Eye Flashcards
(15 cards)
What are the three layers of the eye (from outer to inner)?
Fibrous layer – sclera and cornea
Vascular layer (uvea) – choroid, ciliary body, iris
Neural layer – retina
What type of photoreceptors are found in the retina and what are their functions?
Rods – sensitive to low light, peripheral and night vision
Cones – detect colour and detail, concentrated in the fovea
What is the function of the fovea centralis?
It provides the highest visual acuity; it contains a high density of cones and no rods.
What is the optic disc, and why is it called the blind spot?
The optic disc is where the optic nerve exits the eye; it contains no photoreceptors, so it creates a natural blind spot.
Which retinal cells transmit signals from photoreceptors to ganglion cells?
Bipolar cells
What is the role of ganglion cells in the retina?
They generate action potentials that travel via the optic nerve to the brain.
What is the visual pathway from the retina to the visual cortex?
Retina → Optic nerve → Optic chiasm → Optic tract → Lateral geniculate nucleus (LGN) → Optic radiations → Primary visual cortex (V1)
Which part of the visual field is processed by the left primary visual cortex?
The right visual field from both eyes
What happens at the optic chiasm?
Fibres from the nasal retinae of both eyes cross to the opposite side; temporal fibres remain ipsilateral.
What would a lesion in the left optic tract cause?
Right homonymous hemianopia – loss of right visual field in both eyes
What is the function of the ciliary body?
It produces aqueous humor and contains muscles that adjust lens shape for accommodation.
What is the pupillary light reflex and what pathway does it involve?
Constriction of pupils in response to light.
Pathway: Retina → Pretectal nucleus → Edinger–Westphal nucleus → CN III → Ciliary ganglion → Pupil constrictor muscles
What neurotransmitter is released by photoreceptors in darkness?
Glutamate – which inhibits bipolar cells
What is the difference between scotopic and photopic vision?
Scotopic: Vision in low light (rods dominate)
Photopic: Vision in bright light (cones dominate)
Which clinical condition is caused by increased intraocular pressure?
Glaucoma – damages optic nerve, can lead to blindness
