Eye movement disorder
Eye movement disorderOphthalmologycenter850008549640April 10, 2020 1000000April 10, 2020 Collected by : Tha'er Ahmad AlajouEye movements may be abnormal because there is:1.? abnormal position of eyes.2.?reduced range of eye movements.3.?abnormality in character of eye movements.Extraocular Muscles actions (1°)Medial rectusAdductionLateral rectusAbductionInferior rectusDepressionSuperior rectusElevationSuperior obliqueIntorsionInferior obliqueExtorsionInnervation of EOMSuperior division of? Oculomotor (3rd ) nerveLevator palpebrae and? Superior rectus muscles.Inferior division of? Oculomotor nerveMedial rectus, Inferior? rectus and Inferior oblique? muscles.4th nerve? (Trochlear nerve)Superior oblique.6th nerve? (Abducens nerve)Lateral rectus.Strabismus (aka?squint/ crooked? eye) is a generic term applied to all those? conditions in which visual axes assume a? position relative to each other different from? that conforming to physiological conditions.Strabismus = squint : is deviation of an eye’s visual axis from it’s normalEso : inward Exo: outward Hyper: superiorly Hypo: inferiorlyTropia : always deviated ( manifest squint)Phoria : sometimes deviated (latent squint)Binocular single vision : both eyes are directed towards the same object of regard ,their movements are coordinated so that the retinal images of an object fall on corresponding points of each retina, these images are fused centrally, so that they are interpreted by the brain as a single image.stereopsis : Because each eye views an object from a different angle this permits a three-dimensional percept to be constructed. The development of stereopsis requires that eye movements and visual alignment are coordinated over approximately the first 5 years of life.Binocular single vision and stereopsis afford certain advantages to the individual:They increase the field of vision. They eliminate the blind spot, since the blind spot of one eye falls in the seeing field of the other. They provide a binocular acuity, which is greater than monocular acuity. Stereopsis provides depth perception and estimation of distance.If the visual axes of the two eyes are not aligned, binocular single vision is not possible. This results in: Diplopia : An object is seen to be in two different places. Visual confusion : Two separate and different objects appear to be at the same pointEye movement disorders :non-paralytic squint (concomitant)Deviation is equal in all of gaze and movement of both eyes are full ( there is no paresis ) but only one eye is directed towards the fixated target.It could be : monocular , alternating or intermittent Angle of deviation is constant and unrelated to the direction of gaze The common squint that is seen in childhood and usually begins in infancy , up to 8-10 yearsEtiology : may developed on normal child with normal eyes so the cause is obscure or idiopathic it thought to be caused by an abnormality in the central coordination of eye movements diplopia is absent.Amblyopia : is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together. Amblyopia only occurs in unilateral strabismusAmblyopia is reversible before 7-8 years examination and investigationFirst the patient is observed for features that may simulate a squint.These include: epicanthus (a crescentic fold of skin on the side of the nose that incompletely covers the inner canthus) ; hirschberg test to to detect pseudo squintDetermination of acuityDetermination of any refractive error .Detection of any abnormality in eye movement (H shape).Cover uncover testCareful examination of the eyes to exclude opacities of the cornea, lens or vitreous and ? abnormalities of the retina or optic disc.Cover – uncover test Pseudo strabismusIn young infant, strabismus must be differentiated from more common pseudo strabismus Pseudoesotropia as a result of a broad bridge of the nose, this is not a real eye crossing .Non paralytic squint with no associated ocular disease is treated as follows:Any significant refractive error is first corrected with glasses.Surgical intervention to realign the eyes may be required for functional reasons (to restore or establish binocular single vision) or for cosmetic reasons (to improve appearance and prevent a child being singled out at school)Paralytic squint (incomitant squint)Angle of deviation is different in different position of gaze.Extraocular movement are not full so there is under action of one or more of the eye muscles due to a nerve palsy or mechanical restriction of the muscles Neurogenic :Congenital hypoplasia/ absence of 3rd/ 6th nerve nucleus.Meningitis/ Encephalitis/ Syphilis.Brain tumors involving 3rd/6th nerve nucleus.Vascular lesions (Hypertension/DM/ Atherosclerosis)Head injury involving nerve trunks.Demyelination in MS (Multiple sclerosis).Neuromuscular junctionMyasthenia Gravis.---------History and examination:The patient usually complains of diplopia, there may be an abnormal head posture to compensate for the inability of the eye to move in a particular direction.Sixth nerve palsy results in failure of abduction of the eye.Fourth nerve palsy results in defective depression of the eye when attempted in adduction ,, usually the damage is bilateral due to head trauma ( concussion )??Third nerve palsy??Failure of adduction , elevation and depression of the? eyePtosisIn some cases? dilated pupil due to involvement of autonomic fibers??pupil involvement here can be a feature of extrinsic compression of the nerve.Posterior communicating artery aneurysm is an important cause of sudden onset of 3rd?CN. palsy? with pupillary dilatation.?Common in young adults (come with severe headache & sudden onset squint )Treatment :An isolated nerve palsy is related to coexistent systemic disease , if posterior communicating aneurysm is suspected, patient must be sent for neurosurgical review and angiography.?The most common cause of palsy is microvascular disease of a peripheral cranial nerve, associated with diabetes or hypertension. The nerve function often recovers over months. Especially in old ones.??Disease in the cavernous sinus may also be the cause of multiple nerve palsies such as 3rd , 4th and 6thDiplopia can be helped by fitting prisms to the patient ’ s glasses, which realign the retinal images.If eye movements fail to improve spontaneously then surgical intervention may be required..Disease of the extraocular musclesDysthyroid eye disease (Grave’s disease)Myasthenia gravis :?Pathogenesis caused by the development of antibodies to the acetylcholine receptors of striated muscle. It affects females more than males 15-50 years?Some 40% of patients may show involvement of the extraocular muscles onlySymptoms and signs:Variation in clinical signs and symptoms over days to weeks, with fatigability, is the hallmark of myastheniaVariable diplopia and variable ptosis may be presentDiagnostic tests :Confirmed by :electromyography By determining whether an injection of neostigmine? or edrophonium (cholinesterase antagonists) temporarily restores normal muscle movementTreatment :Patients are treated in collaboration with a neurologist , with neostigmine .Systemic steroids and surgical removal of the thymus Multiple choice questions1. Match the eye muscle to the nerve.a Lateral rectus.b Superior rectus.c Medial rectus.d Inferior rectus.e Superior oblique.f Inferior oblique.i Third nerve.ii Fourth nerve.iii Sixth nerve.2. Which of the following statements are true?a In a non - paralytic strabismus the movement of the eyes is reduced.b In a non - paralytic strabismus the angle of deviation is unrelated to thedirection of gaze.c In a paralytic strabismus, the eye movement is reduced.d Nystagmus refers to an oscillating movement of the eyes.e In a horizontal gaze palsy the patient is unable to look to one side.3. Amblyopiaa Refers to a developmental reduction in visual acuity.b May be caused by Duane ’ s syndrome.c May be caused by a previously unidentifi ed difference in refractive correctionbetween the two eyes.d May be caused by a squint.e May be treated by patching the amblyopic eye.4. Nerve palsies affecting the third, fourth on sixth cranial nerves may beseen ina Orbital disease.b Raised intracranial pressure.c Ischaemia of the cerebral cortex.d Systemic infl ammatory disease.e Trauma.5. Internuclear ophthalmoplegiaa Is caused by a lesion of the medial longitudinal fasciculus.b Manifests as a reduced adduction and contralateral nystagmus in theabducting eye.c Is manifested by a failure of the eye to elevate in adduction.d May be caused by demyelination.e Requires surgical treatment. ................
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