Keratoconus in Africa: A systematic review and meta-analysis

Keratoconus Profile in the Elderly Population: Prevalence, Keratoconus Indices, and Patterns of Keratoconus

PURPOSE

To assess the prevalence and associated characteristics of keratoconus (KCN) among individuals aged 60 years and older.

METHODS

In this study, total of 160 clusters and 20 strata were identified in Tehran, Iran through a multistage cluster sampling technique. Participants aged 60 years and older were included in the study. Corneal imaging used the Pentacam AXL. The diagnosis of KCN in this study was determined based on the measurements obtained from axial topography, pachymetry, and the elevation data from the Pentacam's refractive 4-maps.

RESULTS

The prevalence of KCN was determined to be 5.36% [95% confidence interval (CI), 4.52-6.2], with rates of 5.04% (95% CI, 3.88-6.2) in males and 5.68% (95% CI, 4.47-6.9) in females. The prevalence of KCN increased from 4.6% (95% CI, 3.29-5.92) among individuals aged 60 to 64 years to 6.92% (95% CI, 3.18-10.67) in those aged 80 years and older. A multiple regression analysis indicated that advancing age (odds ratio = 1.03; P < 0.001) and illiteracy (odds ratio = 1.65; P < 0.001) were significant factors associated with KCN in the elderly population. Besides, the predominant curvature pattern observed in KCN was the asymmetric bowtie with inferior steepening (18.91%), whereas the symmetric bowtie was the least common (0.29%).

CONCLUSIONS

The prevalence of KCN is notably high among the elderly population and tends to rise with advancing age. Findings from the current study underscore the critical role of corneal topography and tomography in guiding clinical decisions for older patients, particularly in the context of intraocular lens power calculations.

Normative corneal biometric parameters in sub-Saharan African populations: A systematic review and meta-analysis

BACKGROUND

Despite the importance of corneal biometric parameters in ophthalmology, there is limited comprehensive data on these measurements in Sub-Saharan African (SSA) populations. This study systematically reviewed the evidence on corneal biometric parameters of Sub-Saharan African populations, focusing on their variability, influencing factors, and implications for clinical practice and public health interventions.

METHODS

A systematic review and meta-analysis were conducted following PRISMA guidelines. Eligible studies published between January 2003 and December 2023 were identified through comprehensive searches in PubMed, Scopus, and Web of Science, with a specific focus on African populations. Inclusion criteria comprised non-interventional studies reporting central corneal thickness (CCT), corneal curvature, radius of curvature, or horizontal corneal diameter (HCD) of eyes of continental Africans. Data were synthesized using random-effects meta-analyses, with heterogeneity assessed using the I2 statistic. Subgroup analyses examined variations by geographic region, measurement instrument, and sex.

RESULTS

Twenty-eight studies with a total of 14,009 participants were included. The pooled mean CCT was 553.35 µm (95 % CI: 548.52-558.18 µm), with regional variations ranging from 555.66 µm in West Africa to 510.17 µm in Southern Africa. Males exhibited slightly higher CCT values compared to females (539.11 µm vs. 533.78 µm). Additional parameters assessed included mean corneal curvature (43.07 D), radius of curvature (7.70 mm), and HCD (11.59 mm). Variability in the measurements was attributed to demographic, geographic, and methodological factors.

CONCLUSIONS

Corneal biometric parameters exhibit substantial regional and demographic variability in SSA. These findings underscore the importance of population-specific data in enhancing diagnostic precision and guiding the development of regionally tailored clinical protocols. Further research is needed to address current knowledge gaps and improve eye care outcomes across the African continent.

FUNDING

This research received no specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Referral Pattern and Comanagement of Patients With Keratoconus in West Africa: A Survey-Based Study of Optometrists in Ghana and Nigeria

OBJECTIVES

To investigate the referral and management patterns of patients with keratoconus among primary eye care practitioners in Ghana and Nigeria.

METHODS

A questionnaire adapted from previous studies was modified and created using Google Forms. The online survey was distributed to prospective participants using e-mails and other social media platforms. Data were analyzed using the Statistical Product and Service Solutions software (version 25.0; IBM Corp, Armonk, NY; Released 2017).

RESULTS

One hundred and sixty-nine optometrists responded to the survey (61.54% from Nigeria and 38.46% from Ghana). Most (88.6%) practiced without corneal topographers. Most respondents (77.7%, n=136) reported not fitting rigid gas-permeable (RGP) contact lenses in a year and 68% were willing to refer for contact lens fitting to another practitioner. The major barriers to RGP fitting were lack of experience (44.4%, n=72), cost to practice (15.4%, n=25), and other reasons (12.4%), whereas 27.8% (n=45) preferred not to answer. Seventy-six percent of respondents (n=133) were willing to fit RGPs if the respondents received the training to do so. About half of the respondents (53.8%) reported progression of cornea signs as the reason for referral to an ophthalmologist. Half of the respondents (n=51.4%) did not have a cornea surgeon in the area the respondents practiced, and 76.3% reported not comanaging patients at all with ophthalmologists.

CONCLUSION

This study highlights the current standard of care of patients with keratoconus in West Africa. The findings from this study suggest that clinical guidelines and further training of eye care practitioners in West Africa are needed to better manage patients with keratoconus.

Prevalence and demographic profile of keratoconus among high school students in Kenya

PURPOSE

To determine the prevalence and demographic profile of keratoconus (KC) among high school students in Nairobi County, Kenya.

METHODS

In this population-based, prospective, cross-sectional study, multistage cluster sampling was used to select the participants. All students underwent visual acuity measurement, auto-refraction, retinoscopy and corneal topography. Students with a scissors reflex on retinoscopy or corneal topography patterns suspicious of KC were referred for corneal tomography.

RESULTS

A total of 3051 students from 29 schools, with a mean age of 17.4 ± 1.6 years (range: 13-25 years) were screened. The prevalence of KC was 1.7% (n = 51) (95% CI, 1.2-2.2) and of KC suspects was 3.8% (n = 117) (95% CI, 3.2-4.6). There were no significant associations between the prevalence of KC and gender, age or ethnicity (all p > 0.05). In the KC group, 88.2% (n = 45) were unaware of their condition, 52.9% (n = 27) were treated for allergic conjunctivitis, 45.1% (n = 23) required spectacles, 11.8% (n = 6) were recommended contact lenses in at least one eye and 49.0% (n = 25) were recommended corneal cross-linking.

CONCLUSIONS

Among adolescents, the results of this study indicate a higher prevalence of KC compared to that reported in South Korea, Norway, Brazil and Caucasians in New Zealand, but less than that reported in some countries in the Middle East. Given the high prevalence revealed in this study, a national school screening program and clinical guidelines for screening, diagnosis and management of KC is recommended.

Factors associated with keratoconus in Israel-A cross-sectional population-based study

PURPOSE

To identify potential factors associated with keratoconus.

METHODS

This cross-sectional study included data from Israel's largest healthcare provider for the years 2005-2020. Keratoconus patients and age-matched controls were identified. Demographic factors and comorbid conditions, including smoking, diabetes mellitus, asthma, myalgia, mental retardation, Down syndrome, atopic dermatitis and allergy/allergic rhinitis, were compared between the two cohorts. The independent risk factors associated with keratoconus were determined using a multivariable conditional logistic regression model.

RESULTS

Overall, 145 508 subjects were reviewed of which 13 228 were keratoconus patients. A ten-fold group (n = 132 280) of age-matched control subjects served as controls for comparisons. In multivariable analysis, several factors were found to be significantly associated with keratoconus. Male gender (OR = 1.27, p < 0.001), Arab ethnicity (OR = 1.50, p < 0.001), diabetes (OR = 1.19, p < 0.001), asthma (OR = 1.50, p < 0.001), myalgia (OR = 1.09, p = 0.02), mental retardation (OR = 2.63, p < 0.001), atopic dermatitis (OR = 1.35, p < 0.001) and allergic rhinitis (OR = 1.21, p < 0.001) were significantly associated with keratoconus. Smoking was significantly protective of keratoconus (OR = 0.66, p < 0.001).

CONCLUSIONS

This population-based study reports male gender, Arab ethnicity, diabetes, asthma, myalgia, mental retardation/Down syndrome, atopic dermatitis and allergic rhinitis as factors associated with keratoconus while smoking demonstrates a protective effect. The results of this study could guide enhanced screening strategies and early interventions, particularly for high-risk groups.

Effects and safety of combined corneal collagen crosslinking and intrastromal corneal ring segment treatment in patients with keratoconus: a retrospective study

PURPOSE

To evaluate the safety and efficacy of different time-point combinations of intrastromal corneal ring segment (ICRS) implantation using femtosecond technology) and corneal collagen crosslinking (CXL) for the treatment of moderate-to-severe keratoconus (KCC).

METHODS

This study included 69 eyes of 69 patients with keratoconus who underwent ICRS and CXL treatment at an Eye Hospital between March 2020 and March 2023. The patients were divided into two groups: Group 1 (n = 33 eyes of 33 patients), which received ICRS and CXL treatment in one session, and Group 2 (n = 36 eyes of 36 patients), which included treatment with ICRS for at least 6 months following CXL application. Preoperative and postoperative evaluations included visual acuity, autorefractometer refraction, corneal tomographic measurements using the Sirius (CSO) Scheimpflug camera and the TONOREF™ III device, and documentation of observed complications. Uncorrected visual acuity (UCVA) and best-corrected spectacle visual acuity (BCVA) were measured in each eye individually, and visual acuity was assessed using the logarithm of the minimum angle of resolution (logMAR).

RESULTS

In Group 1, mean UCVA improved from 0.81 ± 0.34 to 0.45 ± 0.25 (p < 0.01), and mean BCVA improved from 0.76 ± 0.35 to 0.38 ± 0.20 (p < 0.01). In Group 2, mean UCVA improved from 0.71 ± 0.32 to 0.43 ± 0.30 (p < 0.01), and mean BCVA improved from 0.65 ± 0.25 to 0.31 ± 0.23 (p < 0.01). Both groups showed significant reductions in manifest spherical and cylindrical refraction (p < 0.01). Group 1 exhibited greater reductions in maximum keratometry (Kmax), flat keratometry (K1), steep keratometry (K2) (p < 0.05), and astigmatic aberration compared with group 2 (p < 0.01). The use of simultaneous or separate CXL and ICRS does not significantly increase the incidence of complications.

CONCLUSIONS

Both combined and separate CXL and ICRS treatments resulted in significant improvement in UCVA and BCVA and reduced manifest refraction. Although improvements were observed in groups 1 and 2 in terms of K1, K2, and Kmax at 6 months, the improvements were more pronounced in Group 1. These results highlight the potential benefits of simultaneous ICRS + CXL treatment and underscore the importance of optimising the timing of CXL treatment to achieve the best visual outcomes.

Awareness of Keratoconus Among the Population of Taif City, Saudi Arabia: A Cross-Sectional Study

BACKGROUND

Keratoconus (KC) is a prevalent corneal condition in Saudi Arabia, with studies suggesting variable prevalence rates across regions, highlighting a considerable public health issue. Despite its prevalence, public awareness of the condition remains low. This study aims to evaluate the level of awareness of keratoconus among the population in Taif City, Saudi Arabia.

METHODS

A community-based cross-sectional study was conducted in Taif City from May to July 2024. An online questionnaire, adapted from a validated Arabic version, was distributed via social media to adults aged 18 years and older. The survey included questions about demographics, medical history, and keratoconus awareness. Data were analyzed using descriptive and inferential statistics. Awareness levels were categorized as good or poor based on participants' responses, and the chi-squared test or Fisher's exact test was used to compare categorical variables.

RESULTS

The study included 499 participants, with 282 (56.5%) aged 18-25 years and 383 (76.8%) females. Nearly half of the participants, 248 (49.7%), had a history of allergies, and 294 (58.9%) reported having an eye condition. While 286 (57.3%) had heard of keratoconus, only 83 (16.6%) correctly identified it as corneal thinning. Additionally, 263 (52.7%) believed frequent eye rubbing could lead to keratoconus, though 186 (37.3%) were unsure. Overall, 414 (82.9%) participants demonstrated poor awareness of keratoconus. Participants with a refractive error, a family history of KC, or prior knowledge of the disease were significantly more likely to have good awareness (p < 0.05).

CONCLUSION

The study reveals a low level of awareness about keratoconus among the population in Taif, despite its significant association with eye rubbing and potential visual impairment. The findings highlight the need for public health interventions and educational campaigns to raise awareness and promote early detection of keratoconus.

Screening Preadolescents for Keratoconus Risk Factors in a Low-Resource Setting

BACKGROUND

Diagnosis of keratoconus (KC) involves the identification of corneal signs, refraction, and corneal imaging. The prevalence of KC ranges between 0.4 per 100,000 and 4,790, depending on geographical location and ethnicity. Diagnosis of KC should occur early for appropriate management with relatively affordable, accessible options to prevent visual impairment in low-income settings.

METHOD

Written consent and assent were obtained from subjects before a questionnaire was administered to collate demographics, general and ocular history of subjects, and keratoconus risk factors. A novel scoring system was applied to identify subjects at a higher risk of developing KC and document KC risk factors prevalent in Harare using an informed risk score calculation.

RESULTS

Thousand one hundred fifty-three subjects aged between 6 and 12 years were seen. The prevalence of KC was found to be 626/100,000 in primary school children resident in Harare. Reduced visual acuity, vernal keratoconjunctivitis, itchy eyes, eye rubbing, and atopy are the most prevalent KC risk factors identified in this community. Informed risk score calculation proved valuable in the screening for KC.

CONCLUSION

The prevalence of KC in primary school children in Harare is 626/100,000, which is relatively high. School-aged children stand to benefit from the early screening for KC based on evidence-based practices in the absence of advanced clinical instrumentation.

Estimated prevalence of keratoconus in the largest metropolitan area of Italy

PURPOSE

To estimate the prevalence of keratoconus in a population of subjects undergoing first eye examination in an eye clinic in Italy.

METHODS

A single-center, cross-sectional, study was conducted involving patients who underwent first eye examination at an eye clinic in Rome between September 2021 and June 2022. The prevalence of keratoconus was determined by Placido-disk corneal topography using the maximum keratometry (Kmax) value and the Cone Magnitude and Location Index (CLMI) for keratoconus screening. Subjective analysis was performed by two experienced corneal specialists, who classified the outcome into two groups: normal and keratoconus. Risk factors, including family history of keratoconus, allergy or atopy, thyroid disease, eye rubbing habit and gender were also examined.

RESULTS

A total of 512 subjects between 7 and 81 years old were evaluated. The inter-observer agreement to classify subjects in normal or keratoconus group was excellent (k = 1.0); the estimated prevalence in the specific population was 2.1%. Presence of positive family history (9% of keratoconus vs 5% normal), concomitant allergy or atopy (27% vs 9%) and eye rubbing habit (18% vs 4%) were associated with a higher risk of disease.

CONCLUSION

This study reported a high estimated prevalence of keratoconus in a metropolitan area of Italy, as found in recent studies in the Mediterranean and Middle East countries. Screening for keratoconus is highly recommendable and easily feasible with corneal topography under expert supervision and may be indicated primarily in young population to improve early detection and prompt therapeutic management for halting disease progression.

Dramatic Reduction in Corneal Transplants for Keratoconus 15 Years After the Introduction of Corneal Collagen Crosslinking

PURPOSE

The aim of this study was to investigate the effect of the implementation of corneal collagen crosslinking (CXL) on the frequency of corneal transplants among patients with keratoconus (KC) in the same region.

METHODS

Before the introduction of CXL in 2007, 55 primary corneal transplants had been conducted in patients with KC (2005 and 2006) at the Department of Ophthalmology, Oslo University Hospital, Norway. We collected data from our corneal transplant registry for 2021 and 2022. The primary outcome was the number of corneal transplants performed in patients with KC. Age, sex, visual acuity (logarithm of the minimal angle of resolution), KC stage according to the Amsler-Krumeich classification system, and steepest keratometry reading (maximum keratometry, Pentacam, HR) were recorded. Furthermore, we registered the annual number of CXL treatments conducted from 2007 to 2022.

RESULTS

A total of 352 corneal transplants were performed in 2021 and 2022. Among them, 11 (3.1%) were transplants for patients with KC. All included patients were male; further, 90.1% and 9.1% of the patients were graded stages 4 and 3, respectively. The mean maximum keratometry was 79.0 diopter (range 61.0-109). The mean best-corrected visual acuity (logarithm of the minimal angle of resolution) was 1.3 (range 0.2-3.0). In 2021 to 2022, 431 CXL treatments were performed.

CONCLUSIONS

There was a significant decrease in the number of corneal transplants performed in patients with KC 15 years after the introduction of CXL. This indicates that the availability of CXL treatment over many years may considerably reduce the need for keratoplasties in this group of patients.

The candidate proteins associated with keratoconus: A meta-analysis and bioinformatic analysis

PURPOSE

Keratoconus (KC) is a multifactorial disorder. This study aimed to conduct a systematic meta-analysis to exclusively explore the candidate proteins associated with KC pathogenesis.

METHODS

Relevant literature published in the last ten years in Pubmed, Web of Science, Cochrane, and Embase databases were searched. Protein expression data were presented as the standard mean difference (SMD) and 95% confidence intervals (CI). The meta-analysis is registered on PROSPERO, registration number CRD42022332442 and was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement (PRISMA). GO and KEGG enrichment analysis were performed, as well as the miRNAs and chemicals targeting the candidate proteins were predicted. PPI was analyzed to screen the hub proteins, and their expression was verified by RT-qPCR.

RESULTS

A total of 21 studies were included in the meta-analysis, involving 346 normal eyes and 493 KC eyes. 18 deregulated proteins with significant SMD values were subjected to further analysis. In which, 7 proteins were up-regulated in KC compared with normal controls, including IL6 (SMD 1.54, 95%CI [0.85, 2.24]), IL1B (SMD 2.07, 95%CI [0.98, 3.16]), TNF (SMD 2.1, 95%CI [0.24, 3.96]), and MMP9 (SMD 1.96, 95%CI [0.68, 3.24]). While 11 proteins were down-regulated in KC including LOX (SMD 2.54, 95%CI [-4.51, -0.57]). GO and KEGG analysis showed that the deregulated proteins were involved in inflammation, extracellular matrix (ECM) remodeling, and apoptosis. MMP9, IL6, LOX, TNF, and IL1B were regarded as hub proteins according to the PPI analysis, and their transcription changes in stromal fibroblasts of KC were consistent with the results of the meta-analysis. Moreover, 10 miRNAs and two natural polyphenols interacting with hub proteins were identified.

CONCLUSION

This study obtained 18 candidate proteins and demonstrated altered cytokine profiles, ECM remodeling, and apoptosis in KC patients through meta-analysis and bioinformatic analysis. It will provide biomarkers for further understanding of KC pathogenesis, and potential therapeutic targets for the drug treatment of KC.

Barriers to the Diagnosis and Management of Keratoconus Among Optometrists in Kenya

Background

Early diagnosis and management of keratoconus (KC) are important for limiting visual complications of the disease. This study aimed to explore the perspectives of optometrists on the barriers to effective diagnosis and management of KC in Kenya.

Methods

An online questionnaire was distributed to optometrists in Kenya to collect data on barriers to the diagnosis and management of KC.

Results

The majority (60.9%) of optometrists were confident in retinoscopy and subjective refraction. Fewer were confident in the use of keratometers (46.4%) and corneal topographers (24.9%) and in the fitting of rigid gas permeable (RGP) contact lenses (25.0%). The most commonly reported barriers to improving their knowledge and skills were, limited continuous professional development opportunities (87.4%), high costs of conferences (86.1%) and the lack of diagnostic tools (79.5%). Impediments cited to diagnosing and managing KC effectively were a lack of national guidelines (64.9%), patient education material (71.5%), equipment (58.9%) and RGP supply (68.2%) and cost (67.5%). Most commonly reported barriers related to patients were compliance (91.4%), affordability (90.7%), RGP discomfort (89.4%), willingness to pay (88.1%) and the lack of patient education about KC (87.4%).

Conclusion

This study showed that the lack of national guidelines, essential equipment and adequate practitioner knowledge and skills were barriers to KC diagnosis and management. Regulation of optometric education and clinical practice, development of national guidelines for diagnosis and management of KC, up-skilling of practitioners and cost-effective solutions for equipment procurement and maintenance may improve both access to, and quality of, care to patients with KC.

Experiences of keratoconus patients attending public eye care facilities in South Africa

BACKGROUND

Keratoconus (KC) is a progressive condition that usually affects young persons between their first and fourth decades. Myopia and irregular astigmatism are the common presentations which are proceeded by corneal steepening and thinning. Keratoconus is a progressive ectasia of the cornea that presents bilaterally, although often asymmetrical.

AIM

To explore the experiences of KC patients attending public eye care facilities in Capricorn District of Limpopo province.

SETTING

Capricorn District, Limpopo province, South Africa.

METHODS

Descriptive qualitative phenomenology approach was used in the study to explore the lived experiences of patients diagnosed with KC, attending public eye care facilities. Purposive sampling was used to select 16 patients who were diagnosed with KC and referred for contact lens fitting. Data were collected through face-to-face, one-on-one interviews.

RESULTS

Patients reported to have developed gradual vision loss which worsened when they grew older. There was lack of knowledge of KC amongst patients and this was exacerbated by limited health literacy and vocabulary barriers. Patients had difficulty performing daily activities where some had dropped out of school while others worked at a slower pace and reduced working distances.

CONCLUSION

Patients with KC received inadequate information on their condition due to limited health literacy and vocabulary barriers. Programmes to promote practitioner and patient education are required to improve the perceived service level provided to KC patients.Contribution: The findings of this study will assist to improve the experiences of KC patients on perceived service quality received from public facilities.

A double-crosslinked nanocellulose-reinforced dexamethasone-loaded collagen hydrogel for corneal application and sustained anti-inflammatory activity

In cases of blinding disease or trauma, hydrogels have been proposed as scaffolds for corneal regeneration and vehicles for ocular drug delivery. Restoration of corneal transparency, augmenting a thin cornea and postoperative drug delivery are particularly challenging in resource-limited regions where drug availability and patient compliance may be suboptimal. Here, we report a bioengineered hydrogel based on porcine skin collagen as an alternative to human donor corneal tissue for applications where long-term stability of the hydrogel is required. The hydrogel is reinforced with cellulose nanofibers extracted from the Ciona intestinalis sea invertebrate followed by double chemical and photochemical crosslinking. The hydrogel is additionally loaded with dexamethasone to provide sustained anti-inflammatory activity. The reinforced double-crosslinked hydrogel after drug loading maintained high optical transparency with significantly improved mechanical characteristics compared to non-reinforced hydrogels, while supporting a gradual sustained drug release for 60 days in vitro. Dexamethasone, after exposure to crosslinking and sterilization procedures used in hydrogel production, inhibited tube formation and cell migration of TNFα-stimulated vascular endothelial cells. The drug-loaded hydrogels suppressed key pro-inflammatory cytokines CCL2 and CXCL5 in TNFα-stimulated human corneal epithelial cells. Eight weeks after intra-stromal implantation in the cornea of 12 New-Zealand white rabbits subjected to an inflammatory suture stimulus, the dexamethasone-releasing hydrogels suppressed TNFα, MMP-9, and leukocyte and fibroblast cell invasion, resulting in reduced corneal haze, sustained corneal thickness and stromal morphology, and reduced overall vessel invasion. This collagen-nanocellulose double-crosslinked hydrogel can be implanted to treat corneal stromal disease while suppressing inflammation and maintaining transparency after corneal transplantation. STATEMENT OF SIGNIFICANCE: To treat blinding diseases, hydrogel scaffolds have been proposed to facilitate corneal restoration and ocular drug delivery. Here, we improve on a clinically tested collagen-based scaffold to improve mechanical robustness and enzymatic resistance by incorporating sustainably sourced nanocellulose and dual chemical-photochemical crosslinking to reinforce the scaffold, while simultaneously achieving sustained release of an incorporated anti-inflammatory drug, dexamethasone. Evaluated in the context of a corneal disease model with inflammation, the drug-releasing nanocellulose-reinforced collagen scaffold maintained the cornea's transparency and resisted degradation while suppressing inflammation postoperatively. This biomaterial could therefore potentially be applied in a wider range of sight-threatening diseases, overcoming suboptimal administration of postoperative medications to maintain hydrogel integrity and good vision.

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.

Clinical-epidemiological characteristics of keratoconus in Asturias

INTRODUCTION

Keratoconus is the most frequent corneal ectasia and second most common cause of keratoplasty worldwide. The clinical and epidemiological characteristics of keratoconus have rarely been studied in Spain, and to date, no study has been done in Asturias.

MATERIAL AND METHODS

A cross-sectional study was conducted to analyze all cases of keratoconus diagnosed in the first consultations of the Cornea and Surface section of the Hospital Universitario Central de Asturias (Oviedo) and Hospital Universitario de Cabueñes (Gijón) between 2017 and 2020. Demographic data, visual acuity and corneal topography were collected.

RESULTS

A total of 112 patients (42.0% women and 58.0% men) were included. The mean age was 36.84 ± 15.59, with 39.3% being older than 40 years. 31.8%, 28.0%, 15.0%, and 25.2% were in stages I, II, III and IV, Amsler-Krumeich scale, respectively. Corneal segments were implanted in 7.5% of patients, cross-linking was performed in 4.7%, and keratoplasty was performed in 13.2%.

CONCLUSION

Approximately 40% of keratoconus cases are detected at advanced stages and another 40% are detected at an age over 40 years. 13% of these patients require keratoplasty, which is why it is frequently performed in our setting. Therefore, early diagnosis before irreversible visual loss is necessary.

Diagnosis and management of keratoconus by eye care practitioners in Kenya

BACKGROUND

To explore current eye care practice in keratoconus diagnosis and management in Kenya.

METHODS

An online questionnaire was distributed to ophthalmic clinical officers (OCO) and optometrists.

RESULTS

A total of 203 responses were received from 52 OCOs and 151 optometrists with a response rate of 24.4% and 53.5% respectively. The majority reported having access to retinoscopes (88.5%; p = 0.48) and slit lamps (76.7; p = 0.14). Few practitioners had access to a corneal topographer (13.5%; p = 0.08) and rigid contact lens (CL) fitting sets (OCOs 5.8%, optometrists 33.8%; p < 0.01). One-third did not feel that retinoscopy (38.7%; p = 0.21), slit lamp findings (30.3%; p = 0.10) and corneal topography (36.6%; p = 0.39) are important investigations in keratoconus diagnosis. Corneal topography was not recommended in two-thirds of patients (59.0%; p = 0.33) with vernal keratoconjunctivitis (VKC). The majority counselled against eye rubbing in mild (73.6%; p = 0.90) VKC, 52.9% in moderate (p = 0.40) and 43.6% in severe (p = 0.24) cases. The majority prescribed spectacles in mild (90.2%; p = 0.95), 29% (p = 0.97) in moderate and 1.9% (p = 0.05) in severe cases. When the binocular best corrected visual acuity (BCVA) with spectacles was ≤ 6/18, 76.9% of OCOs and 58.9% of optometrists referred for CLs (p = 0.02). When binocular BCVA with CLs dropped to ≤ 6/18, 83.7% (p = 0.18) referred to the ophthalmologist for surgical intervention. Few OCOs fitted rigid CLs (15.4% OCOs, 51.0% optometrists; p = 0.01), majority referred to optometrists (82.7% OCOs, 43.7% optometrists; p < 0.01). Progression was monitored in 70.1% (p = 0.11) of mild, 50.9% (p = 0.54) moderate and 25.3% (p = 0.31) advanced cases. Few OCOs (15.4%) performed corneal cross-linking (CXL). A few respondents (5.4%; p = 0.13) did not know when to refer keratoconus patients for CXL. Co-management with ophthalmologists was reported by 58.0% (p = 0.06) of respondents.

CONCLUSION

The results of this study highlight the need to map services for keratoconus patients, review current curricula and continuous education priorities for mid-level ophthalmic workers, develop guidelines for the diagnosis and management of keratoconus and improve interdisciplinary collaboration.

Strabismus and amblyopia in Africa - a systematic review and meta-analysis

The objective of this review was to estimate the prevalence of strabismus and amblyopia in Africa. A systematic online literature search was conducted for articles on strabismus and amblyopia in Africa. Meta-analysis was performed, using the Freeman-Tukey double arcsine transformation, to estimate the prevalence of strabismus and amblyopia in Africa. Subgroup analyses were conducted according to age, gender, study year, and type of amblyopia. Meta-regression was used to evaluate the influence of predetermined factors on the prevalence of amblyopia. 8 (1 population-based & 7 school-based) and 21 (3 population-based & 18 school-based) studies on strabismus and amblyopia with sample sizes of 22,355 and 46,841, respectively, were included in the review. Overall prevalence of strabismus in Africa was estimated to be 0.8% (95% CI: 0.4% - 1.4%); exotropia was 0.2% (95% CI: 0.1% - 0.5%) and esotropia was 0.5% (95% CI: 0.1% - 1.2%). Overall prevalence of amblyopia was estimated to be 0.6% (95% CI: 0.3% - 0.9%); refractive and strabismic amblyopia were 1.1% (95% CI: 0.2% - 2.5%) and 0.4% (95% CI: 0.2% - 0.6%), respectively. Prevalence estimate of amblyopia in males was 1.8% (95% CI: 0.7% - 3.3%) and in females was 1.3% (95% CI: 0.4% - 2.6%). There was a significant association between the prevalence of amblyopia and the type of amblyopia (p = .007) and the study year (p = .006). Although there appears to be a relatively low prevalence of strabismus and amblyopia in Africa, there is a dearth of well-designed population-based studies on strabismus and amblyopia in Africa, resulting in the lack of epidemiological information on strabismus and amblyopia within the general African population. Information about the prevalence of strabismus and amblyopia across Africa can inform policy making and design and implementation of public health intervention program.

Risk Profile of Keratoconus among Secondary School Students in the West Region of Cameroon

This study determined the risk factors of keratoconus (KC) among secondary school students in the West Region of Cameroon. A stratified, random sampling technique was used to select the 3015 secondary school students, 8 years and older, within the West Region of Cameroon. Selected school students completed the validated Keratoconus Risk Investigative Survey (KRIS) and a structured demographic questionnaire to determine the risk profile of KC. Descriptive analysis, logistic regression and p-values were used to provide an overview of the demographic findings and the risk factors of KC. Estimates were made as the proportion of affected school students and presented with a 95% confidence interval (CI). Multivariate logistic regression analysis was performed to explore the association between KC and the independent predictors that were found significant in the univariate analysis. The ages of the majority (93.2%) of students ranged from eight years to 18 years (mean = 13.18 ± years) and were mostly female (59.7%). Gender (OR 2.024, p < 0.001), eye rubbing (OR 3.615, p < 0.001), exposure to sunlight (OR 2.735, p < 0.001), blood relations with KC (OR 41.819, p < 0.001) and allergic experience (OR 1.070, p < 0.001) were considered. Eye rubbing was the most significant risk factor of keratoconus followed by refractive error, allergic experiences and sunlight exposure. These findings support the evidence that the etiology of KC is multifactorial, with eye rubbing being the most significant factor in this cohort. There is a need to address eye rubbing among students to minimize the risk of KC. Furthermore, 34.46% of students in Cameroon were at risk of developing KC. Hence the risk profile is that one engages in eye rubbing, has a family member with KC, spends more than eight hours per week in the sun and is prone to allergies. It will therefore be prudent for these risk factors for keratoconus to be included in the school health education programs.

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.

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.

Childhood Vision Impairment and Refractive Error in Zimbabwe: A Hospital-based Retrospective Study

Background

The objective of this study was to determine the causes and distribution of vision impairment and refractive error among children in Zimbabwe.

Methods

A hospital-based retrospective cross-sectional study was conducted among children (3–16) who attended the Eye Institute, Harare, Zimbabwe, from January 2010 to December 2020. Patients' records were collated, and variables such as visual acuity, ocular morbidities, and vision impairment were analysed.

Results

During this time, 1038 children with mean age of 10.63 ± 3.54 years visited the facility. The majority of them were males (53.2%). Prior to treatment, 9.9% of the children had vision impairment which reduced to 3.5% after intervention. Uncorrected refractive error accounted for the majority of vision impairment (67.0%), followed by keratoconus (7.8%), corneal opacity/ulceration (6.8%), and amblyopia (6.8%), among other conditions. Astigmatism (60.6%) was the most prevalent type of refractive error followed by myopia (37.5%).

Conclusion

The prevalence of childhood vision impairment is higher than that found in similar hospital-based studies conducted in Africa. The most common reason for childhood vision impairment was uncorrected refractive error.

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.

Evaluating the association between MPDZ-NF1B rs1324183 and keratoconus in an independent northwestern Chinese population

Background

Keratoconus (KC) is a complex, non-inflammatory corneal degenerative disease. Although numerous studies have analyzed the correlation of SNP rs1324183, which located in MPDZ-NF1B gene, and KC in different populations, only few findings were repeated. In this study, to evaluate the association between rs1324183 and KC in a new independent Chinese population, we performed a replication study of the significantly associated rs1324183.

Methods

In total of 114 unrelated KC patients and 88 unrelated controls were recruited from Ningxia, China. We detected the genotypes and alleles of rs1324183 using PCR technology and Sanger sequencing and also analyzed the association between this locus and KC, its clinical parameters by statistical methods.

Results

The frequency of genotype AA (11, 9.6%) and genotypes containing allele A (47, 41.2%) of rs1324183 in KC were both higher than those of the control group. And genotype AA of rs1324183 conferred a higher risk of KC (OR > 1). Moreover, corneal parameter Belin/Ambrósio enhanced ectasia display final D value (BAD-D) had significant correlation (p = 0.002) with AA genotype of rs1324183 in KC.

Conclusions

Our replication study indicates that the results of rs1324183 associated with KC in our population is robust and further better illustrates the significance of BAD-D as a diagnostic indicator for KC. rs1324183 should be considered as the first genetic mark of KC risk in its future diagnosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02359-1.

Ectasia After Corneal Refractive Surgery: A Systematic Review

INTRODUCTION

The incidence of ectasia following refractive surgery is unclear. This review sought to determine the worldwide rates of ectasia after photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) based on reports in the literature.

METHODS

A systematic review was conducted according to modified Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Publications were identified by a search of eight electronic databases for relevant terms between 1984 and 2021. Patient characteristics and preoperative values including manifest refractive spherical refractive equivalent (MRSE), central corneal thickness (CCT), anterior keratometry, postoperative residual stromal bed (RSB), and percent tissue altered (PTA) were summarized. In addition, annual rates of each refractive surgery were determined, and incidence of post-refractive ectasia for each type was calculated using the number of ectatic eyes identified in the literature.

RESULTS

In total, 57 eyes (70 eyes including those with preoperative risk factors for ectasia) were identified to have post-PRK ectasia, while 1453 eyes (1681 eyes including risk factors) had post-LASIK ectasia, and 11 eyes (19 eyes including risk factors) had post-SMILE ectasia. Cases of refractive surgery performed annually were estimated as 283,920 for PRK, 1,608,880 for LASIK, and 96,750 for SMILE. Reported post-refractive ectasia in eyes without preoperative identifiable risk factors occurred with the following incidences: 20 per 100,000 eyes in PRK, 90 per 100,000 eyes in LASIK, and 11 per 100,000 eyes in SMILE. The rate of ectasia in LASIK was found to be 4.5 times higher than that of PRK.

CONCLUSION

Post-refractive ectasia occurs at lower rates in eyes undergoing PRK than LASIK. Although SMILE appears to have the lowest rate of ectasia, the number of cases already reported since its recent approval suggests that post-SMILE ectasia may become a concern. Considering that keratoconus is a spectrum of disease, pre-existing keratoconus may play a larger role in postoperative ectasia than previously accounted for in the literature.