4.1.1 The Retina Flashcards
What are the 3 layers of the eye?
Sclera- continuous with the dural sheath of optic nerve
Uvea- choroid and lens / ciliary body anteriorly
Retina- pigmented and neural layer
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What does the pigmented layer do?
Absorbs excess light to prevent light from scattering in the eye causing a glare
Determines amount of light that gets to the retina
Why can albinos develop photophobia?
Reduced pigment in the eye, this leads to light rebounding in the eye causing a glare
What do photoreceptor cells do?
Rods and Cones
Rods- Black and white vision, active at low light intensity e.g. at night
Cones- colour vision, active at high light levels
What do horizontal cells do?
Lateral inhibition leading to higher definition at the edges and increased contrast, inhibitory interneurones
Prevents too many neural impulses
What do bipolar cells do?
First order neurones
Act to connect photoreceptor cells to retinal axons
Collect information and interact with retinal ganglion cells
What can be found on fundoscopy?
Retinopathies
-Hypertension
-Diabetes
Vascular occlusions
-Branch of central retinal artery or vein
-Amaurosis fugax
Macula
-Degeneration
Optic disc
-Papilloedema
ROMV
Image of normal retina
What are some features about the fovea?
-Highest density of photoreceptors
-Rich cone content
-Thin, dips therefore, reduced impediment of light to reach cones
What happens at the optic disc?
Vessels all converge here
Where retinal axons coalesce to form the optic nerve
Optic nerve exits here
What happens in retinal detachment?
Photoreceptors separate from the underlying pigment epithelium
Fluid builds up between the layers
Separation of neural layer from pigmented layer
What are some symptoms of retinal detachment?
Sudden blurring
Vision loss
Visual artefacts
What is amaurosis fugax?
Painless loss of vision due to central retinal artery occlusion
Described as curtain coming down over you
What can be used to visualise the layers of the retina?
Optical Coherence Tomography OCT
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