• 
  

  OVERVIEW AND TERMINOLOGY

  
  
• 
  

  GENERAL OBSERVATIONS

  
  
• 
  

  OCULAR MOTILITY

  
  
  
  
  • 
    

    Fixation

    
    
  • 
    

    Ocular versions and ductions

    
    
  • 
    

    Vergence

    
    
  • 
    

    Pursuit

    
    
  • 
    

    Saccades

    
    
  • 
    

    Ancillary methods

    
    
  • 
    

    Assessing ocular alignment

    
    
  • 
    

    Forced duction testing

    
    
  • 
    

    Nystagmus

    
    
  • 
    

    Eye movement recording

  
  
• 
  

  PUPILS

  
  
• 
  

  EYELIDS

  
  
  
  
  • 
    

    Examination techniques

    
    
  • 
    

    Ptosis

    
    
  • 
    

    Eyelid retraction

    
    
  • 
    

    Facial nerve disorders

  
  
• 
  

  ORBIT AND ADNEXA

  
  
  
  
  • 
    

    Inspection

    
    
  • 
    

    Palpation

    
    
  • 
    

    Auscultation

  
  
• 
  

  ADDITIONAL ASSESSMENTS

  
  
  
  
  • 
    

    Cranial nerve V

    
    
  • 
    

    Cranial nerve VII

  
  
• 
  

  KEY POINTS

This chapter expands the discussion of examination techniques summarized in Chapter 1 and is a companion to Chapter 2, which discusses examination of the afferent visual system. In this chapter, methods for examining the pupil and cranial nerves (CNs) III, IV, V, VI, and VII are presented, with greater detail provided in other chapters regarding examination of the pupil (chapter 11), CN VII (chapter 12), and CN V (chapter 13).

The purpose of the ocular motor system is to aim the visual axis of each eye at an object of interest. This function places an image of the object on the area of greatest retinal sensitivity: the foveola. Ideally, the motor system keeps the eyes steady and aligned with the fixation object even when the object is moving in three-dimensional space. The smooth tracking of a moving object is called pursuit. When a new object of interest is encountered, the motor system can quickly redirect gaze with a rapid movement to fixate on a new object of interest. This rapid refixation movement is called a saccade. Generally, when following or finding objects, both eyes move in the same direction (conjugate gaze). However, objects that move toward or away from the observer require a disconjugate eye movement (vergence). For example, an object approaching the observer’s nose from a distance requires the eyes to converge, or turn in (right eye turns to the left, left eye turns to the right) to maintain fixation. Divergence occurs in the opposite setting: When the fixation object moves from near to far the eyes move outward—from a converged state to a more parallel alignment. Additional complexity is introduced when the observer is moving or when both the observer and the object are moving in space. Even in this complex situation, eye movement systems can provide stability of fixation, compensating for movement of the observer as an object is tracked.

When binocular fixation occurs, the brain can synthesize depth information from the slightly disparate views of the object (stereopsis). If the motor system fails to provide alignment, the brain cannot reconcile the two images, potentially resulting in confusion and diplopia (Box 7–1).

Six extraocular muscles insert on the globe and act in concert to rotate the eye horizontally and vertically. In addition, the globe can be rotated to a limited extent around the visual axis (torsion) to provide limited compensation for head or environmental tilt.

The extraocular muscles are controlled by CNs III, IV, and VI, which originate in the brainstem. CN III also innervates the levator muscle (for elevating the upper eyelid) and carries parasympathetic input to the pupillary sphincter. The CNs are in turn coordinated by supranuclear regions in the brain. Other components of the efferent visual system include CN VII (the facial nerve), which innervates the orbicularis muscle that closes the eye and the sympathetic system that controls pupillary dilation. A brief discussion of the examination of CN V (trigeminal nerve) is included in this chapter, although it is primarily a sensory (afferent) cranial nerve.

The fine art of observation cannot be detailed in a textbook. The examiner should realize that the examination actually begins when the physician first encounters the patient—observing how the patient ambulates to the examination room, sits in the chair, and shakes the examiner’s hand. Initial observations of the patient’s facial movements, eyelids, and eye movements should be made during the history. Such observations are important because they may be more objective than when the patient is aware that his or her eyes and face are being scrutinized (see Figure 6–12).

A general guide for evaluating ocular motility is presented in Table 7–1.

FIXATION

Fixation describes how the eyes remain trained on a single, stationary distant or near object. Fixation is normally central, with the eye pointed directly at the target object. Patients with central scotomas or anomalous retinal correspondence may display eccentric fixation. Fixation cannot occur if the patient’s poor vision precludes seeing the fixation object. Patients with ocular misalignment may adopt a head turn or tilt, or may close one eye to avoid diplopia when both eyes are attempting to fixate.

Fixation is normally steady, without interruption. Abnormalities include square-wave jerks (brief, back-and-forth, horizontal saccadic diversions) from brainstem or cerebellar disease, or nystagmus.

Normal fixation is also maintained, that is, both eyes remain trained on the target, even if fixation is momentarily broken by a blink or brief occlusion of one eye. In young children, the determination of central, steady, and maintained fixation may be the only clues of central visual function that the examiner can determine. In adults, observations about fixation are usually made during visual acuity testing and throughout the motility examination.

OCULAR VERSIONS AND DUCTIONS

Ocular version testing looks for defects in the full range of conjugate gaze. The test is performed with both eyes open, observing each eye and comparing the two eyes at the extremes of gaze in the cardinal positions (Figure 7–1). The test is performed in a manner that allows observation of the action of each of the extraocular muscles. The actions of the vertically acting muscles are best tested when the eye is in adduction (superior and inferior oblique muscles) or abduction (superior and inferior rectus muscles). Ocular version testing also includes testing straight up and down to look for vertical gaze palsies.

In horizontal gaze, the normal eye can be abducted and adducted such that little or no sclera is visible in extreme gaze. This ability varies somewhat among individuals (especially with age) but normally should be symmetric between eyes. Vertical gaze is more difficult to judge because the eyelids move with vertical eye movements. Upgaze is particularly dependent on age, with increasing deficiency in normal patients with age. The upper eyelids need to be held up by the examiner to fully observe the eyes in the lower gaze positions. (However, it is important at some point to observe the position of the eyelids in downgaze.) The results of the motility examination can be recorded as shown in Figure 7–1.

Ocular duction testing is a monocular test, usually performed with the fellow eye covered, that examines the range of motion of a single eye. Ocular versions are performed first, followed by duction testing when necessary.

VERGENCE

Vergence testing examines the ability of the eyes to track an object from distant to near. It can be measured (in centimeters from the bridge of the nose) as the point at which an approaching accommodative target breaks down and is seen as double, and the point at which fusion is regained when the path of the target is reversed. However, these measurements are entirely dependent on the effort exerted by the patient, making interpretation difficult. Convergence effort can be maximized by having the patient focus on a near-card letter, rather than the examiner’s finger. Another method is to use the patient’s own finger as the convergence object, guided by the examiner from distant to near. Even blind patients can be tested in this manner because proprioceptive clues help the patient achieve convergence.

Convergence occurs by activation of both medial rectus muscles through a different supranuclear pathway than conjugate gaze. Disparities in medial rectus function between convergence and ocular versions may help to localize the lesion as supranuclear. For example, in an internuclear ophthalmoplegia (INO), an adduction deficit is present on attempted lateral gaze, but adduction is usually normal with convergence. This finding usually helps to distinguish the INO from an orbital restrictive process or partial CN III palsy.

Testing convergence is also important when convergence insufficiency is suspected. These patients have an exophoria or intermittent exotropia at near only and complain of vague discomfort (and occasionally diplopia) after extended near tasks. Usually a benign idiopathic condition, convergence insufficiency can also be associated with head trauma.

Convergence testing is also performed to observe the pupillary response to near (see Table 11–2) and should be performed whenever the pupillary light reaction is poor.

PURSUIT

Pursuit testing checks the brain’s supranuclear smooth-tracking mechanisms (discussed in Chapter 10). Pursuit is tested by asking the patient to follow the examiner’s finger or other target as it slowly and smoothly moves between the extremes in the horizontal plane and then in the vertical plane. The pursuit target should be at least an arm’s length from the patient to minimize confounding factors from convergence and accommodation. Abnormal pursuit may be saccadic (choppy) rather than smooth in one or both directions. Pursuit testing can be performed as an integral part of testing ocular versions—observations of how smoothly the patient can track the examiner’s moving finger evaluates pursuit, and the ability of each eye to reach the endpoint at extreme gaze evaluates ocular versions.

SACCADES

Saccades are tested by asking patients to look rapidly from primary position (looking at the examiner’s nose) to a target (the examiner’s finger positioned in right and left gaze in the horizontal plane or straight up and down in the vertical plane). Supranuclear abnormalities may cause hypometric saccades, in which the eyes do not line up on the new fixation target in one quick movement, but require additional smaller saccades to finally arrive on target. Hypermetric saccades, in which the eyes overshoot the target, also occur. Unilateral slow saccades are identified by comparing the two eyes: The slow eye is still moving toward the target after the normal eye has completed its saccade. Unilateral slow saccades are seen in an eye with a neurogenic palsy, in contrast to saccades that are abruptly halted in restrictive disorders such as thyroid eye disease. Slow movement of the adducting eye alone suggests an internuclear ophthalmoplegia (INO). Attempted upward saccades produce convergence-retraction nystagmus in patients with dorsal midbrain syndrome (see Chapter 10).

ANCILLARY METHODS

Optokinetic Nystagmus Testing

Optokinetic nystagmus (OKN) testing was discussed briefly in the context of afferent visual system testing as an objective physiological response to test gross vision (see Table 6–2). The afferent limb of this physiological response begins with a moving visual stimulus, usually alternating black and white stripes on a rotating drum, but any interesting stimuli that are equally spaced at appropriate intervals moving across the visual field will work (Figure 7–2). The efferent limb consists of pursuit of the moving target in one direction and a refixation saccade in the opposite direction to acquire the next target. This test has value as a physiological stimulus that allows observation of saccade and pursuit movements, even in patients who may be incapable of cooperating with other examination techniques. In addition, the rapidly repeating saccades and pursuit greatly increase the clinical sensitivity of detecting abnormalities. When performing an optokinetic test, the amplitude and frequency of the induced nystagmus should be observed, particularly when compared to the response from stimulus movement in the opposite direction. Box 7–2 lists the important clinical uses of the optokinetic response.

Oculocephalic (Doll’s Head) Maneuver

The oculocephalic maneuver helps determine the level of a lesion in a gaze palsy because it uses the vestibular system to move the eyes. The test is performed by rotating the patient’s head in the plane of the gaze palsy while the patient fixates on a stationary object. Patients who are unable to produce a gaze movement with this maneuver have a lesion at or below the level of vestibular input to the efferent visual motor system. Patients with a gaze palsy who can achieve full horizontal gaze with this maneuver but cannot do it volitionally have a supranuclaear palsy. The test can be performed for both horizontal and vertical gaze palsies.