Overview

Diabetic retinopathy is one of the leading causes of preventable sight loss in working-age adults worldwide. Around a third of people with diabetes develop it at some point. The problem is that it causes no symptoms until it is advanced enough to be considerably harder to treat. Annual retinal screening exists specifically to close that gap, detecting damage that is present before the patient is aware of anything.

What Is Happening in the Retina

Chronically elevated blood glucose damages the small blood vessels throughout the body. The retina, which has one of the highest metabolic demands of any tissue, is particularly vulnerable. Early damage makes retinal vessels fragile and leaky, this leakage causes macular oedema, swelling of the central retina that affects reading and fine vision. Later changes stimulate the growth of abnormal new blood vessels that bleed easily and can cause rapid, severe vision loss or tractional retinal detachment if untreated.

The correlation between long-term blood glucose control (measured as HbA1c) and retinopathy development is one of the clearest dose-response relationships in diabetes complications research. Better glucose control substantially reduces both the rate of development and the speed of progression. Blood pressure control matters equally. These are not marginal effects, the differences between good and poor control are large and well-documented across multiple major trials.

How Retinal Screening Works

Diabetic eye screening uses digital retinal photography. A photograph of each retina is taken and reviewed by a trained grader, often with software assistance. Results are typically reported within a few weeks. The categories vary by country and screening programme, but broadly: no retinopathy, background retinopathy (monitored, not treated), or referable changes requiring ophthalmology assessment.

Most people with well-controlled diabetes attending regular screening have background changes at most, or none at all. A referral to ophthalmology does not necessarily mean treatment is needed immediately, it means the findings require a more detailed assessment than screening photography alone provides.

If macular oedema is detected, treatment is now primarily anti-VEGF injections, which are effective at preserving and often improving central vision. For more detail on what that treatment involves, the guide to your first eye injection walks through the procedure step by step.

What Happens If Retinopathy Is Found Early

Background retinopathy, a few microaneurysms or small haemorrhages, is monitored, not treated. It does not by itself threaten vision, and for many people with good systemic control it progresses slowly or not at all.

The cases where early detection makes a decisive difference are macular oedema and proliferative retinopathy (abnormal new vessel growth). Both are treated effectively when caught before significant vision loss, and much more difficult to manage after the vision has already changed. This is precisely why regular screening has value that a routine eye test does not replicate. A standard visual acuity check tells you nothing about the retinal changes that have been building for months.

If you notice any change in vision between screening appointments, blurring, new floaters, or an area that seems missing, do not wait for the next scheduled screening. See the guidance on which eye symptoms need urgent attention.

When to Contact Your Eye Doctor

• Any visual change between screening appointments: blurring, new floaters, or a shadow in your field of vision
• A referable screening result with no follow-up appointment yet scheduled
• More than 15 months have passed since your last screening without a new invitation

Questions People Ask

• My vision feels completely normal. Why does screening matter?
  Early and intermediate diabetic retinopathy produces no symptoms. Normal vision at any given moment does not rule out significant retinal change. The entire point of population screening is to detect disease in the window before symptoms appear, when treatment is most effective.
• I have only had diabetes for two years. Do I really need annual screening?
  Yes. Guidelines recommend annual screening from the point of diagnosis, because the duration of subclinical hyperglycaemia before formal diagnosis is unknown. The disease may have been developing for some time before it was detected.
• Does it matter if my blood glucose is poorly controlled right now?
  Your current glucose level does not affect whether screening is worthwhile, the appointment shows what is happening in the retina at this moment regardless of current control. A screening result showing early change can itself be a powerful motivation to improve control. Do not skip the appointment on that basis.
• My result said I have background retinopathy. Does that mean I am going blind?
  No. Background retinopathy refers to early, mild changes that are monitored. The majority of people with background changes do not progress to sight-threatening disease, particularly with reasonable systemic control. The finding is a signal to take blood glucose and blood pressure management seriously, not a prediction of blindness.
• Can my optometrist substitute for the formal diabetic screening programme?
  Optometric retinal photography can detect gross changes, but it is not equivalent to a formally quality-assured diabetic screening programme with standardised protocols and defined referral pathways. They address different purposes and are not interchangeable for people with diabetes.

This page is for general educational information. If you have questions about your screening result, speak with your GP or ophthalmologist. Further reading: Diabetic retinopathy conditions overview, American Academy of Ophthalmology on diabetic retinopathy and WHO global overview of diabetes and its complications.