Orthoptics Awareness Week is taking place between 1-5 June with the theme ‘Seeing the future’. In the second article of a five-part series, South Australian orthoptist Lachlan Knight focuses on the detection of inherited eye disease in children.
A referral lands in the hands of an orthoptist stating that the child has trouble seeing the board. Sometimes the referral says the child has ongoing light sensitivity, trouble identifying colours or just likes to hold things close to their face.
Sometimes, the child has simply failed their preschool vision test, or perhaps the referral states they are frightened of the dark and it’s brushed off as normal childhood behaviour.
These are all common complaints that usually do not warrant much further investigation. However, a genetic eye disease can sometimes present the same way and it is the skilled orthoptist who determines the likelihood of such a condition.
Inherited eye diseases are relatively rare and encompass a broad spectrum of ocular conditions. Each condition, caused by an abnormal change in an individual’s genetics, generally come with their own set of clinical signs and symptoms.
Even then, someone with the same genetic mutation may present at a different age with a varying degree of severity or disease progression. Consequently, the orthoptic examination may not be as straightforward as one thinks. It is best to approach genetic eye disease as a puzzle.
The first piece of the puzzle is the history of the child’s complaint. History taking when suspecting a genetic eye disease in a child involves thinking outside the box and digging deeper.
Let’s consider more commonly known genetic eye diseases such as a cone/rod dystrophy, albinism or retinitis pigmentosa. Buzz words such as age at onset, gradual or sudden changes in behaviour and light or dark adaptation spring to the forefront of an assessment and an orthoptist will begin to question outdoor and indoor behaviour.
However, and understandably, children may not be able to explain what they see or notice any changes they are going through. Asking something as simple as what they like to do guides the orthoptist in determining signs and symptoms. But of course, the parent may be the best source of information.
The second piece of the puzzle is the family history. If there is a known family history, the task is an easy one. However, if the ocular symptomology is an unfamiliar phenomenon within the family, a family tree becomes critical.
An orthoptist plays the detective as they navigate immediate and distant ancestry to determine a likely inheritance pattern. For example, the key may lie in a distant paternal great-uncle who is colour-blind, or someone closer such as an older sibling who is strikingly blonde with no apparent ocular problems. The orthoptist knows that no clue is insignificant.
The third piece of the puzzle is found by observing the child and learning about their visual behaviours. An orthoptist who specialises in paediatrics is particularly skilled at observing and documenting the visual behaviours of children of all ages. This is especially required when children struggle to sit still and are unable to perform other clinical testing. The way they hold their digital device or lose attention at certain distances can provide a lot of information.
Clinical examinations provide the fourth piece of the puzzle. This is guided by the history and observations. An orthoptist may choose to perform cone function tests such as near visual acuity and colour vision.
If rod dysfunction is suspected, then visual fields are crucial. Some orthoptists also specialise in electrophysiology testing for rod and cone disorders or even albinism. Perhaps if albinism is suspected, a child will undergo cover testing, a nystagmus assessment and cycloplegic refraction. An orthoptist also knows not to dilate a suspected albinism case before iris transillumination defect is checked. Whatever diagnosis is being chased, the orthoptist meticulously chooses each test to perform and knows how to extract maximal information from the child. The orthoptist’s findings, paired with the ophthalmologist’s findings, then guide the clinical geneticist in determining which genes to test for and consequently provide genetic counselling. This completes the puzzle.
Orthoptists evidently play a key role in the assessment of inherited eye diseases as they complete parts of the puzzle. Their knowledge is invaluable, paired with their skills and talents in paediatric orthoptic assessments. While genetic eye diseases are encountered infrequently, their investigation is critical so that the child, and family, can understand their child’s visual behaviours and prognosis and gain access to the necessary supports. One might find an orthoptist who specialises in this area in a tertiary public hospital in an ocular genetics clinic.
ABOUT THE AUTHOR: Lachlan Knight is an orthoptist who specialises in paediatrics and genetic eye disease at Flinders Medical Centre and the Women’s and Children’s Hospital, Adelaide. He is also undertaking his PhD in the genetics of childhood glaucoma at Flinders University.