Pupil anomalies and reactions

Chapter 63 Pupil anomalies and reactions



Andrew G. Lee, Megan M. Geloneck, Derrick C. Pau



Chapter contents



DEVELOPMENT


THE NEAR SYNKINESIS


CONGENITAL AND STRUCTURAL ABNORMALITIES


AFFERENT ABNORMALITIES OF PUPIL REACTIVITY


HORNER’S SYNDROME


PUPIL CHANGES FROM HIGH SYMPATHETIC “TONE”


PUPIL CHANGES FROM DAMAGE TO THE PARASYMPATHETIC SYSTEM


PHARMACOLOGICAL AGENTS


ABNORMALITIES OF THE NEAR REFLEX


SPASM OF THE NEAR REFLEX


REFERENCES


The anatomy (Fig. 63.1), physiology, and pathophysiology of the pupillary pathways are important to the pediatric ophthalmologist but they are dealt with so excellently elsewhere that only aspects relevant to children will be discussed here.


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Fig. 63.1 Schematic representation of the efferent and afferent pathways involved in pupillary reactions. Red = blood vessels and parasympathetic. Blue = afferent visual pathways. Green = sympathetic pathway.



Development (see Chapter 2)


The pupillary light response is absent in infants of 29 gestational weeks or less, but is usually present by 31 or 32 weeks.1 At birth the pupil is small. It enlarges in the first months of life and is probably at its largest at the end of the first decade, gradually becoming miotic in old age. The pupil reactions of term or premature infants are often of small amplitude and, because of their small resting size, may be difficult to elicit clinically especially in infants with brown irises. The failure of the pupil grating response in infants under 1 month of age is further evidence of the immaturity of the pupil responses in infancy.2 Cocaine and hydroxyamphetamine are less potent in infants than in older children, suggesting that miosis of the newborn is due to decreased sympathetic tone.3 In very premature babies the pupil may not have fully formed; during the seventh month of gestation, the vascular pupillary membrane atrophies and the pupil appears. Before 32 gestational weeks, mydriasis should not be taken as necessarily indicating a central nervous system lesion and an unresponsive pupil does not necessarily indicate an afferent defect.3


Dynamic retinoscopy indicates that infants from 6 days to 1 month of age have no accommodation, but that normal function is achieved by 3 to 4 months.4 The effect of this is defocus of the higher spatial frequencies, the detection of which requires a greater discrimination than the younger infant is capable of. However, photorefraction studies have demonstrated an ability to accommodate of over 1 diopter in the neonate, and this increases rapidly in the first month and to a lesser extent in the first few years of life, with high amplitudes from 4 years onward until presbyopia sets in.



The near synkinesis


When looking from the distance to a near point, the eyes converge, the pupils constrict, and the lens accommodates; these components are separate in origin but linked as a synkinetic response. Disturbances in the relationship between the amount of accommodation and convergence are important aspects of most childhood squints, and the manipulation of that accommodation to convergence ratio is important in management.


In uncooperative children, testing of the near pupil response is more difficult than the response to light. The most important factor in testing is to provide a suitable fixation target, for example a small internally lit toy for an infant, a mobile toy with sufficient detail to stimulate convergence, and letters or numbers for a literate child.



Congenital and structural abnormalities


Congenital, structural, and developmental anomalies in the pupil include the following (many are found in Chapters 32 and 38):



• Aniridia


• Micropupil (congenital idiopathic microcoria)


• Polycoria and corectopia


• Coloboma


• Peninsula pupil (an inherited partial iris sphincter atrophy with dilated oval pupils)


• Persistent pupillary membrane


• Congenital mydriasis and miosis


• Irregular pupils


• Abnormalities of iris color



Afferent abnormalities of pupil reactivity



Afferent pupil defects



Amaurotic pupils


A totally blind (“amaurotic”) eye resulting from ocular disease usually has no pupil reaction to a light shone on it (amaurotic pupil), but a normal near reaction if the efferent side is intact. In monocular blindness, the affected eye has no direct pupil reaction but has an intact consensual response when the light is shifted to the unaffected eye (amaurotic pupil reaction). In cases of binocular blindness due to anterior visual pathway or retinal disease, both pupils are usually dilated, although they may be nearly normal in size in long-standing blindness. If the efferent pupil pathway is intact, then eyes with an amaurotic pupil will still be able to react to near stimuli (light−near dissociation).



Relative afferent pupil defect


When one afferent pathway is affected, or if bilateral afferent pathways are affected asymmetrically, the relative afferent pupil defect (RAPD) in the afferent pupil pathway can be detected clinically with the “swinging flashlight” test (see video 106.1).5image



Testing for a RAPD


In a dimly lit room, the observer uses a bright light source and shines the light upon each pupil individually. The child should be encouraged to fixate at distance to relax the accommodative pupil response at near. The light is then swung between the two eyes (i.e. “the swinging flashlight test”) with one second on each eye and one second between the eyes. If there is a defect in the afferent pupil pathway of one eye, then the direct response will be less than the consensual reaction driven by the fellow eye and the affected pupil will dilate as the light swings from the unaffected to the affected pupil (i.e. a relative afferent pupillary defect). The RAPD can be graded subjectively from I through IV, with IV being an amaurotic pupil. The magnification provided by a slit-lamp may help detect a minimal defect in an older, more cooperative child. In situations in which there is a known unilateral efferent defect or opacity precluding evaluation of the affected pupil, the test for the RAPD can still be performed. In this setting, a second light is held below the unaffected pupil. As the light swings from the affected pupil to the unaffected pupil, the unaffected pupil constricts and when the light swings back to the affected pupil, the pupil in the unaffected eye will dilate and can be seen better with the second light shining indirectly from below. The RAPD is usually attributed to Robert Marcus Gunn who described sequential pupillary assessment with a bright light: the swinging light test is much more sensitive in detecting mild to moderate afferent defects.


The presence of an RAPD is objective evidence for a defect in the afferent pathway from the retina to the optic tract and the intercalated neurons in the midbrain to the efferent pupil pathway. Although uncommon, a small RAPD may occur in deeply amblyopic eyes.6 In older children, a useful subjective addition to the test for the RAPD is to ask the child which eye sees the light brightest. The child may be asked a question, “if the light in the good eye is worth 1 pound/dollar how much is the other one worth?”, which may give a rough subjective quantification.



Light–near dissociation


When the pupil reacts better to a near than to a light stimulus this is referred to as light–near dissociation. Defects in the afferent or efferent pupillary pathway might produce light−near dissociation. In patients with bilateral, but symmetric, afferent disease, an APD might be difficult or impossible to detect. In these situations, it is especially important to look for light−near dissociation of the pupil which might be evidence of afferent disease thereby aiding in localization of the lesion.



Efferent pupillomotor defects



Argyll Robertson pupils


In 1869, Douglas Argyll Robertson described a type of light−near dissociation seen classically with tertiary syphilis. The pupils are small, irregular, and constrict more fully and more briskly to a near stimulus than to light. The iris is often seen to be atrophic on slit-lamp examination. The lesion in the Argyll Robertson pupil is presumed to be located in the dorsal midbrain,7 and patients with such pupils should undergo serologic testing for syphilis.



Sylvian aqueduct syndrome (Parinaud’s dorsal midbrain syndrome)


Expanding lesions dorsal to the Sylvian aqueduct in children include pinealomas, ependymomas, “trilateral” retinoblastoma, granulomas, hydrocephalus, cystic and and other lesions. Compression of the dorsal midbrain produces light–near dissociation that may be associated with a vertical gaze palsy (typically upgaze palsy), lid retraction (Collier’s sign), accommodation defects, and convergence–retraction nystagmus. The resting size of the pupils is usually larger than normal. Sometimes, probably in more rapidly enlarging tumors, the pupils may be large and poorly reactive to light or near stimuli.



Adie’s syndrome (tonic pupil syndrome)


Adie’s syndrome, unusual in young children, is typically idiopathic, but may occur with chicken pox or other viral infections,8 ophthalmoplegic migraine, and measles vaccination.9,10 It is more frequent in young female adults.11 It is usually unilateral but many cases become bilateral.11 Children rarely have symptoms related to the onset, but they may fail a school near vision test, or complain of blurred near or, if they are hyperopic, distant vision or photophobia. They may develop anisometropic amblyopia. Many patients are asymptomatic and parents may be the first to notice.


The acutely affected pupil is usually larger than the uninvolved eye (Fig. 63.2), but over time the Adie’s pupil tends to become miotic (“little old Adie”). There is typically a segmental paralysis of the iris sphincter which might be more extensive or diffuse. Once constricted, the pupil remains consticted longer (the “tonic” pupil). There may also be a transient defect in accommodation, which is often marked at first but gradually improves over 2 or more years.11 Corneal sensation may be reduced when tested with an aesthesiometer or even with a wisp of cotton, but is generally asymptomatic. This is probably due to damage to the trigeminal fibers that also pass through the ciliary ganglion. Patients with Adie’s pupil may also have hyporeflexia or areflexia in their extremities but no other neurologic findings are usually present. Although the Adie’s pupil is a clinical diagnosis, denervation hypersensitivity of the pupil may be demonstrated by finding pupillary constriction compared to the fellow eye 20 minutes after instillation of pilocarpine 0.0625%. Pharmacological hypersensitivity may occur with post- as well as pre-ciliary ganglionic lesions (Fig. 63.3).


image image

Fig. 63.2 Left Adie’s pupil. (A) In light, (B) in dark. The pupil size difference is less in the dark.


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Fig. 63.3 Left Adie’s pupil (A) before and (B) after instillation of 0.1% pilocarpine. The right pupil is unchanged while the left constricts due to denervation hypersensitivity.


Loewenfeld and Thompson proposed that the site of the lesion of the tonic pupil is in the ciliary ganglion and that many of its features can be explained by aberrant regeneration.12 The cause is unknown but it may be due to a neurotropic virus. Most patients do not require treatment, but they may be helped with their photophobia and occasionally with symptoms due to accommodation paresis by pilocarpine (0.1% three times daily) or another dilute miotic. In distinction to adult patients, young children with Adie’s or other tonic pupils should have the unaffected or better eye occluded for a short period each day to avoid amblyopia. Spectacle correction of hyperopia in the affected eye may be necessary to prevent anisometropic amblyopia.



Other causes of tonic pupils


Although Adie’s syndrome is the classic idiopathic tonic pupil, other causes of ciliary ganglion damage give rise to a similar syndrome. Congenital or acquired tonic pupils have been described in infants with orbital tumors, traumatic, infectious, or inflammatory diseases or as part of a variety of widespread neuropathies including syphilis, diabetes, Guillain-Barré syndrome, Miller-Fisher syndrome, pandysautonomia, hereditary sensory neuropathy, Charcot-Marie-Tooth disease, and Trilene poisoning. Autonomic neuropathy due to paraneoplastic disease has also caused tonic pupils.



Iris abnormalities


Damage to the iris by trauma, irradiation, uveitis, ischemia or hemorrhage, or involvement with a tumor such as lymphoma, leukemia, juvenile xanthogranuloma, leiomyoma, or neurofibroma, may all give rise to anisocoria, corectopia, and/or impaired pupil reactions (Fig. 63.4). Slit-lamp examination of the iris can demonstrate the disruption of the iris architecture from the underlying cause.


image

Fig. 63.4 Normal right eye (A) and left iris abnormality with sluggish reactions and small pupil due to leukemic infiltration (B).



Benign episodic unilateral mydriasis (“springing pupil”)


The syndrome of idiopathic episodic mydriasis is likely a heterogeneous group of conditions that result in parasympathetic insufficiency of the iris sphincter or sympathetic hyperactivity of the iris dilator.13

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Jun 4, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on Pupil anomalies and reactions

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