8 October 2020

World Sight Day: Focus on Age-Related Macular Degeneration

 

Today, Thursday 8th October, is World Sight Day. To mark this, Porterhouse Medical Group is raising awareness for Age-Related Macular Degeneration (AMD), one of the most common causes of vision loss in adults.

What is AMD

AMD is a condition that affects the macula, a small structure at the back of the eye. The macula is responsible for our central vision, most colour vision and resolution of fine details (1). AMD usually affects people over the age of 50, with 1 in 200 suffering from the condition by the age of 60. In the UK more than 600 000 people are affected by AMD, and with an increasingly aging population, the prevalence will continue to rise (1-3).

There are two types of AMD; dry and wet. The dry form is the most common, accounting for about 90% of cases (2). Dry AMD causes progressive vision loss, due to inflammation and death of photoreceptors (specialised cells in the eye that give us colour and night vision) (4, 5). Unfortunately, there is currently no treatment for dry AMD. Wet AMD is a less common, but more aggressive type of the disease which is associated with rapid progression to severe vision loss, sometimes within days (2, 6). A number of people with dry AMD will go on to develop wet AMD (2). Whilst wet AMD causes a more rapid deterioration of vision than dry, there are treatment options for the former. In part, the pathology of wet AMD is mediated by a chemical called VEGF (vascular endothelial growth factor) which causes aberrant development of new blood vessels at the back of the eye (5, 6). These vessels can bleed and leak fluid, thus causing loss of central vision. The standard treatment for wet AMD is injections of so-called anti-VEGF agents that work by inhibiting the formation of these new blood vessels (5).

 Living with AMD

AMD in itself does not cause total blindness, as it doesn’t affect peripheral vision (1). However, loss of central vision heavily impacts on people’s ability to engage in everyday and work-related activities, such as reading, cooking and driving. Along with functional decrease, AMD may also cause emotional distress, as those affected lose the ability to see faces clearly, increasingly become dependent on help for everyday tasks, and many may experience visual hallucinations (1). Such hallucinations are believed to be caused by the brain continuing to process visual information in the absence of actual visual input from the photoreceptors, comparable to “phantom limb syndrome” in which people with an amputated limb continue to feel sensation from it (7).

Common symptoms of AMD are (1, 8);

  • Gaps or dark spots appearing in your central vision
  • Objects seem to change shape, size or colour
  • Colours fade
  • Bright light becomes glaring and uncomfortable
  • Words may disappear while reading
  • Straight lines, like doorframes, appearing distorted or bent

 Taking care of your eyes

Family history of AMD is a strong risk factor for developing the condition, and there is of course little to be done about a genetic predisposition (3). However, there are steps that everyone can take to maintain good eye health and lower their chance of developing AMD (and other eye conditions).

Get regular check-ups

As a general rule most people, even those with perfectly healthy eyes, should attend an eye examination every couple of years (9). AMD, like many conditions affecting the eyes, does not cause pain or discomfort, and by having regular eye checks an optician can detect early signs, even before symptoms of altered vision are evident to the patient (8). Early detection also increases the chances of receiving effective, vision saving treatment (1).

Protect your eyes

Just like your skin, UV rays from the sun can cause damage to your eyes (9). It is therefore important to not only remember the sun lotion, but also protect your eyes by wearing sunglasses with appropriate UV protection. Sunglasses that provide the appropriate level of UV protection carry the European CE mark or British Standard BSEN ISO 12312-1:2013 (9).

Stop smoking

For smokers the risk of developing AMD is up to four times that of non-smokers, and for smokers with a genetic pre-disposition to the condition, the risk  increases to 20 times that of a non-smoker (1, 3).

Maintain a healthy diet

Certain proteins required for macular function are not produced by the body and must be obtained through diet. These proteins are called yellow plant pigments, and they give some foods their colour (10). They can, unsurprisingly, be found in yellow and orange fruits and vegetables, as well as in leafy greens and in eggs (10).

You can learn more about AMD, and how to live with and manage the condition, by visiting the Macular Societies webpage at https://www.macularsociety.org/age-related-macular-degeneration

 

References

  1. Macular Society Guide to AMD Available from: https://www.macularsociety.org/sites/default/files/resource/Macular%20Society%20Guide%20to%20AMD%20accessible%20pdf%20MS002%20JUN17.pdf.
  2. Al-Zamil WM, Yassin SA. Recent developments in age-related macular degeneration: a review. Clinical interventions in aging. 2017;12:1313-30.
  3. Garcia-Layana A, Cabrera-Lopez F, Garcia-Arumi J, Arias-Barquet L, Ruiz-Moreno JM. Early and intermediate age-related macular degeneration: update and clinical review. Clinical interventions in aging. 2017;12:1579-87.
  4. Ophthalmology AAO. Photoreceptors – American Academy of Ophthalmology 2020 [Available from: https://www.aao.org/eye-health/anatomy/photoreceptors.
  5. Hernandez-Zimbron LF, Zamora-Alvarado R, Ochoa-De la Paz L, Velez-Montoya R, Zenteno E, Gulias-Canizo R, et al. Age-Related Macular Degeneration: New Paradigms for Treatment and Management of AMD. Oxidative medicine and cellular longevity. 2018;2018:8374647.
  6. NHS. Age-related macular degeneration (AMD) – Treatments – NHS. 2018.
  7. VisionAware. Charles Bonnet Syndrome – VisionAware. 2020.
  8. NHS. Age-related macular degeneration (AMD) – symptoms – NHS 2018.
  9. NHS. Look after your eyes-NHS 2018 [Available from: https://www.nhs.uk/live-well/healthy-body/look-after-your-eyes/.
  10. MacularSociety. Accessible Nutrition2017. Available from: https://www.macularsociety.org/sites/default/files/downloads/Accessible%20Nutrition%20JAN17.pdf.

 

Author: Sarah Brun Bar-Yaacov, Medical Writer, Porterhouse Medical Group