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What is the function of the retina?

eye examination at the ophthalmologists

The retina is the light-sensitive tissue in the back of the eye which contains specialised cells called photoreceptors. These cells are responsible for covering converting light rays to electrical impulses so that our brain can interpret what we see every day. These light rays focus on the retina as they travel through the cornea, pupil and the lens

What is the macula?

This part of the retina is only half a millimetre in size but is packed with a high concentration of specialised photoreceptors and is responsible for the whole of the central vision, most of our colour vision and fine detail of images.

the eye

What symptoms are associated with retinal disorders?

The most common symptoms include:

  • Decrease in central vision
  • Loss of vision
  • Floaters and cobwebs (which are more apparent when looking at a white background)
  • Flashing lights
  • Objects appearing smaller or larger than they truly are
  • Decrease in peripheral vision or presence of shadows#
  • Distortion of straight lines

How is the retina assessed?

We start by taking a detailed history from the patient to understand their symptoms. The surgeon will then use a slit lamp to examine the eye. We use a non-invasive scanner called Optical Coherence Tomography (OCT) which gives us detailed information about the structure of the retina.

Occasionally a dye test called fluorescein angiography/ICG may be needed to assess the retinal structures in more detail and in a more dynamic way. A visual field test is another diagnostic examination we can use to provide information about the function of the retina. On occasion, more specialised tests e.g electrodiagnostics may be needed in certain cases.


What are the main blinding retinal conditions?

This list is not exhaustive but the top conditions which account for the majority of vision impairment and blindness in the UK include:

Wet age-related macular degeneration:

This condition starts with a sudden blurring of central vision and distortion which is painless and progressive. Abnormal blood vessels from the layer beneath the retina, choroid, damage the photoreceptors. This condition needs urgent attention to avoid irreversible loss of vision and is the most common cause of blindness in the UK.

Diabetic retinopathy:

In diabetes very small blood vessels within the retina get damaged and leak fluid causing swelling of the retina, displacing the photoreceptors resulting in distortion. With advancing disease abnormal blood vessels can develop and bleed, causing floaters and vision loss. These symptoms require urgent attention to limit any damage. DR is the most common cause of blindness in the working population.

Retinal vein occlusion:

This condition refers to blockage of the main trunk or smaller contributories of the retinal veins that drain the blood from the retina. Vein occlusion can result in central blurring or loss of vision through fluid accumulation in the macula and sheer force of the blockage causing damage to the photoreceptors. In branch vein occlusions, if the central part of the retina is spared, vision blurring occurs just off centre and can be peripheral.

Myopic choroidal neovascularisation:

In patients with high degrees of short-sightedness, the eyeball and the retina are stretched over an abnormally large area. As a result the barrier separating the retina from the abnormal blood vessels beneath in the choroid becomes susceptible to damage. Once abnormal blood vessels grow into the retina, the photoreceptors can get damaged and the patient develops symptoms of vision loss and distortion in their central vision.

What other retina conditions are seen in the clinic?

We advise that if you have any of the following symptoms, you are seen by a clinician in the clinic so that a diagnosis can be made.

Posterior vitreous detachment

If you get onset of flashing lights and floaters. The symptoms tend to resolve on their own but we would need to exclude a retinal tear or detachment as if these were present they would require urgent treatment. Occasionally floaters persist and treatment options are available to manage this after discussion with the clinician.

Central serous retinopathy

This condition occurs as a result of fluid build-up in the macula from the layer beneath the retina known as choroid. You would normally your vision is distorted and dimming of your central vision. Most cases spontaneously resolve but can be chronic and may need treatment.

Vitreomacular traction and macular holes

Disorders affecting traction on the retinal surface by the vitreous body is often found incidentally but as the condition advances, distortion can occur. Macular hole (MH) formation can result in the loss of central vision and you may see a kink when looking at straight lines. MH often requires surgical management.

Post-operative cystoid macular oedema (CMO)

CMO can occur after a complicated procedure and can also occur in around 2% of patients following routine cataract surgery. This condition is often treated with drops but may need injections around the eye or in the vitreous cavity to manage the swelling in the macula.

Treatment of retinal disorders

Please read our retinal disorder procedure page for the different treatments and surgeries available for treating retinal disorders.