What are the main components of the eye that should be assessed during a physical exam?

A proper eye exam evaluates the eyelids, sclera, conjunctiva, iris, pupil, and lacrimal structures. The upper eyelid should slightly overlap the iris without covering the pupil, while the lower lid lies below the iris. The sclera normally appears white or slightly buff. The conjunctiva, a transparent membrane covering the anterior sclera and inner eyelids, is a sensitive indicator of ocular disorders like infections and inflammation.

How does the tear drainage system work in the eye?

Tears are produced by the lacrimal gland, located above and lateral to the eyeball. They spread across the eye and drain medially into two lacrimal puncta, then pass into the lacrimal sac and nasolacrimal duct before reaching the nose. This drainage pathway is essential for maintaining eye moisture and health.

What role do cranial nerves play in eye function and movement?

Cranial nerves II and III control pupillary reaction and lens accommodation. Cranial nerve III controls upper lid elevation, while cranial nerves III, IV, and VI control eye movement. These nerves innervate the six extraocular muscles that direct gaze in all cardinal directions, making them essential for coordinated eye function and visual assessment.

How does the iris and ciliary body regulate vision?

The iris divides the anterior from the posterior chamber and contains muscles that control pupil size. The ciliary body, located behind the iris, contains muscles that control the focal length of the lens and produces aqueous humor, which largely determines intraocular pressure. Together, these structures regulate how light enters the eye and focuses on the retina.

What happens to light as it travels through the eye to the retina?

Light passes through the cornea, pupil, lens, and vitreous body before projecting a focused image onto the retina. This image is inverted and reversed right to left, meaning light from the lower temporal visual field strikes the upper nasal retina. Photosensitive retinal cells then generate electrical impulses relayed to the optic nerve and visual cortex.

How do the visual cortices process images from different visual fields?

Electrical impulses from the retina travel through the optic nerve and optic tracts to reach the visual cortex. The right and left visual cortices process images entering from the left and right visual fields, respectively. This crossed processing allows the brain to integrate visual information from both eyes into a unified perception.

Why is visual testing an important part of the eye exam?

Visual testing is essential for assessing cranial nerve II function and detecting vision problems during ophthalmoscopic functioning and examination. It evaluates how well light focuses on the retina and whether the visual pathway from the eye to the brain functions properly. This testing provides critical information about overall eye health and neurological status.

Eye Exam

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1. Vision

Visual acuity is recorded as two numbers (e.g., 20/40 corrected). The top number indicates the distance the patient stood from the chart (20 ft), and the bottom number indicates the distance from which a person with normal vision (20/20) could see the smallest line of print accurately read by the patient (40 ft with glasses). In the US, a patient with vision of 20/200 or worse is considered legally blind.

If available, use a well-lit, wall-mounted Snellen chart.
Position the patient 20 ft from the chart with non-reading glasses on (if normally used).
Have the patient cover one eye with a card, and ask the patient to read the smallest line of print possible; give credit for correctly identifying half or more of the letters.
Record the visual acuity indicated to the side of this line, noting whether it was with correction or not.
Repeat with the other eye.
If a wall-mounted chart is unavailable, conduct the same procedure with a specially designed card the patient can hold 14 inches away ( Figure 4), which simulates the view of a Snellen chart from 20 ft away. The card can also be used to test for presbyopia, or impaired near vision, common in people as they reach middle age; in presbyopia, vision improves when the card is held further away.
In the absence of a chart or card, screen for visual acuity using any fine print.
Peripheral vision.
1. Begin by asking the patient to use both eyes to stare at your eyes without looking anywhere else.
2. Place your hands, with two fingers raised, lateral to the patient's ears, about 2 ft apart.
3. Wiggle your fingers and bring them slowly forward, curving slightly inward toward the center of vision.
4. Ask the patient to tell you when the movement of your fingers can be seen in the periphery. Normally, this occurs when your fingers are even with the patient's temples or about 90° from the center of gaze on either side.
5. Increase the accuracy of this exam by slowly moving a 5-mm, red-topped pin inward along the lines projecting from the four corners of the patient's visual field, noting when the patient can first see the color in each of the four quadrants.

2. Eye Inspection

Stand in front of the patient and ask the patient to stare directly at you.
Observe the eyes for any asymmetry or protrusions.
Inspect the eyebrows for sparseness or scaliness and the eyelids for adequate closure, ptosis, entropion, ectropion, retraction, discoloration, lesions, swelling, masses, or discharge.
Check for dryness or excessive tearing, and examine the lacrimal gland and sac for swelling or tenderness.
Expose the conjunctiva and sclera by having the patient look upward while gently pulling downward on the lower lids with your thumbs. Note color, vascular dilations, nodules, swelling, or discharge.
Shine a penlight obliquely across the cornea, noting any surface irregularities or opacities. Inspect the iris for rings, shadows, or ciliary injection, and inspect the lens for opacities.
Inspect the pupils for their size, shape, and symmetry. Pupils are normally 3-4 mm in diameter. In anisocoria, the pupil diameters are unequal by at least 4 mm. The terms myosis and mydriasis refer to abnormally constricted or dilated pupils, respectively.
Have the patients stare at a penlight held about 20 cm away. Note the position of the corneal reflections, which should be symmetrically located just nasal to the center of the pupils.
Check for pupillary reaction to light by asking the patient to stare off into the distance in a slightly darkened room. Observe the patient's right pupil while swinging the penlight from right to left across the patient's right eye. It should constrict. Now, do the same maneuver while observing both eyes, taking care not to allow any light to fall on the patient's left eye. Both pupils should consensually constrict. Repeat this testing for the left eye.
Examine the extraocular motion by asking the patient to look at your index finger and follow it as you trace the shape of a large "H" at a comfortable distance in full light. Make sure the patient's head remains still. Both eyes should symmetrically move through all cardinal directions of gaze.
Momentarily hold the patient's gaze at the extreme upper, lateral positions, and observe for nystagmus, which appears as involuntary rhythmic oscillations of the eyes.
Check for lid lag by looking for an abnormal rim of sclera over the iris on downward gaze.
Finally, have the patient stare at your finger as it moves toward the bridge of the patient's nose, and watch for equal convergence of the eyes medially and equal pupillary constriction.
If the pupils don't react, hold your finger about 10 cm away and ask the patient to alternately stare at your finger and into the distance beyond it. The pupils should constrict while focused on your finger.