Amsler Grid, Extraocular Muscle Movements, and Confrontational Visual Fields

Clinical Foundations I

Besides visual acuity, what entrance tests are typically performed on all patients (regardless of CC)?

Amsler Grid, EOMs, and CVF — generally grouped together and performed in succession.

Define Extraocular Muscles (EOMs).

Movements of the eyes controlled by six extraocular muscles.

What are versions, vergences, and ductions?

• Versions: binocular movements where both eyes move in the same direction.

• Vergences: movements where both eyes move in opposite directions (e.g., convergence).

• Ductions: monocular eye movements.

Define the six main EOM movement terms.

• Abduction: away from midline (away from nose).

• Adduction: toward midline (toward nose).

• Elevation: upward.

• Depression: downward.

• Intorsion: rotation toward the nose.

• Extorsion: rotation away from the nose.

Which muscle abducts the eye and where does it insert?

Lateral Rectus (LR); inserts on lateral side of the eye.

Which muscle adducts the eye and where does it insert?

Medial Rectus (MR); inserts on medial side of the eye.

What is the primary and secondary action of the Superior Rectus (SR)?

Primary: elevation.
Secondary: intorsion and adduction.
(It inserts on the top of the eye at 23° to the line of sight.)

What is the primary and secondary action of the Inferior Rectus (IR)?

Primary: depression.
Secondary: extorsion and adduction.
(It inserts on the bottom of the eye at 23° temporal to line of sight.)

What is the primary and secondary action of the Superior Oblique (SO)?

Primary: intorsion.
Secondary: depression and abduction.
(It attaches to upper temporal region at a 54° medial angle.)

What is the primary and secondary action of the Inferior Oblique (IO)?

Primary: extorsion.
Secondary: elevation and abduction.
(It attaches to lower temporal region at a 51° medial angle.)

What are the general rules for EOM actions?

• Superiors always intort.

• Inferiors always extort.

• Obliques’ primary action is torsion.

• Obliques’ secondary action is abduction.

What are the two main purposes of eye movements?

• To move the eye so the fovea aligns with an object of interest.

• To hold images steady on the retina.

What is primary gaze vs. cardinal positions?

Primary gaze: looking straight ahead.
Cardinal positions: six positions testing the primary action of each EOM.

How do you isolate oblique vs. rectus muscles during testing?

Obliques: have patient look toward the nose (adduct).
Recti: have patient look away from the midline (abduct).
(“O’s to Nose.”)

Which muscles are tested in right gaze?

Right lateral rectus & left medial rectus.

Which muscles are tested in left gaze?

Left lateral rectus & right medial rectus.

Which muscles are tested in up-right gaze?

Right superior rectus & left inferior oblique.

Which muscles are tested in up-left gaze?

Left superior rectus & right inferior oblique.

Which muscles are tested in down-right gaze?

Right inferior rectus & left superior oblique.

Which muscles are tested in down-left gaze?

Left inferior rectus & right superior oblique.

Which cranial nerves innervate the EOMs?

• LR = Abducens (CN VI)

• SO = Trochlear (CN IV)

• All others = Oculomotor (CN III)
  Mnemonic: (LR6 SO4)3

What happens with a CN III lesion?

Eye deviates down and out, ptosis, and loss of pupillary reflexes (sometimes)

What happens with a CN IV lesion?

Eye turned upward, vertical diplopia, inability to look down and in.

What happens with a CN VI lesion?

Eye turned inward (strabismus), horizontal diplopia, inability to look laterally.

What is Duane’s Retraction Syndrome?

A congenital condition (most common in left eye of females) caused by structural muscle abnormalities or innervation defects.

• Type I: limited abduction.

• Type II: limited adduction.

• Type III: limited both.
  Associated with globe retraction and fissure narrowing on adduction; usually presents with esotropia in primary gaze.

What is the purpose of EOM testing?

To assess the patient’s ability to perform conjugate eye movements.

What are the evaluation techniques for EOMs?

• Single H Pattern.

• Double H Pattern.

• Rotations (smooth pursuits).

What equipment is used for EOM testing?

Transilluminator, target at 40 cm, good lighting; use pictures for children.

What instructions are given during EOM testing?

“Follow the target with your eyes only, don’t move your head.”

What should you observe during EOM testing?

Smoothness, range, accuracy, presence of jerky movements, lag, restrictions, pain, or diplopia.

How are normal and abnormal EOM results recorded?

• Normal: “EOMs smooth & full, no pain or diplopia” or SAFE (Smooth, Accurate, Full, Extensive).

• Abnormal: specify findings, e.g., “EOMs: diplopia, right eye lags on left superior gaze.”

State Hering’s Law.

Yoked muscle law: equal innervation is sent to corresponding muscles of both eyes during movement.

State Sherrington’s Law.

Agonist and antagonist muscles of the same eye are reciprocally innervated (one contracts while the other relaxes).

What is nystagmus?

Involuntary back-and-forth movement of one or both eyes, disrupting fixation.
Can be horizontal, vertical, or torsional; may be physiologic or pathologic.
End-point nystagmus occurs in extreme gaze positions, more in horizontal than vertical.

What is positional alcohol nystagmus (PAN)?

Nystagmus induced by alcohol affecting semicircular canals.

• PAN I: nystagmus to same side as head position.

• PAN II: nystagmus to opposite side during alcohol elimination (hangover phase).

How is endpoint nystagmus used in sobriety testing?

Police check lateral gaze positions; nystagmus within 30° of center indicates excessive ethanol consumption.

What are the types of screening visual fields tests?

Humphrey (40, 60, 120 point), Humphrey FDT (30°), Tangent screen (25–30°), Amsler Grid (5°), Confrontation fields (180°), Finger counting fields (30–45°).

What is the purpose of visual field screening?

To detect large or substantial unnoted field loss (not sensitive to early disease).

How is confrontation finger counting performed?

• Patient covers one eye, doctor covers opposite eye.

• Patient looks at doctor’s open eye.

• Doctor presents 1, 2, or 4 fingers in each quadrant midway between.

• Patient reports number. (Never use 3 fingers.)

How should finger counting be performed to avoid errors?

Fingers must be within 15–20°, brightly lit, not wiggled, pointing toward center, crossing midline in Z pattern.

How are confrontation visual fields recorded?

“CVF: FTFC OD, OS” (Full to Finger Count). If abnormal, note restriction and location (temporal, nasal, inferior, superior etc)

What is the purpose of the Amsler Grid?

To assess the macular region (central 5°). Useful for patients >50, diabetics, macular disease, or on toxic meds.

What are the types of Amsler Grids?

• Standard white on black.

• White on black with fixation X (for central scotomas).

• White on black with central half grid (small juxta/paracentral scotomas).

• Red on black (early drug toxicity).

• Black on white (detect small floaters).

How is Amsler Grid testing performed?

• Patient covers one eye.

• Wears best near correction.

• Holds grid at 30 cm (not 40 cm like other near tests).

• Fixates on center dot.

• Asked about corners, straightness of lines, missing/wavy/distorted squares.

• Must maintain fixation throughout.

How is Amsler Grid recorded?

Examples:

• “Amsler OD/OS: No metamorphopsia, scotoma, or defects.”

• “Amsler OS: Missing upper left corner.”

• “Amsler OD: (+) central metamorphopsia, (+) defect; OS neg. Plot attached.”