Hello dear. Thank you for writing us here. The back of the brain is the area for vision perception. A clot would affect it and results into the symptoms which your husband have. The blood collects there and presses that area so he is having trouble in his vision. Certain blood thinners or anti coagulants should be given to treat his condition. A heparin therapy would be prescribed for him but carefully observed because it could could be harmful for people suffering from thrombocytopenia/ hypertension / endocarditis and also if someone is on aspirin therapy. Another alternative treatment is surgical removal of clot where a little hole is made and clot is sucked out of it. But first the medicines would be given. Regards, Dr Gunjan