Table 4.

Characteristic eye movement abnormalities in various movement disorders.

Name of movement disorder	Characteristic eye movement abnormalities
Parkinson's disease	Decreased amplitude of saccades (more for volitional & memory guided saccades than visually guided ones) Increased saccade latency (more for volitional & memory guided saccades than visually guided ones) Abnormality is saccade amplitude occurs earlier and is more severe than abnormality in latency Abnormal convergence movements with correlate with degree of motor abnormality Abnormal smooth pursuit movements with abnormal saccades during pursuit Excessive square wave jerks
PDD or DLBD	Greater impairment of visually guided saccades and complex saccades (memory guided, antisaccades)
MSA-P	Same as described under Parkinson's disease + Square wave jerks, moderate saccadic hypometria, impaired smooth pursuit, abnormal suppression of VOR
MSA-C	Gaze evoked, downbeat and rebound nystagmus Impaired smooth pursuit Square wave jerks
PSP	Prominent gaze abnormalities Vertical saccades affected earlier and greater than horizontal saccades Slowing of downward saccades: hallmark and diagnostic criteria Loss of saccades and pursuit in advanced stages Normal eye movements on VOR Excessive small amplitude square wave jerks Errors on tasks involving antisaccades
CBGD	Hallmark- Saccadic apraxia (difficulty and delay in initiation of saccades toward target i.e. increased saccadic latency with normal saccade velocity) Errors on tasks involving antisaccades
HD	Saccadic apraxia and slow hypometric saccades (abnormal saccade latency and velocity) Verbally guided, memory guided and antisaccades are affected more than visually guided ones Vertical saccades are affected more than horizontal Mild impairment of smooth pursuit Extent of decrease in velocity and increase in latency of saccades as well as errors on antisaccades correlate with disease severity

Abb: PDD: Parkinson disease with dementia; DLBD: Diffuse Lewy body disease; MSA-P: Multisystem atrophy (parkinsonism type); MSA-C: Multiple system atrophy (cerebellar type); PSP: Progressive supranuclear palsy; CBGD: Cortico-basal-ganglionic degeneration; HD: Huntington disease; VOR: vestibulo-ocular reflex.