Letter about the article entitled "Optic nerve sheath fenestration: A five year audit. Neuro-Ophthalmology 2005;29 : 173-177

Abstract

I read the article by Knapp and Sampath1 in a recent issue of this journal (Neuro-Ophthalmology 2005;29:173–177) with interest. The optic nerve sheath fenestration (ONSF) technique used by those authors is different in some respects from that used in previous studies. Optic nerve sheath fenestration is a surgical procedure performed in a critical and narrow area and in a limited time. Therefore, all the details related to the surgical technique are important. Two main surgical techniques have been described for decompression of the optic nerve. In the first technique, about 4 × 4 mm of the dura and arachnoid layers are excised and a meningeal window is created.2 The other technique comprises multiple longitudinal incisions with arachonidal dissection in the dura.3 In the second technique, it is assumed that multiple trabecular compartments of cerebrospinal fluid (CSF) are decompressed and that the orbital fat will not occlude the dural slits. The optic nerve can be reached by either medial or lateral orbitotomy. Knapp and Sampath made a fenestration of 0.5–1 mm in the nerve sheath through a medial conjunctival approach. Another specific aspect of their technique is that the bilateral surgery was performed simultanously in those patients with significant visual loss in each eye. Knapp and Sampath’s published study does not provide sufficient information about the details of their surgical technique.