Most Common Vision Problems in Down syndrome

The most common vision problems in people with Down syndrome include refractive errors (long-sighted and short-sighted) and strabismus (squint) may occur at an early age and persist into childhood 50% of people with Down’s syndrome wear glasses.
The majority of children with Down syndrome have reduced accommodation at near (do not focus accurately on near targets)
Cataract and/or Glaucoma may occur in infancy.
Nystagmus is present in about 10%.
Brushfield spots are present in the eye in many children at birth.
Keratoconus and cataract may develop in adolescents and young adults.
If undiagnosed and/or untreated, many of these disorders are a significant cause of preventable secondary handicap.

Long-sighted

Long-sighted or hypermetropia results in the person having more difficulty in seeing things that are close up than far away, although both can be affected. This condition can be corrected with prescription lenses.

Short-sighted

Short-sighted or myopia results in the person having difficulty in seeing things that are in the distance. This condition can also be corrected with prescription lenses.

Accommodation

Accommodation - FOCUSSING DIFFICULTY ('WEAK ACCOMMODATION')
Many children with Down syndrome have difficulties focusing well on near tasks, and this applies whether they are long-sighted, short-sighted or even if they do not need glasses for general use. Furthermore, the problem with focussing persists even if the children wear their glasses.
Recent studies have suggested that children that have this problem with focusing benefit from wearing bifocals, at least in school. Some children with Down’s syndrome choose to wear their bifocals all of the time, preferring them to the conventional ‘single vision’ glasses.

Astigmatism

Astigmatism occurs when the curve of the cornea is not symmetrical. It can occur alongside long-sight and short-sight and results in the person having blurred vision at all distances. Astigmatism is treated with prescription lenses (glasses or contact lenses) that are designed to counteract the different curves of the cornea.

Presbyopia

This condition (literally old eye) affects all of us as we get older, whether we wear glasses or not in our youth. The lens, which is flexible when we are younger, loses its ability to change shape so that focusing on near tasks becomes difficult or impossible. Affecting most of us at around the age of forty-five, presbyopia may happen at a younger age in people with Down syndrome. Reading glasses or bifocals are usually prescribed, and it is important to remember that people who do not read may benefit from glasses for near tasks like crafts and puzzles and, of course, eating.

Strabismus

Strabismus or squint is quite common amongst people with Down syndrome. This condition arises because of a lack of muscle coordination between the eyes and causes them to point in different directions. As a result of strabismus individuals may experience double vision, vision in one eye only, loss of depth perception and uncoordinated - appearing eyes. Squints can often be effectively treated in children, however if the problem is left into adulthood it can be harder to rectify, as the person will have usually developed ways to compensate.

Cataract

Cataract is a clouding of the lens. It can cause the person to have one or more of the following: blurred vision, double vision, difficulty seeing in bright light and, most importantly, disabling glare when facing a light source. Amongst some people with Down syndrome, the onset or worsening of a cataract brings about behaviour that others find challenging as vision changes dramatically depending on the environment. This behaviour may be their only way of telling supporters that something is very wrong. The most effective treatment for cataracts is surgery to remove the lens. While surgeons often choose to perform cataract surgery on people with Down syndrome under general anaesthetic, it can be carried out under local anaesthetic with some sedation. The operation generally only takes about 45 minutes and involves a small cut in the top of the eye which is stitched afterwards. The cloudy lens is removed and a plastic replacement implanted.

On occasions, the surgeon may decide that the eye is unsuitable for an implant and the person will be prescribed either glasses or contact lenses instead. The main issue around cataract surgery for a person with Down syndrome is supervision after the operation, to prevent eye rubbing.

Glaucoma

Glaucoma - INFANTILE GLAUCOMA
This very rare condition is slightly more common in babies with Down syndrome. Typically the eye looks larger than normal. The baby is distressed, particularly by bright lights, and the eyes may water more than usual. Urgent referral to an ophthalmologist is essential.

Nystagmus

Nystagmus is an involuntary movement of the eyes - usually from side to side, but sometimes the eyes oscillate up and down or in a circular motion. This affects about 15% of people with Down syndrome, but it is not part of the syndrome and should be considered as a visual impairment that someone has in addition to Down syndrome. Detail vision will be poorer if a person has nystagmus.

Most people with nystagmus are affected by factors such as stress, tiredness and unfamiliar surroundings, making eye movements greater and vision worse. They are also likely to tire more easily due to the increased effort to concentrate on focusing. People often adopt a certain head position or head movement that helps them maximise their vision and it is crucial that they be able to locate and position themselves wherever is most helpful.

For those people with literacy skills, reading can be slow although this should not be seen as having poor reading ability. People should be given more time to complete tasks. The size and density of lettering that is required will vary from person to person, and experimenting with colour contrast may help. Mobility can be affected as some people can have difficulty with balance and depth perception, for example, the person may think a change in floor colour is a step. Some people find scanning their environment very difficult, and safety when crossing roads may become an issue.

Unfortunately, there is no cure for nystagmus and little treatment has proved to be effective. It is important that any other eye condition that is present is treated, for example a person should still wear glasses for short-sight, even though they will not help the nystagmus.

Brushfield spots

Brushfield spots are small white or grayish/brown spots on the periphery of the iris in the human eye due to aggregation of a normal iris element (connective tissue). These spots are normal in children but are also a feature of the chromosomal disorder Down syndrome. They occur in 35-78% of newborn infants with Down syndrome. They are much more likely to occur in Down syndrome children of the Caucasian race than children of Asian heritage. Brushfield spots are named after the physician, Thomas Brushfield, who first described them in 1924.

Keratoconus

Keratoconus literally means conical cornea. The cornea is usually transparent and spherical, however in this condition the cornea stretches causing the tissue to thin and the centre to bulge. The cornea is the main part of the eye responsible for focusing so a change in its shape causes distorted vision (usually a combination of myopia and astigmatism). Other symptoms may include: sensitivity to bright light, double vision, difficulty adjusting to vision in differently lit environments and halos around images.

Keratoconus can progress at various rates and usually to different degrees in each eye. The changes to the eye can stabilise after a few months or continue for many years. In a small number of cases the cornea can become so fragile that the back surface ruptures allowing fluid in. This condition is known as hydrops and can cause some pain and blurred vision.

Although keratoconus is a fairly rare condition and the cause unknown, evidence shows an increased risk amongst people with Down syndrome, people with a history of allergies such as asthma, eczema and hay fever, people who eye rub or eye poke, and South Asian and Afro-Caribbean people.

Management of keratoconus varies depending on its level of its progression. In the early stages glasses may help, but the best management is with contact lenses, which can restore good vision.
Some health professionals may make the unfortunate assumption that people with Down s syndrome are unable to cope with contact lenses, but there are increasing numbers of specialist optometrists who fit lenses. Families and carers, as well as the person with Down syndrome, may need to be trained to insert and remove lenses.

In very rare cases people require corneal surgery in which a corneal transplant is carried out.