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Throughout our lifetime our vision is likely to deteriorate slowly. It is a fact that most of us in our older years will require visual correction – glasses for long distances, or glasses for short distances.
With this type of deterioration, you might not notice any differences initially. But at some point, you might start to feel headachey when you drive or watch TV, as your eyes have to strain to focus on things. Or you may notice that you have to hold your book further away from your face to be able to read the pages.
If you notice a deterioration in your vision, it is always important to see an optician. And, if this change has happened over days, hours, or more suddenly, you must make sure that you are seen urgently by a doctor.
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Sudden or Short-term Visual Loss
There are lots of different conditions that can cause you to lose vision suddenly.
Visual loss which happens over a short period is known as acute visual loss. Here are several of the most common types of acute visual loss, their symptoms, and what treatments are available.
Central Retinal Artery Occlusion/Central Retinal Vein Occlusion
Your retina sits at the back of your eye. It is the bit that light is focused onto and is essential in allowing you to see. It has its own blood supply with a network of arteries and veins that come into the eye through a small opening at the back. If the main artery or vein which supplies or drains this network of blood becomes blocked, this can lead to a loss of vision.
If the artery becomes blocked, then the loss of vision may be sudden. It is usually painless and only on one side.
If the vein is blocked, loss of vision can also be sudden, but can also develop over a few hours or days. It is also painless and usually only in one eye.
Both conditions require treatment urgently. The longer the time between the blockage forming and treatment starting, the more likely you are to have permanent vision loss.
Treatments can include eye drops and injections placed in or around the eye.
The globe of your eye is filled with a jelly-like fluid known as the vitreous humour. It usually is transparent, allowing light to travel through to the back of your eye. It is attached at the back of your eye to your retina.
If there is bleeding into the vitreous, this stops light from being able to travel through to the retina. This can cause partial or complete loss of vision.
Many things can cause bleeding into this fluid, and treatment will depend on what has caused it. The most common causes of vitreous haemorrhage are:
- Diabetic eye disease, or diabetic retinopathy. As blood vessels become damaged from frequent changes in blood sugar, new blood vessels are created at the back of the eye. These blood vessels are more prone to leaking than healthy blood vessels, and as a result, may bleed into the vitreous.
- Posterior vitreous detachment. Your vitreous attaches at the back of your eye to your retina. It is quite common, as you age, for the vitreous to start to come away from the back of the eye. If it does this suddenly, it might cause a tear in your retina, which can cause bleeding.
- Trauma to the eye.
Once the source of bleeding can be identified, laser therapy may need to be used to stop the bleeding. The blood in the eye will then slowly clear on its own over a few weeks, and your vision should improve.
The main globe of your eye is made up of three layers. Imagine your eye as a golf ball, and then wrap that golf ball in a layer of cloth, and then wrap that cloth in cling film – the middle layer of cloth is known as your uvea. At the front of your eye, this includes your iris (the coloured ring).
This part of the eye can become inflamed due to an infection or certain medications, but most commonly due to auto-immune diseases.
Some examples of auto-immune conditions are sarcoidosis and rheumatoid arthritis. These are conditions where your immune system attacks different parts of your body, causing inflammation.
When this happens to the front of your uvea, it is known as anterior uveitis. This causes a red eye, which is usually painful when looking at light. It can also cause blurred vision.
Treatment is with eye drops that reduce the pressure in the eye and with steroid eye drops. If left untreated, it can cause loss of vision and is one of the most common causes of preventable vision loss in the UK.
Around 1 in 1000 people develop acute glaucoma in their lifetime. This is where the aqueous fluid, which is a fluid inside your eye that drains out next to the iris, stops draining due to a blockage. This then leads to a build-up of pressure inside your eye, which can damage the optic nerve (the nerve that goes from the back of your eye to your brain and is essential in helping you see).
Glaucoma can be acute or chronic. If you have chronic glaucoma, you may simply develop a slow blurring of your vision over a long period, which you overlook. This is why it is essential to get regular check-ups with an optician.
If it is acute, then the pressure in the eye may increase quickly. This causes pain, blurring of vision, and redness of the eye. You may notice circles around lights when you look at them, or even get a headache, feel sick, and vomit.
Acute glaucoma is an emergency, as delayed treatment can cause the damage to your optic nerve to worsen. Treatment is aimed at reducing the pressure in the eye, and eye drops or injections of medicines into a vein can be used to do this.
Chronic Visual Loss
Loss of vision can occur slowly, over months or years. In this scenario, it is known as “chronic visual loss.” You may not notice this type of visual loss until it has progressed to the point where you need visual aids, such as glasses. The first clue that your vision is deteriorating could be headaches when you try to focus on things that are further away, such as the television.
The two main conditions which cause chronic visual loss in the UK are cataracts and macular degeneration.
Almost 50% of people older than 75 will develop cataracts. A cataract is where the lens of your eye becomes opaque, stopping light from travelling through it and causing you to lose your vision slowly, over time.
The lens is the part of your eye that sits inside your iris. It works like glasses and is responsible for bending light so that it focuses on your retina. It is important that it is see-through and functions properly so that you can see clearly.
Several different things can cause cataracts. By far the most frequent cause is just getting older, but others include:
- Trauma (which sometimes can cause cataracts years later)
- Drinking too much alcohol
- Medicines, such as steroids
- Too much sunlight exposure.
The only real symptom of cataracts is the slow blurring of vision, as the cataract forms over time. It might be possible, in severe cataracts, to be able to see that the inside of the pupil looks white. This is because the lens becomes visible as it becomes more and more white. In most people, however, the eye looks normal. You may also see haloes of light, or circles, when you look directly at light sources or have difficulty distinguishing dark blue from black.
Your doctor can diagnose cataracts by merely looking into the eye with a light.
Initially, treatment may only be the need for glasses. However, if the cataract becomes severe, it may need surgery to remove it. The lens is then replaced with a plastic or silicone lens so that you can continue to see.
If you are undergoing cataract-removal surgery, it is most likely that you will be awake. A local anaesthetic will be injected behind the eye, so you will be unable to see or feel what is happening.
Complications from cataract surgery are rare, but include:
- Infection within the eye (antibiotics are often used, either during or after surgery to reduce this already very rare risk)
- Swelling of the white part of the eye where damage may have been caused during surgery. This is unlikely to cause any problems with vision, but may be noticeable
- Very rarely, complete loss of vision
- Retinal detachment. This is where the retina comes away from the back of the eye. It tends to happen months after surgery, is relatively rare, and can be treated with laser therapy.
Your macula sits in the central part of your retina. It is responsible for focusing the central part of your vision.
In macular degeneration, this part of your eye becomes slowly damaged over time, leading to central vision loss.
There are two types of macular degeneration – dry and wet.
In dry macular degeneration, small yellow deposits form, causing areas of blurred vision. These are known as drusen. This slow loss of vision progresses over the years, and can eventually lead to significant visual impairment.
In wet macular degeneration, abnormal blood vessels are formed, which slowly leak into the retina. This causes permanent damage, which leads to the central part of your vision being permanently lost. This is seen as a dark spot and is known as a scotoma.
Both forms of the disease become more common with age. There may be a genetic component, and people who smoke or are obese are also more likely to get the disease.
As it develops over a long time, an optician can diagnose it before you develop any symptoms by looking at the back of the eye. For this reason, it is essential to make sure that you get regular eye check-ups after the age of 40.
Both forms of macular degeneration are unfortunately incurable. Wet macular degeneration tends to progress more quickly and be more severe than dry macular degeneration.
For wet macular degeneration, you might receive injections into the eye to help slow the progression of the disease.
If you have been diagnosed with macular degeneration and feel like you need to talk to someone or get some extra support, The Macular Society is a UK based charity dedicated to helping people. They operate a helpline for those who need to get some advice and also run support groups.
People who are diabetic often suffer from large swings in their blood sugars. The frequent drastic changes of these levels cause damage to blood vessels throughout the body, including in the retina. When this happens, the blood vessels can become leaky, which causes damage to the retina. To try to combat this, the body starts to form new blood vessels to the damaged areas, but these vessels can cause further damage and leaking.
This damage occurs slowly over time, and as such, the visual loss is slow but progressive. People who have diabetes should be examined once a year for the development of this condition.
If these abnormal new blood vessels are seen when the eye is being examined, they can be removed by laser surgery. This can help to preserve the vision in the eye.
The best way to prevent yourself from developing this condition if you have diabetes is strict blood sugar control. Keeping your blood sugars within normal levels should help to prevent you from developing this condition.
Diabetes UK is a charity dedicated to helping people with diabetes. They operate a helpline to answer questions related to all aspects of living with diabetes and also run support groups.
Loss of sight can be extremely debilitating. It can affect mobility and social independence. It is crucial to maintain good eye health, and ensure that you are getting regular check-ups from an optician. You may be entitled to free eye check-ups. To check if you are eligible, visit the NHS page on free NHS eye tests and optical vouchers.
Acute visual loss is an emergency, and if you experience loss of vision over a short period, you must be seen and assessed urgently. If you experience this condition along with any other symptoms, such as weakness in the face, arms or legs or difficulty speaking, call 999 as you may be having a stroke.
Chronic loss of vision can be insidious. Many forms of chronic visual loss are treatable. Therefore it is vital to ensure that you are seeing an optician regularly.
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Many charities operate in the UK, specifically for people who are suffering from sight loss. The Royal National Institute for the Blind (RNIB) runs a helpline, where you can get advice on what is available for you.
If you are suffering from a loss of sight, you might be eligible for adaptations to your home or, if your vision loss is severe, even a guide dog. For further information on where to access these resources, start by calling the RNIB helpline.
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Medical terms are often baffling and difficult to fully understand. To help, we have listed some frequently used terms below.
Cataract – a condition where the lens of the eye becomes opaque, causing progressive blurring of vision
Glaucoma – a medical condition which causes increased pressures within the eye, which can lead to loss of sight
Laser-therapy – a type of non-invasive eye surgery, where lasers can be used to treat conditions at the back of the eye
Macula – this is a part of the retina which is responsible for the central part of your vision
Optic nerve – the nerve which goes from the back of your eye into your brain. It is necessary for your brain to be able to interpret the images captured by your retina
Optician – someone who is trained to evaluate eyes and provide glasses or contact lenses. They are also able to assess the eyes for certain diseases
Retina – a piece of tissue which sits at the back of the eye and captures light, so that your brain can interpret images
Uveitis – inflammation of the uvea, which is a layer of tissue that makes up the main globe of the eye
Vitreous – a transparent jelly-like fluid which sits inside the eye