Abstract
Purpose: :
To study the anatomy of the glaucomatous optic nerve head in highly myopic eyes of Chinese.
Methods: :
The investigation included a study group of 32 human glaucomatous globes with an axial length >26.5 mm (highly myopic glaucoma group) which was compared with a non-highly myopic normal group of 40 globes enucleated due to malignant choroidal melanoma, and a non-highly myopic glaucomatous control group of 56 eyes enucleated due to painful absolute secondary angle-closure glaucoma. Anterior-posterior histologic sections through the pupil and the optic disc were morphometrically evaluated.
Results: :
The lamina cribrosa was significantly thinner in the highly myopic glaucoma group than in the non-highly myopic normal group (p<0.001) and in the non-highly myopic glaucoma group (p<0.001). In the highly myopic group, the lamina cribrosa thickness decreased significantly (P<0.001) with increasing axial length. Within the non-highly myopic normal group, the lamina cribrosa thickness was not significantly associated with axial length (P=0.54). In multivariate analysis, the peripapillary scleral thickness at the optic disc border and just outside of the optic nerve meninges decreased significantly with increasing axial length (P=0.05 and P=0.016, respectively). The percentage of the sclera passing into the optic nerve meninges did not vary significantly (p=0.17) between all three groups.
Conclusions: :
The lamina cribrosa is significantly thinner in highly myopic glaucomatous eyes than in non-highly myopic eyes so that the distance between the intraocular space and the cerebrospinal fluid space is reduced. In a parallel manner, the peripapillary scleral thickness decreases with increasing axial length in highly myopic eyes. These intrapapillary and peripapillary changes may be some of the reasons for an increased glaucoma susceptibility in highly myopic eyes. The lamina cribrosa thinning in the highly myopic eyes was significantly correlated with an increasing axial length beyond an axial length of 26.5 mm. It suggests that the myopic stretching of the lamina cribrosa starts at an axial length of about 26.5 mm. It additionally suggests that within the highly myopic group, the already increased glaucoma susceptibility may further increase with increasing axial length.
Keywords: anatomy • lamina cribrosa • myopia