for beginners ophthalmologists

1. Pupillary Reflexes
Othman Al-Abbadi, M.D

2. Normal pupil
• Functions:
• Limits the amount of light reaching retina
• Controls spherical & chromatic aberrations
• Number
• Location
• Size  3-4 (bright)… 4-8 (dark)
• The same for different genders & iris colours
• Variation with age
• Physiologic anisocoria

3. • Pupillary unrest: constant symmetrical fluctuation… detected
by magnification
• Hippus: exaggerated.. Detected on visual inspection
• No diagnostic significance
• Colour: depend on the structures behind it
• Greyish black
• Jet black
• leukocoria

4. • Pupillary constrictor/ spincter-innervated by parasympathetic
• Pupillary dilator – innervated by sympathetic
• Evaluation of pupil- Diagnostic clue to ocular, neurological,
medical, surgical and paediatric diseases

5. Light reflex
• When light is shown to one eye.. Both pupils constrict
• Direct vs consensual
• Almost identical in time, course & magnitude
• If both pupils illuminated at once summation
• Dependant the state of adaptation of the retina, emotions,
alertness, …
• Maximum frequency of stimuli is 5 Hz

6. Light reflex
• Initiated by retinal photoreceptors
• Transmitted along optic nerve
• Undergo a hemidecussation at the optic chiasma
(nasal fibres cross over)
• Proceeds along optic tract
• Synapses at pre- tectal nucleus
• Ends in both Edinger westpal nucleui
• Any given pretectal neuron behaves functionally
as though it recieves similar inputs from each eye
& projects equally in each EW nucleus
• Ipsilateral around periaqueduct
• Contralateral via the posterior commissure

7. Light Reflex

8. • Efferent fibers travel on the surface of CN-III
• to inf. Obl.
• &/ due to long course unilateral defecits can be of
localizing significance in unilateral pathology
• Synapse & relay at ciliary ganglion
• Post ganglionic fibres reach ciliary muscle and
iris spincter through short ciliary nerves to reach
the sphincter pupillae
• Cerebral cortex sends inhibitory signals to EW
nucleus absence leads to meiosis during sleep

9. • Functions:
• Protects against excessive bleaching of the visual pigments
• Light/Dark adaptation to maximize VA

10. Near reflex
• Triad:
• Inc. accomodation
• Convergence of visual axes
• Constriction of the pupils

11. Near reflex
• Accomodation reflex:
• Stimulus : Blurring of retinal images when object is near
• Retina- Optic nerve – Optic chiasma- Optic tract- Optic
radiations- Lat geniculate body- visual cortex – cortical
association areas- occipito mesencephalic tract- mid brain-
E.W. nucleus- 3rd nerve- accessory ciliary ganglion along short
ciliary nerves- ciliary muscle and pupil constrictor

12. Near reflex- convergence
reflex
• Co contraction of both medial recti
• Proprioceptive impulses originate and travel along 5th
nerve
• Reach mesencephalic root of 5th
nerve
• Transmitted to EW nucleus in midbrain via convergence
centre (in the tectal or pretectal area)
• From EW efferent pathway same as accomodation reflex

13. Accomodation Reflex

14. Darkness reflex
• From lighted to dim environment
• Physiology
• Abolition of light reflex relaxation of sphincter pupillae
• Contraction dilator pupillae

15. Psychosensory reflexes
• Dilation in response to psychological stimuli
• Not seen in newborn
• Fully developed at 6 months of age
• Cortical mechanism

16. Ciliospinal reflex
• Pupil dilation in response to painful stimulus in the neck
• Indicates that some of the psychosensory reflex is mediated at
the spinal cord

17. Lid-closure reflex
• Nonspecific term
1.Meiosis with blinking
• Constrict transiently with blinking
• Absent in darkness maybe darkness reflex
1.Homolateral meiosis with lid closure
• Constrict with forced prohibited lid closure
• Absent if distant gaze unconscious attempt at near
gaze
1.Oculopupillary reflex (mydriasis on corneal
touch)

18. Pharmacology
• Miotics
• Mydriatics

19. Parasympathomimetics
• Cholinergic
• Initiate or potentiate acetylcholine action
1.Direct acting
• Pilocarpine; similar to acetylcholine
1.Indirect (cholinesterase inhibitors)
• Cholinesterase is present in presynaptic axon
• Block action or deplete stores
1. Reversible physostigmine
2. Irreversible ecothiophate iodide, demecarium,
diisopropyl fluorophosphate
2.Dual action

20. Sympatholytics
• Alpha-adrenergic blockers
• By preventing dilator contraction by occupying alpha-receptor
sites on the iris dilator
• E.g: thymoxamine, phenoxybenzamine, dibenamine,
tolazoline
• Guane-thidine
• commonly used in ophthalmology
• Depletes norepinephrine stores & disrupts release
• Continued topical drops lead to Horner’s syndrome

21. Other miotics
• Histamine:
• Direct action
• Even in atropinized eyes
• Morphine
• Cutting off cortical inhibition of EW nucleus
• Also direct action

22. Sympathomimetics
• Ways of action:
• Inc. norepinephrine release
• Prevent reuptake
• Direct action
1.Adrenaline (epinephrine)
• Direct action
• 4 drops of 0.1% q5m
• Rapidly inactivated (not effective)

23. 2. Phenylephrine 5-10%
• Synthetic analog
• Direct action & inc. release
2. Hydroxyamphetamine & ephidrine
• Inc. release
2. Cocaine
• Prevents reuptake

24. Parasympatholytics
1. Atropine 1%
• Strongest
• Completely paralyses sphincter pupillae & ciliary muscles
• Complete dilation in 30-40 m & cycloplegia in 2h
• Duration 7+ d
1. Homatropine 2%
• Quicker
• Cycloplegia in 45-60 m
• Duration 48 h

25. 3. Cyclopentolate 1%
• Short acting
• Cycloplegia 1 h
• Duration 6-12 h
3. Tropicamide 1%
• noncycloplegic

26. Abnormalities of
pupillary reflexes

27. Afferent pathway defects
1. TAPD (amaurotic pupil)
• Complete retinal or nerve lesion
• Total blindness
• -ve ipsilateral direct & contralateral consensual light reflex
• Isocoria in diffuse illumination
• Near reflex is preserved

28. 2. RAPD (marcus gunn pupil)
• Severe retinal or incomplete optic nerve lesion
• Swinging flashlight test
• Paradoxical response of the affected pupil by Swinging flashlight
test
• Earliest sign of optic nerve disease
• VA maybe preserved

29. • 3. Wernicke’s hemianopic pupil
• Optic tract lesion
• Ipsilateral temporal & contralateral nasal

30. Efferent pathway defects
• Ipsilateral absence direct & consensual light
reflexes
• Ipsilateral absence of near reflex
• Ipsilateral fixed & dilated pupil
• Causes
• Brainstem lesions
• Fascicular 3rd
nerve lesion
• Ciliary ganglion lesion
• Iris damage
• Drugs
• Pilocarpine to differentiate from neuro

31. Tonic pupil
• -ve light, accomodation & near reflexes
• Cholinergic hypersensitivity (pilo 0.125%)
• Causes
• Local
• Herpes zoster ganglionitis
• Orbital or choroidal trauma or tumors
• Blunt trauma resulting injury at the iris root
• Neuropathic (DM, alcoholism)
• Adie’s tonic pupil

32. • Adie’s tonic pupil: Characterised by
• large unilaterally dilated pupil
• Absent / poor light response
• In near response , there is slow / tonic contraction of the iris
• May be associated with loss of deep tendon reflexes as for the
knee (Adie’s syndrome)
• Seen in young women
• Mild regional corneal impaired sensitivity

33. Light-Near dissociation
1. Bilateral complete afferent pathway defect
2. Lesion in the midbrain at the level of the
pretectal area
3. CN-III palsy with regeneration of MR
innervation into sphincter innervation pathway
(pseudo-Argyll Robertson pupil)
4. Ciliary ganglion or short ciliary nerve with
regeneration of accomodation fibers into
sphincter pupillae
5. Aberrant regeneration in DM, alcoholism,
amyloidosis

34. • Argyll Robertson pupil(ARP)
• Occurs in neurosyphilis, Tabesdorsalis,G.P.I.
• Site of lesion: (dorsal mid brain) in the region of the tectum near the
sylvian aqueduct interfering with light reflex fibers & supranuclear
inhibitory fibers going down to EW nucleus
• Characteristics:
• Bilateral asymmetrical involvement
• Small irregular pupils
• Preserved vision
• -ve light & +ve near reflexes
• Poor dilation with atropine
• Further constriction with physostigmine

35. • Horner’s syndrome :
• Involvement of cervical sympathetic
• Miosis, partial ptosis, enophthalmos & anhydrosis
• Iris heterochromia

36. • Pourfour de Petit Syndrome
• This syndrome is the clinical opposite of Horner syndrome. It
represents oculosympathetic overactivity
• unilateral mydriasis, lid retraction, apparent exophthalmos, and
conjunctival blanching
• Seen after trauma, brachial plexus anesthetic block or other
injury, and parotidectomy