Eye Assessment: Visual Acuity, Extraocular Muscles, and Pupil Reflexes

What is the purpose of the Snellen Eye Chart?

To test visual acuity for distant vision.

What is the procedure for using the Snellen Eye Chart?

Position the person 20 feet from the chart, leave glasses/contacts on, shield one eye at a time, read the smallest line possible, and record the lowest line read with at least 50% accuracy.

What are the four straight (rectus) muscles of the eye?

Superior rectus, inferior rectus, medial rectus, lateral rectus.

What is the function of the superior rectus muscle?

It moves the eye up.

What is the function of the inferior rectus muscle?

It moves the eye down.

What is the function of the medial rectus muscle?

It moves the eye inward.

What is the function of the lateral rectus muscle?

It moves the eye outward.

What are the two slanting (oblique) muscles of the eye?

Superior oblique and inferior oblique.

What is the function of the superior oblique muscle?

It moves the eye down and outward.

What is the function of the inferior oblique muscle?

It moves the eye up and outward.

How are Snellen Eye Chart results recorded?

As a fraction (e.g., 20/30), where the top number is always 20, indicating the distance in feet from the chart.

What does a 20/20 vision indicate?

Normal visual acuity.

What should be done if a person cannot read the largest letters on the Snellen chart?

Reduce the distance to the chart and check if they can count fingers, see hand movements, or perceive light.

What does the acronym PERRLA stand for?

Pupils Equal, Round, Reactive to Light and Accommodation.

What does a normal PERRLA assessment indicate?

Normal pupil assessment findings.

What are the characteristics of a normal iris?

Color varies from person to person; shape should be round and regular.

What causes pupil constriction?

Parasympathetic stimulation (CN III).

What causes pupil dilation?

Sympathetic stimulation.

What is the pupillary light reflex?

An involuntary reflex where the pupil constricts in response to bright light.

What is the direct light reflex?

Contraction of the pupil in the eye exposed to bright light.

What is the consensual light reflex?

Simultaneous constriction of the other pupil not directly stimulated.

What is accommodation in eye physiology?

The adaptation of the eye for near vision by increasing the curvature of the lens.

What is convergence in eye assessment?

The motion of the eyeball axes toward each other.