4 - Retina + central visual pathways Flashcards
Name the 2 main layers of the retina:
1) Retinal pigment epithelium
2) Neural layer
What is the function of the retinal pigment epithelium?
- Melanocytes absorb scattered light entering retina to protect against photooxidation of macula cells
- Transport nutrients to retinal visual cells
Why do albinos have problems seeing in bright sunlight?
- Retinal pigment epithelium is not pigmented (no melanin), so light entering retina is not dampened down = damaged macula cells
What are the 3 main types of cells in the neural layer of the retina?
1) Photoreceptor cells: rods and cones
2) Bipolar cells
3) Ganglion cells
Name the 2 main ways to view the retina:
1) Fundoscopy
2) Optical Coherence Tomography
Total blindness of one eye:
- where is the lesion?
- name some common causes:
Optic nerve
- Optic nerve glioma/meningioma
- Trauma
- Retinoblastoma
Bitemporal hemianopia:
- where is the lesion?
- name some common causes:
Optic chiasm
- Pituitary adenoma
- ACA aneurysm
Left homonymous hemianopia:
- where is the lesion?
- name some common causes:
Right optic tract
- Neoplasia
- Stroke
- Trauma
Left inferior homonymous quadrantonopia:
- where is the lesion?
- name some common causes:
Right superior parietal radiations
- Neoplasia
- Stroke
- Trauma
Right superior homonymous quadrantonopia:
- where is the lesion?
- name some common causes:
Left inferior temporal radiations (Meyer’s loop)
- Neoplasia
- Stroke
- Trauma
Left homonymous hemianopia with macula sparing:
- where is the lesion?
- what is the cause?
- why is the macula spared?
Right primary visual cortex (occipital lobe)
- Stroke in posterior cerebral artery
- Macula is supplied by MCA
Which nucleus is involved in the visual pathways?
Lateral geniculate nucleus
What is amaurosis fugax?
Name some common causes:
Sensation of ‘black curtain’ falling over 1 or both eyes temporarily
- TIA
- Giant cell arteritis
- Papilloedema
- MS
A pituitary adenoma can compress the optic chiasm. What visual change would this cause?
Bitemporal hemianopia
What visual change is associated with a stroke in the posterior cerebral artery?
Contralateral homonymous hemianopia with macular sparing
What is the function of the Medial Longitudinal Fasciculus?
Yokes the medial movement of one eye to the lateral movement of the other eye during lateral gaze
What is internuclear ophthalmoplegia?
Medial longitudinal fasciculus is damaged, so lateral gaze no longer linked
= abducting eye can move, but adducting eye cannot follow
What are some causes of internuclear ophthalmoplegia?
- MS
- Brainstem stroke
- Pontine glioma
A patient has a tumour arising from the right cavernous sinus and invading medially towards the optic chiasm. Which visual field defect might this result in?
Unilateral right nasal hemianopia
Destruction of the optic tract is rare. What would be the consequence of compression of the right optic tract?
Left homonymous hemianopia
Homonymous superior quadrantanopia is most commonly seen in lesions to which part of the visual pathway?
Meyer’s loop (inferior temporal optic radiation)
Which geniculate nucleus is involved in the visual pathway?
Lateral geniculate nucleus
Which geniculate nucleus is involved in the auditory pathway?
Medial geniculate pathway
Depolarisation of hair cells in the auditory pathway is dependant on the influx of which ion?
K+
Name some common causes of conductive hearing loss:
- Blocked EAM
- Ruptured tympanic membrane
- Otitis media
- Otosclerosis
- Rubella
Name some common causes of sensorineural hearing loss:
- Gentamicin toxicity
- Trauma
- Age-related loss
- Acoustic neuroma
- Tinnitus
- Congenital
- Neuropathy ie hyperbilirubinaemia
What are the 3 most common causes of vertigo?
1) BPV = Benign Paroxysmal positional vertigo
2) Acute labyrinthitis
3) Meniere’s disease
In which lobe is the auditory cortex?
Temporal lobe
Otitis media causes which type of hearing loss?
Conductive loss
Hyperbilirubinaemia can cause which type of hearing loss?
Sensori-neural (neuropathy)
