Brief Answer:
A step by step approach needs to be taken
Detailed Answer:
Thanks for using the Ask a Doctor service.
The situation is indeed concerning. A step by step approach needs to be taken. The first step is to visit an ophthalmologist and get a fundal examination done. It will provide valuable clues to the probable pathology including retinal problems. The next step would be to get a VEP (Visual evoked potential) done. It will help in evaluating the probable neurological problems including those in the optic nerve and brain. Neurological causes like multiple sclerosis also need to be considered.
Please update me after these and I will guide you accordingly.
Regards