There are a number of non-diabetic eye conditions which may be picked up at screening and referred to the hospital eye service. For example, at a first screening, it could be a naevus (the equivalent of a mole in the retina) which might be photographed and monitored. Patients over the age of 50-60 might be referred for wet AMD or glaucoma or a blocked blood vessel. There are many other conditions, some requiring urgent referral (within 2 weeks) and others a routine referral (within 3 or 4 months). It is quite likely that your GP has been told the reason for referral so it is worth asking them.