Visual electrical evoked potentials: evaluation of ocular injuries

Area of Science:

• Ophthalmology
• Neurophysiology
• Medical instrumentation

Background:

• Clinical neurophysiologists often evaluate patients with ocular injuries.
• Assessing retinal function in injured eyes can be challenging due to media opacities like blood.
• Conventional visual evoked potentials may be limited in these clinical scenarios.

Purpose of the Study:

• To describe a novel method for eliciting visual electrical evoked potentials (VEEPs) using transcorneal electrical stimulation.
• To compare VEEPs with conventional flash visual evoked potentials in healthy subjects and patients with severe ocular damage.
• To investigate the prognostic value of VEEPs in injured eyes.

Main Methods:

• Electrical pulse stimuli were delivered to the eye via a contact lens electrode.
• VEEPs were recorded from the cornea and contrasted with flash visual evoked potentials.
• The study included normal subjects and 17 patients with 19 severely injured eyes, primarily from trauma.

Main Results:

• The findings suggest that transcorneal electrical excitation targets retinal nerve cell layers, not photoreceptors.
• VEEP recordings successfully circumvented ocular media opacification by blood.
• Absent VEEP response was identified as an unfavorable prognostic sign.

Conclusions:

• VEEPs provide a viable method for evaluating retinal function in eyes with opacified media.
• While preserved VEEP response doesn't guarantee visual recovery, an absent response is a significant negative prognostic indicator.
• VEEPs may aid clinical decisions, including the consideration of enucleation.