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KirsiSetälä
SariAtula

Neurological Eye Symptoms

Essentials

  • An impression of the site of a neuro-ophthalmic lesion and its possible cause may be obtained by examining
    • visual acuity
    • visual fields
    • eye movements
    • pupillary reactions
    • size difference between the pupils.
  • Diagnosis and treatment require the cooperation of an ophthalmologist and a neurologist.

Impaired visual acuity

  • A careful history is important.
    • Is the vision impaired only in one eye or in both eyes?
    • Did the vision deteriorate suddenly or gradually?
      • Sudden deterioration: vascular origin?
        • Patients over 50 years: ischaemic optic neuropathy (the onset is not always sudden and, in some cases, vision may deteriorate over a few days)
      • Deterioration over a few days: optic neuritis?
        • Particularly in young adults
      • Gradually deteriorated sight: optic nerve compression?
  • How did the patient notice the problem?
    • By chance covered the other eye: the aetiology may originate from the eye, e.g. a cataract or macular degeneration.
  • If the visual acuity is impaired only in one eye, it is important to examine the pupillary reactions before dilating eye drops are administered: relative afferent pupillary defect (RAPD) is the only objective sign of unilateral or asymmetric optic nerve lesion.
  • See also .

Unequal size of the pupils (anisocoria)

  • Physiological anisocoria is very common: in 20% of individuals the pupils are not totally equal in size.
  • Ask initially about eye surgery or trauma, eye drops? For how long have the pupils been unequal in size (are there old photographs)?
  • Examine both pupils, do they react normally?
  • If both pupils react normally, the patient has either Horner's syndrome or physiological anisocoria.
    • Horner's syndrome (a disturbance of the sympathetic innervation): ptosis and miosis (occasionally impaired sweating ipsilaterally); picture Horner's Syndrome.
    • It is important to localise the site of the problem, and further investigations are carried out accordingly.
    • In acute Horner's syndrome with ipsilateral facial/neck pain, suspect carotid artery dissection.
      • Emergency imaging studies of the carotid arteries
    • In young individuals (women), one pupil may show intermittent (hours-days) dilatation: a migraine variant?
  • Unilateral impairment of pupillary response: disturbance of the parasympathetic innervation
    • One pupil dilated, symmetric and round with no reaction to light: oculomotor nerve palsy induced by an aneurysm or other compression. Almost always diplopia (may be mild).
      • Oculomotor nerve palsy + fixed dilated pupil: emergency magnetic resonance imaging (MRI) and magnetic resonance or computed tomographic angiography (MRA or CTA)
    • In injured or unconscious patients, a dilated pupil may be indicative of increased intracranial pressure and imminent herniation.
  • If the only sign is a fixed and dilated pupil, administer 1% pilocarpine eye drops into each eye (the unaffected eye will act as a control).
    • If the pupil constricts: an aneurysm of the basilar artery tip?
    • If the pupil does not constrict: a pharmacological blockade? An atropine-like drug has been administered to the eye, either by accident or knowingly.
      • Has the patient been in contact with plants, works in a hospital, has a family member with iritis or has the patient used antinausea patches?
  • If one pupil is slightly irregular, reacts poorly to light and flashes of bright light induce vermiform movements at the edge of the pupil, the patient is likely to have a tonic pupil (Adie's pupil).
    • The affected pupil is initially larger than the contralateral pupil but will become smaller over the years; however, the pupillary reactions will remain poor, slow and tonic.
    • More common in young women
    • In 20-30% of cases the condition becomes bilateral. The patellar reflexes are absent in one third of patients.
    • A tonic pupil constricts with 0.1% pilocarpine drops (denervation supersensitivity)
    • A tonic pupil is a benign condition and needs no further investigations.

Diplopia (double vision)

  • A careful history is important: binocular or monocular diplopia?
  • If diplopia persists when the patient covers one eye, the origin of diplopia is in the uncovered eye: cornea, lens, macula.
    • A referral to an ophthalmologist
  • Binocular diplopia: true double vision
  • Intermittent diplopia, more when tired: the patient may have heterophoria.
    • Cover test is indicated.
    • Examine the range of ocular movements: any deficits?

Ophthalmoplegia

Oculomotor nerve (the 3rd cranial nerve)

  • The oculomotor nerve innervates the majority of the muscles responsible for eye movement as well as the levator muscle of the upper eyelid and the muscle controlling pupil constriction.
  • Complete oculomotor nerve palsy: ptosis with poor elevation, depression and adduction of the eye, the eye is turned outward (+ slightly downward) and the pupil is dilated and not reacting to light. Emergency imaging warranted; an aneurysm or other nerve compression is likely.
  • If the oculomotor nerve palsy is otherwise complete but there is no pupil involvement, the likely diagnosis is a microinfarct involving the nerve itself.
    • Will resolve within a few months.
    • If the patient is elderly and has vascular risk factors, imaging studies are not indicated, but the patient does need regular follow-up.
  • The possibility of temporal arteritis must be borne in mind.
  • A normal pupil does not exclude nerve compression in incomplete oculomotor nerve palsy.

Trochlear nerve (the fourth cranial nerve)

  • The trochlear nerve innervates the muscle that allows the depression, adduction and intorsion of the eye.
  • Trochlear nerve palsy causes diplopia that is worse when looking down; spiral staircases, reading, eating etc.
  • Often present at birth, but noticeable diplopia may not develop until around the age of 20-30 years. Old photographs are useful in diagnosis: characteristic head tilt.
  • Because the trochlear nerve exits from the posterior aspect of the brain stem, it is the nerve most likely to be injured by trauma, e.g. by a fall backwards; a sudden jolt may result in damage.
  • Trochlear nerve palsy may also be caused by a microinfarct. More rarely, nerve compression is the cause.

Abducens nerve (the sixth cranial nerve)

  • The abducens nerve innervates the lateral rectus muscle. In abducens nerve palsy, the inability of the affected eye to abduct results in esotropia.
  • In elderly patients the most common cause is a microinfarct of the abducens nerve, which will resolve spontaneously within a few months.
  • Other aetiologies include nerve compression and lesions within the cavernous sinus.
  • If the intracranial pressure is increased the patient may exhibit unilateral or bilateral weakness of the abducens nerve function.
  • Nuclear damage within the brainstem is often also accompanied by other neurological signs and typical paresis.
  • Damage to the abducens nucleus does not produce isolated abducens palsy but causes gaze palsy.

Internuclear ophthalmoplegia (INO)

  • INO is the most common eye movement disturbance in multiple sclerosis.
  • Damage occurs in the medial longitudinal fasciculus with the result that a message does not cross over from the abducens nucleus to the medial rectus subnucleus.
  • For example, with a gaze to the left, the right eye fails to adduct and the left eye may demonstrate jerky movements (nystagmus).
  • In elderly patients, the most common aetiology for INO is vascular.

Myasthenia gravis

  • If the patient has intermittent diplopia that is worse when tired, and either unilateral or bilateral ptosis, the possibility of myasthenia gravis should be borne in mind.
  • Myasthenia gravis may mimic any eye movement disorder, including oculomotor nerve palsy and INO.

Papilloedema

  • The condition is (almost always) bilateral (pictures Papilloedema Caused by High Intracranial Pressure Papilloedema).
  • Loss of spontaneous venous pulsation
  • The visual acuity is usually good.
  • Signs of increased intracranial pressure (headache, nausea, reduced level of consciousness)
  • The cause for papilloedema must be identified quickly: imaging studies.
    • Differential diagnosis: an optic nerve head with an unusual appearance: optic disc drusen (ODD)?
    • If there are no other signs of increased intracranial pressure, an ophthalmologist must be consulted.