Study on normal ophthalmic tissues among ocular volume and extraocular muscles structure measurement by HR-MRI

Abstract

Objective: To measure the ocular volume and extraocular muscles of healthy people using the high-resolution magnetic resonance imaging (HR-MRI) technology, to provide parameters support for eye research, teaching and diagnosis. 

Methods: The study collected 100 cases of normal subjects (200 eyes) from November 2012 to December 2013, including 50 males and 50 females, accepted line HR-orbital MRI, and image processing software was applied to morphology and statistical analysis. The extraocular muscles, muscle belly level horizontal diameter and maximum diameter vertical diameter were measured.

Results: The volume of the vitreous cavity (4.51 ± 0.26) cm³ had no significant difference with the anatomic normal value (p = .148); The volumes of the ocular globe, the anterior chamber and the lens cavity were (5.05 ± 0.21) cm³, (0.24 ± 0.26) cm³, (0.23 ± 0.14) cm³, with no statistic differences compared with those of the anatomic normal values. The extraocular muscles of normal Chinese were symmetrical on the two sides. The relationships of the short diameters of extraocular muscles in the maximum planes were: inferior rectus muscle (IR) > medial rectus muscle (MR) > superior rectus (SR) > lateral rectus muscle (LR). Those of the long diameters of extraocular muscles were: LR > MR > SR > IR.

Conclusions: MRI can be used for measuring ocular volume and sizes of extraocular muscles. Compared with the anatomic normal value, the sizes of extraocular muscles can also be assessed by the symmetry on the two sides and by observing the usual rule of extraocular muscles.