Prevalence of keratoconus in paediatric patients in Riyadh, Saudi Arabia

Update on Pediatric Corneal Diseases and Keratoplasty

Managing pediatric corneal disorders is challenging as the prognosis of pediatric keratoplasty depends on several factors. Advancements in the genetic basis of congenital corneal diseases and investigations in congenital corneal conditions provide a better understanding of pediatric corneal conditions. Surgeons performing keratoplasty in children now have a choice of various techniques. Evolving surgical techniques of anterior lamellar and endothelial keratoplasties has expanded the management interventions in these pediatric corneal morbidity conditions; however, considerable concerns still exist in association with corneal transplantation in infants and children. Outcomes in pediatric keratoplasty depend upon the preoperative indications, the timing of surgical intervention, intraoperative and postoperative factors including the patient/care givers' compliance. Factors such as low scleral rigidity, higher rate of graft failure, need for frequent examinations under anesthesia, and difficulty in optimal visual acuity assessment still remain a considerable challenge in pediatric scenarios. In children, deprivation amblyopia as a result of the corneal opacification can adversely affect visual development, causing dense amblyopia. Outcomes to surgical interventions for management of corneal opacification in children is further compromised by the pre-existing amblyopia apart from the concerns of refractive outcome of the graft. Graft rejection, graft infection, amblyopia, and glaucoma continue to be serious concerns. In recent years both anterior and posterior lamellar keratoplasty techniques are being increasingly performed in pediatric eyes, which offer advantages in the form of lower risk of graft rejection. The timing of surgery, careful case selection, cautious intraoperative approach, and optimal postoperative management can improve the anatomical and functional outcome in difficult cases.

Prevalence of keratoconus in Ghana: A hospital-based study of tertiary eye care facilities

PURPOSE

To estimate the prevalence of keratoconus in tertiary eye care facilities in Ghana.

METHODS AND ANALYSIS

In this hospital-based retrospective cohort study, medical records of patients from tertiary/referral eye care facilities in Ghana were reviewed. Included in the study were records of individuals who visited the eye care facilities and were diagnosed of keratoconus within the period of January 2016 to December 2019 inclusive. Data on patients' demographics, severity of keratoconus, mode of diagnosis, treatment, and visual acuity outcomes were analysed.

RESULTS

Out of the total of 142,209 records reviewed, 75 patients were diagnosed of keratoconus in at least one eye (127 eyes; 86.8% bilateral cases), representing a prevalence estimate of 53 per 100000 (95% confidence interval (CI): 41 to 65 per 100000). The mean ± SD age of patients at the time of diagnosis was 21.1 ± 9.5 years (66.2% males). The mean ± SD keratometry in keratoconus patients was 52.1 ± 7.0: majority (76.5%) of the cases were moderate to severe keratoconus. The main primary treatment regimen was corneal transplant (58.8%) followed by spectacles (25.0%), crosslinking (8.8%) and rigid contact lens (7.3%). There was a significant association between post-treatment visual acuity outcomes and treatment type (p < 0.001).

CONCLUSION

Our study represents the first prevalence estimate of keratoconus in Ghana. The prevalence of keratoconus estimated in our study is lower than that reported in countries with tropical climates. This could be due to lower uptake of referrals, underdiagnosis and/or misdiagnosis of the condition in lower-level health facilities.

Diagnosis of keratoconus in a young male by electrophysiological test findings: A case report

RATIONALE

The purpose of this report was to describe the diagnostic process of a case of keratoconus (KCN) after electrophysiological examination.

PATIENT CONCERNS

A 23-year-old male army officer presented with decreased visual acuity (VA) in the left eye for 5 months. Best-corrected VA was 20/20 in the right eye and 20/300 in the left eye. The cornea and lens were clear in both eyes with a normal anterior chamber. No specific abnormalities were found on fundus photography, optical coherence tomography, fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA), or full-field electroretinography (ffERG) of both eyes. Pattern visual-evoked potentials (PVEP) detected a reduced amplitude and delayed peak time of the P100-wave in both eyes, which was more severe in the left eye. The amplitude and peak time of the P2-wave in flash VEP (FVEP) were comparable in both eyes and were within the normal ranges.

DIAGNOSIS

Corneal topography was performed, and KCN was diagnosed by the presence of an asymmetrical bowtie pattern in both eyes, which was worse in the left eye.

INTERVENTIONS

Transepithelial corneal collagen cross-linking was performed.

OUTCOMES

The BCVA of both eyes remained stable after treatment at follow-up.

LESSONS

KCN should be suspected in cases of unimproved VA and significant irregular stigmatism, while no obvious lesions exist in other parts of the eyes. The evidence of lesion location by electrophysiological examinations could sometimes be of favor in diagnosing KCN.

Keratoconus detected by corneal topography in patients seeking refractive surgery in Jazan region, Saudi Arabia: A retrospective cross-sectional study

Background

Keratoconus is a non-inflammatory, chronic, idiopathic, corneal disease characterized by thinning of the core or paracentral part of the cornea. In this study, we demonstrate the prevalence of keratoconus among patients seeking refractive surgery using laser vision correction (LVC) at the Department of Ophthalmology, Private Eye Center, Jazan, Saudi Arabia.

Materials and methods

A retrospective cross-sectional study was undertaken with the data from January 1, 2019 to December 31, 2019 in the ophthalmology department of Jazan city. This study included 1068 eyes of 534 patients of which 56.8% were men. The mean patient age was 28.5 (SD = 8.3) years. The analyst performed chi-square tests for the report. Prevalence was calculated at a 95% confidence interval at specified times in the year (CI).

Results

The prevalence of manifest unilateral keratoconus was 3% and that of bilateral keratoconus was 18.72%; on the other hand prevalence rates of suspected unilateral KC was 16.48% and of bilateral KC 9.36%. Significant differences between eyes were noted and recorded.

Conclusion

The occurrence and spread of this condition are on the rise in the city of Jazan and on the outskirts.

Terminology

eyeball disorder (keratoconus), prevalence, risk factors, treatment of the disorder (vision).

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We reported a high prevalence of keratoconus. 3% had uni KC, 18.72% had bi KC, 16.48% had uni KC, and 9.36% had bi KC.

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Using social media websites, malls, and television to raise awareness of keratoconus is recommended.

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Screening is recommended for the detection of keratoconus early to avoid its complications.

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Future studies should include a larger number of hospitals to estimate the prevalence of keratoconus in the Jazan region.

Combining Spectral-Domain OCT and Air-Puff Tonometry Analysis to Diagnose Keratoconus

PURPOSE

To investigate the diagnostic capacity of spectral-domain optical coherence tomography (SD-OCT) combined with air-puff tonometry using artificial intelligence (AI) in differentiating between normal and keratoconic eyes.

METHODS

Patients who had either undergone uneventful laser vision correction with at least 3 years of stable follow-up or those who had forme fruste keratoconus (FFKC), early keratoconus (EKC), or advanced keratoconus (AKC) were included. SD-OCT and biomechanical information from air-puff tonometry was divided into training and validation sets. AI models based on random forest or neural networks were trained to distinguish eyes with FFKC from normal eyes. Model accuracy was independently tested in eyes with FFKC and normal eyes. Receiver operating characteristic (ROC) curves were generated to determine area under the curve (AUC), sensitivity, and specificity values.

RESULTS

A total of 223 normal eyes from 223 patients, 69 FFKC eyes from 69 patients, 72 EKC eyes from 72 patients, and 258 AKC eyes from 258 patients were included. The top AUC ROC values (normal eyes compared with AKC and EKC) were Pentacam Random Forest Index (AUC = 0.985 and 0.958), Tomographic and Biomechanical Index (AUC = 0.983 and 0.925), and Belin-Ambrósio Enhanced Ectasia Total Deviation Index (AUC = 0.981 and 0.922). When SD-OCT and air-puff tonometry data were combined, the random forest AI model provided the highest accuracy with 99% AUC for FFKC (75% sensitivity; 94.74% specificity).

CONCLUSIONS

Currently, AI parameters accurately diagnose AKC and EKC, but have a limited ability to diagnose FFKC. AI-assisted diagnostic technology that uses both SD-OCT and air-puff tonometry may overcome this limitation, leading to improved treatment of patients with keratoconus. [J Refract Surg. 2022;38(6):374-380.].

Comparing the natural progression and clinical features of keratoconus between pediatric and adult patients

To present the natural course of keratoconus (KC) and compare pediatric and adult patients. Design A retrospective cohort study. Setting Hospital-based. Patient Population In total, 152 patients (288 eyes) diagnosed with KC at Chang Gung Memorial Hospital, Taiwan, were included. Previously managed patients and those with missing optical data were excluded. Observation Procedures Patients were divided into pediatric (≤ 18 years) and adult (> 18 years) groups. Demographics, clinical data, and optical variables were collected, including corrected distance visual acuity (CDVA), refractive error, and keratometric readings (K). Main Outcome Measure Optical variables at the final follow-up before aggressive treatment. Results In total, 20 pediatric (37 eyes) and 132 adults (251 eyes) patients were eligible for this study. The mean follow-up time was 2.98 years. Male predominance was observed in both groups. Both groups had similar clinical characteristics and optical variables at the initial diagnosis. Pediatric patients progressed significantly more rapidly in refractive errors, including spheres and cylinders, spherical equivalence, steep K, and flat K during the follow-up. However, significant change between the two study groups was only seen in sphere refractive error spherical equivalence. Conclusion Pediatric patients had more rapidly progressive KC than adult patients, so early detection and frequent follow-up for prompt interventions are necessary for these patients.

Pediatric Crosslinking: Current Protocols and Approach

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

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.

Best Indicators for Detecting Keratoconus Progression in Children: A Report From the Shahroud Schoolchildren Eye Cohort Study

PURPOSE

The purpose of this study was to investigate 3-year changes in keratoconus (KC) indices to determine the indicators of KC progression compared with age-related changes in children aged 6 to 12 years.

METHODS

In this report of the Shahroud Schoolchildren Eye Cohort Study, KC was diagnosed based on vision, refraction, tomography, and slitlamp examination findings. KC progression was defined as changes in refractive astigmatism or zonal maximum keratometry (Zonal Kmax-3 mm). Then, 3-year changes (Δ) in vision, refraction, and tomographic indices were compared between progressive KC and normal eyes. The best set of ∆parameters for distinguishing KC progression from age-related changes were determined using the area under curve (AUC).

RESULTS

Eighteen KC eyes and 10,422 normal eyes were analyzed. All KC cases showed progression after 3 years. Δindices were statistically different between the 2 groups except corrected distance visual acuity, anterior radius of curvature, irregularity index, and KC percentage index. The best Δindices, in descending order of AUC value, were index of height decentration, Zonal Kmax-3 mm, refractive astigmatism, single point Kmax, and index of vertical asymmetry (all AUC > 0.9), followed by inferior-superior asymmetry, index of surface variance, minimum corneal thickness, index of height asymmetry, KC index, posterior radius of curvature, and Belin/Ambrósio total Deviation (AUC = 0.8-0.9).

CONCLUSIONS

According to our findings, changes in index of height decentration, Zonal Kmax-3 mm, refractive astigmatism, single point Kmax, and index of vertical asymmetry are the best indices for detecting KC progression in children younger than 12 years.

[Prospects for early detection of keratoconus based on systems built for computer-assisted diagnostics of structural changes in the cornea]

The article is devoted to the problem of diagnosing subclinical keratoconus (KK). The need to identify early signs of KK is primarily associated with the potential for the development of iatrogenic keratoectasia in cases of underdiagnosis of the disease when determining the conditions for laser keratorefractive surgery involving a decrease in the thickness of the cornea. Today generally accepted algorithms for early computer-assisted diagnosis of KK are mainly based on the analysis of various morphometric parameters of the cornea, reflecting changes in its shape and thickness induced by structural abnormalities. Direct detection of structural changes in the cornea characteristic of early KK requires the use of high-tech imaging methods that are not always applicable in everyday clinical practice. The promising approach proposed in this study is based on the fact that a digital image of a corneal «slice» obtained using serial analyzers such as the Scheimpflug camera widely used in clinical practice provides indirect information about the structure of the epithelial layer, the local thickening of which takes place in the initial stages KK. It is this criterion that underlies the proposed system of computer-assisted diagnosis of KK. The carried out studies have shown the high sensitivity of this algorithm, and its specificity can be increased by involving the known diagnostic indicators of KK.

Prevalence of Subclinical Keratoconus in Children with Astigmatism in Iraq

Background: Keratoconus is a progressive ectatic corneal pathology that involves both eyes, its usually asymmetrical, its early diagnosis and treatment are vital for the prevention of ocular morbidity that usually happen if it's not treated. Aim: To detect the prevalence of subclinical keratoconus and keratoconus suspect in children with the astigmatic error of ≥2 Diopters in Diwaniya city, Iraq. Methods: This is a cross-sectional, observational study, which investigates all the children aged six to eighteen years with an astigmatic error of ≥2 Diopters who attended the ophthalmology department for a routine eye examination during the period from January 2020 to June 2021. All children underwent full eye examination and corneal imaging study with a modern set which is a pentagram with Scheimpflug technology.   Results: we had 488 children participated in our study, the Mean age of participants was 12.01 ± 1.24 (range 6–18) years, 255 children were males (52.2%) and 233 were female children (47.7%) and they were divided into 2 age groups: first one between 6 and 12 years 225 children ( 46.1%)  the second one between 12 to 18 years include 263 children (53.8%). We found 21 children with subclinical keratoconus ( 4.3% ) and 24 children were keratoconus suspects ( 4.9% ).   Conclusion: the prevalence of keratoconus whether subclinical or suspect among the children with astigmatism who enrolled in our study was relatively high, the use of modern imaging technique tests is vital in the diagnosis.    

Keratoconus: An updated review

Keratoconus is a bilateral and asymmetric disease which results in progressive thinning and steeping of the cornea leading to irregular astigmatism and decreased visual acuity. Traditionally, the condition has been described as a noninflammatory disease; however, more recently it has been associated with ocular inflammation. Keratoconus normally develops in the second and third decades of life and progresses until the fourth decade. The condition affects all ethnicities and both sexes. The prevalence and incidence rates of keratoconus have been estimated to be between 0.2 and 4,790 per 100,000 persons and 1.5 and 25 cases per 100,000 persons/year, respectively, with highest rates typically occurring in 20- to 30-year-olds and Middle Eastern and Asian ethnicities. Progressive stromal thinning, rupture of the anterior limiting membrane, and subsequent ectasia of the central/paracentral cornea are the most commonly observed histopathological findings. A family history of keratoconus, eye rubbing, eczema, asthma, and allergy are risk factors for developing keratoconus. Detecting keratoconus in its earliest stages remains a challenge. Corneal topography is the primary diagnostic tool for keratoconus detection. In incipient cases, however, the use of a single parameter to diagnose keratoconus is insufficient, and in addition to corneal topography, corneal pachymetry and higher order aberration data are now commonly used. Keratoconus severity and progression may be classified based on morphological features and disease evolution, ocular signs, and index-based systems. Keratoconus treatment varies depending on disease severity and progression. Mild cases are typically treated with spectacles, moderate cases with contact lenses, while severe cases that cannot be managed with scleral contact lenses may require corneal surgery. Mild to moderate cases of progressive keratoconus may also be treated surgically, most commonly with corneal cross-linking. This article provides an updated review on the definition, epidemiology, histopathology, aetiology and pathogenesis, clinical features, detection, classification, and management and treatment strategies for keratoconus.

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.

Corneal Scheimpflug topography values to distinguish between normal eyes, ocular allergy, and keratoconus in children

To identify and compare keratometric, corneal thickness, and elevation parameters and indices among healthy children, ocular allergy, and keratoconus using the OCULUS Pentacam Scheimpflug topography system. This study included healthy children, children with ocular allergy (OA) without keratoconus, and children with keratoconus (KC). The study design consisted of a prospective evaluation and review of medical records from a Brazilian ophthalmology department. The exclusion criteria were inability to undergo the ocular exam, other ocular diseases, contact lens wear, and topographic corneal ectasia. The effect of each corneal parameter was evaluated using univariate and multivariate logistic regression models adjusted for sex and age, and ROC curves were used to assess the ability each variable to discriminate among groups. A total of 182 subjects were included: healthy children (n = 99), children with OA (n = 32), and children with KC (n = 51). Groups differed in terms of sex, with more males in the OA group (73.2%) and the KC group (67.7%) than in the control group (40.9%). All corneal parameters studied differed significantly between the control and KC groups, and between the OA and KC groups; they also differed significantly between the three groups in terms of astigmatism, q-value, CCT, TP, BAD-D, and ARTmax values. We present the first study to describe and compare corneal tomographic parameters in healthy children, OA, and KC. Keratometry indices, ACD, ARTmax, AETP, and PETP were found to be the most useful for differentiating between healthy and KC children.IBR registry number: CAAE 54921916.9.0000.5404.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

Correlation between long-term use of rigid gas permeable contact lenses and endothelial morphometric changes in keratoconus patients

PURPOSE

This study was conducted to evaluate the effects of long-term use of rigid gas-permeable (RGP) contact lenses on corneal endothelium in keratoconus (KC) patients using non-contact specular microscopy. In addition, the correlation between wearing duration of RGP lenses (years & hours /d) and endothelial morphometric changes in KC patients was performed. This may provide more useful data for clinical application of RGP contact lens.

STUDY DESIGN

This study was a prospective, observational, comparative, hospital based, nonrandomized, cross-sectional, and quantitative study.

SUBJECTS AND METHODS

The study included 40 eyes of non-wearer contact lens KC patients (group 1) and 38 KC eyes with a long history of Rose K2 RGP contact lens wearing (group 2). The corneal endothelial morphology such as endothelial cell density (ECD); coefficient of variation of cell area (CV); percentage of hexagonal cells (HEX); and central corneal thickness (CCT) were evaluated in all patients using SP3000P Specular Microscope.

RESULTS

The study included 40 eyes of non-wearer contact lens KC patients (20 mild KC eyes and 20 moderate KC eyes) and 38 KC eyes with a long history of RGP contact lens wearing (18 mild KC eyes and 20 moderate KC eyes). The mean duration of RGP lenses wearing was 5.67 ± 3.481 years & 12.11 ± 2.698 h/d in mild KC eyes and 7.15 ± 5.294 years &13.65 ± 2.889 h/d in moderate KC eyes. Wearing duration in hours in mild KC eyes showed a significant moderate negative correlation with ECD (r = -0.529, p = 0.024) and a moderate positive correlation with CV (r = 0.565, p = 0.015). In addition, wearing duration in years in moderate KC eyes showed a significant moderate negative correlation with ECD (r = -0.465, p = 0.039) and moderate positive correlation with CV (r = 0.627, p = 0.003). However, wearing duration in hours in moderate KC eyes showed a significant moderate negative correlation with HEX only (r = -0.490, p = 0.028). This study reported significant corneal thinning in contact lens wearer KC eyes in contrast to non-wearer KC eyes.

CONCLUSION

This study documented a significant correlation between a long-term use of Rose K2 RGP using the three-point touch and corneal endothelial morphometric changes in KC patients. In addition, the current study confirmed a significant corneal thinning in RGP contact lens wearer compared to non-contact lens wearer KC patients. Further studies are recommended to evaluate the association between different RGP lens materials with different oxygen permeability transmissibility; different lens design types; different fitting methods; the duration of contact lens wear and the endothelial morphometric changes in KC patients.

[Stage-appropriate treatment of keratoconus]

Keratoconus (KC) is a progressive cone-shaped corneal protrusion that causes paracentral thinning at the apex of the cone and typically occurs asymmetrically on both sides. After a careful anamnesis and classification of the degree of severity a targeted treatment appropriate to the stage of the disease is available. If the visual acuity is no longer sufficient, rigid gas-permeable contact lenses (CL) are fitted by a specialist. Riboflavin UVA cross-linking (CXL) is recommended in cases of progression and visual acuity that is still useful for the patient. Intracorneal ring segments (ICRS) are indicated for CL intolerance in cases of reduced visual acuity and a clear central cornea. If the stage is more advanced, deep anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PKP) is recommended. A PKP is contraindicated in acute KC but deep stromal sutures for readaptation of the Descemet tear with gas filling of the anterior chamber can considerably shorten the course. Almost no other eye disease is nowadays as easily accessible for an early instrument-based diagnosis and stage-appropriate treatment as KC.

Estimated Prevalence of Keratoconus in the United States From a Large Vision Insurance Database

PURPOSE

To estimate the prevalence of keratoconus in the United States using a large vision insurance database.

METHODS

We used data from the 2016 vision service plan (VSP) Global claims database to estimate the prevalence of keratoconus among enrollees by state. The VSP Global database includes cross-sectional de-identified claims data summarized by state of residence in predefined age and gender groups. Crude values of prevalence of keratoconus are provided in the VSP Global database. The open-source software package qGIS version 3.12 was used as the geographic information system for geospatial analysis.

RESULTS

The prevalence of keratoconus among VSP enrollees in the United States was estimated to be 0.15% with 95% confidence interval (CI) (0.15%, 0.15%). The prevalence of keratoconus was highest in Western states and among male population. The highest prevalence of keratoconus was in Colorado (0.51%; 95% CI 0.49%-0.52%), with particularly high prevalence for men in the age groups 18 to 39 years (0.90%; 95% CI 0.84%-0.95%) and 40 to 64 years (0.90%; 95% CI 0.85%-0.95%).

CONCLUSION

The average prevalence of keratoconus in the United States in 2016 may be higher than previously reported. Living in Western states and male sex were associated with high prevalence.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Era of "Dr. YouTube": Evaluation of YouTube Videos as a Valid Source for Patient Education on Keratoconus

OBJECTIVE

To evaluate the content, quality, and reliability of keratoconus-related YouTube videos as sources for patient education.

METHODS

YouTube was queried using the keywords "keratoconus," "contact lenses for keratoconus," "corneal cross-linking," and "corneal transplant surgery for keratoconus." Two ophthalmologists independently classified videos as useful, misleading, or patient testimonials and rated them using the DISCERN score (range, 16-75), Journal of the American Medical Association score (JAMAS; range, 0-4), Global Quality Score (GQS; range, 1-5), and Keratoconus-Specific Score (KSS; range, 0-32). Interrater agreement was analyzed using intraclass correlation coefficients. Multivariate linear regression models were fitted to identify factors associated with quality and popularity indices.

RESULTS

Of the 300 videos screened, 201 were included in the study, 58% were classified as useful, 13% as misleading, and 29% as patient views. Overall video quality was poor, with an average DISCERN score of 22, JAMAS of 1.2, GQS of 1.8, and KSS of 4.5. Misleading videos scored significantly lower than average but had higher popularity compared with useful videos. Video length inversely correlated with popularity index. Television shows were more likely to share misleading information than other uploaders, whereas all videos uploaded by university channels provided useful information but constituted only 12% of all videos.

CONCLUSIONS

Videos rated the best source of information were not the ones most popular. YouTube has great potential to change the attitude of individuals both for and against the right choice. Therefore, health professionals should act to use this potential in favor of effective and reliable health communication.

Mitomycin C Application After Corneal Cross-linking for Keratoconus Increases Stromal Haze

PURPOSE

To evaluate and compare corneal haze as determined by optical coherence tomography (OCT) after corneal cross-linking (CXL) for the treatment of mild to moderate keratoconus with or without mitomycin C (MMC) application.

METHODS

This was a retrospective analysis of 87 eyes of 72 patients with mild to moderate keratoconus. The first group (n = 44 eyes) underwent CXL between June 2013 and January 2015 and the second group (n = 43 eyes) underwent CXL with MMC (CXL+MMC) between February and December 2015, both following the Dresden protocol. Patients were evaluated preoperatively and at 1, 3, 6, and 12 months postoperatively. Main outcome measures were corneal reflectivity and haze reflectivity measured by a specially developed OCT image analysis software.

RESULTS

Anterior corneal reflectivity at 1 month and 1 year postoperatively was 14.79 ± 4.68 and 25.97 ± 15.01 (P < .001), and 13.88 ± 4.39 and 18.41 ± 9.25 (P = .025) for the CXL and CXL+MMC groups, respectively. The reflectivity of the anterior stromal haze region at 1 month and 1 year postoperatively was 23.15 ± 5.91 and 33.14 ± 16.58 (P = .005), and 20.58 ± 7.88 and 27.14 ± 12.80 (P = .049) for both groups, respectively. The changes in simulated keratometry from preoperatively to postoperatively were similar in both groups. The CXL+MMC group showed larger maximum keratometry flattening: 53.41 ± 6.88 diopters (D) preoperatively and 49.44 ± 5.66 D 1 year postoperatively versus 52.27 ± 5.78 and 50.91 ± 4.25 D for CXL alone (P = .008).

CONCLUSIONS

MMC application following CXL significantly increases corneal haze. Similar studies need to be performed on simultaneous CXL and photorefractive keratectomy to evaluate the role of MMC in haze formation in such procedures. [J Refract Surg. 2021;37(2):83-90.].

Contribution of Bowman layer to corneal biomechanics

PURPOSE

To compare the elastic modulus of thin corneal lamellas using 2D stress-strain extensometry in healthy ex vivo human corneal lamellas with or without the presence of Bowman layer.

SETTING

Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Switzerland; ELZA Institute, Dietikon, Switzerland; Department of Ophthalmology, Philipps University of Marburg, Germany.

DESIGN

Prospective experimental laboratory study.

METHODS

Healthy human corneas were stripped of Descemet membrane and the endothelium for Descemet membrane endothelial keratoplasty. After epithelium removal, corneas were divided into 2 groups. In Group 1, Bowman layer was ablated with an excimer laser (20 μm thick, 10 mm). In Group 2, Bowman layer was left intact. Then, a lamella was cut from the anterior cornea with an automated microkeratome. Elastic and viscoelastic material properties were analyzed by 2D stress-strain extensometry between 0.03 and 0.70 N.

RESULTS

Twenty-six human corneas were analyzed. The mean lamella thickness was 160 ± 37 μm in corneas with Bowman layer and 155 ± 22 μm in corneas without. No statistically significant differences between flaps with and without Bowman layer were observed in the tangential elastic modulus between 5% and 20% strain (11.5 ± 2.9 kPa vs 10.8 ± 3.7 kPa, P > .278).

CONCLUSIONS

The presence or absence of Bowman layer did not reveal a measurable difference in corneal stiffness. This may indicate that the removal of Bowman layer during photorefractive keratectomy does not represent a disadvantage to corneal biomechanics.

Corneal Cross-Linking for Paediatric Keratoconus: A Systematic Review and Meta-Analysis

All corneal cross-linking techniques attenuated disease progression in patients with pediatric keratoconus for at least one year based on a meta-analysis. A standard and accelerated technique led to marked improvement in visual acuity. We determined the efficacy and safety of corneal cross-linking (CXL) in pediatric keratoconus by conducting a systematic review and meta-analysis. The PubMed and Cochrane databases were searched for relevant studies on the effects of standard, transepithelial, and/or accelerated CXL protocols in patients aged 18 years or younger. Standardized mean differences with 95% confidence intervals were calculated to compare the data collected at baseline and 12 months. The primary outcomes were maximum keratometry (Kmax) and uncorrected visual acuity (UCVA), and the secondary outcomes were the thinnest corneal thickness (TCT), best-corrected visual acuity (BCVA), and manifest refraction spherical equivalent or cylindrical refraction. Our search yielded 7913 publications, of which 26 were included in our systematic review and 21 were included in the meta-analysis. Standard CXL significantly improved the Kmax, UCVA, and BCVA, and significantly decreased the TCT. Accelerated CXL significantly improved UCVA and BCVA. In the transepithelial and accelerated-transepithelial CXL methods, each measurable parameter did not change after treatments. All CXL techniques attenuated disease progression in patients with pediatric keratoconus for at least one year. Standard and accelerated CXL led to marked improvement in visual acuity.

Development of a classification system based on corneal biomechanical properties using artificial intelligence predicting keratoconus severity

Background

To investigate machine-learning (ML) algorithms to differentiate corneal biomechanical properties between different topographical stages of keratoconus (KC) by dynamic Scheimpflug tonometry (CST, Corvis ST, Oculus, Wetzlar, Germany). In the following, ML models were used to predict the severity in a training and validation dataset.

Methods

Three hundred and eighteen keratoconic and one hundred sixteen healthy eyes were included in this monocentric and cross-sectional pilot study. Dynamic corneal response (DCR) and corneal thickness related (pachymetric) parameters from CST were chosen by appropriated selection techniques to develop a ML algorithm. The stage of KC was determined by the topographical keratoconus classification system (TKC, Pentacam, Oculus). Patients who were classified as TKC 1, TKC 2 and TKC 3 were assigned to subgroup mild, moderate, and advanced KC. If patients were classified as TKC 1–2, TKC 2–3 or TKC 3–4, they were assigned to subgroups according to the normative range of further corneal indices (index of surface variance, keratoconus index and minimum radius). Patients classified as TKC 4 were not included in this study due to the limited amount of cases. Linear discriminant analysis (LDA) and random forest (RF) algorithms were used to develop the classification models. Data were divided into training (70% of cases) and validation (30% of cases) datasets.

Results

LDA model predicted healthy, mild, moderate, and advanced KC eyes with a sensitivity (S_n)/specificity (S_p) of 82%/97%, 73%/81%, 62%/83% and 68%/95% from a validation dataset, respectively. For the RF model, a S_n/S_p of 91%/94%, 80%/90%, 63%/87%, 72%/95% could be reached for predicting healthy, mild, moderate, and advanced KC eyes, respectively. The overall accuracy of LDA and RF was 71% and 78%, respectively. The accuracy for KC detection including all subgroups of KC severity was 93% in both models.

Conclusion

The RF model showed good accuracy in predicting healthy eyes and various stages of KC. The accuracy was superior with respect to the LDA model. The clinical importance of the models is that the standalone dynamic Scheimpflug tonometry is able to predict the severity of KC without having the keratometric data.

Trial registration

NCT04251143 at Clinicaltrials.gov, registered at 12 March 2018 (Retrospectively registered).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40662-021-00244-4.

Keratoconus Epidemiology Presentations at Najran Province, Saudi Arabia

AIM

Our study aims to produce an estimation of the keratoconus disease epidemiology and important demographic factors in disease presentation in Najran city in the south of Saudi Arabia.

METHODS

Keratoconus patients between 9 and 29 years of age at the eye clinic of King Khaled General Hospital in Najran Province with a confirmed diagnosis of keratoconus were recruited over one year period. Visual acuity, keratometry, corneal thickness and demographic data were collected and analysed.

RESULTS

The keratoconus prevalence in Najran Province was found to be 87.3 cases per 100,000 people with an incidence of 28.47 per 100,000 cases. The disease presented more frequently in male patients (67.9%) with a statistically significant difference in the mean age between genders (p=0.014). Most cases presented at a moderate stage, and almost half of the cases reported a family history of the disease. There were statistically significant differences in best visual acuity and corneal thickness between genders (p<0.05). The majority of the cases were managed with contact lenses (56.08%).

CONCLUSION

Genetic and environmental factors could have a substantial role in the increased rate of keratoconus presentation in Najran Province. Screening programmes should dedicate more attention to late presentation to improve prevention and early detection. More studies on keratoconus epidemiology in Saudi Arabia are needed.

Mismatch of corneal specialists' expectations and keratoconus knowledge in general ophthalmologists - a prospective observational study in Switzerland

BACKGROUND

To assess whether Swiss general ophthalmologists have the minimal keratoconus knowledge that corneal specialists would expect them to have.

METHODS

Corneal specialists defined "minimal keratoconus knowledge" (MKK) with respect to definition, risk factors, symptoms and possible treatment options of keratoconus. A telephone interview survey was conducted among one hundred ophthalmologists (mean age 51.9 years (SD 9.5), 60 % male) from the German-speaking part of Switzerland. For each participant, years of work experience, number of keratoconus patients seen per year and access to a topography device were obtained. We calculated the proportion of MKK and examined in multivariate analyses whether ophthalmologists with access to topography and with greater work experience performed better than other groups.

RESULTS

No single ophthalmologist had MKK. The mean MKK was 52.0 %, and the range was 28.6-81.0 %. Per 10 years of working in private practice, the MKK decreased by 8.1 % points (95 % CI: -14.2, -2.00; p = 0.01). Only 24 % of participants correctly recalled the definition of keratoconus, 9 % all risk factors, 5 % all symptoms and 20 % all treatment modalities. The MKK values were not associated with the number of keratoconus patients seen per year and the availability of topography to diagnose keratoconus.

CONCLUSIONS

There is a substantial mismatch between corneal specialist' expectations and general ophthalmologists' knowledge about keratoconus. The low recall of symptoms and risk factors may explain why ophthalmologists diagnose relatively few cases of keratoconus, resulting in inefficient care delivery and delayed intervention.

High-Fluence Accelerated Epithelium-Off Corneal Cross-Linking Protocol Provides Dresden Protocol-Like Corneal Strengthening

Purpose

To assess whether optimized technical settings for accelerated epithelium-off corneal cross-linking may lead to increases in biomechanical stiffness similar to the benchmark 30-minute epithelium-off Dresden protocol.

Methods

Three-hundred porcine eyes were divided equally into six groups for analysis. All samples underwent epithelial debridement and soaking with 0.1% iso-osmolar riboflavin solution for 20 minutes. Corneal cross-linking (CXL) was performed using epithelium-off protocols varying in acceleration and total fluence (intensity in mW/cm² * time in minutes, total fluence in J/cm²): standard (S)-CXL (3*30, 5.4), accelerated (A)-CXL (9*10, 5.4), A-CXL (9*13'20″, 7.2), A-CXL (18*6'40″, 7.2), and A-CXL (18*9'15″, 10). Control corneas were not irradiated. The elastic modulus of 5-mm wide corneal strips was measured as an indicator of corneal stiffness.

Results

All irradiated groups had significantly higher elastic modulus than controls (P < 0.05), with a stiffening effect of 133% S-CXL (3*30, 5.4), 122% A-CXL (9*10, 5.4), 120% A-CXL (9*13'20″, 7.2), 114% A-CXL (18*6'40″, 7.2) and 149% A-CXL (18*9'15″, 10). The high-fluence accelerated epithelium-off protocol (18*9'15″, 10) showed the highest stiffening effect. Elastic modulus at 5% strain (1%-5% strain) showed significant differences between A-CXL (18*9'15″, 7.2) and three other accelerated protocols: A-CXL (9*10, 5.4; P = 0.01), A-CXL (9*13'20″, 7.2; P = 0.003), and A-CXL (18*6'40″, 10; P = 0.0001).

Conclusions

An accelerated high-fluence epithelium-off CXL protocol (18 mW/cm² for 9'15″) was identified to provide a significantly greater stiffening effect than any other accelerated protocols and is indistinguishable from the Dresden protocol, with accelerating irradiation times ranging from 30 to 9 minutes; by combining gentle acceleration with higher fluence, such a protocol does not require supplemental oxygen.

Translational Relevance

This A-CXL (18*9'15″, 10) protocol has the potential to become a new standard in epithelium-off CXL, delivering Dresden protocol-like strengthening over a shorter period.

Prevalence of keratoconus in persons with Down syndrome: a review

Purpose

Keratoconus is a vision-threatening condition, and there is a need for knowledge about the occurrence in subgroups of the population. The progression of the disease can be effectively stopped, and vision may be restored, if keratoconus is diagnosed at an early stage. The purpose of this review was to evaluate the literature of the prevalence of keratoconus in persons with Down syndrome.

Methods

We conducted a literature review of keratoconus prevalence in persons with Down syndrome. A thorough search was performed in Pubmed (Medline), and the quality of evidence was evaluated.

Results

The literature review identified 20 relevant studies, which reported keratoconus in 0%–71% of persons with Down syndrome. These studies varied greatly in design, patient selection, sample sizes and mean age, and the quality of evidence concerning estimates for the prevalence of keratoconus was generally evaluated as low. Most studies that included adults reported high prevalences of keratoconus–in many studies more than 10-fold the prevalence in the general population. No large screening studies in persons with Down syndrome were identified.

Conclusions

The present review showed that the prevalence of keratoconus in persons with Down syndrome is higher than in the general population. However, estimates from previous studies vary widely. Screening for keratoconus in this group should be considered.

Keratoconus in Africa: A systematic review and meta-analysis

PURPOSE

The aim of this review is to evaluate the prevalence of and factors associated with keratoconus in Africa.

METHOD

A systematic online literature search was conducted for articles on keratoconus in Africa. Meta-analysis was performed to estimate the prevalence of keratoconus in Africa. The Freeman-Tukey double arcsine transformation was used to minimize the effects of studies with extremely high or low prevalence estimates on the overall pooled estimates. Leave-one-out sensitivity analysis was used to assess the robustness of the pooled effects and potential outliers. Meta-regression was performed to explore associations between keratoconus, gender and age.

RESULTS

Twelve studies were included in the review; 5 from Egypt, 2 from South Africa, 2 from Kenya, 1 from Sudan, 1 from Ghana and 1 from Nigeria. Two studies were conducted in allergic conjunctivitis patients, 4 in keratoconus patients, 1 in contact lens service seekers, 1 in pre-LASIK patients, 1 in refractive patients and 1 in a student population. Eight studies were included in the meta-analysis. The overall prevalence estimate of keratoconus in Africa was 7.9% (95% CI: 2.5%-16.0%). The prevalence of keratoconus among males and females in Africa was estimated to be 9.3% (95% CI: 2.5%-19.5%) and 5.8% (95% CI: 1.5%-12.7%) respectively. The estimated prevalence of unilateral and bilateral keratoconus was 2.6% (95% CI: 0.4%-6.5%) and 5.8% (95% CI: 1.6%-12.3%), respectively. The estimated prevalence of mild keratoconus was 2.2% (95% CI: 0.7%-4.7%), moderate keratoconus was 3.5% (95% CI: 0.0%-11.8%) and severe keratoconus was 4.0% (95% CI: 0.0%-19.6%). There was no significant association between gender and the prevalence of keratoconus in Africa (p = 0.63), and age and the prevalence of keratoconus in Africa (p = 0.78).

CONCLUSION

The estimated prevalence of keratoconus reported here is higher than prevalence values reported in other meta-analyses or different geographical locations. This is mainly because studies included in this meta-analysis were either conducted on a cohort at high risk of keratoconus or a population with high possibility of finding keratoconus patients. There is a dearth of well-designed population-based studies on keratoconus in Africa, resulting in a lack of epidemiological information. This highlights the urgent need for research on keratoconus in Africa.

Individualized Corneal Cross-linking With Riboflavin and UV-A in Ultrathin Corneas: The Sub400 Protocol

PURPOSE

To determine whether corneal cross-linking (CXL) with individualized fluence ("sub400 protocol") is able to stop keratoconus (KC) progression in ultrathin corneas with 12-month follow-up.

DESIGN

Retrospective, interventional case series.

METHODS

Thirty-nine eyes with progressive KC and corneal stromal thicknesses from 214 to 398 μm at the time of ultraviolet irradiation were enrolled. After epithelium removal, ultraviolet irradiation was performed at 3 mW/cm² with irradiation times individually adapted to stromal thickness. Pre- and postoperative examinations included corrected distance visual acuity (CDVA), refraction, Scheimpflug, and anterior segment optical coherence tomography imaging up to 12 months after CXL. Outcome measures were arrest of KC progression at 12 months postoperatively and stromal demarcation line (DL) depth.

RESULTS

Thirty-five eyes (90%) showed tomographical stability at 12 months after surgery. No eyes showed signs of endothelial decompensation. A significant correlation was found between DL depth and irradiation time (r = +0.448, P = .004) but not between DL depth and change in K_max (r = -0.215, P = .189). On average, there was a significant change (P < .05) in thinnest stromal thickness (-14.5 ± 21.7 μm), K_max (-2.06 ± 3.66 D) and densitometry (+2.00 ± 2.07 GSU). No significant changes were found in CDVA (P = .611), sphere (P = .077), or cylinder (P = .915).

CONCLUSIONS

The "sub400" individualized fluence CXL protocol standardizes the treatment in ultrathin corneas and halted KC progression with a success rate of 90% at 12 months. The sub400 protocol allows for the treatment of corneas as thin as 214 μm of corneal stroma, markedly extending the treatment range. The DL depth did not predict treatment outcome. Hence, the depth is unlikely related to the extent of CXL-induced corneal stiffening but rather to the extent of CXL-induced microstructural changes and wound healing.

Outcomes and complications of implantable collamer lens for mild to advance keratoconus

PURPOSE

To evaluate the outcome and safety of implantable collamer lens (ICL; (Visian, STAAR Surgical, Monrovia, CA, USA) in mild to advance keratoconus patients with myopia and myopic astigmatism.

METHODS

This retrospective study evaluated all patients who underwent ICL implantation for the management of keratoconus at a tertiary care eye hospital from January 2012 to January 2018. The mean duration of follow-up was 15.3 months (range, 3.13 to 38.97 months). Data were collected on preoperative and postoperative uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA), refraction was compared, and adverse effects were evaluated.

RESULTS

Thirty-two eyes (32 patients) were evaluated. The median CDVA was 20/30 preoperatively and 20/20 at last follow-up. The median UDVA was 20/25 at last follow-up. Thirteen patients (40.6%) had 20/20 UDVA in comparison to none at baseline. The median spherical equivalent in diopters (D) was -7.875 D (-4.125 to -10.0 D) preoperatively and decreased to -0.3125 D at last follow-up. The median manifest refractive cylinder was 3.00 D (2.25 to 5.25 D) preoperatively and decreased to 1.125 D postoperatively. Cylinder axis rotation of 10° or greater occurred in 3 eyes (9.375%) and required repositioning of the ICL. One patient (3%) developed nonvisually significant anterior subcapsular cataract. One ICL (3.125%) had to be explanted due to residual refractive error and unsatisfactory vision.

CONCLUSION

ICLs are a suitable refractive option for the correction of refractive error associated with stable, nonprogressive keratoconus even in advance cases. However, the risk of ICL rotation and subsequent repositioning remain. Careful patient selection is necessary for achieving good outcomes and mitigating intraoperative and postoperative complications.

Indications of Keratoplasty and Outcomes of Deep Anterior Lamellar Keratoplasty Compared to Penetrating Keratoplasty

Background

Corneal diseases are a significant cause of visual impairment and blindness. Despite the treatable nature of many corneal diseases before visual demise, many cases of advanced disease necessitating keratoplasty for visual rehabilitation are encountered. A mismatch between the number of corneal donors and potential recipients also exists worldwide, with underutilization of certain types of keratoplasty techniques that may allow more efficient use of this limited resource.

Methodology

A retrospective cohort study of all cases of optical corneal transplantations performed from January 1, 2015 to October 31, 2020 was performed. Indications for keratoplasty, type of keratoplasty, complications, intraocular pressure elevation, and best corrected visual acuity (BCVA) by category and range at different time intervals were collected and analyzed. Findings were compared between penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) for all indications, specifically for keratoconus (KCN).

Results

A total of 58 corneal transplants meeting our criteria were performed during the study period. PK was performed for 29 eyes, DALK for 28 eyes, and endothelial keratoplasty for one eye. The most frequently encountered indication was KCN (62.1%). The number of eyes with BCVA of 20/100 or better increased from preoperative BCVA, 37/58 eyes had BCVA worse than 20/100 before keratoplasty (63.8%), while at the time of last follow-up 45/58 eyes had BCVA of 20/100 or better (77.6%). At the time of last follow-up 16/58 had BCVA in the range of 20/20 to 20/40 (27.6%) and 29/58 eyes had BCVA in the range of 20/50 to 20/100 (50%). Comparison of all cases of PK to DALK for all indications showed significantly better BCVA by category at one year, at last follow-up, and BCVA range at last follow-up (p = 0.032, 0.001, and 0.014, respectively). Although better visual acuity results by category and range at one year and last follow-up, respectively, were observed in more patients undergoing DALK than PK, for KCN the results were not statistically significant (p = 1.00, 1.00, 0.417, and 0.374, respectively). Overall, 70% of recorded complications, intraocular pressure (IOP) elevations, and graft rejections were seen in eyes that underwent PK; however, these findings were not statistically significant (p = 0.297). Graft failures occurred more frequently with PK than deep anterior keratoplasty when analyzed for all indications of keratoplasty (p = 0.010).

Conclusions

Despite advancement and improvements in surgical techniques, statistics continue to show underutilization of the invaluable resource of donor corneas, with PK still being performed more than DALK for diseases that do not affect the endothelium. Our study found superior visual acuity outcomes of DALK as well as the advantages of less frequent complications, IOP elevations, graft rejections, and graft failures. We encourage ophthalmologists to utilize DALK in appropriate candidates to more fully utilize the scarce and potentially vision-restoring resource of donor corneal tissue.

Pediatric keratoconus - Current perspectives and clinical challenges

Keratoconus is an ectatic corneal disease characterized by progressive stromal thinning, irregular astigmatism, and defective vision. It can be unilateral or bilateral with asymmetric presentation. It starts at puberty and either progresses rapidly to an advanced stage of the disease or stops in case of delayed onset and slow progression. Pediatric keratoconus is more aggressive than in adults and the management protocols differ because of various rationales such as accelerated progression, advanced stage of disease at the time of diagnosis and co-morbidities. It poses a burden to the society as it affects the quality of life, social, and educational development in children. Hence early diagnosis, recognition of progression, and timely intervention with collagen crosslinking is imperative to arrest the worsening. Association with systemic syndromes and ocular comorbidities can be of concern in pediatric keratoconus. Severe ocular allergy when associated hastens progress and complicates timely intervention of crosslinking treatment and compliance to contact lens wear. Keratoplasty in pediatric keratoconus has good outcomes but can encounter frequent suture-related concerns. This article discusses the epidemiology, etiopathogenesis, clinical challenges, and current perspectives of management of pediatric keratoconus.

Correlation between Keratoconus and Pollution

Introduction: Keratoconus is a corneal ectasia with multifactorial origin. Three risk factors for keratoconus are currently recognized: ultraviolet rays (UV), eye rubbing and atopy. In the current literature, other factors are evoked such as pollution, whose role in the physiopathology of keratoconus is unclear. The effects of particles matter (PM) 2.5 and 10 are the most studied and questioned in the scientific literature.Material and method: A correlation study was carried out to determine the influence of pollution on keratoconus. Fine particulate matter levels were measured according to available WHO data and were correlated with the prevalences of epidemiological studies. These measures were included in the study according to strict selection criteria.Results: The mean pollution rate of the selected studies was 29.1 ± 24.3 μg/m³ for PM_2.5 and 57.2 ± 56.2 μg/m³ for PM₁₀. The Pearson test shows a moderate correlation between the prevalence of keratoconus and the levels of PM_2.5 (R = 0.51; p = .022) and a strong correlation with the levels of PM₁₀ (R = 0.71; p < .001).Discussion: Fine particulate matter appears to be an emerging risk factor for keratoconus. They are thought to act indirectly by exacerbating known risk factors such as atopy and eye rubbing. And could have a direct action on the cornea by increasing the apoptosis of epithelial cells and interacting directly with the structure of collagen of the stroma.

A Comparative Study of Corneal Topography in Children with Autism Spectrum Disorder: A Cross-Sectional Study

Purpose: To investigate the corneal characteristics in individuals with autism spectrum disorder (ASD) and age-matched typical development (TD) participants. Methods: This cross-sectional, clinically based study compared children with ASD to age-matched TD participants. Corneal topography was measured with a portable EyeSys Vista system. The distance visual acuity (VA) and the contrast sensitivity (CS) were determined. The refractive error (RE) was assessed using a 2WIN autorefractometer. Results: A total of 31 children with ASD (mean age: 12.78 ± 4.49 years), and 60 participants with TD (mean age: 13.65 ± 3.56 years) were recruited. The two groups were similar in age (t = −2.084, p = 0.075) and VA (t = −0.35, p = 0.32). Most of the children with ASD had a significant amount of refractive errors (REs; range: +5.25 to −5.50 DS), and astigmatism was dominant (range: −0.25 to −4.50 DC). There was no statistically significant difference between both groups in terms of average corneal power (t = 1.12, p = 0.39). The children with ASD and participants with TD also did not differ significantly in terms of corneal shape descriptors (p > 0.05), such as corneal asphericity, inferior superior index, opposite sector index, and differential sector index. The spherical equivalent did not differ significantly between the ASD participants and participants with TD (t = 1.15, p = 0.15). There was a significant difference (p < 0.05) in the astigmatism component between the ASD participants and the participants with TD.

Outcomes of Corneal Topography among Progressive Keratoconus Patients 12 months following Corneal Collagen Cross-Linking

Purpose

This study aimed to assess the overall and specific topographic changes among patients who underwent corneal collagen cross-linking (CXL) due to progressive keratoconus.

Methods

This retrospective case series study was conducted at a single-arm hospital in King Abdulaziz Medical City, Riyadh. All progressive keratoconus patients who underwent CXL between January 2017 and December 2018 were included consecutively. The epi-off crosslinking technique (Dresden protocol) was applied in all patients. The topographic values were measured preoperatively and 12 months postoperatively. Patients with a history of a previous corneal procedure, corneal trauma, or any corneal scarring were excluded.

Results

Among our population (29 eyes of 24 patients), 58.6% of eyes were for male patients, and the mean age of the population was 27.76 ± 4.21 years. Based on the topography results, the mean values of corneal thickness at central 3 mm decreased from 473.45 ± 38 µm to 465.72 ± 41.78 µm following CXL (Z = −1.93, 95% confidence interval [CI] = 0.048–0.057, p= 0.053). Clinically significant astigmatism measurements were present in 28 (96.6%) eyes before CXL compared to 26 (89.7%) eyes after CXL. The mean values of astigmatism among the patients were 3.37 ± 2.25 diopters before and 3.67 ± 2.61 diopters after CXL (Z = −1696, 95% confidence interval [CI] = 0.085–0.096, p = 0.09). After CXL, the mean values of the front elevation at the apex changed from 33.90 ± 20.13 µm to 36.10 ± 21.09 µm (Z = −2.792, 95% [CI] = 0.003–0.006, p = 0.005). The mean values of the back elevation at the apex changed from 68.4 ± 35.66 µm to 69.90 ± 35.89 µm (Z = −0.934, 95% CI = 0.343–0.366, p = 0.35).

Conclusion

The topographic corneal parameters improved significantly in the patients with corneal ectasia after CXL. These results revealed the safety and efficacy of CXL in stabilizing keratoconus progression among Saudi patients at 1 year of follow-up.

Update on the genetics of keratoconus

In the past few years we have seen a great acceleration of discoveries in the field of keratoconus including new treatments, diagnostic tools, genomic and molecular determinants of disease risk. Recent genome-wide association studies (GWAS) of keratoconus cases and population wide studies of variation in central corneal thickness and in corneal biomechanical properties confirmed already identified genes and found many new susceptibility variants and biological pathways. Recent findings in genetic determinants of familial keratoconus revealed functionally important variants and established first mouse model of keratoconus. Latest transcriptomic and expression studies started assessing novel non-coding RNA targets in addition to identifying tissue specific effects of coding genes. First genomic insights into better prediction of treatment outcomes are bringing the advent of genomic medicine into keratoconus clinical practice.

Corneal Cross-Linking for Keratoconus: Current Knowledge and Practice and Future Trends

Corneal collagen cross-linking (CXL) with riboflavin is an accepted universal standard of care for our keratoconus patients with progressive disease. It has been a game changer in how we manage keratoconus. Early diagnosis and treatment is essential in paediatric patients as younger patients progress more rapidly and have poorer transplant outcomes. There is an ongoing debate around standard, accelerated, and transepithelial protocols of CXL, the role of CXL, and the combination of laser refractive surgery. Future developments will improve CXL safety and efficacy and the scope of utilization, but we must be careful not to leap too far ahead with clinical applications before publication of basic science research and good clinical results with standardized protocols.

The Enigma of Environmental Factors in Keratoconus

Keratoconus is an ectatic disorder with highly complex and varied causes including genetic variations and environmental factors. Its prevalence varies widely between regions and countries. Many environmental factors have been proposed to be associated with keratoconus, but the interpretation of their individual contributions is difficult due to the presence of many confounding variables. The current literature was reviewed to evaluate the strength of the associations and the causative effects of environmental factors on keratoconus. Ethnicity and consanguinity have been revealed as important determinants for geographical variations in keratoconus prevalence. Eye rubbing, atopy, floppy eyelid syndrome, contact lens wear, pregnancy, and thyroid hormone disturbances are likely associated with keratoconus. The first 4 factors can induce ocular surface inflammation, matrix metalloproteinase release, and keratocyte apoptosis, consistent with the postulated etiology of keratoconus. The associations of keratoconus with UV exposure, cigarette smoking, personality, and sex were less convincing once confounding factors were considered. Future studies powered for multivariate analysis of factors discussed will hopefully shed light on what is truly important in the development and progression of keratoconus.

Determining Progression in Ectatic Corneal Disease

Before the advent of modern tomographic imaging and corneal cross-linking (CXL), diagnosis and treatment of ectatic disease were limited to disease severity where changes on the anterior corneal surface lead to visual complaints. Rigid contact lenses and/or penetrating keratoplasty addressed late stage disease, as identifying early or subclinical disease was not possible, or its need appreciated. The emergence of CXL as a viable treatment to alter the natural progression of keratoconus heightened the need for improved diagnostics.Several methods have been described in the literature to evaluate and document progression in keratoconus, but there has been no consistent definition of ectasia progression. Newer imaging techniques (ie, tomography) allowed the detection of earlier ectatic disease, before visual loss and subjective complaints. The Belin ABCD classification/staging system was introduced on a Scheimpflug imaging system [Pentacam, (Oculus GmbH, Wetzlar, Germany)] to address previous shortcomings. The ABCD system utilizes 4 parameters: Anterior ("A") and posterior ("B" for Back) radius of curvature taken from a 3.0 mm optical zone centered on the thinnest point, "C" is minimal Corneal thickness, and "D" best spectacle Distance visual acuity. The first 3 parameters (A, B, C) are machine-generated objective measurements that can be used to determine progressive change.The staging system is not limited to a specific commercial entity and can be incorporated in any tomographic imaging system. The ABCD Progression Display graphically displays each parameter and shows when statistical change above measurement noise is reached. This should allow the clinician the ability to diagnose progressive disease at a much earlier stage than was previously possible, with the confidence that earlier intervention could prevent visual loss.

The Prevalence and Risk Factors for Keratoconus: A Systematic Review and Meta-Analysis

PURPOSE

This study was conducted to determine the prevalence and risk factors for keratoconus worldwide.

METHODS

In this meta-analysis, using a structured search strategy from 2 sources, 4 electronic databases (PubMed, Web of Science, Google Scholar, and Scopus) and the reference lists of the selected articles were searched from inception to June 2018 with no restrictions and filters. The outcome of the study was the prevalence of keratoconus and its risk factors, including eye rubbing, family history of keratoconus, atopy, allergy, asthma, eczema, diabetes type I and type II, and sex.

RESULTS

In this study, 3996 articles were retrieved, of which 29 were analyzed. These 29 articles included 7,158,241 participants from 15 countries. The prevalence of keratoconus in the whole population was 1.38 per 1000 population [95% confidence interval (CI): 1.14-1.62 per 1000]. The prevalence of keratoconus was 20.6 per 1000 (95% CI: 11.68-28.44 per 1000) in men and 18.33 per 1000 (95% CI: 8.66-28.00 per 1000) in women in studies reporting sex. The odds ratio of eye rubbing, family history of keratoconus, allergy, asthma, and eczema was 3.09 (95% CI: 2.17-4.00), 6.42 (95% CI: 2.59-10.24), 1.42 (95% CI: 1.06-1.79), 1.94 (95% CI: 1.30-2.58), and 2.95 (95% CI: 1.30-4.59), respectively.

CONCLUSIONS

The results of this study, as the most comprehensive meta-analysis of keratoconus prevalence and risk factors, showed that keratoconus had a low prevalence in the world and eye rubbing, family history of keratoconus, allergy, asthma, and eczema were the most important risk factors for keratoconus according to the available evidence.

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.

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

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

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

A Case of Early Keratoconus Associated with Eye Rubbing in a Young Child

INTRODUCTION

Keratoconus usually presents during puberty and is considered rare in young children.

METHODS

Case report with clinical findings and computerized corneal tomography.

RESULTS

We report the case of an 8-year-old girl with early bilateral keratoconus who presented with allergic conjunctivitis and persistent eye rubbing. Although our patient did not exhibit steep keratometry, early cones and inferotemporal thinnest corneal thicknesses were detected in both eyes using Scheimpflug imaging (Oculus GmbH Pentacam, Wetzlar, Germany). Belin/Ambrósio total D values were 1.85 on the right and 2.11 on the left. Improvement in best-corrected visual acuity was noted after treatment of allergic eye disease, and corneal tomographic findings remained stable 4 months after initial consult.

CONCLUSION

This is a case of early diagnosed keratoconus in a young patient. Diagnosis of this condition in young children is challenging, as these patients are less likely to report visual complaints, and clinical examination is usually unremarkable. Keratoconus screening should be considered in children with atopy and eye rubbing behavior regardless of age, even in those with no other associated pathology and with negative family history.

Screening for Keratoconus in a High-Risk Adolescent Population

PURPOSE

To estimate the prevalence of keratoconus (KC) in a majority-Emirati adolescent population and to demonstrate the feasibility of screening using a dual Scheimpflug and Placido imaging device.

METHODS

Adolescent subjects from two secondary schools in Abu Dhabi, UAE underwent corneal imaging with the Galilei tomographer (Ziemer Ophthalmic Systems AG, Port, Switzerland). The prevalence of KC and KC suspects was determined using a combination of both subjective and objective criteria. Objective criteria included these KC indices: percent probability of keratoconus, inferior-superior index, asphericity asymmetry index, maximum keratometry and thinnest pachymetry. Subjective pattern analysis was performed by four experienced cornea specialists. Subjects were classified by each cornea specialist into three groups: normal, KC and KC suspect. The final classification was made by group reconciliation of cases where disagreement was present. Inter-observer agreement was assessed with the kappa statistic.

RESULTS

A total of 839 eyes of 420 students between 10 and 19 years of age underwent corneal tomography. After the exclusion of 251 eyes due to insufficient scan quality based on internal instrument-derived standards, 588 eyes of 339 subjects were included in the analysis. The prevalence of KC and KC suspect was estimated to be 2.7% (95% CI [1.2%, 5.0%]) and 19.8% (95% CI [15.7%, 24.4%]), respectively. There was a strong inter-observer agreement between examiners' classification of the subjects' KC status (kappa = 0.84).

CONCLUSION

KC is highly prevalent in Emirati adolescents. Screening secondary school students for keratoconus appears to be feasible and may be indicated in this population to improve early detection and intervention.

Assessment of the mechanical forces applied during eye rubbing

Background

To determine the average amount of mechanical forces applied to the lids of keratoconus patients during eye rubbing.

Methods

Fifty-seven patients (41 male, 16 female, average age 34.8 years) with a clinically and topographically diagnosed keratoconus and a history of eye rubbing were prospectively asked to perform their individual eye rubbing movement on a high-precision balance. The type of eye-rubbing movement and the force applied, represented in newtons (N), were recorded and analyzed.

Results

We detected three different types of eye rubbing. Rubbing with the fingertip was most frequent (51%), followed by rubbing with the knuckle (44%) and rubbing with the fingernail (6%). Each type of eye rubbing showed different average forces, with knuckle type eye rubbing applying significantly more force (9.6 ± 6.3 N) on the lids than fingertip (4.3 ± 3.1 N) and fingernail (2.6 ± 3.3 N) types (p < 0,001 and p = 0,016, respectively).

Conclusions

There were major variations in the force exerted on the lids, depending on the type of eye rubbing employed. This data will help determine the forces that need to be applied in future experimental eye rubbing models.