve treatment success.

METHODS

PubMed research of relevant publications and report of own experiences with different CXL protocols.

RESULTS

Accelerated CXL shows comparable efficiency with shorter surgery time and similar complication rates. Customized CXL provides improved results with faster epithelial healing. CXL in a hyperoxic environment seems to be a safe and effective transepithelial alternative with presumably less complications and fewer side effects. Thin corneas (<400 µm) can be treated safely by corneal swelling using hypoosmolar riboflavin solutions and reducing the applied UV-energy. The combination of CXL with photorefractive keratectomy (PRK) can be considered in patients with contact lens intolerance improving visual acuity, however, with increased risk of visual loss compared to CXL alone. Two-Photon (2Ph) CXL is a promising new technology enabling three-dimensional CXL.

DISCUSSION

Recently developed CXL protocols offer advantages over the standard "Dresden-protocol" and should be considered in patients with progressive keratectasia.

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.

Corneal Crosslinking With Riboflavin and UVA Light in Progressive Keratoconus: Fifteen-Year Results

PURPOSE

To analyze the 15-year results of corneal crosslinking (CXL) in progressive keratoconus.

DESIGN

Retrospective follow-up analysis of interventional study patients.

METHODS

This study included keratoconic eyes with progressive disease treated from 2001 to 2006 at the Department of Ophthalmology, Carl Gustav Carus University Hospital, TU Dresden, Germany. CXL was performed by applying riboflavin and ultraviolet A (UVA) light according to a standard protocol. The best-corrected distance visual acuity (BCVA), slitlamp examination, and corneal topography as well as corneal thickness values were recorded preoperatively and 15 years after the treatment.

RESULTS

A total of 42 eyes received a complete follow-up of 15 years. The mean age of the patients at baseline was 26.9 (95% CI: 25.0-28.8) years. The maximum keratometry was 61.6 (95% CI: 58.2 - 64.9) diopters (D) preoperatively and 55.1 (95% CI: 51.6-58.4) D postoperatively; the decrease was statistically significant (P < .001). The mean keratometry value changed from 50.3 (95% CI: 48.3-52.4) D to 47.5 (95% CI: 45.3-49.4) D (P < 0.001). Furthermore, the thinnest corneal thickness decreased statistically significantly by 40 (95% CI: 24-56) µm (P < .001). The BCVA improved statistically significantly from 0.4 to 0.2 logMAR after the treatment. Retreatment was needed in 14% of cases. Mild scarring of the superficial stromal corneal layers was observed in 36% of the eyes, and in 67% of them visual acuity was stable or even improved.

CONCLUSIONS

The CXL procedure proved to be an effective method in the treatment of keratoconic eyes in the progressive stage of the disease, and achieved long-term stabilization without the occurrence of serious complications or side effects.

Long-term Safety and Efficacy of Corneal Collagen Crosslinking in a Pediatric Group With Progressive Keratoconus: A 7-year Follow-up

PURPOSE

To assess effectiveness and safety of corneal crosslinking (CXL) to reduce keratoconus (KC) progression and improve visual acuity among children with progressive KC and to analyze the use of 20% dextran-based (Dextran) and 1% hydroxypropyl methylcellulose-based (HPMC) riboflavin.

DESIGN

Prospective, clinical cohort study METHODS: Standard CXL (SCXL) was performed in 74 eyes (58 patients, 45 males, mean age 13.0 ± 2.1 years): 53 eyes with HPMC and 21 with Dextran. Examinations were performed at baseline, 3 and 6 months, and 1, 2, 3, 4, 5, and 7 years of follow-up, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), a complete ophthalmologic examination, anterior segment ocular coherence tomography, Scheimpflug corneal tomography, and specular microscopy.

RESULTS

UDVA and CDVA improved at all periods with statistically significant differences in CDVA at 1, 2, and 3 years. Compared with baseline, maximum K (Max K) reduced throughout the 7-year follow-up. Mean thinnest pachymetry (Th Pachy) decreased significantly at 3 months and remained low; in the Dextran group, the Th Pachy mean value returned to baseline 6 months postoperatively. After CXL, 1.5 diopter progression in max K was 1.4% to 14.6% of eyes; worsening was found at 4 to 7 years postoperatively.

CONCLUSION

SCXL reduced KC progression in children up to 7 years of follow-up and revealed improvement and stability of UDVA and CDVA in 82% of eyes. For visual acuity and KC stability, no statistically significant difference was observed between Dextran-HPMC. The HPMC group showed persistent cornea thinning, raising concerns about its use in SCXL.

Five-year corneal cross-linking outcomes: A Save Sight Keratoconus Registry Study

BACKGROUND

We aimed to determine the long-term outcomes of epithelium-off cross-linking (CXL) in keratoconus patients.

METHODS

An observational registry study from 41 centres across 5 countries was carried out. Primary outcomes included the mean change in visual acuity (VA), Kmax, K2, and thinnest corneal thickness (TCT) at 1-5 years. Secondary outcomes included the percentage of eyes with worsening, stable and improving outcomes.

RESULTS

There were 976 eyes of 794 patients with 1-year of complete follow-up, 501 eyes with 2-years, 355 with 3-years, 235 with 4-years and 162 with 5-years. There was a significant improvement in mean VA from baseline by 3.7 logMAR letters (p < 0.001) in year 1, and 6.9 (p < 0.001) in year 5. Mean Kmax decreased by 1.2 dioptres (D; p < 0.01) in year 1. During subsequent years the Kmax flattening appeared sustained but this was not statistically significant. K2 flattened significantly from baseline in year 1 and then remained stable. At 1 year, 4.1% patients were poor responders to CXL in terms of VA, losing ≥15 letters. The proportion of the poor responders remained unchanged: 4.9% at 5-years. The proportion of poor responders in terms of Kmax remained similar: 5.9% steepening by ≥2D at 1-year and 7.5% at 5-years. The proportion of K2 poor responders remained stable with 4.7% steepening by ≥2D at 1-year and 5.8% at 5-years.

CONCLUSIONS

Cross-linking is effective at stabilising keratoconus up to 5 years in most patients. However, a small proportion of eyes failed to stabilise and had reduced vision.

Prospective, Randomized, Multicenter, Double-Masked, Clinical Trial of Corneal Cross-Linking for Boston Keratoprosthesis Carrier Tissue

PURPOSE

To assess whether cross-linking the carrier donor cornea of the Boston Keratoprosthesis (BKPro) improves retention of the device in participants at high risk for keratolysis.

DESIGN

Prospective, double-masked, randomized clinical trial.

METHODS

In this multicenter study, 68 adult participants who were scheduled for BKPro implantation were enrolled. Masked participants were randomized to receive either a cross-linked (CXL) or non-cross-linked (non-CXL) donor corneal carrier. The Kaplan-Meier event-free survival was determined by the product-limit method and compared by the log-rank test to examine whether survival curves were different between the CXL and non-CXL groups. The primary outcome of the study was time from surgery to BKPro removal. The secondary endpoint was 12-month retention rate.

RESULTS

A total of 68 participants were enrolled and randomized 1:1 to each group. The average age at the time of surgery was 62 (range = 24-89) years, and 42 participants (62%) were male. The overall BKPro retention rate was 70% during a mean follow-up time of 93 (range = 6-201) weeks. Twenty BKPros were removed, 10 in the CXL group and 10 in the non-CXL group, with 18 requiring removal because of sterile keratolysis. There was no difference in the time to removal between the groups during the study (P = .910). At 12 months, there was no significant difference in the retention rate in the CXL group (94%) vs the non-CXL group (82%, P = .150).

CONCLUSIONS

In this prospective study, cross-linking of the carrier cornea prior to BKPro implantation did not reduce the incidence of sterile keratolysis or increase device retention among participants at high risk for retention failure.

Best Fit Sphere Back and Adjusted Maximum Elevation of Corneal Back Surface as Novel Predictors of Keratoconus Progression

Purpose

We evaluated the Maximum Elevation of Corneal Back Surface adjusted to the same Best Fit Sphere Back (BFSB) between timeline measurements (AdjEleBmax) and the BFSB radius (BFSBR) itself as new tomographic parameters for documentation of ectasia progression and compare them with the most recent and reliable parameters used on keratoconus (KC) progression.

Results

We evaluated the performance and the ideal cutoff point of Kmax, D-index, posterior radius of curvature from the 3.0 mm centered on the thinnest point (PRC), EleBmax, BFSBR, and AdjEleBmax as isolated parameters to document KC progression (defined as a significant change in two or more variables), we found a sensitivity of 70%, 82%, 79%, 65%, 51%, and 63% and a specificity of 91%, 98%, 80%, 73%, 80%, and 84% to detect KC progression. The area under the curve (AUC) for each variable was 0.822, 0.927, 0.844, 0.690, 0.695, 0.754, respectively.

Conclusion

AdjEleBmax presented a greater specificity, larger AUC, and better performance compared to EleBmax without any adjustment, with similar sensitivity. Although AdjEleBmax and BFSB demonstrated smaller AUC and specificities comparing with Kmax and D-Index, AdjEleBmax still presented a good performance with a reasonable AUC. Since the shape of the posterior surface, more aspheric and curved than the anterior, may facilitate detection of change, we suggest the inclusion of AdjEleBmax in the evaluation of KC progression in conjunction with other variables to increase the reliability of our clinical evaluation and early detection of progression.

Long-Term Outcome of Corneal Collagen Crosslinking with Riboflavin and UV-A Irradiation for Keratoconus

PURPOSE

To evaluate long-term outcomes of corneal collagen crosslinking (CXL) using riboflavin and UV-A irradiation and to determine when to repeat CXL.

METHODS

In this retrospective consecutive interventional case series 131 eyes of 131 patients (95 male, 36 female, mean age 29.7 ± 11.4 years) between 2006 and 2016 received standard CXL (Dresden protocol, epithelium-off) for progressive keratoconus. Corrected distance visual acuity (CDVA) and corneal tomography (K₁, K₂, K_max) were repeatedly recorded 1 year (n = 103 eyes) to 10 years (n = 44) postoperatively. Only one eye per patient was included. Paired t-test or Wilcoxon matched-pairs signed rank test was used for parametric and nonparametric data, respectively.

RESULTS

1-3 years preoperatively, median K₂ significantly increased by 1.1 D (p < 0.001). Postoperatively, median K₂ increased by 0.1 D after 1 year, then decreased over the remaining postoperative period by 0.85 D (p = 0.021). K_max fluctuated without significant change. Median apical corneal thickness decreased by 16 µm (p = 0.012) after 5 years and then returned to preoperative values. Mean CDVA showed a significant improvement (decrease in logMAR 0.08 after 10 years, p = 0.010). CXL non-responders, defined by a postoperative increase in K_max>2 D, increased from 16% after 5 to 33% after 10 years. Risk factors for non-response were young age, high astigmatism (>4.3 D), thin cornea (<480 µm), poor initial visual acuity (CDVA ≥0.3 D), and atopic dermatitis. 4 eyes were re-treated 3-4 years after first CXL without complications and keratoconus stabilized thereafter.

CONCLUSIONS

CXL can slow or stop keratoconus progression. However, as the number of responders declines after 5 years, especially patients with risk factors may require re-treatment.

A Comparison Between Cross-Linking Protocols in Patients With Progressive Keratoconus: A Review

Keratoconus (KC) is a noninflammatory cornea disease leading to progressive thinning, causing it to change from its normal dome shape to a cone shape. One of the novel treatments of KC is corneal collagen cross-linking (CXL). Due to its importance, many studies have been conducted to compare corneal cross-linking protocols; this review article aims to discuss corneal cross-linking and compare its different treatment options, including Dresden, accelerated, and customized protocols in patients with progressive KC and their respective long-term outcomes. A search was performed in PubMed and Google Scholar with no language, dates, or study type restriction. Most of the results showed almost no difference between protocols over traditional cross-linking. However, published data are limited, long-term outcomes of novel age groups remain unclear, and further studies are needed.

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.

Oxygen-supplemented transepithelial-accelerated corneal crosslinking with pulsed irradiation for progressive keratoconus: 1 year outcomes

PURPOSE

To investigate the effects of combining oxygen supplementation with enhanced UV-A light and increased riboflavin permeability in improving the efficacy of epithelium-on crosslinking (epi-on CXL).

SETTING

Private eye clinic in Brisbane, Queensland, Australia.

DESIGN

Retrospective single-center nonrandomized uncontrolled longitudinal cohort case series.

METHODS

Transepithelial CXL was performed on keratoconic eyes. Applications of an oxygen goggle and pulsed UV-A irradiation (1 second on, 1 second off) were used to enhance oxygen kinetics during epi-on CXL. Additional procedural modifications included the use of benzalkonium chloride and high UV-A irradiance level (30 mW/cm 2 ) to improve the stromal bioavailability of riboflavin and UV-A. The main efficacy outcomes were the changes in mean corrected distance visual acuity (CDVA) and safety over 12 months. Additional refractive and keratometry (K) outcomes were also observed.

RESULTS

53 eyes (38 patients) were included in this study. 12 months postoperatively, mean CDVA improved from a mean of 0.18 ± 0.2 at baseline to 0.07 ± 0.1 logMAR ( P < .0001). No statistically significant change was observed in maximum K (Kmax) and mean K, which were respectively 51.7 ± 5.8 diopters (D) and 46.4 ± 3.85 D at baseline and 51.2 ± 5.7 D ( P = .152) and 46.0 ± 3.84 D ( P = .06) 12 months postoperatively. Only 3 eyes experienced an increase of more than 2 D in Kmax; however, none of these eyes experienced a CDVA loss. There were no reported infections, corneal scarring, or other severe adverse effects.

CONCLUSIONS

Performing supplemental oxygen epi-on CXL with accelerated, pulsed UV-A irradiation in conjunction with riboflavin permeability enhancers resulted in improved CDVA ( P < .0001) and stable keratometry up to 12 months postoperatively with a good safety profile.

EpiSmart® Crosslinking for Keratoconus: A Phase 2 Study

PURPOSE

The aim of this study was to assess changes in visual acuity after epithelium-on ("epi-on") corneal crosslinking after a diagnosis of keratoconus.

METHODS

Subjects with corneal ectatic diseases were enrolled in a prospective, randomized, controlled, open-label, multicenter trial. Subjects were randomized to 1 of 3 treatment groups and treated with an epi-on crosslinking system including riboflavin/sodium iodide and pulsed UVA exposure (EpiSmart® , CXL Ophthalmics, Encinitas, CA). The UVA treatment groups were 2.4 J/cm2 over 20 minutes, 3.6 J/cm2 over 20 minutes, and 3.6 J/cm2 over 30 minutes. The primary end point was logarithm of the minimum angle of resolution corrected distance visual acuity (CDVA). Secondary end points were logarithm of the minimum angle of resolution uncorrected distance visual acuity (UCVA), maximum corneal curvature (Kmax), and minimum corneal thickness. Data were assessed 6 and 12 months post-operatively, using t-tests for differences from baseline.

RESULTS

Two thousand two hundred twenty-eight subjects were treated with epi-on crosslinking. One thousand nine hundred twenty-two subjects had a diagnosis of keratoconus; other treated eyes had postsurgical and other ectasias. At 6 and 12 months, the subjects with keratoconus demonstrated significant improvements in CDVA, UCVA, and Kmax; minimum corneal thickness was unchanged. One hundred ninety-five subjects (8.7%) reported at least 1 adverse event (AE). A mild corneal epithelial defect was reported in 31 cases (1.4%) and was the only AE reported in >1% of subjects. There were no serious AEs related to the treatment.

CONCLUSIONS

EpiSmart® epi-on crosslinking resulted in mean improvements in CDVA, UCVA, and Kmax at both 6 and 12 months and an excellent safety and efficacy profile in subjects with keratoconus, with few significant side effects. Differences between UVA treatment groups were not significant.

Identification of Treatment Protocols for Effective Cross-Linking of the Peripheral Cornea: An Experimental Study

INTRODUCTION

This study aimed to test and evaluate modified corneal cross-linking (CXL) protocols regarding improved treatment effects on the peripheral cornea in terms of tissue stability and cellular response.

METHODS

Peripheral CXL (pCXL) was performed within a ring of 9-11 mm of 36 human donor corneas with variations in applied energy (5.4, 7.2, and 10 J/cm²) at 9 mW/cm² irradiance. Each energy level was additionally modulated regarding the oxygen level surrounding the cornea during treatment (21%; 100%). Stress-strain tests with endpoints at 12% strain and collagenase A-assisted digestions to complete digestion were performed to evaluate the rigidity and resistance of treated and control tissue. Further, corneas were processed histologically via TUNEL assay and H&E staining to demonstrate the effects on stromal cells during treatment under varying CXL conditions.

RESULTS

Increases in energy dosage achieved significant increases in resistance to stress in all variations except when comparing protocols A and B under normoxic conditions. Supplemental oxygen significantly increased rigidity in protocols B (p < 0.01) and C (p = 0.018). Hyperoxic conditions significantly increased resistance to digestion in all protocols. The number of DNA strand breaks in TUNEL assay staining showed significant increases in all increases in energy as well as with oxygen supplementation.

CONCLUSIONS

Increases in energy and supplemental oxygen improved the effect of CXL, though endothelial safety could not be verified with confidence in high-fluence CXL with supplemental oxygen. Results suggest that CXL protocols using 7.2 J/cm² with 100% O₂ or 10 J/cm² without supplemental oxygen prove most effective without anticipated risk of endothelial damage.