The examination includes the following checks:
• Visual acuity (VA).
• Eye movements.
The examination of the eyes begins by sitting or standing in front of the patient (except when checking the pupils). Note any asymmetry of the eye globe or the presence of droopy eyelids (ptosis).
If Ptosis Is Found, What Does It Mean?
• Isolated, fixed, unilateral ptosis is usually congenital or because of old eye trauma.
• Elderly individuals may have droopy eyelids because of laxity of eyelid muscles.
• Ptosis with an abnormality of pupils is seen in patients with Horner’s syndrome or CN III nerve palsy.
• Fluctuating, unilateral, or bilateral ptosis is suggestive of myasthenia gravis.
• Do not mistake ptosis from eye closure weakness in Bell’s palsy.
Make the Following Observations When Checking Pupils
A. Any asymmetry of size or anisocoria.
B. Any asymmetry to the direct and consensual light reflex.
C. Any irregularity of pupillary border.
D. Check pupillary reaction to accommodation.
E. Do the swinging-flashlight test by shifting between two eyes rapidly and repeatedly to see if one pupil remains dilated as compared to the other.
Remember: The afferent pathway for pupillary light reflex is the optic nerve (CN II), and for the accommodation is the frontal lobes, but the efferent pathway for both are the parasympathetic fibers of the CN III. Examine the pupil in a semidark room and do not stand in front of the patient; have the patient fixate the eyes on a distant object while you shine the light obliquely at the pupils.
Common Pupillary Abnormalities
A. Anisocoria up to 2 mm in an awake and normal person is a normal variant. In an unconsciousness patient, it should be considered abnormal until proven otherwise.
B. Elderly individuals usually have smaller pupils.
C. Marcus-Gunn (M-G) pupil, or afferent pupillary defect, is when one pupil does not constrict as compared with the other eye when you swing the light. M-G pupil is indicative of an optic nerve (CN II) lesion anterior to the chiasm such as optic neuritis. M-G pupil is always unilateral.
D. Horner’s syndrome consists of miosis, ptosis, and anhydrosis. Horner’s syndrome can arise from any lesion from the hypothalamus to the superior cervical ganglion in the neck, and is commonly seen in neck pathologies. Try to localize the lesion by doing a cocaine-and-amphetamine test to differentiate a first-order neuron from a third-order neuron.
E. Adie’s pupil is a common finding and is seen in young, healthy women. One eye is dilated and has poor reaction to direct light but is better to accommodation. Some patients may have hyporeflexia (knee jerk) on the same side (Adie–Holmes syndrome).
F. Argyll–Robertson pupils are small and bilateral, with poor reaction to direct light but react to accommodation. Argyll–Robertson pupils are caused by a midbrain lesion, and are seen in syphilitic tabes and diabetes.