Abstract
Purpose: :
Papilledema in intracranial hypertension is a direct sign of elevated intracranial pressure. Since papilledema is a passive event not primarily affecting the visual tract resolution with restitution ad integrum is expected if intracranial pressure is rebalanced. Nevertheless, a regression of papilledema does not necessarily implicate a successful therapy but may also be caused by nerve fibre atrophy in long lasting optic disc edema. The purpose of the study was to investigate retinal nerve fiber swelling due to papilledema in the acute phase and possible axon loss after long lasting elevated intracranial pressure by Scanning Laser Polarimetry (SLP) and Optical Coherence Tomography (OCT).
Methods: :
32 patients with idiopathic intracranial hypertension according to the modified Dandy diagnostic criteria were investigated using SLP (GDx VCC) and OCT (Spectralis- or Stratus-OCT). Patients were divided into groups depending on the presence of a papilledema or the regression of the papilledema after initiation of medical therapy and mean nerve fiber thickness was evaluated as provided by the different devices.
Results: :
Mean retinal nerve fiber layer thickness showed no significant correlation between SLP and OCT in the acute phase of papilledema (r=0.219; p=0.255) but a good correlation in patients with regression of papilledema (r=0.776; p<0.001) after initiation of medical therapy. Bland-Altman analysis demonstrated a proportional deviation between the two methods in patients with papilledema and a systematic deviation for patients with regression of papilledema. 14 patients showed signs of nerve fiber loss in SLP but only 9 of 32 patients if measured by OCT.
Conclusions: :
SLP and OCT are useful to detect nerve fiber atrophy after regression of long lasting optic disc edema. OCT is valid to measure papilledema, whereas SLP does not show true nerve fiber swelling. Partial nerve fiber atrophy might be masked by coexisting papilledema when measured by OCT whereas SLP may show signs of early nerve fiber atrophy with coexisting papilledema.
Keywords: neuro-ophthalmology: optic nerve • imaging/image analysis: clinical • nerve fiber layer