The Characteristics of Nystagmus Essay

Definition

Nystagmus is a medical condition where a person’s eyes are involved in a rapid, involuntary, and repetitive movement. (Snow & Wackym & Ballenger, 2009).

Types of Nystagmus

The movement of the eyes determines the nature of Nystagmus a person is suffering from. In most cases of Nystagmus, the movement of the eyes is usually from left to right or right to left. This type of Nystagmus is known as horizontal Nystagmus. Nystagmus can also affect the eye and cause it to have involuntary, repetitive, and rapid movement from up to down. This kind of Nystagmus is known as vertical Nystagmus. Another kind of Nystagmus – although very rare – causes the eyes to move in a circular motion. This kind of Nystagmus is known as rotary Nystagmus. Although there is a variance with regards to the speed of the movement caused by this medical condition, the movement of eyes in such a condition involves both eyes. (Urban & Caplan, 2011)

Patho-physiology and causes of Nystagmus

In the analysis of the pathophysiology of Nystagmus, there are four important things to take note of. There is Nystagmus due to the disease of the visual pathways, Nystagmus due to imbalance in the vestibular system, Nystagmus due to disturbance of mechanisms holding eccentric gaze, and supranuclear eye movements. With regards to the visual pathways, a disorder in the visual pathways can result in Nystagmus. This is usually the consequence of two completely separate mechanisms; suppression of unwanted saccades and deprivation of motion vision information. The Nystagmus that is caused due to an imbalance in the vestibular system usually affects the semicircular canals. Here, the pattern that is generated by the labyrinthine is affected and this causes Nystagmus. Disturbance of the mechanisms that hold the eccentric gaze in place also causes Nystagmus. Here, the extra ocular muscles and the numerous elastic forces that are involved in orbital tissues are affected. In the event these are affected and the communication between the brain and the muscles is disconnected or interrupted, it usually results in horizontal Nystagmus. In the analysis of supranuclear eye movements and how these are related to the pathogenesis of the different forms of Nystagmus in young children – there are a number of movements that are studies. These include the eye movements in neonates, abnormal eye movements, primate eye movements, conjugate and dysconjugate. There are also a number of reflexes that are analyzed under the same topic. These include the optokinetic reflex and the vestibuloocular reflex. (Snow & Wackym & Ballenger, 2009).

There are a number of causes of pathological Nystagmus. The different causes can be classified into idiopathic, congenital, and also as a secondary disease to an already existent neurological disorder. With regards to congenital Nystagmus, the affected persons are usually unaware of the change in movement of the eye. However, vision can be impaired in congenital Nystagmus but this depends on the nature and level of severity of the initial movements. Some of the congenital Nystagmus causes include aniridia, rod monochromatism, Nystagmus blockage syndrome, infantile, bilateral congenital cataracts, idiopathic, bilateral optic nerve hypoplasia, Noonan syndrome, optic nerve disease, macular disease, and latent Nystagmus. Some of the metabolic and toxic causes of the disease include barbiturates, alcohol intoxication, ketamine, benzodiazepines, lysergic acid diethylamide, lithium, methylenedioxyamphetamine, methylenedioxymethamphetamine, phencyclidine, phenytoin, SSRI’s, Wernicke’s encephalopathy, salicylates, and thiamine deficiency. The central nervous systems disorders that can cause the diseases include cerebellar ataxia, multiple sclerosis, trauma, Chiari malformation, tumor, and thalamic hemorrhage. Other causes include Whipple’s disease, Tulio phenomenon, trochlea nerve malfunction, head trauma, Menieres disease, balance disorders, and Pelizaeus-Merzbacher disease. (Joseph & Cass, 2003).

Difference between motor and sensory Nystagmus

Although there are a number of differences that exist with regards to motor and sensory Nystagmus, the main difference lies within the cause. Motor Nystagmus is usually caused by a neurological problem whereas sensory Nystagmus is cause by diseases affective the eyes. (Desmond, 2011)

Difference between latent and manifest Nystagmus

There are a number of differences with regards to latent and manifest Nystagmus. In manifest Nystagmus, the disorder is usually biphasic and there is pendular increasing velocity in the slow phase. In latent Nystagmus,, the disorder is usually jerking, with decreasing velocity in the slow phase. Manifest Nystagmus does not present any change on the unilateral occlusion but latent Nystagmus increases the overall unilateral occlusion. In manifest Nystagmus, the direction is usually independent of the fixating eye whereas latent Nystagmus entails past phase towards fixating eye. Very few cases of manifest Nystagmus as associated with infantile esotropia whereas most – if not all – of the cases of latent Nystagmus are associated with infantile esotropia. In latent Nystagmus, the binocular visual acuity is better than monocular visual acuity even though they are the same in manifest Nystagmus. (Straube, 2007)

Congenital type and acquired type Nystagmus

Cases of congenital Nystagmus are more frequent compared to the cases of acquired Nystagmus. In congenital Nystagmus, the disorder can be accompanied by another disorder or manifest as being insular. Some of the disorders that accompany congenital Nystagmus include Down syndrome and micro-ophthalmic anomalies. Compared to acquired type Nystagmus, congenital Nystagmus is usually non-progressive and mild in nature. Although there is the possibility of vision impairing, the people suffering from this disease are usually unaware of the effects. Unlike congenital Nystagmus which presents itself early in life, acquired Nystagmus is usually common in adults. Acquired Nystagmus presents itself as a sign or signal for another disorder or medical condition. (Desmond, 2011)

Visual acuity measurements for Nystagmus

There are different ways of measuring the visual acuity in Nystagmus patients. One such method is through the use of the opticokinetic reflex. Mostly, opticokinetic reflex is employed in analyzing the visual acuity that exists in newborn infants. There are a number of importamt factors at play with regards to these measurements. These include the reflex arc of the retina, the optic tract, the optic nerve, the optic cortical areas, the ocular motor centers, and the cranial nerves. (Straube, 2007)

The Null position and prism therapy

The null position is usually concerned with the unusual positions of the head and eye. Unlike normal people, patients who are affected by Nystagmus have to find a position where vision is optimum. A comfortable position for patients suffering from Nystagmus which provides them with clear and better visions is called the null position. The null position will vary from one Nystagmus patient to another. It is usually very important to ensure that the Nystagmus patients are provided with the physical and psychological support they need with regards to attaining better vision. Cosmetic appearance is enhanced on patient’s eyewear by adding prisms on them. Here, the null position is usually changed or adjusted so as to assume the best normal position without causing any form of discomfort or disturbance. This is very important in administering eyeglasses to patients who suffer from Nystagmus. (Desmond, 2011)

Effects of Nystagmus

Nystagmus affects different people in completely different ways. Although two people may be classified as suffering from the same condition, there effects of Nystagmus are almost unique in all the people who suffer from the disorder. As a result of Nystagmus, people develop a null point. Here, a person’s vision through a number of angles is affected and they are not able to see well whenever they are in that position. As a result, they are forced to look for an angle which will ensure that their head position and eye position are in the best and most comfortable viewing position. Finding this position is tiresome and makes one look confused. In the event they such a person is expected to view something normally, they may feel embarrassed while trying to look for the right and comfortable angle of view. (Urban & Caplan, 2011)

Sharing books or other reading materials is also a challenge to the different people who suffer from this condition. There are also challenges presented with regards to reading small texts from a distance as well as looking at unclear handwritings. Reading or viewing things in dim light is also one of the greatest challenges with regards to this medical disorder. People suffering with Nystagmus also have a problem with regards to lighting and reading. For such people, the amount of light that is present during the process of reading should be controlled. Here, it is important to ensure that the lighting is optimum and that the reading position is perfect. People suffering from Nystagmus also have a problem with regards to body balance. Their body balance is affected and most of these people have a hard time stating in balance. (Snow & Wackym & Ballenger, 2009).

References

Desmond, A. (2011). Vestibular Function: Clinical and Practice Management. New York: Thieme New York. Web.

Joseph M. F., and Cass, S.P. (2003). Vestibular Disorders: A Case-Study Approach. London: Oxford University Press. Web.

Snow, J.B. and Wackym, P.A. and Ballenger, J.J. (2009). Otorhinolaryngology. Shelton, Connecticut: People’s Medical Publishing House/B C Decker.

Straube, A. (2007). Neuro-Ophthalmology: Neuronal Control of Eye Movements. Basel: Karger.

Urban, P., and Caplan, L.R (2011). Brainstem Disorders. Heifelberg: Springer Publishers. Web.