Hello Sir My Husband Is Sufferd From Blurr Vision From

Hello sir
My husband is sufferd from blurr vision from last 3 months some time headache and nausea will also occur we have concert with physician ophthalmologist and neurologist they said there is no eye problem all the blood and urine test are negative we have also done a mri of brain the report is nagative now we realy dont know what is the cause of this problum