Editor, The biomechanics of the optic nerve head is of particular importance in glaucomatous optic neuropathy. It depends on several parameters such the thickness of the lamina cribrosa and peripapillary sclera (Burgoyne et al. 2005). Previous studies have shown that glaucoma is associated with a thinning of the lamina cribrosa (Jonas et al. 2003). It was postulated that this lamina cribrosa thinning may be one of the reasons for an increased risk of further glaucoma progression in advanced stages of the disease (Gordon et al. 2002; Jonas et al. 2003). It was also demonstrated that the peripapillary sclera is thinner in highly myopic eyes compared to non-highly myopic eyes (Jonas et al. 2004). One inferred that this myopic thinning of the peripapillary sclera may be one of the reasons for increased glaucoma susceptibility in highly myopic eyes (Xu et al. 2007). It has remained unclear so far, whether besides high myopia, also glaucoma leads to a thinning of the peripapillary sclera. In that case, it will be an additional cause for the elevated risk of further glaucoma progression in eyes with advanced glaucoma (Gordon et al. 2002). We, therefore, performed the present study to address the question whether glaucomatous optic nerve atrophy is associated with a thinning of the peripapillary sclera, parallel to a thinning of the lamina cribrosa, in non-highly myopic eyes. The histomorphometrical study included eight eyes of eight patients who had been enucleated because of absolute secondary angle-closure glau-coma and 25 eyes of 25 patients who had been enucleated because of a malignant choroidal melanoma (control group). Using paraffin-imbedded histological sections running in anterior–posterior direction through the pupil and the optic nerve, we measured the thickness of the sclera just at the optic disc border inside of the optic nerve meninges, at the location just outside of the optic nerve meninges, and at distances of 0.2, 0.4 and 0.6 mm from the optic disc border (Fig. 1). The latter was defined by the end of Bruch’s membrane. Both groups did not vary significantly in age (p=0.98) and axial length [23.9 ± 1.9 mm (22.0–26.0 mm) versus 23.8 ± 0.9 mm (22–25 mm); p=0.89]. Eyes with an axial length of more than 26 mm were excluded. Histophotograph of an optic nerve head, showing the thickness measurement of the peripapillary sclera inside of the optic nerve meninges (yellow arrows) and just outside of the optic nerve meninges (black arrows). Between the glaucoma and the control group, the scleral thickness measurements did not vary significantly, neither inside of the optic nerve meninges (356 ± 56 versus 367 ± 64 μm; p =0.66) (Fig. 2), nor just outside of the optic nerve meninges (696 ± 93 versus 740 ± 117 μm; p=0.29), nor at distances of 0.2 mm (445 ± 65 versus 418 ± 100 μm; p=0.38), 0.4 mm (529 ± 62 versus 543 ± 142 μm; p = 0.71) and 0.6 mm from the optic disc border (601 ± 65 versus 598 ± 121 μm; p=0.92). Box plots showing the distribution of the thickness of the peripapillary sclera inside of the optic nerve meninges at the optic disc border in 10 eyes with absolute secondary angle-closure glaucoma and 26 non-glaucomatous eyes (control group). The results suggest that in adult non-highly myopic human eyes with far advanced glaucoma and presumably high intraocular pressure as typically found in absolute secondary angle-closure glaucoma, the peripapillary sclera did not get markedly thinner. This finding is in contrast to recent investigations in monkeys which developed a posterior scleral thinning in the course of experimental high-pressure glaucoma (Downs et al. 2001). Correspondingly, another study in adult monkeys with unilateral experimental glaucoma showed a lengthening of the glaucomatous eyes compared to the fellow control eyes (Hayreh et al. 1998). That is in contrast to non-highly myopic humans with glaucoma, in whom a lengthening or an enlargement of the optic disc was not described (Jonas et al. 1988). The latter finding correlates with the findings in the present study in which the scleral thickness in the peripapillary region of non-highly myopic eyes did not differ significantly between eyes with glaucoma and eyes without glaucoma. The finding of our study may have importance for the discussion of glaucomatous optic neuropathy in that in non-highly myopic human eyes, glaucoma-related thinning of the peripapillary sclera did not occur and thus may not contribute to the progression of the disease. The differences between humans and monkeys with respect to the peripapillary sclera in glaucoma may be taken into account if results of experimental glaucoma studies in monkeys are transferred to patients.