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pupil. The pupil is an opening located in the center of the iris that allows light to enter the retina. Its function is to control the amount of light entering the eye and it does this via contraction (miosis) and dilation (mydriasis) under the influence of the autonomic nervous system.

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slide2
The pupil is an opening located in the center of the iris that allows light to enter the retina.
  • Its function is to control the amount of light entering the eye and it does this via contraction (miosis) and dilation (mydriasis) under the influence of the autonomic nervous system
slide3
The iris is a contractile structure, consisting mainly of smooth muscle, surrounding the pupil. Light enters the eye through the pupil, and the iris regulates the amount of light by controlling the size of the pupil.
slide4
The iris contains two groups of smooth muscles:
  • a circular group called the sphincter pupillae.
  • and a radial group called the dilator pupillae.
parasympathetic pathway
Parasympathetic pathway
  • First Order – Retina to Pretectal Nucleus in B/S

(at level of Superior colliculus)

  • Second Order – Pretectal nucleus to E/W nucleus

(bilateral innervation!)

  • Third Order – E/W nucleus to Ciliary Ganglion
  • Fourth Order – Ciliary Ganglion to Sphincter

pupillae (via short ciliary nerves)

sympathetic pathway
Sympathetic Pathway
  • First Order – Posterior Hypothalamus to

Ciliospinal centre of Budge (C8-T2)

(Uncrossed in Brainstem)

  • Second Order – Ciliospinal centre of Budge to

Superior Cervical Ganaglion

  • Third Order – Superior Cervical Ganglion to

dilator pupillae muscle. (Close to

ICA and joins V1 intracranially)

slide8

You can then observe the pupils closely by shining a bright light on the patient's face from below (minimise the shadow cast by the nose by placing the light in the midline). If you think there is size asymmetry, a good trick is to stand back and observe the red reflex of both eyes simultaneously with the ophthalmoscope. A slight difference will then become more apparent.

pupils
Pupils
  • Pupil is the circular aperture in the centre of iris. Its normal size is 3-4mm. it is grayish black in colour.
points to be noted in pupil
Points to be noted in pupil

1. Number-normally there is one pupil. More than one pupil is called polycoria.

2. Location- normally almost central, slightly nasal. Eccentric pupil is called correctopia.

3. Size of pupils

slide11
Normal pupil

may be variable sizes but should be equal

– react to light

– central

– round

  • Abnormal

– unequal

– dilated or constricted

– not reacting to light

– irregular (eg tear drop)

– not central

assessing pupillary reflexes
Assessing pupillary reflexes
  • There are essentially three reflexes to specifically test for :
  • Light-reflex test
  • Swinging flashlight test
  • Near-reflex test
pupillary reactions
Pupillary reactions
  • Pupillary Reflexes
  • Light reflex-
  • Direct- throw light into the eye, look for pupillary constriction in the same eye
  • Consensual - keep an obstruction between the two eyes. Throw light in one eye, look for constriction in other eye.
slide14
Light-reflex test
  • What it assesses - the integrity of the pupillary light reflex pathway.
  • How to perform it - dim the ambient light and ask the patient to fixate a distant target. Shine the right eye from the right side and the left from the left side. (Make sure you do not stand in front of the patient as their pupils will accommodate to focus on you). Record whether there is a direct pupillary response (the pupil constricts when the light is shone on it) and a consensual response (the fellow pupil constricts too).
  • Normal test - there should be a brisk, simultaneous, equal response of both pupils in response to light shone in one or the other eye.
slide15
Swinging flashlight test
  • What it assesses - compares direct and consensual responses of each eye (as opposed to seeing whether they are there or not).
  • How to perform it - use the same conditions as for the light reflex test and check this reflex first. Then, move the beam swiftly and rhythmically from one eye to the other, making sure that you allow the same amount of light exposure on each eye and that each is illuminated from the same angle. You should note the pupillary constriction of both eyes when the beam is maintained. However, when it is swung, look at what happens to the pupil of the eye you are concerned about and compare this with what is happening to the fellow eye.
slide16
Normal test - the pupil should constrict or stay the same size.
  • If it dilates when light is shone on it, then this means that the light reflex is weaker than the consensual reflex (produced by withdrawing light from the unaffected eye), suggesting optic nerve pathology. This abnormal response is known as a relative afferent pupillary defect (RAPD) and is a very important sign. Note that this is a comparative test: you cannot have a bilateral RAPD.
pupillary reactions18
Pupillary reactions
  • Near reflex- pupil contracts while looking at near object. It has 2 parts –

a) convergence reflex i.e. contraction of pupil on convergence

b) accommodation reflex i.e. contraction on accommodation

slide19
Near-reflex test
  • What it assesses - this assesses the miosis component of near fixation. (The other two components are accommodation: increased lens thickness and curvature, and convergence of the eyes).
  • How to perform it - in a normally lit room, instruct the patient to look at a distant target. Bring an object (toy, patient's thumb) into their near point (about an arm's length away) and observe the pupillary reflex when their fixation shifts to the near target.
  • Normal test - there should be a brisk constriction. A near-light dissociation describes the situation where the patient has a significantly better pupillary near reflex than light reflex.
slide21
Anisocoria
  • This refers to unequal pupils. This is physiological in about 20% of people. However, if this is a new complaint, the steps to the underlying diagnosis lie in determining which of the pupils is abnormal and then look for associated signs. The first step is to compare the pupils in light and dim conditions:
  • If there is a poor reaction to light in one eye and the anisocoria is more evident in a well lit room, then the affected pupil is abnormally large.
  • If there is a good reaction to light in both eyes but a poor dilation in the dark (i.e. the anisocoria is enhanced), then the affected pupil is abnormally small.
slide22
The abnormally large pupil
  • Features - there is poor constriction in a well lit room.
  • Differential diagnosis - traumatic iris damage, third cranial nerve palsy, pharmacological dilation (i.e. dilating drops), Adie's pupil, iris rubeosis.
slide23
The abnormally small pupil
  • Features - there is poor dilation in a dim room.
  • Differential diagnosis - physiologically small pupil, pilocarpine drops, uvietis with synaechiae, Horner's syndrome.
pupil25
Constricted (mioisis)

Sympathetic (pupillodilator) denervation

Drugs

Pilocarpine

Morphine

Dilated (mydriasis)

Parasympathetic (pupilloconstrictor) denervation

Lesion of the third CN

Drugs

Atropine

Cocaine

Pupil
shape of pupil
Shape of pupil
  • Shape normally circular
  • Irregular narrow pupil- iridocyclitis
  • Festooned pupil- irregular pupil after patchy dilatation (effect of mydriatics in presence of posterior synechiae)
slide27
The abnormally shaped pupil
  • Features - a pupil should be round. Deviation from this suggests abnormalities.
  • Differential diagnosis - congenital defects (e.g. coloboma), iris inflammation or trauma, Argyll Robertson pupils. A fixed oval pupil in association with severe pain, a red eye, a cloudy cornea and systemic malaise suggests acute angle closure glaucoma which warrants immediate referral.
slide29
The abnormally reacting pupil
  • Light reflex test - abnormalities arise as a result of severe optic nerve damage (e.g. transection) - the patient will be blind in that eye, neither pupil reacts when the affected side is stimulated but both pupils react normally when the fellow eye is stimulated.
  • Swinging flashlight test - when the pupil exhibits an RAPD, it is described as a Marcus Gunn pupil. It suggests optic nerve disease, central retinal artery or vein occlusions ,extensive retinal lesion . A mild RAPD may also occur in amblyopia, with vit. hg, RD or advanced macular degeneration.
slide30
Near-reflex test - there are several causes of light-near dissociation which can be grouped according to whether the problem is unilateral or bilateral:
  • Unilateral light-near dissociation - afferent conduction defect, Adie pupil, herpes zoster ophthalmicus, aberrant regeneration of the third cranial nerve.
  • Bilateral - neurosyphilis, diabetes, myotonic dystrophy, Parinaud dorsal midbrain syndrome, encephalitis, chronic alcoholism.
slide32
Congenital abnormalities
  • Aniridia - this is a bilateral condition arising from the abnormal neuroectodermal development secondary to genetic mutation. It is associated with glaucoma and a number of serious, systemic abnormalities.
  • Coloboma:this is an uncommon, congenital condition characterised by a unilateral or bilateral partial iris defect.
  • Leucocoriarefers to a white pupil and may be due to a number of conditions. Congenital cataracts are generally easily identified but all patients must be assessed for the possibility of retinoblastoma.Other conditions causing a white pupil include persistent fetal vasculature syndrome, Coat's disease andROP.
slide33
Acquired structural abnormalities
  • Pseudoexfoliation syndrome - this is a condition characterised by deposition of a grey-white fibrogranular extracellular matrix material deposited on the anterior lens. It is seen, on slit-lamp examination, as a fine grey dusting around the pupil. Pupil shape and function are not affected - it is clinically significant due to its association with glaucoma and its potential to make CATARCT surgery more tricky.
  • Sphincter tear - iris tear can occur as a result of blunt or penetrating trauma and can also occur during intraocular surgery. Tears may be associated with glaucoma and, if large, visual problems. All tears, however small, need ophthalmological assessment.
  • Synechiae - this refers to adhesions between the lens and the iris (posterior synechiae) or the iris and the peripheral cornea (peripheral anterior synechiae). These adhesions will give rise to an abnormally shaped pupil; treatment depends on the underlying cause. Uveitic posterior synechiae are broken with mydriatics whereas glaucomatous anterior synechiae may be managed with miotics.
slide35
Horner’s syndrome - this syndrome is characterised by miosis with a pupil that is slow to dilate, a mild (1-2mm) ptosis, ipsilateral anhydrosis and apparent enophthalmos (affected eye appears to be sunken) as a result of a combination of the ptosis and a slight elevation of the inferior eyelid. The irides may be of different colours if the lesion is congenital or long-standing.Depending on the location of the lesion, some or all of these features will be present.
horner s
Horner’s
  • Oculosympathetic paresis
    • Ptosis: mild (1-2mm)
    • Miosis
    • Ipsilateral anhidrosis
    • Does not dilate with cocaine 4%
causes of horner s pupil
Causes of Horner’s pupil
  • Central – B/S lesions (tumours, vascular and MS)
  • Preganglionic – Pancoast tumour, Carotid & Aortic

aneurysms, Neck lesions/trauma.

  • Postganglionic – Cluster headaches, Nasopharyngeal

tumours, Otitis media, Cavernous

sinus mass and ICA disease.

  • Miscellaneous – Congenital (brachial plexus injury)

Idiopathic.

slide38
Confirmation of Horner's syndrome is with instillation of a drop of 4% cocaine:
  • in physiological anisocoria, this results in dilation whereas it doesn't where there is a Horner's syndrome.
slide39
Further localisation of the problem is carried out with 1% hydroxyamphetamine (Paredrine).
  • Instillation is done >48 hours after the cocaine test as cocaine affects the Paredrine. Pupillary dilation suggests a central or preganglionic Horner's syndrome whereas if dilation does not occur, the lesion is likely to be postganglionic.
slide40
)Adie's) tonic pupil

this describes a unilateral (80% of cases) mydriaticpupil in otherwise healthy patients (typically young adults, especially women). Over months to years, the pupil diminishes in size to eventually become miotic. There is a sluggish, sectoral or no reaction to light but a normal near reflex. Redilation after the near-response is slow. Slit-lamp examination may reveal slow, vermiform contractions of the iris but ultimately

slide41
the diagnosis is confirmed by the pupil's hypersensitivity to weak miotic drops (e.g. 0.05-0.125% pilocarpine) which causes the abnormal pupil to contract vigorously and the normal pupil minimally.
  • Occasionally, it is associated with diminished deep tendon reflexes (Holmes-Adie syndrome) ± autonomic nerve dysfunction.
slide42
The exact cause is not known but it often occurs after a viral illness (e.g. herpes zoster ophthalmicusand denervation of the postganglionic supply to the sphincter pupillae is described. This tends to be a benign condition and the patient is simply observed. However, infants < 1 year old should be referred to a paediatric neurologist to rule out familialdystonias(Riley Day syndrome(
slide43
Argyll Robertson pupil -these are caused by neurosyphilis. Although usually asymptomatic, they have characteristic features on examination. These include a bilateral (usually asymmetrical) small, irregular pupils showing a light-near dissociation. They are difficult to dilate. Management is related to the underlying disease.
comparison
Argyll-Robertson pupil

Small, irreg

Does not react to light

Reacts to accommodation

Causes

syphilis

diabetes

Miotonic pupil (Adie’s syndrome)

Dilated

Poor response to light and convergence.

Constricts with weak Pilocarpine

Holmes-Adie syndrome

Reduced tendon reflexes (Knee, ankle)

- Orthostatic hypotension

comparison
slide46
Topical drugs
  • Dilating - sympathomemtice.g. phenylephrine, adrenalinediperavine and antimuscarinics e.g. cyclopentolate, tropicamide , atropine.
  • Constricting - muscarinic agonists e.g. pilocarpine.
slide47
Systemic drugs
  • Dilating - sympathomimetics e.g. adrenaline and antimuscarinics e.g. atropine. Think also of tricyclic antidepressants, amphetamines .
  • Constricting - opiates e.g morphineandorganophosphate..