Abnormal Pupil Reactions

Hatlan Alhatlan

211525898

Pupil ?

Function of The Pupil

• The pupil serves an important function to the eye , as it controls the amount of the light that enters the eye , and it does so by the help of the Iris:

• Sphincter muscle(constrictor) Dilator muscle

(Circular) (Radial)

Physiology of The Pupil

• Knowing the physiology is must :

• The parasympathetic pathway :controls the constrictor pupillaemuscle , serves as the pupillary light reflux :

• Also as near , orbicularisand trigeminal

The Pupillary light reflux pathway :

Afferent pathway -

1-optic disc/nerve

2- optic chiasm

3- optic tract

4-the pretectal nucleus (lying in the dorsal midbrain).

Efferent pathway: (The parasympathetic)

1- Edinger-Westphal nucleus

2- the third cranial nerve out to

3-the ciliary ganglion

4-short ciliary nerves to both constrictors of the eye.

The Sympathetic Pathway

• The sympathetic pathway controls the dilator papillae muscle :

• For withdrawal , emotional fear and vestibular reflex.

The pathway of The Sympathetic

• -The central first neuron begins in the posterior hypothalamus, the ciliospinal center (C8-T2)in the cervical spinal cord

• -The preganglionic second neuron

• Through sympathetic trunk to the superior cervical ganglion.

• -The postganglionic third neuron extends a neural plexus along the internal carotid artery, ophthalmic artery, and long ciliary nerves to the dilator pupillae muscle .

Let’s Start to evaluate the Pupil

• General examination of the patient

• Provide helpful clues as to what is going on, particularly where there is an underlying neurological cause.

• Telltale neck scar and associated ptosis in patients with Horner's syndrome or a neurosurgical scar in patients with a 3rd nerve palsy.

Pupil Examination

• Important terminologies :

• Examination consists of four steps :

AnisocoriaIsocoria

Unequal pupils size (efferent or unilateral)

Equal pupils size (afferent or

bilateral)

1-Pupil Observation

• Start by a general observation, noting

1. The shape

2. The size of the pupil in ambient bright light. Size is measured in millimetres and the normal pupil ranges from 1-8 mm.

3. The symmetry.

2-Light reflex test

• Used to assess the integrity of the pupillarylight reflex pathway.

• Direct light reflex :

The examined eye is constricted when the light is shown.

• Indirect (consensual) light reflex :

The fellow eye will constrict.

(don’t stand in the front of the patient!!)

Indirect Light Reflex Test

3- Swinging Flashlight Test

• Also known as (Marcus gunn test).

• Used to compare between direct and consensual light reflex.

• It’s preformed by equal exposure of light to each eye.

• Normally both pupils should be of the same size and constricted.

• Abnormally if the pupil dilate if light is shown.

• That’s caused by withdrawal reflex of the fellow eye.

• Called as RAPD (relative afferent pupillarydefect).

Near Reflex

• Used to test accommodation.

• Preformed by asking the patient to fixed at distant the to bring it to a near object (arm’s length).

• Normally the pupil will have a brisk constriction.

• Near-light dissociation =significant better pupillary near reflex than light reflex.

Normal Pupil Reactions

• Will be :

PERRLA, -MG

•Pupils Equal Round and Responsive to Light and Accommodation

•Negative Marcus Gunn response

Diagnosis Keys

• Determine which pupil is abnormal.

• Search for associated signs.

Disorders of the pupil may result from:

• Ocular disease.

• Disorders of the controlling neurological pathway.

• Pharmacological action.

Anisocoria

• This is physiological in about 20% of people.

• How to assess it :

• An affected Large Pupil has poor constriction in a well lit room.

• An affected small pupil has poor dilatation in well lit room.

The abnormally reacting pupil

1- Light reflex test :

From severe optic nerve damage(transection)

The patient will be blind in one eye .

No reaction when the affected side is stimulated.

Opposite (Isocoria) (fellow)

The abnormally Reacting Pupil

2- 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, A mild RAPD may also occur in amblyopia .

The abnormally Reacting Pupil

• 3- Near light reflex :

• (light-near dissociation)

• Unilateral :afferent conduction defect, Adie pupil, herpes zoster ophthalmicus.

• Bilateral : neurosyphilis, diabetes, myotonicdystrophy, Parinaud'sdorsal midbrain

Diseases affecting the pupils

• Congenital : 1. Aniridia : bilateral

absence pupil. (Glaucoma)

2. Coloboma : partial absence of pupil.

3. Leukocoria : White pupil (retinoblastoma or congenital cataract)

Diseases affecting the pupils

• Acquired :

1. Pseudoexfoliation

syndrome :grey-white

fibrogranular extracellular matrix material deposited on the anterior lens.

2. Sphincter tear: due to trauma

3. Synechiae : post. between iris +lens or ant. Between iris and cornea.

Diseases affecting the pupils

• Neurological :1- Horner’s syndrome :disruption of the sympathetic

nerves supplying the eye.Triad of : • Partial ptosis (upper eyelid

drooping).• Miosis (pupillary constriction).• Enophthalmos .• (Normal pupillary reaction)

• Causes : Many causes : 1. Central : Multiple

sclerosis, spinal cord tumors Syringomyelia.

2. Preganglionic: Pancoast's tumour

3. Postganglionic : internal Carotid dissection

Horner’s syndrome :

2- 3rd cranial nerve palsy :

• Fixed and dilated pupil not reacting to light .

• Many causes at base of skull.

• Ptosis and 4 EOM paralysis , except lateral rectus and superior oblique.

3rd Nerve Palsy

3- Adie's tonic pupil:

Tonically dilated pupil reacts much significantly to accommodation more than light.

Caused by infection to ciliary ganglion.

4-Argyll Robertson pupils: Caused by neurosyphilis.

They are characterized by bilateral (usually asymmetrical) small, irregular pupils showing a light-near dissociation.

Difficult to dilate.

Drugs Affecting Pupil

•Mydriatics (bilateral or unilateral )

• Topical : sympathomimetics(eg, phenylephrine, adrenaline) and antimuscarinics (eg, cyclopentolate, tropicamide, atropine).

• Systemic: sympathomimetics (eg, adrenaline (epinephrine)) and antimuscarinics (eg, atropine).

•Miotics (bilateral or unilateral)

• Topical : muscarinicagonists (eg, pilocarpine).

• Systemic: opiates (eg, morphine and organophosphates).

Remember :

• Take a good history to help exclude an ocular cause for the pupillary changes and to see if a medical condition exists which may contribute to the pupillary problem.

• Determine whether it is the small or the large pupil that is abnormal.

• Search for associated signs that may help make a diagnosis.

Resources :

• http://www.patient.co.uk/

• Lecture notes on ophthalmology 9th edition.

Thanxxxxxxxxxx