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What is Most common ocular movement affected in thyroid ophthalmopathy? and explain in detail?
Ans. is 'c' i.e., Elevation Most commonly muscles involved in thyroid ophthalmopathy is inferior rectus, which becomes fibrotic and thickened. Thus, eyeball is depressed and elevation is not possible. Thyroid ophthalmopathy Thyroid ophthalmopathy, also called thyroid orbitopathy, is a disease of the orbit seen in Graves disease (thyrotoxicosis), therefore also called Graves ophthalmopathy. However it may also occur rarely in Euthyroid person, primary hypehyroidism and Hashimoto's thyroiditis. Thyroid ophthalmopathy is characterized by enlargement of ocular fat and enlargement of extraocular muscles(PG'") due to deposition of mucopolysaccharides. Clinical features are :- The most common and earliest symptom is upper eyelid retraction. Exophthalmos (Proptosis) Proptosis is the second most common symptom.Thyroid ophthalmopathy is the most common cause of proptosis, whether unilateral or bilateral in adults. Proptosis may be :- i) Mild exophthalmos :- In hypehyroidis (thyrotoxicosis, Graves disease) Extreme exophthalmos :- In hypothyroidism' Restrictive extraocular myopathy :- Enlargement of extraocular muscle without enlargement of tendon is the hallmark of thyroid ophthalmopathy. This distribution of extraocular muscle swelling is typical of thyroid ophthalmopathy. The extraocular muscles involvement in order of decreasing frequency is : Inferior rectus (most commonly involved)> Medial rectus > Superior rectus< Lateral rectus< obliques. It is woh noting that this is restrictive myopathy and the muscle becomes thickened & scarred with detion of eye towards the direction of action of muscle and there is restriction of movement in the direction opposite to the action of the involved muscle, though the opposite muscle is normal. For example in medial rectus involvement eye may be deted medial and abduction will be restricted though the lateral rectus is normal External ophthalmoplegia :- Thyroid ophthalmopathy can cause veical diplopia due to paralysis of veical acting muscles like inferior oblique.