Checking for Eye Misalignment (Strabismus)
Checking for normal eye alignment is an important component of an eye examination. Our optometrist pays close attention to a patient’s eye position while they are looking at a target as this is important not only for the healthy development of vision in children but also to prevent an individual from seeing double.
There are a variety of reasons that an eye may be turned either inwards (called esotropia) or outwards (called exotropia). Below are some of the commonly considered risk factors for eye turns.
Genetic and Developmental Conditions Causing Strabismus
Some eye turns may occur due to a genetic variant, which is most often associated with inward turned eyes but can also be associated with outward turned eyes. The closer an affected relative is in the family tree to the patient, the more likely an eye turn will be noticed.
Certain developmental conditions may be associated with eye turns, including Down’s syndrome, which more often shows inward turned eyes but can also be associated with outward turned eyes. Cerebral palsy is another example of a developmental disorder associated with outward turned eyes.
Premature Birth and Eye Misalignment Could Lead to Strabismus
Infants that are born premature (less than 36 weeks of gestation) have a five times higher risk of an inward eye turn. If the child has undergone oxygen treatment at birth, they may also be at risk for retinopathy of prematurity, an ocular condition in which blood vessels at the back of the eye develop irregularly.
These blood vessels are crucial for the development of the nerve layer at the back of the eye that is responsible for seeing, called the retina, and thus may cause a disruption to the sensory stimuli experienced by the infant. This may ultimately lead to abnormal visual development and a subsequent eye turn as well.
Infection and Trauma Causing Ocular Deviations
Some infectious diseases that affect the body can have effects on the eyes. These include meningitis (a brain infection) and viral infections such as herpes simplex (the cold sore virus). These can cause disruption to the nerves that move the eye muscles and thus a temporary or permanent change in the position of the eye.
Any traumatic injuries that occur to or around the eye can have potential to affect the eye muscles that keep the eyes aligned. At birth, a difficult delivery can cause trauma to the child’s head, including trauma to the orbital cavity that surrounds the eye or a forceps delivery.
Later in life, fracturing the orbital bones that surround the eye from fighting or high impact sports can also affect the muscles. Complications secondary to surgery such as cosmetic or eye procedures may also affect the eye position.
High Glasses Prescriptions Can Cause Strabismus
In some cases, a glasses prescription is the cause for an eye turn. For example, children with high hyperopia, or farsightedness, can exhibit inward turned eyes as the focusing systems in their eyes attempt to achieve visual clarity.
Our optometrist will assess a need for glasses depending on the power found and see if it may be helpful. In other cases, children with large refractive differences between the eyes may show an eye turn because they prefer to see through one eye more than the other and thus shut off signals to and from the weaker eye.
In this case, glasses will definitely need to be prescribed and worn full time to promote equal visual stimuli to each eye. If an eye can see more clearly, it often has a better ability to achieve fusion and alignment with the other eye.