Age and sex related variations of adult human ocular volumes in the Sri Lankan population: an evaluation using magnetic resonance imaging

Abstract

IntroductionVariations in the human ocular volumes are related to ocular pathologies including congenital glaucoma, microphthalmus, buphthalmus, and macrophthalmus. As the currently published reference ocular volumes are prone to physiological and racial variations, population specific values may provide more precision in ophthalmological interventions. This study was conducted to assess the age and sex dependent differences in ocular volumes in Sri Lankan individuals using magnetic resonance imaging (MRI). MethodsThe study was undertaken using the brain MRI scans from 200 patients which were reported as normal. Study sample consisted of patients between 18 years and 90 years of age with 91 male subjects and 109 female subjects. Two independent observers measured ocular volumes using a software-based method and an MRI planimetry based method. Age and sex of the study participants were recorded for the further analysis. ResultsStatistically significant differences in both ocular volumes were found between males and females (p < 0.05) when using both volume analysis methods. The mean ± SD ocular volumes obtained as right software based volume, right MRI planimetry volume, left software based volume and left MRI planimetry volume were 6.8 ± 0.6, 6.0 ± 0.6, 6.6 ± 0.7 and 5.9 ± 0.6 cm3 in females and 6.9 ± 0.8, 6.3 ± 0.7, 6.9 ± 0.8 and 6.2 ± 0.7 cm3 in males. While software-based measurements show a significant linear correlation with age in both eyeball volumes, MRI planimetry measurement showed a significant linear correlation with age only in the left eyeball (p < 0.05). Weak negative correlations were found with age in right ocular volume in both MRI planimetry based (r = −0.121) and software based (r = -0.168) measurements and in left ocular volume in MRI planimetry based (r = −0.151) and software based (r = -0.179) measurements. Furthermore, ocular volumes obtained from the software-based method were significantly greater than the MRI planimetry based ocular volumes (p < 0.05) in both eyes, despite having a strong positive correlation. ConclusionThe mean ocular volumes obtained from this study revealed a significant variation between the right and left eyes as well as a sexual dimorphism. Moreover, since the two measurement methods show a significant difference, the choice of measurement method should depend on the required accuracy of the eye volume decided with respect to the clinical implication. Implications for practiceSince there are no reference values for Sri Lankan adult ocular volumes, this study may serve that purpose in the current population, while supporting ophthalmologists and radiologists to quantitatively evaluate ocular pathologies and to follow precise interventions.