SIGNS AND SYMPTOMS
A small percentage of patients possess a form of the disease known as ocular myasthenia. Here, the signs and symptoms remain strictly confined to the extraocular muscles. The pupil is never involved in MG.
Systemic symptoms include intermittent fatigue of the limbs, weakness of
the facial muscles and difficulty breathing, chewing, talking and swallowing. In a small
percentage of patients, dysthyroidism may also be present, resulting in the mixture of
ptosis and exophthalmos. Thymic neoplasia (thymoma) is an associated finding in patients
over 65. Associated disorders such as diabetes mellitus, lupus erythematosus and
rheumatoid arthritis occur in 20 percent of MG patients.
Up to 75 percent of patients with myasthenia present with some type of ocular symptom. Ninety percent of patients with myasthenia gravis will develop ocular signs or symptoms, and 80 percent of patients who present with ocular involvement progress to have involvement of additional muscle groups within two years of the initial presentation.
Signs and symptoms may be initiated, exacerbated or mimicked by
medications such as D-penicillamine, antibiotics (polymyxn B, neomycin, gentamicin,
streptomycin), beta blockers and anticonvulsants.
In office tests for the optometrist include:
1. asking the pertinent history
2. testing the pupils
3. assessing the orbicularis function by asking the patient to squeeze their eyelids shut while you attempt to open them forcibly
4. attempt to elicit diplopia by eliminating the occlusive effects of ptosis
5. attempt to elicit superior rectus or levator fatigue by asking the patient to sustain upgaze while you observe for unexpected eyelid droop
6. attempt to elicit the Cogan's lid twitch sign by asking the patient to look into downgaze for an extended period, then to gaze up
7. apply an ice pack to the eyelid for five to 15 minutes, reevaluating the ptosis and/or ocular motility for improved position following the ice packs removal
8. ask the patient to close their eyes for 30 minutes (sleep test), reevaluating the ocular motility and/or ptosis for improved position upon awakening. Diagnosis may also be assisted by evaluating old photographs for appearance.
The quintessential method of diagnosing MG is the endrophonium
hydrochloride (Tensilon) injection test. An additional laboratory test used for diagnosing
MG is the acetylcholine antibody receptor test. Medical management of MG should be handled
by the neurologist or neuro-ophthalmologist.
Other reports in this section
Eyelids & Eyelashes | Conjunctiva & Sclera | Cornea
Uvea | Vitreous & Retina | Optic Nerve & Brain | Oculosystemic Disease
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