Visual Acuity 101: Uncover vision disorders before eyes stop growing
One in four children has a vision problem. Since treatment efficacy declines as we age, early
detection and treatment are critical. Left untreated, kids can experience many challenges,
including blindness. The leading cause of vision loss in kids, amblyopia, is almost always
treatable when found early.
The goal is to find vision disorders before children’s eyes have finished developing. Visual
acuity testing is our best tool. It detects refractive errors by measuring the ability of the eye to
distinguish shapes and details of distant objects.
Catch risk factors early
Refractive errors are the most common vision disorders in children--myopia (nearsightedness),
hyperopia (farsightedness), and astigmatism (an imperfection in eye curvature). They occur
when light isn’t focused on the retina, causing blurred vision. They are also risk factors for
Children are born hyperopic because our eyes grow until we’re about 10 years old. A child with
uncontrolled eye growth may have an eye that grows more rapidly or doesn’t stop growing until
well after 10. This stretches the retina, which increases the chances of a retinal detachment in
the future. It’s a significant problem with myopia.
The chances of developing amblyopia are high if risk factors aren’t detected at the right age.
Once a child develops amblyopia, it can’t be reversed. The stronger eye takes over for the
weaker eye, which will start to shut down. Beyond the age of 10, it's harder to develop the
brain's visual area.
Visual acuity testing evaluates the entire visual pathway. Acuity is affected if we have an issue
in that pathway. Issues within the eye, brain, or anywhere in between will affect visual acuity.
• Discrimination – Patients are asked whether they can see letters or other optotypes on a
chart and if they understand what they are.
• Detection – This tests the ability to detect the slightest stimulus. For example, a colored dot
is reduced in size until it’s not visible.
that only vary in orientation.
objective methods, but it’s in the very early stages.
These gray cards include square-wave gratings displayed opposite a card without stripes. The
clinician watches the child through a peephole in the card to determine if the child is looking at
From three to six years old, children may be tested with a HOTV chart (uses the letters H, O, T,
and V) or the Lea symbol chart. HOTV is better for early amblyopic detection because of
“crowding bars” surrounding the intended optotypes (figures or letters of different sizes). An eye
that’s developing amblyopia starts to have issues with fixation. The eye doesn’t stay still. This
makes it difficult to focus with crowding bars, which the HOTV test brings to light.
Children are introduced to the Snellen wall chart or the ETDRS (Early Treatment of Diabetic
Retinopathy Study) test at about six years old. Most pediatricians don’t use a Snellen Chart for
the youngest kids because studies have shown it to have zero positive predictive value in
children under 4.
The ETDRS study introduced new visual acuity charts using Sloan optotypes. It’s preferred to
the traditional Snellen chart (introduced in 1862) for precise visual acuity measurement in
research or clinical settings. It’s not practical for most primary care practices due to its high cost,
specialized equipment, and specialized training.
The GoCheck Kids digital visual acuity test is first attempted when children are four years old,
as recommended by the American Academy of Pediatrics, American Academy of
Ophthalmology, and American Association of Pediatric Ophthalmology & Strabismus. The visual
acuity testing logic in GoCheck Kids is designed to be as effective as visual acuity testing in a
pediatric ophthalmology setting. It removes tester bias and eliminates the ability to cheat.
The methodology uses modified Amblyopia Treatment Studies (ATS) and ETDRS protocols with
Sloan optotypes, crowding bars, and sophisticated algorithms. ATS protocols came out of
studies by the Pediatric Eye Disease Investigator Group, funded by the National Eye Institute, to
evaluate amblyopia treatment regimen effectiveness. Their results have greatly influenced
clinical amblyopia practice.
narrowed career choices, and permanent vision loss without early treatment. Thankfully, there
are effective testing options to check kids for vision disorders at a young age. They can get the
treatment they need before their eyes have finished growing.