Its difficult for me to accuratley give you information without seeing the MRI images myself - so this information is not specific for your case.
However, if the report is correct, then it sounds like you may have had a 'silent' stroke. Stroke is when there is a lack of blood or oxygen supply to a part of the brain for whatever reason - arterial blockage, a clot etc, and htat part of the brain dies. But if that part of the brain doesn't do much, then you might not notice, and it only comes to attetion when you get a scan for something else!
A stroke in the left occipital region could cause some visual loss in the right field of vision, and the visual feild test should have been done by the ophthalmologist could tell this. THe gyral pattern means that it involves the grey matter of the brain which is atypical for something like MS. However inflamed optic nerves and white matter lesions around the ventricle are - more testing for MS may need to be done to fully exclude.
You should see a neurologist, perhaps one specializing stroke, who can evalaute the scan and try to make a diagnosis. While you may not have the 'usual' risk factors - age, BP etc, there are risk factors that can affect the young for stroke - ie blood clotting, artery tears or narrowings, PFO among some others.
Goodluck