Purpose:
Pathologic myopia is the major cause of blindness worldwide. In addition to the increase of axial length, the eyes with pathologic myopia are considered to have deformity of eye shape. Although the elongation of the eye can be measured exactly, the deformity of the entire eye shape has been difficult to be evaluated. Recently, we have analyzed the 3D topographic images of eyes with pathologic myopia using high-resolution 3D magnetic resonance imaging (MRI). However, the analysis in our previous study was done based on the subjective judgment. So we have established the software to analyze objectively the deformity of highly myopic eyes using high-resolution 3D MRI. The aim of this study is to analyze the eye shape of pathologic myopia qualitatively and quantitatively using this software.
Methods:
234 eyes of 117 patients with bilateral high myopia (refractive error ≥-8.00 diopters (D) or axial length >26.5 mm) and 22 eyes of 22 patients with emmetropia were studied. Volume renderings of the images from the high-resolution 3D MRI data of the eye globe were analyzed quantitatively by the software which we established.
Results:
All of the eyes were successfully analyzed by the software. The shape of highly myopic eyes was symmetric in horizontal plane in 146 eyes (62.4%), and in 162 eyes (69.2%) in sagittal plane. The posterior shape of the eye was pointed in 45.7% of the eyes, and was dull in the remaining eyes. The shape of both eyes in each individual was identical in 61 patients (52.1%). The deformity was categorized and expressed by a number of three digits. In highly myopic eyes, the most prevalent type was the one whose posterior eye shape had dull angle and symmetric in both horizontal and sagittal planes. There was a significant negative correlation between the degree of pointedness of posterior eye shape and the patients’ age. Both visual field defects and myopic macular pathologies were significantly less frequently observed in symmetric eyes in horizontal planes and significantly more frequently observed in eyes whose posterior fundus is more pointed. In contrary, there was no deformity in any of the emmetropic eyes.
Conclusions:
The analysis of eye shape by this software has enabled more detailed analysis of eye shape of pathologic myopia and also is considered to be useful to analyze an association between eye shape and vision-threatening complications due to pathologic myopia.
Keywords: myopia • shape and contour • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)