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.

Interocular Symmetry and Repeatability of Central Corneal Thickness and Corneal Endothelial Cell Morphology and Density in Healthy Eyes of Congolese

PURPOSE

To determine the limits of normal interocular symmetry and the repeatability of central corneal thickness (CCT) and endothelial cell morphology and density.

METHODS

Two hundred and seventy-eight subjects (age: 10.9-80.7 years) with healthy eyes were studied. CCT as well as endothelial cell morphology and density were measured by non-contact specular microscopy. Three measurements were obtained per eye per participant. Upper and lower tolerance limits of normal interocular symmetry were defined as the 2.5th and 97.5th percentiles of the interocular differences in CCT, endothelial cell density (CECD), coefficient of variation (CoV), hexagonality, and cell size. Repeatability was determined using the intraclass coefficient correlation (ICC), the coefficient of variation (CV), and the test-retest variability standard deviation (TRTSD).

RESULTS

The mean interocular differences were -1.05 ± 17.5 µm (p = .32) for CCT and 0.5 ± 90.8 cells/mm² (p = .76) for CECD. The 2.5th and 97.5th percentiles of the interocular differences were -13.9 and 15.4 µm for CCT and -177.4 cells/mm² to 182.0 cells/mm² for CECD. Only interocular difference in CoV correlated weakly with age (r = -0.22, P < .001). ICCs were 0.93 (95% CI: 0.89-0.96, P < .001) for CCT and 0.95 (0.94-0.96, P < .001) for CECD. CV and TRTSD were 1.2% ± 5.3% and 4.4 ± 3.4 µm for CCT and 2.4% ± 3.9% and 17.7 ± 7.7 cells/mm² for CECD, respectively.

CONCLUSIONS

CCT and CECD showed good repeatability and interocular symmetry in normal Congolese subjects. Absolute interocular differences in CCT and CECD exceeding 15.5 µm and 182 cells/mm², respectively, should be considered suspicious and investigated. When comparing two intrasession measurements from the same eye, a difference of approximately 4.5 µm in CCT and 18 cells/mm² or greater may be considered statistically significant.