Normal Tomographic Papillary and Macular Parameters in Young Cameroonians Aged 6 to 20 Years

Nanfack Ngoune C^1*, Akono Zoua ME¹, Nomo AF¹, Sohnagou Marie Josee¹, Ganone T¹, Nguepnang V¹, Mvilongo TC¹, Bilong Y¹, Kagmeni G¹, Noche N¹

¹Faculty of Medicine and Biomedicales Sciences, University of Yaounde 1, Botswana

*Correspondence author: Chantal Ngoune Nanfack, Faculty of Medicine and Biomedicales Sciences, University of Yaounde 1, Botswana; Email: cngoune2001@yahoo.fr

Citation: Nanfack NC, et al. Normal Tomographic Papillary and Macular Parameters in Young Cameroonians Aged 6 to 20 Years. J Ophthalmol Adv Res. 2025;6(3):1-11.

Copyright^© 2025 by Nanfack NC, et al. All rights reserved. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Table 1: Distribution of eyes based on refraction.

Table 2: Distribution of eyes according to the mean or median of optic disc parameters.

Table 3: Correlation between age and optic disc parameters.

Table 4: Variation of optic disc parameters according to sex.

Table 5: Variations in RNFL thickness according to sex.

Discussion

This analytical cross-sectional study successfully established normal tomographic parameters of the optic disc and macula in healthy young Cameroonians, utilizing the Topcon 3D-Maestro OCT. It is crucial to acknowledge that OCT measurements are inherently device-specific which consequently limits the direct generalization of these findings to other OCT platforms [3,4,6]. Furthermore, the hospital-based recruitment strategy may introduce a sampling bias, potentially impacting the representativeness of the broader general population. The primary strength of this research lies in its focus on a Black African population, a demographic notably underrepresented in existing scientific literature. In stark contrast to numerous studies predominantly centered on Caucasian populations, there is a distinct lack of normative data for African populations. Our comprehensive analysis, covering a broad spectrum of papillary and macular OCT parameters, offers a more complete characterization of the retinal and optic nerve head structures in young Cameroonians, differentiating it from studies that often focus on more limited aspects.

The median age of 13 years (interquartile range: 9-16 years) in our cohort is higher than that reported in studies conducted in France and Lebanon which typically included younger populations [1,10]. This age discrepancy underscores the critical influence of age in cross-study comparisons. The observed hyperopia prevalence of 43.3% and a median spherical equivalent of +0.5 diopters align consistently with previously published data [12,13]. These findings suggest that the refractive profile of our study population is comparable to that observed in other cohorts, thereby enhancing the generalizability of our results in this regard.

Optic Disc Tomographic Data

The mean optic disc area was 2.35±0.40 mm². This finding is consistent with Mays, et al., research in California, which reported an optic disc area of 2.46 mm² in a population of African American children [14]. This consistency suggests potential commonalities in optic disc size across various ethnic groups within the African diaspora. However, our results diverge from those of Elia, et al., in Spain, who found an optic disc area of 2.05±0.39 mm² [15]. This discrepancy could be attributed to the use of different OCT devices, but also significantly to racial influences. Previous research has proposed that individuals of African origin tend to possess larger optic discs than Caucasians and our study provides additional empirical evidence supporting this observation [4,15]. The absence of unusually large optic discs (area >4.09 mm²) in our cohort emphasizes the necessity of a thorough clinical evaluation for any notable optic disc excavation, as this could signal an underlying pathological condition.

Regarding the vertical cup-to-disc (C/D) ratio, the median was 0.60 (interquartile range: 0.50 – 0.66). This ratio is notably higher than values typically observed in Caucasian studies, which generally hover around 0.40 [4,15]. This suggests that individuals of Black ancestry may indeed exhibit a larger optic cup compared to Caucasians. This potential difference in C/D ratio must be meticulously considered during OCT interpretation and glaucoma diagnosis in individuals of African descent. Furthermore, the higher C/D ratio observed with OCT compared to clinical evaluation reflects inherent differences in measurement sites and methodologies; OCT provides a more objective and detailed assessment. Other optic nerve head parameters also displayed variations linked to geographical origin and race, yet these variations were not deemed pathological.

A statistically significant negative correlation was identified between the neuroretinal rim area and age (r=−0.20; p=0.001), indicating a physiological reduction in rim area with advancing age. Similarly, a statistically significant positive correlation was observed between age and the horizontal C/D ratio (r=0.13; p=0.018), suggesting a slight physiological increase in the horizontal C/D ratio with age. The optic disc area, neuroretinal rim area and vertical optic disc diameter were significantly larger in females, potentially attributable to hormonal factors or variations in overall ocular size. These specific observations contrast with Elia, et al., study which reported no significant differences in optic disc parameters related to age or sex [15].

The mean Retinal Nerve Fiber Layer (RNFL) thickness was 119.4±11 µm. This average is higher than values reported by Al-Haddad, et al., and Gire, et al., who, using a Cirrus OCT device, found values of 95.6±8.7 µm and 104.33±10.22 µm, respectively [1,10]. These disparities can be attributed to racial and device-related differences. As previously noted, different OCT devices can produce variable measurements due to differences in image acquisition technology and segmentation algorithms. Furthermore, individuals of Black ethnicity tend to have larger optic discs and, consequently, a thicker RNFL, as eyes with a larger optic disc physiologically possess a greater neuroretinal rim area and thus a higher quantity of retinal nerve fibers [16,17,18]. This relationship between optic disc size and RNFL thickness underscores the importance of considering optic disc size when interpreting RNFL thickness measurements. The mean RNFL thickness distribution by quadrant conformed to the normal “double-hump” pattern (respecting the ISNT rule) [3,4]. This characteristic distribution, with distinct peaks in the superior and inferior sectors, is crucial for distinguishing normal variations from pathological changes. No significant correlation was found between mean RNFL thickness and age, which is consistent with results from several studies conducted in young subjects [1,10,14,15]. This absence of correlation is explained by the fact that physiological axonal loss typically occurs later in life, generally peaking after the age of 50 [19]. However, mean RNFL thickness was significantly higher in the female population, which contrasts with some studies that have observed no influence of sex on RNFL thickness [10,15].

Macular Tomographic Data

The thickness of the macular Ganglion Cell Complex (GCC) was 111.9±6.7 µm. This is similar to Wolf, et al., findings in Sweden (107.1±6.5 µm) [20], but greater than those reported by Chaglasian, et al., in the United States (105.9±8.5 µm) and Vonor, et al., in Togo (105.0±7.1 µm) [6,21]. These differences may be explained by the inclusion of predominantly adult populations (mean ages: 37.7±15.2 years and 46.3±16.3 years, respectively) in these latter studies, unlike our study which focused on a younger cohort. No significant correlation was observed between age, sex and mean or sectoral GCC thickness. Our results corroborate those of Wolf, et al., in Sweden [20]. However, Vonor, et al., study, which included a wider age range (5 to 60 years), reported a weak correlation (r2=0.01; p=0.2), suggesting that our younger study population might not have been broad enough to detect this subtle association [21].

The Mean Macular Thickness (MMT) was 278±13.8 µm. These findings are consistent with those reported by Al-Haddad, et al., in Lebanon (279.6±12.5 µm) and Krumova, et al., in Bulgaria (286.70±9.82 µm) in pediatric populations [1,22]. This consistency across studies suggests a relatively stable macular thickness in children, thereby reinforcing the reliability of our results. In line with anatomical knowledge, mean foveal thickness (208.7±19.7 µm) was thinner than both mean parafoveal (298.2±15.9 µm) and perifoveal (274.1±12.8 µm) thicknesses, given that the fovea naturally lacks outer retinal layers [3]. Furthermore, we observed that the parafoveal region was thicker than the perifoveal region. These data align with those reported in most studies, reflecting the physiological variation in retinal thickness: it is thinnest at the foveola, increases at the clivus (parafoveal region) and then gradually decreases towards the retinal periphery [1,5,11,22-28].

Conclusion

This study significantly enriches the understanding of OCT parameters in young Cameroonians, underscoring the critical need for population-specific reference data. The observed differences highlight the paramount importance of considering both ethnic origin and the specific OCT technology used, as ethnicity can influence ocular structure and retinal parameters and various OCT devices can yield different measurements. Therefore, establishing normative values tailored to both the specific population and the OCT apparatus is essential for accurate clinical interpretation. Future research should encompass broader population-based studies and investigate the influence of additional factors, such as genetics and environmental elements. Furthermore, longitudinal follow-up studies are crucial to fully understand the long-term evolution of OCT parameters in Cameroonian children.

Conflict of Interest

The authors declare no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding Details

No author has a financial or proprietary interest in any material or method mentioned.

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