Nystagmus is an involuntary movement of the eyes, usually from side to side, but sometimes up and down or even in a circular motion, most people with the condition have vision which is much worse than average. For example, many people with it can register as partially sighted and a small number as blind.
Nystagmus which appears in the first six months of life is called early onset, congenital or infantile nystagmus. If the condition develops later, it is known as acquired nystagmus.
In early childhood it can be caused by a defect in the eye or optic nerve, including: cataract, glaucoma, some disorders of the retina and albinism. It can also be found in children who have multiple disability such as Down’s Syndrome.
However, many children with nystagmus have no other health issues. In this case it is called congenital idiopathic nystagmus or idiopathic infantile nystagmus, meaning that the condition is observed, or starts, early in life and the cause is unknown. Some types can be inherited. To find out the chances of someone passing on nystagmus to the next generation, a specialist must first make an accurate diagnosis of the underlying condition. It may then be necessary to consult a clinical geneticist for detailed information and counselling.
Acquired nystagmus, which develops later in life, can be a symptom of another condition such as stroke, multiple sclerosis, concussion, or many others. Nystagmus is not infectious or contagious. Because the condition may be the first sign of a serious disorder, it is vital that an an eye specialist or a neurologist is consulted as soon as symptoms develop.
Nystagmus cannot be cured. Glasses and contact lenses do not correct the condition, although they may help a little and should certainly be worn to correct other sight problems, but the nystagmus will still remain.
Very occasionally, surgery is performed to alter the position of the muscles which move the eye, the purpose of this is to reduce the head tilt. Research has been made into finding ways of reducing nystagmus by making the patient aware of the eye movement and encouraging them to control it. These techniques rely on visual or audio signals (known as bio-feedback). For example, the patient might listen to an electronic signal which goes higher when the eye movement is greater. Some people have said that they benefit from this type of treatment – the evidence is inconclusive.
Interest in Nystagmus among vision scientists is growing. However, a lot of research is still needed to better understand the condition and progress is likely to be measured in decades rather than years.
Over half of people aged 65 or more have some cataract development and most cases can be treated very successfully with surgery. A cataract is where all or part of the lens of the eye is no longer transparent and as a result vision becomes blurred or dim. Cataracts can form at any age, but most develop as people get older. In younger people they can result from an injury, certain drugs, prolonged inflammation or illnesses such as diabetes.
Some things can seem blurred, or any glasses worn can seem dirty or scratched. Cloudiness in the lens can occur in more than one place, this can cause double vision. It may be more difficult to see properly in bright light, or on sunny days. As a cataract develops its centre becomes more yellow, giving everything a yellowish tinge.
The most effective treatment for cataracts is a small operation to remove the cloudy lens. This cannot be performed by laser, although laser treatment is sometimes needed afterwards. Diet or medication have not been shown to slow or stop their development. Usually, it is a matter of personal choice if, and at what stage, to have an operation. It should be remembered that there will probably be a waiting list.
In the past, eye specialists often waited until the cataract became ‘ripe’ before suggesting its removal. Nowadays, with modern surgery, the operation can be carried out at any stage of the cataract’s development. If the visual impairment interferes with reading, work, or leisure activities, then surgery should be seriously considered.
Diabetes can affect the eyes in a number of ways, but usually involves damage to the fine network of blood vessels in the retina in a process known as diabetic retinopathy. Although vision may be good, changes can be taking place in the eyes which mean they need treatment.
Most sight loss in diabetes is preventable providing early diagnosis is made. People with diabetes should have an eye examination every year and not wait until vision has deteriorated enough to warrant a test.
A family doctor, diabetologist or optician can examine for diabetic retinopathy. Photographs are sometimes used to detect abnormalities without the need for any other sort of test. If a problem is found, patients will be referred to a consultant ophthalmologist at a hospital eye clinic.
If found early enough, most sight-threatening problems caused by diabetes can be prevented by laser treatment. It is important to realise however that laser treatment can only save any remaining sight, it cannot make it better. The laser beam can be focused with extreme precision, so that the blood vessels damaging the retina can be closed.
If new blood vessels are growing, more extensive laser treatment has to be carried out. In 80% of cases, laser treatment causes any new blood vessels to disappear.
Glaucoma is the name for a group of eye conditions in which the optic nerve is damaged at its junction with the eye. The nerve carries information from the light sensitive layer in your eye, the retina, to the brain where it is perceived as a picture.
The eye needs a certain amount of internal pressure in order for it to be the necessary shape to work properly. In some people, damage is caused by raised eye pressure, others may have normal eye pressure but a weakness in the optic nerve. In most cases both factors are involved to varying degrees. Eye pressure is largely independent of blood pressure. Glaucoma becomes more common in those over the age of 40.
What controls the pressure?
A layer of cells behind the iris (the coloured part of the eye), produces a watery fluid (aqueous humor). This fluid passes through the hole (the pupil) in the centre of the iris to leave the eye through tiny drainage channels. These are in the region between the front of the eye (the cornea) and the iris, and return the fluid to the blood stream. Normally the fluid produced is balanced by the fluid draining out, but if more enters than leaves, the eye pressure will rise. Aqueous humor has nothing to do with tears.
Having an eye test at least every two years and having all three glaucoma tests are very effective in detecting the condition. The three test are:
1. Viewing the optic nerve using an ophthalmoscope (like a tiny torch with a handle).
2. Measuring the pressure in the eye using a tonometer (air puffer).
3. Being shown a sequence of spots of light on a screen and finding out which ones can be seen.
These tests are very simple to carry out and don’t hurt at all.
The main treatment is designed to reduce pressure in the eye. However, some treatment also aims to improve blood supply to the optic nerve.
Treatment to lower pressure usually starts with eye drops, which act by opening up the drainage channels so that the excess aqueous humor can drain away. If this does not work, the specialist may suggest either laser treatment or an operation, called a trabeculectomy, to improve drainage. A specialist will determine the best treatment, or treatments, in each individual case.
The eye can be compared to a camera; light enters through the cornea and pupil to be focused by the lens onto the macula. The sharply focused image is then conveyed to the brain by the optic nerve. Macular degeneration is the medical term describing the loss of these functions. The macula is a part of the retina, which rests on a membrane called Bruch’s membrane, if this becomes brittle, it will allow blood vessels to grow into the retina and cause damage. If one eye is affected there is a 20% chance that the other eye will be affected within 2 years.
If one eye is fully functioning, there may not be any noticeable symptoms in the early stages. After some time however, vision may become blurred or distorted. Objects with straight edges, like telephone poles, lamp posts and doorways can start to look wrong.
A blank area is experienced at the centre of what should be normal vision. For example, a person’s face can be difficult to see, but their ears, hair and chin can be seen easily. On graph paper the area of distortion can be outlined. Colour vision may become impaired. Judging distance becomes impossible. Threading a needle, using a screwdriver and pouring liquids become difficult. The height of steps is hard to judge. All these symptoms are the result of the loss of three dimensional vision. Vision starts to become two dimensional, like a television screen or photograph.
Unfortunately there is no treatment for the ‘dry form’ of macular degeneration. With the ‘wet form’ however, if the abnormal blood vessels are not too close to the centre of the macula, laser treatment is possible. This is a painless out-patient treatment designed to seal leaking blood vessels. Treatment can be repeated if necessary. Dietary ‘cures’ for macular degeneration appear from time to time, but none so far have been scientifically proven to be of any benefit.
The retina is attached to the inside of the eye, if fluid gets underneath it, this can make it loose, rather like wallpaper coming off a damp wall. When this happens a clear image cannot be made on the retina, and vision becomes blurred and dim. Retinal detachment happens more in middle aged, short sighted people. It is quite uncommon however and only about 1 in 10,000 people is affected. Very rarely, younger people can have a weakness of the retina.
The most common symptom can be described as a shadow. Bright flashes and/or showers of dark spots called floaters can also be experienced. The symptoms are never painful. Many people have occasional flashes or floaters and these are not necessarily a cause for alarm. However, if they are severe and seem to be getting worse and/or if there is a loss of vision, then an optician or doctor should be seen urgently. Prompt treatment can often minimise any damage.
If diagnosed early enough, laser or freezing treatment may be all that is needed, this is usually performed under a local anaesthetic. Sometimes an operation to repair a hole in the retina will be needed, this is usually done under a general anaesthetic and is successful in 90% of cases after just one treatment. A repair operation does not normally result in real pain but the eye will be sore and swollen for a few days afterwards. Patients usually need to stay in hospital for two or three days observation.