Clinical Testing: PupilsDr.Roopchand.PSSenior Resident AcademicDepartment of Neurology
Introduction:• The normal pupil size in adults varies from 2to 4 mm in diameter in bright light to 4 to 8mm in the dark.• They constrict to direct illumination (directresponse) and to illumination of the oppositeeye (consensual response).• The pupil dilates in the dark.• Both pupils constrict when the eye is focusedon a near object (accommodative response)
• The size of the pupil is controlled by– the circumferential sphincter muscle found in themargin of the iris• innervated by the parasympathetic nervous system– iris dilator muscle, running radially from the irisroot to the peripheral border of the sphincter.• iris dilator fibers contain α-adrenergic sympatheticreceptors• Function : control the amount of light enteringeyes for optimal vision.• Hippus: constant small amplitude fluctuationof pupil under constant illumination.
Pupillary Reflexes:• Light Reflex– Constriction of pupils in response to light.• Accomodation Refelx
The Light Reflex:• Tested in each eye individually• Patient fixing at a distance• Light shown to the eye obliquely.• Cover uncover thechique– Uses ambient light• Normal response: brisk constriction -> slightdilatation back to an intermediate state.
• Can be recorded : prompt, sluggish, absent– Graded 0 to 4+• THE ACCOMMODATION REFLEX:– Relax accommodation by gazing a distant object– Shifting gaze to some near object.– The primary stimulus for accommodation isblurring.– Response: accommodation, convergence, miosis
Other reflexes:• Ciliospinal reflex: dilation of pupil on pain fulstimulation of ipsilateral neck.• Occulosensory or occulopupillary reflex:constriction or dilation followed byconstriction on painful stimuli to eye or itsadnexa.• Plitz – Westphal reaction.• Cochleo pupillary reflex & vestibulopupillaryreflex.• Psychic reflex.
Large pupils:• 3rd nerve palsy.– With pupil sparing– With predominant pupil involvement.– Mid dilated unreactive pupil.• Adie’s pupil.– Slow response to light and removal of illumination– Lesion at ciliary ganglion/ short ciliary nerves– Denervation supersensitivity.– Old adie’s pupil: unilateral miosis.
• Tectal pupils: large pupils with light neardissociation.– seen in lesions affecting the upper midbrain.• The variably dilated, fixed pupils reflectingmidbrain dysfunction in a comatose patientcarry a bleak prognosis.• Acute angle closure glaucoma: dilated poorlyreacting pupils– Cloudy cornea.
Small Pupils:• Pilocarpine eye drops, opiate• Horners syndrome.• Neurosyphilis.
Horners syndrome:• Ptosis– Denervation of mullers muscles• Miosis– Denervation of dilators• Anhydrosis– Sympathetic denervation• Apparent enophthalmosis– Narrowing of palpebral fissure• Absent ciliospinal reflex.
Argyll Robertson Pupil:• Small irregular pupil having light near.dissociation.• React poorly to light.• Normal near response.• Neurosyphilis.• Lesion in periaqueductal region, pre tectal,rostral midbrain
Abnormal Reaction:• Disease of the retina does not affect pupilreactivity.• Cataracts and other diseases of the anteriorsegment do not impair light transmission.• Because of the extensive side-to-side crossingof pupillary control axons through theposterior commissure, light constricts not onlythe pupil stimulated (the direct response) butalso its fellow (the consensual response).
Afferent Pupillary Defect:• The status of the light reflex must be judgedby comparing the two eyes.• Indicator of optic nerve function• Swinging flashlight test: light is held about 1 infrom the eye and just below the visual axis;the light is rapidly alternated.– The examiner attends only to the stimulated eye.– Comparing the amplitude and velocity of theinitial constriction in the two eyes
• The reaction is relatively weaker when the badeye is illuminated.• The brain detects a relative diminution in lightintensity and the pupil may dilate a bit inresponse.• Bring out the dynamic anisocoria.• The weaker direct response or the paradoxicaldilation of the light-stimulated pupil is termedan afferent pupillary defect (APD), or MarcusGunn pupil
Grading of an Afferent PupillaryDefect:• Trace APD: pupil that has an initialconstriction, but then it escapes to a largerintermediate position than in the other eye.• 1 to 2+ APD: no change in pupil size initially,then dilation.• 3 to 4+ APD: immediate dilation of theaffected pupil.• Placing neutral density filters over the goodeye
• Paradoxical pupils: constrict in darkness– congenital retinal and optic nerve disorders.• Springing pupil: intermittent, sometimes alternating,dilation of one pupil lasting minutes to hours seen inyoung, healthy women, often followed by headache.• Tadpole pupil: pupil intermittently and brieflybecomes comma-shaped because of spasm involvingone sector of the pupillodilator• Scalloped pupils: occur in familial amyloidosis• Corectopia iridis: spontaneous, cyclic displacement ofthe pupil from the center of the iris.– seen in severe midbrain disease.