Physical Examination of the Eye

Clinicians must be able to recognize several specific patterns of vision loss:

• Scotomata: Specific areas of vision loss within the field.
• Blind eye: A total loss of vision in one eye.
• Hemianopia: The absence of half of the visual field.
• Bitemporal hemianopia: A defect affecting the temporal (outer) visual fields of both eyes.
• Homonymous hemianopia: A defect occurring in the same field of both eyes.
• Homonymous quadrantanopia: Loss of vision in only one quadrant of the visual field, often colloquially referred to as "pie in the sky".

Ocular Motility and Alignment

Ocular motility assessment evaluates the function of the extraocular muscles and the integrity of the cranial nerves that innervate them.

The Six Cardinal Positions of Gaze

To test the coordination and strength of the extraocular muscles, the clinician directs the patient to follow a target through the six cardinal positions of gaze. This helps ensure that all muscles—including the medial, lateral, superior, and inferior recti, as well as the superior and inferior obliques—are functioning correctly.

Strabismus

The clinician also assesses eye alignment to check for strabismus (misalignment). Common types include:

• Esotropia: The eye turns inward.
• Exotropia: The eye turns outward.
• Hypertropia: The eye turns upward.

Exam Tip: To assess alignment, perform a "cover test" and observe the location of the reflected light on the corneas.

Pupillary Function

The examination of the pupils provides vital information regarding neurological health and autonomic function.

Pupillary Light Reflex

This reflex is assessed by shining a light into the eye and observing two distinct responses:

1. Direct response: The constriction of the pupil in the eye receiving the light.
2. Consensual response: The constriction of the pupil in the opposite eye when the light is shone into the first eye.

Accommodation Reflex

The accommodation reflex is tested by asking the patient to shift their focus from a distant object to a near target. A normal response involves two simultaneous actions:

1. The eyes converge (move inward toward the nose).
2. The pupils constrict.

Ophthalmoscopic Examination

An ophthalmoscopic exam allows for the visualization of the internal structures of the eye, including the optic disc, macula, and retina.

The Optic Disc

The optic disc is the intraocular portion of the optic nerve. It should appear pinkish to yellow-orange with sharp, round, or slightly oval margins. The center of the disc contains a funnel-shaped depression called the cup. In a healthy eye, the cup should be approximately 1/3 the size of the disc; however, an increased cup-to-disc ratio is often seen in patients with glaucoma due to increased intraocular pressure.

The Retina and Vasculature

The retina contains various blood vessels that originate from the optic disc. During inspection, clinicians look for:

• Arteries vs. Veins: Arteries typically appear thinner and brighter than veins.
• Arteriovenous (AV) nicking: An indicator of hypertensive retinopathy.
• Cotton wool spots: White lesions caused by microinfarcts in the retinal nerve fibers, often associated with diabetes or hypertension.
• Hemorrhages: Red lesions on the retina.

In cases of diabetic retinopathy, the clinician may observe micro-aneurysms, vessel tortuosity, and exudates, which can lead to macular edema and blindness. Conversely, papilledema refers to the swelling of the optic disc, which results in blurred margins and is a clinical sign of increased intracranial pressure.