In my experience, weakness of medial eye movement along the horizontal plane is equally as common. The natural history of ocular myasthenia has been well studied. Most of the worsening seemed to occur during the first 3-5 years of illness during which time the incidence of a severe exacerbation is highest. The salient symptoms of ocular MG,double vision and droopiness of one or both lids, are frequently influenced by environmental, emotional and physical factors. Bright sunlight, emotional stress, viral illness, surgery, menstruation, pregnancy, immunizations and other physical factors all may precipitate a change in the expression of ocular MG, although not in a predictable direction.
Spontaneous remissions can occur in any patient and sometimes persist for years.
Fortunately MG only rarely follows an acutely or chronically progressive course. Age, sex and pattern of onset are not used to predict the eventual course of the disease. It used to be felt that MG has no racial or geographic predilection. In ocular MG, equal numbers of males and females are affected, the Chinese race has an unusually high incidence, and patients with ocular MG often have abnormal levels of autoantibodies against the thyroid gland and show concomitant disorders of thyroid function. Victims of generalized MG, in contrast, are more commonly female, ethnically more likely to be Italian and show much fewer abnormalities of thyroid function.