Objective: To investigate the correlation between proptosis and changes of axial components in myopic eyes.
Methods: One hundred and eighty-nine myopic and emmetropic eyes were included. There are one hundred and eighty-three right eyes and six left eyes. Based on axial length (AL), subjects were divided into three groups: low-myopia & emmetropia group, moderate myopia group, high myopia group. Refraction of the eye (SE, spherical equivalent) was measured by retinoscopy examination under mydriasis. Proptosis was measured by Exophthalmometer (K-0161 Hertel-Type). Axial components including axial length and corneal curvature and were measured by partial coherence laser interferometry (IOL-master). The correlation in results among proptosis, axial components, and refraction was evaluated.
Results: The proptosis in high myopia group was bigger than in the other groups (P < 0.01). The proptosis in moderate myopia group was bigger than in low-myopia and emmetropia group (P < 0.01). The axial length was shorter than 25 mm in low-myopia and emmetropia group, from 25.00 to 27.00 mm in moderate myopia group and equal or longer than 27 mm in high myopia group. There was an increasing trend in proptosis [ranging from (14.66 +/- 1.94) mm, (16.16 +/- 1.40) mm to (18.30 +/- 1.63) mm] and axial length [ranging from (23.54 +/- 0.73) mm, (25.77 +/- 0.53) mm to (30.08 +/- 2.09) mm] among the three groups, the order of groups in the ranging was from low-myopia and emmetropia group, moderate myopia group to high myopia group. There was a highly significant correlation between proptosis and AL (R(2) = 0.990, F = 18 450.30, P < 0.01). Refraction results in low-myopia and emmetropia group, moderate myopia group and high myopia group were (-0.76 +/- 1.29) diopters (D), (-5.33 +/- 2.37) diopters (D) and (-15.92 +/- 5.12) diopters (D) respectively. There was a moderate correlation between proptosis and SE (R(2) = 0.500, F = 187.05, P < 0.01). There was a highly significant correlation between axial length and refraction (R(2) = 0.892, F = 1537.83, P < 0.01).
Conclusion: Myopic proptosis increases with the increasing AL and SE of the eye. The eyeball tends to expand backward and proptosis forward with the increasing AL and the proptosis forward appears to be more obvious.