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Flash Visual Evoked Potential (F-VEP)

Eye Care estimated about CNY 350-700

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Description

An electrophysiological test measuring cortical electrical responses to brief, non-patterned light flashes; used to assess optic nerve and visual pathway integrity, especially when pattern VEP is unobtainable.

Main Uses

Objective assessment of visual pathway integrity from retina to occipital cortex; diagnosis and monitoring of optic neuritis and multiple sclerosis; evaluation of unexplained visual loss (e.g., functional vs. organic); pre- and post-surgical assessment in optic pathway surgeries; detection of subclinical optic nerve dysfunction; differentiation of anterior (retrobulbar) vs. posterior (cortical) lesions; pediatric vision assessment when behavioral testing is unreliable.

Normal Range

Latency of the P100 wave: 95–115 ms (varies by age, stimulus size, contrast, and refractive correction); Amplitude: 5–20 µV (peak-to-trough); Interocular latency difference: <10 ms; Interocular amplitude ratio: >0.7. Values are highly dependent on testing parameters (e.g., checkerboard size 60′ or 15′, contrast ≥80%, luminance ~50 cd/m², monocular stimulation with refractive correction).

Low Values - Possible Causes

Optic nerve demyelination (e.g., multiple sclerosis), optic atrophy (e.g., glaucoma, ischemic optic neuropathy), severe amblyopia, advanced retinal ganglion cell loss (e.g., end-stage optic neuropathies), uncorrected high refractive error or media opacity (e.g., cataract, vitreous hemorrhage) during testing.

High Values - Possible Causes

Rarely clinically meaningful as 'high' amplitude is uncommon; potential contributors include technical artifacts (e.g., excessive electrode impedance, muscle artifact), young age (<10 years) with enhanced neural synchrony, hypermyelination (very rare), or paradoxical amplitude elevation in early inflammatory optic neuritis (transient, not diagnostic); prolonged latency (not amplitude) is far more clinically relevant than elevated amplitude.

flash visual evoked potential optic pathway assessment neuro-ophthalmology test

estimated about CNY 350-700