The detection of small simulated field defects using multifocal VEPs.

Area of Science:

• Ophthalmology
• Neuroscience
• Visual electrophysiology

Background:

• The multifocal visual-evoked potential (mfVEP) is a key tool for studying visual system diseases.
• The diagnostic sensitivity of mfVEP for detecting visual field defects remains undetermined.
• This study assesses mfVEP response variations when simulating field defects of varying sizes.

Purpose of the Study:

• To determine the minimum size of a simulated visual field defect detectable by mfVEP.
• To compare the sensitivity of mfVEP at different retinal eccentricities (10 and 16 degrees).
• To evaluate the impact of simulated field defects on mfVEP response density and latency.

Main Methods:

• Standard mfVEP dartboard stimuli were modified with opaque masks to simulate field defects (2, 3, 5, 7 degrees).
• Simulated defects were generated at 10 and 16 degrees of retinal eccentricity in 10 normal subjects.
• mfVEP response densities and latencies (N1, P1) were analyzed with and without simulated defects.

Main Results:

• A minimum simulated field defect size of 5 degrees was required to significantly reduce P1 and N1 response densities.
• N1 response density reduction was similar at both 10 and 16 degrees eccentricity.
• P1 response density reduction was more pronounced at 10 degrees than at 16 degrees eccentricity; latencies remained unchanged.

Conclusions:

• mfVEP is sensitive to simulated field defects of 5 degrees or larger.
• mfVEP demonstrates higher sensitivity in detecting simulated field defects at a 10-degree eccentricity compared to 16 degrees.
• mfVEP latency is not affected by small simulated field defects.