Histomorphometry of the optic disc in highly myopic eyes with absolute secondary angle closure glaucoma

Abstract

Aim: To evaluate histomorphometrically the optic nerve head in highly myopic eyes with absolute secondary angle closure glaucoma.

Methods: Optic disc sections of 16 highly myopic eyes with an axial length of more than 26 mm and of 19 eyes with an axial length of less than 26 mm were histomorphometrically evaluated. All eyes had been enucleated due to painful absolute secondary angle closure glaucoma.

Results: In the highly myopic eyes compared with the non-highly myopic eyes, mean optic disc diameter was significantly larger (mean 2.33 (SD 0.55) mm versus 1.77 (0.50) mm; p = 0.01), and the optic cup was significantly shallower (optic cup depth 0.34 (0.29) mm versus 0.63 (0.23) mm; p = 0.03). The peripapillary scleral ring was significantly broader (0.58 (0.65) mm versus 0.08 (0.06) mm; p = 0.001), and the beta zone (0.83 (0.74) mm versus 0.28 (0.25) mm; p = 0.006) of the parapapillary chorioretinal atrophy was significantly larger in the highly myopic eyes.

Conclusions: The results of the present study agree with biomorphometric data of the optic nerve head in highly myopic eyes with glaucoma. In the highly myopic group, a markedly enlarged peripapillary scleral ring characterised by absence of Bruch's membrane and choriocapillaris contributes in addition to alpha and beta zone to the parapapillary atrophy.

Figures

Figure 1

Microphotograph of an optic nerve head cross section of an eye with absolute glaucoma and normal axial length of 24 mm. Note the deep excavation. White arrows indicate the ends of Bruch's membrane. (Magnification as indicated in the right lower corner: black bar 100 µm; staining, periodic acid Schiff.)

Figure 2

Microphotograph of an optic nerve head cross section of a highly myopic eye with absolute glaucoma (axial length 30 mm). It shows a shallow excavation. White arrows indicate the retinochoroidal interface. (Magnification as indicated in the right lower corner: black bar 100 µm; staining, periodic acid Schiff.)

Figure 3

Microphotograph of the parapapillary region of an eye with absolute glaucoma and normal axial length (same eye as Fig 1). The black arrow points to the edge of Bruch's membrane and the white arrow indicates the beginning of the retinal pigment epithelium. The scleral ring is located left of the black arrow, zone B is between the two arrows and zone A is on the right of the white arrow. (ON= optic nerve, SA = subarachnoid space, V = vitreous; magnification as indicated in the right lower corner: black bar 50 µm; staining, periodic acid Schiff.)

Figure 4

Microphotograph of the parapapillary region of a highly myopic eye with absolute glaucoma (axial length 34 mm). The white arrows indicate the retinal remnants. Bruch's membrane and the retinal pigment epithelium are absent at this location. The white arrowhead points to the border of the optic nerve head. (ON = optic nerve, V = vitreous; magnification as indicated in the right lower corner: black bar 100 µm, staining, periodic acid Schiff.)