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Diabetic eye screening: slit lamp examination explained

Updated 27 July 2022

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Female patient being screened by female screener using slit lamp biomicroscopy equipment

Diabetic eye screening test using slit lamp equipment (photo courtesy of British Association of Retinal Screening / Kamran Rajaby)

1. Overview

This leaflet is for people who need to be examined for diabetic eye disease using an instrument called a slit lamp instead of a digital camera.

You need a slit lamp appointment because we could not get a clear view of the back of your eyes using digital photography.

2. Diabetic retinopathy

Illustration showing cross-section of the eye, including pupil, lens, optic nerve, macula and retina

Cross-section of the eye, showing pupil, lens, optic nerve, macula and retina

Diabetic retinopathy occurs when diabetes affects small blood vessels, damaging the part of the eye called the retina. It can cause the blood vessels in the retina to leak or become blocked. This can affect your sight.

3. Importance of screening

Diabetic eye screening helps prevent sight loss. As someone with diabetes, your eyes are at risk of damage from diabetic retinopathy. Screening can detect the condition before you notice any changes to your vision.

Screening is an important part of your diabetes care. Untreated diabetic retinopathy is one of the most common causes of sight loss. When the condition is caught early, treatment can reduce or prevent damage to sight.

Remember, diabetic eye screening is not covered as part of your normal eye examination with an optician. Screening does not look for other eye conditions and you should continue to visit your optician regularly for an eye examination as well.

4. Slit lamp

A slit lamp has 2 parts – a very bright source of light shone through a slit and a microscope. It allows us to look at the individual parts of the eye in detail, in particular the retina at the back of the eye.

This will show whether there are any changes that may have been caused by diabetic retinopathy.

5. The screening test

  1. We put drops in your eyes to temporarily make your pupils larger. You may find the drops sting. They also blur your vision slightly.

  2. We ask you to sit in the examination chair. We ask you to rest your chin and forehead on a support to steady your head. The appointment lasts about 40 minutes.

  3. We send a letter to you and your GP within 6 weeks to let you know your screening results.

6. When screening is offered

We offer screening every 12 months to anyone with diabetes aged 12 and over.

7. Possible side effects

Eye drops may affect your vision for a few hours, so you should not drive after your appointment until your vision returns to normal.

8. Next steps

If you have no changes (or mild diabetic changes) and we are still unlikely to get clear photographs of the back of your eyes we will invite you for another slit lamp appointment in 12 months’ time.

If there are signs of serious changes we will refer you to a specialist eye doctor at your nearest hospital ophthalmology (eye) clinic.

9. Preparing for appointment

To prepare for your appointment you should:

  • bring all the glasses (spectacles) and contact lenses you wear along with lens solution for contacts
  • bring sunglasses as your eyes can feel sensitive after having the eye drops

You may want to bring someone with you to the appointment.

Eye drops may affect your vision for a few hours, so you should not drive after your appointment.

Please tell us if you have had cataracts removed recently or are going to have cataracts removed soon. This may enable us to get a clear view of your eyes using digital photography again.

10. How you can help

You can reduce your risk if you:

  • continue to attend your regular diabetic eye screening appointments
  • keep your blood sugar (HbA1c) at the levels agreed with your health care team
  • see your health care team regularly to check your blood pressure is not raised
  • keep your blood fats (cholesterol) at the levels agreed with your health care team
  • get professional advice if you notice any new problems with your sight
  • eat a healthy, balanced diet
  • lose excess weight if you are overweight
  • take your medication as prescribed
  • exercise regularly
  • cut down or stop smoking if you are a smoker

Remember, you should continue to visit an optician regularly for a normal eye examination as well as attending your diabetic eye screening appointment.

11. More information

You can find more information at:

The NHS screening programmes use personal information from your NHS records to invite you for screening at the right time. NHS England also uses your information to ensure you receive high quality care and to improve the screening programmes. Find out more about how your information is used and protected, and your options.

Find out how to opt out of screening.

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