Extraocular muscle function testing

Extraocular Muscle Function Testing

Extraocular muscle function testing is a procedure used to examine the functioning of the eye muscles. It helps to detect any abnormality in the functioning of the eye muscles, deficits caused by cranial nerve palsy or dysfunctions of the brain and nerves which connect the eye with the brain. It is generally conducted in patients with a squint or strabismus and to diagnose any neurological problem of the eye.

Preparation

Before beginning the test, the patient is asked to remove contact lenses, jewelry or any other item that may interfere in the testing process.
The patient is asked to fixate on the target object and is also given instructions on the same.
The patient’s pupils are examined to detect the functioning of the parasympathetic and sympathetic nervous systems that control the size of the pupils.
The patient is given topical drops of cycloplegic before starting the test, which helps to relax the ciliary body and reduce any refraction error.

Procedure

In the extraocular muscle function, test one eye is covered at a time and the unmasked eye is monitored to measure the range of movement and the speed of movement of the eyeball.
The eyes are moved to various directions and the muscles attached to the eyes are observed for any signs of weakness.
The observations are recorded with help of a prism bar and a slit lamp biomicroscope.

Types

The Hoffman"s reflex test is done to observe the functioning of the medial rectus muscle and the sixth cranial nerve.
A Chemical reflex test is conducted to measure the degree of displacement caused by a prism.
In Forced duction test, the globes are manually moved to observe any resistance.
The Brown's Finger test measure the amount of duction and assesses the movement of the eye.
The Bell's Palsy test measures the occurrence of any anisocoria.

Risks

The common risks associated with the extraocular muscle function test are discomfort, dizziness, Alle gic reactions, over dilation or blurred vision due to dilated pupils.
The bulky equipment and the loud noise made by the same might cause discomfort to the patient.

Why

Extraocular muscle function test is generally used to diagnose any form of strabismus or squint in the patient, which is quite common in young children. Furthermore, it is also conducted to either diagnose or confirm any other neurological problem such as Bell's palsy, Oculomotor nerve palsy, superior or inferior oblique palsy, or any muscle imbalance.

When

Extraocular muscle function test is generally conducted when the patient shows any visible sign of movement of the eyes, like a squint. It is also conducted when the patient is suspected of any neurological disorder, especially a condition that can affect the muscles of the eye or the cranial nerve which supplies the muscles with signals.