Early and late optical coherence tomography (OCT) findings in patients with postoperative hypotony

Purpose: To study early and late findings of macular retinal thickness in patients with hypotony following filtering procedures. Patients and methods: 13 patients who had undergone trabeculectomy (9 with antimetabolites) developed ocular hypotony. The macular region appeared normal during biomicroscopy in 8 patients. In the hypotensive phase, macular thickness was measured using optical coherence tomography (OCT). Directly after attempted and successful normalization of intraocular pressure (7 spontaneous, 5 operative, 1 failure) as well as 6 months later, OCT measurements were repeated. Foveal thickness in the hypotonous eye was correlated with visual acuity and foveal thickness in the fellow eye. Results: Intraocular pressure could be raised from a mean of 2.5+/-1.3 mmHg to 11.5+/-5.5 mmHg and later on to 13+/-3.7 mmHg (follow-up). Mean foveal thickness was reduced from 211+/-73 mu m during hypotony to 170+/-44 mu m after normalization of intraocular pressure and to 171+/-38 mu m at late follow-up. Mean visual acuity improved from 0.17 to 0.33 and finally to 0.6. Conclusions: Despite normal appearance of the macula (8 patients) using biomicroscopy in patients with hypotony, retinal thickness in the fovea is increased. Apart from refractive changes,this retinal thickening can be held responsible for the deterioration of visual acuity in eyes with hypotony. OCT analysis and measurements may be useful to distinguish between retinal thickening that is reversible after normalization of intraocular pressure and cystoid macular edema that leads to permanent visual impairment.