Vision Flashcards
What are some important arteries that supply the eye?
- ICA branches into ophthalmic artery branches into central retinal artery (pierces optic nerve to supply inner 2/3 of retina - end artery)
What is the lamina cribrosa?
Sieve-like hole in sclera to allow exit of optic nerve
What are the parts of the optic disc we can see when we look at the retina? What are they made up of?
Rim (made up of axons)
Cup (lamina cribrosa/bare sclera)
What is the clinical importance of the central retinal artery?
It is an end artery, can become blocked from a clot that has travelled from ICA and this damages retina if clot is not cleared
Signs - pale retina, cherry-red spot (fovea)
What are the features of the macula when looking at the retina?
- darker
- BVs avoid it
- temporal side of optic disc
How can you tell the difference between arteries and veins in the retina?
Arteries appear thinner than veins
Describe the features of the branching of the central retinal artery.
Divides into four branches which keep subdividing into capillary networks that are most dense in macula and absent from the foveal avascular zone (which can be seen in an OCTA)
What happens to the foveal avascular zone in diabetes?
It gets bigger due to capillary dropout
How is a fluorescein angiogram of the retina described?
Hyper-fluorescent/hypo-fluorescent
How is optic disc described in fundoscopy?
Colour of rim
- orange (normal)
- pale
Contour
- sharp/defined (normal)
- undefined (disc is swollen)
Cupping
What does the retina look like in raised intracranial pressure?
Pale, red streaks, indistinct optic disc
-optic nerve surrounded by dura mater + arachnoid sheaths - central retinal vein within is compressed by pressure transmitted along subarachnoid space - congestion - papilloedema
What do the ciliary arteries branch off and supply?
Branch off ophthalmic artery to supply uvea (choroid, ciliary body, iris)
What are the conceptual layers of the retina?
- Inner neural layer
- Outer pigmented layer
Where would the eye be injected?
Aim of ora serrata as there are no important structures underneath and retina stops here
Describe the retinal pigment epithelium.
choroid - Bruch’s membrane - RPE - potential space - photoreceptors
- multiple microvilli extend out + surround outer segments of photoreceptors
- potential space is where retinal detachment occurs
- normally, GAGs act as glue and water is actively transported out, creating -ve pressure
- tight junctions (outer retina-blood border)
Gives eye immune privilege + highly selective transport of glucose, retinal from Vit A and specialised phospholipids - photoreceptors shed outer segments -> creates free radicals
- choroid has high blood flow but little O2 is extracted
- light energy
- RPE live in highly oxidative environment (lipofuscin can accumulate over life)
- RPE absorbs light
- RPE phagocytoses shed outer tips of photoreceptors
- secretes VEGF which keeps capillaries in choroid fenestrated
