Oscillopsia - Permanent Oscillopsia Due To Impairment of The Ocular Stabilizing Systems

Permanent Oscillopsia Due To Impairment of The Ocular Stabilizing Systems

Ocular stability is maintained by three different ocular motor systems

1. The fixation system
2. The visuo-vestibular stabilizing system
3. Neural integrator

1. The fixation system and its deficit

• In the fixation system, the ocular motor noise that comes from microsaccades, microtremors and slow drifts (all necessary for important perceptual functions) are limited by the visual and cerebellar ocular motor feedback loops. The frontal basal ganglia and cerebellar network also helps to provide correct saccades and inhibit unwanted saccades for fixation.
• A deficit in this fixation system results in ocular instability that mainly leads to acquired pendular nystagmus and saccadic intrusions. Acquired pendular nystagmus is seen in a variety of conditions with the two most frequent being multiple sclerosis and oculopalatal tremor.

2. The visuo-vestibular stabilizing systems and their deficits

• The vestibular and visual ocular stabilizing systems interact together in order to maintain the image of the visual scene steady on the retina during a head and body displacement situation.
• A deficit in these vestibular or visual ocular stabilizing systems may result in ocular instability due to pathological jerk nystagmus. The vestibulo-ocular reflex deficit (especially when bilateral) and a deficit of vestibulo-ocular reflex inhibition can result in oscillopsia and impaired visual acuity during head and body displacement.

3. The neural integrator and its deficit

• The neural integrator helps to maintain a constant innervation of extra-ocular eye muscles to avoid backward drift of the eyes.
• A deficit in the neural integrator can result in gaze-evoked nystagmus and oscillopsia in the eccentric eye position.