NEURO-OPHTHALMOLOGY . . . CONT.

Jerking Nystagmus

due to brainstem, labyrinthine, cerebellar disease

rapid movement in one direction, slow movement in opposite direction

Coarse Nystagmus

due to weakness of ocular muscles or lower motor neuron disease

coarse jerking in the direction of the weakened muscle

Normal Nystagmus

endpoint

•at extremes of gaze, subsides after a few beats

•also seen in patients on anticonvulsant therapy

evoked

•optokinetic: occurs when patient viewing a moving object

•vestibular: labyrinthine stimulation from thermal or rotatory movement

•unlike central lesions, vestibular nystagmus is suppressed by fixation

Abnormal Nystagmus

any nystagmus which occurs in the field of binocular vision persistently

vertical nystagmus

•always abnormal if persistent

•up-beating: usually due to acquired disease or lesion in medulla

•down-beating: usually due to lesion in lower brainstem or upper cervical cord

congenital nystagmus

•pendular, may cause amblyopia from poor fixation

gaze-evoked nystagmus

•in certain fields of gaze

•with a brainstem/cerebellar lesion, acoustic neuroma phenytoin, ethanol, barbiturates, demyelinating diseases

spasmus nutans

•asymmetrical fine nystagmus of unknown pathogenesis

•in children 4-12 months of age, usually recover by 2 years

•head nodding to offset pathological eye movements

ataxic nystagmus

•one eye has more marked nystagmus than the other

•associated with internuclear ophthalmoplegias

INTRAOCULAR MALIGNANCIES

uncommon site for primary malignancies

eye usually affected secondarily by cancer or cancer treatments

MALIGNANT MELANOMA

most common primary intraocular malignancy

more prevalent in Caucasians

arise from uveal tract

hepatic metastases predominate

Management

choice is dependent on the size of the tumour

radiotherapy, enucleation, limited surgery

RETINOBLASTOMA

incidence: 1/1000; sporadic or genetic transmission

unilateral or bilateral (in 1/3 of cases)

malignant - direct or hematogenous spread

diagnosis

•may be detected by leukocoria (white pupil) in infant

•CT scan: dense radiopaque appearance (contains calcium)

Management

radiotherapy, enucleation(removal of globe from eye socket), or both

METASTASES

most common intraocular malignancy in adults

most common from breast and lung

usually infiltrate the choroid, but may also affect the optic nerve or extraocular muscles

may present with decreased or distorted vision, irregularly shaped pupil, iritis, hyphema

Management

local radiation, chemotherapy

enucleation if blind painful eye