轴性高度近视眼直肌PULLEY功能位置的动态磁共振成像研究

目的用MRI研究轴性高度近视眼4条直肌pulley的功能位置,探讨轴性高度近视继发性眼球运动障碍的病因。方法轴性高度近视12例(22眼)根据眼屈光度、眼轴长度以及有无眼球运动受限分为A、B两组。A组无眼球运动受限;B组有眼球运动受限。应用动态MRI技术,获取眼球原在位及上转、下转、内转、外转位时的冠状位MRI图象。应用计算机图像处理软件测量各层面MRI图像眼球垂直方向转动时水平直肌、眼球水平方向转动时垂直直肌的横截面质心,根据其坐标值建立直线回归方程,统计求得眼球垂直转动时内、外直肌径路及眼球水平转动时上、下直肌径路直线回归曲线斜率变化最大的一点(直肌pulley的位点),将A组、B组、正常对照组进行比较。结果A组与正常对照组4条直肌pulley的位点比较无显著差异(P>0.05);B组与正常对照组内直肌、上直肌、下直肌pulley的位点比较无显著性差异(P>0.05);B组外直肌pulley的位点较正常对照组向颞下移位(P<0.01);A组与B组内直肌、上直肌、下直肌pulley的位点比较无显著性差异(P>0.05);B组较A组外直肌pulley位点向颞下移位(P<0.05)。结论外直肌pulley的位点向颞下移位可能是引起轴性高度近视眼继发性眼球运动障碍的主要病因之一。

The location of rectus pulley in high myopia by dynamic MRI

Objective To study the location of rectus pulleys in high myopia by dynamic MRI and the etiopathogenisis of dyskinetic ocular movement of axiality high myopia. Methods The patients depend on refractive diopter, axis of eye ball and dysfunction of eye movements were divided into two groups: A group had no dysfunction of eye movements; B group had limitation of movement. Multiple contiguous quasi-coronal MRI images perpendicular to the orbital axis were acquired at primary gaze, supraduction, infraduction, abduction, and adduction by dynamic MRI. The area centroids of vertical rectus at secondary horizontal gaze and horizontal recti at secondary vertical gaze were then determined by image software. Rectus paths were defined as the connection of the area centroids and plotted in a normalized oculocentric coordinate system. Inflection of each rectus path was then determined objectively using linear regression on rectus mean area centroid coordinates. The point of the biggest changes of slope rate in linear regression equation was defined as the functional locations of rectus pulley. And the result was compared with the normal control. Results In group A, all rectus Pulley function locations have no statistically significant difference compared with normal control (P>0.05). In group B, the function point of MR, SR, and IR rectus Pulley have no statistically significant difference compared with normal control (P>0.05). The LR rectus Pulley function points of group B compared with normal control have statistically significant difference(P<0.01). The LR rectus Pulley function points significant inferior dislocation in temporal site. Between group A and group B, except the LR rectus pulley function location is significant inferior dislocation in temporal site (P<0.05),the others rector pulley function locations have no statistically significant difference(P>0.05). Conclusions The inferior dislocation in temporal site of LR rectus pulley point maybe the main cause of dysfunction of eye movements in high myopia.