Visual System Flashcards
What are the three layers of the eye?
- Corneoscleral coat
- Uveal tract
- Retina
Describe the corneoscleral coat
- Outermost layer of the eye
- Transparent anterior extension of the sclera
Describe the uveal tract
- Middle layer of the eye
- Vascular coat
- Consists of iris and ciliary body anteriorly and vascularised choroid coat posteriorly
Describe the retina
- Innermost layer of the eye
- Consists of layers of nerve cells, their processes, support cells and on the outside, a layer of pigmented epithelium.
Describe the lens
- Biconcave disc
- Elastic to allow change in shape to permit accommodation for near vision.
What lies in front of the lens?
- 2 chambers filled with aqueous humour.
- An anterior chamber and a posterior chamber.
What lies behind the lens?
The much larger vitreal cavity filled with vitreous humor, which is avascular and gelatinous due to collagen fibres and hyaluronic acid.
What are the reasons for high visual acuity in the fovea centralis?
- Thinning of retinal layers
- Lack of rods, high concentration of cones
- Low convergence
At what point do the axons of the optic nerve become myelinated?
Not myelinated within the eye, but are myelinated after passing the lamina cribrosa.
What forms myelin in the optic nerve?
Oligodendrocytes
What is the primary visual cortex also known as?
- Striate cortex
- Because a prominent stripe of myelinated fibres are found in layer 4 which can be seen with the naked eye.
- Called the line of Gennari
Where is information from the lower visual field projected to?
The gyrus superior to the calcarine sulcus
Where is information from the upper visual field projected to?
The gyrus inferior to the calcarine sulcus
Where does the macula project to?
The posterior pole of the visual cortex - it occupies a much greater portion of the cortex relative to the size of the visual field it covers.
