The document discusses the physiology and clinical applications of the pupil. It describes the pupil's functions in controlling retinal illumination, reducing optical aberrations, and providing depth of focus. It then discusses various clinical aspects of pupil examination including relative afferent pupillary defect, anisocoria, pupil pathways, near response, and pharmacological response. Various conditions that affect the pupil like Horner's syndrome and Adie's tonic pupil are also summarized.

1. The Pupil : Physiology
and Clinical
Applications
Raed Behbehani , MD FRCSC

2. Functions
• Control of retinal Illumination.
• Reduces optical aberrations.
• Depth of focus by miosis (pinhole effect).

3. Functions
• In dim light, pupil dilates maximizes the
number of photons to enhance dark
adaptation.
• In light adaptation , pupil constricts and
enhances light adaptation.

4. Functions
• A small pupil reduces spherical and
chromatic aberration.
• After Refractive surgery, patient with large
pupil have more bothersome symptoms
( glare at night).

5. Clinical Significance of
Pupil Status
• Measure afferent input. (RAPD)
• Indicates awakefulness.
• Autonomic functions.
• Pupil diameter and optical aberrations.
• Pharmacological response.

6. Pupil Examination

7. Relative Afferent
Pupillay Defect
• Swinging flashlight test.

8. RAPD

9. Awakefullness
• Excited individualas - larger pupil.
• Sleept , on narcotivs - smaller pupil.
• Central inhibition (parasympathomimetic)
at level of midbrain.

10. Anisocoria
• Inequality of pupils sizes.
• Drugs.
• Trauma.
• Sympathetic lesions (Horner’s).
• Parasympathetis lesions (Adie’s ,Third
nerve Palsy).

11. Pupil Pathway

12. Near Response
• Activation of rostral brain stem neurons
(supranuclaear input) which relay to
Edinger-Westphal to activate near
response.
• Light-Near dissociation.

13. Afferent Arm Of
Pupillary Light Reflex
• Same as visual perception (Rods and
Cones).
• Under dark adaptation , rods
dominates( low-amplitude contractions ).
• Under light adaptation, cones dominate
( larger amplitude contractions ).

14. Melanopsin-containing
Retinal Ganglion Cells
• MCRGC recently discovered and fire
constantly to produce steady-state
contractions.
• May mediate light input to the pupil via
rods and cones.
• Project to suprachiasmatic nucleus
(hypothalamus - circadian rythm) and
pretectal nucleus (midbrain).

15. Interneurons Arm of
Pupillary Reflex
• Pretectal Neurons : Summate GC input.
• They send (corssed and uncrossed fibers)
in PC to EW nucleus (equally).
• Dorsal Mibrain Syndrome (Light-near
dissociation).

16. Pupil Pathway -
Pretectal Neurons
• Birds and rabits have only crossed fibers in
pretectal nucleus ( only ipsilateral eye will
respond to light) .
• Cats - 70% crossed.
• Humans - almost 50% crossed and
uncrossed.

17. Efferent Arm of
Pupillary Response
• EW nucleus send fibers to III CN and
Preganglionic accomodative Neurons in
nearby nuclei.

18. CN III
• CN III send fibers --- ciliary ganglion
(parasympathetic) -- Short Ciliary Nerve.
• Post-Ganlionic accomodative fibers :
Pupillary fibers = 30 : 1.
• Sectoral distribution on the iris (20 clock
hours)
• Adies’s tonic pupil , L-N dissociation.

19. CN III Palsy

20. Accomodation
• Convergence , accomodation , and miosis.
• Mechanism synchronized by supra-nuclear
connections.
• Cortical areas around visual cortex and
frontal eye field.

21. Pupil Dilataion
• Iris sphincter relaxes and iris dilator
muscles contracts.
• Supranuclear inhibition of EW nucleus by
sympathetic class of neurons pass through
the Periaqueductal gray area -> relaxation
of iris sphincter.
• Narcotics, and sleep produce miosis.

22. Oculosympathetic Flow

23. Oculosympathetic
Pathway

24. Relative Afferent
Pupillary Defect
• RAPD correlates with amount of visual
field deficit.
• Neutral density filter can measure
objectively.
• If pupil does not work , look at the OTHER
pupil.

25. Measuring RAPD

26. Anisocoria
• Is it worse in LIGHT (iris sphincter) or
DARK (iris dilator) damage ?

27. Anisocoria

28. Anisocoria Increases in
Dark
• Horner’s Syndrome.
• Simple Anisocoria.

29. Horner’s Syndrome
• Dilation Lag (pupil dilates slowly in dark
room).
• Usually anisocria greatest first 4-5 seconds
after light it turned off.
• Ptosis ,“up-side down ptosis”, conjunctival
injection , ipsilateral decreased sweating.

30. Horner’s Syndrome

31. Horner’s Syndrome
Right Horner’s Syndrome before and after Cocaine test

32. Horner’s Syndrome

33. Diagnosis of Horner’s
• Cocaine (prevents reuptake of
Norepinephrine) , 4% or 10%.
• After application by 40-60 minutes , check
pupils.
• Presence of >=1 mm aniosorocia after
cocoaine is positive test.

34. Dilation Lag

35. Diagnosis of Horner’s
• Hydroxyamphetamine (differentiates pre-
from post-ganglionic lesions).
• Apraclonidine (reversal of anisocoria ,
alpha-1 supersensitivity)

36. Diagnosis ?

37. Adie’s Tonic Pupil
• Women.
• Segmental denervation (sectoral palsy).
• Light-near dissocation (chronic stage).
• ? Immune-mediated damagae to ciliary
ganglion.
• 50% bilateral in 10 years.

38. Adies’ Tonic Pupil

39. Adies Tonic Pupil

40. Cholinergic
Supersensitivity
• 0.125% Pilocarpine produces more
constriction in the abnormal pupil.
• Develops in 5-7 days.
• Can occur in CN III palsy as well.

41. Anticholinergic
Mydriasis
• 1% Pilocarpine can be used to diagnose.
• Scopolamine , cyclopentolate , atropine.

42. CN III Palsy
• Pupillary fibers located in medial part of the
intracranial CN III.
• Aberrant regeneration (Primary and
Secondary)

43. CN III Palsy Aberrant
Regeneration

44. Aberrant Regeneration
CN III

45. Tadpole Pupil
• Brief episodic pupillary “distortion” or
peaking.
• Lasts 3-15 minutes.
• Abnormal periocular sensation, headache,
blurred vision.
• No specific treatment needed.

46. Tadpole Pupil

47. Tadpole Pupil

48. idiopathic episodic unilateral
mydriasis
• Benign episodic mydriasis.
• Can lasts from hours to weeks.
• Can be associated with migraine.
• No apparent precipitating factor.
• Sympathetic overaction or parasympathetic
underaction.