The Electroretinogram (ERG) (CPT 95930)
This is an objective test somewhat similar to the VEP but test RETINA function not OPTIC NERVE function. A contact lens is placed in each eye and the response to a flash of light is recorded as the electrical activity of the retina (recorded by electrodes placed in the face/head). This is a test not use in patients known to have MS but in patients whose visual loss’ cause is not known to see if the visual loss is of retinal origin.
Results with Retinitis Pigmentosa
Optic Nerve/Retinal Topography
This uses a scanning laser to measure nerve fiber layer thickness, as a way to gauge nerve fiber function, particularly in diseases affecting the optic nerve. Decrease in the thickness of the nerve fiber layer is found in patients with MS and can be used to determine progression over time of the disease contributing to loss of nerve fibers. The machines are called OCT, GDX, HRT among others.
The Explanation: RNFL Loss