Visual

The Visual Pathway

Key anatomy

Key anatomy

Temporal

Nasal

• Optic disc • Optic nerve head • Optic nerve • Macula • Fovea • Fovealis

Retina Chiasma Optic Nerve

LGB

Lower fibres (Temp lobe)

Optic radiation

Upper fibres (ant parietal lobe)

Occipital Cortex

Retina Chiasma Optic Nerve

LGB

Lower fibres (Temp lobe)

Optic radiation

Upper fibres (ant parietal lobe)

Occipital Cortex

Retina Chiasma Optic Nerve

LGB

Lower fibres (Temp lobe)

Optic radiation

Upper fibres (ant parietal lobe)

Occipital Cortex

Retina Chiasma Optic Nerve

LGB

Lower fibres (Temp lobe)

Optic radiation

Upper fibres (ant parietal lobe)

Occipital Cortex

Retina Chiasma Optic Nerve

LGB

Lower fibres (Temp lobe)

Optic radiation

Upper fibres (ant parietal lobe)

Occipital Cortex

Retina Chiasma Optic Nerve

LGB

Lower fibres (Temp lobe)

Optic radiation

Upper fibres (ant parietal lobe)

Occipital Cortex

Retina Chiasma Optic Nerve

LGB

Lower fibres (Temp lobe)

Optic radiation

Upper fibres (ant parietal lobe)

Occipital Cortex

The Eye Muscles

Extra Ocular Eye Muscles

IO

SR

LR

SR

LR

MR

IR

SO

IR

IO

SR

LR

SR

LR

MR

IR

SO

Lateral Rectus: • Origin = tendinous ring on bony orbit around optic foramen • Insertion = lateral wall of eyeball • Action = turns eye laterally

IR

IO

SR

LR

SR

LR

MR

IR

SO

Medial Rectus: • Origin = tendinous ring on bony orbit around optic foramen • Insertion = Medial wall of eyeball • Action = turns eye medially

IR

IO

SR

LR

SR

LR

MR

IR

SO

Superior Rectus: • Origin = tendinous ring on bony orbit around optic foramen • Insertion = Superior and central part of eyeball • Action = turns eye upwards and outwards

IR

IO

SR

LR

SR

LR

MR

IR

SO

Inferior Rectus: • Origin = tendinous ring on bony orbit around optic foramen • Insertion = inferior and central part of eyeball • Action = turns eye downwards and inwards

IR

IO

SR

LR

SR

LR

MR

IR

SO

IR

Superior Oblique: • Origin = tendinous ring on bony orbit around optic foramen • Insertion = between superior and lateral recti muscles • Action = rotates eyeball on its axis – directs cornea downwards and laterally (note – via the trochlear)

IO

SR

LR

SR

LR

MR

IR

SO

IR

Inferior Oblique: • Origin = maxilla (front of orbital cavity) • Insertion = between inferior and lateral recti muscles • Action = rotates eyeball on its axis – directs cornea upwards and laterally

Superior Rectus Muscle

Nose

Superior Oblique

Superior Rectus

Inferior Rectus

Inferior Oblique

Superior Oblique

Medial Rectus

Lateral Rectus

R = Superior Rectus L = Inferior Oblique

Both = Superior Recti & Inferior Oblique

R = Inferior Oblique L = Superior Rectus

R = Lateral Rectus L = Medial Rectus

R & L = Primary Position

R = Medial Rectus L = Lateral Rectus

R = Inferior Rectus L = Superior Oblique

Both = Inferior Recti & Superior Oblique

R = Superior Oblique L = Inferior Rectus

Superior Rectus & Inferior Oblique

Inferior Rectus & Superior Oblique

Left VI Nerve Palsy (lateral Rectus)

Left IV Nerve Palsy Superior Oblique)

Left III Nerve Palsy

IO

SR

LR

SR

LR

MR

IR

SO

Lateral Rectus = VI cranial nerve (Abducens)

IR

IO

SR

LR

SR

LR

MR

IR

SO

Lateral Rectus = VI cranial nerve (Abducens) Superior Oblique = IV cranial nerve (Trochlear)

IR

IO

SR

LR

SR

LR

MR

IR

SO

Lateral Rectus = VI cranial nerve (Abducens) Superior Oblique = IV cranial nerve (Trochlear) All others = III cranial nerve (Occulomotor)

IR

The Pupils

Pupils • Parasympathetic – Originate from the subnucleus of the III nerve and synapse in the cilliary ganglion – Supplies the constrictor pupillae of the iris

• Sympathetic – Originate in the hypothalamus, pass down the brain stem, cervical spine to emerge at T1 and return to the eye

Pupils • Lesions of the sympathetic pathway produce Horner’s syndrome – Constricted pupil – Partial ptosis – Unilateral Ahydrosis

• Optic nerve lesions produce Afferent defects – Impairs direct response to light – Consensual response unaffected in diseased eye

• III nerve lesions, cilliary ganglion and sympathetic supply produce Efferent disorders of the pupil

Afferent Pathway

Efferent Pathway

Cilliary Body - Iris

Optic Nerve Cilliary Ganglion Convergence Centre Lateral Geniculate Body

Edinger – Westphal Nucleus of III

Pretectal Nucleus

Pupils Afferent = Optic nerve (II) Efferent = Occulomotor (III)

Direct Pupil Reaction to Light

Pupils Afferent = Optic nerve (II) Efferent = Occulomotor (III)

Consensual Pupil Reaction to Light

Pupils

Diseased Eye

Afferent = Optic nerve (II) Efferent = Occulomotor (III)

Afferent Pupil Defect

Pupils

Diseased Eye

Afferent = Optic nerve (II) Efferent = Occulomotor (III)

Afferent Pupil Defect –

no pupil response

Pupil defects •

RAPD – Marcus Gunn Pupil – – – –

•

Partial Damage to optic nerve (therefore Afferent defect) Pupils symmetrical but degree of dilation is variable Retrobulbar neuritis etc Use ‘swinging torch test’ to detect affected pupil

Argyle Robertson Pupil – Mid brain lesion, Neuro-syphilis – Small irregular pupils, fixed to light but constricts on convergence

•

Holmes Adie Pupil (Adie pupil) – Cilliary ganglion lesion – Unilateral Fully dilated pupil, un-reactive to light

•

III Nerve Palsy – Dilated pupil + Infero-lateral position of the eye, complete ptosis