Eye health conditions explained

Optometrist Will in his testing room smiling
Did you know that regular eye tests are an easy way to look at your overall health as well as that of your eyes?

You may not be aware that you have any of these conditions – feeling well and having no problems with your eyesight. This is why it is so important to have regular eye exams, as early diagnosis of any health conditions means early treatment and could even save your life.

Table of Contents

Eye health conditions that can be corrected with glasses or contact lenses

Hypermetropia (long or far sight)

Long-sight is when the light entering the eye would be brought to a point of focus beyond the retina, causing a blurred image. This can be caused by the eyeball being too small or the lens not having enough focusing power. It is simply corrected with lenses that cause the image to focus on the retina. You will know you have this if the number in the ‘Sphere’ or ‘SPH’ box on your distance prescription has a +(plus sign) in front of it. It means that things that are close to your eyes might be blurry.

Myopia (short or near sight)

Short-sight occurs when light entering the eye is brought to a point of focus in front of the retina, causing a blurred image. This can be due to the eyeball being too long or the lens having too much focusing power. It is simply corrected with lenses that cause the image to focus on the retina. You will know you have this if the number in the ‘Sphere’ or ‘SPH’ box on your distance prescription has a – (minus sign) in front of it. It means that things in the distance might be blurry.


This is a very common condition where the light rays from objects are not brought to a single sharp focus within the eye. This is often caused by the front surface of the cornea having an irregular shape, i.e. being similar in curvature to he side of a rugby ball, instead of being spherical like a football. It is very straightforward to correct, using lenses with more power in one direction than another. These are called ‘cylinder’ lenses or ‘Cyl’, and must be prescribed with an ‘axis’ to ensure the power is working in the correct direction for your vision.


Presbyopia is a condition where the eye has difficulty focusing on near objects, when reading for example. The process of focusing on near objects is called accommodation. With age the lens, which enables accommodation, becomes less flexible and after we reach our early to mid forties, focusing on close objects becomes increasingly difficult. Although it often seems to occur suddenly, the loss of flexibility takes place over a number of years.


Presbyopia is part of the eye’s natural ageing process. It happens to everyone regardless of whether they need glasses for short-sight, long-sight or astigmatism. It cannot be prevented. One of the first signs of presbyopia is the need to hold reading material further away to see it clearly – a common complaint is “my arms aren’t long enough!”. Other symptoms include blurred vision for reading, or eyestrain and headaches when doing close-up work.


Early on, simply holding close material further away helps, but eventually a near vision correction is the spectacles or contact lenses is required. This is described on prescriptions as a ‘reading addition’ or ‘Add’.


Some short-sighted people can delay the need for a near vision correction by removing their spectacles for reading and close work. The most appropriate type of near vision correction is dependent on your lifestyle, occupation and hobbies. If you have good distance vision and only have difficulty seeing close up, a separate pair of near spectacles is often the easiest solution.


For others, needing separate prescriptions for distance and near means two sets of glasses and this can prove frustrating. In these cases, glasses with varifocal lenses may be more appropriate. Varifocal lens technology has advanced considerably over recent years to provide lenses that provide good vision at all distances, including the intermediate range, which is ideal if you use a computer There are also a wide range of contact lenses options for presbyopia.

Strabismus (squint or crossed eyes)

This is a visual defect where the eyes are misaligned and point in different directions. There are two different forms of strabismus being referred to:


  • Esotropia – where the eye points inwards
  • Exotropia – where the eye points outwards


In each case, the brain will not be able to use the vision from both eyes because each eye will be receiving light from a different direction The brain will suppress the image from the weaker eye, called amblyopia, and three dimensional vision and depth perception will be lost.


This can be corrected in children if detected early enough. However, in adults, it is corrected with glasses containing a ‘prism’ designed to bring light from the same object to both eyes.

Eye health conditions that are treatable with surgery or medication, or a combination


A cataract forms when the clear lens of the eye, behind the iris, which focuses light to provide sharp images, becomes cloudy and hardens, causing a loss of sight. Cataracts are painless and gradually develop over a long period of time. Over 50% of people aged over 65 have some form of cataract development and most cases can be treated successfully with surgery, where the lens is replaced by a clear plastic one. It can be caused by age, trauma, diabetes, long term steroid therapy, excessive exposure to UV light or hereditary.


Glaucoma is an eye condition where your optic nerve is damaged by the build up of pressure in the fluid inside your eye. The increased pressure pushes the contents of the eye back, which eventually leads to damage to the retina. This damage causes the field of vision to be reduced. This is measured accurately with a visual field test.

Glaucoma affects 2% of the UK population over the age of 40 and there are many different types of glaucoma. Most types of glaucoma have no symptoms, so a regular eye test is the only way to know you have the condition, which causes permanent sight loss. It affects the peripheral vision, or side vision, so it is often not noticed for quite some time. There is no treatment to restore sight loss caused by the disease. Eye drops and laser surgery may help to prevent it worsening once detected. 

Age Related Macular Degeneration

Age Related Macular Degeneration is the most common cause of poor sight in people over the age of 60. The macula is the small central part of the retina, which is responsible for what we see when we look straight ahead, allowing us to see fine detail when reading or recognising faces, as well as allowing us to see colour. The cells of the macula are very delicate and can become damaged over time. When this occurs later in life, it is known as age related macular degeneration (AMD). There are 2 main types of AMD:

'Dry AMD'

This accounts for about 90% of cases. It develops slowly over a number of years causing gradual loss of central vision. People often complain of difficulty with detailed tasks such as reading, writing and recognising small objects. Stronger reading glasses can help in the early stages. Low vision aids such as magnifiers can help make the most of the remaining vision. In the advanced stages of the disease, people may notice a blank patch or dark spot in the centre of their vision, making detailed tasks very difficult. Unfortunately, there is no treatment for dry AMD.

'Wet AMD'

This generally develops more quickly, resulting from new blood vessels growing behind the retina leading to bleeding and scarring. It causes a loss of vision which is often more severe than dry AMD. Wet AMD often causes symptoms of blur or distortion, causing straight lines to appear wavy. Objects may appear an unusual size or shapes. If you develop any of these symptoms suddenly, you should seek advice as soon as you can. Wet AMD is sometimes treated using lasers to seal leaking vessels. This is an area in which research is ongoing and new treatments are constantly being developed. 


AMD usually involves both eyes, although one eye can be affected before the other. Using the ‘good’ eye will not wear it out, so don’t be afraid to use it as normal. AMD is not painful, and never leads to total blindness as it only affects the central vision.

What causes AMD?

The exact cause is not known, but a number of risk factors have been identified:

  • Age – AMD is age related and therefore is more likely later in life.
  • Gender – Women appear more likely to develop the disease.
  • Smoking – Several studies have shown that smoking increases the risk of AMD. Stopping smoking is therefore important for the eyes, as well as for your general health.
  • Nutrition – There are many treatments and vitamin supplements for macular degeneration.
Having regular eye checks is vital to ensure that any early signs of the disease are picked up and treatment is started quickly. Even though you may not be aware of any change in your vision at all, your Optometrist will be able to see small changes that could indicate macular degeneration or other problems such as cataracts. Early detection of macular degeneration is vital to help ensure the best outcome possible.

From the age of 40 onwards, there is an increased risk of developing eye conditions such as glaucoma. This risk increases over the age of 60, with many people developing cataract and the risk of developing macular degeneration. For this reason, regular eye examinations are advised. Eye examinations are available on the NHS for those over 60.

Other health conditions that can be detected during an eye test


The small capillaries in the retina of the eye are damaged by diabetes which may result in blood or fluid leaking from them. This can be detected in a routine eye exam, though the patient may have no symptoms. This is called diabetic retinopathy and as it progresses, symptoms may include:

  • Blurred vision
  • Floaters
  • Shadows and missing areas of vision
  • Blindness

A comprehensive eye exam is the only way to detect the early stages of diabetic retinopathy, before symptoms begin to affect the person’s sight. Regular testing will help your Optometrist to monitor the condition closely. Whilst treatment cannot usually reverse damage already done, it will keep the disease from getting worse. Surgical procedures can shrink the abnormal blood vessels and reduce swelling. Close monitoring of blood sugar, blood pressure and cholesterol by health professionals, along with regular eye exams by an Optometrist is vital to help prevent diabetic retinopathy. If your Optometrist detects any changes in these blood vessels, referral for further examination by an Ophthalmologist may take place.

High Cholesterol

High levels of harmful cholesterol in the body will cause plaque to develop within the arteries. This can restrict blood flow by causing blockages. As the eye has many tiny blood vessels, symptoms of high cholesterol will be present in the eye and can be detected at a routine eye exam. Identification of high cholesterol is often done via the eyes, as these are visible to the naked eye, unlike other blood vessels in the body which are under the skin.

When cholesterol becomes visible in the eye, it indicates that the person has a high level and they should seek to reduce this to prevent further damage and other conditions developing. An unhealthy lifestyle can be the cause of high cholesterol, or it could be a hereditary condition that has caused it to develop. Diet and lack of exercise can lead to the problem and a change in lifestyle will help to reduce cholesterol levels. High levels of cholesterol can lead to the development of other conditions such as:
  • Heart disease
  • High blood pressure
  • Stroke
  • Diabetes
  • Peripheral vascular diseases, which  cause sudden loss of vision

Cancer of the Eye

There are several forms of eye cancer, which can begin in the eye or can spread to the eye from other parts of the body.

Cancers that begin in the eye and could spread to other parts of the body can include:

Ocular melanoma – Uveal melanoma is a cancer inside the eye that affects approximately 600 new cases in the UK each year, making it a rare cancer. Unfortunately, development of tumours elsewhere in the body is found in half of all patients.

Ocular melanoma – Conjunctival melanoma appears on the surface of the eye, which are usually coloured and raised. Some are clearly visible while others can be hidden behind the eyelid. Up to 2% of all ocular melanomas are conjunctival, making it very rare. There are other types of cancer which can involve the conjunctiva.

Intraocular lymphoma – This is normally Non-Hodgkins type. Primary lymphoma (starts in the eye) can be found in several internal parts of the eye.

Retinoblastoma – A rare cancer that almost exclusively affects young children, being the most common eye cancer found in children. The prognosis for this cancer when treated has been very good although some vision may be lost. Often this is picked up when photographers’ flash is used. The resulting photo may show a white glow as the tumour reflects the flash back towards the camera.

Cancers can spread to the eye from other parts of the body and can include breast cancer, lung cancer and skin cancer. This is called secondary cancer of the eye.

For more information about cancer of the eye please visit the OcuMel website at www.ocumeluk.org.

High Blood Pressure

Untreated high blood pressure, or hypertension, can lead to damage of the blood vessels in the eye. The person may suffer headaches and vision problems, which will be discussed with the Optometrist at a routine eye examination. Signs of hypertensive retinopathy, caused by high blood pressure will be present at the back of the eyeball and could include:
  • Narrowing of the blood vessels
  • Fluid leaking from the blood vessels
  • Spots on the retina
  • Swelling of the macula
  • Areas of bleeding inside the eye

The Optometrist would refer the patient to their GP for further diagnosis of high blood pressure and treatment to reduce this, including diet and lifestyle changes.