nystagmus(redirected from harmonic acceleration test)
Also found in: Dictionary, Thesaurus, Encyclopedia.
Causes and symptoms
- Albinism. This condition is caused by a decrease in pigmentation and may affect the eyes.
- Disorders of the eyes. This may include optic atrophy, color blindness, very high nearsightedness (myopia) or severe astigmatism, or opacities in the structures of the eyes.
- Acute labyrinthitis. This is an inflammation in the inner ear. The patient may have dizziness (vertigo), nausea and vomiting, and nystagmus.
- Brain lesions. Disease in many parts of the brain can result in nystagmus.
- Alcohol and drugs. Alcohol and some medications (e.g., anti-epilepsy medications) can induce or exaggerate nystagmus.
- Multiple sclerosis. A disease of the central nervous system.
nystagmus/nys·tag·mus/ (nis-tag´mus) involuntary rapid movement (horizontal, vertical, rotatory, or mixed, i.e., of two types) of the eyeball.nystag´mic
nystagmusOphthalmology Rapid involuntary oscillary eye movements Directions Horizontal, vertical, rotary. See Caloric nystagmus, Irritative nystagmus, Paralytic nystagmus, Recovery nystagmus, Opticokinetic nystagmus, Seesaw nystagmus.
nystagmusPersistent, rapid, rhythmical, jerky or wobbling movement of the eyes, usually together. The movement is usually transverse and most commonly of a ‘sawtooth’ pattern with a slow movement in one direction followed by a sudden recovery jerk in the other. This kind of nystagmus is often CONGENITAL and, in this case, although associated with some reduction in visual acuity, is usually of little significance. Nystagmus may also be pendular or, when vision is very poor, of a searching type. Acquired nystagmus is always of significance as it implies an acquired disorder of the nervous system.
nystagmus blockage syndrome See nystagmus blockage syndrome.
caloric nystagmus See caloric testing.
congenital nystagmus A motor nystagmus that is present at birth or soon after. It may be inherited as X-linked recessive or autosomal dominant, or induced in the uterus, and results from decreased vision due to corneal opacity, cataract, albinism, aniridia, macular disease or optic atrophy. It is typically a horizontal jerk nystagmus and it may be associated with abnormal head movement and decreases in intensity with convergence. The visual prognosis is reasonably good, but if the head turn is excessive, extraocular muscle surgery may be needed. See spasmus nutans.
convergence-retraction nystagmus A jerk nystagmus which appears on attempted upward gaze and in which the fast phase brings the two eyes towards each other in a convergent movement with retraction of the globes into the orbit. It may result from a lesion affecting the tectum or dorsal midbrain or a pineal tumour, or form part of Parinaud's syndrome. See pinealoma.
gaze-evoked nystagmus An acquired form of horizontal nystagmus characterized by a jerk nystagmus on eccentric gaze with the fast phase towards the direction of gaze. This type of nystagmus is believed to be due to cerebellar or brainstem disease affecting the conjugate gaze centres.
occlusion nystagmus A form of nystagmus occurring when one eye is covered, or which increases in intensity when one eye is covered. The nystagmus is typically of the horizontal, jerk variety, with the fast phase occurring in the direction of the occluded eye.
physiological nystagmus See fixation movements.
rotary nystagmus A very rare form of nystagmus in which the eyeball makes a movement about the visual axis. It may result from a lesion to the vestibular nerve. See vestibular nystagmus.
sensory nystagmus A form of nystagmus thought to be due to an abnormality in the afferent mechanism. It is most often due to inadequate image stimulation of the macula, leading to abnormal development of the ocular fixation reflex. Causes include congenital cataracts, optic nerve hypoplasia, aniridia, albinism, achromatopsia, as well as Leber's congenital amaurosis.
vestibular nystagmus There are two main types of vestibular nystagmus: Peripheral vestibular nystagmus results from stimulation, injury or disease (e.g. Menière's disease) of the labyrinth or of the vestibulo-cochlear nerve (VIII). It presents as a jerk, mainly horizontal, nystagmus with a torsional component. It may be accompanied by vertigo, tinnitus and hearing loss. Fixation inhibits the nystagmus. Central vestibular nystagmus results from stimulation, injury, disease of the central vestibular pathways of the brainstem or the cerebellum, or lesion of the vestibular nuclei. It is typically a jerk nystagmus, which can be purely horizontal, vertical or torsional. It is not inhibited by fixation.
Patient discussion about nystagmus
Q. My granddaughter has Nystagmus, diagnosed when she was about 9 month old. Is there a community for Nystagmus? We have taken her to see Paediatric Ophthalmologists in Singapore on a regular basis,since last year July. The little girl seems to be sensitive to light, especially white light. She can hardly open her eyes outside the house during day time.In the late evenings. she seems to be comfortable and can actually see things well. The eyes seem to be ok with house lightings at night.