Corneal Collagen Cross-Linking With Riboflavin and Ultraviolet A Light for Pediatric Keratoconus: Ten-Year Results

Topography-guided photorefractive keratectomy combined with accelerated corneal collagen cross-linking versus cross-linking alone for progressive keratoconus: a long-term prospective cohort study

Purpose

To comprehensively compare the long-term outcome of the combined topography guided photorefractive keratectomy (TG-PRK) with accelerated corneal cross-linking (ACXL) and ACXL alone in eyes with progressive keratoconus. The analysis focused on the changes in the detailed corneal aberrometric values.

Methods

This single-center, prospective cohort study included 28 patients (30 eyes) of the TG-PRK plus ACXL group and 14 patients (15 eyes) of the ACXL alone group. The mean duration of the follow-up was 44 ± 10.18 months (ranged from 31 to 65 months). The preoperative data and the postoperative measurement data at the last follow-up visit, including demographic data, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, corneal topography, pachymetry, aberrometry and densitometry were analyzed.

Results

The CDVA significantly improved in the TG-PRK plus ACXL group at the last follow-up visit (p = 0.006), while no significant improvement was found in the ACXL alone group (p = 0.432). The maximal keratometry of the anterior corneal surface (Kmax) of both groups significantly decreased at the last follow-up visit (p < 0.05). Compared with the ACXL alone group, the Kmax of the TG-PRK plus ACXL group showed a greater decline (p = 0.008). The total corneal aberrations, the corneal lower-order aberrations (LOAs), the corneal higher order aberrations (HOAs), the vertical coma and the spherical aberration (SA) at the 4.0 mm and 6.0 mm zone of the TG-PRK plus ACXL group significantly decreased at the last follow-up visit (all p < 0.05). The declines of the total corneal aberrations, the corneal LOAs, the corneal HOAs and the vertical coma at the 4.0 mm and 6.0 mm zone of the TG-PRK plus ACXL group were significantly higher than those in the ACXL alone group (p < 0.001).

Conclusion

Compared with ACXL alone, combined TG-PRK with ACXL procedure had a significantly higher reduction in the corneal HOAs and better CDVA, while providing a similar long-term stability and safety. For progressive keratoconus patients with adequate corneal thickness, the combined procedure might be a recommended treatment option.

Corneal Collagen Cross-linking for Keratoconus in Pediatric and Developmentally Delayed Patients

PURPOSE

Corneal cross-linking (CXL) is the standard of care in patients with keratoconus but presents unique challenges in children and developmentally delayed patients. We present our clinical decision-making algorithm, CXL surgical technique, and outcomes in these groups.

METHODS

A retrospective chart review was undertaken at a tertiary referral center of all patients who underwent CXL for keratoconus at University of Pittsburgh Medical Center (UPMC) Children's Hospital of Pittsburgh between October 1, 2017, and April 1, 2021. Demographic information along with preoperative, intraoperative, and postoperative ophthalmic examination findings were collected. The main outcome measures were indications of CXL, postoperative complications, and visual acuity (VA).

RESULTS

Forty-eight eyes of 34 patients [21 patients (30 eyes) with developmental delay (DD) and 13 patients (18 eyes) with no DD (NDD)] underwent epithelium-off, standard CXL. General anesthesia was used for CXL in all patients except for 3 with NDD. A temporary central tarsorrhaphy was performed in all patients with DD and 7 patients with NDD. The remaining got a bandage contact lens. There were no immediate postoperative complications. A trend toward improvement in VA was noted postoperatively. The mean logMAR VA (with habitual correction) was 0.67 preoperatively and 0.57 postoperatively (P = 0.3) in DD and 0.52 and 0.36, respectively (P = 0.13), in NDD.

CONCLUSIONS

This retrospective review presents a technique for assessment and treatment of keratoconus in children and those with DD. Our technique ensures timely diagnosis and provides a safe method for CXL in these groups. Temporary central tarsorrhaphy is a well-tolerated option to reduce postoperative pain.

Hyperbaric Oxygenation Maintains Elevated Stromal Oxygen Availability During Corneal Collagen Crosslinking with and Without Epithelial Removal

PURPOSE

Corneal collagen cross-linking (CXL) can halt corneal ectasia. Leaving corneal epithelium intact during treatment may reduce the incidence of complications. However, it is under debate whether this reduces efficacy and if oxygen supplementation may be necessary to optimize the cross-linking effect. This study aimed to investigate the impact of hyperbaric oxygenation (HBO) on intracorneal oxygen concentrations during epi-off and epi-on CXL.

METHODS

CXL was performed using riboflavin and ultraviolet-A (UV-A) irradiance (3 mW/cm2 for 30 min) on porcine corneas under normobaric and hyperbaric conditions, with and without supplemented oxygen, with and without epithelium. Intracorneal oxygen concentrations were continuously monitored before and during irradiation. Biomechanical properties were assessed through tensile strength testing.

RESULTS

HBO alone did not cause perceivable changes in stromal oxygen concentrations. Oxygen supplementation resulted in higher oxygen concentration in corneal stroma during CXL. HBO may cause a further increase in oxygen levels, although this was not statistically significant in this study. Notably, a tendency of oxygen levels to rise continuously during UV-irradiation was observed using HBO. Biomechanical properties showend no statistically significant differences between any groups.

CONCLUSIONS

In this ex-vivo model, HBO increased stromal oxygen levels during CXL, regardless of the presence of corneal epithelium. The dynamics in oxygen concentrations in corneal stromal tissue during CXL suggest that time is an important factor to consider in modifications of established protocols. Also, we hypothesize that stromal levels of riboflavin and UV-A irradiance may be more critical to the CXL effect when oxygen is supplemented and epithelium is not removed.

Long-term outcomes of corneal crosslinking

PURPOSE OF REVIEW

This manuscript summarizes contemporary research from 2018 to 2023 evaluating long-term (≥2 years) outcomes of corneal crosslinking (CXL) for progressive keratoconus (KCN).

RECENT FINDINGS

The standard Dresden protocol (SDP) has been utilized clinically since the early 2000 s to treat ectatic disorders, primarily progressive KCN and postrefractive ectasia. Various modifications have since been introduced including accelerated and transepithelial protocols, which are aimed at improving outcomes or reducing complications. This review summarizes data demonstrating that the SDP halts disease progression and improves various visual and topographic indices (UDVA, CDVA, Kmax, K1, K2) up to 13 years postoperatively. Accelerated and transepithelial protocols have been found to be well tolerated alternatives to SDP with similar efficacy profiles. Studies focusing on pediatric populations identified overall higher progression rates after CXL. All protocols reviewed had excellent safety outcomes in adults and children.

SUMMARY

Recent studies revealed that SDP successfully stabilizes KCN long term, and a variety of newer protocols are also effective. Pediatric patients may exhibit higher progression rates after CXL. Further research is required to enhance the efficacy and ease of these protocols.

Update on corneal crosslinking for keratoconus and corneal ectasia

PURPOSE OF REVIEW

To review corneal crosslinking for keratoconus and corneal ectasia, and recent developments in the field. This study will review the mechanism of crosslinking, clinical approaches, current results, and potential future innovations.

RECENT FINDINGS

Corneal crosslinking for keratoconus was first approved by U.S. FDA in 2016. Recent studies have confirmed the general long-term efficacy of the procedure in decreasing progression of keratoconus and corneal ectasia. New types of crosslinking protocols, such as transepithelial treatments, are under investigation. In addition, adjunctive procedures have been developed to improve corneal contour and visual function in these patients.

SUMMARY

Crosslinking has been found to be well tolerated and effective with the goal of decreasing progression of ectatic corneal diseases, keratoconus and corneal ectasia after refractive surgery. Studies have shown its long-term efficacy. New techniques of crosslinking and adjunctive procedures may further improve treatments and results.

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.

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.

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.

Differences Between Simulated Keratometry and Total Corneal Power in Eyes With Keratoconus and a Formula to Improve IOL Power Calculation Results

PURPOSE

To compare simulated keratometry (SimK) and total corneal power (TCP) in keratoconic eyes, to determine whether the differences are systematic and predictable and to evaluate an adjusted TCP-based formula for intraocular lens (IOL) power calculation.

METHODS

In a consecutive series of keratoconic eyes, measurements of SimK, TCP, posterior keratometry, and anterior and posterior corneal asphericities (Q-values) were retrospectively collected. The difference between SimK and TCP was linearly correlated to the biometric parameters. In a separate sample of keratoconic eyes that had undergone cataract surgery, IOL power was calculated with the Barrett Universal II, Hoffer QST, Holladay 1, Kane, and SRK/T formulas using the SimK and an adjusted TCP power. The respective prediction errors were calculated.

RESULTS

A total of 382 keratoconic eyes (271 patients) were enrolled. An increasing overestimation of SimK by TCP was detected from stage I to III, with a significant correlation between the SimK and TCP difference and SimK in the whole sample (P < .0001, r2 = 0.1322). Approximately 7% of cases presented an underestimation of SimK by TCP. IOL power calculation with the adjusted TCP improved outcomes, achieving a maximum of 80% of eyes with a prediction error within ±0.50 diopters with the Hoffer QST, Holladay 1, and Kane formulas.

CONCLUSIONS

Overall, SimK overestimated TCP. Such a difference could not be predicted by any variable. The proposed TCP-adjustment formula (TCPadj = TCP + 0.56 diopters) in keratoconic eyes for IOL power calculation might be valuable for improving refractive outcomes. [J Refract Surg. 2024;40(4):e253-e259.].

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.

Outcomes of accelerated corneal cross-linking for pediatric and adult keratoconus: a comparative study

PURPOSE

To compare the visual, refractive, and topographic outcomes of a high irradiance accelerated corneal crosslinking (ACXL) protocol after a 12-month follow-up between pediatric and adult patients with progressive keratoconus (KC).

METHODS

Retrospective, comparative, cohort study. Patients with KC were divided into two groups: pediatric (≤ 18 years) and adult (> 18 years). All of them were managed with epi-OFF ACXL (30 mW/cm2, 8 min, pulsed 1:1 on and off = 7.2 J/cm2). Visual, refractive, and topographic values were measured preoperatively and at 1, 3, 6, and 12 months postoperative. KC progression, defined as a Kmax increase of  ≥ 1D during follow-up, was recorded.

RESULTS

Eighty-nine eyes (53 patients) were included for analysis; 45 (50.6%) eyes were from pediatric patients and 44 (49.4%) from adults. At one-year follow-up, pediatric patients experienced significantly higher rates of progression (22.2% vs. 4.5%, p = .014). Contrariwise, female gender (Beta = - 3.62, p = .018), a baseline uncorrected visual acuity of Snellen ≥ 20/60 (Beta = - 5.96, p = .007), and being ≥ 15 years at ACXL treatment (Beta = - 0.31, p = .021) were associated with non-progressive disease. A significant improvement in best-corrected visual acuity, Kmin, Km, and Kmax was recorded in both groups. Overall, 86.5% of eyes from both groups showed Kmax stabilization or improvement.

CONCLUSIONS

Despite the similarity in visual, refractive, and topographic outcomes in both groups, younger age was associated with KC progression after ACXL at one year of follow-up.

High-Fluence Epithelium-off Accelerated Pulsed Corneal Cross-linking (15 mW/cm2; 7.2 J/cm2) for Pediatric Keratoconus: A 3-Year Retrospective Analysis

PURPOSE

To assess the safety and efficacy of treatment and secondarily determine the topographic changes, visual outcomes, and demarcation line depth after high-fluence pulsed light accelerated cross-linking (ACXL) in pediatric patients (younger than 18 years) with progressive keratoconus.

METHODS

This retrospective analysis included 32 eyes (25 children, aged 11 to 18 years), with progressive keratoconus treated with high-energy epithelium-off pulsed light ACXL (7.2 J/cm2, 15 mW/cm2, 12 minutes, 2 seconds on/1 second off). Corrected distance visual acuity (CDVA), Scheimpflug tomography, and anterior optical coherence tomography measurements were recorded preoperatively and 1, 2, and 3 years postoperatively.

RESULTS

A total of 32 eyes were included. Significant CDVA improvement, pachymetry, and maximum keratometry reduction were found at all follow-up visits. Mean keratometric values remained stable, and astigmatism showed a mild worsening (< 0.25 D) with statistical significance at 1 and 3 years. Total aberration showed discordant results and coma aberration had a slight improvement without statistical significance. The demarcation line depth was 265 ± 26 μm. Three patients developed mild haze without visual acuity loss. None of the patients underwent a second CXL procedure.

CONCLUSIONS

In pediatric patients, high-fluence epithelium-off pulsed light ACXL appears to be a safe and effective procedure to halt the progression of keratoconus, slightly improving the CDVA and keratometric values. [J Refract Surg. 2024;40(3):e148-e155.].

Prevalence of Keratoconus Based on Scheimpflug Corneal Tomography Metrics in a Pediatric Population From a Chicago-Based School Age Vision Clinic

PURPOSE

Determine the pediatric prevalence of keratoconus (KC) using Scheimpflug corneal tomography.

METHODS

A prospective observational study was done on subjects aged 3 to 18 years at the Princeton Vision Clinic, Chicago, IL. Scheimpflug tomography (Pentacam HR, OCULUS Optikgerate GmbH) scans (Belin/Ambrósio Enhanced Ectasia BAD3) yielded BAD Final D (Final D) and Back Elevation at the Thinnest Point (BETP) measurements. Criteria differentiating non-KC from KC suspects & KC were, Non-KC -Final D <2.00 in both eyes; KC suspect -Final D ≥2.00 and <3.00 in combination with BETP ≥18 μm for myopia and ≥28 μm for hyperopia/mixed astigmatism in at least one eye; and KC -Final D of ≥3.00 with BETP ≥18 μm for myopia or ≥28 μm for hyperopia/mixed astigmatism in at least one eye. Two thousand two hundred and six subjects were recorded, removing duplicate and poor-quality scans leaving 2007 subjects.

RESULTS

Of 2007 subjects, six were classified as KC -prevalence of 1:334, three subjects were KC suspects -prevalence of 1:669, and total prevalence of KC suspects and KC was 1:223.

CONCLUSION

The prevalence of KC in children is higher than previously reported, emphasizing the importance of sensitive screening for KC at its earliest manifestation as standard in pediatric comprehensive eye examinations.

Analysis of the outcomes of three different cross-linking protocols for treatment of paediatric keratoconus: A multicentre randomized controlled trial

PURPOSE

To analyse long-term outcomes of standard cross-linking (SCXL), accelerated cross-linking (ACXL) and transepithelial cross-linking (TCXL) in the treatment of progressive paediatric keratoconus regarding stability, safety and efficacy.

METHODS

This prospective multicentre randomized controlled trial included 97 eyes of 97 paediatric patients with stages I-III ABCD keratoconus grading system, who were randomized into three groups; SCXL group (control group, n = 32; 3 mW/cm2  × 30 min/5.4 J/cm2 ), ACXL (n = 33; 18 mW/cm2  × 5 min/5.4 J/cm2 ) and TCXL (n = 32; 18 mW/cm2  × 5 min/5.4 J/cm2 ). Subjective refraction, uncorrected and corrected visual acuity, keratometry and pachymetry measurements using corneal topography were recorded preoperatively and 1, 2 and 3 years postoperatively.

RESULTS

SCXL group exhibited significant successive improvements in the mean visual, refractive and keratometric parameters throughout the entire postoperative 3 years while ACXL group exhibited significant improvements in visual and keratometric parameters in the first postoperative year that remained stable in second and third postoperative years. TCXL group exhibited significant progressive deterioration in all mean parameters compared to SCXL and ACXL (p < 0.0001). Both SCXL and ACXL revealed final 100% success rate with good stability while TCXL revealed final 22% failure rate with keratoconus progression (p < 0.0001).

CONCLUSION

SCXL and ACXL were comparable in halting keratoconus progression and achieved good stability and safety; however, SCXL was more efficient than ACXL as it yielded greater significant postoperative mean visual, refractive and keratometric improvements achieving smoother corneal remodelling. Both SCXL and ACXL were much superior to TCXL. SCXL is the best CXL treatment option for paediatric keratoconus while ACXL is a good and effective alternative.

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.

Clinical Results of Accelerated Iontophoresis-Assisted Epithelium-on Corneal Cross-linking for Progressive Keratoconus in Children

PURPOSE

To evaluate the clinical characteristics of pediatric patients with progression of keratoconus after accelerated iontophoresis-assisted epithelium-on corneal cross-linking (I-ON CXL) and to assess the efficacy and safety of re-treatment using accelerated epithelium-off CXL (epi-OFF CXL).

METHODS

Sixteen eyes of 16 patients (mean age: 14.6 ± 2.5 years) with keratoconus underwent I-ON CXL. The main outcome measures were uncorrected distance visual acuity, corrected distance visual acuity, maximum keratometry index (Kmax), minimum corneal thickness, elevation front and elevation back measured at the thinnest point, total higher order aberrations root main square (HOA RMS), coma RMS, and spherical aberration. An increment of Kmax greater than 1.00 diopter (D) and a decrease of greater than 20 µm in pachymetry were considered to determine the progression of keratoconus. Patients with progression of keratoconus after I-ON CXL were re-treated using an epi-OFF CXL protocol.

RESULTS

Two years after I-ON CXL, 12 patients showed progression of keratoconus, whereas 4 patients were stable. There was significant worsening of Kmax (P = .04) and steepest keratometric reading (P = .01). Furthermore, a significant correlation was documented between progression of keratoconus and age (P = .02). These patients were re-treated using an epi-OFF protocol and after 2 years all patients were stable, and a statistically significant reduction of the mean Kmax (P = .007), HOA RMS (P = .05), and coma RMS (P = 05) was observed.

CONCLUSIONS

I-ON CXL was ineffective in the treatment of pediatric keratoconus in younger children, whereas it had an efficacy of 2 years in older children. Re-treatment using epi-OFF CXL proved effective to halt progression of keratoconus after I-ON CXL failure. [J Pediatr Ophthalmol Strabismus. 2024;61(1):44-50.].

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.

Accelerated Corneal Crosslinking for Treatment of Keratoconus in Children and Adolescents under 18 Years of Age

PURPOSE

To evaluate the efficacy of accelerated (9 mW/cm2, 10 min) epithelium-off (epi-off) corneal crosslinking (A-CXL) in keratoconus (KC) patients < 18 years of age.

PATIENTS AND METHODS

Our retrospective study included 41 eyes (25 male and 5 female patients, mean age 15.3 ± 1.2 years) who underwent A-CXL (9 mW/cm2, 10 min) because of progressive KC or critical KC at first presentation or asymmetrical finding in the partner eye. Outcome measures were best-corrected visual acuity (BCVA) and tomography readings (Pentacam HR, Oculus, Wetzlar, Germany), evaluated 2 years, 1 year, 6 months preoperatively, prior to surgery (pre-CXL) and 6 weeks, 6 months, 1 year, 2 years, > 2 years postoperatively (post-CXL). The demarcation line was assessed by anterior segment optical coherence tomography (SS-1000 and CASIA 2, Tomey, Nagoya, Japan).

RESULTS

Total deviation value increased statistically significantly 6 months pre-CXL to pre-CXL. Anterior steep, flat, and mean keratometry values showed a statistically significant increase 6 weeks post-CXL (p < 0.05), followed by a significant decrease until 2 years post-CXL for steep and mean keratometry. Kmax increased 6 weeks post-CXL without statistical significance and decreased significantly even > 2 years post-CXL (p < 0.0001). Posterior keratometry as well as anterior and posterior astigmatism did not show any significant changes post-CXL. Thinnest and apical pachymetry decreased significantly until 6 months post-CXL (p < 0.05) and remained stable > 2 years post-CXL (p > 0.05). BCVA decreased 6 weeks post-CXL but improved significantly > 2 years post-CXL (p = 0.003). The demarcation line reached an average depth of 52.1%.

CONCLUSIONS

Epi-off A-CXL stabilizes KC progression in patients < 18 years even > 2 years postoperatively and leads to a deep demarcation line. A "pseudoprogression" is observed up to the 6-week follow-up, which is not indicative of the long-term results.

Long-Term Outcomes After Corneal Cross-linking for Progressive Keratoconus and Corneal Ectasia: A 10-Year Follow-Up of the Pivotal Study

OBJECTIVES

To report on the topographic and visual outcomes 10 years after corneal cross-linking in patients with progressive keratoconus and corneal ectasia after refractive surgery.

METHODS

Cross-sectional cohort study of an original, prospective, randomized, clinical trial. Patients treated in a single center cornea and refractive surgery practice as part of the U.S. pivotal trials, which led to the Food and Drug Administration approval of corneal cross-linking, were recruited for a 10-year follow-up examination. LogMar lines (LL) of uncorrected visual acuity (UCVA) and best spectacle--corrected visual acuity (BSCVA), maximum keratometry, and thinnest pachymetry were evaluated. In addition, the Belin ABCD progression display was used to determine progression (95% confidence interval) of the anterior curvature, posterior curvature, and corneal thickness of each individual eye included.

RESULTS

Nineteen eyes of 13 patients treated with standard cross-linking returned for a 10-year follow-up examination. Mean maximum keratometry changed from 58.2±12.0 diopters (D) to 58.3±10.1 D, thinnest pachymetry changed from 440.6±51.6 µm to 442.3±54.4 μm, UCVA changed from 0.79±0.42 LL to 0.86±0.46 LL, and BSCVA changed from 0.38±0.26 LL to 0.33±0.34 LL, 10 years after cross-linking. Individually, 68.5% of the entire cohort, 81.8% of keratoconus eyes, and 50% of eyes with corneal ectasia remained topographically stable 10 years after standard cross-linking.

CONCLUSIONS

In the entire cohort, visual acuity and topography remained stable 10 years after cross-linking. Over the long-term, eyes with keratoconus seem to be more stable than those with corneal ectasia.

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

PURPOSE

To assess long-term efficacy and safety of iontophoresis-assisted transepithelial corneal cross-linking (I-CXL) for keratoconus.

PATIENTS AND METHODS

Twenty-seven eyes of 21 patients (15 M, 6F) affected by progressive keratoconus were evaluated. All subjects were treated with iontophoresis-assisted transepithelial CXL. The patients were examined at baseline and each 6 months after the CXL procedure. Only subjects who completed the follow-up of 5 years were considered in this study. The main outcome measures were uncorrected visual acuity (UCVA), corrected visual acuity (CDVA), corneal transparency and corneal parameters such as K-max, central corneal thickness (CCT) and at the thinnest point, and high-order ocular aberrations (HOAs). The ABCD system was used to determine the progression and re-progression of ectasia.

SETTING

Ophthalmology Clinic, University Hospital of Messina, Messina, Italy.

RESULTS

At 5 years, significant improvements of UCVA from 0.53 ± 0.33 logMAR to 0.4 ± 0.33 logMAR (p = 0.001) and HOAs (p = 0.01) were registered. No significant changes of CDVA (p = 0.4), K-max (p = 0.75), CCT (p = 0.5) were observed at the end of follow-up period. The ABCD system showed re-progression in 25.9% of eyes after 5 years. No adverse events such as corneal opacities and infections were reported.

CONCLUSIONS

Iontophoresis-assisted transepithelial CXL resulted to be safe and effective to stabilize progressive keratoconus in adults at a long-term follow-up.

Corneal Biomechanical Evaluation After Meniscus-Shaped Stromal Lenticule Addition Keratoplasty (MS-SLAK) for Keratoconus

PURPOSE

To evaluate corneal biomechanical changes after meniscus-shaped stromal lenticule addition keratoplasty (MS-SLAK) performed for the treatment of keratoconus.

METHODS

This interventional study included patients affected by advanced keratoconus (stage III and IV) who underwent examination with a dynamic Scheimpflug analyzer and non-contact tonometer (Corvis ST; Oculus Optikgeräte GmbH) at baseline and 12 months after MS-SLAK. The biomechanical parameters evaluated in this study were integrated inverse radius (1/R), deformation amplitude ratio (DA ratio), stiffness parameter at first applanation (SP-A1), biomechanical intraocular pressure (bIOP), central corneal thickness (CCT), and stress-strain index (SSI).

RESULTS

Sixteen patients were enrolled in the study. The analysis was ultimately conducted on 15 patients. Comparative analyses showed an increase in corneal stiffness as demonstrated by a rise in SSI (P < .0001) and SP-A1 (P < .0001) and a decrease in DA ratio (P < .0001) and 1/R (P = .01). A significant increase in CCT was found (P < .0001). No statistically significant modification was found for bIOP (P = .43).

CONCLUSIONS

The corneal biomechanical analyses evaluated by the Corvis ST showed that MS-SLAK for advanced keratoconus is able to increase corneal overall stiffness. This result is explained by the significant increase in thickness induced by MS-SLAK. [J Refract Surg. 2023;39(7):499-504.].

Safety and Efficacy of Corneal Cross-Linking in Patients Affected by Keratoconus: Long-Term Results

The present study evaluated the effectiveness and safety of corneal collagen cross-linking (CXL). A total of 886 eyes with progressive keratoconus were enrolled in a retrospective cohort study in a tertiary care university hospital. CXL was performed using a standard epithelium-off Dresden protocol. Visual outcomes, maximum keratometry (Kmax), demarcation line measurements, and complications were recorded. Visual outcomes and keratometric data were analyzed in a subgroup comprising 610 eyes. Uncorrected distance visual acuity (UDVA) improved from 0.49 ± 0.38 LogMAR to 0.47 ± 0.39 LogMAR (p = 0.03, n = 610) three years after the procedure, while corrected distance visual acuity (CDVA) improved from 0.15 ± 0.14 LogMAR to 0.14 ± 0.15 LogMAR (p = 0.007, n = 610). A significant reduction of Kmax from 56.28 ± 6.10 to 54.98 ± 6.19 (p < 0.001, n = 610) was observed three years after CXL. In five eyes (0.82%, 5/610) keratoconus progression continued after CXL. Three eyes were retreated successfully with documented refractive and topographic stability after five years. In the 35 eyes that completed 10 years of follow-up, mean visual acuity and topographic parameters remained stable. In conclusion, CXL is a safe and effective treatment for avoiding keratoconus progression. Long-term data are encouraging, supporting a high safety profile for this procedure.

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.

Outcome indicators for cross linking in pediatric keratoconus

Purpose

To evaluate the predictive factors for successful corneal collagen cross-linking (CXL) in pediatric patients with Keratoconus (KC).

Methods

This retrospective study was conducted using a prospectively built database. Patients (18 years old or younger) underwent CXL for KC between 2007 and 2017, with a 1-year follow-up period or longer. The outcomes included changes in Kmax (delta [Δ] Kmax = Kmax_last - Kmax_pre) and LogMAR visual acuity (ΔLogMAR = LogMAR_last - LogMAR_pre).The effects of CXL type (accelerated or non-accelerated), demographics (age, sex, background of ocular allergy, ethnicity), preoperative LogMAR visual acuity, maximal corneal power (Kmax), pachymetry (CCT_pre), refractive cylinder, and follow-up (FU) time on the outcomes were analyzed.

Results

One hundred thirty-one eyes of 110 children were included (mean age, 16 ± 2 years; range, 10-18 years). Kmax and LogMAR improved from baseline to last visit: from 53.81 D ± 6.39 D to 52.31 D ± 6.06 D (p < 0.001) and from 0.27 ± 0.23 LogMAR units to 0.23 ± 0.19 LogMAR units (p = 0.005), respectively. A negative ΔKmax (meaning corneal flattening) was associated with a long FU, low CCT_pre, high Kmax_pre, high LogMAR_pre, and non-accelerated CXL on univariate analysis. High Kmax_pre and non-accelerated CXL were associated with negative ΔKmax in the multivariate analysis.A negative ΔLogMAR (meaning vision improvement) was associated with a high LogMAR_pre in univariate analysis.

Conclusion

CXL is an effective treatment option in pediatric patients with KC. Our results showed that the non-accelerated treatment was more effective than the accelerated treatment. Corneas with advanced disease had a greater effect on CXL.

Paediatric cornea crosslinking current strategies: A review

Background

In the general population, 1 in 2000 people has keratoconus. Indians and other people from Southeast Asia have a higher incidence of keratoconus. Children with keratoconus typically present earlier in life and with a more severe disease. Rubbing the eyes has been identified as a risk factor. Children have a higher incidence and a faster rate of keratoconus progression. Visual rehabilitation in children with keratoconus is challenging. They have a low compliance with contact lens use. Many of these children require penetrating keratoplasty at an early age. Therefore, stopping the progression of keratoconus in children is of paramount importance.

Main text

Compared to treatment, keratoconus progression prophylaxis is not only preferable, but also easier. Corneal collagen cross-linking has been shown to be safe and effective in stopping its progression in children. The Dresden protocol, which involves central corneal deepithelization (7-9 ​mm), saturation of the stroma with riboflavin (0.25%), and 30 ​min UV-A exposure, has proven to be the most successful. Two significant disadvantages of the typical Dresden regimen are the prolonged operating time and the significant post-operative pain. Accelerated-CXL (9 ​mW/cm2 x 10 ​min) has been studied to reduce operative time and has been shown to be equally effective in some studies. Compared to accelerated CXL or traditional CXL, epi-off procedures, transepithelial treatment without the need for de-epithelialization and without postoperative discomfort, have been shown to be safer but less effective. Corneal crosslinking should only be performed after treating children with active vernal keratoconjunctivitis. Corneal opacity, chronic corneal edema, sterile infiltrates, and microbial keratitis have been reported after cross-linking of corneal collagen.

Conclusions

The "Dresden protocol", also known as the conventional corneal cross-linking approach, should be used to halt the progression of keratoconus in young patients. However, if the procedure needs to be completed more rapidly, accelerated corneal crosslinking may be considered. Transepithelial corneal cross-linking has been proven to be less effective at stabilizing keratoconus, although being more safer.

Three-year follow-up of accelerated versus standard corneal cross-linking in paediatric Keratoconus

PURPOSE

Standard corneal collagen cross-linking (S-CXL) is an effective treatment to arrest Keratoconus (KC) progression in children. Less is known on the long-term efficacy of accelerated CXL (A-CXL) in paediatric populations.

METHODS

A historical cohort analysis of paediatric patients (≤18 years) with KC who underwent S-CXL and A-CXL at two tertiary referral centres in Israel between 2010-2017. Preoperative and 3-year postoperative evaluation included changes in visual acuity (best spectacle corrected [BSCVA]) and uncorrected [UCVA]), refractive errors, and keratometric data.

RESULTS

Ninety-three eyes of 93 patients were analysed (A-CXL: n = 39; S-CXL: n = 54). Baseline characteristics were similar between groups. Both groups showed a significant improvement in visual acuity compared to baseline (S-CXL: 0.810-0.602 LogMAR UCVA; A-CXL: 0.890-0.306 LogMAR UCVA, p < 0.05 for both). Improvement in BSCVA and UCVA following A-CXL was non-inferior to S-CXL (< ± 0.2 LogMAR). Kmax decreased by a mean of 0.98 ± 5.56 dioptres following S-CXL (p = 0.02) and by 1.48 ± 8.4 dioptres following A-CXL (p = 0.015). Thinnest pachymetry decreased following both treatments (S-CXL: by 26.8 ± 40.7 µm, p = 0.001, A-CXL: by 10.2 ± 13.4 µm, p = 0.028), the difference between groups was within the non-inferiority margin (< ± 10 µm).

CONCLUSIONS

Paediatric patients followed for three years after A-CXL showed improved visual function, reduced corneal astigmatism and Kmax, and decreased thinnest corneal thickness. A-CXL was non-inferior to S-CXL at three years in terms of best-corrected and uncorrected visual acuity, thinnest pachymetry, and astigmatism. For Kmax, non-inferiority could not be concluded.

Impact of corneal collagen cross-linking on vision-related quality of life measured with the keratoconus outcomes research questionnaire (KORQ) in patients with keratoconus

PURPOSE

To assess the impact of corneal collagen cross-linking on self-reported vision-related quality of life (VR-QoL) in keratoconus patients by means of the Keratoconus Outcomes Research Questionnaire (KORQ), a new disease-specific patient reported outcomes measures (PROMs) tool.

METHODS

Patients with progressive keratoconus undergoing corneal collagen cross-linking were consecutively enrolled. Patients completed the KORQ before and after the treatment, at 1, 3 and 6 months. Data were collected regarding the visual acuity and the topographic, aberrometric and pachymetric parameters of both eyes. Patients were also asked to quantify their eye rubbing behavior on a Visual Analogue Scale (VAS) from 0 to 10, before and 6 months after treatment. The KORQ scores were associated with the visual acuity, topographic, aberrometric and pachymetric data by means of the Spearman correlation coefficient.

RESULTS

The Activity Limitation (AL) subscale score was higher after surgery. Preoperatively, negative correlations were observed between the KORQ AL score and Best Corrected Visual Acuity (logMAR), maximum keratometry, flattest keratometry, steepest keratometry, symmetry index front and higher order aberrations (HOA) of the treatment eye. Postoperatively, we observed a shift toward the fellow eye, with stronger correlation of the KORQ scores with the fellow eye parameters. The Symptoms subscale score correlated with the aberrometric parameters of both eyes at various time points. Statistically significant correlations were observed between the change in KORQ scores and the change in aberrometric parameters. A statistically significant reduction in the eye rubbing behavior was detected (p < 0,0001).

CONCLUSIONS

These results suggest that the corneal cross-linking treatment is effective both in improving the subjective perception of the disease by the patient and in stabilizing the objective indicators of disease progression. Keratometric, aberrometric and visual acuity values showed a significant impact on self-reported VR-QoL. Corneal cross-linking, by halting the worsening of these parameters, may bear a beneficial effect on VR-QoL.

The research progress on the molecular mechanism of corneal cross-linking in keratoconus treatment

Keratoconus (KC) is a corneal anomaly that is manifested in a limited cone-like bulge with corneal thinning. Many molecules in the cornea change during the development of KC, including various components of the extracellular matrix, cytokines, cell connection, and cell adhesion-related proteins. Several treatment options are available, with corneal cross-linking (CXL) being the treatment of choice for early KC. However, postoperative complications have been reported in some CXL patients, mainly caused by corneal epithelial resection. Despite the fact that some novel approaches have helped to reduce some of the initial post-operative issues, their effectiveness seems to be inferior to that of the original CXL. To keep effectiveness while avoiding these negative effects, it is necessary to study the mechanism of CXL in KC treatment at the molecular level. This article provides a review of the molecular mechanism of CXL in the treatment of KC from four aspects: enzyme activity, signal transduction pathway, corneal-related proteins, and other KC-related molecules, further confirming the feasibility of CXL treatment of KC, providing new ideas for improving CXL.

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.

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.

Alterations in the choroidal thickness and retinal vascular caliber in keratoconus

PURPOSE

To compare the choroidal thickness (CT) and retinal vascular caliber in the differentiation of patients who have keratoconus (KC) from those of astigmatic and normal patients.

METHODS

This was a prospective, cross-sectional study. A total of 72 patients who had KC, 70 who had astigmatism, and 83 healthy control subjects were enrolled in this study. All the patients were examined using the Sirius topography system and spectral domain optical coherence tomography with enhanced depth imaging. Using the digital fundus photographs, the retinal vascular calibers were calculated. The measurements were also analyzed between the KC stages according to the Amsler-Krumeich classification.

RESULTS

The CT measurements were significantly higher in the KC group, when compared with the other 2 groups, in each location (P < 0.05). No statistically significant difference was observed with regards to the central retinal artery equivalent (CRAE) values (P = 0.959), while significant differences were noted in the central retinal vein equivalent (CRVE) among the groups (P = 0.011). Significant increases were noted in the CT as the stage of KC progressed, except at temporal 3000 µm (P = 0.603). No statistically significant difference was observed with regards to the CRAE among the stages (P = 0.901). However, the CRVE changes increased remarkably as the stages advanced (P < 0.001).

CONCLUSION

The patients who had KC seemed to have a thicker CT and higher CRVE values than the healthy individuals, and these differences were progressively increased as the stages of KC advanced. Reflecting the vascular effects of inflammation, the high CRVE supported theories based on the inflammatory component of KC.

Evaluation of a Post-Operative Therapy Protocol after Epithelium-Off Corneal Cross-Linking in Patients Affected by Keratoconus

A large retrospective study evaluated the safety of a post-operative therapy protocol after epithelium-off corneal collagen cross-linking (CXL). In total, 1703 eyes of the 1190 patients with progressive keratoconus were enrolled in a retrospective cohort study in a tertiary care university hospital. CXL was performed using a standardized technique (Dresden protocol: 0.1% riboflavin solution containing dextran 20% for 30 min during the soaking phase followed by 30-min ultraviolet A irradiation (3 mW/cm²)). Postoperatively, a bandage contact lens was applied, and therapy included a topical fluoroquinolone antibiotic until the epithelium healed, followed by topical fluorometholone treatment for three weeks. Post-operative complications were recorded and analyzed. No cases of infectious keratitis occurred, whereas peripheral sterile infiltrates were observed in 1.17% of cases. Trace haze was typically present but did not have an impact on visual acuity. In fifteen cases (0.88%), visually significant anterior stromal opacity developed. Mild signs of dry eye were observed in 22 eyes (1.29%). The present study demonstrates that a post-operative treatment protocol including fluoroquinolone antibiotics and a BCL in the first phase until complete epithelial healing, followed by a three-week period of topical steroid treatment is safe and not associated with the development of microbial keratitis.

Corneal cross-linking guards against infectious keratitis: an experimental model

BACKGROUND

PACK-CXL (photo-activated chromophore for keratitis-corneal cross-linking) is an alternative option in treatment of corneal infections. It inhibits corneal melting by increasing the stromal resistance, besides the microbicidal effect of photo-activated riboflavin.

METHODS

Corneal infection with Pseudomonas aeruginosa and Staph aureus bacteria was induced in 20 eyes of 10 rabbits after 6 weeks of corneal cross-linking in half of the eyes, while the other acted as control group. Clinical and corneal histopathological examination was done to evaluate the extent of inflammation, ulceration, organism penetration, and depth of corneal stromal affection.

RESULTS

The control eyes developed severe inflammation compared to the cross-linked eyes. Corneal melting occurred in 6 eyes in the control versus none in cross-linked group. Histopathological examination showed that the inflammation was confined to the superficial part of the stroma with localization of the inflammation in the cross-linked eyes in contrast to the control eyes that showed deep infiltration.

CONCLUSION

PACK-CXL provides infection localization through increasing the corneal rigidity and resistance to enzymatic digestion, even in the absence of the riboflavin microbicidal role. So, early PACK-CXL is worth to be considered in the IK treatment algorithm.

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 in Corneal Collagen Crosslinking to Treat Keratoconus: A Systematic Review and Meta-Analysis

PURPOSE

Keratoconus is a disorder that results in visual loss from increased corneal high-order aberrations and irregular astigmatism and reduces quality of life. The primary treatment for progressive keratoconus is crosslinking (CXL). Recently, it has been suggested that oxygen enhances the type II photodynamic reaction of CXL that is oxygen dependent. Our study investigated the effect of increased oxygen availability in epithelium-on CXL on visual acuity and corneal curvature.

METHODS

We searched PubMed, EMBASE, Medline, Web of Science, and Scopus databases on November 3, 2021. We included studies that reported increased oxygen availability during CXL in patients with keratoconus published within the last 10 years. A meta-analysis on the primary outcomes, maximum keratometry, and corrected distance visual acuity, was conducted.

RESULTS

The search yielded 108 publications which were screened and assessed for eligibility. Six studies were included in the systematic review and 5 studies were included in our meta-analysis of the outcomes of increased oxygen availability in accelerated CXL. The meta-analysis on data after 6 months of follow-up found a significant decrease in mean maximum keratometry of 1.2 diopter (95% confidence interval: 0.2-2.3; P =0.02) and an improvement in mean corrected distance visual acuity by 0.08 logMAR (95% confidence interval, 0.02-0.13; P =0.01). There were no serious adverse events reported.

CONCLUSIONS

Increasing oxygen during epithelium-on CXL improved visual acuity and produced corneal flattening without any serious adverse events in patients with keratoconus. The demarcation line depth was significantly higher with oxygen compared to the control group. Further data are required with a control group and long-term follow-up across a range of CXL protocols for implementation into standard clinical practice.

Effectiveness of collagen cross-linking induced by two-photon absorption properties of a femtosecond laser in ex vivo human corneal stroma

This study aimed to investigate the effectiveness of two-photon induced collagen cross-linking (CXL) using femtosecond lasers in human corneal stroma. An 800-nm femtosecond laser optical path for CXL was established. Corneal samples that received two-photon induced CXL and ultraviolet-A (UVA) CXL underwent uniaxial stretching experiments, proteolytic resistance assays and observation of collagen fiber structure changes. Two-photon induced CXL can achieve corneal stiffening effects comparable to UVA CXL and showed better advantages at low strains. The cornea after two-photon induced CXL exhibited high enzymatic resistance and tight collagen fiber arrangement. Two-photon induced CXL promises to be a new option for keratoconus.

Progression of Pediatric Keratoconus After Corneal Cross-Linking: A Systematic Review and Pooled Analysis

PURPOSE

Corneal collagen cross-linking (CXL) is an effective treatment to slow down keratoconus (KC) progression in adults. Several studies have also shown efficacious outcomes in pediatric populations, yet no systematic analysis has been performed and no accepted definition for progression is available in children after CXL. This study aimed to establish the most commonly used criteria for progression and to conduct a systematic review of the literature with pooled analysis to assess children's keratoconus progression after CXL.

METHODS

A systemic literature review combined with pooled analysis was performed on full-length studies of KC after CXL treatment in a pediatric population and the methods used to report progression were analyzed.

RESULTS

Thirty-seven studies (2078 eyes) were identified on the rates of KC progression after CXL. The most common method to report progression was increased Kmax, Kmean, or Ksteep by ≥1.0 diopter (78.3% of studies). Using these criteria, the mean pooled progression rate after epithelium-off CXL was 9.9% (95% confidence interval: 6.1% -14.6%, total pooled sample size: 1508 eyes) with high heterogeneity between studies [I 2 = 86.48% (95% confidence interval: 80.98 - 90.39), P < 0.0001].

CONCLUSIONS

When considering KC progression after CXL in children, with an increase in Kmax, Kmean, or Ksteep ≥ 1.0 diopter, the progression risk was roughly 10%. We encourage clear quantitative reporting of KC progression in future studies evaluating CXL efficacy in pediatric populations.

Evaluation of artificial intelligence models for the detection of asymmetric keratoconus eyes using Scheimpflug tomography

BACKGROUND

To evaluate artificial intelligence (AI) models based on objective indices and raw corneal data from the Scheimpflug Pentacam HR system (OCULUS Optikgeräte GmbH, Wetzlar, Germany) for the detection of clinically unaffected eyes in patients with asymmetric keratoconus (AKC) eyes.

METHODS

A total of 1108 eyes of 1108 patients were enrolled, including 430 eyes from normal control subjects, 231 clinically unaffected eyes from patients with AKC, and 447 eyes from keratoconus (KC) patients. Eyes were divided into a training set (664 eyes), a test set (222 eyes) and a validation set (222 eyes). AI models were built based on objective indices (XGBoost, LGBM, LR and RF) and entire corneal raw data (KerNet). The discriminating performances of the AI models were evaluated by accuracy and the area under the ROC curve (AUC).

RESULTS

The KerNet model showed great overall discriminating power in the test (accuracy = 94.67%, AUC = 0.985) and validation (accuracy = 94.12%, AUC = 0.990) sets, which were higher than the index-derived AI models (accuracy = 84.02%-86.98%, AUC = 0.944-0.968). In the test set, the KerNet model demonstrated good diagnostic power for the AKC group (accuracy = 95.24%, AUC = 0.984). The validation set also proved that the KerNet model was useful for AKC group diagnosis (accuracy = 94.12%, AUC = 0.983).

CONCLUSIONS

KerNet outperformed all the index-derived AI models. Based on the raw data of the entire cornea, KerNet was helpful for distinguishing clinically unaffected eyes in patients with AKC from normal eyes.

Ten-year Results after Conventional Corneal Cross-linking in Korean Patients with Progressive Keratoconus

Purpose: To evaluate the long-term effects of conventional corneal cross-linking in patients with progressive keratoconus.Methods: A total of 18 eyes of 9 patients diagnosed with keratoconus were analyzed retrospectively. One eye was diagnosed with progressive keratoconus and conventional corneal crosslinking was performed. The other eye was classified as non-progressive and remained untreated. All patients were assessed with best corrected visual acuity (BCVA), maximum keratometry (Kmax), mean keratometry (Kmean), corneal astigmatism, and corneal thickness. Clinical data were collected before the procedure and at 1, 3, 6 months and 1 to 10 years after the procedure.Results: The BCVA significantly improved from 0.63 ± 0.18 logarithm of the minimum angle of resolution (logMAR) to 0.46 ± 0.25 logMAR at 10 years after conventional corneal crosslinking (p = 0.027). The Kmax and Kmean decreased from 65.90 ± 9.43 D and 52.82 ± 5.16 D to 62.83 ± 8.16 D and 51.52 ± 5.18 D, respectively (p = 0.021, p = 0.028, respectively). Corneal astigmatism decreased from 6.97 ± 2.21 D to 5.53 ± 1.64 D (p = 0.008). The thinnest corneal thickness decreased from 435.11 ± 53.37 μm to 369.22 ± 64.00 μm 1 month after the procedure (p = 0.008), and gradually improved over time. At 10 years, the thinnest corneal thickness increased to 410.11 ± 61.32 μm (p = 0.097). In the untreated eyes, the mean keratometry significantly increased after 4 years of follow-up, but other factors did not change significantly. Although corneal opacity persisted for up to 10 years in 3 eyes of the treatment group, there was no significant difference of BCVA compared to the treated eyes without corneal opacity (p = 0.714).Conclusions: In patients with progressive keratoconus, conventional corneal crosslinking is a safe and effective procedure that suppresses long-term progression.

Pediatric Crosslinking: Current Protocols and Approach

Keratoconus (KC) is likely to be more aggressive in the pediatric population, with a higher risk of progression and visual loss. Several techniques have been proposed for corneal crosslinking (CXL) so far. The standard CXL (SCXL) technique, or the Dresden Protocol, originally developed by Wollensak et al., has been shown to be safe and effective in the pediatric KC group. With similar efficacy to the conventional method, the accelerated CXL (ACXL) protocols proposed a reduced UVA exposure time by increasing the intensity of UVA irradiation. Transepithelial CXL (TCXL), considered an "epithelium-on" method, emerged as a strategy to improve safety and reduce postoperative complications and discomfort. For thinner corneas, we can highlight the use of hypoosmolar riboflavin and new studies, such as contact lens-assisted CXL (CACXL), the epithelial-island CXL (EI-CXL), and the Sub400 protocol. In addition to the different protocols used, another factor that changes CXL results is the type of carrier used: dextran-based or hydroxypropyl methylcellulose-based (HPMC) riboflavin solutions. There are several ways to perform a CXL surgery, and it is still unclear which method is the safest and most effective in the pediatric group. This review of the literature in English, available in PubMed, provides an update on corneal CXL in the pediatric KC group, exploring the data on the techniques currently used and under investigation, including their advantages, efficacy, safety profiles, risks, and cost analyses.

Outcomes After Corneal Crosslinking for Keratoconus in Children and Young Adults

PURPOSE

The aim of this study was to assess the effect of corneal crosslinking on vision and keratometry in children and young adults with progressive keratoconus.

METHODS

A retrospective medical records review of patients aged 22 years or younger with keratoconus who underwent corneal crosslinking between January 2013 and November 2019 at Byers Eye Institute at Stanford University was conducted. Outcome measures included logarithm of the Minimum Angle of Resolution corrected distance visual acuity (CDVA); keratometry, including maximum keratometry (Kmax); pachymetry; and total wavefront aberration. Measurements were taken at baseline and at 12 and 24 months postoperatively.

RESULTS

Fifty-seven eyes of 49 patients aged 12 to 22 years were assessed. The mean preoperative CDVA was logarithm of the Minimum Angle of Resolution 0.38 ± 0.32 (20/48), with a mean postoperative CDVA of 0.29 ± 0.31 (20/39) and 0.31 ± 0.31 (20/41) at 12 and 24 months postoperatively, respectively. Compared with preoperative mean Kmax, there was an improvement of -0.8 diopters (D) to a mean postoperative Kmax of 59.1 ± 9.1 D at 12 months and -1.3 D to 59.7 ± 8.8 D at 24 months. Subanalysis excluding the second eye of patients who underwent bilateral crosslinking showed similar results. Linear mixed modeling showed significant improvement in Kmax at both 12 and 24 months postoperatively. Minimum central corneal thickness initially decreased but stabilized at 24 months after crosslinking. Total wavefront aberration remained stable.

CONCLUSIONS

Corneal crosslinking stabilizes, and in some cases improves, visual and corneal parameters in pediatric and young adult patients with keratoconus. The procedure is safe and well-tolerated and may prevent keratoconus progression in young patients.

Belin ABCD Progression Display Identifies Keratoconus Progression Earlier Than Conventional Metrics

PURPOSE

To compare the progression rate and time to progression determined using the Belin ABCD Progression Display (BAPD) with conventional metrics in patients with keratoconus (KC).

DESIGN

Retrospective comparison of progression assessment.

METHODS

Patients 18 years and older and 35 years and younger with at least 1 year of follow-up and 3 Pentacam (Oculus, Inc) visits were included in the study. Progression was evaluated by selecting either the first visit or the first 2 visits individually as the baseline on the BAPD, and the red gate was used to determine progression (variability in any A, B, and C parameters ≥95% CI or any 2 parameters ≥80% CI). An increase of ≥1 diopter in corneal astigmatism and curvature parameters and a ≥2% reduction in thickness parameters constituted progressive disease.

RESULTS

Two hundred seventy-seven eyes of 155 patients were included. The 2 baseline visit criteria identified the highest progression (n = 186 [67.2%]), followed by the single baseline visit (n = 158 [57%]), minimum corneal thickness (n = 114 [41.2%]), central corneal thickness (n = 111 [40.1%]), maximum keratometry (n = 76 [27.4%]), corneal astigmatism (n = 55 [19.9%]), back mean keratometry (n = 50 [18.1%]), and front mean keratometry (n = 31 [11.2%]) criteria. The median time to progression was shortest using the single baseline visit criterion (11 months), followed by the 2 baseline visits (11.6 months), minimum corneal thickness (12.1 months), maximum keratometry (12.3 months), corneal astigmatism (14.8 months), central corneal thickness (16.6 months), back mean keratometry (18.4 months), and front mean keratometry (24.4 months) criteria. In a subgroup analysis, progression could be identified 4 to 7 months earlier with the BAPD in eyes that were also progressive for maximum keratometry and central corneal thickness.

CONCLUSIONS

BAPD detects progression at a higher rate and earlier than conventional parameters.

Delayed Topographical and Refractive Changes Following Corneal Cross-Linking for Keratoconus

Background: The aim of this study was to analyze the long-term topographic and refractive outcomes of corneal cross-linking (CXL) in keratoconus. Methods: We used a retrospective observational study of patients with keratoconus who underwent CXL with a minimum follow-up of 5 years. Patients’ refractive and topography data (corrected distance visual acuity, sphere, cylinder, average and maximum keratometry, and corneal aberrations) were collected. Results: A total of 112 patients/150 eyes (mean age: 33.2 ± 10.7 years; range: 13−61) were included. The mean follow-up was 5.87 ± 1.35 years (range: 5−10). At the last follow-up visit, an improvement in CDVA, spherical and cylindrical refraction, average and steepest keratometry, and corneal aberrations were observed (p < 0.05), with the exception of trefoil. At the last visit, 49 (34.8%) and 31 (22.0%) eyes had an improvement beyond 1D in their spherical and cylindrical power, respectively, and 43 (28.7%) eyes had a flattening of their steepest keratometry. Progressive improvement over time was observed for spherical refraction; max and mean-K; as well as corneal RMS, total, high, coma, and spherical aberrations (p < 0.05). More severe disease at the baseline correlated with an improvement in corneal aberrations over time. Conclusions: In addition to a progressive improvement in refractive and keratometric indices, corneal aberrations also demonstrate a steady decline with long-term follow-up after CXL, which was more pronounced in more severe patients.