Corneal collagen cross-linking for treating keratoconus

Early findings in a randomised controlled trial on crosslinking protocols using isoosmolar and hypoosmolar riboflavin for the treatment of progressive keratoconus

PURPOSE

To present baseline characteristics and to present the perioperative corneal thickness during corneal crosslinking (CXL) treatment for progressive keratoconus and to describe how the addition of sterile water (SW) efficaciously can maintain the corneal thickness. The treatment efficacy will be evaluated when the 1-year follow-up is complete.

METHODS

A randomised clinical study using epithelium-off CXL with continuous UVA irradiation (9 mW/cm2) and two kinds of riboflavin solutions: (i) isoosmolar dextran-based riboflavin (n = 27) and (ii) hypoosmolar dextran-free riboflavin (n = 27).

INCLUSION CRITERIA

progressive keratoconus with an increase in maximum keratometry value (Kmax) of 1.0 dioptre (12 months) or 0.5 dioptres (6 months). Corneae thinner than 400 μm were also included.

OUTCOME PARAMETERS

Perioperative corneal thickness and the effect of adding SW.

RESULTS

Seventy-four per cent of the patients in the isoosmolar group and 15% in the hypoosmolar group required the addition of SW, which effectively maintained a corneal thickness of 400 μm in all cases during CXL. The addition of SW was primarily needed during the irradiation procedure and not the preoperative soaking period.

CONCLUSIONS

Especially during the CXL irradiation phase, isoosmolar riboflavin causes a significant dehydrating effect leading to corneal thinning during CXL. The customised addition of SW is efficacious in maintaining the corneal thickness during CXL and could increase the safety of the procedure.

Repeat corneal collagen cross-linking after failure of primary cross-linking in keratoconus

BACKGROUND

Primary corneal collagen cross-linking (CXL) stabilises 96% of progressive keratoconus. There is limited evidence for the treatment of choice when this fails. We present 10 years of repeat CXL and compare with our published experience of primary CXL to (1) identify perioperative risk factors of primary CXL failure and (2) demonstrate the safety and efficacy of repeat CXL.

METHODS

Patients undergoing repeat accelerated epithelium-off CXL at St James's University Hospital, Leeds, UK January 2012-August 2022 were identified through electronic patient record, and compared with a previously published cohort of primary CXL patients at the same site.

RESULTS

Twenty-one eyes underwent repeat CXL. The mean interval between primary and repeat CXL treatments was 47.1 months (SD 22.5). Twenty (95%) eyes stabilised after repeat CXL at a mean follow-up of 29.9 months. These cases were compared with 151 cases of primary CXL from our previous study. Patients failing primary CXL were significantly younger (21.3 years (SD 7.0) vs 26.7 years (SD 6.5), p=0.0008). Repeat CXL and primary CXL induced a similar amount of flattening of Kmax (-1.2 D (SD 3.9) vs -0.7 D (SD 4.4), p=0.22). A small, but clinically insignificant, improvement in best-corrected visual acuity was found in the repeat CXL group (-0.04 (SD 0.17) vs -0.05 (SD 0.13), p=0.04). No complications of repeat CXL were noted.

CONCLUSION

Younger age may be associated with failure of primary CXL. Repeat CXL is an effective and safe treatment for progressive keratoconus despite primary CXL.

Artificial intelligence for detecting keratoconus

BACKGROUND

Keratoconus remains difficult to diagnose, especially in the early stages. It is a progressive disorder of the cornea that starts at a young age. Diagnosis is based on clinical examination and corneal imaging; though in the early stages, when there are no clinical signs, diagnosis depends on the interpretation of corneal imaging (e.g. topography and tomography) by trained cornea specialists. Using artificial intelligence (AI) to analyse the corneal images and detect cases of keratoconus could help prevent visual acuity loss and even corneal transplantation. However, a missed diagnosis in people seeking refractive surgery could lead to weakening of the cornea and keratoconus-like ectasia. There is a need for a reliable overview of the accuracy of AI for detecting keratoconus and the applicability of this automated method to the clinical setting.

OBJECTIVES

To assess the diagnostic accuracy of artificial intelligence (AI) algorithms for detecting keratoconus in people presenting with refractive errors, especially those whose vision can no longer be fully corrected with glasses, those seeking corneal refractive surgery, and those suspected of having keratoconus. AI could help ophthalmologists, optometrists, and other eye care professionals to make decisions on referral to cornea specialists. Secondary objectives To assess the following potential causes of heterogeneity in diagnostic performance across studies. • Different AI algorithms (e.g. neural networks, decision trees, support vector machines) • Index test methodology (preprocessing techniques, core AI method, and postprocessing techniques) • Sources of input to train algorithms (topography and tomography images from Placido disc system, Scheimpflug system, slit-scanning system, or optical coherence tomography (OCT); number of training and testing cases/images; label/endpoint variable used for training) • Study setting • Study design • Ethnicity, or geographic area as its proxy • Different index test positivity criteria provided by the topography or tomography device • Reference standard, topography or tomography, one or two cornea specialists • Definition of keratoconus • Mean age of participants • Recruitment of participants • Severity of keratoconus (clinically manifest or subclinical) SEARCH METHODS: We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register), Ovid MEDLINE, Ovid Embase, OpenGrey, the ISRCTN registry, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP). There were no date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 29 November 2022.

SELECTION CRITERIA

We included cross-sectional and diagnostic case-control studies that investigated AI for the diagnosis of keratoconus using topography, tomography, or both. We included studies that diagnosed manifest keratoconus, subclinical keratoconus, or both. The reference standard was the interpretation of topography or tomography images by at least two cornea specialists.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the study data and assessed the quality of studies using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. When an article contained multiple AI algorithms, we selected the algorithm with the highest Youden's index. We assessed the certainty of evidence using the GRADE approach.

MAIN RESULTS

We included 63 studies, published between 1994 and 2022, that developed and investigated the accuracy of AI for the diagnosis of keratoconus. There were three different units of analysis in the studies: eyes, participants, and images. Forty-four studies analysed 23,771 eyes, four studies analysed 3843 participants, and 15 studies analysed 38,832 images. Fifty-four articles evaluated the detection of manifest keratoconus, defined as a cornea that showed any clinical sign of keratoconus. The accuracy of AI seems almost perfect, with a summary sensitivity of 98.6% (95% confidence interval (CI) 97.6% to 99.1%) and a summary specificity of 98.3% (95% CI 97.4% to 98.9%). However, accuracy varied across studies and the certainty of the evidence was low. Twenty-eight articles evaluated the detection of subclinical keratoconus, although the definition of subclinical varied. We grouped subclinical keratoconus, forme fruste, and very asymmetrical eyes together. The tests showed good accuracy, with a summary sensitivity of 90.0% (95% CI 84.5% to 93.8%) and a summary specificity of 95.5% (95% CI 91.9% to 97.5%). However, the certainty of the evidence was very low for sensitivity and low for specificity. In both groups, we graded most studies at high risk of bias, with high applicability concerns, in the domain of patient selection, since most were case-control studies. Moreover, we graded the certainty of evidence as low to very low due to selection bias, inconsistency, and imprecision. We could not explain the heterogeneity between the studies. The sensitivity analyses based on study design, AI algorithm, imaging technique (topography versus tomography), and data source (parameters versus images) showed no differences in the results.

AUTHORS' CONCLUSIONS

AI appears to be a promising triage tool in ophthalmologic practice for diagnosing keratoconus. Test accuracy was very high for manifest keratoconus and slightly lower for subclinical keratoconus, indicating a higher chance of missing a diagnosis in people without clinical signs. This could lead to progression of keratoconus or an erroneous indication for refractive surgery, which would worsen the disease. We are unable to draw clear and reliable conclusions due to the high risk of bias, the unexplained heterogeneity of the results, and high applicability concerns, all of which reduced our confidence in the evidence. Greater standardization in future research would increase the quality of studies and improve comparability between studies.

Early findings in a prospective randomised study on three cross-linking treatment protocols: interruption of the iontophoresis treatment protocol

PURPOSE

To present the outcome of the interrupted iontophoresis-assisted treatment arm in an ongoing randomised clinical trial (NCT04427956).

METHODS

A randomised clinical study of corneal cross-linking (CXL) using continuous UV-A irradiation at a rate of 9 mW/cm2 and three different types of riboflavin and riboflavin delivery mode: (1) iso-osmolar dextran-based riboflavin (epithelium-off), (2) hypo-osmolar dextran-free riboflavin (epithelium-off) and (3) iontophoresis-assisted delivery of riboflavin (epithelium-on) for the treatment of progressive keratoconus. Inclusion criteria were an increase in the maximum keratometry value (Kmax) of 1.0 dioptre over 12 months or 0.5 dioptre over 6 months. The primary outcome in evaluating treatment efficacy was Kmax. Recently presented stratified detection limits were used post hoc to confirm the enrolment of patients with truly progressive keratoconus and in the assessment of the need for re-CXL.

RESULTS

Thirteen patients had been randomised to iontophoresis-assisted CXL when the treatment arm was interrupted; two patients dropped out. Of the remaining 11 patients, 7 were deemed as having truly progressive disease according to the more recent stratified detection limits. The disease continued to progress in three patients according to the original definition (increase in Kmax≥1 D), necessitating re-CXL with epithelium-off CXL. This progression was confirmed by post hoc analysis using the stratified detection limits for progression.

CONCLUSIONS

The iontophoresis-assisted CXL protocol failed to halt further disease progression in 27% of the patients. The failure rate increased to 38% when considering only the patients deemed to have truly progressive disease using the stratified detection limits.

Screening a Panel of Topical Ophthalmic Medications against MMP-2 and MMP-9 to Investigate Their Potential in Keratoconus Management

Keratoconus (KC) is a serious disease that can affect people of any race or nationality, although the exact etiology and pathogenic mechanism are still unknown. In this study, thirty-two FDA-approved ophthalmic drugs were exposed to virtual screening using docking studies against both the MMP-2 and MMP-9 proteins to find the most promising inhibitors as a proposed computational mechanism to treat keratoconus. Matrix metalloproteinases (MMPs) are zinc-dependent proteases, and MMP inhibitors (MMPIs) are usually designed to interact with zinc ion in the catalytic (CAT) domain, thus interfering with enzymatic activity. In our research work, the FDA-approved ophthalmic medications will be investigated as MMPIs, to explore if they can be repurposed for KC treatment. The obtained findings of the docking study suggest that atenolol and ampicillin are able to accommodate into the active sites of MMP-2 and MMP-9. Additionally, both exhibited binding modes similar to inhibitors used as references, with an ability to bind to the zinc of the CAT. Molecular dynamic simulations and the MM-GBSA binding free-energy calculations revealed their stable binding over the course of 50 ns. An additional pharmacophoric study was carried out on MMP-9 (PDB ID: 1GKC) using the co-crystallized ligand as a reference for the future design and screening of the MMP-9 inhibitors. These promising results open the door to further biological research to confirm such theoretical results.

Crosslinking vs. Observation in Fellow Eyes of Keratoconus Patients

Purpose

To evaluate whether unilateral crosslinking (CXL) and conservative follow-up of the fellow eye is an acceptable management strategy in patients with keratoconus (KC).

Methods

Seventy-nine fellow eyes of KC subjects that initially underwent unilateral CXL were included. Thirty fellow eyes ultimately received CXL (group 1) whereas 49 fellow eyes were followed (group 2). Best spectacle corrected visual acuity (BSCVA) and corneal tomographic parameters were collected in all eyes preoperatively and at the last follow-up.

Results

Subjects who received CXL in the fellow eye (group 1) were younger than subjects who did not (group 2, p=0.026). Group 1 eyes had higher baseline K1 (p=0.026), K2 (p=0.006), Km (p=0.01), and Kmax (p=0.002) compared to group 2 eyes. Amongst the 49 naïve fellow eyes (group 2), 19 eyes showed evidence of progression. Progressing naïve eyes had higher baseline K1, K2, Km, and Kmax (p < 0.01); progressors also had thinner pachymetry at the pupil, apex, and thinnest point (p < 0.01). Baseline values of K1 ≥ 43.5 Diopter (D), K2 > 45.1D, Km > 44.3D, K_max > 47.9D, astigmatism > 1.4D, pachymetry at the pupil <475 μm, and thinnest pachymetry <478 μm were tentative predictors of progression in the naïve fellow eye.

Conclusions

Unilateral CXL with vigilant follow up of the fellow eye may be an acceptable management strategy in a subset of KC eyes.

Assessing corneal cross-linking with reverberant 3D optical coherence elastography

SIGNIFICANCE

Corneal cross-linking (CXL) is a well-known procedure for treating certain eye disorders such as keratoconus. However, characterization of the biomechanical changes in the cornea as a result of this procedure is still under active research. Specifically, there is a clinical need for high-resolution characterization of individual corneal layers.

AIM

A high-resolution elastography method in conjunction with a custom optical coherence tomography system is used to track these biomechanical changes in individual corneal layers. Pre- and post-treatment analysis for both low-dose and high-dose CXL experiments are performed.

APPROACH

A recently developed elastography technique that utilizes the theory of reverberant shear wave fields, with optical coherence tomography as the modality, is applied to pig corneas ex vivo to evaluate elasticity changes associated with corneal CXL. Sets of low-dose and high-dose CXL treatments are evaluated before and after treatments with three pairs of pig corneas per experiment.

RESULTS

The reverberant three-dimensional (3D) optical coherence elastography (OCE) technique can identify increases in elasticity associated with both low-dose and high-dose CXL treatments. There is a notable graphical difference between low-dose and high-dose treatments. In addition, the technique is able to identify which layers of the cornea are potentially affected by the CXL procedure and provides insight into the nonlinearity of the elasticity changes.

CONCLUSIONS

The reverberant 3D OCE technique can identify depth-resolved changes in elasticity of the cornea associated with CXL procedures. This method could be translated to assess and monitor CXL efficacy in various clinical settings.

[Histological changes in keratoconus and wound healing after corneal cross-linking]

BACKGROUND

Keratoconus is classified as a corneal ectasia and is a multifactorial disease. In those affected, mostly adolescent patients visual deterioration occurs due to the development of irregular astigmatism. Treatment by corneal cross-linking (CXL) has been indicated in progressive disease for several years.

OBJECTIVE

To present the pathophysiology and histological changes in keratoconus as well as wound healing processes after CXL and their potential complications.

MATERIAL AND METHODS

Histological changes in keratoconus as well as wound healing processes after CXL and their potential complications are presented based on histological examination of corneal specimens with keratoconus with and without a condition after CXL. Relevant literature and own data are analyzed and discussed.

RESULTS

Besides inflammatory processes, atopic and genetic dispositions play a role in the development of keratoconus. The histological characteristics of keratoconus include changes in the epithelium, Bowman's layer and stroma. Wound healing processes after CXL include healing of the surface epithelium and transient loss of keratocytes and nerve fibers.

CONCLUSION

Keratoconus shows characteristic histopathological changes, such as epithelial irregularities, stromal thinning and breaks of Bowman's layer, whereas the endothelium and Descemet's membrane remain unchanged (apart from cases of corneal hydrops). After CXL wound healing processes can be followed primarily in vivo by confocal microscopy. Complications after CXL are rare. Persistent loss of keratocytes can be clinically manifested as a visually relevant scar.

Progressive corneal ectatic disease in pregnancy

Pregnancy influences ocular changes which may exacerbate existing or develop new pathology. This review summarises the existing evidence on the association between pregnancy and progressive keratoconus or iatrogenic keratectasia. Ten online databases were searched systematically. Eligible studies were published in English and reported objective ophthalmic outcomes for women with evidence of (i) a new diagnosis of keratoconus, (ii) keratoconus progression or (iii) iatrogenic keratectasia following refractive surgery; during or within one year of pregnancy. Strength of evidence was assessed using the Oxford Centre for Evidence-Based Medicine levels of evidence. Seventeen articles have reported 33 peripartum women with new-onset or progressive ectasia, evident by signs of corneal hydrops or protrusion (n = 8); steepening on topography imaging (n = 20); a mean decline in best corrected visual acuity by +0.20 logMAR (95% CI -0.01 to +0.40, n = 23); a mean increase in maximum keratometry by 2.18 D (95% CI 1.44 to 2.91, n = 42); a mean decline in spherical equivalent refraction by -1.33 D (95% CI -1.73 to -0.93, n = 41); and a mean increase in astigmatism by -1.61 D (95% CI -2.46 to -0.75, n = 19). Pregnancy is associated with progressive ectasia in some women including those with previously stable keratoconus, or a history of laser-assisted in situ keratomileusis surgery or no history of corneal ectasia. This review highlights the heterogeneity in limited existing evidence, the need for a standardised definition of ectasia progression and further prospective studies for clinical guidelines. Closely monitoring women at risk may assist in early intervention with collagen cross-linking and prevent peripartum vision loss.

The resilience of the inner ear-vestibular and audiometric impact of transmastoid semicircular canal plugging

Background

Certain cases of superior semicircular canal dehiscence or benign paroxysmal positional vertigo can be treated by plugging of the affected semicircular canal. However, the extent of the impact on vestibular function and hearing during postoperative follow-up is not known.

Objective

To evaluate the evolution of vestibular function and hearing after plugging of a semicircular canal.

Methods

Six patients underwent testing before and 1 week, 2 months, and 6 months after plugging of the superior or posterior semicircular canal. Testing included caloric irrigation test, video Head Impulse Test (vHIT), cervical and ocular Vestibular Evoked Myogenic Potentials (VEMPs) and audiometry.

Results

Initially, ipsilateral caloric response decreased in all patients and vHIT vestibulo-ocular reflex (VOR) gain of each ipsilateral semicircular canal decreased in 4/6 patients. In 4/6 patients, postoperative caloric response recovered to > 60% of the preoperative value. In 5/6 patients, vHIT VOR gain was restored to > 85% of the preoperative value for both ipsilateral non-plugged semicircular canals. In the plugged semicircular canal, this gain decreased in 4/5 patients and recovered to > 50% of the preoperative value. Four patients preserved cervical and ocular VEMP responses. Bone conduction hearing deteriorated in 3/6 patients, but recovered within 6 months postoperatively, although one patient had a persistent loss of 15 dB at 8 kHz.

Conclusion

Plugging of a semicircular canal can affect both vestibular function and hearing. After initial deterioration, most patients show recovery during follow-up. However, a vestibular function loss or high-frequency hearing loss can persist. This stresses the importance of adequate counseling of patients considering plugging of a semicircular canal.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10693-5.

An inter-day assessment of the ABC parameters in the evaluation of progressive keratoconus

The progression of keratoconus is commonly determined by comparing the results of corneal tomographic measurements on different occasions. However, investigations on the repeatability of measurements are commonly performed within the same day, thus not taking the inter-day variation into account. The effect of keratoconus disease severity on the measurement error is also seldom considered. In this post hoc investigation, the parameters A, B and C in the Belin ABCD Progression Display were evaluated in relation to disease severity in intra-day and inter-day measurements. Four consecutive measurements were performed on 61 patients with keratoconus on the same day (intra-day). In another cohort, four consecutive measurements were obtained and then repeated 3 days later in 25 patients with keratoconus and 25 healthy controls (inter-day). The results suggest that the diagnosis of disease progression would benefit from inter-day measurements, and the stratification of the parameters A and C according to disease severity. It is also recommended that tomographic systems such as the Pentacam HR be modified to allow the comparison of both single measurements and the mean of replicate measurements of the parameters used in the assessment of progression of keratoconus.

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.

Keratoconus detection of changes using deep learning of colour-coded maps

Objective

To evaluate the accuracy of convolutional neural networks technique (CNN) in detecting keratoconus using colour-coded corneal maps obtained by a Scheimpflug camera.

Design

Multicentre retrospective study.

Methods and analysis

We included the images of keratoconic and healthy volunteers’ eyes provided by three centres: Royal Liverpool University Hospital (Liverpool, UK), Sedaghat Eye Clinic (Mashhad, Iran) and The New Zealand National Eye Center (New Zealand). Corneal tomography scans were used to train and test CNN models, which included healthy controls. Keratoconic scans were classified according to the Amsler-Krumeich classification. Keratoconic scans from Iran were used as an independent testing set. Four maps were considered for each scan: axial map, anterior and posterior elevation map, and pachymetry map.

Results

A CNN model detected keratoconus versus health eyes with an accuracy of 0.9785 on the testing set, considering all four maps concatenated. Considering each map independently, the accuracy was 0.9283 for axial map, 0.9642 for thickness map, 0.9642 for the front elevation map and 0.9749 for the back elevation map. The accuracy of models in recognising between healthy controls and stage 1 was 0.90, between stages 1 and 2 was 0.9032, and between stages 2 and 3 was 0.8537 using the concatenated map.

Conclusion

CNN provides excellent detection performance for keratoconus and accurately grades different severities of disease using the colour-coded maps obtained by the Scheimpflug camera. CNN has the potential to be further developed, validated and adopted for screening and management of keratoconus.

Crosslinking und Keratokonus

Ein Keratokonus führt zu einer progressiven Vorwölbung und Verdünnung der Hornhaut. Um dies aufzuhalten, kann ein Crosslinking durchgeführt werden. Dabei ist eine Behandlung nach dem „Dresdener Protokoll“ eine effektive und sichere Behandlungsmöglichkeit, aber auch zahlreiche neue Anwendungsprotokolle (akzeleriertes Crosslinking, transepitheliales Crosslinking) und sogar weitere Indikationen (refraktive Eingriffe, infektiöse Keratitis) wurden in den letzten Jahren veröffentlicht.

[Crosslinking and Keratoconus]

Keratoconus leads to a progressive protrusion and thinning of the cornea. In order to stop this, corneal crosslinking can be performed if the progression of the disease is proven. Crosslinking according to the "Dresden protocol" includes abrasion of the corneal epithelium, application of riboflavin eye drops and irradiation with UV-A light of an intensity of 3 mW/cm² for 30 minutes. The efficacy has been shown in several prospective randomized studies. One of the more recent developments is accelerated crosslinking, which allows a shorter irradiation time. On the other hand, the possibility of transepithelial crosslinking was presented, which does not require an abrasion of the cornea. This should reduce the occurrence of postoperative pain. The range of indications has also been expanded. Corneal crosslinking is used for post-LASIK keratectasia as well. It is also being considered for use in infectious keratitis. Topographically controlled crosslinking can likewise be used to try to positively influence the refractive power of the cornea. The risks of crosslinking include the occurrence of pain, haze or scarring, endothelial cell damage and, rarely, the occurrence of keratitis.

Predictors of progression in untreated keratoconus: a Save Sight Keratoconus Registry study

AIMS

We set out to identify risk factors for progression in untreated keratoconus patients from 34 centres across Australia, New Zealand, Spain and Italy.

METHODS

Patients were divided into 'progressors' and 'stable' patients for each clinical parameter: visual acuity (VA), steepest keratometry (maximum keratometry (Max-K)) and thinnest corneal thickness (TCT). Primary outcomes were the proportion of eyes with sustained progression in VA, Max-K or TCT within 3 years. Secondary outcomes included predictors of progression.

RESULTS

There were 3994 untreated eyes from 2283 patients. The proportion of eyes with VA, Max-K and TCT progression at 1 year were 3.2%, 6.6% and 3.1% respectively. Factors associated with VA loss were higher baseline VA (HR 1.15 per logMAR line increase in VA; p<0.001) and steeper baseline Max-K (HR 1.07 per 1D increase; p<0.001). Younger baseline age was associated with Max-K steepening (HR 0.96 per year older; p=0.001). Thicker baseline TCT, steeper baseline Max-K and younger baseline age were associated with TCT thinning: (HR 1.08 per 10 µm increase in TCT; p<0.001), (HR 1.03 per 1D increase; p=0.02) and (HR 0.98 per year younger; p=0.01), respectively.

CONCLUSIONS

Steeper Max-K and younger age were the most clinically useful baseline predictors of progression as they were associated with worsening of two clinical parameters. Every 1D steeper Max-K was associated with a 7% and 3% greater risk of worsening VA and thinning TCT, respectively. Each 1 year younger was associated with a 4% and 2% greater risk of steepening Max-K and thinning TCT, respectively.

Femtosecond laser-assisted stromal keratophakia for keratoconus: A systemic review and meta-analysis

PURPOSE

Femtosecond lasers have revived the possibility of stromal keratophakia or tissue additive keratoplasty, a technique originally introduced by Prof. Jose Ignacio Barraquer in the 1960s. The surgical technique offers a unique solution to treat keratoconus. In the current study, we reviewed and performed a meta-analysis of the clinical outcomes of the femtosecond laser-assisted stromal keratophakia in the treatment of keratoconus.

METHODS

This is a systematic review and meta-analysis of the estimated outcome difference between pre- and post-lenticule implantations.

RESULTS

A total of related 10 studies were found in the literature. No studies reported adverse events, such as persistent haze or graft rejection, at last patients' visits. We further narrowed down the article selection in accordance to our inclusion criteria to report the composite outcomes (9 studies) and meta-analysis (4 studies). In the composite analysis, we demonstrated that lenticule implantation in keratoconus and post-LASIK ectasia patients appeared to expand the stromal volume of the thin corneas, flattened the cones, and significantly improved uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) and spherical equivalent (SE). The meta-analysis showed that the random estimated UCVA, BCVA, SE and mean keratometry (K_m) differences following the lenticule implantation was -0.214 (95% CI: -0.367 to 0.060; p = 0.006), -0.169 (-0.246 to 0.091; p < 0.001), -2.294 D (-3.750 to -0.839 D; p = 0.002), and 2.909 D (0.805 to 5.012 D; p = 0.007), respectively.

CONCLUSIONS

Femtosecond laser-assisted stromal keratophakia is a feasible technique to correct the refractive aberrations, expand corneal volume and regularize corneal curvature in patients with keratoconus. However, there is a need to standardize the technique (e.g., whether to crosslink or not or to use convex or concave lenticules) and to formulate a mathematical model that accounts for the long-term epithelial thickness changes and stromal remodeling to determine the shape or profile of the lenticules, in order to improve the efficacy of the keratophakia further.

Corneal parameters 18 Months following collagen cross-linkage treatment (CXL) for keratoconus in western Saudi Arabia: A prospective cohort study

Introduction

keratoconus is a common disease in the general population, with prevalence ranging up to 200 per 100 000 with a reported increase in Saudi Arabia. Collagen Cross-Linkage is now an established treatment in isolation and in conjunction with other modalities for managing keratoconus. Our aim is to evaluate using a cohort study the impact of the treatment over a course of 18 months.

Methods

To evaluate the impact of 18 months after collagen cross-linkage treatment and its determinants in eyes with keratoconus in Western Saudi Arabia. A one-armed prospective cohort study design on 45 patients with Stage I, II, III and IV keratoconus who were treated by Collagen Cross-Linkage modality was developed at our institute between 2018 and 2019 to establish the success rate of corneal ectasia stabilization of the disease.

Results

Demographic data and grades of keratoconus (Amsler - Krumiech classification) at presentation were correlated to changes in corneal parameters 18 months after CXL compared to that at presentation. Stage I, II, III and IV keratoconus were 13, 14, 2 and 16 eyes respectively. The study showed that the K max significantly declined (P = 0.05) while spherical equivalent refractive status changed from median −1.5D to −2.27D (P = 0.002). Meanwhile, Central corneal thickness significantly reduced (P = 0.001).

Conclusion

CXL can prove to be efficient in the treatment of Keratoconus and more studies should study ways to improve and implement this treatment plan to such patients.

•

Keratoconus prevalence has been increasing in Saudi Arabia and the world.

•

Studying treatment procedures of the disease is important to determine the best course of action.

•

Collagen Cross-Linkage Treatment is a treatment option that showed variation of success rate in the literature.

Safety, Efficacy, and Predictive Factors of Conventional Epithelium-Off Corneal Crosslinking in the Treatment of Progressive Keratoconus

Purpose

To report predictive factors of outcome of conventional epithelium-off corneal crosslinking (CXL) in the treatment of progressive keratoconus.

Methods

This is a monocentric observational retrospective study conducted at Eye and Ear International Hospital, Lebanon. All patients with progressive keratoconus who underwent CXL between January 2008 and January 2016, with minimal 3-years follow-up were included. Primary treatment outcomes were maximum keratometry (K max), best-corrected distance visual acuity (CDVA), and failure. Failure was defined as an increase of 1.00 diopters (D) or more in K max and/or an increase of 0.1 logMAR or more in CDVA and conversion to corneal transplantation. Statistical analysis was done to identify predictors of treatment success. Univariate and multivariate analyses were performed to determine the correlations between baseline parameters and outcomes, and an equation for predicting K max and CDVA was created.

Results

156 eyes of 102 patients were enrolled. The mean age was 23.85 ± 6.52 years. Failure occurred in 31 eyes (19.87%). Gender and thinnest pachymetry did not have any impact on postoperative outcomes. Concerning the CDVA outcome, multivariate analysis showed that a better preoperative CDVA was associated with higher improvement in CDVA, and higher baseline K max and higher posterior mean K were associated with a worse outcome CDVA. Regarding postoperative K max, a higher baseline K max, a worse baseline CDVA, and a younger age were associated with less flattening postoperatively.

Conclusion

CXL is a safe and effective method in treating progressive keratoconus. However, the clinical benefits can differ among patients, and in our series, a nonnegligible number of cases show a continued progression of their ectasia. Further studies to identify predictors of postoperative progression prior to the procedure could help sort out good responders to treatment.

Reliability of the Evidence Addressing Treatment of Corneal Diseases: A Summary of Systematic Reviews

Importance

Patient care should be informed by clinical practice guidelines, which in turn should be informed by evidence from reliable systematic reviews. The American Academy of Ophthalmology is updating its Preferred Practice Patterns (PPPs) for the management of the following 6 corneal diseases: bacterial keratitis, blepharitis, conjunctivitis, corneal ectasia, corneal edema and opacification, and dry eye syndrome.

Objective

To summarize the reliability of the existing systematic reviews addressing interventions for corneal diseases.

Data Source

The Cochrane Eyes and Vision US Satellite database.

Study Selection

In this study of published systematic reviews from 1997 to 2017 (median, 2014), the Cochrane Eyes and Vision US Satellite database was searched for systematic reviews evaluating interventions for the management of any corneal disease, combining eyes and vision keywords and controlled vocabulary terms with a validated search filter.

Data Extraction and Synthesis

The study classified systematic reviews as reliable when each of the following 5 criteria were met: the systematic review specified eligibility criteria for inclusion of studies, conducted a comprehensive literature search for studies, assessed risk of bias of the individual included studies, used appropriate methods for quantitative syntheses (meta-analysis) (only assessed if meta-analysis was performed), and had conclusions that were supported by the results of the systematic review. They were classified as unreliable if at least 1 criterion was not met.

Main Outcomes and Measures

The proportion of systematic reviews that were reliable and the reasons for unreliability.

Results

This study identified 98 systematic reviews that addressed interventions for 15 corneal diseases. Thirty-three of 98 systematic reviews (34%) were classified as unreliable. The most frequent reasons for unreliability were that the systematic review did not conduct a comprehensive literature search for studies (22 of 33 [67%]), did not assess risk of bias of the individual included studies (13 of 33 [39%]), and did not use appropriate methods for quantitative syntheses (meta-analysis) (12 of 17 systematic reviews that conducted a quantitative synthesis [71%]). Sixty-five of 98 systematic reviews (66%) were classified as reliable. Forty-two of the 65 reliable systematic reviews (65%) addressed corneal diseases relevant to the 2018 American Academy of Ophthalmology PPPs; 33 of these 42 systematic reviews (79%) are cited in the 2018 PPPs.

Conclusions and Relevance

One in 3 systematic reviews addressing interventions for corneal diseases are unreliable and thus were not used to inform PPP recommendations. Careful adherence by systematic reviewers and journal editors to well-established best practices regarding systematic review conduct and reporting might help make future systematic reviews in eyes and vision more reliable.

Association between keratoconus disease severity and repeatability in measurements of parameters for the assessment of progressive disease

BACKGROUND

Progressive keratoconus can lead to severely impaired vision, but there is currently no consensus on the definition of progressive disease. Errors in the measurement of the parameters commonly used to establish progressive disease were evaluated in an attempt to determine the limits at which a true change in the values can be detected. The possible association between measurement error and disease severity was also investigated to evaluate the need for limits based on disease severity.

METHODS

Sixty-one eyes were studied in 61 patients with keratoconus. Four replicate measurements were made in each patient using a Scheimpflug-based tomographic system (denoted the PC) and an auto-keratometer (denoted the AK). The repeatability coefficient, i.e., the level below which differences between two measurements are found in 95% of paired observations, was calculated. Patients were further divided into three groups based on disease severity (parameter magnitude).

RESULTS

Increasing magnitude of all the keratometric parameters investigated was significantly associated with increasing measurement errors, and thus worse repeatability. The maximum keratometry value (Kmax) was the least repeatable parameter (1.23 D, 95% CI 1.11-1.35 D) and showed the strongest association between parameter magnitude and measurement error. The repeatability coefficient ranged between 0.32 and 1.62 D, depending on disease severity. The most repeatable parameter was the flattest central keratometry value (K1), measured with the PC (0.51 D, 95% CI 0.46-0.56 D) and the AK (0.54 D, 95% CI 0.48-0.59 D). K1 showed the weakest association between parameter magnitude and measurement error. The repeatability coefficient for K1 ranged between 0.40 and 0.54 D when using the PC, and between 0.34 and 0.70 D when using the AK in the three groups.

CONCLUSIONS

The association between the magnitude of the keratometric parameters and their measurement errors suggests that limits should be based on disease severity to ensure reliable detection of progressive keratoconus. Further studies are, however, required.

Corneal Collagen Cross-Linking in the Stabilization of Keratoconus

BACKGROUND

Keratoconus is a slowly progressive ectatic deformity of the cornea with a prevalence of 200 to 400 cases per 100 000 persons. The cornea is thinner than normal and irregularly warped; irregular astigmatism and myopia result. Riboflavin-UVA crosslinking (collagen cross-linking) makes corneal tissue more rigid through a photochemical effect and can stop the progression of the disease.

METHODS

This review is based on relevant publications retrieved by a selective search in Medline, as well as on meta-analyses, Cochrane Reviews, and reports of national and international health care institutions.

RESULTS

Pertinent randomized controlled trials (RCTs) have shown that cross-linking prevents the progression of keratoconus to a statistically significant extent, as determined by measurement of topographic parameters. In the largest RCT to date (fol- low-up of 100 eyes for three years), the maximal corneal refractive power increased by 1.75 ± 0.38 diopters in the control group and decreased by -1.03 ± 0.19 diopters in the cross-linking group (p <0.001). This was also the only trial in which data were reported on the patient-relevant endpoint of uncorrected visual acuity, which mildly improved in the cross-linking group (-0.15 ± 0.06 logMAR, p = 0.009). Serious complications of cross-linking are known to date only from a few reports of individual cases. Cohort studies with follow-up times of up to ten years have shown that the condition can continue to progress after cross-linking, especially in younger patients.

CONCLUSION

Cross-linking is the first available treatment for keratoconus that can improve the natural course of the disease.

A randomised, controlled, observer-masked trial of corneal cross-linking for progressive keratoconus in children: the KERALINK protocol

INTRODUCTION

The KERALINK trial tests the hypothesis that corneal cross-linking (CXL) treatment reduces the progression of keratoconus in comparison to standard care in patients under 17 years old. KERALINK is a randomised controlled, observer-masked, multicentre trial in progressive keratoconus comparing epithelium-off CXL with standard care, including spectacles or contact lenses as necessary for best-corrected acuity.

METHODS AND ANALYSIS

A total of 30 participants will be randomised per group. Eligible participants aged 10-16 years with progressive keratoconus in one or both eyes will be recruited. Following randomisation, participants will be followed up 3-monthly for 18 months. The effect on progression will be determined by K₂ on corneal topography. The primary outcome measure is between-group difference in K₂ at 18 months adjusted for K₂ at baseline examination. Secondary outcomes are the effect of CXL on (1) keratoconus progression, (2) time to keratoconus progression, (3) visual acuity, (4) refraction, (5) apical corneal thickness and (6) adverse events. Patient-reported effects will be explored by questionnaires.

ETHICS AND DISSEMINATION

Research Ethics Committee Approval was obtained on 30 June 2016 (ref: 14/LO/1937). Current protocol: V.5.0 (08/11/2017). Study findings will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

European Union clinial trials register (EudraCT) 2016-001460-11.

Intrastromal corneal ring segments for treating keratoconus

BACKGROUND

Keratoconus is a degenerative condition of the cornea that profoundly affects vision and vision-specific quality of life. The axial cornea thins and protrudes, resulting in irregularity and, eventually, scarring of the cornea. There are multiple options available for treating keratoconus. Intrastromal corneal ring segments are small, crescent-shaped plastic rings that are placed in the deep, peripheral corneal stroma in order to flatten the cornea. They are made of polymethylmethacrylate (PMMA). The procedure does not involve corneal tissue nor does it invade the central optical zone. Intrastromal corneal ring segments are approved for use when contact lenses or spectacles are no longer adequate.

OBJECTIVES

To evaluate the effectiveness and safety of intrastromal corneal ring segments as a treatment for keratoconus.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2018, Issue 1); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature Database (LILACS); ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not implement any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 25 January 2018.

SELECTION CRITERIA

Two review authors independently assessed records from the electronic searches to identify randomized controlled trials (RCTs). Disagreements were resolved by discussion.

DATA COLLECTION AND ANALYSIS

We planned for two authors to independently review full-text reports, using standard methodological procedures expected by Cochrane.

MAIN RESULTS

We found no RCTs comparing intrastromal corneal ring segments with spectacles or contact lenses.

AUTHORS' CONCLUSIONS

In the absence of eligible RCTs to review, no conclusions can be drawn.

[Complications and postoperative therapeutic strategies in cross-linking]

CLINICAL ISSUE

The reduced corneal mechanical stability in keratoconus and similar collagen diseases can lead to a progressive and irregular corneal shape and decrease of visual acuity.

DIAGNOSTICS

A progression of keratectatic diseases can be shown with corneal topography.

TREATMENT

Keratoconus can be treated by photo-oxidative cross-linking of the corneal collagen. In order to achieve a high absorption of irradiation energy in the cornea, riboflavin at a concentration of 0.1% and UVA light at a wavelength of 370 nm corresponding to the relative maximum absorption of riboflavin (vitamin B2) are used. Evidence for corneal cross-linking are the increase of biomechanical stiffness, the increased resistance against enzymatic degradation, a higher shrinkage temperature, a lower swelling rate and an increased diameter of collagen fibers. The currently available data demonstrate that the therapeutic cross-linking procedure is safe when respecting the important theoretical and clinical parameters and that a progression of the keratoconus can be avoided. In 80% of cases an average levelling of the curvature of approximately 2 dpt can be achieved, which leads not only to stabilization but also to an increase in visual acuity of approximately 1.2 lines.

ASSESSMENT

In a Cochrane review from 2015 publications about complications and results were reviewed. Complication rates ranged from 1-10% depending on the initial situation, comorbidities and stage of the keratoconus. The most important complications are early epithelial wound healing problems as well as extremely rare perforations.

PRACTICAL RECOMMENDATIONS

Corneal cross-linking is a well-established and safe procedure but is not free of complications.

Repeated Same-Day Versus Single Tomography Measurements of Keratoconic Eyes for Analysis of Disease Progression

Purpose:

Corneal tomography is used to assess progression of keratoconus and to direct clinical decisions regarding corneal cross-linking. The purpose of this study was to analyze the variability of repeated Scheimpflug-tomography (Pentacam Classic; Oculus, Wetzlar, Germany) measurements of keratoconic eyes in a clinical setting and to assess the validity of such measurements as a clinical decision-making tool.

Methods:

Eighty keratoconic eyes of 45 patients (age range 16–32 years) were examined at baseline and after follow-up periods of 3 to 6 months using 3 consecutive tomography measurements at each visit. Minimum corneal thickness and anterior sagittal curvature map parameters were studied [simulated keratometry (K) astigmatism (SimKast); maximum simulated K-reading (SimKmax); average SimK (SimKave); maximum K-readings on the 3-mm (Kmax3) and 5-mm (Kmax5) rings; and maximum K-reading (Kmax)].

Results:

When comparing the first measurements at the first and second visits, respectively, 9% to 20% of eyes were classified as progressive depending on which parameter was chosen. Using the average of 3 consecutive measurements at each visit, 5% to 19% of eyes were classified as progressive. An increase in the SD of 3 consecutive measurements of SimKast (SD_SimKast) at the first visit of 1 diopter makes true progression of keratoconus 3.6 times more likely (odds ratio = 3.6; 95% confidence interval: 0.846–16.027; area under the curve = 0.70).

Conclusions:

The approach used to analyze progression in keratoconus, that is, single versus repeated measurements, may confer a great impact on the decision to perform corneal cross-linking treatment or not.

[Riboflavin UVA crosslinking in progressive keratoconus]

In patients with keratoconus, a progressive, ectatic disease of the cornea, the shape of the cornea is continuously changing leading to a reduction in visual acuity by progressive myopia and more and more (irregular) astigmatism. The symptomatic treatment consists of the prescription of glasses or special gas-permeable rigid contact lenses. Corneal tomography is generally used for diagnosis. After initial diagnosis of keratoconus, regular tomographic follow-ups should be performed. If clinically significant progression is found and confirmed by repeated measurements, riboflavin UVA collagen crosslinking should be offered to the patients. The aim of riboflavin UVA collagen crosslinking is to halt the progression of the disease to avoid further complications. The therapeutic principle is a combined effect of the photosensitizer riboflavin and UVA light. This stiffening effect of the corneal tissue halts the progression of keratoconus. The efficacy of this treatment has been demonstrated in various randomized, controlled trials.

Corneal densitometry after accelerated corneal collagen cross-linking in progressive keratoconus

PURPOSE

To analyze changes in corneal densitometry 3 months after accelerated corneal collagen cross-linking (CXL) measured with Scheimpflug tomography.

METHODS

In this study we reviewed charts and anterior segment data of patients who had undergone accelerated pulsed epithelium-off CXL (30 mW/cm² for 4 min, 8 min total radiation time) for treatment of progressive keratoconus in the Department of Ophthalmology, Goethe University, Frankfurt, Germany. Visual, topographic, pachymetric and densitometric data were extracted before surgery and at the 3-month follow-up. Corneal densitometry measurements from different corneal layers and zones obtained using Scheimpflug tomography (Pentacam HR, Oculus).

RESULTS

The study investigated 12 eyes of 12 patients. The anterior (120 μm) stromal layer within the 0.0 to 2.0 mm and 2.0 to 6.0 mm concentric zones showed a significant elevation of mean densitometry 3 months post-surgery (P = 0.045; P = 0.015) compared to baseline. A mean stromal demarcation line was apparent at a depth of 203.00 μm ± 13.53 (SD). After accelerated CXL, no change in mean corrected distance visual acuity (LogMAR) was observed but a thinning of the cornea measured by a significant reduction in central pachymetry (μm).

CONCLUSION

Accelerated CXL results in an increase in corneal densitometry, particularly in the anterior stromal layer within the two central concentric zones (0.0 to 2.0 mm and 2.0 to 6.0 mm) of the cornea at 3 months postoperatively. The changes in corneal densitometry of the anterior stromal layer did not correlate with postoperative visual acuity or central pachymetry.

Recent Innovations in Collagen Corneal Cross-linking; a Mini Review

Background:

The introduction of corneal cross-linking (CXL) with ultraviolet-A (UVA) and Riboflavin photosensitizer (Vit B₂) from Seiler et al., revolutionized the treatment of Keratoconus and other corneal ectatic diseases.

Today, the commonly known epithelium off Dresden protocol is in clinical use for the last 15 years with great success and regarded by many as the golden standard.

Methods:

With several studies demonstrating its simplicity, efficacy and safety this revolutionary method, paved the way for new therapies and strategies in the treatment of corneal ectatic diseases and changed our understanding in corneal biomechanics. Recent scientific and technological advances enabled the creation of various modifications of the initial CXL protocol and the formation of new ones.

Conclusion:

This work highlights the recent advances of CXL, such as the role of oxygen, higher fluence and shorter irradiation times as well as the various clinical applications and updates of this method.

Updates on corneal collagen cross-linking: Indications, techniques and clinical outcomes

Purpose

To review the historical background and basic principles of collagen cross-linking, to bring together the data regarding the outcomes and complications of collagen cross-linking and finally to explore the efficacy and safety of new variations of this technique.

Methods

A literature review was performed using PubMed and Scopus. The following keywords were used for literature search: cross linking, crosslinking, cross-linking, keratoconus, keratectasia.

Results

In contrast to traditional treatment modalities for keratoconus (KCN), this new technique addresses the progression of the disease. Several clinical studies have been conducted to assess the efficacy of corneal collagen cross-linking (CXL) in the last decade. The results were promising as collagen cross-linking showed significant improvement in visual acuity and keratometric values. Moreover, initial results show that it is a safe procedure with few reported complications.

Conclusion

CXL is an emerging treatment method in ophthalmology that offers the possibility to effectively treat progressive KCN.

Current optometric practices and attitudes in keratoconus patient management

PURPOSE

To compare the current optometric practices and attitudes in the management of keratoconus patients in the UK and Spain.

METHODS

An online survey (adapted to optometric practices) was distributed via a newsletter emailed by various professional organizations in the UK and Spain.

RESULTS

Four hundred and sixty-four practitioners (126 in the UK; 338 in Spain) who prescribed gas permeable GP contact lenses (CLs) more than once per month (54.8% of UK practitioners and 28.1% of practitioners in Spain; p<0.01) responded to the questionnaire. A combination of multiple factors is considered necessary in the keratoconus detection (79.4% in the UK, 75% in Spain; p=0.68), and the use of classification criteria is considered relevant (67.5% in the UK, 70.7% in Spain; p=0.49). There is a high consensus on the consideration that GP CL fitting is more difficult in keratoconus (79.4% in the UK, 80.5% in Spain; p=0.79) requiring more diagnostic lenses (3.2±1.4 and 3.4±1.2 in the UK and Spain, respectively; p=0.72) than are necessary for healthy eyes. Using corneal topography is uncommon from both countries (38.1% in the UK, 59.8% in Spain; p<0.01), with a similar ophthalmologist referral pattern (at initial diagnosis, 50% in both the UK and Spain; p=1.00). Few cases of co-management with ophthalmologists were noted (no co-management reported by 60.3% in the UK and 72.8% in Spain, p=0.01).

CONCLUSION

This study provides initial observations and evidence regarding keratoconus management by optometrists in the UK and Spain and shows similarity in the professional practices and attitudes of practitioners in these two countries.

Assessing Progression of Keratoconus and Cross-linking Efficacy: The Belin ABCD Progression Display

Several methods have been described to both evaluate and document progression in keratoconus and to show efficacy of cross-linking, however, there are no consistent generally accepted parameters. Modern corneal tomography, including both anterior and posterior elevation and pachymetric data can be used to screen for ectatic progression, be employed to detect earlier change and additionally to show efficacy of new treatment modalities, such as crosslinking.

To describe specific quantitative values that can be used as progression and efficacy determinants, the normal noise measurements of the three parameters used in the ABCD keratoconus classification (corneal thickness at the thinnest point, anterior and posterior radius of curvature taken from the 3.0 mm optical zone centered on the thinnest point), were determined. Values were obtained from both a normal population and a known keratoconic population. The 80 and 95% one-sided confidence intervals for all three parameters were surprisingly small, suggesting that they may perform well as progression and efficacy determinants.

How to cite this article

Belin MW, Meyer JJ, Duncan JK, Gelman R, Borgstrom M, Ambrósio Jr R. Assessing Progression of Keratoconus and Cross-linking Efficacy: The Belin ABCD Progression Display. Int J Kerat Ect Cor Dis 2017;6(1):1-10.

Corneal Collagen Cross-Linking for Keratoconus: Systematic Review

Purpose

To evaluate the efficacy of collagen cross-linking (CXL) one year after treatment for keratoconus compared to no treatment by summarizing randomized controlled trials (RCTs) using a systematic review.

Methods

Trials meeting the selection criteria were quality appraised, and the data were extracted by two independent authors. The outcome parameters included maximum keratometry (K_max), corneal thickness at the thinnest point, best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), spherical equivalent (SE) refraction, and cylindrical refraction one year after CXL. We compared the changes in the above parameters with the control group.

Results

We identified five RCTs involving 289 eyes that met the eligibility criteria for this systematic review. The changes in BSCVA from baseline to one year exhibited a significant difference between the two groups. There was no statistically significant difference between the two groups for changes in corneal thickness and cylindrical refraction. We did not conduct a meta-analysis in K_max, UCVA, and SE refraction because their I² values were greater than 50%.

Conclusions

According to the systematic review, CXL may be effective in halting the progression of keratoconus for one year under certain conditions, although evidence is limited due to the significant heterogeneity and paucity of RCTs.

Patient selection for corneal collagen cross-linking: an updated review

Corneal cross-linking (CXL) is an option that in the last decade has demonstrated its efficacy and safety in halting the progression of keratoconus (KCN) and other corneal ectasias. Its indication has been extended beyond the classic definition that required evidence of KCN progression, especially in the presence of some risk factors for a possible progression (particularly the younger age). However, the results can be still somewhat variable today. There are several protocols, each with its own advantages and disadvantages. Some predictors of CXL outcome have been identified. We will review the current knowledge on patient selection for CXL, its indications, and options in special cases (such as thin corneas).

Novel Technique of Transepithelial Corneal Cross-Linking Using Iontophoresis in Progressive Keratoconus

In this work, the authors presented the techniques and the preliminary results at 6 months of a randomized controlled trial (NCT02117999) comparing a novel transepithelial corneal cross-linking protocol using iontophoresis with the Dresden protocol for the treatment of progressive keratoconus. At 6 months, there was a significant average improvement with an average flattening of the maximum simulated keratometry reading of 0.72 ± 1.20 D (P = 0.01); in addition, corrected distance visual acuity improved significantly (P = 0.08) and spherical equivalent refraction was significantly less myopic (P = 0.02) 6 months after transepithelial corneal cross-linking with iontophoresis. The novel protocol using iontophoresis showed comparable results with standard corneal cross-linking to halt progression of keratoconus during 6-month follow-up. Investigation of the long-term RCT outcomes are ongoing to verify the efficacy of this transepithelial corneal cross-linking protocol and to determine if it may be comparable with standard corneal cross-linking in the management of progressive keratoconus.

Assessing progression of keratoconus: novel tomographic determinants

Several methods have been described in the literature to both evaluate and document progression in keratoconus, but there is no consistent or clear definition of ectasia progression. The authors describe how modern corneal tomography, including both anterior and posterior elevation and pachymetric data can be used to screen for ectatic progression, and how software programs such as the Enhanced Reference Surface and the Belin-Ambrosio Enhanced Ectasia Display (BAD) can be employed to detect earlier changes. Additionally, in order to describe specific quantitative values that can be used as progression determinants, the normal noise measurement of the three parameters (corneal thickness at the thinnest point, anterior and posterior radius of curvature (ARC, PRC) taken from the 3.0 mm optical zone centered on the thinnest point), was assessed. These values were obtained by imaging five normal patients using three different technicians on three separate days. The 95 % and 80 % one-sided confidence intervals for all three parameters were surprisingly small (7.88/4.03 μm for corneal thickness, 0.024/0.012 mm for ARC, and 0.083/0.042 mm for PRC), suggesting that they may perform well as progression determinants.

Corneal collagen crosslinking for keratoconus or corneal ectasia without epithelial debridement

PURPOSE

Corneal collagen crosslinking (CXL) is a relatively new technique to reduce the progression of keratoconus. The technique can be performed with or without complete debridement of the corneal epithelium. We describe a novel intermediate technique involving mechanical disruption of the epithelium, and evaluate its safety and efficacy.

METHODS

The case notes of 128 eyes with progressive keratoconus or iatrogenic corneal ectasia who had undergone CXL using the epithelial disruption technique were retrospectively reviewed. Thin corneas were treated with hypotonic riboflavin. All others were treated with an isotonic solution. Note was made of preoperative and postoperative parameters, including uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, endothelial cell count, and corneal tomography. Occurrence of procedure-related complications was recorded. Statistical analyses were performed using the paired sample t-test and Wilcoxon signed-rank test, with a level of P<0.05 being accepted as statistically significant.

RESULTS

At 12 months, 41.8% of patients treated with isotonic riboflavin had improved UCVA and 29.7% had improved BSCVA. Only 13.4% lost lines of UCVA and 14.9% lost BSCVA. Of the patients treated with hypotonic riboflavin, at 12 months, 75% demonstrated stability of BSCVA and 25% had stable Kmax. In addition, 25% showed improved visual acuity at 12 months, and 58.3% showed regression of their Kmax. Our rate of short-term complications was comparable to studies using complete epithelial removal.

CONCLUSIONS

CXL with epithelial disruption is a safe and effective treatment for keratoconus or iatrogenic corneal ectasia, and may be better tolerated by patients than the epithelium-off technique.