ABSTRACT

The ability of the human eye to refract light rely on the equilibrium in overall size of the eye and the refractive components, namely, the cornea and crystalline lens. Increased intraocular pressure is suggested to impact stress on the scleral resulting in axial distension with scleral stretch implicated in the development of myopia.

The purpose of this study was to investigate the relationship between ocular biometrics, intraocular pressure, and refractive error in normal subjects. A total of one hundred and six subjects were used for this study which comprised 106 eyes of patients assessing eye care at the Eye Centre of ECWA Hospital Egbe, Kogi State. All eyes went through the same procedures with a complete ocular examination of slit lamp biomicroscopy, intraocular pressure measurement, objective and subjective refraction, calculation of spherical equivalent refraction, ocular biometry to obtained axial length, anterior chamber depth, lens thickness, and vitreous chamber depth of the globe as well as keratometry and pupil size measurement. Data obtained from the experiment was analyzed using statistical package for social sciences (SPSS) version 17.0.

The results showed the mean axial length, anterior chamber depth, lens thickness and vitreous chamber depth are 23.06±0.90mm; 2.93 ± 0.42 mm, 4.14 ± 0.50 mm and 15.97 ± 0.84 mm, respectively. The spherical equivalent refraction was inversely associated with axial length (r ₌ -0.40, p₌0.000), has a positive linear association with anterior chamber depth and lens thickness (r= 0.17, p₌0.0088; r₌0.28, p₌0.004), and has an inverse association with vitreous chamber depth and pupil size (r₌-0.44, p₌0.000; r₌-0.23, p₌0.016) respectively. It also shows no significant association between corneal curvature and intraocular pressure (r₌0.0064, p₌ 0.52; r₌0.12, p₌0.22) respectively. The association between biometric variables shows that axial length is positively associated with anterior chamber depth and vitreous chamber depth (r₌0.43, p= 0.000; r= 0.86, p= 0.038) respectively and inversely correlated with lens thickness (r= - 0.23, p= 0.038). Anterior chamber depth shows an inverse linear association with lens thickness (r= -0.61, p= 0.000) and a positive association with vitreous chamber depth (r= 0.32, p= 0.001); vitreous chamber depth shows a significant inverse relationship with lens thickness (r= -0.48, p =0.000). Corneal curvature shows a significant inverse relationship with axial length and vitreous chamber depth (r₌ -0.27, p₌0.006), the association between IOP, ACD and VCD were not significant (r₌0.028, p ₌ 0.77; r₌0.094, p= 0.34) respectively. Corneal diameter shows no significant association with other variables studied.

Conclusion: The relationship between refractive error and ocular biometric parameters varies from one parameter to another and the IOP was found to be independent of refractive error.

Key words: Ocular biometry, intraocular pressure, spherical lens equivalent and corneal diameter.