Key learning points:
– Assessment of vision in babies can be difficult and parents’ concerns need to be taken seriously
– Orthoptists are healthcare professionals who specialise in the assessment of babies and children
– If a nurse is unable to assess a red reflex test, the child should be referred to a professional who is capable of doing this
Visual problems are common in children, and affect at least 11% of them.1 Vision and visual function is an essential part of a child’s development; it accompanies the development of the eye and brain. Visual function comprises of three parts:
1.Light sense – the ability to distinguish between light and dark.
2.Form sense – the ability to distinguish the size and shape of an object by the position of its edges.
3.Coloursense – the ability to distinguish between different wavelengths of light.
Visual acuity is mediated by the foveola which is composed of highly sensitive visual cells (cones), and it projects to a large region of the primary visual cortex in the brain. By assessing acuity we are determining the function along the entire visual pathway. Visual acuity is defined as the finest detail that is detectable, otherwise known as minimum angle of resolution (MAR) and is recorded by different conventions, the two most common being:
1.Snellens(6/6 or 20/20). This means a child sees at six metres the same as a normal adult sees at six metres. In America, 20/20 refers to the vision at 20 feet rather than six metres.
2.logMAR(0.00). This is logarithm of the minimal angle of resolution and uses a different chart from Snellens. It is the best way of comparing improvement in vision and is most used in ophthalmology departments.
Eyesight in newborn babies and how it develops
The foveola is not developed at birth. Throughout the first four months the density of these foveal cones increases with the anterior segment of each cone lengthening.2 This foveal development is believed to contribute extensively to the swift rise in visual acuity from birth to six months. At around four months the maturation of cortical synapses and myelination of the visual pathways is completed. It has been shown that cortical maturation contributes to the early development of vision.3 If the vision in one eye is decreased, for example due to squint or cataract, vision in the other eye would increase and become abnormally high for a child of that age. This demonstrates why it is important to assess the vision in children for each eye separately as often the weaker eye will go unnoticed and masked by the unaffected eye with both eyes open. In the first three months, the vision may be poor but this may be related to the development of the fovea. A clue to assessing vision for both eyes in young infants is to ask if the baby is smiling at their mother.
Contrast sensitivity is the ability to see objects that may not be outlined clearly or do not stand out from their background, for example, the ability to see a shade of grey on a white background. At birth, contrast sensitivity is approximately one-in-30 of its eventual level.4 Similar to visual acuity, it develops rapidly in the first six months of life. Infants below the age of six months may struggle to see pastel colours (pink or light blue) but should be able to see black toys against a white background.
The sensitive period for visual acuity and contrast sensitivity extends to eight years, visual deprivation to either eye during this period results in loss of visual acuity. This is why early detection is essential to maximise the effect of treatments because early treatment provides better results.5
After the age of five, visual acuity can be measured by a classic letter chart in an opticians. Before this age, orthoptists have the ability to assess vision using various techniques, including preferential looking techniques.
Signs of poor vision
In nursing practice, it is essential to be able to identify if a child is seeing well or not, and what to do if you think they are struggling. There are some clear signs when a baby may be struggling with their sight as stated in the Red Book the Personal Child Health Record that is given to every new parent.
– Squint (strabismus) – A child with a squint is at risk of the vision in the squinting eye not developing. Squints are common and affect 2.1% of the childhood population.1 However, they may harbour dangerous conditions so it is essential the nurse performs a red reflex assessment or refers to someone who can assess this. If there is no white or abnormal reflex, the child can be referred routinely to a GP or paediatric ophthalmologist.
– Ptosis (droopy eyelid) – This can cover the visual axis of the eye and occlude the child’s vision. It can potentially halt the visual development of the eye and cause astigmatism. It is essential such a child is referred to a paediatric ophthalmologist.
– Nystagmus – This is a ‘wobbling’ of one or both eyes; this is often horizontal movements but can be vertical also. It is usually a sign of poor vision and requires an urgent referral to a paediatric ophthalmologist particularly if vision is poor and/or the onset is acquired (after the age of three months).
– Leucocoria (white reflex) – the normal reflex through the pupil in the eye when a light is shone co-axially is red. This is due to reflection of the blood vessels at the back of the eye. However, if it is absent or white, this can be abnormal and it can be a sign of serious pathology. The most common cause is cataract but cancer such as retinoblastoma can also be detected.
– Enlarged eyes (buphthalmos) – If one eye is visibly larger than the other or if both eyes enlarge with hazy corneas (front of eye), this may be due to raised pressure in the eye and requires urgent referral to a paediatric ophthalmologist.
– Behaviour – Often children with significant vision problems will hold things very close to them, or “screw their eyes up” when trying to focus on things. Dependent on the level of their vision, parents may also describe a lack of eye contact or a lack of smiling with eye contact. This is important after the age of three months as foveolar development progresses.
What a health visitor should do if a problem is suspected
The health visitor should refer any child that has a white reflex to a GP urgently. The GP should then refer to a local paediatric ophthalmologist on an urgent basis, who will in turn refer to a national retinoblastoma unit. These units will see patients within seven days of referral. There are two national retinoblastoma units in the UK. One in London (Royal London Hospital) and the other in Birmingham (Birmingham Children’s Hospital).
Long delays in the diagnosis of retinoblastoma can cause death.7 In the UK this is rare, but healthcare professionals need to be vigilant. In the 1990s the greatest delay in diagnosis in the UK was related to the first healthcare professional being a health visitor with a median delay of 13 weeks in referral to an ophthalmologist compared to parents who went directly to a GP and had a one week delay.8 Recent unpublished data shows the delay for health visitors has reduced but still remains at three weeks compared to GPs who have a median delay of one week.
It is essential that practice nurses and health visitors are aware of the importance of eye conditions in infants and the referral pathway.
Case study: Child with retinoblastoma
A mother has noticed a ‘cat’s eye’ reflex in her six month old baby’s left eye. A health visitor is asked to visit. The baby is seeing well with both eyes open, and smiling at its mother. The baby looks healthy and giggles during the examination. There is no evidence of muscle wasting and the baby is feeding well. The health visitor feels that the outside of the eye looks fine and is not red. The child does not have an obvious squint. The mother is reassured and told there is nothing to worry about.
Three months later the left eye enlarges and the front of the eye becomes hazy. The mother takes the baby directly to A&E and the child is seen by the local paediatric ophthalmologist within a day. Within seven days of the visit to A&E, the family travel several hundred miles to a national retinoblastoma unit.
Bilateral retinoblastoma is diagnosed and the left eye is removed. The baby undergoes systemic chemotherapy and 45 examinations under anaesthesia with laser and cryotherapy over four years in order to save the remaining eye which now cannot see. The child is certified as severely sight impaired.
A white reflex (see opposite page) in the eye can be caused by many conditions. If picked up by a camera it will most likely be due to the reflection of the optic nerve and this will not harm the child.6 However, a ‘bona fide’ white reflex is most likely due to a congenital cataract and it is important to detect this as soon as possible after birth, in order to improve visual outcomes following surgery. The most dangerous condition to cause a white reflex is retinoblastoma, which affects around one in 17,000 live births. In infants it can affect both eyes but one eye is usually more affected than the other. In the UK the survival is 99% at five years although removal of eye (enucleation) is still necessary. In underserved countries, survival drops to 20% with 80% of children dying from this condition.
Learning points from the case study:
1.A child can be blind in one eye yet still smile at their mother and see objects as the baby uses the other less affected or normal eye.
2.Retinoblastoma (childhood eye cancer) will not cause a child to be ill. This can prove confusing to healthcare professionals as it is difficult to understand how a fit and healthy child can harbour cancer.
Resources
Childhood Eye Cancer Trust– chect.org.uk
Barts Health Retinoblastoma Service– bartshealth.nhs.uk/our-services/services-a-z/r/retinoblastoma/
Children’s Eyes in London– childrenseyes.london
Royal London Society for the Blind– rlsb.org.uk
References
1. Williams C, Northstone K, Howard M, Harvey I, Harrad RA, Sparrow JM. Prevalence and risk factors for common vision problems in children: data from the ALSPAC study. British Journal of Ophthalmology2008; 92:959-64
2. Yuodelis C, Hendrikson A. A qualitative and quantitative analysis of the human fovea during development. Vision Research 1986;26:847-855.
3. Mohindra L, Jacobson S, Zwaan J, Held R. Psychological assessment of visual acuity in infants with visual disorders. Behavioural Brain Research1983;10:51-58.
4. Held R. Normal visual development and its deviations. In: G Lennerstrand, G.K.von Noorden & E.C.Campos, eds. Strabismus and Amblyopia: Wenner Gren International Symposium Series. Macmillan, London; 1988:247-258.
5. Harwerth RS, Smith EL, Duncan GC, Crawford MLJ, Von Noorden GK. Multiple sensitive periods in the development of the primate visual system. Science1986;232:235-8.
6. Muen W, Hindocha M, Reddy MA. The role of education in the promotion of red reflex assessments. JRSM Short Reports2010;1:46.
7. Brasme J, Morfouace M, Grill J, Martinot A, Amalberti R, Bons-Letouzey C, Chalumeau M. Delays in diagnosis of paediatric cancers: a systematic review and comparison with expert testimony in lawsuits. Lancet Oncology2012;13:e445-459
8. Goddard AG, Kingston JE, Hungerford JL. Delay in diagnosis of retinoblastoma: risk factors and treatment outcome. British Journal of Ophthalmology1999; 83:1320-3
