Thank you Hatch! Had a follow up visit to the eye specialist yesterday. So the good news is that the detached retina appears to have reattached itself! The inflammation behind the one eye (cause still unknown) has reduced dramatically/gone but they were unsure if this was in response to the steroids or antibiotics. There is some light perception in both eyes, but it varies from eye to eye and is not consistent in either eye, so each will react independently and not all the time! This is also baffling the vets as they don't think it is a retina issue, but are unsure if it is an optic nerve issue or a brain issue! The left eye reacted well in the vets to a bright light, but not the right. A day earlier, the right eye reacted in sunlight but not the left! They think he can perceive the difference between bright light and deep shade but no fine detail or small objects. They are tailing off the steroids gradually and giving him another course of the antibiotics to make sure every base is covered and then we wait to see what happens. It will depend on how much damage has been done to the optic nerve as the retinas should be allowing some sight. Nothing really tallies with all the symptoms or responses to the meds. If it was a tumour in the brain or on the optic nerve, it wouldn't have reacted to the meds as favourably as it has. A tumour would also have other physical symptoms such as loss of co-ordination, head tilt, fits etc, which he doesn't have. If it was a foreign body behind one eye, then the other eye should have been OK. If he had just run into something hard then the delay in sight loss doesn't make sense and the meds wouldn't really have had any effect. If it was a toxin (such as eating sheep poo from sheep recently treated with Ivomectin etc) then he should have had other symptoms as well, which he didn't.....
He still seems slightly puzzled, but he has mastered most of the house including the stairs, and he is still walking off the lead, even in unknown areas but just checking back in when he is unsure, and we have to do some of his 'seeing' for him such as fences etc. He runs, hunts etc almost as fast as he used to but stays closer, and a pair of specialist goggles (courtesy of a police dog handler - they have badly scratched lenses so he was going to throw them away, but that doesn't matter for our dog as he can't see anyway) protect his eyes from scratches from brambles or twigs, and we will see how he copes back in the beating line on Saturday! We are starting to get our heads around it, as it is sad to see his confidence knocked back, but he seems to be quickly regaining that, and as the vet pointed out, it is less of an issue for a dog than a human as sight isn't their primary sense so his other senses are all stepping up and helping to balance out.
Will keep you informed. Thank you everyone for all your support!