Prevalence and topographical characteristics of keratoconus in patients with refractive errors in the Egyptian delta

Keratoconus characteristics and associations: A cross-sectional keratoconus study in western India (CKSWI)

PURPOSE

To study the clinical and tomographic characteristics and associations of keratoconus (KC) patients visiting a tertiary eye care hospital.

METHODS

This was a cross-sectional, observational study that included 242 newly diagnosed clinical KC patients. Detailed ocular and systemic history, visual complaints, habit of eye rubbing, best spectacle-corrected visual acuity (BSCVA), retinoscopy reflex, detailed slit-lamp examination and tomographic findings, and presence of any ocular and systemic associations were documented for the included patients. Severity of KC was further graded into stages 0, 1, 2, 3, and 4 according to the ABCD grading system.

RESULTS

The most common visual complaint was blurred vision (82.64%), followed by itching (48.76%), tearing (43.80%), and photophobia (41.32%). A total of 44.62% of patients had the habit of eye rubbing and 4.54% had a family history of KC. Most common clinical signs were scissor reflex (94.21%), Rizutti's sign (77.27%), corneal protrusion (69.83%), and Fleischer ring (67.35%). A total of 14.05% of patients had stage 0, 42.15% had stage 1, 19.83% had stage 2, 18.60% had stage 3, and 5.37% had stage 4 KC. Of these patients, 70.25% had a BSCVA visual acuity of ≥6/12 or better; 26.45% had a BSCVA of ≥6/60 to <6/12; and 3.30% had a BSCVA of <6/60. Ocular allergies, atopy, and asthma were found in 32.32%, 4.96%, and 2.48% cases, respectively.

CONCLUSION

This study gives an overview of the clinical findings of KC cases in western India. Our results suggest that use of retinoscopy should be promoted in early KC detection in primary eyecare screening programs.

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.

Correlation of Manifest Refraction and Simulated Keratometry to Tomography Characteristics in Patients With Keratoconus

OBJECTIVES

To report on baseline refractive and keratometric values and their correlation with tomographic characteristics of eyes with keratoconus (KC).

METHODS

Retrospective chart review of patients treated in a single-center cornea and refractive surgery practice. Baseline topographic measurements were reviewed for 1,012 keratoconic eyes of 586 patients between 2008 and 2018. The manifest refraction, thinnest pachymetry (P thin ), corneal astigmatism (K astig ), and the maximum (K max ), steep (K steep ), flat (K flat ), and mean (K mean ) keratometry were analyzed. The location of K max (x, y) was used to determine central (<1 mm), paracentral (1-3 mm), pericentral (3-5 mm), or peripheral (>5 mm) cone locations.

RESULTS

In the entire cohort, the mean manifest sphere was -2.2±4.4 diopters (D) and the cylinder was -3.2±2.3 D. In total, 48.6% of patients had against the rule (ATR) manifest astigmatism (M astig ). The average K astig was 3.8±2.7 D, and unlike the manifest axis, 50.2% of patients had with the rule (WTR) K astig . Patients with a K max less than 50 D had an M astig of -1.9±1.6 D, 45.9% of which was ATR M astig . With respect to baseline tomography measurements, K max , K steep , K flat , and K mean were 58.0±9.4, 50.6±6.5, 46.8±5.9, and 48.6±6.1 D, respectively. There was a weak correlation between K max and simulated keratometry (K steep , K flat , and K mean ) for patients with a K max less than 60 D.

CONCLUSIONS

Simulated keratometry is poorly correlated with KC severity until the disease is more severe. M astig ≥2 D and ATR M astig were correlated with KC at all levels of severity. M astig ≥2 D and ATR M astig may serve as a simple, inexpensive, and widely available indicator for topographic analysis to identify possible KC and suggest further workup; however, further prospective studies are needed to confirm its utility.

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.

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.

Prevalence of Subclinical Keratoconus in Children with Astigmatism in Iraq

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

Prevalence and incidence of keratoconus in Norway: a nationwide register study

PURPOSE

To estimate the national prevalence and incidence of keratoconus in Norway.

METHODS

In this epidemiologic study, data were obtained from the Norwegian Patient Registry, which provides information from all publicly funded specialist care in Norway. Prevalence of keratoconus was estimated from the total number of patients registered with this diagnosis and incidence from the annual frequency of first-time registrations of patients up to 40 years of age in the period 2010-2018. Data on age and gender of the keratoconus patients were also gathered.

RESULTS

A total of 9832 keratoconus patients were registered. The estimated prevalence in the general population was 192.1 per 100 000 (95% confidence interval (CI): 188.3-195.9), and the estimated annual incidence was 19.8 per 100 000 (95% CI: 18.1-21.5). There was a predominance of males (73%), and mean age for all patients was 37.5 years at first registration in this period.

CONCLUSION

This study reports the frequency of keratoconus from a national patient register during a time period with available modern diagnostic tools. The estimated prevalence and incidence were higher than most previous estimates and show that keratoconus is not a rare condition. As screening was not part of the study, the true prevalence in the general population may be even higher.

Keratoconus in Africa: A systematic review and meta-analysis

PURPOSE

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

METHOD

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

RESULTS

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

CONCLUSION

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

Prevalence of Subclinical Keratoconus Among Pediatric Egyptian Population with Astigmatism

Purpose

To report the prevalence of subclinical keratoconus (KC), and KC suspects, in pediatric Egyptian population with astigmatic error ≥2 diopters (D), with the use of CSO Sirius tomographer.

Methods

A cross-sectional study that included all the children aged 6–18 years with an astigmatic error of ≥2 D who attended the pediatric ophthalmology clinic for routine checkups during the period between March 2017 and December 2017 was done. All subjects underwent comprehensive ophthalmic examination, and corneal imaging using CSO Sirius instrument, a pentacam with Scheimpflug technology.

Results

There were 547 subjects enrolled in our study. Mean age was 11.34 ± 3.03 (range 6–18) years. There were 278 subjects (50.8%) between 6 and 12 years, and 269 subjects (49.2%) between 12 and 18 years. Males represented 48.4% and females represented 51.6% of patients. Among all the subjects, there were 26 (4.8%) KC patients, 24 (4.4%) KC suspects, and 497 (90.9%) were normal.

Conclusion

Prevalence of subclinical KC among pediatric age group with astigmatism is relatively high, hence the importance of corneal tomography screening of children with astigmatic error ≥2 D.