A comparison between multifocal and conventional VEP latency changes secondary to glaucomatous damage

Area of Science:

• Ophthalmology
• Neuroscience
• Visual electrophysiology

Background:

• Glaucoma is a progressive optic neuropathy characterized by retinal ganglion cell loss.
• Visual evoked potentials (VEPs) are electrophysiological tests used to assess the visual pathway's function.
• Prolonged VEP latency has been suggested as an indicator of ganglion cell damage and a tool for monitoring neuroprotection in glaucoma.

Purpose of the Study:

• To compare the latency of conventional visual evoked potentials (cVEPs) and multifocal VEPs (mfVEPs) in the same patients.
• To evaluate the utility of VEPs in detecting abnormal ganglion cells and monitoring neuroprotection in glaucoma.

Main Methods:

• Seventy-five glaucomatous eyes, 75 eyes with suspected glaucoma, and 41 control eyes were tested.
• Achromatic automated perimetry, mfVEP, and cVEP tests were performed on all participants.
• mfVEP used a scaled dartboard with 60 sectors of pattern-reversing checkerboards; cVEP used pattern-reversing checkerboards of 15 or 60 minutes width.

Main Results:

• A minority of glaucomatous eyes exhibited VEP latencies outside the normal range, with little difference between cVEP and mfVEP results.
• In the glaucoma group, 12.3% (15 min cVEP), 8% (60 min cVEP), and 17.3% (mfVEP) of eyes exceeded the normal latency range.
• VEP latency showed no clear relationship with the visual field's mean deviation in glaucomatous eyes.

Conclusions:

• Contrary to previous findings, prolonged VEP delays were observed in only a small proportion of glaucoma patients.
• Delayed VEPs may not be a reliable indicator of damaged, as opposed to lost, retinal ganglion cells.
• The results suggest that either damaged ganglion cells are rare in these patients or VEPs are insensitive to such damage.