Age-related Macular Degeneration

Age-related Macular Degeneration is a chronic and progressive retinal condition which occurs due to degeneration of the macula. The macula is at the centre of the retina, the light-sensitive neural tissue layer which lines the back of the eye, and is responsible for sharp central vision, as well as for normal daily tasks, such as reading and driving.

The retina contains rod and cone photoreceptor cells, which sense incoming light from the cornea. The cone cells are most densely populated at the centre of the retina in the macula, responding to bright light (photopic vision) and important for central vision, while the rod cells exist primarily along the outer area of the retina to detect dim light (scotopic vision) and assist with peripheral vision.

AMD is the leading cause of vision loss in the ageing population, 50 years and older and is estimated to affect 196 million people worldwide, a figure which is expected to rise to 288 million by 20401.

AMD occurs in two stages; early and late, whereby early AMD is asymptomatic and is detected by a dilated eye exam. This is the only way to definitively diagnose AMD. Late AMD exists in two forms, called neovascular AMD, also known as wet or exudative AMD and dry AMD, commonly known as Geographic Atrophy.

Dry AMD is characterised by progressive loss of photoreceptor cells and retinal pigment epithelium cells, which nourish the retina, as well as loss of underlying blood-vessels within the choroid layer, beneath the retina. The accumulation of fatty deposits called drusen between the RPE cell-layer and Bruch’s membrane affects the RPE cell’s ability to nourish and maintain the cone photoreceptor cells, damaging the macula and ultimately causing a decline in central vision.

Neovascular AMD arises due to choroidal neovascularisation, whereby a substance in the body called vascular endothelial growth factor (VEGF) is overactive and causes immature blood-vessels to grow in the choroid layer, beneath the retina. These blood-vessels subsequently burst and leak blood, fluid and toxins into the RPE cell-layer, which subsequently damages the macula.

Due to the fact that early and intermediate stages of AMD exist largely without any symptoms, it is essential that we have regular eye examinations to detect early stage AMD and avoid late stage AMD .

What are the symptoms of AMD?

Common symptoms of AMD include blurred central vision, blind spots (scotomas) and distorted vision, where straight lines appear wavy. A variety of imaging technologies can be used during dilated eye exams to take photographs of the retina, including fundus photography and optical coherence tomography to detect early stage AMD. Additionally, they can identify the presence of drusen, a characteristic feature of dry AMD or Geographic Atrophy.

It is recommended to get your eyes tested every two years and if 50 years or older, it is important to check your eyes every year as people in this age category are at high-risk of developing AMD. Additionally, you can monitor your eye health and central vision independently, using the Amsler grid. The Amsler grid is a square grid of straight lines and has a central dot which you are to focus your eyes on. If any lines appear wavy or distorted, contact your doctor immediately.

To learn more about the symptoms of AMD and to check your vision using the Amsler grid please visit the AMD resource.

 

What causes AMD?

AMD is a complex condition which is caused by a combination of environmental and genetic risk factors. Age, whereby people over 50 years of age are at significant risk, as well as smoking, poor nutrition, ethnicity (Caucasian) and family history can contribute to a person’s risk of developing AMD.

Neovascular AMD occurs when a substance called vascular endothelial growth factor (VEGF) is over-active, causing immature blood-vessels to grow in the choroid layer, directly beneath the retina. As these blood-vessels are immature, they begin to burst and leak blood, fluid and toxins which damages the retinal cells and macula to cause a decline in central vision.

Genetics is also known to play a role in the development of AMD, with certain identified gene variants associated with neovascular AMD, particularly certain gene variants which impact the complement pathway, a system which regulates inflammation. However, genetic testing is not yet a primary part of the AMD screening process. This is expected to change as our knowledge of the genetic factors involved in AMD improves and is expected to play a key role in managing AMD in the future.

Here is a list of measures to help you maintain healthy vision:

  • Eat a balanced vegetable rich diet.
  • Take regular exercise.
  • Wear good quality sunglasses.
  • Quit smoking.

 

For more detailed information about AMD and the modifiable and non-modifiable risk factors which influence AMD onset, please visit our AMD resource.

What treatments are available?

To date, there are no available therapies or cures for dry AMD, although recent stem-cell research has successfully grown RPE cells from embryonic stem-cells, which were genetically modified using CRISPR/Cas9 gene therapy, to prevent rejection by the body’s immune system2.

With respect to neovascular AMD, surgical intervention was the primary treatment strategy in the past. In more recent years, photodynamic therapy and in particular, anti-VEGF therapy have become the most common and effective therapy options. If neovascular AMD is suspected, you may have a test called fluoroscein angiography. A special dye is injected into your arm and carried through your bloodstream and as it passes through the blood vessels in your eye, doctors can detect blood leaking into the retina. Anti-VEGF agents inhibit VEGF activity to stop blood-vessel growth. Its success in maintaining or restoring some visual acuity is dependent on early detection and treatment before irreversible scarring and damage occurs.

Brolucizumab (Beovu) is the most recent anti-VEGF to receive FDA approval for use in the United States and European Commission for use in the 27 European Union member states, as well as in the UK, Iceland, Norway and Liechtenstein.

For people living with AMD, general eye check-ups are extremely important, because these individuals are still at risk for other kinds of eye problems that can affect the general population and may be treatable. Regular visits to your eye doctor can also make you aware of current advances as we learn more about treating these prevalent diseases.

The ERN-EYE have a number of helpful resources available, such as the video below to communicate how we can best care for people living with retinal conditions and visual impairments when visiting hospitals for check-ups and appointments.

How to welcome visually impaired people to the hospital.

References

1. Wong, W. L. et al. Global prevalence of age-related macular degeneration and disease burden projection for 2020 and 2040: a systematic review and meta-analysis. Lancet Glob. Health2, e106–e116 (2014).

 

2. Reyes, A.P., Petrus-Reurer, S., Sánchez, S.P., Kumar, P., Douagi, I., Bartuma, H., Aronsson, M., Westman, S., Lardner, E., André, H. and Falk, A., 2020. Identification of cell surface markers and establishment of monolayer differentiation to retinal pigment epithelial cells. Nature Communications11(1), pp.1-15.

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