5 Retina and Visual Pathways Flashcards
Describe each of the following that make up the retina:
- Pigmented layer
- Photoreceptor layer
- Horizontal cells
- Bipolar cells
What is the name of the nucleus from which the optic radiations leave to reach the primary visual cortex (occipital lobe)?
Lateral geniculate nucleus
(part of the thalamus)
Where would the lesion be to cause monocular blindness?
Optic nerve (of one eye) before optic chiasm
Where would the lesion be to cause bitemporal hemianopia?
Optic chiasm
(Temporal visual field lost as nasal fibres lost)
Where would the lesion need to be to cause right homonymous hemianopia?
Lesion to optic tract after optic chiasm
Remember- describe according to field loss so if left nerve will be right homonymous hemianopia- contralateral
Where would the lesion have to be to cause a homonymous inferior quandrantanopia?
Lesion to superior optic radiation (parietal lobe)
Where would the lesion have to be to cause a homonymous superior quandrantanopia?
Lesion to inferior optic radiation (parietal lobe)
Other than a lesion to the optic tract (after chiasm), what else can cause a homonmous hemianopia?
Stroke affecting both superior and inferior optic radiations
Non-vascular damage to the occipital lobe can cause homonymous hemianopia without macular sparing.
Explain how macular sparing can occur if there is a stroke affecting the posterior cerebral artery.
- Occipital lobe dual blood supply
- Posterior cerebral
- Middle cerebral artery (supplies occipital pole)
- Therefore central function= spared
Outline the accomodation reflex in terms of:
- Afferent arm
- Processing centres
- Efferent arm
Afferent arm: Optic nerve CN II
Processing centres:
- Visual cortex (has to know image is closer)
- then to edinger westphal nuclei
Efferent arm: Occulomotor nerve CN III
What are the 3 effects of the accomodation reflex? (3Cs)
- Convergence
- Eyes converge- medial rectus
- Constriction
- Constrictor pupillae
- Convexity
- Lens becomes more convex- increase refractive power-cilliary muscles
Outline the light reflex in terms of:
- Afferent arm
- Processing centre
- Efferent arm
- Afferent arm
- Optic nerve
- Processing centre
- Pretectal nucleus (mediates consensual light reflex)
- Projects bilaterally to pretectal nucleus
- Pretectal nucleus (mediates consensual light reflex)
- Efferent arm
- Oculomotor
What is fundoscopy? Give an example of a pathology it can detect.
Examination of the retina
- Hypertensive retinopathy
- Diabetic retinopathy
- Macular degeneration
What is amaurosis fugax?
Sudden visual loss due to occlusion of central retinal artery (branch of ophthalmic artery)
Curtain coming down over vision
What is OCT (optical coherence tomography)?
OCT= specialist technique used to visualise layers of retina
Normal: retina
Fill in the labels:
- Macula: Point of highest acuity
- =LATERAL to optic disc
- Branches of central retinal artery: visible on macula
