hey buddy, sorry to her about the gf's probs... but I bet she don't let em get her down.
right to your question:
her eye - it depends on the classification of the visual difficulties. if it is registered as (DVLA wording) "disorders producing field defect including partial or complete homonymous hemianopia/quadrantanopia or complete bitemporal hemianopia, retinitis pigmentosa, bilateral glaucoma, bilateral retinopathy" driving must stop unless she can meet the national guidelines for field of vision testing.
Waffle clear up time:
homonymous hemianopia - partial blindness affecting both eyes, ie. left sided vision loss in both eyes
homonymous quadrantanopia - same as above, but affects top or bottom field of vision
bitemporal hemianopia - vision loss to left and right fields of vision in both eyes, ie.
left eye:left sided vision loss
right eye:right sided vision loss
retinitis pigmentosa - tunnel vision
= can only see things directly infront
bilateral retinopathy - damage to the retina of both eyes (not caused by inflammation), most common cause is the blood supply to the eye
Going by them (and what u've said) she has none of the above. The only problem is when it comes to MONOCULAR VISION, which is where someone has lost the sight in one eye. They could be difficult with this one (only if they change their guidelines that is), but as it stands any form of light perception in the affected eye is not classified as the above problem..... so she's sorted (ATM).
Arthritis only has to be registered if severe under Permanent Limb Disabilities/Spinal Disabilities.
Sciatica is never mentioned in the guidelines, so no hassles there.
As for the insurance side.... well technically the conditions affecting here eye do not have to be disclosed to the DVLA, therefore no impositions or insurance bump up's should be enforced, but I would inform them (just to cover your own back) incase something did happen, then they could reduce liability/payout due to not being informed.
Hope I've been of some help