| Objective: To examine histomorphometrically the parapapillary region in highly myopic eyes.
Methods: We examined a highly myopic glaucomatous group (36 human globes; axial length >26.5 mm) and a non-highly myopic group (28 globes). Using light microscopy, pupil-optic nerve sections were assessed.
Results: In all highly myopic eyes (n=15) with a distance of >0.5 mm between optic nerve border and beginning of Bruch membrane, the parapapillary region consisted of an elongated parapapillary scleral flange associated with a scleral flange thinning and a retrobulbar cerebrospinal fluid space extended into the retro-parapapillary region. The parapapillary retina was composed of retinal nerve fiber layer (or its remnants) only, without elements of any other retinal layer, without underlying Bruch membrane or choroid. These histological features were not detected in any of the non-highly myopic eyes.
Conclusions: Since parapapillary scleral thickness influences the lamina cribrosa biomechanics, the findings may partially explain the increased glaucoma susceptibility in highly myopic eyes. The implications of a missing of Bruch membrane and choroid in the highly myopic parapapillary region, and the implications of the retrobulbar parapapillary extension of the cerebrospinal spinal fluid space for the pathophysiology of the optic nerve head have to be elucidated. | 
