Visual pathway and lesionsCEREBELLOPONTINE ANGLE AND THEIR CONTENTSCEREBELLOPONTINE ANGLE AND THEIR CONTENTS.pptx

Visual, pupillary and accommodation
reflex pathways and associated lesions
PRESENTER: DR HAPPYNES PIUS MBAWALA(MD,MMED-SUREGERY,COSECSA FCS
TRAINEE IN NEUROSURGERY

Anatomy of visual pathway
 Eyes acts like camera and relay information to the visual cortex via optic
pathway
 The path consist of
 Retina
 Optic nerve
 Optic chiasma
 Optic tract
 Lateral geniculate body
 Optic radiation
 Visual cortex

 The visual field is inverted and reverse relationship with the retina this means
 Superior part of the visual field will be represented by inferior part of retina and the inferior part of
visual field will be represented by superior part of retina
 Temporal part of visual field will be represented by nasal part of retina and the nasal part of the
visual field will be represented by temporal part of retina
 From retina the fibres will travel in the same side as the retina
 In optic chiasma the only the nasal fibres which carry information from temporal part of visual field
will cross while the temporal fibres which carries information from the nasal field will travel the same
side
 Optic tract consist of the
 Uncrossed temporal fibres of ipsilateral eye
 Nasal fibres from contralateral eye
 This phenomenon continue from optic tract lateral geniculate body ,optic radiation to visual cortex

 Optic chiasm
 It is located in suprasella cistern over the Sella turcica but also can be
prefixed (tuberculum Sella) or postfix (dorsum Sella )

Optic tract
 Some of fibres will go to the superior colliculi to the pretectal nucleus which
forms the pupillary reflex pathway
 Others will go to the lateral geniculate body

Lateral geniculate body
 Located at superior lateral of thalamus

Optic radiation
 They are called geniculocaricarine pathway
 Divided into two loops
 Meyer's loop/inferior fibres of optic radiation /temporal
• Which will arch around temporal horn of lateral ventricle through the
temporal lobe to the visual cortex
• This fibres carries superior fibres of visual field
 Baum loop/superior fibres of optic radiation/parietal
• Which goes superior to the parietal lobe to the carcarine fissure in visual
cortex
• This fibres carries inferior of visual field

Visual cortex
 Area 17 –in carcarine fissure –primary visual cortex
 Area 18 and 19 –either side or carcarine fissure –secondary visual cortex

Blood Supply and Lymphatics
 The blood supply and lymphatic factors for neuroanatomy of the visual
pathway include the following:
 Branches of the internal carotid artery supply the majority of the visual
system.
 The optic nerve's retina and extra cranial part receive blood from
 The ophthalmic artery.
 The intracranial part and optic chiasm receive supply from
 Anterior cerebral,
 Superior hypophyseal,
 Anterior communicating arteries.

 The optic tract
 The posterior communicating
 Anterior choroidal arteries
 Lateral geniculate nucleus
 The anterior and posterior choroidal arteries
 Optic radiation
 Both middle and posterior cerebral arteries .
 The primary visual cortex (Bradman area 17), Primarily supplied by
 The posterior cerebral artery with watershed areas processing peripheral
information.

 The optic nerve is 1 of the ways followed by the glymphatic system to drain
a part of the cerebrospinal fluid.
 The ophthalmic veins drain the orbit's back, top, and bottom.
 Their congestion and, therefore, their inadequate drainage produce retro-
ocular headaches and heavy and pulsating eyes.
 They pass through the upper orbital and the sphenoid fissure and continue
into the cavernous sinus.

Visual pathway lesion
 The visual field is inverted and reverse relationship with the retina this means
 Superior part of the visual field will be represented by inferior part of retina
and the inferior part of visual field will be represented by superior part of
retina
 Temporal part of visual field will be represented by nasal part of retina and
the nasal part of the visual field will be represented by temporal part of
retina

Terms
 Homonymous
 Both eyes are involved with the same laterality means if left or rt in both
eyes
 Congruent field defect
 Both eyes has similar field defect, can over lap each other
 Incongruent field defect
 Two eyes has no similar defect ,can not superimpose on each other

Congruent vs incongruent field defect

Optic nerve
 Features will be
 Complete blindness of affected eye
 Direct and consensual light reflex will be affected but when the light is
shown in unaffected eyes direct and consensual light reflex will be normal
 Causes can be
 Transection
 Tumour
 Stroke

Wilbrand knee
 This carries information from lower nasal fibers of optic nerve which carries
information from superior temporal field
 If affected will cause superior temporal field defect since it is near opposite
optic nerve so will be also either effect on macular part or complete
blindness of opposite eye

Pupillary reflex-constriction -
parasympathetic

Pupillary reflex- dilatation-sympathetic

Visual reflex syndromes
Parinaud syndrome
 Dr Henry Parinaud was French neurologist who is regarded to be founder of
neuroopthalmology
 Dorsal midbrain syndrome, the common causes are
 Tumour –pineoblastoma
 Stroke
 Hydroencephalus
 The syndrome consist of four signs
 Impairment of Upward gaze-sun set sign
 Convergence retraction nystagmus
 Collier’s sign which is retraction of eye lids
 Light near dissociation

Parinaud syndrome
 Impairment of upward gaze
 The lateral gaze are located at PPR-Paramedian pontine reticular formation
 The vertical gaze are located at the rostra part of mid brain which consist of
Upgaze and down gaze
 Upward gaze fibres cross over the opposite side and descend while the
down ward gaze decent without crossing over the opposite side
 So if there is lesion in dorsal part of midbrain the only the upward gaze will
be affected causing impairment in upward gaze while the downward gaze
will intact

Parinaud syndrome
 Eye lids retraction
 The action is done by levetor papebral superioris which is innervated by oculomotor nerve
 So if there is lesion in dorsal midbrain there will be disinhibition of oculomotor nerve so eye
lids go upward and retracted
 Convergence retraction nystagmus
 This is due to disinhibition of oculomotor nerve causing medial rectus to contract causing
convergence as well as superior as well as inferior rectus contraction causing nystagmus
 No divergence cause the sixth nerve is in the pons thus why not affected
 Light Near dissociation
 Accommodation reflex present but pupillary reflex is abscent cos its only light reflex which
goes to pretectal nucleus thus why can accommodate but no light reflex

ABNORMAL PUPILLARY REACTION
ADIE pupil
 Is abnormality in parasymphathetic system
 The reaction is poor or absent,tonic
Holmes –Adie syndrome
 It is adie pupil with decrease deep tendon reflex
 The pathophysiology is the damage to ciriary ganglion
 95% of all short ciriary nerves are going to supply ciriary muscles which are responsible for accommodation
 5% supply sphincter pupil which responsible for light reflex
 Present with anisocoria where the affected pupil is dilated and not responsive to light reflex and it get worse with light
 At the slit lump has sectoral palsy and vermiform movement of pupil due to abberent neuronal regeneration of nerve
 Light near dissociation
 Denarvation sensitivity which will be tested by diluted pilocarpine 0.125 after application check after 30-60 min ifor
hypersensitive pupil will react by contriction which you cant find in normal eye
 Treatment
 Reasurance as it is benign condition as time goes by the abberant regeneration will take place

Pupil abnormalities
ARGILL Robertson pupil
 Occur bilatellary
 Miosis
 Accommodate but does not react to light
 Due to tertiary syphilis in the mid brain

Pupil abnormalities
Marcus Gun pupil
 Relative Afferent pupillary defect
 Where by there is defect in afferent pathway in optic nerve causing no
pupillary reflex both same side or consensul when light is directed to the
affected eye while there is reflex when directed to unaffected eye
 Can be tested by swing light

ACCOMODATION REFLEX
 Is the process of making image of the object sharp in the retina
 When the object come near the ciliary muscle contact zonnule become relaxed lens become
convex to accommodate the object and when the object is far ciliary muscles relax causing
tension to the zonnule/suspensory ligament so the lens become less convex or stretch
 The structures/components involved are
 The lens become more convex
• This is done by contraction of ciliary muscles cause zonule/suspensory ligament to relax so the
lens become more convex
 Pupillary constriction
• Pupillary constrictor muscles
 Convergence
• Bilateral Medial rectus contraction

ACCOMODATION REFLEX
 Afferent pathway
 Is through optic nerve –optic tract –lateral geniculate body-optic radiation
–visual cortex(area 17)-visual association area (18,19) –frontal eye field
(area 8) in frontal lobe through superior longitudinal fascicullus –to
oculomotor nucleus through corticonuclear fibres
 Efferent pathway
 From oculomotor nucleus to
• Rectus muscles -convergence
• Pupillary constrictor muscles -pupillary constriction
• Ciliary muscles for lens accommodation

ACCOMODATION REFLEX
Mechanism
 The combined optical power of the cornea and the lens brings light from the environment
to focus on the retina.
 The mechanism of the accommodation reflex involves 3 responses:
 The convergence of both eyes is such that the near object is in focus, which aids in image
projection on the fovea.
• This action involves contraction of the medial rectus muscles of both eyes, with the
relaxation of lateral recti resulting in the adduction of both eyes.
 Constriction of the sphincter pupillae muscles and pupils improves the depth of focus.
• The divergent rays from distant objects scatter off the cornea's periphery so they do not fall
on the fovea.
 Contraction of bilateral ciliary muscles results in the thickening of the lens, which shortens
the focal length and increases its refractive power (measured in diopters).

ACCOMODATION REFLEX
Function
 The function of the accommodation reflex is to coordinate visual attention
to near objects.
 Proper convergence prevents diplopia, and pupil constriction increases the
depth of field.

ACCOMODATION REFLEX
Related Testing
 Examiners frequently check the accommodation reflex during a
neurological exam by having the patient focus on a small target, such as
the examiner's fingertip or a pen.
 The examiner asks the patient to focus on the target used for testing at a
distance and then gradually brings the finger within a few centimeters
between the patient's eyes.
 Look for convergence of eyes and constriction of the pupils.

ACCOMODATION REFLEX
Clinical Significance
 Dysfunction of the accommodation reflex can be physiological, like in aging and
presbyopia, or pathological or pharmacological.
 Accommodation deficits can occur in neurological conditions like
 Supranuclear lesions
 Encephalitis
 Pineal tumors
 Neuromuscular disorders like myasthenia gravis.
 It can also occur in systemic conditions, such as in children after
 A viral illness
 As a result of primary ocular conditions like glaucoma or cataracts.

ACCOMODATION REFLEX
1. Convergence
 Damage to the medial rectus muscle itself can disrupt convergence.
 A cortical or brainstem lesion can impair the neural machinery required to coordinate
ocular convergence.
 It can be congenital, presenting with strabismus in childhood.
 Near reflex insufficiency is a disorder of convergence; it can be mild paresis or complete
paralysis.
 For paresis, treatment involves reading glasses or bases in prisms.
 Convergence insufficiency can occur in individuals with the increased use of near work,
like in school-age children.
 It can occur as idiopathic or following viral illness.

ACCOMODATION REFLEX
1. Convergence
 Spasm of the near reflex is a functional condition associated with
 Diplopia
 Blurred vision
 Headaches
 Near reflex triad occurs even when the patient is not focusing on a near object.
 It affects mostly females.
 Convergent squint (esotropia) with miosis and pseudo myopia is a presenting feature
2. Pupillary Constriction
 Disrupting the parasympathetic pathway can dysregulate the coordination of pupillary
constriction.

ACCOMODATION REFLEX
3. Lens Accommodation
 The Accommodation amplitude decreases with age, and the near point of accommodation recedes.
 For example, at the age of 20 years, the nearest point of accommodation is approximately 10 cm, and by the age of 50
years, it has receded to approximately 50 cm.
 near point of accommodation is where the eyes can maintain a clear focus.
 As part of normal aging, there is a gradual loss of accommodation termed presbyopia
 Which refers to the hardening of the lens expected with age, with decreased ciliary muscular tension, contributing to the
loss of accommodation.
 Symptoms include
 Difficulty in near vision
 Blurred or double vision for near objects
 Eye fatigue or headache
 It is correctable with convex lenses for near vision.
 Disruption to lens integrity or the ciliary body, such as in conditions like cataracts or glaucoma, can also cause
accommodation reflex insufficiency.

Visual pathway and lesionsCEREBELLOPONTINE ANGLE AND THEIR CONTENTSCEREBELLOPONTINE ANGLE AND THEIR CONTENTS.pptx

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