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The Pocklington Trust - The main causes of visual impairment and how these affect people.

There are many different sight conditions however the most common in the UK today are:

  • Cataracts
  • Diabetic Retinopathy
  • Retinitis Pigmentosa
  • Hemianopia
  • Age-related Macular Degeneration
  • Glaucoma

Levels of visual impairment vary from person to person, can deteriorate over time and in some cases can even fluctuate throughout the day.


A cataract is a clouding of the lens in your eye which sits just behind your iris (the coloured part of your eye)

Normally your lens is clear and helps to focus the light entering your eye. Developing cataracts will cause your sight to become cloudy and misty. This usually affects both eyes but can affect just one.

Developing cataracts is most commonly a result of growing older - most people start to develop cataracts after the age of 65 however people in their 40’s/50’s can also develop them.

Cataracts normally develop slowly. As they worsen, symptoms include:

  • You feel like your glasses are dirty and need cleaning, even when they don’t.
  • Your sight is misty and cloudy.
  • You’re more sensitive to light – bright sunlight or car headlamps may glare more.

There’s nothing you can do to stop cataracts from developing or getting worse, but they can be treated by surgery. 

Diabetic Retinopathy

Type 1 and Type 2 Diabetes are long term health conditions that can affect vision in different ways. The most common cause of sight loss in those with diabetes is diabetic retinopathy which occurs as  a result of damage to the network of blood vessels supplying the retina at the back of the eye.

It can affect anybody with any type of diabetes at any age.

Diabetes can cause blood vessels to become blocked, leak or to grow incorrectly therefore reducing overall blood supply to the retina.

The body tries to fix this by growing new blood vessels but unfortunately, these new vessels are weak, and bleed very easily, which affects vision.

This usually result in the blurring of vision, ‘blind spots’ or ‘floaters’ appearing on certain parts of the retina.

Different forms of laser treatment can be used depending upon how much of the retina is affected.

Retinitis Pigmentosa

Retinitis Pigmentosa (RP) is the name given to a group of inherited eye conditions called retinal dystrophies.

RP affects the retina at the back of the eye and, over time, stops it from working, causing gradual but permanent changes that reduce vision depending on age and the type of RP someone has.

RP is a progressive condition. Sight will worsen over time. These changes in sight can happen gradually or suddenly over a short period of time. As RP progresses it leaves a central narrow field of vision. This is often referred to as “tunnel vision”.

Currently there is no cure or treatment which can slow down or stop RP from getting worse.


Hemianopia can be caused by brain trauma, the most common of which is related to stroke.  Damage to the visual pathways connecting the brain and the eye causes the loss of one half of the visual field.

Hemianopia can result in someone being unable to see to either the left or right from the centre of their field of vision in both eyes. The extent of sight loss varies from person to person and depends on the area of the brain that has been affected by the stroke.

Strokes are most common in people aged over 65 but around a quarter of people who have a stroke are of working age. Increased risk factors include:

  • People of African, Caribbean and South Asian descent.
  • A family history of stroke.
  • Lifestyle choices including smoking and drinking alcohol.
  • Other medical conditions such as diabetes and high blood pressure.

Treatment of Hemianopia tends to take the form of rehabilitation and training, to help make the most of the remaining vision, rather than surgery or medication.

Age-related Macular Degeneration

Age related macular degeneration (AMD) is a form of macular dystrophy. When someone develops AMD, their cone cells in the macular become damaged and stop working as they should. Macular degeneration is most typically associated with ageing and is most common in those over 65. 

There are two main types of AMD – “wet” and dry. Wet AMD causes sight loss more rapidly than the more common “dry” AMD.  It usually affects both eyes though not always at the same time.

AMD does not cause complete loss of sight. It affects the central vision, which can become distorted or blurry.  Eventually a blank patch may appear.  Everyone can have slightly different symptoms, but typically the first thing people notice is greater difficulty seeing detail. Straight lines may start to look distorted, wavy or bumpy. They may also have increased sensitivity to bright light.

There is no treatment for dry AMD. But there is some evidence of certain vitamins and minerals helping to slow its progression. Treatment is available for wet AMD using medication which minimises further damage to sight.


If the pressure is too high in a person’s eye, it can cause the optic nerve to become damaged at the point where it leaves the eye. This damage is called glaucoma. It can occur at any age but is more common as people get older.

A person is at a higher risk of developing some form of glaucoma if:

  • They have a close blood relative such as a parent who has it, or
  • They are black or from an East Asian ethnic background.

Glaucoma affects the side vision first and, if untreated, can result in a narrowing of the visual field or blind spots forming on the outer edges of sight. It produces misty or blurry patches in the vision, or missing details such as objects and people around the periphery.

In more severe cases central vision can be affected too.  This causes blind spots to appear when looking straight ahead which makes it harder to recognise faces, watch TV or read a newspaper.

Vision lost due to glaucoma cannot be restored. But, once diagnosed, it is possible for further deterioration to be prevented. Most commonly this is through the long-term use of eye drops and less commonly through laser treatment and surgery.


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