Hi, I am Dr.Richa. I am.a strabismologist.I understand your concern. Double vision can be because of many reasons but as you have mentioned specifically that your double vision is only with both eyes open, it is not because of cataract. Your double vision is binocular that means because of in-coordination between two eye movements. It happens mostly because muscle weakness or paralysis. Some times problem resolves by itself but sometimes it needs treatment in form of eye muscle surgery depending upon duration of your ailment. Till the treatment is planned. therapy in form of prisms can help you see single. Pituitary tumour will have more effect on field of vision rather than causing double vision. I would advise you to visit an ophthalmologist to be specific squint specialist or an ocular neurologist. Don t worry about pituitary tumour but specialist will get an MRI done to rule out any other lesion( if it is there). You have not mentioned your age, any other problem like diabetes or blood pressure and since how long you have this problem. That would have helped to point out the reason, Please visit an ophthalmologist to get a detailed check up. All the best.