Optical coherence tomography measurements in compressive optic neuropathy associated with dysthyroid orbitopathy

The purpose of the study was to assess the influence of optic nerve compression on the peripapillary retinal nerve fiber layer (RNFL) thickness in eyes with acute and chronic dysthyroid optic neuropathy (DON). Patients with DON and healthy control subjects underwent peripapillary optical coherence tomography (OCT) scanning with the Cirrus HD-OCT. Patients were classified as acute (within 6 months from the onset of DON) versus chronic (6 months or more from the onset of DON) DON. The thickness of peripapillary RNFL was compared between eyes with acute and chronic DON and control eyes. Baseline factors associated with visual acuity at the last visit were also analyzed. The mean temporal peripapillary RNFL thickness was thinnest in chronic DON at 66 +/- 12 mu m compared to 76 +/- 8 mu m in eyes with acute DON and 73 +/- 12 mu m in control eyes (p = 0.014). In a multivariable analysis, patients with greater inferior peripapillary RNFL thickness and younger age tended to have better visual acuity at the last visit (p = 0.034, odds ratio [OR] = 1.038 and p = 0.007, OR = 0.912, respectively). Our data revealed a notable difference in temporal peripapillary RNFL thickness in eyes with chronic DON compared to eyes with acute DON and control eyes. We also found a significant association between inferior peripapillary RNFL thickness and visual acuity at the last visit. Thicker inferior peripapillary RNFL thickness was associated with better visual outcome. Further studies with large sample sizes using a prospective design should more clearly reveal the time aspect of the association between the onset of DON and the changes in peripapillary RNFL, and their clinical significance.