Thyroid and the Eye

Thyroid gland, located in front of the neck, is mainly involved in metabolism . If it under functions ( hypo-thyroidism ) the metabolism slows down, causing symptoms like tiredness, skin and hair dryness, low heart rate, weight gain, and the tendency of being physically inactive. Thyroid over function ( hyper-thyroidism) on the other hand gives rise to opposite symptoms like hyperactivity, fast heart beats , weight loss, over sweating, hand tremor, sometimes anxiety, and so on.

The effect of hypo- thyroid in the eye can be cataracts and puffy eyelids.

Hyper-thyroidism is rather complicated in regard to relation of the eye condition to the status of the function of the gland.

Hyper-thyroidism is seen in a disease called Grave’s disease, which is believed to be an auto-immune disease, in the sense that the person’s immune system recognizes the body’s own thyroid tissue as foreign and fights against it. Grave’s disease is about 8 times more common in women as other immune diseases are: Lupus, rheumatoid arthritis, M.S., etc.

Hyper-thyroid eye disease, thyroid eye disease, Grave’s ophthalmopathy, thyroid related orbitopathy, are all terms that have been used for the condition of the eyes that is seen in association with thyroid immune disease. The latter term is the mostly accepted by ophthalmology academic circles for the eye problem in regards to Grave’s disease. The eye condition can occur before or concurrent to the thyroid problem or after thyroid disease has been quiet. It seems that although the basic phenomenon is similar in both thyroid and eye condition, they independently manifest their disease features. Also the eye condition sometimes occurs even when the thyroid tests are normal or subnormal. Due to seriousness of both diseases, a professional communication between endocrinologist, radiologist and ophthalmologist is quite essential in management and control of the diseases.

Thyroid related eye disease effects primarily the eye muscles and the orbit, and due to orbital involvement, secondarily causes protrusion ( exophthalmos) of the eyeball , swelling of the eyelids and compression of the optic nerve. The exophthalmos can be in one orbit or in both. Usually the patients with this disease are 20-40 years of age. Grave’s eye disease which is inflammation of the orbit can occur in relation to thyroid dysfunction.

The eye manifestations of Grave’s eye condition are retraction of the eyelids especially the upper lid which makes the eye look larger , the conjunctiva above the cornea exposed (staring gaze), and in attempt on looking down the upper lid does not drop down as the eyeball itself does (lid lag). There may also be exophthalmos ,double vision, limited eye movements to the sides or up and redness of the conjunctiva due to engorgement of the vessels The muscles of the eye are infiltrated with inflammatory cell and swollen , the orbital tissues edematous and all these causes the orbit being pushed outwards, closure of the lid to cover the cornea harder and optic nerve and its blood supplying vessels under pressure. The corneal exposure and compression of the optic nerve are the important factors to threaten the patient’s vision .If the cornea is not covered by the lids during sleep will get dry and eventually develop ulcer compromising the vision. The intra-ocular pressure also may increase and be checked.

To establish the correct diagnosis, blood tests including thyroid panel , ultra-sound test and CT scan of the orbit, are done. CT scan is in particular good for the diagnosis because it can better demonstrate that the swelling is limited to the bulk of the muscle and the tendons are spared which happens only in Grave’s ophthalmopathy. In unilateral exophthalmos , presence of intra-orbital tumor must be ruled out.

This disease becomes quiet in about few months or years by itself and if the problem is mild no drastic treatment except for moisture drops for the protection of cornea is needed. Frequent eye exams for checking eye pressures, central and peripheral vision , motility of the eye and corneas should be done. But if the disease is active and in full blown state with considerable exophthalmos , double vision , visual disturbance and corneal ulceration is a concern, treatment with high dose steroids ( topical or systemic) or anti-immune medications, radiation , decompression surgery should be started. Radiation due to its side effects is not recommended unless in special cases. The best method of orbital decompression is to remove the medial wall (nasal side ) and floor of the orbit all the swollen muscles and orbital contents have some more room and be released from being compressed . After the condition has been stabilized and no more worsening is happening corrective surgery on the muscales can be carried out.