I'm suffering from visual field loss due to small lesion in pulvinar. is this curable?

Maybe: If the lesion is a tumor and compressive, treatment which shrinks the lesion may reduce the visual changes. If the lesion is due to blockage of a blood vessel (stroke) the visual changes are generally permanent. Best to get a baseline visual field test prior to treatment and subsequently to monitor your progress.

Pulvinar: Depends. If the lesion can be treated and eliminated without damaging surrounding structures, then perhaps yes. In general, when a brain tumor or lesion is removed, the vision may recover fully if the lesion is dealt with in a timely manner and if the surrounding pathways have not suffered permanent damage.