Assessment of ocular axial length as a factor in refractive errors (myopia and hyperopia)

Refractive errors account for a large proportion of patients presenting with visual impairment. In the developed nations, ocular axial length has been found to be the strongest determinant of refractive errors, however, there is paucity of knowledge on this issue in the West African sub-region. This study was undertaken at the University of Benin Teaching Hospital to determine the relationship between axial length and the form of refractive errors seen. Study Design: A prospective study of the ultrasonic measurement of the axial length of the eye in 100 myopic and 100 hyperopic adult patients was carried out over a 6-month period. All the patients had refraction and were confirmed to have either of refractive errors by the ophthalmologist. Result: Ocular axial lengths were consistently higher in the myopic patients than in the control group (P < 0.001) while axial lengths were consistently lower in the hyperopic patients in comparison to the control group (P < 0.001). There was no significant difference between the axial length of the right and left eye in any one individual whether myopic or hyperopic. Myopia was found to be common in the younger age group in contrast with hyperopia, which was mainly seen in the middle aged and elderly. In addition, individuals with higher body mass indices were found to have shorter axial lengths than those with lower body mass indices, therefore the heavier patients were mainly hyperopic while the lighter ones were myopic. Conclusion: This study showed a strong association between myopia and longer axial length and this is synonymous with large eyeballs. On the contrary, a shorter axial length was found in the hyperopic group indicating a smaller eyeball size.