They are all reversible on stopping treatment and none has yet been known to cause serious or permanent visual defect. Should these types of corneal changes occur with Plaquenil, it should be either stopped or temporarily withdrawn. Reversible extra-ocular muscle palsies and temporary blurring of vision due to interference with accommodation have also been noted. Early retinal changes are asymptomatic, but may progress later to cause central and peripheral scotoma with field defects. Originally, the condition was thought to be progressive and irreversible but more recent evidence suggests that routine ophthalmological examinations may detect retinal changes, especially pigmentation, at an early and reversible stage when there is no apparent visual disturbance.
Much evidence suggests that there is a threshold of dosage above which retinopathy appears.
These results seem to correlate more with daily dosage than with a cumulative dose, although the risk increases with increased duration of treatment. It is recommended that all patients have an initial ophthalmological examination, repeated at six-month intervals during therapy. This should include slit-lamp microscopy, fundus and visual field studies. Four to twelve week's therapy is required before the effect of treatment can be evaluated. If the response is good, the dose can be reduced to 200 - 400 mg daily.