What is a lazy eye and how does it develop?
Amblyopia, commonly known as lazy eye, is a neuro-developmental vision condition that begins in early childhood, usually before age eight.
A lazy eye develops when the neural connections between the eye and the brain are interrupted and one eye is unable to achieve normal visual acuity, even with corrective lenses.
Lazy eye can be caused by an eye turn, an ocular obstruction, such as a drooping eyelid (ptosis), a significantly high optical prescription, or even if there is a significant difference between the optical prescription of the two eyes.
While any of these conditions may result in a lazy eye, the true underlying cause of lazy eye is a reaction in the brain, called suppression.
Suppression occurs when the brain actively ignores all of the visual information coming from one eye to avoid blurry or double vision (diplopia).
What happens when you have a lazy eye?
Children with lazy eye are unable to achieve binocular vision, and therefore, often have difficulty with depth perception— seeing in 3D and judging spatial distances between objects.
Depth perception allows you to determine where you are in space, in relation to the objects around you.
Depth perception is a necessary skill for accurate eye-hand coordination, and without it, a child may have difficulty playing sports or be labeled as “accident prone”.
What is eye-hand coordination and why is it necessary?
Eye-hand coordination is the ability to coordinate visual information received through the eyes to control and direct hand movements for the achievement of any given task.
This skill is typically learned as early as four months of age, and continues to develop as the child grows and reaches new milestones.
Basic eye-hand coordination skills include reaching, grasping, feeding, and dressing. But as an infant matures, eye-hand coordination skills become increasingly important for exploring toys and other objects, climbing, catching and hitting balls, drawing, writing, cutting and pasting.
How does a lazy eye affect eye-hand coordination?
Binocular vision is the ability to use both eyes simultaneously to view an object as a clear, single image.
Binocular vision is essential for accurate depth perception.
Each eye receives different visual spatial information, which is then sent to the brain for interpretation and processing. The brain uses the information from both eyes to determine the 3-dimensional spatial relationships between objects to judge distance and depth.
When a child has a lazy eye, the vision from the affected eye is suppressed by the brain, thereby affecting their 3D vision— and impacting their depth perception and eye-hand coordination.
Is eye-hand coordination dependent on binocular vision?
A study was conducted to determine if eye-hand coordination is truly dependent on binocular vision.
The study included 3 groups:
- Group 1: 36 children ages 5 to 11 years with normal binocular vision
- Group 2: 11 adults with normal binocular vision
- Group 3: 21 children ages 4 to 8 years with strabismus and or anisometropia
During the study, the three different groups were asked to perform the same reach to grasp activities to determine if eye-hand coordination is indeed affected by lazy eye.
The two groups with normal binocular vision were asked to use only one eye while performing the activities in order to limit their binocular vision.
According to the results of the study:
- Group 1: The younger children were often seen colliding with the objects they meant to grasp.
The older children were able to use their visual feedback to help them reach and grasp the desired object, even with one eye closed.
- Group 2: This group was able to use their visual feedback, in the same way as the older children in group 1.
The researchers explained this phenomenon by concluding that their ability to use visual feedback was due to the fact that they had developed this skill from many years of having binocular vision.
- Group 3: This group was unable to successfully perform the reach to grasp activity, even while using their dominant eye. These children took much longer to reach the desired object, and made up to three times more errors in both reach direction and grip position.
Conclusion: Binocular vision is absolutely necessary for children to develop accurate hand-eye coordination.
Can a lazy eye be treated?
Vision therapy is highly successful for the treatment of lazy eye, as it helps to strengthen the eye-brain connections necessary for improved binocular vision, depth perception, and eye-hand coordination.
A vision therapy program may include the use of specific exercises, lenses, prisms, filters, occluders, and other specialized equipment designed to actively encourage the lazy eye to work. Home practice exercises may also be prescribed to reinforce the office-based treatments.
Binocular vision is a necessary skill for 3D vision, spatial awareness and well developed eye-hand coordination.
If your child displays poor eye-hand coordination as a result of a lazy eye, vision therapy can help to strengthen their binocular vision— for improved academic and athletic success.