Differences in pupillary light reflex between optic neuritis and ischemic optic neuropathy.

Area of Science:

• Ophthalmology
• Neuroscience

Background:

• Optic neuritis (ON) and nonarteritic anterior ischemic optic neuropathy (NAION) are leading causes of vision loss.
• Pupillary light reflex (PLR) abnormalities can indicate optic nerve dysfunction.

Purpose of the Study:

• To compare pupillary light reflex (PLR) characteristics in the acute and chronic phases of ON and NAION.
• To identify differences in PLR between these optic neuropathies and healthy controls.

Main Methods:

• PLR was measured using a dynamic pupillometer in 30 ON patients, 22 NAION patients, and 58 controls.
• Key PLR parameters analyzed included latency, constriction velocity, and constriction ratio.
• Regression analysis explored correlations between PLR and visual function metrics.

Main Results:

• Acute ON and NAION showed significantly decreased pupillary constriction velocity, ratio, and latency compared to controls.
• ON exhibited delayed constriction latency versus NAION (P=0.047).
• PLR parameters recovered in chronic ON but not in chronic NAION.

Conclusions:

• Both acute ON and NAION present with significant pupillary light reflex deficits.
• The recovery of PLR in chronic ON, contrasted with its persistent impairment in NAION, suggests distinct pathophysiological mechanisms.