Synchronous optokinetic nystagmus. The prediction area in normal humans

Area of Science:

• Ophthalmology
• Neuroscience
• Gerontology

Background:

• Optokinetic nystagmus (OKN) is a crucial reflex for maintaining visual fixation during head movement.
• Age-related changes in visual-vestibular function are common, but their impact on OKN requires further elucidation.

Purpose of the Study:

• To investigate age-related differences in horizontal optokinetic nystagmus (OKN) responses.
• To determine the normal variation in eye velocity during OKN in different age groups and at varying target speeds.

Main Methods:

• 150 healthy subjects were divided into two age groups: young (17-50 years) and older (65-89 years).
• Horizontal OKN was assessed at target speeds of 10 and 20 degrees/sec.
• Electrooculography (EOG) was used to record eye movements; vertical OKN recordings were unstable.

Main Results:

• All participants were within the synchronous response range, indicating regular nystagmic beats.
• No significant age- or speed-dependent asymmetry in horizontal eye velocity was observed.
• Considerable individual variation in eye velocity was noted, which decreased when comparing clockwise and counter-clockwise movements.

Conclusions:

• Horizontal OKN responses remain largely preserved in most older adults compared to younger individuals.
• Individual variability is a significant factor in OKN eye velocity, more so than age or target speed within the tested parameters.
• Further research may be needed to understand the reasons for the few older adults who exhibited irregular OKN responses.