1. Dysthyroid eye disease
PATHOGENESIS :
infiltration of the extraocular muscles with lymphocytes and the deposition of glycosaminoglycans.
SYMPTOMS AND SIGNS
The patient may sometimes complain of:
A red painful eye (associated with exposure caused by proptosis
Double vision.
Reduced visual acuity (sometimes associated with optic neuropathy).

2. On examination:
There may be proptosis of the eye (the eye protrudes from the orbit, also termed exophthalmos).
The eye may be chemosed and injected over the muscle insertions.
The upper lid may be retracted
The upper lid may lag behind the movement of the globe on downgaze (lid lag).
There may be restricted eye movements or squint (also termed restrictive thyroid myopathy,
The inferior rectus is the most commonly affected muscle. Involvement of the medial rectus causes mechanical limitation of abduction thereby mimicking a sixth nerve palsy.

3. A CT or MRI scan shows enlargement of the muscles.

4. Dysthyroid eye disease is associated with two serious acute complications:
1- Exposure keratopathy, and corneal ulcers due to proptosis and failure of the lids to protect the cornea. The condition may lead to corneal perforation.
2 Compressive optic neuropathy due to compression and ischaemia of the optic nerve by the thickened muscles. This leads to field loss and may cause blindness.

5. Myasthenia gravis PATHOGENESIS
development of antibodies to the acetylcholine receptors of striated muscle. It affects females more than males and although commonest in the 15–50 age group may affect young children and older adults. Some 40% of patients may show involvement of the extraocular muscles only.
SYMPTOMS AND SIGNS
The extraocular muscles fatigue resulting in a variable diplopia.
A variable ptosis may also be present.
There may be evidence of systemic muscle weakness.

6. TREATMENT
The diagnosis can be confirmed by electromyography or by determining whether an injection of neostigmine or edrophonium (cholinesterase antagonists) temporarily restores normal muscle movement. This test must be performed under close medical supervision with resuscitation equipment and atropine to hand because of the possibility of cholinergic side effects such as bradycardia and bronchospasm.
Patients are treated, in collaboration with a neurologist, with neostigmine or pyridostigmine. Systemic steroids and surgical removal of the thymus also have a role in treatment.