Vision 2 Flashcards
How does visual acuity vary over the visual field?
Closer to the periphery the lower the visual acuity
How would we test someones visual field
Confrontation testing for outpatient screening
Automated Perimetry
Describe the visual pathway?
- > Right Eye
- > Right nasal and temporal fibres pass along optic nerve
- > At optic chiasma nasal fibres from each eye swap
- > Right temporal and left nasal fibres pass along right optic tract
- > Synapses at Lateral Geniculate Body (LGB)
- > All fibres pass through right optic radiation
- > Reach Right Primary Visual Cortex
How is the visual field divvied up between eyes?
Nasal fibres see the temporal field for that eye
Temporal fibres see the nasal field for that eye
What would right optic nerve damage cause?
Blindness in the right eye
What does damage to the middle of the optic chiasma cause?
Youll lose both your nasal fibres resulting in loss of the temporal part of both fields of view.
Bitemporal Hemianopia
What happens if theres damage to the right optic tract?
The left nasal and right temporal fibres are damaged
Resulting in loss of the entire left visual field,
Contralateral Homonymous Hemianopia
What happens if theres damage to the right optic radiation?
Contralateral Homonymous Hemianopia
Contralateral (left field of vision)
Homonymous (same on both sides)
Hemianopia (loss of half the field)
So you’d lose left field of vision on both eyes if you damaeg the right optic radiation
Whats the function of the eyes intrinsic muscles and their nerve supply?
They control pupil diameter & lens curvature
Ciliaris & constricter pupillae get parasympathetic innervation from Cr N III.
Dilator Pupillae gets sympathetic innervation
Whats the function of extrinsic muscles of the eye and their innervation?
Also known as extraocular muscles.
They move the eye
Most are supplied by ophthalmic branch of the trigeminal nerve (Cr N V1).
The Sup oblique is supplied by the trochlear nerve (IV), because it has a trochlea
The main abducting muscle (Lateral Rectus) is supplied by the VI nerve (Abducens)
List the extrinsic eye muscles?
4 straight (recti):
- Medial rectus
- Lateral “
- Superior “
- Inferior “
2 Obliques:
- Superior Oblique
- Inferior “
From where do the recti muscles arise and insert?
They all arise from the annular fibrous ring at the apex of the orbit and insert onto the sclera anteriorly
Describe the path of the sup oblique muscle
Sup Oblique arises from roof of the orbit posteriorly (lesser wing of sphenoid).
It is slung to the superomedial front of the orbit and crosses by the superior rectus, inserting on the sclera lateral to the sup rectus
Describe the path of the inferior oblique
Arises from the maxillary bone and crosses under the eye to insert onto the lateral, inferior, posterior surface of the sclera.
What muscle elevates the eyelid?
The Levator Palpebrae Superioris
It runs from the roof of the orbit to the upper eyelid, basically on top of the sup rectus