Vision Screening Online Training Program

Module 4: Screening for Crossed Eyes (Strabismus)
(C&TC: Often performed by the health care provider)

The four procedures in this module (Observation, Corneal Light Reflection, Cross Cover, Fix and Follow) are all intended to screen for some degree of crossed eyes (called Strabismus). Eyes may cross or turn for various reasons, the goal of screening is to note if an eye crosses and if so, refer to an eye professional. The screener may observe either one or both eyes turning or crossing. The eyes may always turn/cross or may only turn occasionally (i.e. when tired or under stress).

If any eye is always turned or crossed, it is termed a tropia. If any eye only occasionally turns, it is called a phoria. In addition, the direction of the way the eye turns should also be noted. For example, if an eye turns in towards the nose, it is called ‘eso’, if the eye turns out towards the temple, it is called ‘exo’. If the eye turns upward, it is called ‘hyper’ and if the eye turns down, it is called ‘hypo’.

If the eye is always turned IN towards the nose, it is called esotropia. If it only occasionally turns IN, it is called intermittent esotropia.

If the eye is always turned OUT towards the ears, it is called exotropia. If it only occasionally turns OUT, it is called intermittent exotropia.

If the eye is always turned UP towards the eyebrows, it is called hypertropia. If it only occasionally turns UP, it is called intermittent hypertropia.

You may note an eye turning DOWN. This is called hypotropia, or intermittent hypotropia if it is occasional. This is very rare.


The test of Observation is the chance for the screener to check for constant strabismus.

Ages: 4 months through 8 years (C&TC) or 3rd grade (Early Childhood and school screenings).

Observing alignment (See Examples of Strabismus).

It is important that if the child wears prescription glasses that they have them on because the prescription glasses may already be correcting a previous diagnosed crossed eye. Please note, in the two pictures of the same child, you will see how the eye is turned in when the glasses are off, but then when the glasses are on, the eyes are straight (See Example of Child Wearing Glasses).

Equipment: No equipment is needed.
Facilities: Well-lighted room.
Procedure: The screener observes the child's eyes to see if one eye appears to turn in, out, up, or down in relation to the other. The position of the head for tilt (chin up or down) should also be noted.
Pass: The eyes are properly aligned and head position is normal.

One eye appears to turn in, out, up, or down in relation to the other.

Images of Strabismus: Esotropia, Exotropia, Hypertropia, and Hypotropia.

A child with an abnormal head position should also be referred as it may be indicative of an eye disorder leading the child to tilt his/her head to improve their view.

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