Abstract
Purpose: :
To examine changes in the multifocal electroretinogram (mfERG) in patients with optic nerve drusen. Optic nerve drusen are refractile bodies located on the anterior surface of the optic nerve. They commonly lead to visual field defects and, at times, transient visual loss in affected patients.
Methods: :
Subjects were identified with optic nerve drusen at a tertiary referral center and were treated according to the Declaration of Helsinki. Patients were dark adapted and received corneal anesthesia as well as pupillary dilitation. The mfERGs were recorded using a visual evoked response imaging system and a Burrian-Allen contact lens electrode (VERIS 5.3.2; EDI, San Mateo). A stimulus array of 103 hexagonal elements was delivered by an eye camera-display-refractor unit (EDI) driven at a 75-Hz frame rate. The implicit time and amplitude of local first-order mfERG responses were analyzed as previously described.
Results: :
On average, eyes with optic nerve drusen had responses which were reduced in amplitude compared to their clinically unaffected eye (or normal subject in the case of bilateral drusen). The reduction ranged from 14 - 58% in affected eyes and average 39.7%. The P1 latency was prolonged in eyes with optic nerve drusen but this difference was not found to be statistically significant in the initial analysis. The foveal response density was reduced an average of 75.6% (p= 0.06), the largest reduction of any area tested.
Conclusions: :
Patients with unilateral optic nerve drusen had decreased response amplitudes compared to their clinically unaffected eye. Since the foveal response was most affected by the drusen, it is possible that the midget ganglion cells are selectively targeted in the pathophysiology of this disease.
Keywords: electroretinography: clinical • electrophysiology: clinical • optic nerve