Global Consensus on Keratoconus Diagnosis

Pediatric Keratoconus

Keratoconus is a common pediatric corneal disease, leading to vision impairment and amblyopia. Compared to its adult counterpart, pediatric keratoconus has an advanced presentation, rapid progression, higher incidence of complications such as corneal hydrops, and potential impact on the child's quality of life. It typically manifests during puberty and can evolve rapidly to more severe stages if left untreated. This rapid progression underscores the importance of early diagnosis through regular screening in pediatric populations and vigilant monitoring of pediatric keratoconus suspects. Concomitant ocular allergies, ocular anomalies, systemic diseases (eg. syndromes), and poor compliance with contact lenses might impede prompt intervention and frequently postpone rehabilitation. Corneal collagen crosslinking is a crucial intervention in the management of pediatric keratoconus because it strengthens the corneal microstructure and halts the disease's progression. When conservative measures fail, keratoplasty remains a viable option with generally favorable outcomes, though with unique challenges in post-operative care, including concerns related to sutures, long-term graft survival and need for repeated examinations under anesthesia. A multidisciplinary approach involving ophthalmologists, optometrists, pediatricians, and other healthcare professionals, focusing on early diagnosis and timely intervention, is essential for the comprehensive management of pediatric keratoconus and to mitigate its impact on children's lives.

Corneal Backscatter, Pachymetric Indices, and Ectasia Indices for the Assessment of Fuchs Endothelial Corneal Dystrophy

PURPOSE

To determine whether corneal backscatter, pachymetric indices, and ectasia indices derived from Scheimpflug tomography can identify Fuchs endothelial corneal dystrophy (FECD) corneas with abnormal tomography, the relationships between these parameters and tomographic edema in FECD, and if these parameters help predict improvement in central corneal thickness (CCT) after Descemet membrane endothelial keratoplasty (DMEK).

METHODS

Tomography maps of 132 eyes of 80 subjects with FECD were analyzed to determine how backscatter, pachymetric, and ectasia parameters compared with the instrument's normative database and if any predicted tomographic edema. Tomography maps from a separate group undergoing DMEK were split into derivation (48 eyes of 39 subjects) and validation (45 eyes of 41 subjects) subgroups to derive a predictive model of improvement in CCT after DMEK. Backscatter, pachymetric, and ectasia parameters were incorporated to determine if the model could be enhanced.

RESULTS

Among all ectasia, pachymetric, and backscatter parameters, at best only 65% of FECD corneas with definite tomographic edema could be identified based on the instrument's normative database. Among all parameters individually, the highest sensitivity for detecting tomographic edema was 77%. Anterior and mid-corneal backscatter featured in a model predicting improvement in CCT after DMEK with high performance in derivation (R2 = 0.79; 95% confidence interval, 0.65-0.87) and validation (R2 = 0.72; 95% confidence interval, 0.52-0.83) subgroups.

CONCLUSIONS

The Scheimpflug camera software program could not reliably detect abnormal tomography in FECD from corneal backscatter, pachymetric indices, or ectasia indices. Corneal backscatter contributes to, but does not enhance, a predictive model of improvement in CCT after DMEK.

Eye Rubbing in Chinese Patients With Keratoconus: A Multicenter Analysis

PURPOSE

To investigate the eye rubbing habits of Chinese patients with keratoconus.

METHODS

This study was carried out from 2018 to June 2022 at Shandong Eye Hospital, Qingdao Eye Hospital, and Henan Eye Hospital. The study compared the number of patients who rubbed their eyes between medical records and second time questionnaires, eye rubbing of patients with myopia and patients with keratoconus, and disease severity between patients with keratoconus. A questionnaire survey of ophthalmologists was conducted to determine their degree of awareness that eye rubbing is a risk factor for keratoconus.

RESULTS

The study assessed 799 patients with keratoconus and 798 control patients, and 97 ophthalmologists. The average proportion of patients with keratoconus who rubbed their eyes was 31.0% in the medical records with an increasing trend related to the increase in ophthalmologists' awareness, 66.6% after the second follow-up, and 25.4% among patients with myopia. After multivariate analysis, the following variables showed significant results: eye rubbing frequency more than 10 times/day (odds ratio [OR], 9.168; P < .001); rubbing with knuckles (OR, 9.804; P = .001); and prone sleep position (OR, 12.427; P < .001). The proportion of patients who rubbed their eyes with stage IV keratoconus was 71.9%, 18.9% higher than those with stage I, 4.8% higher than stage II, and 17.8% higher than stage III.

CONCLUSIONS

The proportion of Chinese patients with keratoconus who rubbed their eyes was relatively high. The main reasons for the low proportions reported were lack of attention. Clinical attention should be paid to eye rubbing in patients with keratoconus who should be educated to avoid it. [J Refract Surg. 2023;39(10):712-718.].

Evaluation of Retinal Layer Thicknesses in Patients with Keratoconus Using Retinal Layer Segmentation Analysis

OBJECTIVE

To conduct an evaluation of the effects of irregular astigmatism on the retinal nerve fiber layer (RNFL) and the retinal layers observed using spectral-domain optical coherence tomography (SD-OCT) in patients who had keratoconus (KC).

MATERIALS AND METHODS

A total of 255 eyes from 255 individuals, comprising 72 eyes of KC patients, 70 eyes of patients with astigmia, and 113 eyes of healthy controls were included in the analysis. RNFL scan maps (comprising global, temporal, superotemporal, inferotemporal, nasal, inferonasal, and superonasal maps) and macular thickness (MT) maps of a standard from the Early Treatment Diabetic Retinopathy Study (ETDRS) grid were assessed. The measurements were segmented automatically using Spectralis software, and included the RNFL, inner and outer plexiform layers (IPL, OPL), inner and outer nuclear layers (INL, ONL), ganglion cell layer, retinal pigment epithelium (RPE) in the central 6-mm ETDRS subfield.

RESULTS

The RNFL thickness in the KC group was lower when compared with the other two groups; however, statistically significant differences were noted in the global, temporal, superotemporal, and inferotemporal sectors (p < 0.05 for all). All of the central MT parameters showed significant variation among the groups, while a statistically significant decrease was noted in the KC group, except in the inferior outer sector (p = 0.741). In the segmentation analysis, the KC group had the significantly lowest IPL, ONL, RPE, and outer retinal layer (ORL) thickness among the groups (p < 0.05 for each). The astigmatic group was similar to the control group with regard to these parameters (p > 0.05 for each).

CONCLUSION

The eyes in the KC group appeared to have a thinner RNFL and MT when compared to those in the astigmatic and control groups. The ORLs, especially the ONL and RPE, were the most affected component of the macula in the KC group.

Keratoconus International Consortium (KIC)- advancing keratoconus research

CLINICAL RELEVANCE

The Keratoconus International Consortium (KIC) will allow better understanding of keratoconus.

BACKGROUND

Keratoconus is a disorder characterised by corneal elevation and thinning, leading to reduced vision. The current gaps in understanding of this disease will be discussed and the need for a multi-pronged and multi-centre engagement to enhance our understanding of keratoconus will be highlighted.

DESIGN

KIC has been established to address the gaps in our understanding of keratoconus with the aim of collecting baseline as well as longitudinal data on several fields.

PARTICIPANTS

Keratoconus and control (no corneal condition) subjects from different sites globally will be recruited in the study.

METHODS

KIC collects data using an online, secure database, which enables standardised data collection at member sites. Data fields collected include medical history, clinical features, quality of life and economic burden questionnaires and possible genetic sample collection from patients of different ethnicities across different geographical locations.

RESULTS

There are currently 40 Australian and international clinics or hospital departments who have joined the KIC. Baseline data has so far been collected on 1130 keratoconus patients and indicates a median age of 29.70 years with 61% being male. A total of 15.3% report a positive family history of keratoconus and 57.7% self-report a history of frequent eye rubbing.

CONCLUSION

The strength of this consortium is its international, collaborative design and use of a common data collection tool. Inclusion and analyses of cross-sectional and longitudinal data will help answer many questions that remain in keratoconus, including factors affecting progression and treatment outcomes.

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.

Oxidative Stress in the Anterior Ocular Diseases: Diagnostic and Treatment

The eye is a metabolically active structure, constantly exposed to solar radiations making its structure vulnerable to the high burden of reactive oxygen species (ROS), presenting many molecular interactions. The biomolecular cascade modification is caused especially in diseases of the ocular surface, cornea, conjunctiva, uvea, and lens. In fact, the injury in the anterior segment of the eye takes its origin from the perturbation of the pro-oxidant/antioxidant balance and leads to increased oxidative damage, especially when the first line of antioxidant defence weakens with age. Furthermore, oxidative stress is related to mitochondrial dysfunction, DNA damage, lipid peroxidation, protein modification, apoptosis, and inflammation, which are involved in anterior ocular disease progression such as dry eye, keratoconus, uveitis, and cataract. The different pathologies are interconnected through various mechanisms such as inflammation, oxidative stress making the diagnostics more relevant in early stages. The end point of the molecular pathway is the release of different antioxidant biomarkers offering the potential of predictive diagnostics of the pathology. In this review, we have analysed the oxidative stress and inflammatory processes in the front of the eye to provide a better understanding of the pathomechanism, the importance of biomarkers for the diagnosis of eye diseases, and the recent treatment of anterior ocular diseases.

Corneal cross-linking in patients with keratoconus: up to 13 years of follow-up

INTRODUCTION

To evaluate long-term safety and efficacy of corneal collagen cross-linking (CXL) in patients with keratoconus up to 13 years.

MATERIALS AND METHODS

In this mono-centre exploratory study, we included all consecutive patients who underwent CXL in our cornea centre from 01/01/2007 to 12/30/2011 and met the inclusion criteria. CXL was performed in all patients according to the Dresden protocol. Evaluation included best-corrected visual acuity (BCVA), topographic keratometry by Scheimpflug corneal tomography and endothelial cell count (ECC). Follow-up measurements were taken up to 13 years after treatment were compared with baseline values.

RESULTS

The study enrolled 168 eyes. The mean age of our patients was 26.3 years ± 7.8 years. A complete topographic dataset was available 1 year postoperatively for 142 eyes, 5 years postoperatively for 105 eyes, 10 years postoperatively for 61 eyes and 13 years postoperatively for 9 eyes. BCVA increased statistically significant after 1 year, 5 years and 10 years and non-significantly after 13 years. All keratometric parameters with exception of posterior astigmatism showed a statistically significant decrease after 1 year, 5 years and 10 years. After 13 years, the decrease was statistically significant only in Kmax, K2 and thinnest cornea. No significant changes in ECC were detected. Three eyes received Re-CXL, none of the eyes received penetrating keratoplasty and no infections occurred in this cohort.

CONCLUSIONS

CXL can slow down or even stop the progression of keratoconus in the majority of cases. The effect is long-lasting with excellent safety.

The Changing Face of the Cornea in a Case of Juvenile Glaucoma and Subclinical Keratoconus

We report on a 23-year-old man who presented with bilateral subclinical keratoconus and juvenile glaucoma (JG). With intraocular pressures (IOPs) of 30 and 28 mmHg, both eyes were consecutively operated by adjusted trabeculotomy, leading to a remarkable decrease in IOP to well below the mean for this surgery in JG. Meanwhile, most keratoconus indices clearly progressed in the first 5 months postoperatively, with increases in corneal hysteresis, associated with a remarkable drop in the corneal resistance factor. During the following years, IOP remained low, and all changes (except the increase in corneal hysteresis) reverted to near preoperative levels through the follow-up course of 5 years. This report complements a few existing reports that show the coincidence of keratoconus and JG, and, more importantly, documents a novel pattern of remarkable and prolonged corneal changes following surgical lowering of IOP in eyes with these changes. Postoperative biomechanical disturbances in the cornea and possibly limbus are proposed in cases of JG and subclinical keratoconus.

Single-cell atlas of keratoconus corneas revealed aberrant transcriptional signatures and implicated mechanical stretch as a trigger for keratoconus pathogenesis

Keratoconus is a common ectatic corneal disorder in adolescents and young adults that can lead to progressive visual impairment or even legal blindness. Despite the high prevalence, its etiology is not fully understood. In this study, we performed single-cell RNA sequencing (scRNA-Seq) analysis on 39,214 cells from central corneas of patients with keratoconus and healthy individuals, to define the involvement of each cell type during disease progression. We confirmed the central role of corneal stromal cells in this disease, where dysregulation of collagen and extracellular matrix (ECM) occurred. Differential gene expression and histological analyses revealed two potential novel markers for keratoconus stromal cells, namely CTSD and CTSK. Intriguingly, we detected elevated levels of YAP1 and TEAD1, the master regulators of biomechanical homeostasis, in keratoconus stromal cells. Cyclical mechanical experiments implicated the mechanical stretch in prompting protease production in corneal stromal cells during keratoconus progression. In the epithelial cells of keratoconus corneas, we observed reduced basal cells and abnormally differentiated superficial cells, unraveling the corneal epithelial lesions that were usually neglected in clinical diagnosis. In addition, several elevated cytokines in immune cells of keratoconus samples supported the involvement of inflammatory response in the progression of keratoconus. Finally, we revealed the dysregulated cell-cell communications in keratoconus, and found that only few ligand-receptor interactions were gained but a large fraction of interactional pairs was erased in keratoconus, especially for those related to protease inhibition and anti-inflammatory process. Taken together, this study facilitates the understanding of molecular mechanisms underlying keratoconus pathogenesis, providing insights into keratoconus diagnosis and potential interventions.

In vivo Assessment of Localised Corneal Biomechanical Deterioration With Keratoconus Progression

Purpose: To evaluate the regional corneal biomechanical deterioration with keratoconus (KC) progression as measured by the Stress-Strain Index (SSI) maps.

Methods: The preoperative examinations of 29 progressive KC cases that were submitted to corneal cross-linking (CXL) were evaluated. The examinations included the tomography and the SSI measured by the Pentacam HR and the Corvis ST (Oculus, Wetzlar, Germany), respectively. The results were recorded twice, the latter of which was at the last visit before the CXL procedure. The patient-specific SSI maps were built, using data at each examination, based on finite element modelling and employing inverse analysis to represent the regional variation of biomechanical stiffness across the cornea.

Results: All cases presented significant shape progression (above the 95% CI of repeatability) in anterior and posterior curvatures and minimum thickness. The overall corneal stiffness as measured by the SSI within the central 8 mm-diameter area underwent slight but significant reductions from the first to the last examination (−0.02 ± 0.02, range: −0.09 to 0, p < 0.001). In all 29 cases, the reduction in stiffness was localised and concentred in the area inside the keratoconus cone. The SSI values inside the cone were significantly lower in the last examination (by 0.15 ± 0.09, range: −0.42 to −0.01, p < 0.001), while the SSI outside the cone presented minimal, non-significant variations (0 ± 0.01, range: −0.04 to 0.01, p = 0.999).

Conclusion: It has been observed through the SSI maps that the regional deterioration in stiffness was concerted inside the area of pathology, while only mild non-significant alterations were observed outside the area of pathology.

In vivo biomechanical changes associated with Keratoconus progression

Purpose: To assess the biomechanical deterioration arising from keratoconus progression in-vivo.Materials and Methods: The preoperative examinations of 32 progressive KC cases that were submitted to corneal cross-linking were evaluated. The examinations included the corneal tomography using the Pentacam HR and biomechanical parameters assessed by the Corvis ST (Oculus, Wetzlar, Germany). The results were recorded at two time points, the latter of which was at the last visit before the CXL procedure. Keratoconus progression was characterised by a significant change in the ABCD system.Results: At the last follow-up visit (41.4 ± 40.9 months) all morphological parameters of the ABCD grading system showed significant deterioration (p < 0.001). The comparative analyses revealed a significant reduction in corneal stiffness expressed by a significant reduction in the stress-strain index (SSI: -0.10 ± 0.06, p < 0.001), the Stiffness parameter A1 (SP-A1: -6.1 ± 12.0 mmHg/mm, p = 0.011), by a significant increase in the integrated Inverse Radius (IIR: 0.95 ± 1.04 mm-1, p < 0.001) and in the deflection amplitude (DA) ratio (0.23 ± 0.58, p = 0.034). A barely significant increase in the DA also pointed towards corneal stiffness reduction. (0.04 ± 0.13 mm, p = 0.056). The SSI and the IIR were the indices with the smallest overlaps between the two examinations.Conclusions: It has been demonstrated in-vivo that corneal biomechanical deterioration occurs with keratoconus progression. The larger changes observed in the SSI and the IIR when compared to the remaining biomechanical parameters suggests that these parameters could be suitable to assess the corneal stiffness reduction in keratoconus natural progression.

Management Outcomes in Pediatric Keratoconus: Childhood Keratoconus Study

Introduction. The Global Delphi Panel of Keratoconus (KC) and Ectatic Diseases formulated management guidelines for KC in 2015. The aim of this study was to evaluate management outcomes in pediatric KC. Materials and Methods. Prospective, interventional study was conducted at a tertiary care hospital including KC patients aged <18 years. Based on disease severity and progression of disease, patients were prescribed either glasses or contact lenses (CLs) or underwent corneal collagen crosslinking (CXL), deep anterior lamellar keratoplasty (DALK), or penetrating keratoplasty (PK). Main Outcome Measures. Best corrected visual acuity (BCVA), manifest cylinder, maximum keratometry, thinnest corneal thickness, total higher order aberrations, and corneal hysteresis at baseline and 12 and 24 months. Results. 116 eyes of 62 patients with a mean age of 14.76 ± 2.77 years were included. 32.8% of the eyes (n = 38) achieved satisfactory BCVA with glasses/CLs only. Corneal collagen crosslinking (CXL) was performed in 43.1% of the eyes (n = 50) with progressive KC and halting of progression was noted in 83.3% (n = 35) of the eyes at 2 years. 7.7% of the eyes (n = 9) were managed for acute hydrops. DALK and PK were successfully performed in 9.5% (n = 11) and 6.9% (n = 8) of the eyes with BCVA of 0.14 ± 0.09 and 0.08 ± 0.12 at 2 years, respectively. Conclusions. Pediatric KC cases with progression show good visual and aberrometric outcomes and halting of progression after CXL. DALK and PK have good outcomes. The global consensus guidelines showed good clinical utility in pediatric patients. Presence of VKC did not have an impact on the outcomes of CXL in pediatric patients.

Keratoconus epidemiology: A review

Keratoconus is an ectatic corneal disease that affects both men and women, usually at a young age. Risk factors such as eye rubbing, environmental and genetic factors contribute to its pathogenesis. Keratoconus presents a variable prevalence, being as high as 5% of the population in the Middle East. In this review, an English-language search for keratoconus epidemiology was undertaken using the PubMed database. We present and discuss the findings of the most relevant epidemiological studies on keratoconus and describe its characteristics and risk factors, correlating them with its pathogenesis.

Tomographic changes after corneal collagen cross-linking for progressive keratoconus - one-year follow-up study

Introduction/Objective. The aim of this study was to evaluate the outcome of corneal collagen crosslinking (CXL) in patients with progressive keratoconus. Methods. This retrospective single-centered interventional study included 52 eyes of 41 patients who underwent epithelium-off CXL procedure at the age > 18 years. Corneal tomography data, uncorrected, and best spectacle-corrected distant visual acuity (UDVA and CDVA, respectively) were analyzed at baseline and postoperatively over the initial 12-month period. In addition, the natural course of corneal tomographic changes was demonstrated at one, three, six, nine, and 12 months after the CXL procedure. Results. At one year, mean UDVA improved significantly from 0.15 ? 0.22 (0.3 min ? logMAR ? 0 max logMAR) at baseline to 0.06 ? 0.09 logarithm of minimum angle resolution (logMAR) (0.1 min logMAR ? 0 max logMAR) (p = 0.024). Mean CDVA was 0.45 ? 0.39 0.45 ? 0.39 logMAR (0.8 min logMAR ? 0 max logMAR) at baseline and 0.06 ? 0.13 logMAR (1 min logMAR ? 0 max logMAR) at one year (p = 0.039). Maximum keratometry showed a significant flattening of 1.36 D ? 1.53 D (p = 0.0032) at one year after CXL. Minimum keratometry significantly decreased with a mean change of 1.15 ? 1.20 (p = 0.011). Mean anterior and posterior best fit sphere (ABFS and PBFS, respectively) remained stable during the entire follow-up period. Mean reduction of corneal thickness after CXL was 47 ? 61 ?m (p = 0.003). At one year, 29 (56%) eyes showed K max regression, 22 (53%) showed stabilization, and one (2%) showed progression. Spearman correlation coefficients were calculated to assess the correlation between difference in preoperative corneal thickness (CT), in posterior elevation corneal thickness (PECT), and minimum corneal thickness, ?CT (PECT ? minCT) and radius difference ?r (r1-r2). Spearman rs > 0.3 proved statistical significance and correlation. Conclusion. In our study, CXL effectively prevented progression of keratoconus in 98% of eyes at one year, while improving visual acuity. The effect of CXL can be evaluated at the earliest after six months; at that time, the stability of the corneal shape was provided by following the CXL procedure. The main limitation of this study is the small number of patients included.

The Aotearoa Research Into Keratoconus Study: Geographic Distribution, Demographics, and Clinical Characteristics of Keratoconus in New Zealand

PURPOSE

To investigate the epidemiologic, demographic, and basic clinical characteristics of individuals with keratoconus managed by optometrists in New Zealand (NZ)/Aotearoa.

METHODS

A prospective, longitudinal, nationwide, survey protocol was completed for every patient with keratoconus who underwent a consultation with participating optometrists in a 2-year period. Data for each patient included date of birth, sex, self-reported ethnicity, new or previous diagnosis, uncorrected (UCVA) and best-corrected visual acuity (BCVA), type of refractive correction required to obtain BCVA and keratometric readings obtained using keratometry or computerized topography.

RESULTS

One thousand eight hundred sixty-nine cases were identified, with a mean age of 41.0 ± 15.7 years, 56.4% being men, and 87.3% with previous diagnosis. The distribution of cases was skewed toward Auckland (41.6%), Waikato (21.3%), Wellington (16.8%), and Bay of Plenty (13.3%). Self-reported ethnicities were predominantly NZ European (54.4%), Māori (24.7%), and Pacific Peoples (15.5%), disproportionate to the general population profile (74.0%, 14.9%, and 7.4% respectively). Most eyes (64.3%) were managed with rigid contact lenses (corneal lens in 34.2%). The mean K-mean was 49.0 ± 5.7 D. The mean UCVA was 6/42 and BCVA was 6/9. Māori and Pacific Peoples had both the highest K-mean and proportions of eyes graded stage IV on the Amsler-Krumeich scale.

CONCLUSIONS

The results indicate that keratoconus is relatively common in NZ with at least 1869 patients managed by optometrists in 2 years. Most eyes had mild to moderate disease; however, Māori and Pacific Peoples seem to have greater disease severity. An ethnic predilection is apparent, with Māori and Pacific Peoples overrepresented relative to their population proportions, reinforcing a long-held clinical suspicion.

Bilateral Differential Topography-A Novel Topographic Algorithm for Keratoconus and Ectatic Disease Screening

Purpose: The purpose of this study was to establish a novel bilateral differential topographic algorithm and assess its efficacy for screening of keratoconus and corneal ectasia before corneal refractive surgery.

Methods: One hundred and sixty-one consecutive patients (115 men and 46 women, aged 22.8 ± 6.8 years) with keratoconus, including clinical keratoconus, subclinical keratoconus, forme fruste keratoconus (FFK), and corneal ectasia (KC group) and one hundred and seventy-four consecutive patients (97 men and 77 women, aged 25.1 ± 6.7 years) with ametropia (control group) visiting the Eye and ENT hospital of Fudan University from June 2018 to April 2021 were included. Bilateral differential keratometry, elevation, and pachymetry topographies were composed based on raw topographic data obtained by a Scheimpflug imaging anterior segment analyzer. Key bilateral differential characteristic parameters were calculated. SPSS 20 (SPSS Inc., IBM) was used for statistical analyses and the receiver operating characteristic (ROC) curves were used to determine the diagnostic efficacies.

Results: Mann-Whitney tests detected that the front keratometry, front elevation, corneal pachymetry, and back elevation maximal, mean, and standard deviation values within a 1.5-mm radius of the bilateral differential topography were all significantly higher in the KC group than in the control group (all p-values <0.001). The front keratometry mean (ΔFKmean) and standard deviation (ΔFKsd) and the front elevation standard deviation (ΔFEsd) and maximal (ΔFEmax) values within a 1.5-mm radius of the bilateral differential topography yielded the four highest accuracies (area under the ROC curve = 0.985, 0.985, 0.984, and 0.983, respectively) for discriminating KC cases (including FFK cases) from normal cases. Cut-off values of 0.75 diopters (D) for the ΔFKmean, 0.67 D for the ΔFKsd, 2.9 μm for the ΔFEsd, and 14.6 μm for the ΔFEmax had the highest sensitivities (95.7, 95.0, 96.9, and 95.0%, respectively) and specificities (96.0, 97.7, 94.8, and 95.4%, respectively).

Conclusion: Bilateral differential topographic parameters may be efficient for the early detection of keratoconus and corneal ectasia secondary to corneal refractive surgery. This bilateral differential topographic algorithm may complement conventional diagnostic models by improving the sensitivity and specificity of screening for early keratoconus and ectasia before corneal refractive surgeries.

Anterior pituitary, sex hormones, and keratoconus: Beyond traditional targets

"The Diseases of the Horny-coat of The Eye", known today as keratoconus, is a progressive, multifactorial, non-inflammatory ectatic corneal disorder that is characterized by steepening (bulging) and thinning of the cornea, irregular astigmatism, myopia, and scarring that can cause devastating vision loss. The significant socioeconomic impact of the disease is immeasurable, as patients with keratoconus can have difficulties securing certain jobs or even joining the military. Despite the introduction of corneal crosslinking and improvements in scleral contact lens designs, corneal transplants remain the main surgical intervention for treating keratoconus refractory to medical therapy and visual rehabilitation. To-date, the etiology and pathogenesis of keratoconus remains unclear. Research studies have increased exponentially over the years, highlighting the clinical significance and international interest in this disease. Hormonal imbalances have been linked to keratoconus, both clinically and experimentally, with both sexes affected. However, it is unclear how (molecular/cellular signaling) or when (age/disease stage(s)) those hormones affect the keratoconic cornea. Previous studies have categorized the human cornea as an extragonadal tissue, showing modulation of the gonadotropins, specifically luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Studies herein provide new data (both in vitro and in vivo) to further delineate the role of hormones/gonadotropins in the keratoconus pathobiology, and propose the existence of a new axis named the Hypothalamic-Pituitary-Adrenal-Corneal (HPAC) axis.

Ferrara Rings for Visual Rehabilitation in Eyes with Keratoconus and Previous Cross-Linking Using the Ferrara Ring Nomogram

PURPOSE

To report the visual, refractive and tomographic outcomes following the implantation of intrastromal corneal ring segments (ICRS) (Ferrara rings, AJL Ophthalmics, Miñano, Spain) in eyes with a history of keratoconus and corneal cross-linking using the Ferrara ring nomogram.

METHODS

Retrospective, interventional case series performed at the Corneoplastics Unit, Queen Victoria Hospital, East Grinstead, United Kingdom.

RESULTS

21 eyes of 19 patients with a history of keratoconus and prior corneal collagen cross-linking had Ferrara Intrastromal Corneal Ring Segments implanted between December 2015 and October 2017. The number, thickness and length of ring segments was chosen based on the Ferrara ring company nomogram. Mean uncorrected visual acuity (UDVA) improved from 0.88 to 0.52 logMAR (p < 0.001). Mean corrected visual acuity (CDVA) improved from 0.47 to 0.36 logMAR (p = 0.046). The percentage of eyes achieving 20/40 UDVA and CDVA increased from 5% to 38% and from 38% to 67%, respectively. Of the eyes, 52.3% gained at least two lines of CDVA. The spherical equivalent improved from -7.51D to -3.76D (p < 0.001) and the refractive astigmatism magnitude improved from 5.14D to 2.76D (p = 0.004). There were significant improvements in the corneal tomography with mean keratometry (K_M) improving from 50.40D (3.53) to 48.24D (3.00) (p = 0.01) and keratometric astigmatism magnitude improving from 5.14D (2.91) to 2.76D (1.67) (p = 0.004).

CONCLUSION

Insertion of Ferrara rings in keratoconic eyes with a history of prior cross-linking using the company nomogram results in significant improvements in visual, refractive and tomographic outcomes.

Contrast sensitivity and higher-order aberrations in Keratoconus subjects

This study analyzes the relationship between contrast-sensitivity and higher-order aberrations (HOA) in mild and subclinical-keratoconus in subjects with good visual-acuity (VA). Keratoconus group (including subclinical-keratoconus) and controls underwent autokeratometry, corneal-tomography, autorefraction and HOA measurement. Contrast-sensitivity was tested using a psychophysical two-alternative forced-choice Gabor patches in three blocks (6, 9, 12 cycles/deg). Controls were compared to the keratoconus group and to a keratoconus subgroup with VA of 0.00 LogMar group ("keratoconus-0.00VA"). Spearman correlation tested association between HOA and contrast-sensitivity. Twenty-two keratoconus subjects (38 eyes: 28 keratoconus, 10 subclinical-keratoconus, 20 keratoconus-0.00VA) and 35 controls were included. There was a significant difference between control and keratoconus, and between control and keratoconus-0.00VA, for keratometry, cylinder, thinnest and central corneal thickness (p < 0.001). Controls showed lower HOA and higher contrast-sensitivity for all spatial-frequencies (p < 0.001). Most HOA were negatively correlated with contrast-sensitivity for all spatial-frequencies for keratoconus group and for 9 and 12 cycles/deg for keratoconus-0.00VA. Keratoconus subjects with good VA showed reduction in contrast-sensitivity and increased HOAs compared to controls. HOA and contrast-sensitivity are inversely correlated in subjects with mild keratoconus despite good VA. This suggests that the main mechanism underlying the decreased vision quality in keratoconus is the increase of HOA.

Comparison of Different Methods of Corneal Collagen Crosslinking: A Systematic Review

Purpose: To review the scientific literature on the comparison of the efficacy of different corneal collagen crosslinking (CXL) protocols for the treatment of progressive keratoconus.Methods: Systematic review of randomized clinical trials (RCTs) on CXL outcomes. A search was carried out using the Cochrane Library, PubMed, EMBASE, Web of Science, Ovid MEDLINE, and Scopus databases. Internal validity was analyzed by applying the filter CASPe (Critical Appraisal Skills Program Spain).Results: The search yielded 1151 articles, and among these, 14 articles met the inclusion and exclusion criteria defined. Conventional (S) crosslinking (CXL) provided better topographic outcomes than transepithelial (TE) CXL, and S-CXL had a better therapeutic effect of corneal flattening than accelerated (A) CXL. The corneal thinning after CXL was lower with hypotonic riboflavin than with riboflavin-dextran. While one study demonstrated a better therapeutic effect of corneal flattening with S-CXL than with A-CXL, another study showed similar results between both techniques. No correlation was found between the depth of the demarcation line and topographic changes, which was not a direct measure of treatment effectiveness. Quality analysis of the literature reviewed yielded a mean score of 8.64, indicating that the RCTs evaluated had an overall acceptable quality.Conclusions: Good-quality RCTs comparing CXL techniques have been conducted, and most of them suggest that epi-off CXL can be considered the standard treatment for progressive keratoconus. TE-CXL and iontophoresis-assisted CXL are mainly indicated in patients with a risk of corneal scarring and patients with pain intolerance, respectively.

The possible causes for tomography suspect Keratoconus in a Chinese cohort

Background

To explore the possible causes of tomography suspect keratoconus (TSK) marked by Tomography in screening keratoconus in a Chinese cohort, and the reasonable range of corneal horizontal diameter and thickness for decreasing the proportion of TSK.

Methods

Nested case-control study from a single center prospective cohort. All subjects were selected from the Peking University Third Hospital Ectasia Cornea Disease Cohort Project database, which included myopic patients seeking corneal refractive surgical corrections since 2013. Demographic information, basic eye examination, and auxiliary equipment examination including refraction, IOL-master, Pentacam, Sirius, and Topolyzer were recorded. In this study, all cases were classified into two groups: TSK group and normal control (NC) group, and all of them were followed up at least 2 years. The former is consisted of those whose screening examinations of tomography are abnormal, the latter is those whose screening examinations are normal. All of them have already been followed up at least 2 years without abnormalities after excimer laser corneal refractive surgeries. Unpaired t tests and Chi-square tests were used to compare the differences of indices from the tomography between the two groups.

Results

Of 183 TSK eyes (109 patients) and 160 NC eyes (83 patients), the mean age is 28.0 and 26.3 years old respectively. The corneal horizontal diameter is 11.5–11.8 mm in TSK group and 11.8–12.0 mm in NC group. The central corneal thickness is nearly 520 μm in the former and 550 μm in the latter. For Sirius, the TSK ratio of indices of SIf and SIb is 41.5 and 39.9% respectively in TSK group. For Pentacam, the TSK ratio of index IHD is 59.0% and “final D” is 72.7%.

Conclusions

Corneal horizontal diameter and central corneal thickness have great influences on the results of corneal tomography in detecting the suspect keratoconus.

Accelerated Pulsed High-Fluence Corneal Cross-Linking for Progressive Keratoconus

PURPOSE

To report on 2-year results of accelerated corneal collagen cross-linking (CXL) in progressive ectasia using the Avedro KXL system.

DESIGN

Prospective interventional case series.

METHODS

A total of 870 patients (1,192 eyes) attending Moorfields Eye Hospital after CXL were included. All patients undergoing CXL had progressive keratoconus. Corneas with a minimum stromal thickness <375 μm were excluded. Riboflavin 0.1% soak duration was 10 minutes. High-fluence pulsed UVA was delivered at 30 mW/cm² for 4 minutes, with a 1.5-second on/off cycle (total energy 7.2 J/cm²). Subjective refractive, corneal tomography, and specular microscopy were performed at baseline, 6, 12, and 24 months postoperatively. The primary outcome measure was a change in maximum keratometry (Kmax) at 24 months.

RESULTS

Twelve- and 24-month follow-up data were available on 543 and 213 patients, respectively (mean age 25.4 ± 6.6 years). In mild cones (Kmax < 55 diopter [D]), mean keratometry remained unchanged at 24 months. In more advanced disease, we observed modest corneal flattening compared to baseline (Kmax 63.2 ± 6.5 D vs 61.9 ± 8.1 D, P = .02), but no significant changes in central keratometry (K1 or K2). Keratometric stabilization was confirmed in 98.3% of eyes. Mean CDVA, manifest refraction and endothelial cell density did not change. Overall, 2.7% of eyes lost more than 2 lines of CDVA.

CONCLUSION

Accelerated pulsed CXL is a safe, effective, and refractively neutral intervention (at 2 years) to halt disease progression in keratoconus.

Sensitivity and Specificity of Belin Ambrosio Enhanced Ectasia Display in Early Diagnosis of Keratoconus

Purpose

Early diagnosis of keratoconus disease (KCN) is the first priority in the preoperative evaluations of refractive surgery (RS).The aim of this study was to investigate the correlation between findings of Belin Ambrosio enhanced ectasia display (BAD) software and conventional corneal imaging (Orbscan and topography) in the early diagnosis of KCN.

Methods

For conducting this cross-sectional study, a total of 1000 eyes were selected from 500 patients that underwent the myopic photorefractive keratectomy surgery and were compared in four study groups during the years 2017-2018. In group 1, all topography, Orbscan, and BAD criteria were normal (65.8%).In contrast, in Group 2, at least one of the topography or Orbscan criteria as well as at least one BAD criterion (12.6%) were abnormal. In Group 3, the eyes had normal Orbscan and topography criteria with at least one abnormal BAD criterion (18.5%). Also, in Group 4, the patients had at least one abnormal Orbscan or topography criterion, but all BAD criteria (3.1%) were normal. Thickness of the thinnest point (TP) of cornea was compared in Pentacam and topography. Data analysis was done by SPSS software (version 21).

Results

BAD criteria were normal in 78.5% of all eyes with normal topography and Orbscan criteria (specificity). BAD criteria were also abnormal in 80.2% of eyes (sensitivity). There was also no significant difference between TP in Orbscan and Pentacam.

Conclusions

BAD criteria had a relatively acceptable sensitivity and specificity, compared with conventional Orbscan and topography criteria. Thus, BAD criteria can be more effective in the early diagnosis of KCN.

Topographic properties of the cornea in welders

PURPOSE

The aim of the present study was to evaluate the topographic status of the welders' corneas.

METHODS

In this historical cohort, a group of welders (with at least 5 years' experience in welding) and a control group were assessed and compared. Lack of exposure to welding for 3 months or more was considered an exclusion criterion. In all participants, after taking a complete history of visual and ocular problems, both eyes underwent Pentacam imaging. Then, all subjects received slit lamp biomicroscopy for evaluation of ocular surface diseases.

RESULTS

The data of 140 welders (mean age: 46.66 ± 13.01 years) and 172 controls (mean age: 45.05 ± 12.61 years) were analyzed. The welders' corneas had significantly higher eccentricity (p < 0.0001), keratometry readings (p < 0.0001), and cylinder power (p < 0.0001). The central, inferior, and nasal cornea were significantly thinner in the welders than in controls (p < 0.0001) while the difference was not significant in the superior and temporal cornea. All indices of corneal irregularity except for the central keratoconus index (CKI) and index of height asymmetry (IHA) were higher in welders compared to the control group (p < 0.0001).

CONCLUSION

According to the results of this study, the welders' corneas are topographically irregular. Welders exhibit characteristics like steeper keratometry readings; higher eccentricity indexes; thinner central, inferior, and nasal corneas; and higher indices of corneal irregularity, especially the CK index. Long-term ultraviolet exposure may be a possible reason for these corneal changes.

Outcomes of sequential intracorneal ring segment and phakic intraocular lens insertion for visual rehabilitation in keratoconus

PURPOSE

To report the visual and refractive outcomes of sequential intracorneal ring segment (ICRS) and toric phakic intraocular lens (IOL) insertion for visual rehabilitation in keratoconus.

METHODS

A retrospective interventional cohort study was performed through the Corneoplastics unit and Eye Bank, Queen Victoria Hospital, East Grinstead, United Kingdom.

RESULTS

14 eyes of 12 patients had sequential ICRS and phakic IOL implantation for visual rehabilitation of keratoconus between June 2014 and February 2018. After at least 6 months follow-up, the number of eyes with an uncorrected distance visual acuity (UDVA) of 20/40 UDVA or better increased from zero (0%) to 10 (71%). 12 (85.7%) eyes achieved a post-operative UDVA equal to or better than the pre-operative corrected distance visual acuity (CDVA). The number percentage of eyes with a CDVA of 20/40 or better increased from 3 (31%) to 14 (100%). The mean final spherical equivalent improved from -4.07 to -0.17 (p ⩽ 0.001). The mean refractive astigmatism magnitude improved from 4.76D to 1.23D (p = 0.002). Seven (50%) eyes had 1.0D or less of refractive astigmatism post-operatively.

CONCLUSION

In this cohort of eyes with keratoconus, sequential ICRS and phakic IOL implantation resulted in excellent visual and refractive outcomes after at least 6 months.

Evaluation of Visual Acuity Outcomes and Corneal Alterations of New Generation Hybrid Contact Lenses in Patients With Advanced Keratoconus

PURPOSE

To evaluate the visual and corneal outcomes of new generation hybrid contact lenses (HCL) in patients with advanced keratoconus.

METHODS

This was a retrospective study undertaken at a single academic center. The study cohort consisted of subjects with advanced keratoconus who had elected not to undergo keratoplasty and were fitted with HCLs. Patients were fitted either with EyeBrid (LCS, Cane, France) or Airflex (SwissLens, Prilly, Switzerland) HCLs. Primary outcome measures included contact lens (CL) drop-out rate, best corrected visual acuity, and corneal endothelial cell density (ECD) measurements at the end of a 6-month HCL wear. ECD was measured using in vivo confocal microscopy (ConfoScan4; Nidek, Tokyo, Japan). One eye per patient was included for statistical purposes. Paired t tests and Wilcoxon signed-rank tests were used for comparative analyses.

RESULTS

Thirty-two keratoconic eyes of 32 patients (14M/18F) with a mean age of 25.9 ± 11.5 years were included in the study. All patients were able to continue CL wear for a duration of 6 months. There was a significant improvement in the mean best corrected visual acuity from 0.5 ± 0.2 logarithm of minimal angle of resolution to 0.1 ± 0.1 logarithm of minimal angle of resolution after daily CL wear with HCL at the 6-month follow-up visit (P < 0.001). No vision-threatening CL-related corneal adverse effects were observed. There was no significant reduction in the ECD noted at the 6-month visit [2625.8 ± 300.3 cells/mm (baseline) vs. 2566.4 ± 309.8 cells/mm (6-month); P = 0.623].

CONCLUSIONS

Hybrid contact lenses can provide improved visual function without inducing any short-term clinical or microscopic adverse effects on corneal endothelial cells in patients with advanced keratoconus.

The prevalence of corneal abnormalities in first-degree relatives of patients with keratoconus: a prospective case-control study

PURPOSE

Although there is a high prevalence of keratoconus in the Middle East including Israel, limited data is available describing first-degree relatives of patients with sporadic keratoconus (KC) using Scheimpflug imaging. The purpose of this study is to accurately phenotype first-degree relatives of patients with sporadic KC in Israel using corneal tomography, which may help determine the genetic aetiology of KC.

METHODS

First-degree relatives (N = 56) of 16 KC probands participated in this prospective case-control study. Healthy controls (N = 96) were from a previous study. Autorefraction, visual acuity, slit lamp biomicroscopy, retinoscopy, subjective refraction and Scheimpflug imaging (CSO Sirius Topographer) of keratoconus patients and their first-degree relatives were evaluated. The worse eye was used for KC and KC suspects. The main outcome measure was prevalence of abnormal corneal topography and tomography parameters, which was compared between first-degree relatives vs controls. p values < 0.05 were considered significant.

RESULTS

KC (N = 2) or KC suspect (N = 8) was diagnosed in 18% (95% CI 8-28%) of the first-degree relatives. At least one abnormal corneal parameter was evident in 34% of first-degree relatives, while this was significantly lower for controls (14%, χ2(1,N = 152)  = 8.8, p = 0.01). Qualitative analysis showed KC first-degree relatives had significantly more abnormal anterior corneal topography patterns than controls (34% vs 17%, χ2(1,N = 152)  = 5.9, p = 0.02). For first-degree relatives, sex was not a factor influencing prevalence of corneal abnormalities (18% for both men and women, χ2(1,N = 56)  = 0.0, p = 1.0). A significant correlation was found for first-degree relatives between age and most corneal parameters, while this was not evident for the control group.

CONCLUSIONS AND RELEVANCE

Eye care practitioners should consider first-degree relatives of patients with KC at moderate risk for the disease and/or corneal abnormalities.

Posterior pole retinal thickness distribution pattern in keratoconus

PURPOSE

To evaluate the pattern of retinal thickness distribution in patients with keratoconus (KCN) and its correlation with disease severity.

METHODS

For this cross-sectional cohort study, the study subjects with documented keratoconus and normal eyes were prospectively enrolled. All subjects had anterior segment (Pentacam HR) and posterior segment (Spectralis) imaging. Posterior segment imaging by optical coherence tomography included the posterior pole asymmetry analysis map. Data were analyzed with multiple linear regression models and correlation tests to examine the mean and variance of the measured thickness of the retina and its distribution relative to the presence and severity of KCN.

RESULTS

A total of 24 subjects with keratoconus (48 eyes) and 14 normal subjects (28 eyes) enrolled in this study. The posterior pole retinal thickness, both superior and inferior hemifields, as well as the overall retinal thickness in KCN patients was greater than the control group. There was a direct correlation between the overall retinal thickness of the posterior pole and the severity of KCN (R² = 0.422, P < 0.001). However, the variability of the retinal thickness showed no difference between KCN-afflicted and healthy eyes.

CONCLUSION

Although KCN is a disease of the anterior segment of the eye, we found an orderly increase in posterior pole retinal thickness that is correlated with the severity of disease in KCN eyes compared to control. These findings suggest that the retina may maintain some degree of plasticity to respond to the degraded optical system of the eye.

Is there a potential link between keratoconus and autism spectrum disorders?: A case report and literature review

RATIONALE

Eye rubbing (ER) is a proven factor that can trigger the onset and progression of keratoconus (KC). Apart from allergy, ER is a repetitive motor stereotypy. Eye rubbing is frequently observed in children with autism spectrum disorders (ASDs) and in individuals who may be at risk for developing KC. We present a child with ASD who developed progressive KC following standard corneal cross-linking (CXL), most likely because of abnormal ER associated with allergy and repetitive behavior due to ASD symptoms.

PATIENT CONCERNS

A 14-year-old boy was referred to our clinic because of asymmetric visual acuity reduction.

DIAGNOSIS

The child was diagnosed as having keratoconus. He had a strong ER habit. The child had been previously diagnosed as having ASD.

INTERVENTIONS

Corneal cross-linking was performed in both the eyes. On account of keratoconus progression, most likely associated with persistent ER habit, he was retreated with CXL in the right eye. Behavioral modification intervention for ER habit reversal was also applied.

OUTCOMES

Corneal cross-linking in combination with behavioral modification intervention for ER habit reversal prevented further KC progression.

LESSONS

Behavioral interventions are likely to provide positive results in an ER habit reversal in children with ASD. Keratoconus treatment with CXL combined with behavioral management for ER reversal seemed effective in halting keratoconus progression in a young patient with ASD.

The Correlation between Corneal Findings and Disease Severity in Keratoconus per Scheimpflug Corneal Tomography

PURPOSE

This study aims to correlate the clinical signs of keratoconus (KC) which include superficial apical scarring, Fleischer rings, and Vogt striae with best spectacle-corrected visual acuity (BSCVA) and corneal tomography findings. Patients and methods. A retrospective observational study. 72 consecutive KC patients seen by the senior author over the course of one year were included in this case series. Eyes with pellucid marginal degeneration, postrefractive ectasia, history of a corneal graft, prior corneal collagen cross-linking, intracorneal ring segments or hydrops were excluded from analysis. Subsequently, the final analysis included only treatment-naïve KC eyes with varying degrees of disease severity.

RESULTS

BSCVA with manifest refraction was 0.5 logMAR higher in eyes with apical scarring (p < 0.001). Eyes with apical scarring had worse vision than eyes with Fleischer rings alone (0.43 logMAR higher in the former, p < 0.001). Eyes with apical scarring had worse vision than eyes with Fleischer rings alone (0.43 logMAR higher in the former, K2 = 64.56 ± 12.89 D versus 49.07 ± 6.61 D, p < 0.001). Eyes with apical scarring had worse vision than eyes with Fleischer rings alone (0.43 logMAR higher in the former, K2 = 64.56 ± 12.89 D versus 49.07 ± 6.61 D, p < 0.001). Eyes with apical scarring had worse vision than eyes with Fleischer rings alone (0.43 logMAR higher in the former, K2 = 64.56 ± 12.89 D versus 49.07 ± 6.61 D, p < 0.001). Eyes with apical scarring had worse vision than eyes with Fleischer rings alone (0.43 logMAR higher in the former, p < 0.001). Eyes with apical scarring had worse vision than eyes with Fleischer rings alone (0.43 logMAR higher in the former, p < 0.001). Eyes with apical scarring had worse vision than eyes with Fleischer rings alone (0.43 logMAR higher in the former, p < 0.001). Eyes with apical scarring had worse vision than eyes with Fleischer rings alone (0.43 logMAR higher in the former.

CONCLUSION

The presence of apical scarring and Fleischer rings on biomicroscopy can aid the clinician in making the distinction between severe or long-standing disease (respectively). Apical scarring is a sign of advanced disease and is associated with worse BSCVA and tomography findings. Fleischer rings are markers of intermediate disease and their presence correlates with disease duration.

Shift in progression rate of keratoconus before and after epithelium-off accelerated corneal collagen crosslinking

PURPOSE

To evaluate the shift in keratoconus progression rate after corneal collagen crosslinking (CXL).

SETTING

Chinese University of Hong Kong Eye Centre, Hong Kong, China.

DESIGN

Prospective case series.

METHOD

Accelerated epithelium-off CXL was performed in patients with progressive keratoconus. Optical coherence tomography-based corneal measurements were recorded. The data collected after the first postoperative month were used for analysis. The main outcome measure was the rate of progression of steep keratometry (K), flat K, average K, and best-fit sphere (BFS) using linear mixed-effects models. Progression was defined based on a significant slope against time in these models.

RESULTS

Forty-seven eyes (38 patients; mean age 27.6 years ± 6.5 [SD]) were included. The median number of preoperative visits and postoperative visits was 3 and 5, respectively. A significant reduction in the progression rate of the anterior average K (0.063 ± 0.138 diopter [D]/mo to -0.022 ± 0.029 D/mo) and posterior average K (-0.011 ± 0.025 D/mo to 0.000 ± 0.009 D/mo) occurred (both P < .001). On univariate analysis, the baseline anterior average K had the strongest association with the progression rate of the anterior average K after CXL. On multivariate analysis, the preoperative progression rate of the posterior BFS was significantly associated with postoperative progression rate of the anterior (P < .001) and posterior average K (P ≤ .05).

CONCLUSIONS

A significant reduction in the progression rate of average K occurred after accelerated epithelium-off CXL. The reduction was associated with the baseline anterior average K and preoperative progression of posterior BFS.

Intrasubject Repeatability and Interdevice Agreement of Anterior Chamber Depth Measurements by Orbscan and Pentacam in Different Grades of Keratoconus

OBJECTIVES

To evaluate the repeatability of anterior chamber depth (ACD) measurements by Orbscan and Pentacam imaging devices in different grades of keratoconus.

METHODS

One examiner performed 3 consecutive ACD measurements with both devices on 74 eyes of 42 keratoconus patient. Repeatability was assessed using intrasession test-retest variability. Within-subject SD was determined for repeatability, and the coefficient of variation was calculated for each measurement. The intraclass correlation coefficient (ICC) was also determined to assess the variance of repeated data.

RESULTS

Overall, the three ACD measurements were not significantly different either with Pentacam or Orbscan. The ICC index values were greater than 90% with both devices, and it significantly reduced at higher grades of keratoconus with Pentacam. Interdevice differences were statistically significant. The interdevice agreement with ACD measurements was 0.981, and the agreement was lower at higher grades of keratoconus. The 95% limits of agreement between the 2 devices for ACD was from -0.19 to 0.04.

CONCLUSIONS

Our results indicate acceptable repeatability for ACD measurements with both Orbscan and Pentacam in keratoconus patients. The progression of keratoconus has no significant effect on repeatability results of these devices. The good agreement between them allows their interchangeable use.

Enhanced Ectasia Detection Using Corneal Tomography and Biomechanics

PURPOSE

To test the accuracy of the Tomographic and Biomechanical Index (TBI) for ectasia detection in an independent population from the original study.

DESIGN

Retrospective case-control study.

METHODS

Subjects: Patients were grouped according to clinical diagnosis including corneal topography (front-surface curvature): Normal group, including 1 eye randomly selected from 312 patients with normal corneas; Keratoconus group, including 1 eye randomly selected from 118 patients with keratoconus; a nonoperated ectatic eye from 57 patients with very asymmetric ectasia (57 eyes, VAE-E group), and the nonoperated fellow eye with normal topography (57 eyes, VAE-NT group).

MAIN OUTCOME MEASURES

The ability of TBI to distinguish normal and ectatic corneas; and comparison with other indexes, including the Belin/Ambrósio Deviation Index (BAD-DI) and the Corvis Biomechanical Index (CBI), considering the areas under receiver operating characteristic curves (AUCs).

RESULTS

The AUC of the TBI was statistically higher than all other tested parameters (DeLong, P < .001). Considering all cases, the cut-off value of 0.335 for the TBI provided a sensitivity of 94.4% and a specificity of 94.9% (AUC = 0.988; 95% confidence interval [CI] 0.982-0.995). Considering the VAE-NT group, optimized TBI cut-off value of 0.295 provided a sensitivity of 89.5% and a specificity of 91.0% (AUC = 0.960; 95% CI 0.937-0.983).

CONCLUSION

The TBI was more accurate than all parameters tested for differentiating normal from ectatic corneas. The TBI may epitomize ectasia susceptibility and distinguish cases with fruste disease from true unilateral cases among the eyes with normal-topography VAE.

Evaluation of the effect of corneal collagen cross-linking for keratoconus on the ocular higher-order aberrations

BACKGROUND

Corneal collagen cross-linking (CXL) is the only treatment currently available to arrest the progression of keratoconus. The procedure consists of photopolymerization of stromal collagen fibers induced by combined action of a photosensitizing substance (riboflavin or vitamin B2) and ultraviolet-A light.

PURPOSE

To determine changes in the ocular higher-order aberrations (HOAs) after CXL and its correlation with changes in visual acuity.

DESIGN

Prospective interventional study.

SUBJECTS AND METHODS

This study was conducted on 30 eyes of 16 patients with progressive keratoconus documented between 2012 and 2014. Patients were treated with epithelium-off CXL and followed for a minimum of 6 months. The following ocular HOAs were measured and analyzed using I-Tracey Aberrometer: coma, trefoil, spherical aberration, astigmatism, and total HOAs.

RESULTS

There was statistically significant improvement in uncorrected visual acuity and best-corrected visual acuity between the preoperative and 6-month evaluations (P<0.001). Total HOAs and total coma were statistically significantly reduced at 6 months by 25% and 18%, respectively. Significant improvement was seen in spherical aberration by 8.71% (P<0.001), while no significant change was observed in trefoil and high order astigmatism (P=0.405 and 0.329, respectively). There was a statistically significant change in the average (K) value at the apex between the preoperative values and the 6-month values (P<0.05).

CONCLUSION

Total HOAs, total coma, and spherical aberrations decreased after CXL. Coma has a direct relationship with the improvement of visual function.