The Visual Pathways & Eye Flashcards
What are the 2 layers of the retina?
Pigmented layer
Neural layer
Name the outermost, middle and inner layers of the eyeball.
Outermost - sclera and cornea.
Middle - choroid, ciliary body and iris.
Innermost - retina.
List the order of cells in the neural layer of the retina from outermost to innermost.
Photoreceptors (rods and cones)
Horizontal cells
Bipolar cells
Ganglion cells
What is the relationship of the sclera and the dura mater?
The sclera is a continuation of the dura of the optic nerve.
Name the 2 most common causes of retinopathies.
Diabetes
Hypertension
What is papilloedema and what does it indicate?
Swollen optic discs
Sign of raised ICP
Which vessels are found in the optic sheath?
Central retinal artery and vein.
What are the macula and fovea?
Macula is a point in the visual field with the highest acuity where lots of cones are found. The fovea is a pit at the centre of the macula and provides the clearest acuity of all.
Why is the optic disc called a blind spot?
There are no photoreceptors here.
Where is the primary visual cortex located?
The occipital lobe.
What lobes are the superior and inferior radiations located in?
Superior - parietal lobe
Inferior - temporal lobe
What is tunnel vision and what causes it?
Bitemporal hemianopia, caused by a lesion at the optic chiasm.
What is the most common cause of bitemporal hemianopia/lesion at the optic chiasm?
Pituitary adenoma.
What causes right monocular blindness?
Lesion in the right optic nerve.
What causes left homonymous hemianopia?
Lesion in the right optic tract or geniculate nucleus.
What is the relationship between visual field, retina and radiations?
Inferior visual field projects to superior retina and superior radiations.
Vice versa.
What causes right homonymous superior quadrantonopia/pie in the sky defect?
Lesion in the left inferior radiation.
What causes left homonymous inferior quadrantonopia?
Lesion at right superior radiation.
What order neurones are in the optic radiations?
3rd order (project to cortex).
What causes macular sparing?
The occipital lobe has a dual blood supply - mainly from posterior cerebral artery but some contribution from middle cerebral artery. If there is a PCA infarct, the lobe still has supply from MCA, so the macula is spared.
What is central scotoma? What causes it?
Central black/grey spot in the middle of the visual field, caused by:
- macular degeneration
- strokes
- brain trauma
- disorders that affect the retina, choroid or optic nerve
What are the afferent and efferent branches of the pupillary light reflex?
Afferent = CN II Efferent = CN III
What muscle is responsible for pupil constriction?
Sphincter pupillae
What are the 3 steps of the accommodation reflex?
1 - eyes converge
2 - pupils constrict
3 - lens thickens
