Anatomy of the Eye
Our eyes might be small, but they provide us with what many people consider to be the most important of our senses - vision.
How vision works
Vision occurs when light enters the eye through the pupil. With help from other important structures in the eye, like the iris and cornea, the appropriate amount of light is directed towards the lens. Just like a lens in a camera sends a message to produce a film, the lens in the eye 'refracts' (bends) incoming light onto the retina. The retina is made up by millions of specialised cells known as rods and cones, which work together to transform the image into electrical energy, which is sent to the optic disk on the retina and transferred via electrical impulses along the optic nerve to be processed by the brain. Anatomy of the eye
What makes up an eye
Iris: regulates the amount of light that enters your eye. It forms the coloured, visible part of your eye in front of the lens. Light enters through a central opening called the pupil.
Pupil: the circular opening in the centre of the iris through which light passes into the lens of the eye. The iris controls widening and narrowing (dilation and constriction) of the pupil.
Cornea: the transparent circular part of the front of the eyeball. It refracts the light entering the eye onto the lens, which then focuses it onto the retina. The cornea contains no blood vessels and is extremely sensitive to pain.
Lens: a transparent structure situated behind your pupil. It is enclosed in a thin transparent capsule and helps to refract incoming light and focus it onto the retina. A cataract is when the lens becomes cloudy, and a cataract operation involves the replacement of the cloudy lens with an artificial plastic lens.
Choroid: the middle layer of the eye between the retina and the sclera. It also contains a pigment that absorbs excess light so preventing blurring of vision.
Ciliary body: the part of the eye that connects the choroid to the iris.
Retina: a light sensitive layer that lines the interior of the eye. It is composed of light sensitive cells known as rods and cones. The human eye contains about 125 million rods, which are necessary for seeing in dim light. Cones, on the other hand, function best in bright light. There are between 6 and 7 million cones in the eye and they are essential for receiving a sharp accurate image and for distinguishing colours. The retina works much in the same way as film in a camera.
Macula: a yellow spot on the retina at the back of the eye which surrounds the fovea.
Fovea: forms a small indentation at the centre of the macula and is the area with the greatest concentration of cone cells. When the eye is directed at an object, the part of the image that is focused on the fovea is the image most accurately registered by the brain.
Optic disc: the visible (when the eye is examined) portion of the optic nerve, also found on the retina. The optic disc identifies the start of the optic nerve where messages from cone and rod cells leave the eye via nerve fibres to the optic centre of the brain. This area is also known as the 'blind spot’.
Optic nerve: leaves the eye at the optic disc and transfers all the visual information to the brain.
Sclera: the white part of the eye, a tough covering with which the cornea forms the external protective coat of the eye.
- Rod cells are one of the two types of light-sensitive cells in the retina of the eye. There are about 125 million rods, which are necessary for seeing in dim light.
- Cone cells are the second type of light sensitive cells in the retina of the eye. The human retina contains between six and seven million cones; they function best in bright light and are essential for acute vision (receiving a sharp accurate image). It is thought that there are three types of cones, each sensitive to the wavelength of a different primary colour – red, green or blue. Other colours are seen as combinations of these primary colours.
Age-related macular degeneration (AMD)
Age-related macular degeneration (AMD) involves damage to the macula and affects central vision.
How AMD affects vision
The macula is a small, but extremely important area located at the centre of the retina, the light-sensing tissue that lines the back of the eye. It is responsible for seeing fine details clearly. If you have AMD, you lose the ability to see fine details, both close-up and at a distance. This affects only your central vision. Your side, or peripheral, vision usually remains normal. For example, when people with AMD look at a clock, they can see the clock’s outline but cannot tell what time it is; similarly, they gradually lose the ability to recognise people’s faces.
Types of AMD
There are two types of AMD. Most people (about 75%) have a form called “early” or “dry” AMD, which develops when there is a build-up of waste material under the macula and thinning of the retina at the macula. Most people with this condition have near normal vision or milder sight loss. A minority of patients with early (dry) AMD can progress to the vision-threatening forms of AMD called late AMD. The commonest form of late AMD is “exudative” or “wet” AMD. Wet AMD occurs when abnormal blood vessels grow underneath the retina. These unhealthy vessels leak blood and fluid, which can prevent the retina from working properly. Eventually the bleeding and scarring can lead to severe permanent loss of central vision, but the eye is not usually at risk of losing all vision (going 'blind') as the ability to see in the periphery remains. There is a rarer form of late AMD called geographic atrophy, where vision is lost through severe thinning or even loss of the macula tissue without any leaking blood vessels.
Treatments for AMD
We provide intravitreal injections (injections into the eye) for wet AMD using a medicine called ranibizumab (also known as Lucentis, the brand name). Ranibizumab is one of a group of anti-VEGF medicines which, when injected into the eye on a regular basis, can stop the abnormal blood vessels growing, leaking and bleeding under the retina. Most people with wet AMD need to have these injections several times a year, so we now provide the service in several of our satellite locations, as well as at our main hospital, so that patients can get their care closer to home. Laser treatment is also available for AMD, but is not effective for most cases. There is currently no treatment for dry AMD.
Amblyopia (Lazy Eye)
Amblyopia develops in childhood and results in reduced vision in one eye.
What is amblyopia?
Amblyopia happens when one eye is used less than the other from birth to seven years of age, which leads the brain to prefer the better eye. Rarely, as a result of a strong glasses prescription, amblyopia may affect both eyes. What causes amblyopia?
Amblyopia can be caused by:
- A turn in the eye (a strabismus or squint)
- A difference in the glasses prescription between the two eyes
- An obstacle blocking visual stimulation to the eye, such as a droopy eyelid or cataract (cloudy lens); the amblyopia might persist even after the obstacle has been removed
Treatment for amblyopia
Glasses can help and should be worn full-time. A patch covering the good eye will stimulate the weaker eye. The length of time the patch needs to be worn depends on how bad the vision is and on the age of the child. If glasses are worn, the patch should be worn under the glasses, but sometimes, when the vision has started to improve, the patch can be worn on the glasses. In some cases, particularly if the child cannot wear a patch, special eye drops can be used to blur the vision in the good eye. Most cases of amblyopia are treatable. However, the success of treatment is dependent on the initial level of vision your child has in the bad eye, their age and the level of co-operation with treatment. It is very important to detect and treat amblyopia as early as possible to get the best possible vision. If it is not treated, the vision in that eye will be permanently impaired, so it very important that you try really hard to follow the instructions given by your child’s doctor or orthoptist. We know that children do not always understand why they need to cover their good eye and treatment can be difficult. Give lots of praise when the patch is worn well and be ready to distract your child’s attention to prevent the patch being pulled off. Your orthoptist is very experienced in dealing with children who have amblyopia and can advise you about carrying out the treatment at home as effectively as possible. Amblyopia is most successfully treated before seven years of age. After this, the eyes and brain become too mature to change. Later attempts to treat are difficult and might not be successful.
Blepharitis is inflammation of the rims of the eyelids, which causes them to become red and swollen.
What is blepharitis?
Blepharitis is inflammation of the rims of the eyelids, which causes them to become red and swollen. It is a common condition which can develop at any age but is more common in young children and people over 50. Most people experience repeated episodes followed by periods with no symptoms. It is not possible to catch blepharitis from someone else who has it.
How blepharitis affects you
The symptoms of blepharitis can include: burning, soreness or stinging in the eyes; crusty eyelashes and itchy eyelids. It can also cause lid cysts (chalazion). The cause of blepharitis is not known in most cases but, although it is not an infection, it can be caused by a reaction to the bacteria that live naturally on the eyelid skin. It is more common in skin conditions such as: Seborrhoeic dermatitis, which causes an itchy rash on the skin and scalp (seborrhoeic dermatitis of the scalp is called dandruff). Rosacea which causes the face to appear red and blotchy. Acne in teenager and young adults, which cases irritation and blockage of the glands in the centre of the face Blepharitis is not usually serious, but can produce a lot of symptoms and can make people unable to wear contact lenses comfortably. Many people with blepharitis also have dry eye condition where the eyes do not produce enough tears or dry out too quickly. Serious complications, such as sight loss, are rare, particularly if recommended advice is followed.
Treatment for blepharitis
Blepharitis is usually a long-term (chronic) condition, which means once it develops it can cause repeated episodes. There is no cure for blepharitis, but establishing a daily eyelid-cleaning routine can help control the symptoms and any dryness can be treated with artificial tear drops. Lid cleaning often needs to be continued indefinitely to prevent recurrence. More severe cases of blepharitis may require treatment with antibiotic ointment applied to the eyelids or, antibiotic drops for the eyes and, in a few cases, steroid eye drops. Some patients benefit from antibiotics by mouth, particularly when the blepharitis is associated with a skin condition such as rosacea, These antibiotics are usually required for at least four to six weeks and may need to be continued for many months.
A cataract is clouding or opacity of the lens inside the eye. It causes gradual blurring of vision and often glare.
How cataract affects vision
Inside your eye, behind the iris and pupil is a lens. In a normal eye, this lens is clear. It helps focus light rays on to the back of the eye (the retina), which sends messages to the brain allowing us to see. When cataract develops, the lens becomes cloudy and prevents the light rays from passing on to the retina. The picture that the retina receives becomes dull and fuzzy. Cataract usually forms slowly and most people experience a gradual blurring of vision.
Causes of cataract
Most forms of cataract develop in adult life. The normal process of ageing causes the lens to harden and become cloudy. This is called age-related cataract and it is the most common type. It can occur at any time after the age of 40. Although most cataracts are age related, there are other types, including congenital (present at birth), drug induced (steroids), and traumatic (injury to the eye). Cataract is also more common in people who have certain diseases such as diabetes.
Treatments for cataract
Surgery is the only available treatment for cataract and is very effective, straight-forward and quick for the vast majority of patients. We advise patients to have surgery when their cataract progresses to the point that it is interfering with daily activities or lifestyle – but it is usually safe to delay surgery if you do not feel that you have a problem with your vision or do not wish to have surgery.
A chalazion is a common condition affecting your eyelids. The condition often occurs due to inflammation around the opening of the oil glands at the base of your eyelashes. This is called blepharitis.
The inflammation is caused by a sensitivity to a common bacteria found on your skin. When the openings of the small oil glands around your lashes become blocked by inflammation, a small tender swelling will occur in the lid. This is known as a chalazion. The chalazion will often vary in size over a few weeks and can discharge spontaneously after hot compresses and lid cleaning. A small proportion of the chalazia will form hard lumps on the eye lid, which, if present for a few weeks can be incised and drained under local anaesthetic. Sometimes the chalazion may cause a spreading infection along the surface of your lid, which might need a course of oral antibiotics, but this is rare.
How to prevent a chalazion
To prevent a chalazion from developing, daily lid cleaning is recommended. A warm wet flannel with a few drops of baby shampoo should be used to clean your eyelids before going to sleep at night. An antibiotic ointment is often prescribed to rub into the base of your lashes at night once your lids are clean.
Conjunctivitis is a common condition which causes the surface of your eye to go red and, often, sticky or watery and your eye becomes sore.
Types of conjunctivitis
Conjunctivitis can be caused by infection from bacteria, viruses or other organisms, and also by allergy or inflammation. Viral conjunctivitis tends to cause a watery red eye and can last for two to three weeks even with the correct treatment. In most cases viral conjunctivitis does not affect your vision but rarely you might notice your vision becomes blurry or you may see glare when looking at lights. This is due to an inflammatory reaction causing small white dots on the cornea, the transparent window at the front of the eye. These usually fade with time, but it can take a few weeks or even months. Bacterial conjunctivitis is more likely to cause a red eye with a sticky yellow discharge.
Treatments for conjunctivitis
There is no antiviral medication for viral conjunctivitis and it does not respond to antibiotic drops as it is not caused by bacteria. The best treatment for viral conjunctivitis is to use artificial tears and simple painkillers, with regular lid cleaning and cold compresses. The conjunctivitis disappears when your body becomes immune to the virus and fights the germs off, just as in a cold or 'flu. Very rarely, steroid drops are given for severe cases of viral conjunctivitis or when the cornea is affected. Antibiotic drops can be helpful in cases of bacterial conjunctivitis and are often prescribed for a one or two-week course. Contact lenses should not be worn during any type of conjunctivitis.
Preventing conjunctivitis from spreading
Conjunctivitis is contagious and spreads very easily by water droplets (coughing, sneezing) or contact with tissues, flannels, towels, pillowcases and so on. For that reason, it’s really important to wash your hands frequently and dispose of tissues after use to prevent the condition from spreading to other family members or work colleagues.
A corneal abrasion is a scratch on the clear part of the front of your eye.
About corneal abrasions
Corneal abrasions are a small scratch on the cornea, the clear window at the front of the eye. They are generally a result of trauma (injury) to the surface of the eye. Common causes include a fingernail scratching the eye, walking into something, and getting grit in the eye, particularly if the eye is then rubbed. Injuries can also be caused by contact lens insertion and removal.
How a corneal abrasion affects vision
Abrasions are very painful because there are many nerves that supply the cornea.The pain gets better as your eye heals, but this can take between 24 and 48 hours.If the abrasion involves the central part of your cornea, your vision could also be temporarily affected.Apart from the pain, your eye might be watery, red and sensitive to light. If your eye becomes increasingly red or painful after treatment or your sight becomes much more blurred, you should see an eye doctor again or contact the hospital.
Treatment for a corneal abrasion
Treatment generally involves a thorough examination of your eye and lids, to check for any trapped foreign body or grit and ensure there is no serious eye injury, followed by drops or ointment and, sometimes, an eye pad.If you are given an eye pad, you will need to keep it on for between 12 and 24 hours; if you find this uncomfortable,you can take it off and use sunglasses instead. You should also note the following:
- You may take ordinary pain killers, such as paracetamol, to help with the pain
- Avoid rubbing or touching your eye
- If you wear contact lenses, don’t use them until your eye is completely healed;you need to see your contact lens practitioner after finishing treatment for your abrasion before you wear your contact lenses again If you are asked to use drops or ointments, please follow these steps:
- Lie down, or lean your head back, and look up
- Use a clean finger to gently pull down your lower eyelid to create a pocket
- If you are using eye drops, gently squeeze them into the pocket you have created,not directly onto your eye
- If you are using ointment, apply a small strip into the pocket
- Blink to spread the medication over your eye If your eye becomes increasingly red or painful after treatment or your sight becomes more blurred, you should see an eye doctor again or contact the hospital.Remember though that if the eye doctor put in pupil dilating (enlarging) drops, your sight will normally be blurred for 12-24 hours after these were put in.
Diabetic retinopathy is a complication of diabetes, and causes damage to the blood vessels in the retina.
Causes of diabetic retinopathy
Many diabetics – particularly those with poor diabetic control which results in too-high blood sugar levels over long periods of time – have damaged blood vessels in the retina, the tissue lining the back of the eye that detects light and allows us to see. This condition, called diabetic retinopathy, affects up to eight out of 10 patients who have had diabetes for 10 years or more.
Types of diabetic retinopathy
Many people with mild diabetic retinopathy have good vision, but there are two types of sight-threatening diabetic retinopathy: diabetic macular oedema (DMO) and proliferative diabetic retinopathy (PDR). In DMO, fluid leaks out of the tiny damaged blood vessels in the back of the eye, and accumulates in the macula, the central part of the retina which is responsible for seeing fine details and central vision. This leads to swelling of the tissue and blurred vision. Eventually, patients with diabetic macular oedema can develop poor central vision and be unable to read or drive, but the vision to the side usually remains normal. Proliferative diabetic retinopathy is when the retinal blood vessels close resulting in the retina being starved of blood. This causes abnormal and very fragile blood vessels to grow on the surface of the retina which can lead to permanent loss of vision from bleeding into the eye, retinal scarring and retinal detachment.
Treatment for diabetic retinopathy
Regular eye checks are essential for all diabetics, so signs of diabetic retinopathy can be detected as early as possible. If you diabetic and experience blurred vision, you should visit an eye specialist immediately. If you develop DMO, you might require laser photocoagulation, which involves placing tiny laser burns in the area of leakage in the retina which slow the leakage of fluid and reduce the fluid in the eye. This may not significantly improve vision for some patients – although it can stop your vision from getting worse. Other treatments are available and have been shown to benefit patients with DMO, including injections of anti-VEGF drugs such as bevacizumab and ranibizumab. Ask your specialist if these treatments are suitable for you or available to you.
An epiretinal membrane is a thin sheet of fibrous tissue that develops on the surface of the macula and can cause problems with central vision.
What is an epiretinal membrane?
If you think of your eye as a camera, the retina is like the photographic film. It is a very thin layer of tissue, which is sensitive to the image focused on it, and sends information to the brain. At the very centre of the retina is the macula. This is a very special area of the retina, which we use for reading and recognising complex shapes. Sometimes, scar tissue forms which grows across the macula. As the membrane contracts, it causes distortion of the retinal tissue. If this happens, the macula cannot work normally. This affects the vision, particularly for reading and other visually demanding tasks, but it does not cause total blindness.
What causes an epiretinal membrane?
Most epiretinal membranes happen because the vitreous (the jelly inside the eye) pulls away from the retina. This most commonly happens to people over the age of 50. The membrane may also form following eye surgery or inflammation inside the eye. How epiretinal membranes affect vision While the scar tissue is developing, it does not appear to affect your vision. However, when it stops growing, it contracts (shrinks) and causes distortion of your central vision – for example, straight lines appear wavy or crooked in appearance, and reading is difficult. Depending on the severity of this distortion, you might notice a substantial loss of central vision.
Treatment for an epiretinal membrane
The only way to treat an epiretinal membrane is by having an operation called a vitrectomy. Eye drops or glasses are not effective. During the vitrectomy, the surgeon makes tiny cuts in your eye and removes the vitreous from inside. They then grasp and gently peel away the epiretinal membrane from the retina. We usually put small stitches in the eye. These dissolve naturally over about four to six weeks. At the end of the operation, we usually put a pad and shield over your eye to protect it. These will be removed the morning after your surgery. Your doctor will help you to decide if surgery is appropriate for you. The main reason to proceed with the operation is to attempt to correct the distortion of your central vision. If you are not aware of any visual problems, you might not need to have surgery. However, if the distortion affects your ability to work, drive, read, or perform other important activities, you should consider having an operation. Some patients decide not to have an operation and accept the distorted central vision in the affected eye. This is reasonable, especially if the vision in the other eye is not affected. There is no “right” or “wrong” decision, as every person has different needs and priorities. In general, you should only go ahead with surgery if you find the distortion of your vision troublesome at the moment, and not as a preventative measure.
Flashes and Floaters
Flashes of light or black floaters that look like spiders or tadpoles and move around as you move your eye are quite commonly seen by people with normal eyes.
Causes of flashes and floaters
Flashes and floaters happen because of changes in the vitreous, the clear, jelly-like substance that fills the inside of your eyeball. The vitreous jelly shrinks as you get older, and slowly pulls away from the inside surface of the eye. This shrinking and separation or detachment of the vitreous from the retina is a common phenomenon, particularly in people over 50 years of age, and causes no retinal damage in nine out of 10 patients. It is known as a posterior vitreous detachment.
Treatment for flashes and floaters
Flashes and floaters rarely lead to any serious complications, so you generally don’t need any treatment for them. If they are troublesome, the effect of floaters might be minimised by wearing dark glasses. This will help especially in bright sunlight or when looking at a brightly lit surface. In many cases, the flashes disappear with time and the floaters get less noticeable as your brain adjusts to the jelly change. If your flashes or floaters become much worse, you should consult your GP, your optometrist (optician) or visit our specialist A&E department to exclude any serious problems. If you see a black shadow or curtain effect or you suddenly loose vision, you should go to your nearest A&E without delay.
Glaucoma is an optic nerve disease. Optic nerve consists of ganglion cells that carry signals from the eye towards the brain. The nerve damage in glaucoma involves loss of retinal ganglion cells in a characteristic pattern. Raised pressure within the eye ball (above 21 mmHg) is the most important and modifiable risk factor for glaucoma. However, some may have high eye pressure for years and never develop damage, while others can develop nerve damage at a relatively low pressure. Untreated glaucoma can lead to permanent damage of the optic nerve and resultant visual field loss, which over time can progress to blindness. Glaucoma is considered as "silent thief of sight" because the loss of vision often occurs gradually over a long period of time. The central vision is usually preserved in the early stages of the disease due to which the disease remains unnoticed until the advanced stages till the central vision is also lost. Some patients even do not notice the loss of vision in one eye until the second eye also gets severely damaged. Once lost, vision cannot normally be recovered, so treatment is aimed at preventing further loss. If the condition is detected early enough, it is possible to slow the progression with medicines, lasers and surgical means. Important risk factors for glaucoma include increased eye pressure, trauma, refractive errors (farsightedness or nearsightedness), eye inflammation, diabetes, family history of the disease and use of steroids. Although the disease usually affect the people after 40 years of age but it can also occur in younger individuals specially if any of the above risk factors are present. A type of glaucoma can even be present at the time of birth (congenital glaucoma).
TESTS OF GLAUCOMA:
The eye is numbed via eye drops after which the examiner uses a tonometer to measure the inner pressure of the eye.
Eye drops are used to numb the eye after which a contact lens with a mirror is placed gently on the eye to see the angle between the cornea and the iris. This test usually helps to distinguish between open and closed angle types of glaucoma. It also helps to plan the management of glaucoma.
Keratoconus is a non-inflammatory eye condition in which the normally round dome-shaped clear window of the eye (cornea) progressively thins causing a cone-like bulge to develop.
What is keratoconus?
Keratoconus is an eye condition in which the normally round dome-shaped clear window of the eye (cornea) progressively thins causing a cone-shaped bulge to develop. Exactly why this happens is unknown, but genetic factors play a role and it is more common in people with allergic diseases such as asthma, in Down's syndrome and in some disorders of connective tissue such as Marfan's disease. It affects up to one in 1,000 people and is more common in people of Asian heritage. It is usually diagnosed in teenagers and young people.
How kerataconus affects vision
The change in shape and thinning of the cornea and, in later stages, scarring causing loss of transparency of the cornea impairs the ability of the eye to focus properly, causing poor vision.
Treatments for keratoconus
In the early stages, spectacles or soft contact lenses may be used to correct vision. As the cornea becomes thinner and steeper, rigid gas permeable (RGP) contact lenses are often required to correct vision more adequately. In very advanced cases, where contact lenses fail to improve vision, a corneal transplant may be needed. Changes caused by keratoconus can take many years to develop. For this reason we monitor those with the condition and invite them back for repeat assessments for up to five years from an initial visit. When a person with keratoconus attends a clinic, the following tests might be performed; 1. Vision (reading chart) 2. Refraction (spectacle test) 3. Corneal scan (Pentacam) Any necessary contact lens checks will also be undertaken. The results are compared with those from your previous visits. If the results are getting steadily worse, we will discuss with you whether you need to undergo corneal cross-linking (CXL). CXL is a new treatment that can stop keratoconus getting worse. It is effective in more than nine out of 10 patients, with a single 30-minute day-case procedure, but it is only suitable where the corneal shape is continuing to deteriorate. Beyond a certain stage, if the cornea is too thin, it could be unsafe to perform the procedure. Usually in people in their late 30s, the cornea naturally stiffens and CXL is generally not required. Below this age, the cornea is more flexible and disease progression (and worsening vision) are more likely to occur.
A macular hole is a small hole in the macula which is in the centre of the retina.
What is a macular hole?
If you think of your eye as a camera, the retina is like the photographic film. It is a very thin layer of tissue, which is sensitive to the image focused on it, and sends the information to the brain. At the very centre of the retina is the macula. This is a very special area of the retina, which we use for reading and recognising complex shapes. Sometimes, a hole forms in the macula, which prevents it from working normally. This affects your vision, particularly for reading and other visually demanding tasks, but it does not cause total blindness.
Treatment for a macular hole
The only way to treat a macular hole is an operation. Eye drops or glasses are ineffective. Some patients decide not to have an operation and accept the poor central vision in the affected eye. This is reasonable, especially if the vision in the other eye is not affected. There is no “right” or “wrong” decision as every person has different needs and priorities. You should discuss your reasons for wanting to proceed with an operation, or for deciding not to have surgery, with your consultant. The operation to repair your macular hole is called a vitrectomy and usually takes about an hour.The procedure will be supervised by an experienced surgeon, who will either perform the surgery themselves or oversee a more junior surgeon who might undertake part or all of the operation.
What is the retina?
The retina lines the inside of the back of the eye. It functions a bit like the film in the back of a camera, in that it absorbs light to form an image of the outside world. The most important part of the retina is the macula this is the part of the retina that the light is focused on. It gives the central vision that is important for fine visual tasks such as reading and driving.
What is a retinal detachment?
A retinal detachment occurs when a break in the retinal allows fluid to pass under the retina, so that the retina peels away from the back of the eye. It is a serious eye emergency and without treatment it can cause blindness in the affected eye. If you are diagnosed with a retinal detachment it is important that you see an eye doctor (ophthalmologist) immediately. You may then be referred to an ophthalmologist who is also trained as a retinal surgeon, such as myself. Most people develop a retinal detachment spontaneously, that is, it is not caused by anything they have done. It is more common in people who are shortsighted (myopic).
What are the symptoms of retinal detachment?
People often notice spots floating in their vision (floaters), or flashing lights, in the period leading up to a retinal detachment. As the retina detaches it causes an enlarging blind spot that may progress to involve the macula. When this occurs the central vision is much reduced (called a macular-off detachment). Some small retinal detachments that haven't affected the macula (macular-on detachments) may go unnoticed and be picked up during a routine eye examination by an optician. In summary, the key symptoms are flashing lights, floaters, bits missing from the vision, or 'curtains' coming over this vision.
Do I need surgery?
Most patients with retinal detachments are advised to undergo surgery as retinal detachments seldom go away, and many progress to cause severe or total loss of vision in the affected eye. Very occasionally, longstanding detachments are kept under regular review or treated with laser.
What does surgery involve?
Patients usually require one of two types of operation: either cryobuckle surgery or vitrectomy. Cryobuckle surgery involves putting a silicone splint (explant/buckle) onto the outside of the eye to push the outside layers of the eye back into contact with the detached retina. The buckle is not normally visible as it is hidden under the skin of the eye (conjunctiva), and the eyelids. The retinal break is then sealed with a laser or freezing probe (cryoprobe). Victrectomy involves operating inside the eye and removing the clear gel (vitreous) that fills the cavity of the eye. The retina is pushed back into position with a bubble of gas, and the hole is sealed with a laser or cryoprobe. The gas bubble absorbs with time but whilst it is in the eye the patient is usually asked to keep their head in a particular position, to float the retina into the correct position. Surgery can be undertaken under a local anaesthetic (the patient is awake but with an injection to numb the eye), or general anaesthetic (asleep), and takes from about 30 minutes up to 2 hours, although most operations take about an hour. It may also be recommended that you have laser or cryoprobe treatment to any weak areas in the other, unaffected eye, to reduce the risk of detachment.
What are the benefits of retinal detachment surgery?
This depends on the type of retinal detachment. If the macula is still attached, the aim is to prevent severe, central, vision loss. If the macula has already become detached then surgery aims to improve vision, but it seldom improves back to normal.
What are the risks of retinal detachment surgery?
All eye operations carry the risk of visual loss and this is true of retinal detachment surgery, however, severe surgical complications such as haemorrhage or infection are thankfully very rare (about 1 in 500 patients are affected). The most common problem is that the retinal detachment persists, or recurs, and further surgery is required to re-attach the retina. This is not uncommon, with 10-20% of patients requiring more than one operation to attach the retina. Even if patients may require more than one operation the good news is that most retinas (more than 95%) can be attached. In addition, those patients who require vitrectomy will usually go on to develop cataract and this usually requires surgery at some time. Those who have cryobuckle surgery may get double vision, but this usually settles.
Are there any particular precautions after surgery?
A nurse will go through the general instructions for someone who has just had an operation such as keeping the eye clean, use of eye drops, and follow up appointments. For those that had a vitrectomy there are additional instructions. Firstly they must not go up to high altitude as the gas in the eye will expand and this puts the eye pressure up. Hence they cannot fly, or go up high mountains until the gas absorbs, and this can take 1-2 months depending on what type of gas is used. Secondly, if they need a general anaesthetic they must inform the anaesthetist that they have gas in the eye, to avoid certain anaesthetic gases.
Any further questions?
Retinal detachment is a serious diagnosis that often comes as a shock. In addition, surgery is often performed relatively urgently so you may feel there is not much time to consider the options. For this reason it is important to ask questions. If you drive you should check with us whether it is safe to continue.
Retinal Vein Occlusion
A retinal vein occlusion occurs when a blood clot forms in a retinal vein.
What is a retinal vein occlusion?
Retinal vein occlusion is a common cause of sudden painless reduction in vision in older people. It occurs when a blood clot forms in the blood vessels of your retina, the layer of light sensitive nerves that lines the inner surface of the back of your eye. A blockage in one of the veins prevent blood from escaping out of the eye and causes blood and fluid to leak into the retina, with bruising and swelling as well as lack of oxygen at the back of the eye. This interferes with the ability of the retina to detect light and reduces vision. The condition is uncommon under the age of 50, but becomes more frequent in later life.
There are two types of retinal vein occlusion:
- Branch retinal vein occlusions are due to blockage of one of the four retinal veins, each of which drains about a quarter of the retina
- Central retinal vein occlusion is due to blockage of the main retinal vein, which drains blood from the whole retina In general, visual loss is more severe if the central retinal vein is blocked.
What causes retinal vein occlusion?
A clot forms in the vein and obstructs the blood flow. The exact cause is unknown, but several conditions make the condition more likely. These include:
- High blood pressure
- High cholesterol
- Certain rare blood disorders
Prevention and treatment
It is essential to identify and treat any risk factors to reduce the risk to the other eye and prevent a further vein occlusion in the affected eye. Treatment of the risk factors listed above also reduces the risk of other blood vessel blockages such as may happen in a stroke (affecting the brain) or a heart attack or, in those with rare blood disorders, a blocked vein in the leg (deep vein thrombosis)or lung (pulmonary embolism). Persistent bruising and swelling at the centre of the retina is the main cause of permanent loss of central vision. Laser treatment is sometimes helpful in restoring some central vision in branch retinal vein occlusions. This treatment is normally recommended at about three months after the occlusion. About three in 10 patients with retinal vein occlusions develop abnormal blood vessels growing on the iris at the front of the eye or on the retina. These abnormal blood vessels can bleed or cause a marked pressure rise in the eye leading to further loss of vision. This can normally be prevented by laser treatment to the retina. This treatment is most effective if applied before vision is lost. For this reason, patients with central retinal vein occlusions are normally checked every six to eight weeks for six months. There is extensive research into a number of new injection treatments to either improve blood flow out of the eye or reduce bruising and swelling. Your doctor will discuss these treatments with you if they are likely to help your eye. The following three tests are frequently recommended for patients with retinal vein occlusion. Retinal photography to help monitor accurately the degree of retinal damage. Fluorescein angiography to determine the need for laser or other treatment. Optical coherence tomography to monitor and help assess the need for and response to treatment Patients with central retinal vein occlusions are checked frequently for about six months and patients with branch occlusions less often. Recurrence or deterioration is unlikely after this and most patients are discharged after one to two years.
A stye is a small abscess (painful collection of pus) on the eyelid and is an infection at the root of an eyelash.
What is a stye?
A stye is a small abcess (painful collection of pus) on the eyelid and is an infection at th root of an eyelash. It appears as a small painful red lump, often with a yellow spot in the middle, on the outside of the eyelid. Other symptoms include a watery eye and a red eye or eyelid. It's not always necessary to see a doctor if you develop a stye, although if you have painful very swollen eyelid with a stye, you should have it checked.
Causes of styes
Styes are fairly common and a person may have one or two styes during their lifetime. Styes are usually caused by an infection with staphylococcus bacteria. If you have been diagnosed with long-term blepharitis (inflammation of the eyelids), this may also increase the risk of styes.
Treatment for styes
Most styes get better without treatment within a few days or weeks. Styes may burst and release pus after three or four days. A warm compress (a cloth warmed with warm water) held against the eye encourages the stye to release pus and heal more quickly. Further treatment is not usually needed unless you have a very painful stye that is not getting better or a very swollen red lid indicating spreading infection. In this case, see your doctor who may decide to treat it with antibiotics, drain it or refer you to an ophthalmologist . You should never attempt to burst a stye yourself.
What is Strabismus?
Strabismus is the medical term for squint, a condition where the eyes point in different directions. One eye may turn inwards, outwards, upwards or downwards while the other eye looks straight. Squint can occur at any age. Squint are common and affect about one in 20 children.
What causes Squint?
- The exact cause is not really known.
- Movement of each eye is controlled by the six muscles. A loss of coordination between the muscles of the two eyes leads to the squint.
- Aquired squint may be caused by the eye attempting to overcome a vision problem such as shortsightedness or long sightedness.
- Genetic factor play a part in many squint.
How Squint affect vision?
- When eyes are not aligned they are focusing on different objects, child would ignore the image from the deviated eye.
- The vision in the deviated eye gradually deteriorates because the brain ignores the weaker image and results in deviation of lazy eye.
- A lazy eye can be treated by patching of the better eye until about six or seven years of age but it is important that it is treated as soon as possible.
- An adult cannot ignore the image and therefore has double vision and develop abnormal head posture.
Types of Squint?
If deviation persists all the time.
If squint appears at certain times they are known as intermittent.
Squint in children need to be assessed as soon as possible to ensure the vision is protected and to improve the chances of successful treatment.
- Glasses can sometimes reduce or completely eliminate the squint.
- Glasses should be worn at all the times to help straighten the eyes.
Patching of the good eye improves the vision in lazy eye.
Prismatic Correction/Fresnel Prism
It is used to relieve diplopia.
- Squint surgery is very common eye operation, it involves tightening or weakening of the muscles to change the eye position by applying absorbable sutures.
- In Young children, surgery develop the coordination of the two eyes to work together for 3D vision (depth).
- Corrective surgery is undertaken to improve the appearance of the eyes, correct double vision and abnormal head posture.
- Surgery is nearly always a day case procedure.
- There are two kinds of squint operation.
- Adjustable Surgery.
- It can be performed in older children and adults. Stitches can be adjusted shortly after the surgery when the patient is awake.
- Complications of surgery are rare.
- Sometimes more than one operation will be needed to correct the squint fully.
Recovery from Surgery
- It can take several weeks to fully recover from corrective squint surgery.
- During this time the eye may feel painful or itchy for a short time and you may have temporary double vision.
- Squint surgery straightness the eye.
- Sometimes after operation the eyes are not perfectly straight.
- It is possible that after several years of successful surgery the squint may gradually return again.
- A further operation is an option to restraighten the eyes.
Facts about Squint
- Squint examination is possible in all children.
- Treatment should be started as soon as possible to ensure the development of the best possible visual acuity and stereopsis.
- Early treatment of strabismus in infancy may reduce the chance of developing amblyopia and depth perception problems.
Uveitis is inflammation of the middle layer of the eye, called the uvea or uveal tract
What is uveitis?
Uveitis is inflammation of the middle coloured (pigmented) layer of the eye, called the uvea or uveal tract. Uveitis usually affects people aged 20 to 59, but it can occur at any age, including in children. Men and women are affected equally. It's estimated that two to five in every 10,000 people will be affected by uveitis in the UK every year. Despite being an uncommon eye condition, uveitis is a leading cause of visual impairment in the UK. It's estimated that the more serious types of uveitis are responsible for one in every 10 cases of visual impairment in the UK. This is why it's very important to confirm a diagnosis of uveitis as soon as possible if you develop symptoms that could be related to the condition, we have a dedicated uveitis service, where patients with acute and chronic disease are seen, and particular expertise is available in the management of complex cases. We can offer advice on all aspects of the medical and surgical management of all patients with these diseases, including children.
How uveitis affects vision and what causes it
The uvea is made up of the iris (coloured part of the eye), the ciliary body (ring of muscle behind the iris) and the choroid (layer of tissue that supports the retina). Uvetis occurs when the uvea becomes inflammed. Common symptoms of uveitis include: pain in one or both eyes; redness of the eye; blurred vision; sensitivity to light (photophobia) and floaters (shadows that move across your field of vision). There are a wide range of potential causes for uveitis. Many cases are thought to be the result of a problem with the immune system, called an autoimmune disorder (where the body's defence against illness and infection attacks the body tissues). Less common causes of uveitis include an infection or injury to the eye.
Types of uveitis
The type of uveitis depends on which part of the eye is affected but the most common forms are: Anterior uveitis – this is inflammation of the iris (iritis) or inflammation of the iris and the ciliary body (iridocyclitis), and is the most common type of uveitis, accounting for about three out of four cases. Intermediate uveitis – this affects the area around and behind the ciliary body. Posterior uveitis – this affects the area at the back of the eye, the choroid and the retina In some cases, uveitis can affect both the front and back of the eye. This is known as panuveitis.
Treatments for uveitis
The main treatment of uveitis is steroid medication (corticosteroids) which can reduce inflammation inside the eye. Several different types of steroid medication may be used, depending on the type of uveitis you have. Eye drops are often used for uveitis affecting the front of the eye, whereas injections, tablets and capsules are more often used to treat uveitis affecting the middle and back of the eye. In some cases, other treatments may also be needed in addition to corticosteroids. These include eye drops to relieve pain or widen (dialte) the pupil, a type of medication called an immunosuppressant, and, rarely, surgery. The sooner uveitis is treated, the more likely the condition can be successfully treated.
Although most cases of uveitis respond quickly to treatment and cause no further problems, there is a risk of complications. The risk is higher in people who have intermediate or posterior uveitis, or who have repeated episodes of uveitis. Complications of uveitis include glaucoma and retinal damage and can cause permanent damage of the eye and loss of vision.
Vitamin A Deficiency
Vitamin A plays an important role in the growth & development of a child. It is vitally important for preservation of night vision. Usually small children are at risk. Poverty, large family size, inadequate child spacing, lack of adequate and balanced food combined with inadequate breast feeding and improper weaning, measles, chronic diarrhea etc. are the major precipitating factors.
What are the symptoms of Vitamin A deficiency?
Usually the child remains ill with repeated attacks of respiratory tract infections (cough), diarrhea, fever, and is very weak or malnourished. When vitamin A deficiency becomes quite server, the eye is involved and the child usually becomes inactive after dark because of night blindness. The child also develops a yellowish white, foamy spot over the white area of eyeball (Bitot's spot). It has been observed that when mothers apply "surma" (antimony powder) to the eyes of such a child, this spot becomes stained by surma ("surma Sign"). As the situation worsens, eye start watering and gradually the cornea (anterior part of the eye melts ways with ultimate loss of sight. Remember, all children with these symptoms are at the brink of death because not only will they become blind but will also suffer from much more serious diseases. In these circumstances, immediately consult any eye specialist.
Prevention & treatment of Vitamin A deficiency
Vitamin A is found is abundance in dark green leafy vegetables, red palm old, yellow fruits (mango, papaya), egg, milk and fish. Regular use of these gives the child enough Vitamin A. The pregnant mothers should also use these sources of vitamin A. Mothers should be encourages to breast feed their children for full two years. Weaning should start at 4 months of age together with use of vitamin a containing foods. Every child must be vaccinated for measles by the age of 9 months. All the pregnant and lactating mothers at risk should also take the adequate dose of vitamin A after consulting the doctor. If you find one child with vitamin A deficiency, look for more children in that area Vitamin A deficiency is life threatening and potentially blinding, save the life and sight of your child.