2. • It is defined as regular and rhythmic to-and-fro involuntary oscillatory
movements of the eyes.
• It occurs due to disturbance of the factors responsible for maintaining
normal ocular posture.These include disorders of sensory visual pathway
,
vestibular apparatus,semicircular canals,mid-brain and cerebellum.
3. FEATURES
• 1.It may be pendular or jerk nystagmus.
- In pendular nystagmus movements are of equal velocity in each direction.It may be
horizontal,vertical or rotatory.
- In jerk nystagmus, the movements have a slow component in one direction and a fast
component in the other direction.The direction of jerk nystagmus is defined by direction of the
fast component (phase).It may be right,left,up,down or rotatory.
• 2.Nystagmus movements may be rapid or slow.
• 3.The movements may be fine or coarse.
• 4.Nystagmus may be latent or manifest
4.
5. TYPES 1.PHYSIOLOGICAL NYSTAGMUS
• 1.Optokinetic nystagmus.
-It is a physiological jerk nystagmus induced by presenting to gaze the objects moving serially in
one direction,such as strips of a spinning optokinetic drum.
-The eyes will follow a fixed strip momentarily and then jerk back to reposition centrally to fix
up a new strip.
- Similar condition occurs while looking at outside things from a moving train.
• 2.End-point nystagmus.It is a fine jerk horizontal nystagmus seen in normal persons on extreme right
or left gaze.
• 3.Physiological vestibular nystagmus.It is a jerk nystagmus which can be elicited by stimulating the
tympanic membrane with hot or cold water
.It forms the basis of caloric test.If cold water is poured
into right ear the patient develops left jerk nystagmus (rapid phase towards left),while the reverse
happens with warm water
,i.e.,patient develops right jerk nystagmus.It can be remembered by the
mnemonic‘COWS’ (Cold– Opposite,Warm–Same).
6. 2.SENSORY DEPRIVATION NYSTAGMUS
• 1.Congenital pendular (ocular) nystagmus.
- It is a horizontal slow pendular nystagmus usually associated with sensory deprivation due to reduced
central visual acuity
.
- Its common causes are congenital cataract,congenital toxoplas-mosis,macular hypoplasia,aniridia,
albinism,optic nerve hypoplasia and Leber’s congenital amaurosis.
• 2.Acquired ocular nystagmus.
- It occurs monocular adults when they develop decreased visual acuity in the only seeing eye.
- It is a pendular nystagmus.
• 3.Miner’
s nystagmus.
- It is a rapid rotatory type of nystagmus which occurs in coal mine workers.
- It probably results from fixation difficulties in the dim illumination
7. 3.MOTOR IMBALANCE NYSTAGMUS
• 1.Congenital jerk nystagmus.
- It is a hereditary nystagmus of unknown etiology which persists throughout life.
• 2.Latent nystagmus.
- It is not present when both eyes are open.It appears when one eye is covered.
• 3.Spasmus nutans.
- It is characterised by fine pendular horizontal nystagmus associated with head nodding and
abnormal head posture.It appears in infancy and self-resolves by the age of 3 years.
• 4.Peripheral vestibular nystagmus.
- It occurs due to diseases of the eighth nerve or vestibular end organ.
8. • 5.Central vestibular nystagmus.
- It may be of the following types:(a) Upbeat nystagmus.In primary position of gaze,the fast
component is upward.(b) Down beat nystagmus.In primary position of gaze the fast comp.
• 6.Gaze-paretic nystagmus.
- It is a slow horizontal jerk nystagmus due to upper brain stem dysfunction.
• 7.Convergence retraction nystagmus.
- It is a jerk nystagmus with bilateral fast component towards the medial side.It is associated with
retraction of the globe in convergence.
• 8.See-saw nystagmus.
- In it,one eye rises up and intorts,while the other shifts down and extorts. It is usually associated
with upper brain stem lesions.
• 9.Nystagmus blockage syndrome.
- It is a rare condition in which sudden esotropia develops in infancy to dampen the horizontal
nystagmus
