Vision

In general, people with Down’s syndrome tend to have poor visual acuity even when corrected with spectacles (9). Regular eye checks are not only necessary to correct their vision but also to check the health of their eyes.

When should a child with Down’s Syndrome get their eyes checked and how often?

• Birth – 6 months – Check for congenital cataracts.
• 18- 24 months – full eye examination. Checking for a squint (orthoptic examination) and if they need spectacles.
• Age 4 – full eye exam. Checking for squint and if they need spectacles.
• School Age – routine eye examination every 2 years.
• Thereafter, an eye test is recommended every 2 years.

It is important to check the eye health of a person with Down’s Syndrome as they tend to be more likely to have various eye conditions.  Below are a few of these are explained bleow along with treatment methods.  These conditions are common in many children, but are more prominent and frequent in a child with Down’s syndrome.

Squint

        

 Picture showing a child with Squint ( L, Newson 2011) (3)

With a squint, the eyes aren’t pointing in the same direction.  This can cause difficulty with binocular vision; this is when the images of both eyes fuse together to form one image. Binocular vision is important as it gives our sight 3D perception (2). If the eyes aren’t pointing in the same direction, they see very different separate images and the brain can’t fuse them together. The brain supresses an eye.  This leaves one eye very weak with a usual lower visual acuity.

Wearing spectacles can correct a squint or make it less obvious, if the squint is due to long (hypermetropia) or short-sightedness (Myopia) in the child. For example, when the eye turns in towards the nose this is known as a convergent squint, caused by long-sightedness.

Squints are present in 1 in 5 children with Down’s Syndrome.

Children with Down’s Syndrome are advised to have additional screening as due to the shape of their eyelids, it can be difficult to identify a squint present. (Down’s Syndrome Medical Health Check Guidelines)

Referral to orthoptists and ophthalmologists for treatment would be the next stage after detecting a squint.

Hypermetropia

Long-sightedness is when the child strains to see things clearly and in focus up close (near vision). Before starting school, a massive 40% of Children with Down’s Syndrome have this strain and therefore need to have it  corrected with glasses. It can also be a cause of squints talked about previously, especially if one eye is more long-sighted than the other.  This leads to a ‘Lazy eye.’  Treatment would involve referral to the orthoptist for patching and other orthoptic management schemes.

Myopia

Short-sightedness is when someone has blurred distance vision but can see clearly up close (clear near vision).  A smaller percentage of 14% of Down’s Syndrome Children have this before starting school, being more common in adolescence (1). It is easily corrected with glasses.

Weak accommodation

Children with down’s syndrome can find it difficult to focus for close work.  This is regardless of the fact they wear glasses, or they do not wear glasses. To help with this, children can find it useful to wear a bifocal pair of glasses. This means there is a part of the lens designed specifically to help with close work.

Glasses on Individuals with Down’s – (P, Fassel, 2014) (5)

Nystagmus

Nystagmus is a twitching and jerking of the eye. It happens involuntarily.  This eye movement can cause the vision to be jerky also.  This sensation is called Oscillopsia (6). The child may have noticed a position of gaze in which the nystagmus is relieved.  Usually the child takes on a head tilt or a different positioning of the head because at this position of nystagmus relief, the vision will be better for the child.  This point of good vision from positioning the head differently is called the ‘null position.’  If this does happen, the different head positioning is to be encouraged.  The child may also read with the object very close to their eyes. This is also to be encouraged. Depending on the type of nystagmus, different drugs may be used as treatment (6).The Visual Impairment Support Service of the Local Education Authority can educate and give advice on a child who has been referred for having a nystagmus.

Eye Infections

Eye infections are common in children with down’s syndrome. Such infections include blepharitis and blocked tear ducts.  Between the corner of the eyes and the back of the nose there is a tube which filters out tears.  This filter is called the lacrimal gland.  Typically, in people with Down’s Syndrome the tube is smaller and therefore more likely to get blocked.  With tears not washing from the eyes, infections are more likely.  Blepharitis involves the lids of the eye and the lashes becoming inflamed, painful and flaking. (1) Simple and effective treatments such as bathing the eyes in cooled water which was previously boiled can cure an infection, whilst an antibiotic in more severe cases would be necessary.

Cataracts

Usually cataracts are associated with the aging of the lens; with age the lens gets cloudier. This makes it difficult to see clearly and vision can get worse. However, rarely new born babies can be found to have congenital cataracts. These can be removed through a procedure in which the lens is replaced with another lens.

Cataracts can be denser than others.  Very dense cataracts would be removed in this way as it will affect the vision of the child.  In children with Down’s Syndrome, this isn’t very common, with less than 1% having these cataracts.  The cataract that is removed can also be left in a way to insert a lens later in the child’s life if needs be. Spectacles or even contact lenses can correct for this if the lens is not replaced. A cataract which is not dense may not affect the child’s vision and may not yet need treatment.

Astigmatism

Astigmatism results in the images seen by the person to be distorted much more in one direction in comparison to another. It occurs because of the shape of the eye. Instead of being round and spherical, the eye is more oval and usually described in terms of a ‘rugby ball’ shape (4). Astigmatism is corrected by wearing glasses. Of Down’s Syndrome children starting school and younger, a huge 30% have astigmatism and therefore need correction for this to ensure clear vision.(1)

Keratoconus

This is a condition of the outermost part of the front of the eye, the cornea.  The cornea is a cone shape.  Symptoms include short-sightedness and astigmatism (explained earlier).  If the condition worsens, the cornea can become very thin and need a corneal graft.  Again, this can also be corrected with the use of contact lenses.

Normal Cornea vs Keratoconic Cornea – Scher & Ward . (2016).  (7)

Infantile Glaucoma

This is when the pressure inside the eye is raised. Raised pressure can damage the optic nerve in the eye and cause vision loss (8). If this is suspected the baby is immediately referred to an ophthalmologist. The symptoms are sensitivity to light, watery eyes, the eyes look larger and the baby is very distressed (1).This rarely occurs but Down’s Syndrome babies are more at risk to this.

All these conditions can be treated so it is important that a child with Down’s Syndrome and thereafter gets regular eye checks to check the health of their eyes.

References:

1. Down’s Syndrome Association. (2014). Eye Problems in Children.Available: https://www.downs-syndrome.org.uk/download-package/eye-problems-in-children/. Last accessed 8th December 2017.
2. IP Howard, B.J. Rogers. (1995). General Introduction. Binocular Vision and Stereopsis. 1 (1.1.1.), 2.
3. L, Newson. (2011). The Basics – Strabismus.Available: https://www.gponline.com/basics-strabismus/ophthalmology/article/1055827. Last accessed 8th December 2017.
4. (2017). Astigmatism.Available: https://www.nhs.uk/conditions/Astigmatism/. Last accessed 9th December 2017.
5. P, Fassel. (2014). Eyeglass Challenges for Children With Down’s Syndrome.Available: https://www.2020mag.com/article/eyeglass-challenges-for-children-with-downs-syndrome. Last accessed 8th December 2017.
6. Rusker, J.C.. (2005). Current Treatment Options in Neurology. Current treatment of nystagmus. 7 (1), 69-77.
7. Scher & Ward . (2016). Available: http://www.scherandward.co.uk/contact-lenses/keratoconus/. Last accessed 8th December 2017.
8. Vincent P.deLuise M.D, Douglas R.AndersonM.D.. (1983). Primary infantile glaucoma (congenital glaucoma). Survey of Opthalmology. 28 (1), 1-19.
9. Woodhouse, J.M etc. (1996). Visual acuity and accommodation in infants and young children with Down’s syndrome. Journal of Intellectual Disability Research. 40 (1), 49-55.