Background: While pulsed intravenous methylprednisolone (iv-MP) has been shown to be effective and well tolerated in moderate to severe Graves' orbitopathy (GO), limited data are available on dysthyroid optic neuropathy (DON). The objective of this retrospective study was to investigate the efficacy of iv-MP in the treatment of DON and to seek parameters predictive of response.
Methods: Twenty-four DON patients (40 eyes) treated with iv-MP from 2007 to 2012 were included in the study. Concurrent neurological or ophthalmologic diseases or signs of corneal exposure were considered as exclusion criteria. Iv-MP was administered daily for three consecutive days and repeated the following week. At six months, eyes not requiring surgery to preserve visual function were considered as responsive to treatment. Visual acuity, color sensitivity, visual field, and optic discs were analyzed at two and four weeks, and at 3, 6, and 12 months after treatment. Activity of GO was graded using a clinical activity score (CAS). Visual and clinical characteristics of the eyes responsive to iv-MP were studied by comparison to those of nonresponsive eyes.
Results: At six months, 17 of 40 (42.5%) eyes had complete visual recovery and were spared from surgical decompression. At two weeks, visual acuity, color sensitivity, and visual field improved significantly in almost all eyes, but GO inactivated (CAS<4) only in the eyes that permanently responded to iv-MP (p<0.01). The CAS at two weeks was a good predictor of response (cutoff ≥4; 66.7% sensitivity, 76.9% specificity). Optic disc swelling at diagnosis was highly predictive for unresponsiveness to iv-MP (34% sensitivity, 100% specificity). At baseline, high CAS (cutoff >5; 40.2% sensitivity, 94.1% specificity) and severely altered visual field mean defect (cutoff ≤6.31 dB; 73.9% sensitivity, 58.8% specificity) were associated with unresponsiveness to steroids. No major side effects were observed.
Conclusions: High-dose iv-MP was effective in permanently restoring visual function in about 40% of the eyes treated. When successful, it generally induced inactivation of the orbital disease within two weeks and normalization of visual function within one month. The presence of optic disc swelling at diagnosis and persistent active disease at two weeks were good predictors of unresponsiveness to steroids.