Humans have five basic senses; sight, taste, smell, hearing and touch and these five senses provide our brains with vital information about the world around us. Our eyes may be relatively small, but they are incredibly powerful, allowing us to see the world around us. It is estimated that around 80% of the sensory information our brains use is provided by our vision.
Structure of the eye
- Cornea – clear tissue at the front of the eye.
- Iris – the coloured part of the eye, which surrounds the pupil and regulates light.
- Pupil – hole in the iris that allows light into the eye.
- Lens – a small clear disc that focuses light rays onto the retina.
- Vitreous – clear, jelly like substance that fills the middle of the eye and maintains the eye’s shape.
- Retina – a layer of tissue that that lines the back of the inside of the eye , senses light, and creates electrical impulses that travel through the optic nerve to the brain.
- Macula – small central area in the retina that is responsible for detailed, central vision.
- Optic nerve – connects the eye to the brain and carries the electrical impulses formed by the retina to the visual cortex of the brain.
How the eye works
When you look at an object, the eye takes in reflected light rays through the cornea at the front of the eye. Light travels through different areas of the eye, including the pupil and lens and becomes focused onto the retina, a thin membrane which covers the back of the eye. The retina contains millions of nerve cells which form the optic nerve and is connected directly to the brain.
Although the image captured by the retina is upside down, the brain is able to convert the image so you see the “correct” version of the world. The retina also contain specialised photoreceptor cells called cones and rods. Cone cells help the brain see fine details and perceive colours. Rod cells provide peripheral vision and enable us to see in poor light.
Managing eye health
Many factors, such as illness, smoking, diet and lifestyle can affect the health of your eyes. It is important to have regular check-ups (every two years) by an optometrist. As well as checking your ability to discern shape and detail of objects, (visual acuity), an optometrist’s job is to test other aspects of your vision to detect any changes or abnormalities in your eyes.
Diabetics have an increased risk of developing an eye disease and should be extra vigilant to any changes in eye health or vision.
What to do if you are concerned about your eyes or vision
If you notice anything unusual with your vision, something has suddenly occurred or if something has changed recently, you should contact your optometrist or ophthalmologist straight away to arrange an examination. Do not delay seeing an eye care professional. Many eye conditions will not get better of their own accord. If detected early enough, some conditions can be treated or managed effectively, with little or no loss of vision.
Common eye problems and conditions
Human vision is complex and sometimes our eyes don’t work the way they should, because of eye conditions, illness or disease. There are many eye conditions that cause vision impairment or blindness in Australia. The causes and onset of these vary and include:
- Acute eye conditions (occur suddenly, eg. through injury or illness)
- Chronic eye conditions (long term conditions, which usually progress gradually)
- Congenital eye conditions (conditions you are born with)
- Genetic/hereditary eye conditions (inherited through parents)
Signs and symptoms of common eye conditions
There are many indications that you may have an eye condition. Not everyone will experience the same symptoms. We have highlighted some of the more common signs of eye disease that can lead to vision loss below. If you experience any of these signs, we recommend getting checked by your optometrist as soon as possible.
Night blindness or difficulty seeing in low light
Having trouble seeing outside in the early evening or in a poorly-lit room is often referred to as “night blindness”. Everyone’s eyes require one to two minutes to adjust to a darkened room, but with certain conditions, it can take much longer – or they may not adjust at all. Night blindness can be a sign of:
- Some retinal dystrophies including Retinitis Pigmentosa
Loss of central vision
Deterioration, unclear, distorted or a blurred patch in the centre of vision can be an indication of an underlying eye disease. Peripheral (side) vision is usually unaffected. A gradual loss of central vision is often associated with:
- Macular degeneration
- Stargardt’s Macular Dystrophy
Peripheral (side) vision loss (tunnel vision)
Unclear or distorted areas around the outside of vision, creating a narrowing or giving a sense of looking through a tube is also known as “tunnel vision”. “Tunnel vision” is often an underlying symptom of:
- Retinitis pigmentosa
Noticeable large specks, circles or clear fine lines in the field of vision, usually when looking at a plain background – eg. light coloured wall. They will move away if focused on. Many people have eye floaters and they are usually harmless and nothing to worry about. Floaters are common, often age-related, but can appear after injury or if you are short-sighted (near-sighted).
They are caused by microscopic fibres clumping together inside the jelly-like substance inside your eye (vitreous humour), which casts a shadow onto the retina. Floaters very often dissipate of their own accord after a few months, but if more floaters than usual are experienced or there is a sudden onset of floaters, get your eyes checked as soon as possible. Eye floaters can be an early sign of:
- Retinal detachment
Your ability to see shapes and detail (visual acuity) can become blurry over time. This is often a result of ageing and/or being short-sighted or long-sighted. These conditions are usually able to be corrected with prescriptive lenses. However, a more sudden onset of blurred vision should be checked out by an optometrist as soon as possible. This can be an indicator of:
- Diabetic retinopathy
- Macular degeneration
- Retinal detachment
Dark shadows behind the eye
A dark shadow, which appears as a “curtain” and obstructs part or all of your vision requires immediate medical attention – do not delay. Attend a hospital emergency department or eye clinic within 48 hours. A dark shadow is frequently a sign of:
- Retinal detachment
- Haemorrhage in the retina due to blockage of a blood vessel
Flashing lights in the eye
Many people have flashes of light in the corner of their eyes – and this is normal for them. If you experience a sudden onset of flashes or if the normal flashes change in any way, arrange for an eye check by an optometrist as soon as possible. Eye flashes can be a symptom of:
- Ocular migraine
- Retinal detachment
- Vitreous detachment
Straight lines appearing wavy or distorted
If straight lines eg. building walls appear to be wavy or distorted, or if parts of it appear to be blurred or “missing”, this can be an early sign of:
- Macular degeneration
Pain on the surface of the eye (ocular)
Ocular pain can be caused by injury, infection, foreign objects (such as an eyelash) or an abrasion to the cornea. Although these can be painful or uncomfortable, they are rarely a sign of a serious condition.
Pain within the eye (orbital)
Migraines or sinus infections often create pain or discomfort within one or both eyes and do not usually require emergency treatment. However, pain from within the eye itself, and especially if accompanied by loss of vision should be considered more serious and immediate medical treatment should be sought.
Pain within the eye can be a sign of:
Eye conditions leading to vision loss can include:
Albinism is a genetic (inherited) condition that reduces the amount of melanin which produces the pigment (colour) in the skin, hair and eyes. The condition can affect all races and ethnicities, but does not limit life expectancy. People are impacted differently, but typically have very blonde/white hair with pale skin and pale blue, violet or pink eyes.
In ocular albinism, only the eyes lack pigment. In oculocutaneous albinism, the skin, hair and eyes all lack pigment and cannot adequately screen out excessive light, creating sensitivity to bright light and glare (photophobia). People with albinism will have some form of vision impairment, but the severity and type varies from person to person, even those with the same type of albinism.
Typically, these include:
- Nystagmus (involuntary flickering of the eyes)
- Photophobia (sensitivity to light)
- Long or short-sightedness
It is important for people with albinism to protect their skin and eyes from the damaging effects of the sun and have regular eye checkups. For more information, visit Albinism Australia (link opens in new window).
Amblyopia, sometimes colloquially referred to as lazy eye, usually occurs in just one eye, typically as a result of interference in focus from one or the other eye. The brain begins to ignore the visual impulses from the weaker eye, favouring the other, stronger eye. It occurs in early childhood, usually before the age of five.
Early detection is essential for treatment ideally, before the age of 8 years. Some improvement may be seen up to 10 years, but treatment is usually unsuccessful and rarely attempted beyond 10 years of age. Studies show that improvement is highly unlikely after the age of 10. A lazy eye will not usually correct itself – if left without treatment, the weaker eye will continue to have permanently low vision.
There are three main causes:
A large difference in refractive error, or glasses prescription (short-sighted or long-sighted) and subsequently, visual acuity between the two eyes, with one eye able to see better than the other.
Strabismic (misaligned eyes)
The eyes are not aligned properly and do not both look at the object of fixation at the same time. The misaligned eye can turn in towards the midline, outwards from the midline, up, down or a combination of a horizontal and vertical deviation. Strabismus can be present constantly or intermittently, and can involve one eye consistently, or alternate between eyes.
The misalignment of the eyes causes double vision, though a child’s brain will suppress the second image to avoid this. This suppression of the second image can lead to amblyopia (also known as “lazy eye”) due to disuse of the turning eye and its pathways to the brain.
An obstruction or deprivation of vision, such as through congenital cataracts or a drooping eyelid.
Correcting a lazy eye
Treatment of the root cause, through prescriptive lenses or removal of the obstruction is followed, generally, by forcing the use of the weaker eye by patching or obscuring the stronger eye for part of the day, continuing until vision is corrected.
Aniridia is typically a congenital condition in which part or all of the iris of the eye is missing. It makes the eye appear as though it has little or no colour and is larger than a normal pupil. When part of the iris is missing it is referred to as a “coloboma”. Colobomas can be congenital or as a result of trauma. Both eyes are usually affected and associated complications can include:
- Retinal detachment.
The iris controls the size of the pupil and how much light comes into the eye. Aniridia prevents the eye from controlling the amount of light entering, which can lead to blurred vision and light sensitivity (photophobia). A family history of aniridia increases risk of developing the condition, but some people with it, have no previous family history of it.
Treatment usually requires regular examinations and a focus on correcting the visual acuity with a sunglasses tint, designed to protect the eyes from sunlight. In some instances, a special type of coated contact lens can reduce the impact of glare, correct the vision and cosmetically enhance how the eye appears.
Cerebral Vision Impairment
Cerebral vision impairment (CVI) is a brain-based visual condition, most often affecting children. It occurs when the part of the brain (the visual cortex) that receives and decodes the message sent from the eye is poorly developed, damaged or missing. This means that messages sent to the brain from the eyes are not properly understood by the brain. Usually the eyes appear to be perfectly normal and function correctly when they are examined.
Another way of describing it is that we look with our eyes, but we “see” with our brain, as the eye receives the light but the brain is responsible for interpreting the light signals into our visual world. Sometimes the cerebral vision impairment is temporary and lasts weeks or months. Sometimes the damage is permanent and messages from the eyes are not decoded. The vision of children with CVI can improve, but rarely to normal levels.
CVI is often associated with other difficulties in development, movement and learning, such as those from in cerebral palsy. CVI is the most common cause of vision impairment in children in developed countries.
Visual processing difficulties can be the sole feature of cerebral vision impairment, or may accompany additional eye conditions, diseases and need for glasses. CVI is most common in children who experience a form of seizure disorder, or have experienced brain injury from stroke or similar.
Treatment of CVI
There is no cure for CVI, but children can benefit from therapies, early intervention and additional specialist educational support. In some cases, the condition gets better of its own accord.
A cataract is a clouding of the normally clear lens in the central part of the eye. Most cataracts are age-related, but in some cases, you can be born with them (congenital cataracts) or can develop after an eye trauma (such as injury or surgery). They can affect one or both eyes and are painless.
For someone who has a cataract, it is like looking through a frosted window.
It is formed when the proteins that make up the lens start to deteriorate around the age of 40. They become damaged and start to cluster together. The cluster creates a cloudy area on the lens, which is the cataract. The cataract gradually becomes worse, clouding more of the lens.
Age is generally the biggest factor in cataracts, with over 70% of Australians aged 80 or over having signs of cataracts. All humans will develop a cataract if they live long enough. Certain health and lifestyle factors can also influence the speed of development, including:
- Family history
- Time in the sun without proper eye protection
Cataracts will not get better of their own accord and treatment is by surgery to remove the damaged lens and replace with a new, synthetic lens. The surgery is quick and extremely safe. In Australia and other developed countries, it is close to 99% successful in the general population who have no other eye conditions. Complications from cataract surgery are rare and the most common is swelling within the eye, which is treated with eye drops and usually resolves in a month or two.
Diabetic Eye Disease
Diabetes is a serious long-term condition that hinders the body’s ability to process blood glucose (blood sugar) levels effectively.
The pancreas is an organ in the body that produces insulin – a substance which helps regulate the level of sugar in the blood. Diabetes disrupts the ability of the pancreas to produce sufficient insulin.
Too much sugar in the blood damages blood vessels and this damage can cause significant problems for many areas of the body, especially the eyes, limbs, brain and nerves.
There is a direct link between the risk of eye disease and the duration of diabetes. The longer you have had diabetes, the more important it is to take extra care of your eyes and get regular checkups by an optometrist.
Although diabetes cannot be cured, in many cases, careful daily management of the condition can greatly reduce or prevent permanent damage. For more information, visit Diabetes Australia (link opens in new window).
Types of Diabetes
This is an unpreventable condition which can happen at any age, although typically it first occurs in children or young adults.
The body’s own immune system attacks the cells of the pancreas. Why this happens is unclear. People living with type 1 diabetes must closely monitor their blood sugar levels each day and administer insulin therapy.
This is a long term, or chronic condition, where the body develops a resistance to the effects of insulin. Over time, the pancreas loses the ability to produce enough insulin.
It is unclear what causes this to happen, but it is often associated with lifestyle (poor diet, obesity, lack of exercise etc).
Daily monitoring of blood sugar is required, but insulin therapy is not usually necessary. Modifications to diet, exercise and lifestyle is often sufficient to effectively manage the condition.
This condition only occurs during pregnancy and can affect 5-10% of women in Australia. The placenta produces hormones which help the baby develop, but these hormones can block the effect of insulin on the woman’s body.
Following the birth, blood sugar levels usually return to normal and the diabetes subsides. However, both the mother and baby have an increased chance of developing type 2 diabetes later in life.
How can diabetes affect eyesight and vision?
Increased levels of blood sugar can change the shape of the lens within the eye, which affects how the eye focuses. This can cause blurred vision, and fluctuates with glucose levels. It is a usually a temporary effect, but in some instances, can last for weeks or even months at a time.
Cataracts, where the lens becomes cloudy, can affect anybody, but occur more frequently and often develop earlier in people living with diabetes.
Diabetes causes retinopathy due to elevated blood sugar levels damaging the blood vessels that nourish the retina: the “seeing” part at the back of the eye. When these vessels become damaged, signals are sent to attempt to grow new ones – which are often more fragile or abnormal.
Damage increases over time, eventually causing the blood vessels to leak. Vision often becomes patchy and fluctuates with blood sugar levels. The damage can cause vision impairment or blindness.
It is expected the majority of people who live with diabetes will develop diabetic retinopathy. There are two stages of diabetic retinopathy:
Early stage – Non-proliferative diabetic retinopathy (NPDR)
This is a more common form of retinopathy, where blood vessels do not regenerate (proliferate). Damage to the walls of the existing blood vessels, causes it to weaken and leak fluid into the retina, but does not typically affect vision.
In some instances, the leaking blood vessels can create a build-up of fluid in the centre area of the retina, known as the macula. This build-up of fluid is known as Diabetic Macular Oedema.
This is the most common cause of vision loss in people with diabetes and can threaten central vision. Early treatment can help prevent permanent vision loss.
Later stage – Proliferative diabetic retinopathy (PDR)
As diabetes and damage to the eyes progresses, risk of total (“black”) vision loss is increased.
Damage to the blood vessels cause them to close off, prompting growth of new, abnormal vessels in the retina and complications can include:
Damage to blood vessels can affect fluid movement in and out of the eye, creating an increase in pressure which can damage the optic nerve – which connects the back of the eye to the brain.
This damage can create permanent and irreversible damage to vision.
Growth of these new blood vessels can trigger the creation of scar tissue and eventually cause the retina to pull away and detach from the back of the eye.
New blood vessels can bleed into the vitreous (the jelly in the middle of your eye) and create dark patches or floaters. If enough blood fills the vitreous cavity, it can create a complete block of vision.
Vitreous haemorrhage does not typically lead to permanent vision loss and the blood usually drains from the eye of its own accord, but can take several weeks.
There is currently no cure for diabetic retinopathy, but careful management and strict control of the underlying diabetes can help limit severity and slow its progression.
Glaucoma is a genetic (inherited) eye disease, caused by high pressures in the eye which leads to damage to the optic nerve. In some cases, injury or illness can also cause glaucoma.
Symptoms typically don’t start until well into adulthood. The condition is usually painless and affects both eyes, but can be worse in one eye.
Fluid within the eye (aqueous humour), normally flows in and out of different chambers and channels, keeping the eye healthy. In some cases, there can be an overproduction of fluid or the channels become blocked, preventing fluid from moving correctly. This can cause a build-up of fluid, increasing the intraocular pressure (IOP).
The increased pressure starts to damage the optic nerve, which connects the eye to the brain. Over time, damage to these cells can cause irreversible loss of vision. For more information and support, visit Glaucoma Australia (link opens in new window).
There are two main types of glaucoma, but there are several others which occur less frequently:
Primary Open-Angle Glaucoma (POAG)
Accounting for around 90% of cases in Australia, POAG is usually painless and has no obvious signs in the early stages. Loss of peripheral (side) vision is usually one of the signs, causing “tunnel vision”.
Many people do not notice the onset of symptoms until the condition is established, by which point, the damage is usually irreversible.
Acute Closed-angle Glaucoma
This type of glaucoma comes on suddenly, causing severe pain in the eyes, headaches, nausea, vomiting, watering eyes and blurred vision.
Immediate treatment (within 24-48 hours) is necessary to prevent further damage and loss of vision.
Left untreated, glaucoma can cause blindness and early detection is critical to reduce the progression or severity of the disease.
Glaucoma risk factors
There are a number of risk factors for glaucoma, including (but not limited to):
- Family history
- Are of African or Asian descent
- Age – being 50+ (there is also a form of glaucoma that you can be born with)
- Live with diabetes
- Previously had eye surgery or received an eye injury
Treatment and management
There is currently no cure for glaucoma and any sight already lost cannot be restored. Vigilance and early detection, especially if you are in a higher risk category, is the key to retaining sight.
Treatment to lower the pressure within the eye can slow or in some cases, prevent the progression of the condition and reduce vision loss. Treatment is commonly through eye drops to regulate the production of and flow of liquid into and out of the eye. Laser treatment or surgery are alternative options for treatment if the condition cannot be controlled through medication.
Hemianopia is a condition which affects the brain, rather than eyes, resulting in loss of half vision in either the right or left sides of both eyes. It is typically caused by an acquired brain injury, such as through stroke, injury or a brain tumour.
People with a hemianopia can experience difficulty coordinating their movements and undertaking everyday tasks due to missing visual information about half their world.
Depending on its cause, the condition can be temporary and resolve of its own accord. But in some cases, the damage is permanent and irreversible. Specialist therapies and training can help with visual processing and using remaining vision more effectively.
Keratoconus is a degenerative eye condition usually first appearing during adolescence and young adulthood. It causes the clear front surface of the eye (the cornea) to thin and develop a cone-like bulge. The bulging cornea affects the way light hits the retina at the back of the eye, causing distorted vision.
Symptoms begin slowly and can be hard to detect and include distorted, ghosting or blurred vision.
Leber’s Congenital Amaurosis (LCA)
Leber’s Congenital Amaurosis (LCA) is an inherited eye condition, which appears at birth or in the first few months of life. This degenerative disease which progresses over time, is caused by the abnormal development of light-sensitive cells in the retina. It results in very reduced vision or blindness.
Macular Degeneration is a condition affecting the central area of the retina called the macula. The macular is responsible for detailed vision, for uses such as reading.
Macular Degeneration damages the central vision, but side or peripheral vision remains intact. For example, sufferers may be able to see the outline of a clock, but not the numbers or hands. There are both ‘wet’ and ‘dry’ forms of Macular Degeneration. People with Macular Degeneration may experience difficulty reading, writing, seeing colours, watching television and recognising faces, but devices such as magnifiers and additional lighting can help improve this.
Nystagmus is an involuntary oscillation or movement of the eyes. The eyes most often move from side to side, but they may also move up and down, around in circles or a combination of these movements. It is usually present in both eyes and can occur alone or together with another vision problem such as congenital cataracts, strabismus or albinism. Nystagmus causes blurred vision and reduces depth perception.
Optic Nerve Atrophy
Optic nerve atrophy is when damage occurs to part or all of the optic nerve fibres. This results in permanent loss of part or all of the nerve function. The optic nerve carries electrical impulses from the retina to the brain, which translates the message into what we see. Affect on vision ranges from almost normal visual acuity to complete blindness. People with optic nerve atrophy may also develop nystagmus.
Optic Nerve Hypoplasia
Optic nerve hypoplasia occurs when the optic nerve is underdeveloped or even missing. It may occur in combination with other brain and endocrine (system of glands that secrete hormones) abnormalities. Affect on vision ranges from almost normal visual acuity to complete blindness and may affect one or both eyes.
Optic Neuropathy is a disease, generally non-inflammatory, of the eye, where there has been destruction of the optic nerve tissues. Causes include an interruption in the blood supply, compression by a tumor or aneurysm, a nutritional deficiency, and toxic effects of chemical. The disorder, which can lead to blindness, usually affects only one eye.
Retinitis Pigmentosa (RP) is one of the more common genetic eye conditions which causes the retina to slowly and progressively deteriorate. This causes vision to slowly and progressively decrease. One of the first symptoms of RP is difficulty seeing in dark places or at night. There then follows a loss of peripheral (side) vision, which means that the field of vision gets narrow and is often referred to as “tunnel vision”.
People with RP may also become sensitive to light and glare. The symptoms of RP usually increase with time. The condition develops between the ages of ten and 30 years as this is typically when symptoms begin to show.
Retinoblastoma is a fast growing childhood cancer of the eye, which develops in the cells of the retina. If it is left untreated, it can spread through the optic nerve to the brain and may be fatal. However the tumour itself is very treatable and recovery rates are good. Treatment can require complete removal of the eye (enucleation) and may need radiation therapy to prevent spread of the tumour.
Retinopathy of Prematurity
Retinopathy of Prematurity (ROP) appears soon after birth, generally in premature infants exposed to high oxygen levels. The combination of high oxygen and immature blood vessels gives rise to the abnormal development of blood vessels in the retina and can lead to retinal detachment and blindness. Sometimes there is a small area of healthy retina which remains, to give the person some useful vision.
Stargardt’s Macular Dystrophy
Stargardt’s Macular Dystrophy (SMD) is a hereditary condition, which affects the macular of the retina. Central vision is usually affected first with progressive vision loss over a period of years.
Symptoms are usually first noticed between the ages of six and 20 years of age. However, in some people it may not cause problems with sight until they are 30 or 40 years old. SMD is an inherited disease, which affects males and females equally.
If you have concerns about your own or someone else’s vision, please see your ophthalmologist in the first instance. If necessary, they can refer you for a low vision vision assessment by our Orthoptics Team.