Air Pollution and the Prevalence of Keratoconus: Is There a Connection?

PURPOSE

Keratoconus is a progressive, asymmetrical corneal ectasia with multifactorial origin. Three identified risk factors for keratoconus include exposure to ultraviolet (UV) rays, eye rubbing, and atopy. Other factors like pollution would play a role in the physiopathology of keratoconus. In this study we investigate the effects of particles matter (PM) of 2.5 and 10 μm, but also nitrogen dioxide (NO2) and the correlation with the prevalence in the scientific literature.

METHOD

A literature review was performed using four databases (PubMed, Research gate, Google scholar and International Journal of Keratoconus and Ectatic Corneal Diseases) according to strict selection criteria. Levels of fine particles and nitrogen dioxide were extracted from available World Health Organization (WHO) databases and correlated with prevalences from epidemiological studies.

RESULTS

The mean pollution rate in the selected studies was 26.88 ± 25.26 μg/m3 for PM2.5 , 58.23 ± 60.98 μg/m3 for PM10 and 24.79 ± 12.58 μg/m3 for NO2. Pearson correlation tests revealed a significant positive correlation between prevalence of keratoconus with particles rate of PM2.5 (R = 0.58; p < 0.001), PM10 (R = 0.67; p < 0.001) and NO2 (R = 0.64; p = 0.00016).

CONCLUSION

Fine particles appear to be a risk factor for keratoconus. These pollutants may act indirectly by exacerbating known risk factors such as atopy and eye rubbing. Atmospheric pollution may also have a direct effect on the cornea, by disturbing the structure of the epithelium and increasing cell apoptosis.

Modeling biological growth of human keratoconus: On the effect of tissue degradation, location and size

Keratoconus is a non-inflammatory bilateral disease, that usually occurs in the inferior-temporal region, where the cornea bulges out and becomes thinner, due to the gradual loss of structural organization in corneal tissue. Degenerated extracellular matrix and fibers breakage have been observed in keratoconic corneas, that may promote the progression of the pathology. While keratoconus histopathology has been widely described in literature, its etiology is still not clear. Being able to fully understand keratoconus growing process could be crucial to detect its development and improve prevention strategies. This work proposes a novel continuum-based keratoconus growth model. The proposed framework accounts for the structural changes occurring in the underlying tissue during the progression of the disease, as indicated in experiments. The developed formulation is able to replicate the typical bulging and thinning of keratoconic corneas, as well as different forms in terms of shape, as they are commonly classified in clinics (nipple, oval and globus cones). The cone that is obtained constitutes a permanent deformed state, not pressure dependent. The resulting model may help to better understand the etiology of the behavior of this disease with the aim of improving the diagnosis and the treatment of the pathology.

Assessment of large-diameter and small-diameter SoftK specialty contact lenses for early-stage keratoconus

INTRODUCTION

Soft contact lenses may be a good alternative for early-stage keratoconus (KC) patients who do not tolerate rigid gas permeable (RGP) lenses due to ocular discomfort or complications. This prospective study compared outcomes obtained after 2 weeks of wearing two types of soft silicone hydrogel contact lenses for keratoconus that varied in their diameter and central thickness (cc).

METHODS

Patients with Amsler-Krumeich grades I or II KC were fitted with small-diameter (14.2 or 14.8 mm) SoftK (SD-SoftK, cc = 0.48 mm) and large-diameter (17 mm) SoftK (LD-SoftK, cc = 0.60 mm) lenses, each worn for 2 weeks in a crossover design. Low (10%;10VA) and high (100%;100VA) contrast visual acuity, contrast sensitivity (CS, Pelli-Robson), higher order aberrations (HOAs, Visionix Vx130), the number of trial lens modifications during fitting and the subjectively preferred lens were compared using Friedman tests with post-hoc analysis.

RESULTS

Forty eyes (N = 20, 10 males, mean age: 39.0 ± 9.9 years, range: 23-55 years) were examined. Their habitual median (interquartile1, interquartile3) 10VA (LogMAR), 100VA (LogMAR) and CS (LogCS) were 0.52 (0.30, 0.50), 0.14 (0.10, 0.15) and 1.35 (1.35, 1.50), respectively. For the SD-SoftK condition, the values were 0.23 (0.17, 0.30), 0.02 (0.00, 0.05) and 1.50 (1.50, 1.65), respectively. For the LD-SoftK condition, the respective values were 0.36 (0.27, 0.44), 0.09 (0.05, 0.13) and 1.50 (1.50, 1.60). SD-SoftK lenses significantly improved 10VA compared with habitual and LD-SoftK. SD-SoftK also significantly improved CS compared with habitual, but not LD-SoftK. LD-SoftK significantly improved spherical aberration compared with uncorrected (0.03 ± 0.10 μ vs. 0.07 ± 0.13 μ) but not SD-SoftK (0.04 ± 0.07 μ). Both lenses required a mean of 1.5 modifications prior to final lens fitting. Fewer adverse events were seen with SD-SoftK (N = 3) compared with LD-SoftK (N = 8), and 75% of participants preferred SD-SoftK lenses.

CONCLUSION

SD-SoftK lenses were preferred by 75% of subjects, were associated with fewer adverse events and significantly improved 10VA compared with LD-SoftK lenses. SD-SoftK lenses also significantly improved CS compared with the habitual correction, but this did not differ significantly from the LD-SoftK lenses.

Awareness of Keratoconus and Its Relationship With Eye Rubbing Among the Population of the Eastern Province of Saudi Arabia

BACKGROUND

Keratoconus is an eye condition where the cornea, the clear, dome-shaped front part of the eye, becomes thinner and gradually bulges outward into a cone shape. Keratoconus usually affects both eyes. The exact cause of keratoconus is unknown, but it is believed to involve a combination of genetic and environmental factors.

AIM

This study aims to assess the awareness level of keratoconus and its relation to eye rubbing among the population in the Eastern Province of Saudi Arabia.

METHODS

A cross-sectional study was conducted in the Eastern Province of Saudi Arabia, involving all eligible participants via an online pre-designed questionnaire from March to June 2023. The data were collected through social media.

RESULTS

A total of 388 eligible participants completed the study questionnaire. Participants' ages ranged from 19 to 60 years, with a mean age of 26.2 ± 13.9 years. There were 265 (68.3%) female participants. Regarding public awareness about keratoconus among participants in the Eastern Province of Saudi Arabia, our research revealed a total of 101 (26%) participants had an overall good awareness of keratoconus, while 287 (74%) had a poor awareness level. The most reported source of information included scientific lectures (21.6%). Precisely, 316 (81.4%) of the research subjects rub their eyes primarily because of allergies (7%), strain headaches (25%), and itching (66.5%).

CONCLUSION

Most of the study participants have poor awareness about keratoconus and its relation to eye rubbing. Health education programs for the population should be conducted to enhance public awareness about keratoconus.

A Cross-Sectional Analysis to Assess the Role of Atopy in Keratoconus Among Saudi Population

Background

In cases of atopy, IgE antibodies are formed in reaction to certain environmental factors like house dust mites, pollen, or even food allergens. Some studies have shown an association between atopic diseases and keratoconus. This study aims to determine the prevalence of atopy and its associated factors among keratoconus patients.

Materials and Methods

A cross-sectional study was conducted among the Jazan population attending ophthalmology clinics regardless of their sex. Data collection started in August 2020 and finished in mid-June 2021. The sample was selected using the convenience sampling technique, and the total sample size was 83 participants. Data were collected via a questionnaire-based interview that contained 46 questions in the Arabic language. The data collected were analyzed using SPSS software.

Results

Family history is the leading predisposing factor for keratoconus (P < 0.001). Also, eye rubbing was a significant (P < 0.015) trigger for keratoconus. However, other factors, including demographic factors such as gender and atopic conditions, did not have any significant association.

Conclusion

A combination of genetic and environmental factors is the leading cause of the development of keratoconus; however, family history is the most influential factor, followed by eye rubbing.

Awareness of Keratoconus and Its Association With Eye Rubbing Among the Population in Aseer Province

BACKGROUND

Keratoconus (KC), is a non-inflammatory, bilateral, asymmetrical, progressive disease characterized by ectasia, thinning, increasing corneal curvature, and loss of visual acuity. In Saudi Arabia, it was discovered that KC has been the main reason for corneal transplantation in the past 20 years. Eye rubbing is considered one of the most significant risk factors for KC based on available data.

PARTICIPANTS AND METHODS

A cross-sectional study was conducted among adults in Aseer province, Saudi Arabia in 2023. Data were collected through a pre-designed online questionnaire consisting of 17 questions divided into three sections. The questionnaire was preceded by informed consent and insured to maintain the confidentiality of the data.

RESULTS

A total of 498 respondents were included in this study. The majority of the study's participants were in the 18 to 25 age group and females made up the majority. The majority of participants had a university education. 41.6% of individuals reported experiencing an allergic disorder, 59.0% reported having knowledge about KC, and the overall participants' awareness regarding KC was poor at 85.74%, with the highest percentage of good awareness (22.2%) detected among the 18-25 age group.

CONCLUSION

The study revealed a concerning lack of awareness about KC among the population in Aseer Province, Saudi Arabia. Additionally, a significant percentage of participants engaged in eye rubbing, a behavior associated with increased risk for KC. There is a need for increased awareness about KC and the importance of avoiding eye rubbing.

The association between keratoconus and allergic eye diseases: A systematic review and meta-analysis

BACKGROUND

To investigate the association between keratoconus (KC) and allergic eye diseases, eye rubbing, and atopy.

METHODS

PubMed, Web of Science, Scopus, and Cochrane databases were searched for studies investigating eye allergy, atopy, and eye rubbing as risk factors for KC up to April 2021. Two authors independently screened all titles and abstracts against the predefined inclusion and exclusion criteria. The study analysed the prevalence of KC and its risk factors, including eye rubbing, family history of KC, atopy, and allergic eye diseases. The National Institutes of Health Study Quality Assessment Tool was used. Pooled data are presented as odds ratios (OR) and 95% confidence intervals (CI). The analysis was conducted using RevMan version 5.4 software.

RESULTS

The initial search yielded 573 articles. After screening, 21 studies were identified for qualitative analysis and 15 for quantitative synthesis. A significant association was found between KC and eye rubbing (OR = 5.22, 95% CI [2.80, 9.75], p < 0.00001), family history of KC (OR = 6.67, 95% CI [4.77, 9.33], p < 0.00001), and allergies (OR = 2.21, 95% CI [1.57, 3.13], p < 0.00001). However, no significant association was found between KC and allergic eye disease (OR = 1.82, 95% CI [0.37, 8.97], p = 0.46), atopy (OR = 1.54, 95% CI [0.58, 4.09], p = 0.39), allergic rhinitis (OR = 0.85, 95% CI [0.54, 1.33], p = 0.47), smoking (OR = 0.96, 95% CI [0.76, 1.21], p = 0.73), and asthma (OR = 1.58, 95% CI [0.99, 2.53], p = 0.05).

CONCLUSION

Significant associations were observed between KC and eye rubbing, family history, and allergy, but not with allergic eye disease, atopy, asthma, and allergic rhinitis.

Self-reported knowledge and skills related to diagnosis and management of keratoconus among public sector optometrists in the Limpopo province, South Africa

BACKGROUND

Keratoconus (KC) has been regarded as a rare condition, although recent studies, including those in South Africa, suggest it is common and is increasing in prevalence. Furthermore, South African-based studies have shown that KC is normally detected at advanced or severe stages. Knowledge and skills for examination, diagnosis and management of KC by optometrists are important for the early detection and management of the disease.

AIM

This study aimed to evaluate self-reported knowledge and skills for examination, diagnosis and management of KC patients among public sector optometrists.

SETTING

Seven public hospitals of the Capricorn district of the Limpopo province, South Africa.

METHODS

A quantitative cross-sectional descriptive study design was used. A self-administered online questionnaire was used to collect data on demographic characteristics of participants and their knowledge, skills and practice for the diagnosis and management of KC.

RESULTS

Twenty-four optometrists (n = 24) with a mean age of 39 ± 5.67 years, 18 (75%) of whom were female, participated in the study. Nineteen (79%) reported that their hospitals did not have the appropriate equipment to examine, diagnose and manage KC patients. Lack of equipment, poor knowledge, skills and competencies, hospital's level of services, policy and lack of interest were cited as barriers to contact lens fittings in KC patients. Using a dichotomised summation of self-reported knowledge and skills of KC, 13 (54.2%) of the optometrists were knowledgeable and skilled on risk factors of KC and examining, diagnosing and managing KC patients.

CONCLUSION

A significant proportion of optometrists did not have the appropriate knowledge and skills to examine, diagnose and manage KC patients. Lack of equipment and poor knowledge and skills were the main barriers to contact lens fittings in managing KC.Contribution: This article highlights the need for the district to upskill the optometrists through a structured programme with a theory and practical component and also provide the necessary equipment to enhance patient care.

Prevalence of Keratoconus and Keratoconus Suspect among Patients Seeking Refractive Surgery in Syria

PURPOSE

The purpose of this study was to determine the prevalence of keratoconus (KC) and keratoconus suspect (KCS) among patients seeking refractive surgery in Syria.

METHODS

This is a retrospective multicenter screening study. The study was conducted in Damascus University, Tishreen University, and Tartous Specialist Eye Center (a private center). Data were collected from refractive surgery candidates referred for preoperative evaluation before laser in situ keratomileusis, photorefractive keratectomy, intrastromal corneal rings, and phakic intraocular lens implantation. Corneal parameters were obtained by Scheimpflug-Placido tomography, Sirius (CSO, Italy).

RESULTS

A total of 1479 patients were included in this analysis. The prevalence rates of KC and KCS were 18.19% (269/1479) and 13.52% (200/1479), respectively. In addition, patients with KC were found to have higher percentages of eye rubbing and astigmatism than suspect and normal (P < 0.0001).

CONCLUSION

High prevalence rate of KC was found among patients seeking refractive surgery in Syria. Although this study was carried out on a highly selective population, it may reflect a high prevalence rate in a general population in Syria.

The Underlying Relationship between Keratoconus and Down Syndrome

Keratoconus (KC) is one of the most significant corneal disorders worldwide, characterized by the progressive thinning and cone-shaped protrusion of the cornea, which can lead to severe visual impairment. The prevalence of KC varies greatly by ethnic groups and geographic regions and has been observed to be higher in recent years. Although studies reveal a possible link between KC and genetics, hormonal disturbances, environmental factors, and specific comorbidities such as Down Syndrome (DS), the exact cause of KC remains unknown. The incidence of KC ranges from 0% to 71% in DS patients, implying that as the worldwide population of DS patients grows, the number of KC patients may continue to rise significantly. As a result, this review aims to shed more light on the underlying relationship between KC and DS by examining the genetics relating to the cornea, central corneal thickness (CCT), and mechanical forces on the cornea, such as vigorous eye rubbing. Furthermore, this review discusses KC diagnostic and treatment strategies that may help detect KC in DS patients, as well as the available DS mouse models that could be used in modeling KC in DS patients. In summary, this review will provide improved clinical knowledge of KC in DS patients and promote additional KC-related research in these patients to enhance their eyesight and provide suitable treatment targets.

The association between keratoconus and allergic eye diseases: A systematic review and meta-analysis

BACKGROUND

To investigate association between keratoconus and allergic eye diseases, eye rubbing, and atopy.

METHODS

PubMed, Web of Science, Scopus, and Cochrane were searched for relevant published studies from inception to April 2021 without restrictions or filters. We included case-control, cohort, and cross-sectional studies that investigated eye allergy, atopy, or eye rubbing as possible risk factors for KC. Two authors independently screened all titles and abstracts against predefined inclusion and exclusion criteria. This study analysed keratoconus prevalence and risk factors including eye rubbing, family history of keratoconus, atopy, and allergic eye diseases. The National Institute of Health Study Quality Assessment tool was utilised. Pooled data were presented as odds ratio (OR) and 95% confidence intervals (CI). Analysis was conducted using RevMan version 5.3 software.

RESULTS

Out of 573 articles, we excluded 161 duplicates than 361 articles by title and abstract screening. The remaining 51 articles underwent full-text screening, and 29 articles were excluded. Twenty-one studies were included in the qualitative synthesis and fifteen for quantitative synthesis. There was no significant association found between KC and allergic eye diseases (OR = 1.03, 95% CI [0.96, 1.11], p = 0.45), eye rubbing (OR = 1.59, 95% CI [0.70, 3.63], p = 0.27), or atopy (OR = 1.08, 95% CI [0.80, 1.44], p = 0.62).

CONCLUSION

No significant association was observed between KC and allergic eye disease, eye rubbing, or atopy. Further prospective studies are needed to clarify and validate these findings.

Oxidative and antioxidative stress markers in keratoconus: a systematic review and meta-analysis

PURPOSE

To conduct a systematic review and meta-analysis on the levels of oxidative stress markers and antioxidants in keratoconus compared to healthy subject.

METHOD

The PubMed, Cochrane Library, Embase, Science Direct and Google Scholar databases were searched on 1st June 2020 for studies reporting oxidative and antioxidative stress markers in keratoconus and healthy controls. Main meta-analysis was stratified by type of biomarkers, type of samples (tears, cornea, aqueous humour and blood) and type of corneal samples (stromal cells, epithelium and endothelium).

RESULTS

We included 36 articles, for a total of 1328 keratoconus patients and 1208 healthy controls. There is an overall increase in oxidative stress markers in keratoconus compared with healthy controls (standard mean deviation (SMD) = 0.94, 95% confidence interval (95% CI) 0.55-1.33), with a significant increase in reactive oxygen and nitrogen species (1.09, 0.41-1.78) and malondialdehyde (1.78, 0.83-2.73). There is an overall decrease in antioxidants in keratoconus compared with healthy controls (-0.63, -0.89 to -0.36), with a significant decrease in total antioxidant capacity/status (-1.65, -2.88 to -0.43), aldehyde/NADPH dehydrogenase (-0.77, -1.38 to -0.17), lactoferrin/transferrin/albumin (-1.92, -2.96 to -0.89) and selenium/zinc (-1.42, -2.23 to -0.61). Oxidative stress markers were higher in tears and in cornea of keratoconus than in aqueous humour, and antioxidants were decreased in tears, aqueous humour and blood without difference between sample type. Oxidative stress markers increased in stromal cells and antioxidants decreased in endothelium.

CONCLUSION

Oxidative stress markers and antioxidants were dysregulated in keratoconus, involving an imbalance of redox homeostasis in tears, cornea, aqueous humour and blood.

Eye Rubbing and Transient Corneal Ectasia Detected by Topography in a Pediatric Patient

ABSTRACT

We report on a 13-year-old girl undergoing changes in the refraction of her OS associated with eye rubbing. Corneal topography showed a corneal deformation in OS, classified as stage 1 keratoconus according to the Krumeich classification. A significant reduction in eye rubbing led to a normal corneal shape at the 1-year follow-up. Transient and fully reversible corneal ectasia can be caused by eye rubbing in pediatric age. This may have implications when counseling very young patients with eye rubbing.

Why a dedicated section on keratoconus in the European Journal of Ophthalmology?

Keratoconus is emerging as a new subspecialty in ophthalmology. The literature is booming with publications on the topic as we have better understanding of the pathophysiology, treatment and prognosis of the disease over the past two decades. Advances in diagnostic tools as well as genuine increase in prevalence have shifted perspective of the disease from being a rare one. Early diagnosis is of public health interest as early treatment arrests progression. With the view to encourage research, increase awareness and to reflect the evolution of knowledge related to keratoconus, the European Journal of Ophthalmology has dedicate a special section on keratoconus in its journal.

Keratoconus concordance in monozygotic twins before and after combined CXL/PRK (Athens Protocol) using Scheimflung and OCT tomography

PUPOSE

To describe the concordance of keratoconus expression in two pairs of monozygotic twins before and after a combined CXL/PRK procedure.

SETTING

Private Ambulatory Eye Surgery Unit.

DESIGN

Retrospective Interventional Twin Study.

METHODS

Two pairs of male monozygotic twins with keratoconus (KCN) were studied retrospectively. Improvement of flattest (k1) and steepest (k2) keratometry, Index of Height Decentration (IHD), corneal thickness at thinnest point and corneal epithelial thickness measured by AS-OCT and Scheimpflug tomography was compared between respective eyes of monozygotic twin siblings 1 to 5 years after the application of combined corneal cross linking (CXL) and topography guided photorefractive keratectomy (PRK) of part of the refractive error (the Athens Protocol).

RESULTS

Significant improvement was noted in all the keratometric indices of all 8 eyes after the combined CXL/PRK procedure.The difference in k1, k2, IHD corneal thickness at thinnest point and corneal epithelial thickness percentage improvement between the right eyes of each pair of twins was statistically significant 1 and 5 years post-operatively (P < .05). Statistically significant discordance in the aforementioned parameters percentage improvement was likewise observed between the left eyes of each pair of twins (P < .05).

CONCLUSIONS

Although a genetic predisposition in KCN is well documented, the discordance in keratometric indices improvement after a CXL/PRK procedure between respective eyes of monozygotic twins suggests that environmental influences may contribute to the disease expression as well. Variable degree of synergy in a combined CXL/PRK procedure may also explain the aforementioned discordant improvement.

Spectrum of Binocular Vision Anomalies in Keratoconus Subjects

Keratoconus (KC) is typically a bilateral asymmetric corneal condition associated with anisometropia. A detailed evaluation of binocular vision function is therefore a critical component of ocular examination in these patients for early detection and treatment of binocular vision anomalies.

PURPOSE

The purposes of this study were to measure the various parameters of binocular vision (BV) in patients with KC and to identify the factors that possibly influence them.

METHODS

This was a prospective, observational study of BV in patients with KC and with best-corrected visual acuity ≤0.4 logMAR in each eye. Age-matched, nonstrabismic normal patients served as controls. Binocular vision examination included motor assessment, accommodation parameters, and fusional vergence.

RESULTS

Binocular vision parameters of 84 KC patients were compared with those of 71 normal controls. The KC group showed statistically significant differences between fellow eyes in refractive cylinder (0.44 ± 2.1 D, P = .03), best-corrected visual acuity (0.06 ± 0.09 logMAR, P = .001), and maximum keratometry (6.64 ± 8.2D, P = .005). The control group showed no significant difference in any refractive or keratometric parameter between fellow eyes. Sixty-six (78.6%) of 84 KC patients had various combinations of BV anomalies: 48.8% had impaired stereopsis, 44% had abnormal fusional vergence, and 39.3% had accommodative infacility. Among individual parameters, all except accommodative amplitudes and negative distance fusional vergence showed statistically significant impairment compared with controls (P < .001). Median (interquartile range) stereoacuity was 70 (50 to 550) arc sec in the KC group and 40 (30 to 50) arc sec in control (P < .0001). There was a statistically significant but weak correlation between stereoacuity and positive fusional vergence for near (P = .008; Spearman coefficient, -0.28) and weak but significant negative correlation between phoria status and negative fusional vergence for near (P = .03; Spearman coefficient, -0.24).

CONCLUSIONS

A large proportion of KC patients have BV anomalies. Assessment of BV function should be included in the clinical examination of all KC patients.

The Association Between Keratoconus and Body Mass Index: A Population-Based Cross-Sectional Study Among Half a Million Adolescents

PURPOSE

To analyze the association between keratoconus and body mass index (BMI) among adolescents.

DESIGN

Cross sectional study.

METHODS

This was a nationwide, population-based study of candidates for military service in Israel attending the draft board in 2006 to 2014 who underwent an ophthalmologic examination. The study population included 579,946 males and females between 16 and 19.9 years of age. Subjects were divided into 4 groups based on adjusted BMI percentiles: underweight (8.3%), normal weight (73.9%), overweight (10.7%), and obese (7.1%). The odds for having keratoconus were compared with the normal weight group. The primary outcome measure was the odds ratio (OR) for the association between BMI groups and keratoconus.

RESULTS

The prevalence of keratoconus in the general population was 164 cases per 100,000, increasing over time (P < .05). There was a greater prevalence of keratoconus among obese adolescents (270/100,000) than of overweight (179/100,000), normal weight (154/100,000), and underweight (141/100,000) adolescents. Compared with the normal weight group, the OR for obese adolescents was 1.50 (95% confidence interval [CI] 1.22-1.83; P < .05), the OR for overweight adolescents was 1.42 (95% CI 1.08-1.92; P < .05), and the OR for underweight adolescents was 0.84 (95% CI 0.65-1.09; P = .18) after adjustment for gender, age, height, country of origin, and socioeconomic status.

CONCLUSIONS

This study provides strong evidence regarding the independent association between BMI and keratoconus. Overweight and obese adolescents have higher odds of having keratoconus compared with normal weight adolescents. BMI should be considered a risk factor for keratoconus and further research should elucidate how obesity is involved in the progress of keratoconus.

Clinical outcomes after intracorneal ring segment implantation for keratoconus management in corneas with mild apical haze

Purpose:

The implantation of intracorneal ring segments represents an effective and safe therapeutic option for visual improvement in patients with keratoconus. The presence of corneal opacities is considered an exclusion criterion for this operation.

Methods:

This is a retrospective cohort study of six eyes of six keratoconus patients at Queen Victoria Hospital, East Grinstead, UK, between January 2012 and December 2016. Femtosecond laser-assisted intracorneal ring segment implantation was performed in six eyes with apical corneal haze. Preoperative and postoperative visual acuity, keratometry readings, as well as corneal pachymetry were compared at 6-month follow-up.

Results:

Uncorrected visual acuity (UCVA) [LogMAR] improved significantly from median 1.05 [95% confidence interval (CI): 0.83–0.13] preoperatively to 0.9 (95% CI: 0.63–1.00) at 6 months postoperatively (p = 0.03). Corrected visual acuity (CDVA) also improved significantly from median 0.75 (95% CI: 0.43–1.00) preoperatively to 0.4 (95% CI: 0.23–0.50) at 6 months postoperatively (p = 0.03). Keratometric readings, K-max (diopters) and K-mean (diopters), decreased significantly from 54.5 and 47.85 preoperatively to 53.45 and 46.42 postoperatively, respectively (p = 0.03). Corneal pachymetry showed no significant changes postoperatively.

Conclusion:

The results of this study show that the presence of apical haze should not exclude the implantation of intracorneal ring segments in patients with keratoconus.

Corneal endothelial cells changes in different stages of Keratoconus: a multi-Centre clinical study

Purpose

To assess the corneal endothelial cells morphology and count in keratoconus patients and their correlation with different stages of keratoconus.

Methods

Prospective non randomized multi-centric clinical study included 150 eyes of 150 keratoconus patients. Four centers in Egypt participated in this study included: Departments of Ophthalmology in Alexandria University, Tanta University and Port Said University and Alex I-Care hospital. Pentacam (Wavelight Oculyzer II) and specular microscopy (Tomey EM-3000) were done to all eyes. Keratoconic eyes were classified according to Amsler classification into stage 1, 2 and 3. Stage 1 included 99 eyes, stage 2 included 32 eyes & stage 3 included 19 eyes.

Results

The mean age of keratoconus patients was 24.07 ± 6.154 years. Forty five cases were males (30%) and 105 cases were females (70%). There was statistically significant difference in endothelial cell density (p < 0.001) and coefficient of variation (p = 0.012) between different stages of keratoconus eyes. Regarding cell surface area, there was statistically significant difference in cell surface area between different stages of keratoconus eyes (p < 0.001). In addition, for cell morphology, there was statistically significant difference between different stages of keratoconus eyes (p < 0.001).

Conclusions

Qualitative and quantitative structural changes were seen in endothelial cells of keratoconus eyes by using specular microscopy. For stages 1 and 2, keratoconus may not affect the corneal endothelim significantly. The endothelium in stage 3 shows significant changes regarding polymegathism and pleomorphism.

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.

Eye rubbing in the aetiology of keratoconus: a systematic review and meta-analysis

PURPOSE

Keratoconus is a potentially blinding condition that slowly deforms the cornea in young people. Despite the increasing prevalence of keratoconus, the exact aetiology of the condition is unknown. This first systematic review examines the evidence of eye rubbing and its association with keratoconus and presents the findings of the meta-analysis.

METHODS

Two independent reviewers searched the electronic databases for all potential articles published from 1st of January 1900 to 31st of July 2020 on eye rubbing and keratoconus. The researchers assessed the methodological quality of the studies using the Newcastle-Ottawa scale for observational studies. The assessment for statistical heterogeneity was estimated using chi-square and I-square (I²) tests. A p value of < 0.05 was considered as statistically significant and I² < 30% as homogenous. Begg funnel plot was used to interpret the asymmetry or small study effects.

RESULTS

Eight case-control studies were included in this systematic review. Two studies assessed eye rubbing without odds ratios and thus were excluded. The pooled odds ratios for the six remaining studies included in the meta-analysis was 6.46 (95% CI 4.12-10.1). The study results were heterogenous (I² = 71.69 [95% CI 35.14-87.88]). All the studies scored moderate quality methodology on the Newcastle-Ottawa scale. Begg funnel plot showed asymmetry supporting heterogeneity.

CONCLUSION

Eye rubbing showed consistent association with keratoconus. However, the current evidence is limited to only a small number of case-control studies which present as heterogeneous and of sub-optimal methodological quality. Additionally, the cause-effect temporal relationship cannot be determined. Further studies are needed to address this intricate relationship of eye rubbing and its induction, ongoing progression, and severity of keratoconus.

Characterization of posterior corneal astigmatism in a population with keratoconus

Background: The curvature of the anterior corneal surface is traditionally used as a surrogate to estimate corneal astigmatism. In recent years, increasing importance has been attributed to posterior corneal astigmatism as an indicator. Our aim is to characterize the posterior corneal surface in a population with keratoconus and investigate its predictive value to keratoconus progression. Methods: Retrospective study from a tertiary care centre (Hospital de Santa Maria, Lisbon, Portugal). Eighty-five patients (85 eyes) with keratoconus were included. All patients had two tomographical examinations ≥12 months apart (Pentacam HR). Vector analysis was used to calculate anterior (ACA), posterior (PCA), and total corneal astigmatism (TCA). Multivariate logistic regression was used to assess the predictive value of PCA to keratoconus progression, adjusting for ACA, TCA and several tomographical indices. Results: Study participants had a mean age of 32 (SD = 12.5) years. Mean tomographical keratoconus classification was 2.16 (SD = 0.95), with a mean Kmax of 55.8D (SD = 7.8). Mean power of PCA, ACA and TCA was, respectively, -0.88D (SD = 0.84), 3.74D (SD = 2.36), and 3.06D (SD = 2.01) and its centroids were 0.44D x 15º, 1.65D x 112º, and 1.61D x 106º, respectively. The power of PCA was ≥0.50, 1.00 and 2.00D in 75.3%, 32.9%, and 3.5% of patients, respectively, inducing against-the-rule astigmatism in 60.0% of patients. On average, ACA overestimated TCA in 0.35D x 151º (p < .01). ACA and TCA were highly correlated but showed a lack of agreement for clinical purposes. A predictive role for PCA was excluded. Conclusions: In this population with keratoconus, PCA contributed substantially to TCA. However, PCA was not a valuable predictor for disease progression.

Incorrect sleeping position and eye rubbing in patients with unilateral or highly asymmetric keratoconus: a case-control study

PURPOSE

To evaluate eye rubbing and sleeping position in patients with Unilateral or Highly Asymmetric Keratoconus (UHAKC).

METHODS

Case-control study of consecutive UHAKC patients diagnosed at the Rothschild Foundation. Controls were age- and sex-matched, randomly selected refractive surgery clinic patients. Patients self-administered questionnaires regarding their family history of keratoconus, eye rubbing, and sleeping habits. All the eyes underwent a comprehensive ocular examination. Logistic regression was used to analyze univariate and multivariate data to identify risk factors for keratoconus.

RESULTS

Thirty-three UHAKC patients and 64 controls were included. Univariate analyses showed that daytime eye rubbing [OR = 172.78], in the morning [OR = 24.3], or in eyes with the steepest keratometry [OR = 21.7] were significantly different between groups. Allergy [OR = 2.94], red eyes in the morning [OR = 6.36], and sleeping on stomach/sides [OR = 14.31] or on the same side as the steepest keratometry [OR = 94.72] were also significantly different. The multivariate model also showed statistical significance for most factors including daytime eye rubbing [OR = 134.96], in the morning [OR = 24.86], in the steepest eye [OR = 27.56], and sleeping on stomach/sides [OR = 65.02] or on the steepest side [OR = 144.02]. A univariate analysis in UHAKC group, comparing the worse and better eye, showed that eye rubbing [OR = 162.14] and sleeping position [OR = 99.74] were significantly (p < 0.001) associated with the worse eye.

CONCLUSION

Our data suggests that vigorous eye rubbing and incorrect sleeping position are associated with UHAKC. This is especially true in rubbing the most afflicted eye, and contributory sleep position, including positions placing pressure on the eye with the steepest keratometry.

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.

Keratoconus with Central Serous Chorioretinopathy: A Rare Combination

Keratoconus and central serous chorioretinopathy are two rare diseases. They can occur together in some individuals. We report a case of a 48-year-old man, who presented to our clinic with decreased visual acuity on his left eye. Physical examination, biomicroscopy, corneal topography, and optical coherence tomography revealed keratoconus and central serous chorioretinopathy. We discuss the possible connection between these two conditions.

Three novel variants identified within ECM-related genes in Chinese Han keratoconus patients

As the primary indication for corneal transplantation, the pathogenesis of keratoconus remains elusive. Aiming to identify whether any mutation from extracellular-matrix (ECM)-related genes contributes to the patients with sporadic cases of keratoconus (KC) from Chinese Han population, one hundred and fifty-three participants in total were enrolled in our study, including fifty-three KC patients and one hundred healthy controls. Mutational analysis of three ECM-related genes (LOX, COL5A1 and TIMP3) with next-generation sequencing and Sanger sequencing was performed. To further confirm the function of three ECM-related genes in the pathogenesis of keratoconus, we performed Real-time Quantitative PCR in vitro. Results showed that three new sequence variants (c.95 G > A in LOX, c.1372 C > T in COL5A1 and c.476 C > T in TIMP3) were identified in aforementioned ECM-related genes in KC patients without being detected among the healthy controls. According to the results of QPCR, we found that the expression levels of LOX and TIMP3 were decreased in the KC patients, while COL5A1 showed no significant difference of expression. This is the first time to screen so many ECM-related genes in Chinese keratoconus patients using next-generation sequencing. We find numerous underlying causal variants, enlarging lots of mutation spectrums and thus providing new sites for other investigators to replicate and for further research.

Long-Term Stability With the Athens Protocol (Topography-Guided Partial PRK Combined With Cross-Linking) in Pediatric Patients With Keratoconus

PURPOSE

To evaluate the safety, efficacy, and stability of topography-guided partial PRK combined with corneal cross-linking (CXL) (the Athens Protocol [AP]) in pediatric patients with keratoconus over a 4-year follow-up period.

METHODS

This prospective study included 39 keratoconic eyes of 21 patients younger than 18 years with clinical and imaging evidence of keratoconus progression. Partial topography-guided excimer laser ablation in conjunction with high-fluence CXL was performed in all patients according to the AP. Uncorrected distance visual acuity, corrected distance visual acuity, refraction, keratometry, endothelial cell density, topography, and tomography using both Scheimpflug and optical coherence tomography (OCT) were evaluated for 4 years postoperatively.

RESULTS

At 4 years postoperative, there was significant improvement in mean uncorrected distance visual acuity from 0.51 ± 0.31 (decimal) to 0.65 ± 0.26 (decimal; P < 0.05). Mean corrected distance visual acuity improved from 0.71 ± 0.22 (decimal) preoperatively to 0.81 ± 0.19 (decimal; P < 0.05), respectively. Mean flat keratometry (K1) and mean steep keratometry (K2) readings reduced from 44.95 ± 3.71 D and 49.32 ± 5.05 D, respectively, preoperatively to 43.14 ± 2.95 D and 46.28 ± 4.87 D, respectively, (P < 0.05) at 4 years. The mean anterior maximum keratometry (Kmax) reading reduced from 56.81 ± 2.94 D preoperatively to 48.11 ± 3.17 D at 48 months. The mean index of height decentration was 0.105 ± 0.054 μm preoperatively and 0.049 ± 0.024 (P < 0.05) at 4 years postoperative. Mean preoperative corneal thickness at the thinnest point was 436.7 ± 42.6 μm preoperatively, 392.50 ± 45.68 μm at 12 months postoperative, and 418.42 ± 17.01 μm at 4-year follow-up. Late-onset deep corneal haze, a potential intrinsic complication of this technique in pediatric patients, was encountered in 2 cases at least 1 year after the procedure.

CONCLUSIONS

Long-term results of the AP seem to be safe and effective in pediatric patients, with marked improvement in visual function and keratometric symmetry indices.

Preliminary demographics for patients with keratoconus attending a university-based clinic in Johannesburg, South Africa

Background: Keratoconus (KC) is a visually debilitating disease if left undiagnosed and untreated. Early intervention is necessary to ensure a good quality of life for those afflicted by the disease. Although much research has been done in other parts of the world, there is a paucity in the literature that describes the disease from a South African perspective.Aim: The aim of this study was to provide the demographics of KC patients attending a university-based contact lens clinic between January 2007 and December 2017.Setting: Patients diagnosed with KC (N = 206) at a university-based contact lens clinic in Johannesburg, South Africa, were included in this analysis.Methods: A retrospective analysis of clinical records of 206 KC patients was conducted. Demographic data on race, gender, age and severity of disease were analysed and presented.Results: The majority of patients with KC that attended the clinic were female (53%), of mainly African (74%) descent and in their second decade of life. The average age at first visit was 24.0 ± 8.53 and 22.9 ± 7.46 years for males and females, respectively. There was no significant difference in average age between male and female patients (p 0.05). Patients in the first and second decade of life presented at first visit with a greater severity of disease when compared with those in the third decade or older.Conclusion: There is a dire need for larger epidemiological studies to be conducted on South African patients with KC so that early intervention becomes possible. This would greatly influence the quality of life for these patients and positively impact the socio-economic status of the country.

Characteristics of keratoconic patients at two main eye centres in Palestine: a cross-sectional study

BACKGROUND

Keratoconus (KC) is a multifactorial, degenerative ectatic condition of the cornea. It usually manifests during late adolescence or the early twenties. A painless disease, KC may end with severe visual loss. The prevalence of KC in middle-eastern countries is much higher than in other regions of the world. This may be due to genetic and environmental risk factors and consanguinity. The goal of this study is to explore the demographic profile of Palestinian keratoconic patients.

METHODS

A retrospective study was conducted in two ophthalmology centres (Tertiary Ophthalmic Centre of An-Najah National University Hospital and An-Noor Centre at the Specialized Arab Hospital). All medical charts of keratoconic patients attending both centres over the period from 2009 to 2016 were reviewed. These patients were diagnosed by ophthalmologists depending on history, examination and Pentacam. Severity was determined using the k median index from the Pentacam map. Data analysis was carried out using SPSS Version 22.

RESULTS

The medical files of 936 keratoconic eyes of 505 keratoconic patients were reviewed. Their mean age at the time of diagnosis was 23.3 ranging from 8 to 62 years. Approximately 70.1% of them presented after the age of 20 years, and younger age groups were more likely to develop a severe disease stage than older ones (P = 0.001, r = - 0.108). There was a nearly equal distribution of patients between the two sexes (49.5% male, 50.5% female). On initial evaluation, the best-corrected visual acuity (BCVA) was recorded as ≥6/12 in most affected eyes (71.5%). Regarding severity, 62% presented in a mild form, while 9.9% were at a severe stage. About 88.2% presented with bilateralism.

CONCLUSIONS

Most of the patients in their twenties presented with a mild bilateral form of the disease. This result is compatible with published international reports. It is recommended that the results of this study be considered when establishing a screening program in Palestine. Subsequently, patients will be identified at an appropriate time where action can be taken before disease progression take place.

Three-Year Outcomes of Cross-Linking PLUS (Combined Cross-Linking with Femtosecond Laser Intracorneal Ring Segments Implantation) for Management of Keratoconus

Purpose

To analyze the results of three-year outcomes of combined epithelium-on cross-linking with femtosecond laser ICRS (cross-linking PLUS) for keratoconus management.

Design

A retrospective multicenter clinical study.

Methods

43 eyes of 38 patients were subjected to preoperative and postoperative UCVA, BCVA, refraction, Pentacam pachymetry, and keratometry examinations at 3-, 6-, 12-, 24-, and 36-month follow-up period.

Results

The preoperative and postoperative mean UCVA was 1.30 ± 0.48 (logMAR ± SD) and 0.82 ± 0.22 respectively. The preoperative and postoperative mean BCVA was 0.90 ± 0.40 and 0.60 ± 0.30, respectively. The preoperative and postoperative mean K average was 50.63 ± 0.87 (D ± SD) and 45.56 ± 0.98, respectively. The preoperative and postoperative mean pachymetry was 471 ± 92.36 (μm ± SD) and 423 ± 39.58, respectively. The preoperative and postoperative mean astigmatism was 7.55 ± 1.75 and 3.39 ± 1.26, respectively. One eye showed ICRS edge exposure while 6 eyes showed progression of keratoconus.

Conclusion

CXL PLUS was proved to be a successful procedure to halt progression (mainly by CXL) and to correct the refractive status of the keratoconic eye (mainly by ICRS). CXL PLUS performed a synergistic action correcting and maintaining the correction of both myopic and astigmatic components of keratoconus.

The genetic and environmental factors for keratoconus

Keratoconus (KC) is the most common cornea ectatic disorder. It is characterized by a cone-shaped thin cornea leading to myopia, irregular astigmatism, and vision impairment. It affects all ethnic groups and both genders. Both environmental and genetic factors may contribute to its pathogenesis. This review is to summarize the current research development in KC epidemiology and genetic etiology. Environmental factors include but are not limited to eye rubbing, atopy, sun exposure, and geography. Genetic discoveries have been reviewed with evidence from family-based linkage analysis and fine mapping in linkage region, genome-wide association studies, and candidate genes analyses. A number of genes have been discovered at a relatively rapid pace. The detailed molecular mechanism underlying KC pathogenesis will significantly advance our understanding of KC and promote the development of potential therapies.

A frequency analysis of cone characteristics for the different stages of keratoconus

Background: The stages of keratoconus can be classified according to the degree of corneal conicity as either early or advanced, or morphologically by the shape of the cone. Knowledge of the different cone characteristics for the different stages of keratoconus may assist practitioners in diagnosing and managing these patients.Aim: To describe the cone characteristics for the different stages of keratoconus.Methods: In this retrospective study, a sample of 190 eyes from 106 cases of previously diagnosed keratoconic patients was analysed. The stage of keratoconus and cone characteristics, namely: cone location, cone decentration, morphology, and topographical patterns were analysed using an Oculus 3M corneal topographer.Results: Our study revealed that for all stages of keratoconus centrally located cones were the most frequent, with corneal apical decentration between 0 mm and 2 mm. Frequency analysis revealed that nipple cones were most frequent in all stages. Topographical pattern frequencies revealed a wide distribution amongst the different corneal patterns in all stages of keratoconus.Conclusion: Cone analysis should be of consideration to the contact lens practitioner when deciding on management of the condition. It additionally serves to compliment the clinical signs such as nerve visibility, Fleischer’s ring, Vogt’s striae and corneal scarring.

Intrastromal corneal ring segment implantation (keraring 355°) in patients with central keratoconus: 6-month follow-up

We evaluate the efficacy and safety of Keraring 355° intrastromal corneal ring segment (ICRS) implantation aided by PocketMaker microkeratome for the correction of keratoconus. Patients underwent ICRS insertion using mechanical dissection with PocketMaker microkeratome and completed 6 months of follow-up. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, topographic findings, safety, efficacy index, and adverse events were reported for six months postoperatively. We evaluated 15 eyes of 15 patients (12 men) with a mean age of 28.87 ± 6.94 years (range 21–49 years). At final postoperative examination, there was a statistically significant reduction in the spherical equivalent refractive error compared to preoperative measurements (−5.46 ± 1.52 to −2.01 ± 1.63 D, P < 0.001). Mean preoperative UCVA (logMAR) before implantation was 0.79 ± 0.48, and postoperative UCVA was 0.28 ± 0.15, P = 0.001. Mean preoperative BSCVA (logMAR) before implantation was 0.36 ± 0.21; at final follow-up examination BSCVA was 0.18 ± 0.9, P = 0.009. Mean K decreased from 48.33 to 43.31 D, P < 0.001. All patients were satisfied with ICRS implantation; 86.7% were moderately to very happy with the results. No intraoperative or postoperative complications were demonstrated. This preliminary study shows that ICRS (Keraring 355°) implantation is an efficient, cost-effective, and minimally invasive procedure for improving visual acuity in nipple type keratoconic corneas.

Screening for keratoconus suspects among candidates for refractive surgery

This review examines methods for estimating the risk of post-surgical ectasia in candidates for refractive surgery by establishing a diagnosis of keratoconus suspect as a contraindication for proceeding with surgery. Notwithstanding the desirability of achieving 100 per cent sensitivity, any associated reduction in specificity and increased numbers of false positives might deny some candidates the opportunity to proceed with refractive surgery. The introduction of a model for the risk of ectasia involving both pre- and post-surgical findings has been followed by a plethora of attempts to achieve the same purpose based on topographic and/or tomographic evaluation before surgery. The desirability of being able to depend on objective assessment using one type of instrument needs to be weighed against the possibility that subjective assessments may contribute significantly to screening success. For example, consideration of ethnicity, family history of keratoconus, a history of atopy or ocular allergies in particular, a history of significant exposure to corneal trauma associated with abnormal rubbing habits or with vocational, leisure or geographically increased exposure to ultraviolet radiation or with contact lens wear trauma or a history of significant exposure to activities which elevate intraocular pressure may improve screening success. To the extent that these factors could contribute to increased risk of the development of keratoconus, they may be useful in estimating the risk of post-surgical ectasia. If any combination of these factors helps to explain the development of keratoconus in normal or even thicker than normal corneas, they may have more significance for those corneas, which have been thinned surgically.

Keratoconus: tissue engineering and biomaterials

Keratoconus (KC) is a bilateral, asymmetric, corneal disorder that is characterized by progressive thinning, steepening, and potential scarring. The prevalence of KC is stated to be 1 in 2000 persons worldwide; however, numbers vary depending on size of the study and regions. KC appears more often in South Asian, Eastern Mediterranean, and North African populations. The cause remains unknown, although a variety of factors have been considered. Genetics, cellular, and mechanical changes have all been reported; however, most of these studies have proven inconclusive. Clearly, the major problem here, like with any other ocular disease, is quality of life and the threat of vision loss. While most KC cases progress until the third or fourth decade, it varies between individuals. Patients may experience periods of several months with significant changes followed by months or years of no change, followed by another period of rapid changes. Despite the major advancements, it is still uncertain how to treat KC at early stages and prevent vision impairment. There are currently limited tissue engineering techniques and/or "smart" biomaterials that can help arrest the progression of KC. This review will focus on current treatments and how biomaterials may hold promise for the future.

Keratoconus management: long-term stability of topography-guided normalization combined with high-fluence CXL stabilization (the Athens Protocol)

PURPOSE

To investigate refractive, topometric, pachymetric, and visual rehabilitation changes induced by anterior surface normalization for keratoconus by partial topography-guided excimer laser ablation in conjunction with accelerated, high-fluence cross-linking.

METHODS

Two hundred thirty-one keratoconic cases subjected to the Athens Protocol procedure were studied for visual acuity, keratometry, pachymetry, and anterior surface irregularity indices up to 3 years postoperatively by Scheimpflug imaging (Oculus Optikgeräte GmbH, Wetzlar, Germany).

RESULTS

Mean visual acuity changes at 3 years postoperatively were +0.38 ± 0.31 (range: -0.34 to +1.10) for uncorrected distance visual acuity and +0.20 ± 0.21 (range: -0.32 to +0.90) for corrected distance visual acuity. Mean K1 (flat meridian) keratometric values were 46.56 ± 3.83 diopters (D) (range: 39.75 to 58.30 D) preoperatively, 44.44 ± 3.97 D (range: 36.10 to 55.50 D) 1 month postoperatively, and 43.22 ± 3.80 D (range: 36.00 to 53.70 D) up to 3 years postoperatively. The average Index of Surface Variance was 98.48 ± 43.47 (range: 17 to 208) pre-operatively and 76.80 ± 38.41 (range: 7 to 190) up to 3 years postoperatively. The average Index of Height Decentration was 0.091 ± 0.053 μm (range: 0.006 to 0.275 μm) preoperatively and 0.057 ± 0.040 μm (range: 0.001 to 0.208 μm) up to 3 years postoperatively. Mean thinnest corneal thickness was 451.91 ± 40.02 μm (range: 297 to 547 μm) preoperatively, 353.95 ± 53.90 μm (range: 196 to 480 μm) 1 month postoperatively, and 370.52 ± 58.21 μm (range: 218 to 500 μm) up to 3 years postoperatively.

CONCLUSIONS

The Athens Protocol to arrest keratectasia progression and improve corneal regularity demonstrates safe and effective results as a keratoconus management option. Progressive potential for long-term flattening validates using caution in the surface normalization to avoid overcorrection.

Prevalence of Keratoconus among Young Arab students in Israel

Purpose

To determine the prevalence of keratoconus (KC) in an Arab population in Israel.

Materials and methods

Videokeratography was performed on volunteer students from the Academic Arab College of Education, in Haifa, Israel. All participants filled out a self-administered questionnaire to evaluate possible risk factors for KC. Univariate and multivariate analysis were performed.

Results

Data of 314 participants were analyzed and a prevalence of (N = 10), 3.18% (95% CI, 1.2 to 5.1%) was found. The only significant factor (both in univariate and multivariate analysis) that was associated with KC was parental consanguinity (OR 5.10, p = 0.02). Druzes and Bedouins had a higher prevalence than Muslims and Christians. However, the differences were not significant possibly due to the small size of the sample.

Conclusion

The result of this study was similar to other studies conducted in the Middle East, which indicate a higher prevalence of KC than in western countries. It is also recommended that people who have consanguinity in their family should be topographically tested to detect the early stages of KC.

How to cite this article

Shneor E, Millodot M, Gordon-Shaag A, Essa M, Anton M, Barbara R, Barbara A. Prevalence of Keratoconus among Young Arab Students in Israel. Int J Kerat Ect Cor Dis 2014;3(1):9-14.

Is consanguinity a risk factor for keratoconus?

PURPOSE

To determine whether consanguinity is a risk factor for keratoconus (KC).

METHODS

A questionnaire was distributed to all patients presenting to St. John Eye Hospital, Jerusalem, Israel. Questionnaire included data on demographic characteristics and potential risk factors. Patients were divided into two groups: cases with KC, in at least one eye, who were diagnosed by the attending ophthalmologist on the basis of abnormal corneal topography and at least one of the common signs of the disease; and controls presenting for problems other than KC and free of systemic and ocular conditions associated with KC. Multivariate logistic analyses were performed to identify risk factors for KC.

RESULTS

Seventy cases and 140 controls participated in the study. Groups were similar with respect to sex and age. Univariate analyses found a significant association between KC and parental first-cousin consanguinity, eye rubbing, allergy, positive family history, education (>12 years), and sunglass wear, whereas asthma, eczema, smoking, and second-cousin consanguinity were not. Multivariate analyses showed that total consanguinity (first-cousin and second-cousin) (adjusted odds ratio, 3.96; p = 0.001), eye rubbing and absence of sunglass wear were significant risk factors. Education was also associated with KC, but family history was not so in the multivariate analysis.

CONCLUSIONS

This study supports the hypothesis that consanguinity is a significant risk factor for KC and provides strong support for a genetic contribution to the disease. Wearing sunglasses in this environment is beneficial, and the study confirmed that eye rubbing, allergy, and education are also significantly associated with KC after adjusting for other predictors.

Self induced digital pressure associated with significant transient corneal distortions in a pediatric patient – A multi disciplinary approach

The present case study is of an 8-year old male who was found to have refractive instability due to corneal distortions that were associated with chronic habit of abnormal eye rubbing (CHAR). Psychiatric evaluation and treatment alleviated the CHAR and at the same time refraction stabilized and the cornea resumed a regular shape. Treatment of this case was made possible by close collaboration between the health care professionals caring for this child.

Evaluation of Visual Acuity, Pachymetry and Anterior-Surface Irregularity in Keratoconus and Crosslinking Intervention Follow-up in 737 Cases

Purpose

To investigate visual acuity, corneal pachymetry, and anterior-surface irregularity indices correlation with keratoconus severity in a very large pool of clinically-diagnosed untreated keratoconic eyes, and in keratoconic eyes subjected to crosslinking intervention.

Materials and methods

Total of 737 keratoconic (KCN) cases were evaluated. Group A was formed from 362 untreated keratoconic eyes, and group B from 375 keratoconic eyes subjected to partial normalization via topography-guided excimer laser ablation and high-fluence collagen crosslinking. A control group C of 145 healthy eyes was employed for comparison. We investigated distance visual acuity, uncorrected (UDVA), best-spectacle corrected (CDVA), and Scheimpflug-derived keratometry, pachymetry (central corneal thickness, CCT and thinnest, TCT), and two anterior-surface irregularity indices, the index of surface variance (ISV) and the index of height decentration (IHD). The correlations between these parameters vs topographic keratoconus classification (TKC) were investigated.

Results

Keratometry for group A was K1 (flat) 46.67 ± 3.80 D and K2 (steep) 50.76 ± 5.02 D; for group B K1 44.03 ± 3.64 D and K2 46.87 ± 4.61 D; for group C, K1 42.89 ± 1.45 D and K2 44.18 ± 1.88 D. Visual acuity for group A was UDVA 0.12 ± 0.18 and CDVA 0.59 ± 0.25 (decimal), for group B, 0.51 ± 0.28 and 0.77 ± 0.22, and for group C, 0.81 ± 0.31 and 0.87 ± 0.12.

Correlation between ISV and TKC (r2) was for group A 0.853, and for group-B 0.886. Correlation between IHD and TKC was for group A r2 = 0.731, and for group B 0.701. The ROC analysis ‘area under the curve’ was for CDVA 0.550, TCT 0.596, ISV 0.876 and IHD 0.887.

Conclusion

Our study indicates that the traditionally employed metrics of visual acuity and corneal thickness may not be robust indicators nor provide accurate assessment on either keratoconus severity or postoperative evaluation. Two anterior surface irregularity indices, derived by Scheimpflug-imaging, ISV and IHD, may be more sensitive and specific tools.

Précis

Visual acuity, Scheimpflug-derived pachymetry and anterior-surface irregularity correlation to keratoconus severity in untreated cases (A), treated with crosslinking (B), and in a control group (C) reveals that visual acuity and pachymetry do not correlate well with keratoconus severity.

How to cite this article

Kanellopoulos AJ, Moustou V, Asimellis G. Evaluation of Visual Acuity, Pachymetry and Anterior-Surface Irregularity in Keratoconus and Crosslinking Intervention Follow-up in 737 Cases. J Kerat Ect Cor Dis 2013;2(3):95-103.

Characteristics of 244 patients with keratoconus seen in an optometric contact lens practice

BACKGROUND

The purpose of this study was to describe the characteristics of keratoconic patients seen in a specialised contact lens practice from a general population with a high prevalence of the disease.

METHODS

Patients attending a contact lens practice for management of keratoconus were asked to complete a questionnaire. Data were collected on demographic characteristics, general health, family history, eye rubbing, allergy, asthma, eczema, education level, history of keratoplasty and smoking.

RESULTS

Two hundred and forty-four patients completed the questionnaire. There was a male bias (54.5 per cent). The majority of the patients (78.7 per cent) wore contact lenses, of whom 67.7 per cent wore hard, 13 per cent soft and 4.2 per cent scleral contact lenses. Some of the patients (21.3 per cent) had undergone corneal graft surgery. Eighteen per cent had an associated systemic disease, the most common of which was type 2 diabetes, although this disease was less prevalent, but not significantly, in the keratoconic sample than in the general population (p = 0.19). The prevalence of eye rubbing (65.6 per cent) was similar to other studies. Compared to the general population, asthma (13.2 per cent) was slightly, but not significantly, less prevalent (p = 0.17), eczema (6.6 per cent) was significantly less (p < 0.001) and allergy (34.4 per cent) was more prevalent (p < 0.001). A high proportion of patients reported a family history of the disease (27.9 per cent) and most were better educated than the general population.

CONCLUSION

The results of this survey concur with those of other studies with regard to most known characteristics of keratoconus; however, the proportion of asthma and eczema tended to be less than in other surveys and may be linked to the environmental influence of a hot and sunny country. The high prevalence of positive family history of the disease in this cohort suggests a genetic influence.