Amblyopia is maldevelopment of the visual cortex in the brain during infancy or early childhood that leads to decreased central vision in the affected eye. The hallmark of amblyopia is decreased monocular vision that is not accounted for by other ocular pathology.
Any abnormality that leads to irregular visual stimulation can cause amblyopia, including strabismus, anisometropia, or media opacity. Amblyopia causes more unilateral cases of reduced vision in childhood than all other causes combined, and it affects approximately 2-5% of all children.
The pathology of amblyopia generally occurs by one of two mechanisms. First, a blurred or incomplete image on the retina during the period of visual development (from birth until approximately 10 years of age) inhibits cortical activity in the brain, ultimately leading to underdevelopment of vision in the affected eye.
Second, in the setting of strabismus, misaligned eyes prevent the child from developing fusion of the images from each eye, which leads the brain to suppress the image from the deviated eye so as to avoid diplopia, which in turn reduces the visual potential of that eye.
It's important to start treatment for lazy eye as soon as possible in childhood, when the complicated connections between the eye and the brain are forming.
The best results occur when treatment starts before age 7, although half of children between the ages of 7 and 17 respond to treatment.
The findings suggest that pediatricians and other primary care providers could use the device to catch amblyopia at an early age when it’s easier to treat,
The method for vision testing in infants can be fully automated at a low cost and doesn’t require operator skills, which means it can be used for amblyopia testing in schools and other community settings, with a potential massive impact to test children worldwide.
Computer gaming technology is being used to develop and pilot two low cost, next-generation screening tools for ‘lazy eye’ in children.
NHS Forth Valley Consultant Ophthalmologist, Dr Iain Livingstone and Dr Mario Giardini, senior lecturer in the University of Strathclyde’s Department of Biomedical Engineering, have developed two prototype devices to test for ‘lazy eye’ in children who are too young to speak or follow instructions for a conventional eye test.
The first uses a computer screen webcam and bespoke analysis software. Test patterns are presented on the computer monitor while the webcam focuses on the subject.
The computer then analyses the video stream from the webcam, and detects whether or not the target image has been seen. The second prototype functions in the same way, but uses a virtual reality headset instead of a webcam.
Both platforms were tested on healthy child and adult volunteers, who wore blurring lenses to simulate visual defects. Both were successful in detecting whether visual targets had been seen.
Dr Livingstone said: “Children with amblyopia or ‘lazy eye’ may struggle to see clearly and have difficulty with depth perception. If left untreated, vision may never reach normal levels, leading to lifelong problems.
Early diagnosis is crucial because the younger the child can be treated, ideally in early infancy, the greater the chance of a successful outcome.
“Children who have not yet learned to speak cannot follow instructions so the standard eye tests, which involve presenting a child with a printed card or paddle, rely on the child’s ‘looking response’ to determine whether or not they have seen the target pattern.”
Dr Giardini added: “As human beings we’re hard wired to recognise faces and high contrast objects. We know that from a few hours after birth a baby will turn their eyes to a high contrast object or a face, so we wanted to explore how paediatric vision testing protocols can be transformed using digital technologies, where there is no operator to distract the child.”
Amblyopia, or “lazy eye”, is one of the most common causes of sight loss in children, affecting around one child in 50 in the UK. It occurs when there is a breakdown in the way in which the brain and eyes work together.
Normally, the brain processes visual information from both eyes to enable us to see. However, if an eye condition such as a squint, long or short-sightedness, or cataract, causes visual impairment in one eye, the brain may start to rely solely on signals from the ‘stronger’ eye, causing the vision in the ‘weaker’ eye to deteriorate further
Across the world, where tests are available, they need to be administered in a hospital or specialist healthcare setting, by highly skilled personnel, who are trained to evaluate the child’s attention response, which makes large scale screening a challenge.
In countries where screening programmes are available, they are normally directed at older children, aged around four to five, who are able to follow instructions and engage with testing. By this age, however, the treatment for amblyopia is likely to be less effective.
By moving difficult diagnostics from specialists to the community, this work makes healthcare more accessible, and reduces inequalities of access. These developments clearly show what can be achieved through the open collaboration.