49 Vision I Flashcards
There are ____ layers in the eye
3
The outer layer of the eye consists of?
Sclera, cornea
The middle layer of the eye consists of?
Choroid, ciliary body, iris
The inner layer of the eye consists of ?
Retina, epithelium of the ciliary body, epithelium of the iris
The sclera consists of __________ cells.
Collagen fibroblast
What is the limbus?
The corneoscleral junction
The cornea accounts for ______ of the total refraction of incoming light?
2/3
List the 5 layers of the cornea.
- Epithelium
- Bowman’s membrane
- Stroma
- Descemet’s membrane
- Endothelium
Branches of the ____________ nerve provide sensory information to the cornea. Lesion of it will lead to?
nasociliary nerve (CNV1); cornea ulcers
The cornea is avascular and thus advantageous for?
corneal grafting
In which layer is there a basement epithelium that divides and thus continuous turnover?
Epithelium
______________ contains numerous nerve fibers which are sensitive to pain, and for corneal reflex.
Epithelium
*multilayered
What is the function of the Bowman’s membrane?
For support, protection against infection
What is stroma and what happened if it is damaged?
Regular arrangement of multiple fibroblast nuclei layers to produce transparency.
Damage > reduced transparency (opaque lens)
Function of the Descement’s membrane?
Support
as the basement membrane of the endothelium
Which of the following is true about the endothelium of the cornea?
A. It undergoes turnover
B. Defect (e.g. corneal edema) will cause reduced transparency
C. Regulates the fluid in and out of the cornea by creating a barrier
All except A
therefore will degenerate as person ages
How does the lens acquire nutrients when being avascular?
Receive nutrients from the aqueous humour
The lens is covered by _______________.
Lens capsule
Inherently tends to be spherical but maintains flattened by _____________.
tension in the zonular fibers
Which of the following about the lens are correct?
A. Lens epithelial cells appears around the lens
B. The cells transform into lens fibers towards the equator
C. Nucleus of the lens cells will devoid
All except A
lens epithelium only at the anterior side
___________ surface or iris is covered by 2 layers of pigmented epithelium continuous with that of the ciliary epithelium.
Posterior
At the further end of the iris, there is _______________ muscles innervated by _________.
Sphincter pupillae;
CN3 (EW nucleus)
Which muscle is present along the whole length of the iris? What its the innervation?
Dilator pupillae;
superior cervical ganglion (alpha 1 receptor)
The iris epithelium consists of _____layer(s) (pigmented).
2 layers
- anterior layer: give rise to dilator msucles
- Posterior layer of epithelial cell
The iris epithelium is continuous with the ciliary epithelium in which the outer layer is ___________ while the inner layer is ______________.
pigmented; (further from lens)
non-pigemented (closer to lens)
__________ is the major origin of aqeuous humour. How many layers of epithelium does it contain?
Ciliary body;
2
State the flow of aqueous humour.
Ciliary epithelium > secreted into posterior chamber > pupil > anterior chamber > Trabecular meshwork > Canal of Schlemm > episcleral veins
_________ is the most common form of glaucoma. It is due to?
Open-angle glaucoma;
- slow blockade of the Canal of Schlemm, with wide and open iridocorneal angle
- decreased outflow of aqueous humour through the tracbecular meshwork cause gradual reduction of peripheral vision.
Why can pilocarpine treat open-angle glaucoma?
It contracts the ciliary muscles (it is a muscarinic agonist)
What is close-angle glaucoma?
Closed iridocorneal angle, cannot drain into the trabecular meshwork, causing sudden rise in intraocular pressure, and retinal ganglion cell death.
What drug can worsen the angle-closure glaucoma?
Atropine, as it causes relaxation of the ciliary muscle.
Name all the layers of the retina.
- Retinal pigmented epithelium
Neural retina
- Outer nuclear layer
- Outer plexiform layer
- Inner nuclear layer
- Inner plexiform layer
- Ganglion cell layer
Which of the following about the retinal pigment epithelium is correct?
A. It contains multiple layers
B. It does not undergo mitosis
C. It is firmly attached to the choroid normally
D. It contains melanin
C and D
A: single layer
B: It has continuous removal of the outer photoreceptor segments (photopigment) > defects lead to slow blindness
The outer nuclear layer contains?
Cell bodies of photoreceptors (rods and cones)
The inner nuclear layer contains?
- Bipolar cells
- Amacrine cells (for contrast enhancement, movement detection, no axons)
- Horizontal cells
- Cell bodies of Muller cells
Ganglion cell layer contains?
Ganglion cells: sole output of retina to brain
Muller cells are distributed in what layers?
Functions?
Spans the whole length, but cell bodies at the inner nuclear layer
Function like astrocytes,
Is there any oligodendrocytes in the retina?
No! only Muller cells in which their processes are associated with most retinal cells
Retinal detachment is the detachment of __________ from ___________.
Neural retina from the retinal pigmented epithelium
The fovea is always __________ to the optic disk.
Temporal
*avascular!
Optic disk only contains _____________, and is pierced by ___________.
axons of ganglion cells;
central retinal artery and vein
Meninges of optic nerve continuous with that of brain: hence ________________ of optic nerve is continuous with that of the brain > extends to sclera behind the optic disk.
Clinical significance?
subarachnoid space;
Raised intracranial pressure transmitted along the SAS to the region behind the optic disc led to papilledema (swelling of optic disk)
Other than hydrocephalus, name a cause of papilledema.
glaucoma
