An eye that is constantly turned toward the nose is in esotropia. The prefix eso- means the eyes go in. The ending -tropia means a manifest deviation, one that is present under normal conditions. This child has a right esotropia, because the right eye is the one that rests inward while the left eye fixes on the toy.
Compare the two endings. If the same inward turn were not present normally but was brought out during the exam by stopping both eyes from fixating together, it would be called an esophoria. That is a latent deviation. So all tropias are manifest and all phorias are latent. Misalignment is also sorted by how it behaves in different directions of gaze. Comitant deviations measure the same in all fields of gaze, and most childhood strabismus is comitant. Incomitant deviations change with gaze direction and often come from a nerve or mechanical problem. Children rarely report double vision, because a developing brain can ignore the second image. Adults lose that ability, so a new eye turn in an adult usually comes with a complaint of double vision.
Two questions name any eye turn. Which way does the eye rest, and is the turn there with both eyes open? Examine a young child with one look and one toy, since children lose interest fast. Cover the fixing eye and watch the other one; a refixation movement confirms that the turn is manifest. Test at distance and at near, and never use a bright light as the target, because bright light is irritating to the patient. Recognizing and naming childhood eye turns is part of the COA ocular motility testing content area.
Incorrect Answers
- B. Exotropia is an eye that rests outward, away from the nose. That is the opposite horizontal direction from this child's eye.
- C. Hypertropia is a vertical deviation with the eye turned up. It says nothing about an inward turn.
- D. Hypotropia is a vertical deviation with the eye turned down. This child's eye drifted toward the nose instead.
Testing Pearls
- Eso- means in, exo- out, hyper- up, hypo- down.
- An inward turn that is always present is esotropia; one hidden by fusion is esophoria.
- Most childhood strabismus is comitant, measuring the same in all fields of gaze.
- Children usually do not report diplopia, because the brain can ignore one image.
- Use one look and one toy when testing a young child's eye movements.
References
- American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 9, Ocular Motility.
