Understanding Blindness
Understanding Blindness

Understanding Blindness

Visual Impairment and blindness can affect a wide spectrum of people across the UK, with roughly two million people living with vision loss. Do you know what the different types of visual impairment are or what causes visual impairment? Read about the eye condition and the range of vision aids available to support anyone with a visual impairment.

Blindness or visual impairment (also known as low vision or partially sighted) is a visual disability that cannot be fully corrected (if at all) with surgical procedures, medical treatments, or prescription lenses (glasses or contact lenses).

Visual Impairment and blindness can affect a wide spectrum of people across the UK, with roughly two million people living with vision loss. Of these, there is around 360,000 registered as blind or partially sighted.

There are various eye conditions or diseases that can lead to sight loss, such as glaucoma and cataracts, however, complete ‘black’ blindness happens in few people - many affected by vision loss still retain some residual vision. Those living with low vision, or varying degrees of legal blindness, usually try to maximise their sight as much as possible with vision aids and practical support.

Types of Visual Impairment

Low Vision & Legal Blindness

There are a few different types of low vision that affect different parts of the eye and their severity will determine whether you are partially sighted or blind. The common low vision ‘types’ are:

  • Loss of central vision – there is a blind spot in the centre of your vision.
  • Loss of peripheral vision – you cannot see anything to either side or above/below eye level. Central vision stays intact.
  • Hazy Vision – your field of vision appears covered with a glare or film.
  • Blurred Vision – objects, near and far, are out of focus.
  • Night Blindness – You are unable to see in low lit places and outside at night. 

A person with low vision whose sight has deteriorated to a certain degree can register their sight loss with the local council, who will help them get support and advice for daily life. Your ophthalmologist can provide you with a Certificate of Vision Impairment (CVI) to allow you to register as sight impaired (partially sighted) or severely sight impaired (blind).

If you choose not to register, you can still get help from social services. 

Sight Impaired

To be able to register as sight impaired, you would usually have one of the below: 

  • A visual acuity between 3/60 & 6/60, with a full field of vision.
  • Cloudy/blurry central vision or a field of vision with ‘moderate’ reduction, with a visual acuity of up to 6/24.
  • A visual acuity of up to 6/18, with a considerable part missing from your field of vision or peripheral vision.

Severely Sight Impaired 

To be able to register as severely sight impaired, you would usually have one of the below:

  • A visual acuity less than 3/60, with a full field of vision.
  • Very reduced vision field (especially in lower part) but with visual acuity of 6/60 & over.
  • Severe reduction of field of vision (e.g. tunnel vision) with a visual acuity between 3/60 & 6/60.

What is Visual Acuity?

Visual acuity is used to measure your central vision, as well as your ability to distinguish details and objects. Someone who has ‘normal’ vision has 6/6 visual acuity – they can see the bottom/second bottom line of a Snellen chart (pictured).

If you have 6/60 visual acuity, it means that you can see at 6 metres. Others with normal acuity can see from 60 metres. The 60 equates to the top line of letters on the Snellen chart, if you have to sit at 3 metres away from the chart to read the top line, this is recorded as 3/60.

Each line of letters goes down in numerical value (distance) until it reaches 6/6 of normal visual acuity. For example, the next line down from 60 might be 36 - someone with 6/6 can read that line at 36 metres away, while someone with 6/36 can only read the line at 6 metres away, and most likely won’t be able to read any of the lines below. 

What is Visual Field?

A visual field refers to the edges of your vision while you are looking ahead. Loss of this visual field can result in tunnel vision or blind spots (scotomas) as your peripheral (side) vision is affected. This can cause problems with depth perception, navigation, and vision in low lighting. 

Signs & Symptoms

The signs and symptoms can present differently for different people, but symptoms can also vary depending on the eye condition that is causing the vision loss or blindness. However, you should visit your optometrist if the following symptoms occur:

  • Slightly washed out colours.
  • Judging the depth of steps becomes difficult.
  • Straight lines appear wobbly.
  • Reading is increasingly difficult.
  • Struggling to see road signs while driving.
  • Blurry vision.
  • Difficulty seeing in low lighting or outside at night.
  • Blurry patch in the middle of your vision.
  • Sight loss to the sides of your vision.

It can be easy to pass these off as signs of ageing, however, this may not be the case, and it’s important to check that your body isn’t telling you that something is wrong.

Adults should visit their opticians once every two years.

Complications of Blindness & Low Vision

Depression & Anxiety

A significant change in your life can always be difficult to come to terms with, but sight loss that can’t be treated can result in a range of emotions, from shock and anger to denial and acceptance.

If you are diagnosed with blindness or visual impairment, your eye doctor may refer you to a low-vision clinic, which can offer you advice and support in understanding your condition and the impact it will have on your life. They can also offer practical advice on vision aids, as well as giving you information on other organisations or charities providing help and support, such as the Royal National Institute of Blind People (RNIB).


Depending on the type of work that you do, your vision impairment may have a significant impact on your day to day job. However, the Access to Work Scheme provides advice and support on what equipment and adjustments will be needed to help you do your job. The scheme can also provide a grant towards the equipment and training you might need, from using a braille keyboard to voice recognition software.

If you are looking for work, you don’t have to tell potential employers about your visual impairment, but it is often recommended that you do. If you would rather try self-employment for the flexibility of being able to work from home, Action for Blind People offer advisors and training on how to get set up. Alternatively, you can learn more about general employment & visual impairment on their site or the RNIB website.

What Causes Blindness?

There are a range of eye conditions and diseases that can cause blindness or visual impairment, and not all of them are a symptom of old age.

Whether you are affected by complete blindness or are visually impaired, the cause is due to a disruption between the eye’s ability to perceive light and translate it into impulses that are sent to the brain. This disruption can be caused by a number of things, but to understand these problems and the associated conditions/diseases, it’s important to understand the basics of how the eye works.

How Your Eye Works: The Basics

There are four main components that help the eye function: 

The Cornea and Lens are found at the front of the eye. They focus light coming into the eye, which allows you to form an image on the retina. 
The Retina is at the back of the eye. It is a layer of tissue that senses light and colour, converting them into electrical signals.
The Optic Nerve transmits electrical signals from the retina to the brain for interpretation. This lets us understand the information sent through from the eye.

The Causes

Blindness or visual impairment occurs when one of these components is affected, damaged, or has degenerated over time.  Whether through illness or injury, the following may occur:

  • A cloudy lens that obscures the light entering the eye.
  • Altered eye shape that changes the image on the retina.
  • Degraded or deteriorated retina.
  • Optic nerve that is damaged, disrupting information flowing to the brain.

There are a few more common causes of visual impairment & blindness, these include:


Cataracts are when the lens begins to become less transparent (see-through), usually as a result of becoming older (over 65) but it can also develop from conditions such as diabetes, or medications such as steroids.

Cataracts can cause eyesight to appear misty or cloudy, and as the cataract gets worse, the cloudier your vision can become. There is an operation available to remove the cloudy lens and replace it with an artificial one, but if you have other eye conditions, or there is a complication with the surgery, your sight may still be affected.


Glaucoma refers to a group of eye conditions that damage your optic nerve, usually due to a build-up of fluid pressure in the eye, often affecting your peripheral vision. Unfortunately Glaucoma is permanent and there isn’t any treatment to restore the sight loss, however, there are preventative methods, such as eye drops, or laser eye surgery to help stop this from happening. 

Uncorrected Refractive Errors

Uncorrected Refractive Errors, such as Myopia (short-sighted), Hyperopia (long-sighted), and Astigmatism, can cause severe visual impairment and blindness, however, this is easily avoidable with corrective lenses (glasses or contact lenses).

A refractive error is when someone cannot focus properly on an object due to the light being refracted onto the wrong spot on the retina. This can be caused by a misshapen eye, cornea, or lens. 

Refractive errors can sometimes go uncorrected due to a lack of awareness (often in children who do not know something is wrong), lack of funds to pay for glasses or appointments, or cultural stigma around wearing glasses (less so in modern culture). It is important that eye tests are done once a year for children and once every two years for adults to ensure that treatment is provided and severe vision loss avoided.

Macular Degeneration

Macular Degeneration is when a small part of the retina (macula) begins to degenerate, affecting your central vision. It often occurs with age (age-related macular degeneration –AMD), and can cause blurriness, or distorted vision when looking ahead (reading or watching TV), which can lead to a ‘blind spot’.

The exact cause is not known, but it has been linked with smoking, sunlight exposure, nutrition - it is thought that making changes to these factors can reduce the risk of developing the condition. There is no cure, but treatments such as anti-VEGF medication, and laser eye surgery can help.

Diabetic Retinopathy

Diabetic Retinopathy  occurs as a complication of diabetes, where the high sugar levels damage the retina. If undiagnosed and untreated, it can lead to blindness as the blood vessels nourishing the retina become damaged – there are three stages of damage. Symptoms don’t usually present themselves early on, but in later stages they can include blurry vision, floating shapes, sudden sight loss, or eye pain.

Preventative measures involve close control of sugar levels, cholesterol, and blood pressure as well as regular screening, while treatments can include medication injections (into the eye), laser eye surgery, or surgery to remove scar tissue or blood (from the eyes).

Other Possible Causes

There are a wide range of conditions or problems that can cause blindness or impairment, some of which can be:

  • Injuries to the eye’s surface (chemical burns).
  • Blocked blood vessels.
  • Complications of premature birth (Retrolental Fibroplasia).
  • Complications of eye surgery.
  • Lazy eye.
  • Optic neuritis.
  • Stroke.
  • Retinitis Pigmentosa.
  • Tumours (such as retinoblastoma and optic glioma).

For a full list of eye conditions that can cause vision loss, visit the RNIB website.

How is a Visual Impairment Diagnosed? 

The diagnosis of blindness or visual impairment very much depends on the condition that is causing the vision loss. However, it is important to have regular eye tests, which can help treat certain eye conditions, or catch them at an earlier stage.

Children should have an eye test once every year, and adults once every two years, unless advised otherwise. If you are having vision problems, such as cloudy or blurry sight, visit an optometrist or ophthalmologist as soon as possible.

Eye Test

An eye test may vary depending on what the optometrist is looking for, and if a certain condition is suspected they may conduct further tests, or refer you for a more in depth exam relating to the condition. However, a standard eye test that can help diagnose your vision loss will usually include:

Family History & Current Symptoms

Your optometrist will usually start by asking about your family history and if you have any symptoms, such as blurry vision, as well as how long you’ve been affected by them. They may also ask about your health, lifestyle, and medication. Medical history, symptoms, or age may result in a few further tests being run, such as checking for glaucoma or diabetic retinopathy.

Eye Exam

You will have your eye examined to check for any underlying problems, this will involve a light being shone through your pupil to check the inside of your eye as well as your pupil’s reflexes. You will also have your eye movements and co-ordination (to ensure your eyes are synchronised) checked.

Visual Acuity Test

As mentioned above, a visual acuity test allows the optometrist to analyse the extent of your visual impairment. Using a Snellen chart, you will be asked to read the letters on each row, the further down the chart you get, the better your vision. Corrective lenses are usually able to help most people read the letters further down the chart. If they do not, there may be an underlying condition causing problems with your vision.

Vision Tests

Your near vision (reading), intermediate vision (using a computer), and distance vision will all be tested too. There are few tests they will do, one includes stating if an O is sharper or blacker on a red or green background, usually covering one eye. You may also have a colour vision test.

How do you treat a Visual Impairment? 

Unfortunately, for most conditions, there is no cure for visual impairment or blindness, however, there are some treatments, as well as vision aids to help you try and make the most of your remaining sight.

Vision Aids

There are a few aids that can help make day to day life a little easier if you are living with a visual impairment.

Magnifiers– You can use magnifiers such as illuminated stand, flat-form, hand-held, pocket, or electronic (allows you to project onto TV screen/computer monitor, as well as adjust contrast, enhance or reverse colours) to help with tasks. Monocular or binoculars can also be used for seeing objects in the distance.

Bright Lighting – Bright lights can help improve sight and make it easier to move around, this can include items such as an Anglepoise lamp or installing much brighter lights.

Bold/Large Print Books/eBooks – These can help make reading easier.

Liquid Level Indicators – These stop you from burning yourself with hot water by beeping once it reaches a set temperature.

Big Button Phone & Keyboard – These can make it easier to see the details of the numbers and letters.

Braille – Braille can be a useful tool for those with severe sight loss, especially if affected from a young age. Braille is a writing system that uses raised dots as a substitute for written letters. You can get braille versions of books and magazines, braille keyboards, and Braille display units – these can be attached to your computer so that you can read the text displayed on a computer screen.

Computer Software – Software like text readers, screen display programmes, or voice recognition, can help make use of the computer and the internet more accessible. This can help you stay in touch with friends and families, as well as other communities.

Community Alarm – A wearable alarm can be pressed to alert a response centre, who can contact your nominated friend or carer that you need help. Your local authority will be able to give you some more information about the system.

Two-tone Interior Décor – This style of décor can help to provide contrasts in the home when trying to tell the difference between nearby and far away objects – e.g. the stairs and the hand rail.

A Long Cane – This can be used to help you when you are walking or travelling around, allowing you to detect any objects in your path. Canes are usually foldable, and they can help let others, including drivers, know that you are visually impaired. 

Guide Dogs – Guide dogs can offer practical help with mobility, as well as let the owner claim a sense of independence. It also provides companionship and confidence to those affected with a vision impairment – this can be important for day-to-day life and help with the isolation many experience from their condition.

GPS – A GPS navigational system can tell you where you are and help you with planning your journeys, giving you instructions of when and where to turn. You can hook up your GPS device to a braille keyboard (the ones that are compatible), or if you have a smartphone, there are a range of GPS apps you can download.





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