strange optical problem

A friend undertook an eyesight test for a new drivers licence recently, only to discover he could consistently not read the third column (not row) of the test, that is, he could read the other letters in each line but not the third letter going down in each row. Presumably when getting an earlier drivers licence some years ago this problem did not show up. He experiences bipolar disorder but I cannot see how this could account for this. It would seem to have neurological origins. He has never had a stroke, or seizure to my knowledge, but has experienced panic attacks, and has a long history of cannibas use as self-medication, but nothing else particularly in the way of other drug use. He has  sustained some head injuries earlier in his life, including from boxing, but has never been hospitalised to my knowledge. He does not wear glasses or have a history of eyesight problems.

[DrNoopurMD]

Hi,

How are you?
It is indeed a very unusual problem and could be the result of previous head injuries due to which he has sustained some form of injury to the visual center and cannabis abuse. It is difficult to give a straightforward answer. I would suggest you to get him evaluated by a neuro-opthalmologist.
Take care!