Eagleview Eye Clinic

Tag electroretinography

P50 and N95

P50 and N95 are key waves in pattern ERG (PERG), reflecting retinal ganglion cell (RGC) function:

  • P50: Early positive wave, mainly from RGCs and inner retinal layers. Reduced amplitude or delayed timing suggests ganglion cell dysfunction, common in early glaucoma or optic neuropathies.
  • N95: Later negative wave, more specific to optic nerve health. A drop in N95 amplitude often signals optic nerve damage or axonal loss.

Both waves together help gauge severity and progression of optic nerve diseases. For example, in glaucoma, P50 might reduce first, then N95 drops as damage worsens.

PATTERN ERG

Pattern ERG (PERG) measures electrical activity from retinal ganglion cells in response to a reversing checkerboard pattern. It’s great for spotting optic nerve issues like glaucoma and macular problems.

  • How it’s done: Electrodes on the eye, patient looks at a screen with a checkerboard pattern that flips contrast.
  • What it records: P50 wave (early positive) reflects ganglion cell function; N95 wave (negative) relates to optic nerve health.
  • Key use: Detects ganglion cell loss early, even before visual field defects show up.
  • Difference from full-field ERG: PERG focuses on central retina and optic nerve, not whole retinal response.
ELECTRORETINOGRAPHY

Electroretinography (ERG) is a test that measures the electrical response of the retina’s light-sensitive cells (rods and cones) to light stimuli. It helps diagnose retinal diseases like retinitis pigmentosa, macular degeneration, and Leber congenital amaurosis.

  • How it works: Electrodes placed on the cornea or skin around the eye record electrical activity while the eye is exposed to flashes of light.
  • What it shows: Waves (a-waves, b-waves) reflecting function of photoreceptors and inner retinal layers.
  • Types: Full-field ERG (tests whole retina), multifocal ERG (tests small areas), and pattern ERG (tests ganglion cells).
  • Use: Detects retinal dysfunction even before vision loss is noticeable.