<ul>
 <li>
 Pupil margin is positioned more anteriorly than the iris root and gets support from the lens
 </li>
 <li>Slightly off-centre: inferonasal</li>
 <li>Varies in size from 1 to 8mm in diameter</li>
 <li>
 Physiological anisocoria (less than 0.4mm difference) is present in 25% of the population and
 may change sides!
 </li>
 <li>Physiological tremor in pupil known as hippus (or pupillary athetosis)</li>
 <li>Mydriasis occurs in low light, excitement or fear</li>
 <li>Miosis occurs in illumination, convergence/accommodation and sleep</li>
 <li>
 The strength of constriction increases with light intensity up to 9 log units above the scotopic
 threshold and then levels off
 </li>
 <li>The pupil cannot respond to stimuli of greater than 5Hz frequency</li>
 <li>Pupillary dilatation:</li>
 <ul>
 <li>Reduced depth of field</li>
 <li>Reduced depth of focus</li>
 <li>Increased Stiles-Crawford effect (see below)</li>
 <li>Reduced diffraction of light</li>
 <li>Increased chromatic aberration</li>
 </ul>
 <li>
 Stiles-Crawford effect: light entering at the edge of the pupil is less effective at stimulating
 photoreceptors than light entering centrally because it meets the receptors obliquely rather
 than head on
 </li>
 <li>Pupil size is associated with:</li>
 <ul>
 <li>Iris colour: blue irises are larger than brown</li>
 <li>Autonomic nervous system: fatigue, exercise etc.</li>
 </ul>
</ul>
## Light reflexes
<ul>
 <li>Only one functioning pupil is needed to test the anterior visual pathways</li>
 <li>The latency of the pupil light reaction is 0.2 to 0.5s</li>
 <li>Afferent impulses travel from the retina through the optic nerve, chiasma and tracts</li>
 <ul>
 <li>
 Fibres leave the tract and synapse in the pretectal olivary nucleus near the
 superior colliculus
 </li>
 <li>Each pretectal nucleus receives only an ipsilateral input</li>
 <li>
 Axons of the pretectal nerve cells synapse with the parasympathetic nuclei (Edinger-Westphal
 nuclei) of the oculomotor nerve on BOTH sides of the midbrain
 </li>
 <li>
 Preganglionic fibres travel with the oculomotor nerve ( through its inferior division to the
 inferior oblique) to the ciliary ganglion and synapse
 </li>
 <li>
 Postganglionic fibres travel in the short ciliary nerves to the sphincter pupillae muscle and
 both pupils constrict
 </li>
 <li>
 Since both Edinger-Westphal nuclei are innervated, an unilateral optic nerve lesion will not
 affect the indirect/consensual response in the ipsilateral eye
 </li>
 </ul>
 <li>
 Pupillary reflexes originate in the brainstem and are therefore unaffected by cortical lesions
 </li>
 <li>Causes of efferent pupillary defect (fixed dilated pupil)</li>
 <ul>
 <li>
 Brain stem lesions at the level of the superior colliculus and red nucleus, typically
 accompanied by so-called long tract signs
 </li>
 <li>
 Third nerve lesions, usually compressive (but 20% of microvascular palsies involve the pupil)
 </li>
 <ul>
 <li>May be false localising sign in raised ICP causing uncal herniation</li>
 </ul>
 <li>Ciliary ganglion or short ciliary nerve lesions</li>
 <li>Iris damage due to surgery or grossly elevated IOP</li>
 <li>
 Mydriatic drugs (pilocarpine will not constrict such a pupil but will constrict a pupil
 affected by a neurological lesion)
 </li>
 </ul>
</ul>
## Mydriasis
<ul>
 <li>
 Contraction of the dilator pupillae (innervated by alpha-1-adrenergic{' '}
 receptors)
 </li>
 <li>Stimulated by noradrenergic sympathetic nerves passing through the ciliary ganglion</li>
</ul>
## Miosis
<ul>
 <li>Stimulation and contraction of sphincter pupillae&nbsp;</li>
 <li>Stimulated by cholinergic postganglionic parasympathetic fibres from the ciliary ganglion</li>
</ul>
## Horner&rsquo;s syndrome
<ul>
 <li>Interruption of the sympathetic chain in the head and neck</li>
 <li>Causes:</li>
 <ul>
 <li>
 Central brain stem lesions (ie. first-neurone: the descending reticulospinal fibres within the
 medulla oblongata eg. lateral medullary syndrome -see below)
 </li>
 <li>
 Preganglionic lesions (second neurone: travels from T1 exit over apex of lung and around first
 rib up to carotid bifurcation)
 </li>
 <li>
 Postganglionic lesions (third neurone: travels from superior cervical ganglion to eye along
 the internal carotid and within the cavernous sinus)
 </li>
 <ul>
 <li>
 No anhidrosis since the postganglionic sympathetic fibres controlling facial sweating follow
 the external carotid artery rather than the internal. They separate from the fibres to the
 pupil approximately at the level of the carotid bifurcation
 </li>
 </ul>
 </ul>
 <li>
 Anisocoria (especially in low light conditions) due to failure of normal dilation by the
 affected pupil
 </li>
</ul>
Classic drugs tests for Horner&rsquo;s
<ul>
 <li>
 Cocaine will not dilate a Horner&rsquo;s pupil since increasing adrenergic activity by
 preventing reuptake has no effect on an interrupted neural pathway
 </li>
 <li>
 Hydroxyamphetamine (increases adrenaline release from postganglionic nerve terminals) will
 dilate a first or second neurone Horner&rsquo;s but not a third order neurone lesion (since
 there&rsquo;s no noradrenaline to release)
 </li>
 <li>
 Adrenaline, apraclonidine and phenylephrine will dilate a post-ganglionic Horner&rsquo;s due to
 denervation hypersensitivity
 </li>
 <li>Note: there is no test to distinguish a second from a first-order lesion</li>
</ul>
<ClinicalCorrelate>
 <>
 Lateral medullary syndrome
 <ul>
 <li>Infarction of the ipsilateral posterior inferior cerebellar artery</li>
 <ul>
 <li>Cerebellum: ataxia</li>
 <li>IX and X nuclei: swallowing difficulty</li>
 <li>
 Descending sympathetic tracts: Horner&rsquo;s syndrome
 </li>
 <li>
 Spinothalamic tract: contralateral (due to decussation) sensory loss of pain and
 temperature
 </li>
 <li>Trigeminal nerve (sometimes involved): ipsilateral facial sensory loss</li>
 </ul>
 </ul>
 </>
</ClinicalCorrelate>
## Light-near dissociation
<ul>
 <li>When the near response is greater than the response to light</li>
 <ul>
 <li>Implies a diminished light response</li>
 </ul>
 <li>Causes</li>
 <ul>
 <li>Retinal lesions</li>
 <li>Optic nerve lesions</li>
 <li>Pineal lesions</li>
 <li>Pretectal lesions eg. Sylvian aqueduct syndrome, Argyll-Robertson</li>
 <li>
 Third nerve lesions: secondary to aberrant regeneration of neurones to the iris sphincter
 normally supplying medial rectus
 </li>
 <li>Ciliary ganglion lesions (as above for third nerve lesions), eg. Adie&rsquo;s</li>
 </ul>
</ul>
## Argyll-Robertson pupil
<ul>
 <li>Small pupil</li>
 <li>Unresponsive to light</li>
 <li>Good near response</li>
 <li>Does not dilate with atropine</li>
 <li>Physostigmine increases constriction</li>
 <li>Associated with neurosyphilis</li>
 <li>Lesion site unknown</li>
 <li>Absent tendon reflexes and iris atrophy are common</li>
</ul>
## Adie pupil
<ul>
 <li>Sluggish light reaction: may present with blurred vision due to mydriasis</li>
 <li>Strong near response (with light-near dissociation)</li>
 <li>
 Supersensitive to cholinergics eg. pilocarpine, due to &ldquo;post-denervation phenomenon&rdquo;
 </li>
</ul>
<ClinicalCorrelate>
 <>
 Using dilute pilocarpine can aid the diagnosis of an Adie&rsquo;s pupil
 <ul>
 <li>Lesion affects the ciliary ganglion</li>
 <li>Second eye involvement may not be noticed by the patient</li>
 </ul>
 </>
</ClinicalCorrelate>

AC to Lens

Pupil

Intro

FRCOphth Part 2 Study Notes

Tumours, masses and neoplasia

Tumours overview

Uveitis

Uveitis background

Anterior uveitis

Intermediate uveitis

Uveitis in JIA

Uveitis with JIA

Retinal vasculitis

Sarcoidosis

Behcet's disease

Toxoplasmosis

Strabismus

Overview

Viral uveitis

Esotropia

Fungal uveitis

Mycobacterial uveitis

Adnexal masses

Exotropia

Spirochaetal uveitis (including Syphilis)

Melanoma

Nematode uveitis

Retinoblastoma

Retinoblastoma (for Part 2)

Incomitent

Voyt-Koyanagi-Harada syndrome

Conjunctival intraepithelial neoplasia

Vertical deviations

Orbit and ocular adnexae

Orbit

Sympathetic ophthalmia

AV Malformations and hamartomas

Arteriovenous malformations and hamartomas

Restriction syndromes

Paediatrics

Leucocoria

Congenital Cataract

Paediatric Glaucoma

Retinopathy of prematurity

Retinopathy of Prematurity

ROP-like disorders

Congenital nasolacrimal duct obstruction

White dot syndromes

Aniridia: Short Arm 11 Deletion (11p13)

Choristomas

Management Of Amblyopia

Alphabet patterns

Iris Nodules

Scleritis

Meningioma

Strabismus surgery

Optic nerve glioma

Lymphoma

Extraocular Muscles

Rhabdomyosarcoma

Idiopathic orbital inflammation

Orbital neuroblastoma

Anterior Persistent Foetal Vasculature

Lacrimal system

Metastatic lesions

Surgical Retina

Retinal Detachment

Vitreoretinal Interface And Macular Hole

Epiretinal Membrane

Medical Retina

Diabetic Eye Disease

Orbital Blood Vessels

Retinal Vascular Disease

Macular Degeneration

Central Serous Chorioretinopathy (CSCR)

Sickle Cell Retinopathy

Retinitis Pigmentosa

Albinism

Retinal Telangiectasias

Miscellaneous Retinopathies

Atropine And Myopia Progression

Pharmacology

Side Effects Of Systemic Drugs

Foetal Alcohol Syndrome

Neuro-ophthalmology

Optic Neuropathy

Papilloedema

Idiopathic Intracranial Hypertension

Chiasmal Disorders

Retrochiasmal Disorders

Migraine

Paranasal Sinuses

Supranuclear Motility Disorders

Third Nerve Palsies

Fourth Nerve Palsies

Sixth Nerve Palsies

Seventh Nerve Palsies

Anisocoria

Myasthenia Gravis

Myopathies

Blepharospasm

Functional Visual Loss

Lacrimal Glands

Phakomatoses

Developmental diseases

Tear Film

Eyelids

Blinking

Lid Malpositions

Anterior segment - ocular surface

Conjunctiva

Conjunctivitis

Sclera

Pigmented Conjunctival Lesions

Squamous Cell Carcinoma Of The Conjunctiva

Ocular Cicatricial Pemphigoid

Cornea

Corneal Structure And Development