Flashcards in Retina Deck (70)
By how much does the retina extend over the posterior globe
What is it internally bound by? What about externally?
Internally: vitreous body
Externally: Bruch's membrane of choroid
What color is the retina? What about after death?
Reddish because of rhodopsin. Grays/opacifies after death
What are the two main functions of the retina and what structures are responsible for it?
1. Detect light and movements: Rods
2. Color and vision form (central visual field):Cones
What are the rods and cones named after?
Their outer segments; Rods have a rod like appearance, cones haves conical shaped outer segments
Where is the retina thinnest? Where is it thickest?
Thinnest centrally and peripherally: optic disc
Thickest: near macula
What refers to the internal background of the eye
What color is the fundus oculi and why?
Reddish/orange because of the choroidal vessels and RPE
What color is the fundus of a person who is dark skin, fair, skin, and albino?
Dark skin: darker, gray fundi
Fair skin: Lighter fundi
Albino: Can see choroidal vessels..they are devoid of pigment; extremely photophobic
Where does the optic nerve leave the eye and where is it located?
At the optic disc/papilla. Located 3mm medially and slightly above the posterior pole
T/F the optic disc has photoreceptors
False; optic disc is devoid of photoreceptors. Its projection into space produces the blind spot
Where is the fovea centralis located?
Temporal to and below the posterior pole (1-2 mm in diameter)
What does retinal thinning do to fovea centralis?
It makes a shallow depression in the surface and nerve elements are heaped around to form Henle's layer
What is the foveola? How big is it?
It is in the fovea, and it only contains cones. 0.35 mm in diameter
What is the macula lutea?
Yellow spot, that has a yellowish pigment because xanthophyll is found here
What is the function of the ora serrata. Where does it lie?
It is a notched line which separates the neural part of the retinal periphery from the ciliary body. It lies 8.5 mm behind the limbus and 6 mm in front of the equator
Arteries are ____ and veins are _____
What are the normal artery to vein ratio?
thinner and lighter. veins are thicker and darker. No anastomoses should be present. 2:3
T/F Fovea should contain vessels
False! No vessels should be present
What are the four subdivision in the retina
1. Pigment epithelial layer
2. Photoreceptor Layer
3. Intermediate Cell Layer
4. Ganglion Cell Layer
What is the function of the RPE? Where is it attached?
Absorbs scattered light. Doesnt multiply (no mitosis) When the cell dies, neighboring cell occupies the space. It's attached to Bruch's membrane. There are about 5 million in each eye
How many photoreceptors is the pigment epithelium in contact with?
Less obvious functions of RPE
Provide slow disintegration, a role in phagocytic activity
T/F There is a connection between the RPE and receptors
What type of cells are the photoreceptors and how are they arranged
Sensory cells; transform light into electrical energy by chemical processes. They have a palisade arrangement (held in place by the external limiting membrane)
How long are the rods? what does the outer segment consist of?
40-60 micrometers. Outer segment consists of rhodopsin which has 600-1000 stacked units called lamellae
At what rate are they formed? When does sloughing off occur? When do they get renewed
1 -5 per hour. Sloughed off In the morning. Rod lamellae can be completely renewed after 1-2 weeks.
T/F Sensation is the same for all wavelengths of light
How many bipolar cells do several rods connect with to produce a convergence
1 bipolar cell
Where are the outer segments of cones located
attached to the cell membrane