Strabismus

Eyes Don't Point in the Same Direction

For some patients this happens all of the time with one eye (constant, unilateral)

For some patients this happens all of the time, but the eye that turns can change (constant, alternating)

For some patients this only happens sometimes (intermittent)

Sometimes one eye is pointing out, towards the ear, compared to the eye that is doing the looking (exotropia)

Sometimes one eye is pointing in, towards the nose, compared to the eye that is doing the looking (esotropia)

Sometimes the eye is only pointing in or out when you are looking at a specific direction (non comitant)

Sometimes the eye is pointing in or out by the same amount regardless of which direction you are looking (comitant)

When Did the Eyes First Start to Turn?

If the eye turn started at birth or at a young age it is usually caused by an abnormal development of the binocular vision system

If the eye turn started at an older age (around 60 years old) in a patient with medical conditions (diabetes, hypertension, etc.) it can be a consequence of the underlying health or it can be a symptom of a new medical problem (tumor inside of bony orbit, damage to nerves controlling a specific eye muscle)

If the eye turn started around 40 years old, in a healthy patient, it could be the result of a mild mis-alignment of the eyes, which the eye muscles had previously been able to compensate for, but are now losing their compensating ability (de-compensating phoria)

What Do We Do About the Eye Turn?

We can try eyeglasses with or without prisms to relieve some of the tension on the eye muscles

We might just ignore the problem if it is not happening all of the time (intermittent) or if it is not causing annoying double vision symptoms

We might try going through a vision therapy program to help strengthen the eye muscles and how they work together

With a large, constant eye turn, we might talk to a strabismus surgeon about moving the eye muscle attachments to the eye, to surgically help with eye alignment

For older patients who have an eye turn as the consequence of an underlying health problems, we can try to improve the root problem (better glucose or blood pressure control with medications) and wait to see if the eye turn corrects itself

For patients experiencing double vision (not all patients will experience this) we can use a patch to cover one of the eyes as a temporary relief until we figure out another solution

How Do Prisms Work?

Prisms shift the world side to side or up and down

If one of your eyes is pointed slightly up or to the right, we can shift the light entering that eye slightly up or to the right, so that the two eyes are seeing the same thing, even though they are not pointing the same way

The eyeglass prescription will include a number (in prism diopters) and a direction (base in, base out, base up or base down)

5 BI (base in prism) can be ground in to the right lens,  to the left lens, or split between the two lenses (2.5 BI in each eye)

That is also true for base out prism

2 BU (base up prism) must be specified which eye, if the base up prism is ground in to the wrong lens, it will have the opposite affect (makes the double vision worse)

That is also true for base down prism

Temporary prism can be used in the form of a stick on prism: https://www.bernell.com/product/A/Press_On

What is a Phoria?

A mild mis-alignment of the eyes, which the eye muscles are able to compensate for by pulling the eyes in, or out, or up, or down

This compensation can cause the eyes to feel tired, or feel tension (strain)

The eyes may never turn out, but the tension required to keep them aligned can cause discomfort

Treatment for a symptomatic phoria includes vision therapy for some specific types, or prisms