Vision Screening Online Training Program
Module 4: Screening for Crossed Eyes (Strabismus)
(C&TC: Often performed by the health care provider)
The three procedures in this module (Corneal Light Reflection, Unilateral Cover Test, 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 Corneal Light Reflex test is used to check for milder forms of constant strabismus.
Corneal Light Reflex
Zero months through 20 years of age.
To check for milder degrees of constant strabismus. To differentiate pseudo-strabismus in children with large epicanthal folds.
By noting the position of light being reflected in the pupils, the observer is able to check for a constant strabismus.
Penlight and target object.
Can be performed by screeners with recommended training.
Normal or lower light level. Minimize, if possible, the number of light sources (i.e. windows, overhead lights, etc.).
- Position the child so that the target, the light source, and the examiner's line of vision is at the midline in front of the child's eyes at a distance of 14-16 inches.
- Try to have the child sit with his/her back to any ceiling lights.
- Shine the penlight at the center of the child's forehead directly above and between the child's eyes.
- Make sure the child is focused on the target.
With the child's gaze fixed on the target object (toy), the penlight should be resting on the target object and shining directly above the child's eyes. The distance between the light and the child's face should be about 14-16 inches
- The screener then observes the reflected light in each pupil.
Example: The white spots in each pupil are actually the reflection of the light from the penlight that is being shined in the eyes.
- It is very important that good light is used. Ceiling lights are not sufficient.
A note about facilities:
Ensure a normal or lower light level with a minimum number of light sources (windows, overhead lights, etc.) The child's back should be to any light source in the room to avoid extra reflection of light in the eyes. This next example shows how the reflection should appear (if normal) and how other light sources may confuse the interpretation.
Note: The main light reflection is in the same position in each eye. Also note the extra light reflections in both eyes that are due to the reflection of the ceiling light.
The reflection of the light appears to be in a symmetrical position in the pupil of each eye.
The reflection of light appears to be in an asymmetrical position in one eye compared to the other go to Abnormal corneal Light Examples.
Sometimes an eye may look crossed when it is not. This is called pseudo-strabismus. Pseudo-strabismus is most often found in infants due to a wide, flat nose and a fold of skin at the inner eyelid (called epicanthal folds) that makes the eyes appear crossed (go to Example of Pseudo-Strabismus). Prominent epicanthal folds, together with an upward, outer slant of the eyelids are common in Asian children, but may be suggestive of Down syndrome in children of other ethnic groups.
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