Figure 10-7 A, Right Adie tonic pupil. B, After instillation of pilocarpine (0.1%), the right pupil becomes miotic, demonstrating supersensitivity. (Courtesy of Lanning B. Kline, MD.)
Patients with tonic pupils may have accommodative symptoms or photophobia but just as often have no symptoms and report that anisocoria was first noticed by a friend or relative. Accommodative symptoms are difficult to treat. Fortunately, they usually resolve spontaneously within a few months of onset. When photophobia from a dilated pupil is a problem, topical dilute pilocarpine (0.1%) may be helpful. With time (months to years), an Adie tonic pupil gets smaller. Histologic examination of the ciliary ganglion in patients with Adie tonic pupil has shown a reduction in the number of ganglion cells.
Kardon RH, Corbett JJ, Thompson HS. Segmental denervation and reinnervation of the iris sphincter as shown by infrared videographic transillumination. Ophthalmology. 1998;105(2):313–321.
Third nerve palsy
Pupillary involvement in third nerve palsy is almost always accompanied by ptosis and limited ocular motility. At times, the motility disturbance may be subtle, requiring careful quantitation with alternate cover testing. Pupillary dysfunction is an important factor in evaluating acute third nerve palsy. When the pupil is involved, an aneurysm at the junction of the internal carotid and posterior communicating arteries must be excluded (see Chapter 2., Fig 2-11). If the pupil is spared and all other functions of the third nerve are completely paretic, an aneurysm can likely be ruled out.
Aberrant regeneration of the oculomotor nerve may cause mydriasis and a synkinetic pupillary reaction. (See images provided by The Neuro-Ophthalmology Virtual Education Library, available at http://novel.utah.edu.) Portions of the pupillary sphincter contract with attempted movement of the eye, especially medially.
For additional discussion of third nerve palsy, see Chapter 8.
Czarnecki JS, Thompson HS. The iris sphincter in aberrant regeneration of the third nerve. Arch Ophthalmol. 1978;96(9):1606– 1610.
Disorders of Pupillary Reactivity: Light–Near Dissociation
Light–near dissociation occurs when a near response exceeds the best pupillary constriction that
bright light can produce. This finding may arise from a variety of causes (Table 10-1).
Table 10-1
Afferent Visual Pathway
Optic neuropathy is the most common cause of light–near dissociation (unilateral or bilateral). In optic neuropathy, light–near dissociation is the result of damage to only the afferent limb of the pupillary light reflex (optic nerve); the central near impulses remain unaffected.
Midbrain
Dorsal midbrain damage can result in midsize pupils with poor light response and preserved near response. Such responses occur when the lesion spares the more ventrally located fibers of the near reflex pathway. Associated findings include bilateral eyelid retraction (Collier sign), vertical gaze palsy, accommodative paresis, and convergence-retraction nystagmus (Parinaud syndrome) (see Chapter 7, Fig 7-5).
The Argyll Robertson pupil occurs in patients with tertiary syphilis involving the central nervous system. Affected patients have small pupils (<2 mm) that are often irregular. The pupils do not react to light, but the near response and subsequent redilation are normal and brisk. This feature distinguishes Argyll Robertson pupils from bilateral chronic tonic pupils, which may also result from neurosyphilis. In addition, iris atrophy frequently occurs, portions of the iris transilluminate, and dilation is poor after instillation of mydriatic eyedrops.
Argyll Robertson–like pupils are observed in widespread autonomic neuropathies such as bilateral tonic pupils (chronic), diabetes mellitus, and chronic alcoholism, as well as in encephalitis and after panretinal photocoagulation. Serologic tests for syphilis, such as the serum fluorescent treponemal antibody-absorption (FTA-ABS) test and the Treponema pallidum hemagglutination assay (TPHA), should be considered in the evaluation of patients with bilateral pupillary light–near dissociation with miosis.
Aberrant Regeneration
Light–near dissociation can also result from aberrant regeneration of damaged nerves that restores the near reflex but not the light reflex. In tonic pupil syndrome, the injured short ciliary nerves resprout and accommodative fibers mistakenly reinnervate the iris sphincter. Similar misdirected growth can