EFEI is one of the few practices in Florida to offer testing with Diopsys – a state of the art diagnostic machine – to help us evaluate and diagnose diseases of the retina and optic nerve by performing specialized VEP and ERG Testing.
THESE TESTS HAVE BEEN THE MAINSTAY OF NEUROLOGISTS, GLAUCOMA SPECIALISTS AND RETINA SPECIALISTS FOR OVER A DECADE… BUT UNTIL NOW, THEY HAVE BEEN DIFFICULT TO ADMINISTER AND TOOK HOURS TO PERFORM.
What is a VEP?
Visual evoked potential (VEP) tests the optic nerve. The optic nerve connects the eye to the brain. The retina of the eye is stimulated by light and converts this to an electrical signal that runs through the optic nerve and then to the back of the brain.
Many diseases affect the speed at which signals travel along the optic nerve to the brain. This may translate to decreased vision. With the VEP we can actually measure the speed of the signal as it goes from the eye to the brain.
THE DIOPSYS MACHINE STIMULATES THE EYE BY PROJECTING A BLACK AND WHITE CHECKERBOARD PATTERN ON THE RETINA AND THEN WITH SMALL ELECTRODES ON THE SKIN IT CAN DETECT THE ELECTRICAL IMPULSE.
THE TEST IS PAINLESS AND ALL THE PATIENT HAS TO DO IS LOOK AT A SCREEN.
We can then compare the transmission time between the two eyes, then to what is considered normal (around 100 milliseconds). The VEP test can actually give us information on the function of the nerve. This is useful in disease such as multiple sclerosis, ischemic optic neuropathy, glaucoma, and other disorders of the optic nerve. It can even be helpful in patients with closed head injuries or concussions. Often we will get a baseline to establish where the nerves are and then compare that at a later time. This way we can detect small changes in the nerve function much earlier then the patient will ever notice, and institute treatment that will prevent vision loss.
What is an ERG?
Electroretinography (ERG) is a way to test the function of the retinal cells. This includes the photoreceptors, inner retinal cells and gangional cells. Previously we were able to look at the structure of the retina with test like OCT, but the ERG has given us the ability to look at the function of the retina.
We can detect changes in the retina prior to them causing vision changes that the patient notices. This test can be used in patients with macular degeneration, diabetic retinopathy, and especially useful in patients on plaquinel.
THE ERG AND THE OCT ARE BECOMING THE NEW STANDARD TO TEST FOR EARLY CHANGES FROM PLAQUINEL TOXICITY.
THE TEST IS DONE WITH A SMALL ELECTRODE AROUND THE LOWER LID, AND THEN ON THE HEAD. THE PATIENT WILL LOOK AT A SCREEN, AND THE MACHINE WILL RECORD THE RESULTS.
Who Needs an ERG or VEP?
- Patients with glaucoma or glaucoma suspects
- Patients with a family history of glaucoma
- Multiple Sclerosis patients
- Patients on Plaquinel or other medications that can affect the optic nerve or retina
- Patients with unexplained vision loss
- Patients with macular degeneration
- Patients with closed head injuries