Thyroid Eye Disease
Thyroid problems can cause may eye conditions. Thyroid eye disease leads to marked protrusion of the eyes. This can cause exposure of the corneas, blurred vision, dry eyes and even corneal ulcers. The muscles around the eyes expand and increase the pressure in the socket or orbit. This can raise intraocular pressure and worsen glaucoma. As the muscles get bigger they can push on the optic nerve. This leads to optic nerve damage. Enlarged muscles make it difficult to focus the eyes together. This leads to double vision and also to tracking problems. Finally thyroid problems lead to fat deposition around the eyes. This leads to a cosmetic problem that can only be corrected with surgery..
The foundation of treating thyroid eye disease is the recognition that the reason behind eyes irritation, protrusion and misdirection is the immune system and its relationship to the thyroid. A patient can have low normal or high thyroid levels and still have thyroid eye disease.
The science behind the problem is immunology. Thyroid eye disease is not directly related to hormone levels. It is related to thyroid related immunoglobulins whose receptors sit next to the receptors for thyroid hormones in the tissues around the eyes. When one of these immunoglobulins binds with a receptor, gycosaminogycans can bind to the complex and the tissues begin to swell. The process grows out of control when water binds to the gycosaminoglycans.
The initial treatment of thyroid eye disease is conservative. We ask patients to avoid ceiling fans and bright lights. They hasten the drying process of the cornea leading to tearing and irritation. Wearing a hat with a brim, avoiding direct air conditioning in the car, and using artificial tears are all important measures to combat this problem.
If conservative treatment fails then we consider treatment with medicines, surgery or radiation. Medicines are outstanding in the short run, but have severe long term side effects. Most patients eventually require some type of procedure. We reserve radiation for the most severe cases because it is irreversible and the optic nerve cannot be shielded.
Corticosteroids can temporarily reverse this process by interfering with the immunoglobulins and decreasing swelling. They temporize but do not cure. Long term use of corticosteroids leads to many complications such as aseptic necrosis of the hip, psychosis, hyperglycemia and acne.
There are many surgical procedures designed to help control the changes associated with thyroid eye disease. The key to the surgical management of thyroid eye disease is to first give the eyes more room to move. This requires first decompressing the socket by removing bone and sometimes fat. Second, this requires realigning the eyes so that there is no more double vision for distance vision and for reading. Finally the lids are reconstructed so that they close properly. The lids spread the tear film across the cornea and provide a clear surface for vision
There are several approaches to orbital decompression. The approach depends on which muscle is being restricted the most. The most common approach is external ethmoidectomy and medial orbitotomy. Removing the ethmoid sinuses and medial wall of the eye socket provides the greatest amount of decompression. This can significantly change the amount of double vision and alignment of the eyes. Transconjunctival inferior orbitotomy is best when the inferior rectus muscle is enlarged or there is vertical double vision. There is virtually no scarring. These procedures take less than an hour to perform. We usually monitor the patient overnight for pain and bleeding, and then Dr. McHenry sees you the next day. In some cases a patient requires a lateral orbitotomy. This is a more extensive procedure and allows for the least amount of decompression.
If we determine that the orbital volume is adequate or if we have already decompressed the orbit, the next step is to determine if there is ocular misalignment and if there is double vision. If the double vision cannot be corrected adequately with prisms, then we consider eye muscle surgery. This can be done in an outpatient surgery center with either a local anesthetic with sedation, or under general anesthesia. The double vision is quite different after the surgery, as the muscles become stretched. It takes approximately two weeks to recover. The day after the surgery the patch is removed and temporary prisms , exercises, drops and ointments are started
After ocular alignment is achieved it is then possible to consider the eyelids. The lids should line up with the boarder of the iris. You should not see white above and below the iris. If you do then there is lid retraction. It leads to break up of the tear film and ocular irritation. The lids can be lengthened to correct this problem. It is a day surgery procedure. It is performed under local anesthesia and can be done on both the upper and lower lids.
Finally, extra fat deposits around the eyes can be removed. This can return patients to their normal appearance. Most of these procedures can be performed in the office under local anesthesia. Excess skin can also be removed. As thyroid disease waxes and wanes these procedures can be repeated.