Ocular hypertension in patients with active thyroid-associated orbitopathy: a predictor of disease severity, particularly of extraocular muscle enlargement.

The purpose was to ascertain if any relation exists between the elevated intraocular pressure (IOP) in patients with thyroid-associated orbitopathy (TAO) in active stage and the severity of extraocular muscle involvement and the extent of exophthalmos.

Methods: A total of 96 eyes and orbits of 48 adult patients with active TAO were investigated. All patients underwent magnetic resonance imaging of the orbit and measurement of all extraocular recti muscles (EOM). The obtained data was divided into two groups according to the IOP value: normal IOP ≤ 21 mmHg; n = 47 and elevated IOP with IOP > 21 mmHg; n = 49, and analyszed.

Results: A significant difference was found in the short diameter of medial rectus and inferior rectus muscles and in the sum of short parameters of all EOM. All these parameters were significantly higher in the elevated IOP group. Motility restriction in at least one gaze direction was also significantly more frequent (p < 0.0001) in the elevated IOP group. A positive moderate correlation was found between IOP and the sum of short parameters of EOM (r = 0.496). No correlation was found between the IOP and exophthalmos values (r = 0.267). During the follow-up, the frequency of strabismus surgery and orbital decompression was significantly higher in the elevated IOP group (p = 0.003; p = 0.002).

Conclusion: Elevated IOP in the active TAO stage particularly correlates with extraocular muscle involvement. These patients are also more likely to require orbital decompression and strabismus surgery.