We previously reported that
prednisone reduced the frequency of generalized myasthenia (
GMG) and controlled
diplopia without major adverse effects at 2 years in patients with
ocular myasthenia gravis (OMG). Questions remain as to whether study subjects had long-standing disease, biasing results towards a
steroid benefit, and if
prednisone merely delayed
GMG onset. Here, we performed a record review of a referral neuro-ophthalmology service OMG database for patients who were followed-up for > or =4 years or until
GMG developed. We studied the effect of
prednisone on
GMG incidence and control of ocular symptoms. Generally, patients with
diplopia were recommended for
prednisone therapy. Most remained on daily 2.5-10 mg for
diplopia control. We compared the results for
prednisone-treated and "untreated" (
pyridostigmine only) patients. Of 87 patients, 55 were in the
prednisone-treated and 32 were in the untreated groups.
GMG developed in 7 (13%) of the
prednisone-treated (OR 0.41; 95% CI 0.22-0.76) and in 16 (50%) of the untreated (OR 2.78; 95% CI 1.68-4.60) patients. After OMG onset,
GMG developed at a mean 5.8 and 0.22 years in
prednisone and untreated groups.
Diplopia was present at the last exam in 27% of the
prednisone-treated (mean 7.2 years) and in 57% of the untreated (mean 4.6 years) OMG patients. For 48
prednisone-treated patients who did not develop
GMG, OMG treatment failure occurred in 13. Thus,
prednisone delays the onset of
GMG and has sustained benefit in reducing the incidence of
GMG and controlling
diplopia. Without
prednisone,
GMG develops in 50% of OMG patients, typically within 1 year.