Flashes and floaters typically indicate posterior vitreous detachment; flashes are caused by the shrinking vitreous tugging on the retina, and floaters can be due to blood, inflammatory debris, or condensations (thickened strands) of the vitreous humour. Risk factors for posterior vitreous detachment include short-sightedness, blunt trauma, and a history of cataract surgery.
Check vision, assess visual field (ideally with a red hatpin), and compare red reflexes at ophthalmoscopy; asymmetrical red reflexes may be due to posterior haemorrhage or retinal detachment. Weiss rings are prominent circular vitreous condensations near the optic nerve which are pathognomonic of posterior vitreous detachment.
Local guidelines on referral should be followed, but, if there aren’t any (which, in this area, there aren’t to my knowledge), aiming to get the patient seen within two weeks is a good guideline.