1. 1. -QURESHI HAMZA THIRD YEAR
2. 2. INTRODUCTION Nystagmus is not a disease, it is manifestation of diseases involving either the eyes or extra ocular neural structures with predominant ocular signs. It is a clinical neuro-ophthalmic puzzle with about forty classifications, none of which is very accurate. Nystagmus is a disturbance of ocular posture. Nystagmus is defined as repetitive, rhythmic oscillation of one or both eyes in any or all fields of gaze. Exact mode of development of nystagmus is not well understood. During steady fixation the eyes are motionless, without any to and fro movement, that is brought about by afferent path, efferent path and intra cerebral components. Defect in any of them results in involuntary movements of the eyes, i.e. nystagmus. Ninety percent of nystagmus are brought about by afferent defect. Rests are efferent in nature. The afferent nystagmus are due to defective vision. Defective vision in early infancy is more likely to cause nystagmus. The common conditions associated with nystagmus areCongenital cataract, albinism, aniridia, hypoplasia of optic nerve, achromatopsia, and optic atrophy. The efferent nystagmus are due to ocular motor disturbance
3. 3. Classification Nystagmus can be congenital or acquired. Congenital nystagmus is always pathological. Nystagmus is described clinically under following heads: 1. Morphology 2. Plane 3. Amplitude 4. Frequency 5. Degree
4. 4. 1. Morphology i). Pendular nystagmusIt has oscillation of equal speed and amplitude on each direction like a pendulum of a wall clock generally in primary position. They can be horizontal, vertical or rotatory. The horizontal pendular nystagmus is the commonest type of all nystagmus. The most probable etiology is sensory deprivation caused due to diminished central vision mostly of congenital nature. Some of the them may be acquired in children. Common congenital causes are macular hypoplasia, achromatopsia,Lebers congenital amaurosis, hypoplasia of optic nerve, albinism and congenital cataract, albinism, aniridia The conditions that are acquired in childhood and infancy causing nystagmus are Developmental cataract, corneal opacities, high errors of refraction. Sometimes pendular nystagmus may be seen in many members of the same family. This is called hereditary pendular nystagmus. Such members do not have any associated ocular or neurological defects and these cases last for rest of life without progress. Other causes of pendular nystagmus are: Drug toxicity, lesions of brain stem, miners nystagmus and acquired unilateral nystagmus. The horizontal pendular nystagmus has a slow, smooth to and fro movement equal on both directions. The movements become milder on convergence. They persist on dim light but disappear on closure of eyes. The central vision is invariably poor.
5. 5. Miners nystagmus This is seen exclusively in coal miners who have to spend hours in dim light underground and keep a constant crouched posture with up gaze. They generally have mental fatigue. The nystagmus is mostly pendular, rarely it may be jerky. It is present in up gaze. Most of the cases have horizontal nystagmus, next in frequency are vertical and rarely it may be circular or oblique. ii). Jerk nystagmus This is a biphasic nystagmus, i.e. it has a slow phase in one direction and a rapid phase in the opposite direction. The jerk nystagmus is named after the direction of the rapid phase, it could be right, left, up or down according to direction of the rapid phase. The slow phase is the fundamental phase while the rapid phase is the compensatory phase. The former is also pursuit phase, the latter is saccadic phase. The causes of jerk nystagmus can be congenital or acquired. They can be physiological as well as pathological. The common examples of jerk nystagmus are: Optokinetic nystagmus, end point nystagmus, vestibular nystagmus, latent nystagmus, gaze paretic nystagmus, congenital jerk nystagmus.
6. 6. iii. Mixed nystagmus This is rare than the pendular or jerk nystagmus where the pendular nystagmus is seen in primary position and jerk nystagmus is seen when the eyes deviate. Null point and null zone The excursion of the eyes is not equal throughout their movements. In between the two ends of movement, there is an area where the nystagmus is least or absent. This distance may be reduced to a point. The distance is called null zone. The patient becomes aware of its presence and tries to keep this zone nearer to the primary position of the eye. If the null point falls outside the primary gaze the patient develops an abnormal head posture to maintain the gaze in a position that has least oscillation. Neutral zone is where the direction of nystagmus changes from one side to the other.
7. 7. 2. Plane of nystagmus can be horizontal, vertical, torsional or oblique. The horizontal plane is the commonest plane. 3. Amplitude This is measurement of excursion of the eyeball in degrees during oscillation. It is graded as fine, medium or coarse. Fine is less than 5, while coarse (large) is more than 15. The medium amplitude comes in between. 4. Frequency (rate) This is in cycles per second and designated as rapid and slow. Generally the rate varies with amplitude faster the rate, finer the amplitude and vice-versa. 5. Degrees of nystagmus These are based on Alexanders law which states that the amplitude of jerk nystagmus is largest in the gaze of direction of fast component. One the basis of this the nystagmus has been put in three degrees: i. First degree The nystagmus is present only in the gaze in the direction of fast component. ii. Second degrees Nystagmus is also present in position of primary gaze. iii. Third degree The nystagmus is present in direction of slow components.
8. 8. Classification of nystagmus Nystagmus is a disorders that has been subjected most probably to maximum number of classifications, none of which seem to be self-sufficient encompassing all. The most widely used classification is to differentiate between two groups: 1. Physiological nystagmus 2. Pathological nystagmus The next common division is: Congenital (infantile) Acquired Both the above, can either be due to ocular causes or nonocular causes. The ocular causes of nystagmus are Macular hypoplasia, optic nerve hypoplasia, achromatopsia, albinism, high errors of refraction, congenital cataract, Lebers congenital amaurosis see above. The ocular nystagmus are congenital or infantile in nature. They follow the rule of 2-4-6, which is as follows: i. If the child has poor vision before 2 years of age he will always develop some type of nystagmus. ii. Between 2 to 4 years, only some children with central loss of vision will develop nystagmus. iii. If the loss of central vision develops after 6 years of age, chances of developing nystagmus are nil.
9. 9. Classification Nystagmus can be either: Jerk - fast one direction, slow the other Pendular - equal velocity in both directions Mixed - of above And can be Horizontal/Vertical/Oblique or Rotary In overwhelming majority of cases both eyes move in a co- ordinated manner
10. 10. Physiological Nystagmus not due to a disease process Has no benefit, except as a diagnostic tool Not associated with reduced VA Examples include End point nystagmus Postrotational nystagmus Induced caloric testing Optokinetic nystagmus Voluntary nystagmus
11. 11. Sensory deprivation Due to a defect in the neural control of fixation Poor macular function that cannot be restored and therefore of little clinical significance Typically pendular and horizontal Reduced by convergence and head posture If a child loses vision before 2 yrs they will invariably develop nystagmus After 6 yrs they usually do not develop nystagmus In between 2-6years it is Less predictable
12. 12. Motor Imbalance Congential Spasmus Nutans Latent nystagmus Ataxic nystagmus Downbeat nystagmus Upbeat nystagmus Convergence retraction nystagmus See-Saw nystagmus Periodic alternating nystagmus
13. 13. CONGENITAL NYSTAGMUS due to a congenital anomaly of the motor system or to a congenital disorder of vision Inherited as X-link recessive or autosomal dominant trait may appear during early childhood but is rarely present at birth. Generally horizontal jerk type Absent in sleep Visual impairment is variable
14. 14. Spasmus Nutans Nystagmus, involuntary head movements, AHP Onset 3-18 months of age Fine rapid eye movements; jerky, small amplitude, high frequency Horizontal, vertical or rotary, or a combination of these Considerable variation in nystagmus in different positions of gaze Involuntary head movements comprising nodding or shaking, or a combination of both; variable. Head movements do not appear to compensate for eye movement as they are of a different frequency Most cases resolve spontaneously by age 3 years. Benign, but can be associated with CNS disease, therefore should be investigated.
15. 15. Latent Nystagmus Horizontal jerk nystagmus presents when the light stimulus is reduced to either eye (eg by occluding). In latent, no observable movement is present on uncovering and full BSV is restored. Jerk nystagmus with fast phase towards the uncovered eye Often noted in early childhood but can be observed in adults (especially if they have had strabismus surgery or in DVD)
16. 16. Downbeat Nystagmus Has a fast downward beat Pathognomic of a brain lesion at the cervicomedullary junction at the foramen magnum
17. 17. Upbeat Nystagmus Commonly caused by drug intoxication (eg phenytoin - used as an anticonvulsant) May be associated with a brain lesion at the posterior fossa Often worsens in upgaze base up prisms in reading glasses can be used to force the eyes downward
18. 18. Convergence Retraction Nystagmus Jerk nystagmus Fast phase generating convergence and retraction of globe into orbit Usually associated with brain lesion in the pretectal area
19. 19. See-Saw nystagmus Usually an acquired motility disorder associated with chiasmal lesions where one eye elevates and intorts followed by depression and extorsion of the other eye May be associated with a chiasmal lesion (bitemporal hemianopia could be present) Rare
20. 20. Periodic Alternating nystagmus Very rare jerk nystagmus Nystagmus changes amplitude and direction Associated with vascular or demylinating brainstem disease
21. 21. Recording on paper. Up gazeUp right gaze Up left gaze Down and left gazeDown gazeDown & right gaze
22. 22. Interpretation Amplitude : Length of the arrow Frequency : Number of arrow Direction: Head of arrow Waveform: shape of shaft of arrow No nystagmus ( null zone )
23. 23. Management of nystagmus Lack of precise knowledge about nystagmus makes its management difficult. The management may be broadly divided into two parts: 1. Directed towards the systemic causes that results in nystagmus, i.e. infection, inflammation, trauma, neoplasm etc. These are outside the domain of ophthalmologist. They are best treated by neuro physician or neuro surgeon. 2. Directed towards the ocular manifests. Which is managed by ophthalmologist and optometrist. The aim of which are: i. Improve vision ii. Correct physical appearance by way of: a. Minimize nystagmus b. Correct head posture c. Manage squint and amblyopia.
24. 24. The above goals are achieved by a combination of: a. Medical treatment b. Optical correction c. surgery: a. The medical management consists of: i. GABA agonist, anti convulsants, sedatives and tranquillisers. They are Gaba pentin, baclofen, clonazepam, valproate, carbamazipine. ii. Retro bulbar injection or infiltration of spastic extraocular muscle with botulin toxin type A (Botox). The therapeutic agents are best administered under supervision of physician. b. Optical correction consists of salvaging the best correctable vision by: i. Spectacles ii. Contact lenses iii. Uniocular telescope for distance c. Squint is managed by: i. Optical correction ii. Prisms they are used to dampen the action of stronger muscles and place the eyes in position of least nystagmus. iii. Surgery to correct squint and to move the eyes into null zone. This is claimed to correct abnormal head posture. The commonest procedure is known as Kestenbaum Anderson procedure.(is designed to help realign the head or eliminate face turn in nystagmus with null point)
25. 25. Treatment Aim : to improve VA by Stabilizing the eyes. Decreasing oscilopsia Shifting neutral zone in any compensatory head posture
26. 26. Treatment Low-vision aids can often help improve vision. They may include large print or high contrast materials, good lighting, and magnifying devices. Prevention- There is no known way to prevent nystagmus.
27. 27. Genetic counseling - Autosomal Dominant-A gene for autosomal dominant congenital nystagmus localizes to 6p12 - Autosomal Recessive - X-Linked-Mutations in the FRMD7 gene cause X-linked infantile nystagmus - Genetic counseling can help the patient and family understand the odds of passing the condition to their children. Not all cases of early onset nystagmus are hereditary. - Neurologic or neuro-ophthalmic consultation should be considered.
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