DECREASE IN INTRAOCULAR-PRESSURE AFTER ORBITAL DECOMPRESSION FOR THYROID ORBITOPATHY

Background: The effect of thyroid orbitopathy on intraocular pressure (IOP) remains controversial. We carried out a study to determine the e ffect of orbital decompression surgery on the IOP in patients with adv anced thyroid orbitopathy. Methods: The records of 12 consecutive pati ents (22 eyes) who underwent decompression surgery for severe thyroid orbitopathy between 1985 and 1996 were reviewed. All patients were mai ntained on essentially the same medications before and after surgery. The IOP readings, obtained by means of applanation tonometry in primar y gaze, from the pre- and postoperative visits were recorded, and the net change was calculated. Results: The mean preoperative and postoper ative IOP values were 19.8 mm Hg and 16.8 mm Hg respectively, a signif icant difference (p = 0.008). Seven of eight eyes with an IOP of 21 mm Hg or greater preoperatively had a postoperative IOP less than 21 mm Hg; these eyes showed a mean decrease in IOP of 5.6 mm Hg. The degree of preoperative IOP elevation was found to be a strong predictor of th e amount of IOP lowering after surgery (p = 0.014). Interpretation: Ou r results support the concept that orbital congestion associated with thyroid orbitopathy produces an increase in IOP by elevation of episcl eral venous pressure (EVP) and that orbital decompression may reduce t he IOP by decreasing EVP. Decompression surgery may obviate the need f or more aggressive management of glaucoma in patients with severe thyr oid orbitopathy.