Abstract
Purpose: :
To determine how compression of the optic nerve distal to the eye affects the structure and function of the retinal ganglion cell within the eye in patients with compressive optic neuropathy
Methods: :
36 patients with compressive optic neuropathy were tested by PERG (LACE electronica), visual evoked potentials (VEP) and had retinal nerve fiber layer thickness assessed by optical coherence tomography (OCT). These were compared with 20 normal subjects tested with PERG and simultaneous VEP.
Results: :
51 eyes had normal RNFL thickness (normal OCT in 70%); 34% had abnormal PERG phase but normal amplitude, 4% had abnormal amplitude but normal phase, and 12% had both abnormal phase and amplitude. 21 eyes had significant thinning of the RNFL (abnormal OCT in 30%); 19% had abnormal PERG phase but normal amplitude, 14% had abnormal amplitude but normal phase, and no eyes had both abnormal amplitude and phase. PERG phase was abnormally shortened (phase lead) in eyes with central visual field loss and was delayed (phase lag) in eyes with diffuse or peripheral field loss.
Conclusions: :
Compression of the optic nerve distal to the eye can cause abnormalities in either amplitude or phase of the PERG before axon loss occurs. Abnormalities in phase may consist of either phase lag or lead and may be influenced by the corresponding visual field location of axons which are impaired.
Keywords: neuro-ophthalmology: optic nerve • electroretinography: clinical • nerve fiber layer