Thyroid Gland Function and the Cornea
An underactive thyroid (also known as hypothyroidism), can have a number of causes: it may be congenital, spontaneous, or an expression of various diseases (such as autoimmune thyroiditis) or can arise as a result of surgery to, or irradiation of, the thyroid gland.
Hypothyroidism has a direct effect on the biomechanics of the cornea. The exact mechanism of action is not yet known. Under certain circumstances, hypothyroidism may affect keratoconus and may be a contra-indication for (reason not perform) perform laser refractive surgery.
In addition, many women have an underactive thyroid during pregnancy.
A connection between hypothyroidism and keratoconus has been suspected for decades:
- In 1936, Appelbaum reported that patients with keratoconus have unusual signs of hypothyroidism.
- In 1953, King showed that keratoconus is common after removal of the thyroid gland.
- In 1999, Kocak described that autoimmune diseases of the thyroid lead to bilateral keratoconus.
Hypothyroidism and corneal topography
A journal article of Prof. Hafezi’s, published in 2014 in the Journal of Refractive Surgery clearly showed the association between hyperthyroidism and changes in corneal topography. Such changes are then accompanied by considerable fluctuations in vision.