Author reply

We thank Dr. Killer for his interest in our study. We fully agree with him that (1) the assumption of a narrow orbital cerebrospinal fluid (CSF) space indicating a low intracranial CSF pressure is valid only if there is a free communication between the orbital CSF space and the intracranial CSF space; that (2) it has remained inconclusive whether the narrow optic nerve canal allows a free communication between the intracranial CSF space and the orbital CSF space in living human, even though studies on dogs and cadavers showed a linear relationship between the orbital CSF pressure and the intracranial pressure; and that (3) anatomic differences in the optic nerve canal may exist between East Asians and Europeans, which may explain marked differences between both ethnic groups in the prevalence of normal pressure glaucoma.