Eye hospitals’ waiting rooms have a distinct feel to them; they are quieter than most, more concentrated, and the kind of place where people sit motionless and gaze at nothing in particular. It’s hard not to notice, spending time in one, how many of the patients are there because of diabetes. It’s not because of anything they did yesterday, but rather because years of high blood sugar have silently damaged vessels that wind through the delicate tissue at the back of the eye, too small to see and too many to count.
Diabetic retinopathy is the leading cause of sight loss among working-age adults in the UK, and the numbers behind it are difficult to absorb. The risk of blindness is about 25 times higher in people with diabetes than in the general population. Early on, there are frequently no noticeable symptoms, such as microaneurysms, minor bleeding, and mild swelling. It feels good to see. Before it reaches the proliferative stage, when delicate, aberrant new blood vessels begin to form across the retinal surface, the damage nevertheless builds up, sometimes for years. These are unsteady vessels. They bleed. They can cause vitreous haemorrhage, where blood floods the gel-like interior of the eye, and in advanced cases, retinal detachment. The window for intervention, once that stage is reached, is real but finite.
What takes place inside that window is called panretinal photocoagulation, or PRP laser treatment. The procedure works by applying hundreds of small, precisely scattered laser burns to the peripheral areas of the retina, deliberately destroying tissue that has been starved of its normal blood supply. The reasoning is counterintuitive but clinically proven: the central retina, which is in charge of sharp, detailed vision, can be sustained by rerouting the remaining blood flow and lowering the metabolic demands of the outer retina. When the growth-promoting conditions are removed, the aberrant new vessels shrink and leave scars. The chance of bleeding decreases. PRP consistently lowers the risk of severe vision loss by about 50%, which is a significant reduction considering the scope of what it can prevent.
Most patients don’t anticipate the experience of the procedure when they go in. Before a contact lens is put on the eye to precisely focus the laser, the eye is dilated with drops, which takes about two hours, and a topical anesthetic is applied. Then, session by session, the laser works in a dispersed pattern across the peripheral retina; depending on the severity of the condition, each eye typically needs three to four sessions. The duration of each session is approximately fifteen to thirty minutes. Although there is some discomfort, such as a dull ache during and after treatment and sometimes a headache, paracetamol usually takes care of it. Patients are cautioned against driving the same day because the dilating drops cause blurry vision for several hours.
Honest discussion of the trade-off is warranted. PRP does not restore vision already lost to the disease. That’s a point some patients find genuinely difficult to process, arriving with hope for improvement and leaving with the understanding that stabilisation was the goal all along. There is also a real chance that peripheral and night vision reduce after treatment — an effect of the laser burns themselves, necessary but not trivial for people whose driving or work depends on it. Patients receiving treatment in both eyes are required to notify the relevant driving authority. It’s still unclear, for some individuals, exactly how significant those peripheral changes will feel in daily life until the treatment is done.
Watching this field develop over the past decade, with navigated laser systems now able to track eye movements in real time during treatment and newer anti-VEGF injections offering an alternative monthly approach, there’s a sense that PRP is no longer the only option but remains the most durable one — a one-time course of sessions rather than an indefinite monthly commitment. That is more important than it may seem to many patients who are managing diabetes and all of its complications.
