PCM: Eye Exam

=Eye Exam Objectives= Objectives for Principles of Clinical Medicine

Take a focused history

 * Difficulty with vision?
 * Secretions? If so, describe.
 * Pain?
 * Corrective lenses?
 * Cigarette smoking? (Risk for cataract, glaucoma, macular degeneration

Demonstrate assessment of cranial nerves II, III, IV and VI.
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 * Innnervation
 * Cranial nerve II: Optic nerve, special sensory. Tested by visual acuity,
 * Cranial nerve III: Oculomotor. Innervates Sphincter papillae muscle (parasympathetic), levator palpebrae superioris, inferior rectus, medial rectus, superior rectus.  Test patient's ability to track finger. This presents in a variety of ways, but a complete right CN III palsy will look like this when a subject looks ahead.  Note the down and out direction of the eye at rest. Also, it's dilated.
 * Cranial IV: Trochlear nerve innervates superior oblique muscle. The rectus muscles cannot completely compensate for SO.  Patients may see double at edge of vision (down and out) with unilateral defects in the CN IV.  It's also the most difficult to detect in clinic and is associated with vertical diplopia.  It takes 6 images to illustrate this right CNIV palsy:

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 * Cranial nerve V: Trigeminal (V1). Usually tested by sensation to the face.  Also detect light pressure on the sclera (ie cotton) to trigger reflex (CN VII).
 * Cranial Nerve VI: Abducens nerve innervates the lateral rectus. The cartoon/drawing below shows a right CN VI nerve palsy, characterized by the excessive aDDuction at rest and failure of aBDuction when gazing right.

The photograph shows a left CN VI nerve palsy, as the patient looks to the left.
 * Cranial nerve VII: facial nerve innervates palpebral and orbital fibers of the obicularis oculi muscle.


 * Reflexes
 * Corneal light reflex: Tests ability of optic nerve to signal through the parasympathetic fibers of the occular nerve to obscure the pupil.

Make sure to visit the UC Davis Eye Simulator, to prepare for actual test questions.

Examination procedure

 * 1) Inspect eye externally.  Examine sclera as patient looks up and then down.
 * 2) Test visual acuity; read lowest line on the Snell chart
 * 3) Test pupillary contraction to light.  Shine in each eye twice.
 * 4) Test strength eye muscles.
 * 5) Stand or sit 3 to 6 feet in front of the patient.
 * 6) Ask the patient to follow your finger with their eyes without moving their head.
 * 7) Check gaze in the six cardinal directions using a cross or "H" pattern. This isolates the action of the muscles.
 * 8) Check convergence by moving your finger toward the bridge of the patient's nose.

Identify the extraocular muscle and cranial nerve abnormalities for CN III, CN IV, CN VI.

 * Presence of nystygmus, double vision.
 * See above


 * nystygmus
 * involuntary rhythymic movements of the eyes that can occur in horizontile, vertical, or jerky fashion.

Demonstrate the assessment of pupil reactivity including direct and consensual response and interpret the cranial nerve abnormalities that cause abnormal papillary responses.

 * Shine a light into the patient’s pupil and observe both that eye and the contralateraleye for pupillaryconstriction.
 * CN II-senses light
 * CN III-responsible for pupillary constriction
 * Direct pupillary light reflex-light causes pupil to constrict
 * Consensual pupillary light reflex-light causes contra-lateralpupil to constrict


 * Accomodation: pupils constrict while fixating on an object being moved from far away to near the eyes.

Demonstrate the assessment of visual acuity

 * Snell Chart or Rosenbaum Chart may be used. Position patient 10 or 20 feet from the chart, depending on resources.
 * Test one eye at a time, covering with a card.
 * Ask patient to read a full line.

Demonstrate the assessment of visual fields and describe the abnormalities of homonymous hemianopsias, binaslhemionopsia, bitemporalhemaianopsia, and upper and lower homonymous quadrantopsias.

 * Examine peripheral vision one eye at a time.
 * Face patient, 1m away. Ask patient to on your eye or face and NOT to track your fingers.
 * Extend arm with moving fingers. Ask patient to let you know when fingers first appear and when they exit the field of vision. Test all quadrants quickly.
 * homonymous hemanopsias
 * a type of partial blindness resulting in a loss of vision in the same visual field of both eyes. usually caused by injury to the brain itself such as stroke or trauma effecting the optic tract, rather than malfunctioning of the eye itself.
 * Wikipedia


 * binasal hemianopsia
 * Blindness in the nasal field of vision of both eyes.


 * Bitemporal hemianopsia
 * type of partial blindness where vision is missing in the outer half of both the right and left visual field. It is usually associated with lesions of the optic chiasm, the area where the optic nerves from the right and left eyes cross near the pituitary gland.
 * Wikipedia Link

Describe the anatomy of the retina.

 * Fundus: observable retina
 * Fovea: center of macula. point of highest visual acuity
 * Macula: site of central vision in the retina. aka fovea centralis, or macula lutea. located approximately 2 disc diameters temoporally from the optic disc. avascular.
 * optic disc: position in the retina where the optic nerve originates

Describe normal cup-to-disc ratio

 * The disc is a lighter yellow color about 1.5 mm in diameter. The cup comprises the central area of the disc and is typically 1/3 the diameter of the disc.
 * Cup size can increase in glaucoma

Eye Exam Checklist

 * 1) Inspection
 * 2) Visual Tests
 * 3) Visual Acuity
 * 4) Pupillary Responses
 * 5) Convergence
 * 6) Cranial nerves: extraocular motion
 * 7) Peripheral vision
 * 8) Opthalmascope

Unilateral Cranial Nerve Palsies
=References=
 * UC Davis Eye Simulator, actual PCM exam questions may be adapted from this site.
 * UCSD SoM Eye Exam instructions
 * OHSU PCM Eye Exam Checklist