Download the Original Article Optical Illimination | M.D. News 2013

You may associate electrophysiology (EP) testing with cardiac medicine. However, at Chu Vision Institute, EP testing helps providers diagnose and evaluate eye conditions.

Imagine the body as a complex system of electrical circuits. In the visual system, retinal cells convert light energy into electricity, forming a circuit that continues through the optic nerve and into the visual cortex.

The electrical signals generated from light vary in amplitude and latency — that is, in strength and speed. When people suffer from eye diseases such as glaucoma or neurological diseases such as multiple sclerosis (MS), their eyes may respond less effectively to light, causing vision problems.

That’s where visual EP testing comes in. Using sensory pads affixed to a patient’s head, measurements of retinal and/or neurological response to a pattern of moving images are assessed. The latency and amplitude of the corresponding signal are measured to evaluate a condition or determine the effectiveness of a treatment.

Chu Vision provides this service in the office setting, allowing patients and referring physicians deeper information about many conditions, including:

  • Multiple sclerosis

  • Amblyopia

  • Stroke

  • TBI

Potential early diagnostic benefits may also be possible for patients with:

  • Macular degeneration

  • Glaucoma

  • Diabetic retinopathy

In addition to charting disease progress, clinicians can also draw on visual EP to evaluate the effectiveness of a treatment, such as patching.

Visual Pathway Testing

For a robust platform of vision testing, Chu Vision has acquired a testing system manufactured by Diopsys. The company’s NOVA-LX and NOVA-TR both test visually evoked potential (VEP), the neural response to light along the optic nerve and visual cortex. The NOVA-LX uses a fixed series of patterns to evaluate abnormalities in the visual pathways, while the NOVA-TR can be modified to test response to color reversals, horizontal and vertical patterns, and other variations in light.

Retinal Function Assessment

To assess retinal function, practitioners at Chu Vision use Diopsys NOVA-ERG, an electroretinography system. This technology focuses on the response of retinal cells to light, helping identify processes such as macular degeneration and glaucoma.

“Decreased amplitude and increased latency of response — these indicate problems,” says Dan Davis, OD, Vice President of Clinical Affairs at Chu Vision Institute. “When measuring responsiveness, we compare a patient’s eyes to each other, as well as to those of the baseline population. We have been using this technology for about six months at Chu Vision, and our patients like it very much. We have been able to obtain quantified information about MS, glaucoma, amblyopia, macular degeneration, diabetic retinopathy and certain medications that are toxic to the retina. This is a powerful tool to heighten our diagnostic ability.”

The Patient Experience

Although they use complex technology, visual EP tests require little patient interaction. Each test lasts about 15 minutes and requires neither anesthesia nor eye drops. Because the tests measure retinal and neural activity, patients do not even have to respond verbally. In fact, EP testing equipment can easily be moved to an exam room — a benefit for patients with limited mobility.

“We are excited to provide this technology to the community and are happy to act as a resource for any physician who wants VEP testing for their patients,” says Dr. Davis.

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