Can I clarify? Is it that he doesn’t have sight in the left eye, but has full vision including a full visual field in the right? Or, does he have homonymous hemianopia where part of the visual field is missing in the left and right? If his vision is unaffected in one eye he may be able to apply for an exceptional case provisional disability licence and assessment. Hemanopia can be a bit more difficult. He will need supporting written evidence from a medical professional,
case for a disability