Visual pathway kHem

VISUAL PATHWAY& PUPILLARY REFELEXES

Presented By:Khemchand SahuMBBS Final Part I

Guided By:Dr. Divya Verma

Asst. ProfessorDept. of Ophthalmology

Lt. Shri Lakhiram Agrawal Memorial Medical College, Raigarh

Visual Pathway 2

Contents• Anatomy & Physiology of Visual Pathway• Lesions of the Visual Pathway• Pupillary Reflexes• Abnormalities of Pupillary Reflexes

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Visual Pathway• Visual pathway or Optic Pathway is the nervous

pathway that transmits impulses from retina to visual center in cerebral cortex

• Components• Optic Nerve• Optic Chiasma• Optic Tract• Lateral Geniculate Bodies• Optic Radiations • Visual Cortex

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OPTIC NERVE• 2nd cranial nerve• Extent : optic disc to optic chiasma• 47-50 mm• Formation

• Axons of ganglionic cells of retina

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• Parts of Optic Nerve• Intraocular part• Intraorbital part• Intracanalicular part• Intracranial part

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• Intraocular part• 1 mm• Starts from optic disc, pierces the choroid & sclera,

converting it into sieve like structure Lamina Cribrosa

• Intraorbital part• 30 mm• From back of the eyeball to optic foramina• Relation

• Ant : Seperated from the ocular muscle by the orbital fat• Post : Closely surrounded by Annulus of Zinn

• Retro bulbar Neuritis : Painful ocular movements

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• Intracanalicular part• 6-9 mm in length• Lies within the optic canal• Relation

• Inferolateral : Ophthalmic artery• Medial : Ethmoid & Post. Ethmoid Sinus

• Intracranial part• 10 mm• Lies above the cavernous sinus

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OPTIC CHIASMA• Flattened structure• 12 mm horizontally, 8

mm anteroposteriorly• Lies over tuberculum

& diaphargma sellae• Fibers originating

from nasal halves of the retina decussate at the chiasma

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OpticChiasma

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OPTIC TRACT• Cylindrical bundle of

nerve fibers• Runs outward &

backward from posterolateral aspect of optic chiasma

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OpticTract

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LATERAL GENICULATE BODY• Oval structure• Situated at posterior termination of optic tract• Each geniculate body consists of 6 layers of

neurons (Grey Matter) alternating with white matter

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Lateral Geniculate

Body

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OPTIC RADIATION• 3rd order neuron• Extend from lateral geniculate body to visual

cortex

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Optic Radiation

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VISUAL CORTEX• Location : medial aspect of occipital lobe, above

and below calcarine fissure• Areas• Primary Visual Area (Area 17)

• Perception of visual impulses

• Secondary Visual Area (Area 18)• Interpretation of visual impulses

• Occipital Eye field (Area 19)• Concerned with movement of eye ball

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Blood Supply of Optic Nerve Head• Surface Layer : capillaries

from retinal arterioles• Prelaminar region : Vessels of

peripapillary choroid & lamina cribrosa

• Lamina Cribrosa : posterior ciliary arteries, areterial circle of zinn

• Retrolaminar part– Centrifugal branches of central

retinal artery– Centrifugal branches from Pial

plexus

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LESIONS OF VISUAL PATHWAY

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Lesions of Visual Pathway 18

OPTIC NERVE LESION• Causes

• Optic atrophy• Traumatic avulsion of optic nerve• Indirect optic neuropathy• Ischemic optic neuropathy• Acute optic neuritis

• Clinical features

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Proximal Optic Nerve Lesion Distal Optic Nerve Lesion

•Ipsilateral Blindness•Contralateral hemianopia•Abolition of direct light reflex on affected side & consensual on contralateral side•Near reflex is intact

•Ipsilateral blindness•Abolition of direct light reflex on affected side & consensual on contralateral side•Near reflex is intact


CHIASMAL LESION• Causes– Intrinsic

• Gliomas• Multiple sclerosis

– Extrinsic : compressive lesion• Pituitary adenoma• Craniopharyngiomas• Meningiomas

– Other• Metabolic• Toxic• Inflammatory

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Clinical feature of chiasmal lesion

• CHIASMAL SYNDROME

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Anterior Chiasmal Syndrome

Affected part : Ipsilateral Optic Nerve fiber & Contralateral inferonasal fiber

Junctional Scotoma

Middle Chiasmal Syndrome

Affected part : Decussating fibers in the body of chiasma

Bitemporal hemianopia

Posterior Chiasmal Syndrome

Affected part : Caudal fiber

Paracenbitemporal field defectHomonymous hemianopia on

contralateral side


• LATERAL CHIASMAL LESION• Causes• Distension of 3rd ventricle• Atheroma of the carotid or posterior

communicating arteries

• Features• Binasal Hemianopia

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OPTIC TRACT LESION• Causes• Intrinsic• Demyelinating diseases• Infarction

• Extrinsic• Pituitary adenoma• Craniopharyngioma

• Others• Syphilitic meningitis• Tubercular meningitis

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• Clinical Feature• Incongruous Homonymous Hemianopia• Wernicke’s reaction• Optic disc changes• Descending partial optic atropy : temporal pallor on

side of lesion & bow-tie atrophy on contralateral side

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LESION OF LATERAL GENICULATE BODY• Features• Homonymous Hemianopia• Normal pupillary reflexes• Optic disc pallor due to partial descending

atrophy

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LESION OF OPTIC RADIATION

• Causes• Vascular occlusion• Tumor• Trauma• Temporal lobectomy

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• Features

Visual Field Defect

Superior Quadrantic Hemianopia

Inferior fibers

involved

Inferior Quadrantic Hemianopia

Superior fibers

involved

Complete Homonymous Hemianopia

Total fiber of optic radiation

involved

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LESION OF VISUAL CORTEX• Causes• Occlusion of posterior cerebral artery• Head injury

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• Visual Field Defect• Congruous Homonymous

hemianopia (sparing the macula)

• Congruous Homonymous Macular defect

• Bilateral Homonymous macular defect

• Bilateral Homonymous Hemianopia with macula sparing

• Other Manifestation• Cortical Blindness• Dyschromatopsia• Visual Hallucination• Palinopsia• Polyopsia

Features

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PUPILLARY REFLEXES

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LIGHT REFLEX• When light is shone in one eye both the pupils

constricts.• Two Types:• Direct Light Reflex• Indirect (Consensual) Light Reflex

• Constriction of pupil to which light is shone : Direct Light Reflex and that of other : Indirect Light Reflex

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Afferent Fiber

From retina to pretectal nucleus

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Pathway of light Reflex

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NEAR REFLEX• Occurs on looking at near object• Two components• Convergence Reflex : Contraction of pupil on

convergence• Accommodation Reflex : Contraction of pupil associated

with accommodation

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Pathway of Near Reflex

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PSYCHOSENSORY REFLEX• Dilatation of pupil in response to sensory &

psychic stimuli

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EXAMINATION OF PUPILLARY REFLEXES

• Direct Light Reflex• Normal pupil reacts briskly &

its constriction to light is well maintained

• Consensual Light Reflex• Normally contralateral pupil

should also constrict when light is thrown on to one pupil

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• Swinging Flash Light Test• Performed when relative

afferent pathway defect is suspected in one eye

• Normally, both pupil constrict equally & pupil to which light is transferred is tightly constricted

• MARCUS-GUNN Pupil

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• Near Reflex• Pupil constrict while looking at near object


ABNORMALITIES OF PUPILLARY REACTIONS

• AMAUROTIC LIGHT REFLEX• Absence of

• Direct light reflex on affected side• Consensual light reflex on normal

• Lesion : Optic Nerve, Retina of affected side

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• EFFERENT PATHWAY DEFECT• Absence of

• Both direct & consensual light reflex on affected side

• Presence of• Both direct & consensual light reflex on normal side

• Cause : Sphincter paralysisParasympatholytic Drug (Atropine)IIIrd nerve paralysisInternal Ophthalomoplegia

AMAUROTIC PUPIL


• WERNICKE’S HEMIANOPIC PUPIL• Light reflex is ABSENT

• When light is thrown on temporal half retina of affected side & nasal half of opposite side

• Light reflex is PRESENT• When light is thrown on nasal half of affected side & temporal half of

opposite side

• Lesion of optic tract

• MARCUS-GUNN PUPIL• Seen in Relative Afferent Pupillary Defect (RAPD)• Affected pupil will dilate when light is moved from normal to

abnormal eye• Earliest indication of optic nerve disease• Cause : Incomplete optic nerve lesion, Severe retinal disease• Test : Swinging Flash Light Test

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• ARGYLL ROBERTSON PUPIL (ARP)• For both pupil• Reaction to near reflex : Present• But light reflex : Absent

• Both pupil slightly small in size• Cause – Neurosyphilis in region of tectum

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• ADIE’S TONIC PUPIL• Reaction to

• Light reflex : Absent• Near reflex : Very slow & tonic

• Affected pupil is larger (Anisocoria) initially• Cause : Postganglionic parasympathetic pupillomotor damage• Constricts with weak Pilocarpine (0.125%), while normal does not

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ANISOCORIA

• Normal size pupil : 3-4 mm• Difference between size of two pupil is called

Anisocoria • Causes• Physiological • Pathological

• Difference of 2 mm or more

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Pathological Anisocoria

Abnormal Miosis

Iridocyclitis

Horner Syndrome

Parasympathomimetic Drug

Mydriasis

Parasymapatholytic Drug

Retinal Glaucoma

3rd nerve Paralysis


• Evaluation of Anisocoria• Pupil Size• Anisocoria in dark & bright illumination :

Physiological• Anisocoria greater in dim illumination : Horner

Syndrome

• Pupillary Light Reflex• Normal light reaction followed by dilatation lag :

Horner Syndrome• Poor light reaction : Parasympathetic System Defect

(3rd nerve palsy, tonic pupil, anti-cholinergic drug)

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– Pharmacological Test :

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For suspected parasympathetic palsy : PILOCARPINE TEST

Pupil Constrict to low conc. of pilocarpine (0.125%)• Adie’s Tonic Pupil

Pupil Constrict to usual conc. of pilocarpine (1-2%)• 3rd nerve palsy

Pupil does not constrict to pilocarpine• Pharmacological mydriasis

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…tHANK yOU28/11/2016

Visual pathway kHem

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