Risk factors for progression to penetrating keratoplasty in patients with keratoconus

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.

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.

Outcomes after corneal crosslinking treatment in paediatric patients with keratoconus

PURPOSE

This study aims to determine the efficacy and safety of accelerated corneal crosslinking in children with keratoconus.

METHODS

The study enrolled 64 patients aged 16 years or younger, each contributing one eye for a total of 64 eyes for analysis. Participants underwent an accelerated form of corneal cross-linking with 15 min of ultraviolet A irradiation at a rate of 7 mW/cm2, resulting in a cumulative energy dose of 5.4 J/cm2. The primary outcome measures were best corrected visual acuity (BCVA) and corneal tomography at 6 and 12 months post-intervention. Parameters assessed included BCVA, spherical and cylindrical refraction, keratometry (K1 and K2), maximum keratometry (Kmax) and thinnest corneal thickness (TCT). These metrics were documented preoperatively and then again at 6 and 12 months postoperatively. In addition, any ocular or systemic conditions related to keratoconus were recorded for each participant.

RESULTS

The results showed an improvement in BCVA at 12 months after surgery. K1 showed a decrease at both post-operative follow-ups while K2 remained constant throughout the observation period. Kmax showed a notable decrease at the 12 month postoperative follow-up. Although the TCT showed an initial decrease, it reached a stable state after 12 months of crosslinking. Refractive values remained stable at all subsequent examinations. Notably, no complications such as corneal opacity, non-healing epithelial defects or corneal infections occurred during the follow-up period. The most common ocular comorbidity was allergic conjunctivitis (34.4%).

CONCLUSION

The findings suggest that accelerated corneal crosslinking treatment is effective in slowing or halting the progression of keratoconus. Furthermore, there were no persistent overt complications observed at 12 months after the procedure.

The Keratectasia Volume (KEV) in Corneal Topography to Evaluate the Effect of Corneal Collagen Cross-linking in Pediatric Keratoconus

The study aimed to evaluate the keratectasia volume (KEV) before and after corneal cross-linking (CXL) in pediatric patients. This study included 40 eyes of 25 pediatric patients (10-19 years) undergoing standard CXL. The support vector machine (SVM) algorithm was applied to transform mass pixels in corneal topography into a three-dimensioned model to calculate the KEV. The KEV, Kmax, K1, K2, Kave, keratectasia area (KEA), and thinnest corneal thickness (TCT) were determined before CXL and at 3, 6, and 12 months after surgery. The correlation between KEV and other parameters (Kmax, TCT, max decentration, eccentricity, and so on) was calculated. The KEV was 4.75 ± 0.74 preoperatively and 4.43 ± 1.22 postoperatively at last follow-up (p < 0.002). There was strong positive correlation between the KEV and Kmax (r = 0.806, p < 0.0005). The preoperat ive KEV was 4.32 ± 0.69 in mild to moderate keratoconus (Kmax < 58D) and 5.27 ± 0.37 in advanced keratoconus (Kmax > 58D) (p < 0.0005, t-test). Postoperative KEV and K readings remained stable at the early stage, and the KEV showed a more drastic decreasing trend than Kmax at sixth month. Statistical significance was found in the KEV between preoperative and 6 months after surgery (p < 0.0005), but not in Kmax and other parameters. In 83.3% (15 eyes out of 18 eyes) of the eyes, the preoperative KEV was greater than 4.6 in patients with significant flattening after CXL. Compared with K readings, the KEV can be regarded as a more sensitive index to evaluate the postoperative morphological changes after CXL in pediatric patients.

Outcomes of two different treatment modalities in mild to moderate keratoconus

PURPOSE

To describe visual and refractive outcomes of intrastromal corneal ring segments (ICRS) and toric implantable collamer lenses (TICL) implantation in cases of mild and moderate keratoconus.

METHODS

A prospective descriptive interventional case series. 40 eyes were allocated into two groups. First group (20 eyes) was treated with corneal collagen crosslinking (CXL) 1 month after ICRS implantation and the second group was treated using TICL after 1 year of CXL.

RESULTS

Both groups showed statistically significant improvement in spherical equivalent, cylindrical refraction, uncorrected visual acuity (UCVA) and best corrected visual acuity (BCVA) over the follow-up period.

CONCLUSION

Both ICRS and TICL are effective in treatment of mid and moderate keratoconus with more predictable visual results with TICL.

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.

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.

Progression of keratoconus in children and adolescents

AIMS

To evaluate the rates of keratoconus progression and associated factors in eyes of children and adolescents.

METHODS

Retrospective, cohort study of individuals ≤18 years old at the time of keratoconus diagnosis and with at least 6 months of follow-up. Corneal tomography was performed using an Orbscan tomographer (Bausch & Lomb, Rochester, New York, USA) to determine whether progression occurred. Tomographic progression of keratoconus was defined as a change in any of the investigated parameters (keratometry values, K_MAX, maximum anterior or posterior elevation, central pachymetry, thinnest pachymetry) beyond the limits of repeatability.

RESULTS

148 eyes of 106 patients with a mean age of 15.2±2.5 years were studied over a mean follow-up period of 2.9±2.2 years. The overall rate of tomographic progression was 77.0% (114/148 eyes). Eyes that progressed had more advanced disease at presentation with higher anterior curvature (K_MAX55.4±6.3 vs 52.2±5.4 dioptres; p<0.01), posterior elevation (108.2±40.9 vs 86.3±35.6 µm; p<0.01) and lower central pachymetry measurements (442.1±56.7 vs 454.4±47.5 µm; p=0.01). Age at presentation, gender, atopy, documented eye rubbing, ethnicity and duration of follow-up were not significantly associated with progression in the multivariate analyses. There was a higher rate of bilateral progression if at least one eye had severe keratoconus (73.9%) compared with no severe keratoconus in either eye (36.8%; p=0.03).

CONCLUSIONS

A high rate of progression was identified in keratoconic eyes of children and adolescents. More advanced disease at initial presentation may increase the risk of further keratoconus progression.

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.

Detecting Keratoconus: Feasibility and Findings in Three Pediatric Risk Groups

PURPOSE

To investigate the utility of three corneal screening devices in three groups of children.

METHODS

This was a prospective study of patients with Trisomy 21 (group 1), patients with a first-degree relative with keratoconus (group 2), and control patients (group 3). Informed consent was obtained before testing with the Pentacam (Oculus Optikgeräte GmbH), Orbscan (Orbscan, Inc), and Ocular Response Analyzer (ORA) (Ametek Reichart Technologies). The ability to complete tests, the quality of results, and the corneal parameters obtained for each eye were recorded. A one-way analysis of variance test was used to compare the results between the three groups.

RESULTS

Fifty-four patients aged from 7 to 17 years (mean: 11.74 years) were enrolled between July 2014 and July 2016. The number of patients and the percentage of tests completed for groups 1, 2, and 3 were 12 (55%), 21 (87%), and 21 (88%), respectively. The Pentacam values by group were central corneal thickness of 524, 543, and 542 µm (P = .36); thinnest point of 498, 536, and 534 µm (P = .03); corneal front mean keratometry of 44.9, 43.2, and 43.2 (P = .01); and quality score of 1.42, 0.22, and 0.04 (P < .0001), respectively. Orbscan values by group were central corneal thickness of 493, 551, and 550 µm (P = .01) and thinnest point of 451, 536, and 538 µm (P < .0001), respectively. ORA values by group were corneal hysteresis of 10.6, 12.1, and 11.6 (P = .124); corneal resistance factor of 9.9, 11.8, and 11.6 (P = .03); and waveform score of 5.6, 7.6, and 7.3 (P < .0001), respectively.

CONCLUSIONS

Patients in group 1 completed fewer tests reliably and had thinner corneas and lower corneal resistance factors than patients in groups 2 and 3. Corneal tests used to evaluate adults for keratoconus may not be reliable for the evaluation of certain high-risk pediatric patients. [J Pediatr Ophthalmol Strabismus. 2022;59(2):94-101.].

The detection of keratoconus using novel metrics derived by anterior segment optical coherence tomography

PURPOSE

To determine through a feasibility study whether anterior and posterior corneal arc length and cross-sectional area measured using anterior segment ocular coherence tomography (AS-OCT) can distinguish between healthy and keratoconic corneas.

METHODS

Patients diagnosed with keratoconus along with healthy controls underwent AS-OCT. ImageJ was used to determine the central 6 mm anterior and posterior corneal arc lengths and cross-sectional areas. Each length and area was then divided into 1-mm segment and relative differences compared.

RESULTS

Twenty-five eyes from 15 patients with keratoconus, along with 25 eyes from 14 healthy controls were enrolled. There was a statistically significant difference in anterior and posterior corneal arc lengths as well as corneal cross-sectional area (p = 0.006, p = 0.005, p = 0.01, respectively). When selecting for the less advanced keratoconus eye, it was noted that posterior corneal arc length was longer in the paracentral temporal segment (1003 vs. 1010 µm, p = 0.04) and that greater change in corneal cross-sectional areas occurred between adjacent segments in less advanced keratoconus eyes.

CONCLUSION

AS-OCT is capable of reliably measuring corneal arc lengths in patients with keratoconus and healthy patients. Both anterior and posterior corneal arc lengths along with central cross-sectional areas are statistically different between healthy and keratoconus eyes.

Corneal Cross-Linking as Treatment in Pediatric Keratoconus: Comparison of Two Protocols

Introduction

Keratoconus is a progressive corneal disease commonly treated by collagen cross-linking (CXL). Accelerated protocols have recently become common. This study sought to compare the outcomes of accelerated and standard CXL in terms of visual acuity, keratometry, and tomographic parameters in pediatric population.

Methods

We retrospectively reviewed the files of pediatric patients who underwent standard and accelerated CXL for keratoconus in our hospital, between October 2014 and March 2018. Changes in uncorrected distance visual acuity (UCDVA), best corrected distance visual acuity (BCDVA), tomographic keratometry parameters (K_max, K_steep, K_flat, K_mean), and endothelial density count (EDC) were assessed before and at 6 and 12 months following treatment. The analysis included intergroup and intragroup comparisons.

Results

This study included 53 eyes (44 patients). Fourteen eyes were treated with standard CXL (S-CXL, 3 mW/cm², 30 min), while 39 underwent accelerated CXL (A-CXL, 9 mW/cm², 10 min). Intergroup comparison found insignificant differences between groups, with the exception of better results for UCDVA in the S-CXL group after 12 months (P = 0.03). In this study, there was no significant difference between the two protocols postoperatively in BCDVA, K_max, K_mean, pachymetry, or corneal astigmatism.

Conclusion

A-CXL is as safe and effective as S-CXL for stabilizing progressive keratoconus in pediatric population. Larger-sample-size studies with a longer follow-up time are required. Considering the long-term results of 9 mW A-CXL and its safety and efficacy profile, it should be preferred to S-CXL for reducing treatment time and improving patients' comfort.

Referral pattern and co-management of keratoconus patients in primary eye care: A survey of three European countries

PURPOSE

To explore current primary care practices in keratoconus management in Portugal and compare with previous reported results in two European countries (the UK and Spain), with a special focus on interdisciplinary collaboration and referral practice patterns.

METHODS

An online survey adapted to European professional practice was distributed (via newsletters) by the Portuguese Optometrist Association to explore keratoconus patient management and referral practice patterns among Portuguese practitioners.

RESULTS

Responses of 119 optometrists were compared with previous reported of 464 eye-care practitioners (126 in the UK and 338 in Spain). Most respondents (79% in Portugal, 71% in the UK and 76% in Spain; p = 0.31) had < 5 new keratoconus patients each year. No accepted referral criterion was found (p < 0.01) because small number of the respondents (14%) in Portugal referred out at initial diagnosis (50% in the UK and Spain); 32% referred out when progression was detected (17% in the UK and 30% in Spain); and a minority (10% in Portugal, 9% in the UK, and 6% in Spain) referred out when visual acuity was affected. A majority of respondents (83%) in Portugal reported no co-management with ophthalmologists (60% in the UK and 73% in Spain; p < 0.01).

CONCLUSION

The results of this study suggest that it is necessary to encourage interdisciplinary collaboration between practitioners to improve referral of patients with suspected keratoconus to an ophthalmology specialist to change the course of this disease, to reduce keratoconus progression and visual acuity impairment and to minimize the impact of this disease on patients' quality of life.

Outcomes of customized topographic guided epithelial debridement for corneal collagen cross-linking

PURPOSE

To evaluate the outcomes of corneal collagen cross-linking performed with customized epithelial debridement technique in progressive keratoconic corneas.

MATERIALS AND METHODS

Forty eyes of 40 patients were included in the study. We performed an ophthalmologic examination and recorded the uncorrected visual acuity, best corrected visual acuity (BCVA), central corneal thickness at the thinnest point (t-CCT), flat meridian keratometry (K1), steep meridian keratometry (K2), endothelial cell density (ECC), hexagonal cells (HEX), and coefficient of variation of cell areas (CV) measured preoperatively and at the 1st, 3rd, 6th and 12th months postoperatively.

RESULTS

The mean UCVA and BCVA were increased (p < 0.05). The mean flattest and steepest K readings were decreased (p < 0.05). The mean t-CCT decreased in the first months after treatment and increased after 6 months. The mean t-CCT was thicker at 12 months compared to pretreatment status (p < 0.05). The mean ECC and CV were not significantly different between follow-up intervals (p > 0.05). The mean HEX was statistically increased (p > 0.05).

CONCLUSIONS

Corneal collagen cross-linking performed with customized epithelial debridement technique is a successful alternative method for stopping the progression of keratoconus after 12 months of treatment.

Inter-rater Reliability and Repeatability of Manual Anterior Segment Optical Coherence Tomography Image Grading in Keratoconus

OBJECTIVES

To determine the repeatability of corneal measurements from anterior segment optical coherence tomography (AS-OCT) images using ImageJ software in healthy eyes compared with eyes with keratoconus.

METHODS

Anterior segment OCT images of 25 eyes from 14 healthy subjects and 25 eyes from 15 subjects with keratoconus between the ages of 20 and 80 years were evaluated. Two trained observers used ImageJ to measure the central corneal cross-sectional area and anterior and posterior corneal arc lengths. MedCalc statistical software was used to generate the intraclass correlation coefficient (ICC) and Bland-Altman plots (BAPs) for observer measurements.

RESULTS

Observer measurements of the central corneal cross-sectional area and anterior and posterior corneal arc lengths yielded an ICC >0.7. The ICC comparing the 3 parameters ranged from 0.75 to 0.84 for the control and 0.96 to 0.98 for the keratoconus group. No systematic proportional bias was detected by the BAPs. There were minimal differences between the 2 observer's measurements, with a mean of the difference of 0.3 mm2, 0 mm, and 0 mm, for the 3 measurements, respectively.

CONCLUSIONS

This study suggests that ImageJ software is a repeatable and reliable tool in the analysis of corneal parameters from AS-OCT images among patients with keratoconus and may be applicable to AS-OCT imaging protocol development, an area of active keratoconus research.

Accelerated versus Standard Corneal Cross-linking for Progressive Keratoconus in Syria

Purpose

To compare the outcomes of accelerated versus standard corneal cross-linking for the treatment of progressive keratoconus.

Methods

In this retrospective comparative study, 63 eyes of 40 patients with progressive keratoconus were divided into two groups; 27 eyes in group one were treated with an accelerated protocol (10 mW/cm 2 , 9 min) and 36 eyes in group two were treated with the standard method (3 mW/cm 2 , 30 min). Visual acuity, refraction, corneal topography, corneal tomography, and anterior and posterior corneal higher-order aberrations (HOAs) were assessed preoperatively and 18-30 months postoperatively.

Results

The LogMAR uncorrected and corrected distance visual acuity values were improved in both groups postoperatively. However, the improvement was significantly higher in group one (P < 0.05, all). The flattening in the anterior keratometry readings, flat K, steep K, and average K were significantly higher in group two (P < 0.001, all). The maximum anterior keratometry (AKf) values significantly decreased in both groups, whereas the maximum posterior keratometry (AKb) values increased. The reduction in the minimum corneal thickness (ThKmin) was significantly greater (36.49um) in group two, compared to 10.85um in group one. There was a significant increase in the posterior average keratometry, and a significant decrease in the posterior astigmatism, along 3 mm meridian in S-CXL (P = 0.03, P = 0.008, respectively), while the corresponding values showed no statistical significance in group one (P > 0.05). The anterior corneal trefoil was significantly reduced in group one (P = 0.002), whereas anterior total HOAs and coma were significantly improved in group two (P < 0.0014, all). The posterior corneal spherical aberration decreased significantly in group one (P = 0.02), while group two revealed significant reduction in the posterior trefoil values (P = 0.011). The change in the anterior maximum keratometry was significantly and positively correlated to the preoperative maximum keratometry in group two (P = 0.53, P = 0.003).

Conclusion

An accelerated cross-linking protocol using 10 mW/cm 2 for 9 min showed more visual improvement and less pachymetric reduction when compared to the standard protocol, however, anterior corneal flattening, posterior corneal steepening, and the change in the posterior astigmatism were significantly higher in the standard protocol; while corneal HOAs were improved in both protocols.

Prospective Clinical Study of Keratoconus Progression in Patients Awaiting Corneal Cross-linking

PURPOSE

Keratoconus progression should be treated with corneal cross-linking (CXL) in a timely manner. This study aimed to investigate patient factors associated with keratoconus progression between time of listing and at time of CXL.

METHODS

Prospective observational study at a tertiary center. Ninety-six eyes of 96 patients with keratoconus. Demographic, clinical, and tomographic parameters were analyzed to determine the risk factors for keratoconus progression. Analyzed tomographic indices included steepest keratometry, average keratometry, cornea thinnest point, index of surface variance, index of vertical asymmetry, keratoconus index, center keratoconus index, index of height asymmetry, and index of height decentration.

RESULTS

A total of 38 eyes (39.6%) were found to have keratoconus progression during an average waiting time of 153 ± 101 days. There were significant differences in preoperative tomographic parameters such as index of surface variance (111.3 ± 36.6 vs. 88.3 ± 31.8; P = 0.002), index of vertical asymmetry (1.1 ± 0.4 vs. 0.9 ± 0.4; P = 0.005), keratoconus index (1.31 ± 0.12 vs. 1.22 ± 0.11; P < 0.001), and index of height decentration (0.16 ± 0.07 vs. 0.11 ± 0.06; P = 0.015) between eyes that progressed and those that remained stable. There were no significant differences in steepest keratometry, average keratometry, cornea thinnest point, and center keratoconus index. Multivariate analysis did not reveal age, presence of atopy/atopic keratoconjunctivitis, eye rubbing, or waiting time to be a significant risk factor for progression; however, Maori ethnicity was a risk factor (odds ratio = 3.89; P = 0.02).

CONCLUSIONS

A significant proportion of eyes were found to be progressing while waiting for CXL. A risk stratification score for patients awaiting CXL may reduce the risk of progression.

Corneal transplantation for keratoconus in South Korea

This nationwide population-based study investigated the incidence rate of and risk factors for the progression to corneal transplantation in patients with keratoconus in South Korea using claims data from the Health Insurance Review and Assessment service. Among the entire South Korean population, 10,612 patients newly diagnosed with keratoconus between January 2010 and June 2015 were identified and included in the study. During the study period, 124 patients (1.17%) underwent corneal transplantation, with an average follow-up period of 2.97 ± 1.59 years. The incidence rate of corneal transplantation in patients with keratoconus was 4.46 cases per 1000 person-years. The rate of corneal transplantation for keratoconus was relatively low in South Korea compared to other countries. Multivariate Cox regression analysis revealed that male sex (HR 2.37; 95% CI 1.61–3.50; P < 0.001), severe atopic dermatitis (HR 2.32; 95% CI 1.02–5.28; P = 0.044), obstructive sleep apnea (HR 9.78; 95% CI 1.36–70.10; P = 0.023), and intellectual disability (HR 4.48; 95% CI 1.33–15.11; P = 0.016) significantly increased the risk of progression to corneal transplantation. In patients with keratoconus, male sex, severe atopic dermatitis, obstructive sleep apnea, and intellectual disability were associated with an increased risk of corneal transplantation.

Penetrating Keratoplasty Versus Deep Anterior Lamellar Keratoplasty in Children and Adolescents With Keratoconus

PURPOSE

To compare the outcomes of penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) for pediatric keratoconus.

DESIGN

Retrospective comparative interventional case series.

METHODS

This study included consecutive pediatric keratoconus cases (≤18 years of age) who received PK (n=45) or DALK (n=54) in 2 different time periods. Postoperative best spectacle-corrected visual acuity (BSCVA), refraction, and complications were compared between the study groups.

RESULTS

The mean follow-up was 83.3±46.1 and 63.3±45.6 months in the PK and DALK groups, respectively (P = .10). Postoperatively, BSCVA was 0.20±0.19 logMAR in the PK group and 0.26±0.19 logMAR in the DALK group (P = .11), with a BSCVA of ≥20/40 in 91.1% and 83.3% of eyes, respectively (P = .25). Two groups were comparable regarding postoperative refractive outcomes. Graft epitheliopathy and suture-associated complications were more commonly encountered after DALK, which was attributable to the effect of low-quality grafts on the clinical outcomes of DALK. Ten PK eyes (22.2%) and 9 DALK eyes (16.7%) experienced at least 1 episode of graft rejection within 5 years of corneal transplantation (P = .49). Rejection was reversible in 93.1% and 100% of episodes in the PK and DALK groups, respectively (P = .63). At the postoperative year 5, 95.6% of grafts in the PK group and 98.2% in the DALK group remained clear (P = .45).

CONCLUSION

No significant difference was observed in the outcomes between PK and DALK in pediatric keratoconus. Low-quality donor tissues in DALK increased the incidence of graft epithelial problems and suture-related complications as compared to PK.

Seven years follow-up of corneal cross-linking (CXL) in pediatric patients: Evaluation of treated and untreated eye

BACKGROUND

Retrospective cohort study evaluating long term keratoconus progression amongst cross-linking (CXL) treated pediatric patients in the treated and the fellow untreated eyes.

METHODS

Data on 60 eyes of 30 patients, 18 years old or younger, who underwent CXL in at least one eye was collected and analyzed. Follow-up measurements taken from the treated and untreated eye up to 7 years after CXL treatment, were compared to baseline measurements. Parameters included uncorrected distance visual acuity (UCDVA), best-corrected spectacle visual acuity (BCSVA), manifest refraction, pachymetry, corneal tomography, and topography.

RESULTS

Mean age of patients was 16 ± 2.1 years. For the treated eyes, during follow-up period mean UCDVA had improved (from 0.78 ± 0.22 at baseline to 0.58 ± 0.26 logMAR at 7 years; p = 0.13), as well as mean BCSVA (from 0.23 ± 0.107 at baseline to 0.172 ± 0.05 logMAR at 7 years; p = 0.37). The mean average keratometry showed a significant flattening (from 49.95 ± 4.04 to 47.94 ± 3.3 diopters (D); p < 0.001), However there was no change in the mean maximal keratometry. The mean minimal corneal thickness (MCT) showed a significant mild reduction of 26 µm (p = 0.006). Although statistically insignificant, the mean manifest cylinder was also reduced to 2D (p = 0.15). During the follow-up period, eight untreated eyes (26.6%) deteriorated and underwent CXL, while only one treated eye (3.33%) required an additional CXL.

CONCLUSION

CXL is a safe and efficient procedure in halting keratoconus progression in the pediatric population, the fellow eye needs to be carefully monitored but only a 25% of the patients will require CXL in that eye during a period of 7 years.

Corneal Cross-linking for Progressive Keratoconus in Patients Older Than 40 Years: Long-term Follow-up

PURPOSE

To assess the long-term efficacy and safety of epithelium-off corneal cross-linking according to the standard (Dresden) protocol (S-CXL) in patients with progressive keratoconus older than 40 years.

METHODS

Seventy-six eyes of 64 patients with a mean age of 46.4 ± 5.2 years were included. At baseline and after 6, 12, 24, 36, 48, 60, 72, 84, and more than 96 months (when available) after S-CXL, all patients were assessed with distance-corrected visual acuity (DCVA) and corneal topography and tomography with Pentacam HR (OCULUS Optikgeräte GmbH). A generalized linear model was used to compare the groups. Outcome measures were maximum keratometry, thinnest point, coma, spherical, and higher order aberrations, and ABC values. Fixed and random factors were age, gender, atopy, laterality, and group.

RESULTS

The mean follow-up time was 62.1 ± 40.1 months (range: 12 to 144 months). The main outcome of the study was the evidence that S-CXL was able to safely stop the progression of keratoconus in all patients with none requiring repeat CXL. The generalized linear model analysis showed no significant change in DCVA over time (P = 1.000), but atopy was negatively associated with DCVA (P = .030, B = -0.69). The generalized linear model also showed that CXL was able to induce a significant flattening demonstrated as reduction of maximum keratometry (P = .001, B = -0.35) and A value (P =.001, B = -0.015) of the ABC display. Similarly, coma aberration was reduced over time (P = .006, B = -0.005).

CONCLUSIONS

S-CXL was confirmed to be a safe and effective treatment for progressive keratoconus even after the age of 40 years, inducing a significant flattening of the cone. [J Refract Surg. 2021;37(5):338-342.].

Long term results of accelerated corneal collagen cross-linking in pediatric keratoconus

PURPOSE

To evaluate the long term visual, refractive, and corneal tomographic outcomes of epithelium-off accelerated corneal collagen cross-linking (ACXL) in the management of pediatric keratoconus (KC).

METHODS

This retrospective study included patients under 18 years old with progressive KC who underwent ACXL between 2012 and 2019 at Dicle University Hospital. Complete ophthalmic examination was performed including uncorrected distance visual acuity (UDVA), best spectacle-corrected distance visual acuity (CDVA), manifest refraction, and corneal tomography. Evaluations were performed preoperatively and at 6 months intervals postoperatively.

RESULTS

Forty-nine eyes of 49 patients were included in the study. The mean age of patients at the time of ACXL was 14.2 ± 1.8 (range: 9.5-17.3) years. Mean follow up was 4.61 ± 1.90 (range: 2.0-8.1) years. The mean LogMAR UDVA improved from 0.94 ± 0.41 to 0.81 ± 0.43, 0.69 ± 0.41, and 0.67 ± 0.33 after 1, 3, and 5 years respectively (p = 0.001). The mean LogMAR CDVA improved from 0.58 ± 0.36 to 0.46 ± 0.31, 0.34 ± 0.23, and 0.39 ± 0.27 after 1, 3, and 5 years respectively (p = 0.015). The mean refractive cylinder improved significantly from 6.01 ± 2.07 diopters (D) to 5.46 ± 1.87, 5.38 ± 2.18, and 5.02 ± 2.31 D after 1, 3, and 5 years respectively (p = 0.005). As compared to preoperative values, steep keratometry and maximum keratometry were not significantly different (p = 0.805 and 0.448, respectively) following ACXL, while flat keratometry significantly improved after ACXL (p = 0.012). Although central corneal thicknesses decreased significantly (p = 0.029), the decrease in thinnest corneal thickness was not statistically significant (p = 0.205).

CONCLUSION

Epithelium-off ACXL seems to be effective for halting KC progression with long term clinical benefits in pediatric patients.

Effect of Corneal Cross-linking versus Standard Care on Keratoconus Progression in Young Patients: The KERALINK Randomized Controlled Trial

PURPOSE

To examine the efficacy and safety of corneal cross-linking (CXL) for stabilization of progressive keratoconus.

DESIGN

Observer-masked, randomized, controlled, parallel-group superiority trial.

PARTICIPANTS

Sixty participants 10 to 16 years of age with progressive keratoconus, one eye of each deemed the study eye.

METHODS

The study eye was randomized to either CXL plus standard care or standard care alone, with spectacle or contact lens correction as necessary for vision.

MAIN OUTCOME MEASURES

The primary outcome was steep keratometry (K2) in the study eye as a measure of the steepness of the cornea at 18 months. Secondary outcomes included keratoconus progression defined as a 1.5-diopter (D) increase in K2, visual acuity, keratoconus apex corneal thickness, and quality of life.

RESULTS

Of 60 participants, 30 were randomized to CXL and standard care groups. Of these, 30 patients in the CXL group and 28 patients in the standard care group were analyzed. Mean K2 in the study eye 18 months after randomization was 49.7 D (standard deviation [SD], 3.8 D) in the CXL group and 53.4 D (SD, 5.8 D) in the standard care group. The adjusted mean difference in K2 in the study eye was -3.0 D (95% confidence interval [CI], -4.9 to -1.1 D; P = 0.002), favoring CXL. Adjusted differences between groups in uncorrected and corrected vision favored eyes receiving CXL: -0.31 logarithm of the minimum angle of resolution (logMAR; 95% CI, -0.50 to -0.11 logMAR; P = 0.002) and -0.51 logMAR (95% CI, -1.37 to 0.35 logMAR; P = 0.002). Keratoconus progression in the study eye occurred in 2 patients (7%) randomized to CXL compared with 12 patients (43%) randomized to standard care. The unadjusted odds ratio suggests that on average, patients in the CXL arm had 90% (odds ratio, 0.1; 95% CI, 0.02-0.48; P = 0.004) lower odds of experiencing progression compared with those receiving standard care.

CONCLUSIONS

CXL arrests progression of keratoconus in the majority of young patients. CXL should be considered as a first-line treatment in progressive disease. If the arrest of keratoconus progression induced by CXL is sustained in longer follow-up, particular benefit may be derived from avoiding a later requirement for contact lens wear or corneal transplantation.

Visual and Tomographic Outcomes of a 300° Arc-length ICRS Implantation in Moderate to Advanced Central Keratoconus

PURPOSE

To assess the outcomes of implanting a new 300° arc-length intrastromal corneal ring segment (ICRS) in moderate to advanced central hyperprolate keratoconus.

METHODS

Forty-two eyes with moderate to advanced central hyperprolate keratoconus were evaluated before and after implanting an inferior 300° ICRS (AJL Ophthalmic). The clinical measurements taken included manifest refraction, uncorrected (UDVA) and corrected (CDVA) distance visual acuity (logMAR scale), and corneal tomographic analysis (Sirius; Costruzioni Strumenti Oftalmici). Changes in the anterior and posterior corneal surfaces and the root mean square (RMS) for coma-like aberrations for a pupil size of 4.5 mm were evaluated. All examinations were performed before surgery and 6 months after surgery.

RESULTS

The mean UDVA improved from 1.12 ± 0.48 logMAR preoperatively to 0.73 ± 0.37 logMAR postoperatively (P < .0001). The mean CDVA changed from 0.33 ± 0.20 to 0.20 ± 0.11 logMAR (P < .0001). Postoperatively, the CDVA improved by two or more lines in 45.2% of the eyes and increased by one line in 19.04%, and none of the patients lost lines of CDVA. All of the anterior and posterior corneal tomographic parameters analyzed were significantly improved after surgery, except posterior flat keratometry, which remained unchanged. In 80.95% of the eyes, the postoperative mean keratometry was 50.00 diopters or less. The 6-month RMS for coma-like aberrations also declined significantly from 1.57 ± 0.68 to 1.06 ± 0.42 µm after surgery (P < .0001).

CONCLUSIONS

These results suggest that implanting a 300° arc-length ICRS is a safe and effective procedure for treating patients with moderate to advanced central hyperprolate keratoconus and clear cornea. [J Refract Surg. 2021;37(4):249-255.].

Efficacy of Conventional Versus Accelerated Corneal Cross-linking in Pediatric Keratoconus: Two-Year Outcomes

PURPOSE

To compare the efficacy and safety of accelerated corneal cross-linking (CXL) with conventional CXL in pediatric patients with keratoconus.

METHODS

Consecutive patients with keratoconus received either accelerated CXL (9 mW/cm² irradiance for 10 minutes) or conventional CXL (3 mW/cm² irradiance) for 30 minutes. Visual acuities (uncorrected [UDVA] and corrected [CDVA] distance visual acuity, logMAR), spherical error, cylindrical error, spherical equivalent, and keratometric values were recorded. Follow-up measurements were compared with baseline values.

RESULTS

The study enrolled 48 eyes: 22 eyes had accelerated CXL (mean age: 16.0 ± 1.7 years) and 26 eyes had conventional CXL (mean age: 15.7 ± 1.6 years). Compared with preoperative values, all mean keratometric values significantly improved in the accelerated CXL group (flat [K1]: Δ = -0.64 D, P < .0001, steep [K2]: Δ = -0.63 D, P = .009 and Kmax: Δ = -0.55 D, P = .028), but no significant changes were observed in the mean UDVA and CDVA. In the conventional CXL group, all mean keratometric values and CDVA significantly improved (K1: Δ = -0.65 D, P = .017, K2: Δ = -0.87 D, P = .006, Kmax: Δ = -1.47 D, P = .011). No significant changes were observed in refractive error in either CXL group. There were no significant differences in the keratometric readings, visual acuities, or refractive error between the two groups at the 2-year follow-up.

CONCLUSIONS

Both conventional and accelerated CXL protocols appear to be effective in stabilizing keratoconus progression in pediatric patients. Improved CDVA was also observed in the conventional CXL group. Accelerated CXL, with its advantage of shorter treatment duration, may be an alternative in pediatric patients. [J Refract Surg. 2020;36(4):265-269.].

Baseline Findings in the Retrospective Digital Computer Analysis of Keratoconus Evolution (REDCAKE) Project

PURPOSE

To present the baseline data for a large cohort of patients with keratoconus enrolled in the Retrospective Digital Computer Analysis of Keratoconus Evolution (REDCAKE) study.

METHODS

Eight centers contributed the Scheimpflug tomographical data for 906 patients with keratoconus, 743 measured with a Pentacam and 163 with a Galilei. The stage of keratoconus at baseline, the location of the reference points, minimum pachymetry (Pmin), and maximum keratometry (Kmax) were analyzed. The intereye asymmetry was evaluated for Kmax (anterior and posterior), Pmin, and keratoconus stage. Average maps and elevation profiles were calculated for each degree of keratoconus.

RESULTS

Keratoconus was more frequently diagnosed in men (73%) than in women (27%). At baseline, 500/1155 eyes (43%) presented with moderate to severe changes in the posterior surface, whereas moderate/severe changes were only found in 252 and 63 eyes when evaluating anterior surface and pachymetry, respectively. The location of Pmin was usually inferotemporal (94% OD and 94% OS), while the location of Kmax showed more variability and significantly higher distance from apex (P < 0.05). The keratoconus presentation was chiefly asymmetric for all the parameters studied. Clear differences between stages could be identified in the maps and elevation profiles.

CONCLUSIONS

The staging map set presented can be used as a graphical guidance to classify keratoconus stage. Keratoconus presented asymmetrically, and generally the posterior surface was more affected than the anterior surface or the thickness. Asymmetry is playing a role in KC detection. Although Pmin was almost invariably located inferotemporally, Kmax location showed higher variability and distance from the apex.

Impact of Scleral Contact Lens Use on the Rate of Corneal Transplantation for Keratoconus

PURPOSE

To evaluate the association of scleral contact lens (SCL) use on the risk for keratoplasty for people with keratoconus.

METHODS

The electronic health records of patients receiving eye care at the University of Michigan Kellogg Eye Center between August 1, 2012, and December 31, 2018, were reviewed. Patients with a diagnostic code of keratoconus or corneal ectasia, no previous history of keratoplasty, and for whom data were available for both eyes were included. Using a multivariable Cox regression model, associations between SCL use and keratoplasty were tested and adjusted for sociodemographic factors, maximum keratometry, and current contact lens (CL) use.

RESULTS

Two thousand eight hundred six eyes met the inclusion criteria. CL use in each eye was 36.2% with no CL, 7.2% soft, 33.9% rigid gas permeable (RGP), and 22.7% scleral. A total of 3.2% of eyes underwent keratoplasty. In the adjusted model, SCL or RGP CL use significantly lowered the hazard of undergoing keratoplasty (HR = 0.19, 95% confidence interval [CI] 0.09-0.39, P < 0.0001 and HR = 0.30, 95% CI 0.17-0.52, P < 0.0001, respectively) when compared with no CL use. Factors associated with increased risk of keratoplasty were black race as compared to white (HR = 1.87, 95% CI 1.10-3.16, P = 0.02), younger age (HR = 0.92 per 5-year increment, 95% CI 0.86-0.99, P = 0.032), and lower socioeconomic status (HR = 1.08 per 5-point increase in the Area Deprivation Index, 95% CI 1.03-1.13, P = 0.0008). Keratoplasty was not associated with sex, insurance, or maximum keratometry.

CONCLUSIONS

Physicians should maximize the use of scleral or RGP CL because patients who successfully use CL have almost one-fifth the risk of undergoing keratoplasty.

Long-Term Visual, Refractive and Topographic Outcomes of "Epi-off" Corneal Collagen Cross-Linking in Pediatric Keratoconus: Standard versus Accelerated Protocol

PURPOSE

To compare the visual, refractive and topographic outcomes of standard and accelerated corneal collagen cross-linking (CXL) in pediatric keratoconus patients.

METHODS

Prospective, comparative observational study on 68 eyes of 35 pediatric keratoconus patients (<18 years). Patients were classified into two groups, group (I) included 34 eyes and received standard "Epi-Off" CXL (3 mW/cm², 30 min.) and group (II) included 34 eyes and received accelerated "Epi-Off" CXL (9 mW/cm², 10 min.). Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), simulated keratometry (Sim K-1, Sim K-2, K-max, K-mean), cylindrical (CYL), pachymetry and Q-value were evaluated preoperatively and for 3 years postoperatively.

RESULTS

Postoperative UDVA and CDVA did not significantly change in both groups after 3 years. Postoperative SE was increased significantly in accelerated CXL (p=0.012) with no significant change in the postoperative cylinder in both procedures. Standard CXL had greater "significant" effect in decreasing Sim K-1, K-max and K-mean. The mean reduction in postoperative corneal pachymetry (at thinnest location) was significant in standard CXL (18.4 μm) (p=0.001). No significant change was noticed in postoperative Q-value.

CONCLUSION

Standard and accelerated CXL protocols are efficient in pediatric keratoconus management with better outcomes in the standard procedure.

Normative Values of Various Pentacam HR Parameters for Pediatric Corneas

PURPOSE

To provide a normative database of several Pentacam parameters for a healthy pediatric population.

METHODS

This was a retrospective study conducted at Al Watany Eye Hospitals, Cairo, Egypt. We explored the Pentacam HR database and collected the data of 432 normal right eyes of children and teenagers aged 3 to 18 years. The subjects were classified into the following 3 groups: group 1 (3-6 years, 17 eyes), group 2 (6-12 years, 126 eyes), and group 3 (12-18 years, 289 eyes). The parameters of the study cohort were compared with those of a healthy adult cohort.

RESULTS

The mean age of the study cohort was 13.5 (13.2-13.8) years. There were significant differences in the following indices among the 3 age groups: anterior chamber (depth and volume), curvature (index of height decentration, index of vertical asymmetry, and center keratoconus index), elevation (front and back elevations from the best fit toric ellipsoid), and pachymetric (minimum and average pachymetric progression indices and average Ambrosio relational thickness) parameters (P values 0.001, 0.001, 0.002, 0.04, <0.001, <0.001, 0.03, 0.02, 0.01, and 0.03, respectively).

CONCLUSIONS

There were significant differences in the normative values of several Pentacam indices between the pediatric and adult cohorts. Based on this finding, it is more credible to incorporate separate software cutoff values for pediatric patients. However, because there were no clinically significant differences in the parameters of the pediatric subgroups, there is no need to consider a separate cutoff value for each pediatric age range.

Three-year follow-up of accelerated transepithelial corneal cross-linking for progressive paediatric keratoconus

Purpose

To investigate the long-term safety and efficacy of accelerated transepithelial cornealcross-linking (ATE-CXL) in children with progressive keratoconus.

Methods

Fifty-three eyes of 41 paediatric patients (34 boys, 7 girls; mean age 14.81±1.96 years) undergoing ATE-CXL were enrolled in the study. Corrected distance visual acuity (CDVA) and manifest refraction were assessed preoperatively and 36 months postoperatively. Corneal keratometry, corneal thickness and posterior elevation were measured using Pentacam preoperatively and 1, 6, 12 and 36 months postoperatively. Pachymetry and epithelial thicknesses were measured using optical coherence tomography preoperatively and 6, 12, and 36 months postoperatively.

Results

Thirty-six months postoperatively, CDVA improved from 0.32±0.28 to 0.26±0.25 in logarithm of the minimum angle resolution (p=0.025). Maximum keratometry was 58.73±9.70 D preoperatively and 59.20±10.24, 58.28±9.33, 57.88±9.99 and 58.98±10.79 D at 1, 6, 12 and 36 months postoperatively throughout the 36-month follow-up period (p>0.05). Similarly, corneal central thickness, which was 492.42±33.83 µm postoperatively, also remained stable during the 36-month follow-up (p>0.05). Both posterior central elevation and posterior highest elevation were stable at 12 months after ATE-CXL (p>0.05), but increased at 36 months postprocedure (p<0.05). Corneal pachymetry and epithelial thicknesses remained stable throughout the follow-up period (p>0.05).

Conclusions

ATE-CXL is a safe and effective treatment in paediatric progressive keratoconus patients, leading to stable keratometry and corneal thickness throughout the 36-month follow-up.

Keratoconus Screening Among Myopic Children

Aim

To assess the topographic corneal changes and the incidence of keratoconus among children with high myopia.

Settings

It is a prospective study, in which 174 eyes of children with high myopia were studied in the period between August 2015 and June 2018.

Methods

All patients were examined to assess the refractive error and corneal examination using Scheimpflug camera to evaluate different corneal parameters.

Results

Studied children aged between 6 and 14 years (11.05±1.98). Males represented 54% of the cases (n=94). The mean spherical error was −7.75±2.97 ranging from −6 to −13.50D. The mean cylindrical error was −4.12±1.78D (−1 to −8). Regarding corneal examination, data recorded were those about maximum K reading (k_max), thinnest location, highest anterior and posterior elevation in 4mm zone, and higher-order corneal aberrations. Analysis of the obtained data revealed 16 eyes (9.2%) with keratoconus. These eyes were considered as a separate group and compared with the remaining eyes. There was significant difference in k_max (p= 0.03), anterior elevation, and posterior elevation (p=0.01 for both). Regarding myopia or astigmatism, there were no significant differences when compared with normal eyes. But high myopia with low astigmatism were found in five eyes of them (31.2%). The main statistically different aberrations were vertical coma (−2.04±0.99) (p=0.01) and spherical aberrations (−0.9±0.78) (p=0.02). Regarding gender, there were 11 eyes in boys (68.7%), and this was statistically significant (p=0.01). Vernal keratoconjunctivitis with frequent eye rubbing was found in 6 eyes (37.5%).

Conclusion

Children with high myopia irrespective of the degree of astigmatism may have corneal abnormalities which are more pronounced in cases with vernal keratoconjunctivitis. Corneal examination should be performed for highly myopic children to detect any corneal abnormality and to treat it as early as possible.

Safety and Efficacy of Corneal Cross-linking in Pediatric Patients with Keratoconus and Vernal Keratoconjunctivitis

PURPOSE:

The purpose of the study is to determine the safety and efficacy of corneal collagen cross-linking for keratoconus in pediatric patients with and without vernal keratoconjunctivitis (VKC).

METHODS:

This is a retrospective analysis of 89 eyes of 58 patients <18 years of age that underwent corneal collagen cross-linking for progressive keratoconus; inclusion criteria included a minimum of 2-year follow-up after cross-linking. The main outcomes measures included keratometry, pachymetry, vision, and complications following epithelial-off cross-linking with the Dresden protocol.

RESULTS:

VKC patients were more likely to be male; 81.6% of the non-VKC patients and 96.3% of VKC patients were male (P = 0.038). Comparing pretreatment to the 2-year follow-up, there was no statistically significant change in the mean steep or flat keratometry, corneal thickness, and uncorrected visual acuity or best spectacle-corrected visual acuity in either group. There were no statistically significant differences in the mean visual, keratometric, or adverse event outcomes between the two groups. The proportion exhibiting progression of ectasia at 2 years was 18.5% in the VKC group and 16.7% in the non-VKC group (P = 0.83).

CONCLUSIONS:

Cross-linking appears to be as safe and effective in pediatric patients with vernal keratoconjunctivits as in those without, with similar outcomes, adverse events, and progression of keratoconus after treatment. The proportion of patients exhibiting progression appears to be higher in pediatric patients than adults, and there is an association between male sex and diagnosis of VKC.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Demographic profile, clinical, and topographic characteristics of keratoconus patients attending at a tertiary eye center

Purpose

To evaluate the demographic profile, clinical, and topographic characteristics of keratoconus (KCN) patients attending at a subspecialty eye hospital in Tehran, Iran.

Methods

In this cross-sectional study, all patients who attended Noor Eye Hospital between March 2011 and March 2017 and had a diagnosis of KCN were identified, and the required number of patients was randomly selected. The following data were extracted from patient's records: age, sex, visual acuity, refraction, keratometry, pachymetry, and treatment procedures. The data of KCN laterality, severity, morphology, and cone location were also extracted by analyzing the corneal imaging maps.

Results

The records of 1080 eyes of 540 patients were evaluated. The mean age of the participants was 31.04 ± 8.54 years (range, 13–63 years), and 69.3% of the patients were male. The highest and lowest frequency of KCN was seen in the age group 20–30 years and above 50 years, respectively. Bilateral KCN was detected in 93.3% [95% confidence interval (CI): 91.68–94.75] of the subjects. 43.7% (95%CI: 32.88–54.48), 55.6% (95%CI: 44.73–66.38), and 0.8% (95%CI: 0.75–0.78) of the cases had nipple, oval, and globus cones, respectively. The cone was central in 52.1% (95%CI: 41.10–63.11), paracentral in 43.6% (95%CI: 36.13–51.04), and peripheral in 4.3% (95%CI: 00.76–7.86) of the cases. The frequency percentage of KCN according to severity was 15.2% (95%CI: 13.09–17.46), 56.4% (95%CI: 53.37–59.37), and 28.4% (95%CI: 25.75–31.21) for mild, moderate, and severe KCN, respectively. Among different parameters, only cone location had a significant association with age as the frequency of paracentral and peripheral cones increased with ageing (P = 0.002).

Conclusions

The mean age of KCN patients in our study was higher than similar studies in other Asian countries. KCN was bilateral in most cases with an oval morphology and central cone location. Most of the patients had moderate to severe KCN.

Interplay between hereditary and environmental factors to establish an in vitro disease model of keratoconus

Keratoconus (KC) is a bilateral corneal dystrophy and a multifactorial, multigenic disorder with an etiology involving a strong environmental component and complex inheritance patterns. The underlying pathophysiology of KC is poorly understood because of potential crosstalk between genetic-epigenetic variants possibly triggered by the environmental factors. Here, we decode the etiopathological basis of KC using genomic, transcriptomic, proteomic and metabolic approaches. The lack of relevant models that accurately imitate this condition has been particularly limiting in terms of the effective management of KC. Tissue-engineered in vitro models of KC could address this need and generate valuable insights into its etiopathology for the establishment of disease models to accelerate drug discovery.

Transepithelial versus epithelium-off corneal crosslinking for corneal ectasia

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

Pediatric keratoconus: a review of the literature

PURPOSE

To describe the epidemiology and prevalence, rates of progression, difference between adult and pediatric populations, and therapeutic approaches to pediatric keratoconus from documented literature.

METHODS

A literature search was done on PubMed using key words including pediatric keratoconus, children with keratoconus, adult keratoconus, penetrating keratoplasty, corneal cross-linking and intracorneal ring segments. The literature was reviewed and reported to explore the key epidemiological differences between the pediatric and adult population with regards to presentation and treatment options.

RESULTS

Pediatric keratoconus is more aggressive than adult keratoconus, which has been explained by structural differences in the cornea between both populations. High rates of progression were documented in pediatric populations. While corneal collagen cross-linking, intracorneal ring segments and penetrating keratoplasties have been used as therapies in the pediatric population, the literature overwhelmingly shows higher rates of failure and progression despite these measures as compared to adults.

CONCLUSION

Pediatric keratoconus is more aggressive than adult keratoconus, and current therapies used in adults may not be sufficient for the pediatric population.

Corneal Cross-Linking in Pediatric Patients: Evaluating Treated and Untreated Eyes-5-Year Follow-Up Results

PURPOSE

To evaluate the long-term results of corneal collagen cross-linking (CXL) for treatment of pediatric keratoconus and the long-term outcomes of the fellow untreated keratoconic eye in patients younger than 18 years old.

METHODS

A retrospective case analysis was performed on 88 eyes of 44 patients aged 18 years or younger, with keratoconus, who underwent CXL in at least 1 eye. Follow-up measurements, for the treated and untreated eye pair, taken up to 5 years after treatment, were compared with baseline values. Parameters included uncorrected distance visual acuity (UCDVA), best spectacle-corrected distance visual acuity (BCDVA), manifest refraction, pachymetry, and corneal topography and tomography.

RESULTS

Mean age of patients was 15.6 ± 2.1 years. For the treated eyes, during all years of follow-up, UCDVA improved significantly (from 0.83 ± 0.30 to 0.72 ± 0.28 logMAR; P = 0.01). Improvement in BCDVA was not statistically significant (from 0.28 ± 0.19 to 0.23 ± 0.15 logMAR; P = 0.06). The manifest cylinder showed a significant reduction (from 5.8 ± 3.6 to 4.3 ± 2.5 diopters; P = 0.006). There was no significant change in maximum keratometry. Average keratometry and corneal thickness reduced significantly (P = 0.009 and P = 0.002, respectively). Five patients had very mild corneal haze after CXL. For the fellow untreated eyes-during 5 years of follow-up, UCDVA showed a slight decrease that was not statistically significant. BCDVA, average keratometry, and maximum keratometry remained stable.

CONCLUSIONS

Our long-term follow-up study suggests that CXL is a safe procedure in the pediatric age, and there is no urgency in treating pediatric patients with keratoconus without proof of progression.

Accelerated versus standard corneal collagen cross-linking in pediatric keratoconus patients: 24 months follow-up results

PURPOSE

To compare the 24 month visual, refractive, topographic and aberrometric results of the accelerated and standard corneal collagen cross-linking (CXL) in pediatric keratoconus patients.

METHODS

87 eyes of 64 consecutive keratoconus patients under 18 years old with 24 month follow-up period following standard or accelerated CXL were included. 38 eyes received standard CXL (3 Mw/cm², 30 min), while 49 eyes had accelerated CXL (9 mW/cm², 10 min). Changes in the uncorrected (UCVA) and best corrected visual acuity (BCVA), spherical equivalent (SE), manifest astigmatism (MA), corneal topographic parameters, and corneal aberrations such as spherical aberration (SA), high order aberrations (HOAs), horizontal and vertical coma were evaluated. Corneal haze was graded and progression rate was assessed.

RESULTS

The difference between baseline and 24 months postoperative UCVA, BCVA, SimK (keratometry)-1, SimK-2, Kmax, and the corneal aberrations were not significantly different between the two groups (p > 0.05 for all). The mean reduction in thinnest corneal pachymetry from baseline to 24 months after CXL was higher in accelerated CXL group (p = 0.007). The progression rate was 13.1% in standard and 16.3% in accelerated group (p = 0.754). There were no differences in the grade of corneal haze between the two groups (p = 0.249). No complications were observed in the both groups.

CONCLUSION

The 24 month results of accelerated and standard CXL revealed that, the efficacy and safety of accelerated CXL were the same with standard CXL in pediatric keratoconus patients. As being a rapid procedure, accelerated CXL appears to be more benefical for pediatric patients.

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

PURPOSE

To assess the 10-year follow-up efficacy and safety of riboflavin ultraviolet A-induced cross-linking (CXL) in a population of pediatric patients aged 18 years and younger with progressive keratoconus (KC).

METHODS

The prospective longitudinal cohort study included 62 eyes of 47 keratoconic patients undergoing epithelium-off CXL who completed 10-year follow-up. The surgical procedure was performed in all patients according to the Siena (Dresden modified) protocol. Evaluation included uncorrected distance visual acuity, corrected distance visual acuity, Scheimpflug corneal tomography, and optical coherence tomography demarcation line measurement. Follow-up measurements taken up to 10 years after treatment were compared with baseline values, and statistical analysis was performed using a 2-tailed paired sample Student t test.

RESULTS

Uncorrected distance visual acuity and corrected distance visual acuity improved from 0.45 to 0.23 logarithm of the minimum angle resolution (P = 0.0001) and from 0.14 to 0.1 logarithm of the minimum angle resolution (P = 0.019). KC stability was recorded after 10 years of follow-up in nearly 80% of the patients. The overall 10-year follow-up progression rate was 24% including 13 eyes of 9 patients with Kmax progression over 1 diopter and 2 eyes of 2 patients who underwent corneal grafting.

CONCLUSIONS

The study demonstrates the ability of CXL to slow down KC progression in pediatric patients, improving functional performance. Long-term stability may be correlated with CXL-induced delay in corneal collagen turnover and with spontaneous age-related KC stabilization. A 24% regression rate could be contemplated in the patients who were aged 15 years and younger at the time of inclusion in the treatment protocol.