Eye anatomy review

Question 1

describe the production and drainage of aqueous humour

Answer 1

produced by the ciliary processes of the ciliary body and into the posterior chamber of the eye located between the iris and the ciliary body and the lens, then up between the iris and anterior surface of the lens, through the pupil and into the anterior chamber of the eye between the cornea and the iris.
drainage then out through the drainage angle of the eye which includes the trabecular meshwork (occluded in open angle glaucoma) and the canal of Schlemm, then into the episcleral vessels and then systemic venous circulation.

but note also 10-20% of aq humour drains via uveoscleral route where avoids trabecular meshwork but passes instead into root of iris and/or ciliary muscle, then into scleral vascular system.
*importance of this route-drainage increased by alpha agonists and PG analogues to reduce IOP.

Question 2

function of aq humour?

Answer 2

maintains an adequate pressure in the eye
IOP is a balance between rate of production and clearance of aqueous
this is measured with tonometer-measures force needed to flatten the corneal surface

Question 3

normal range of IOP?

Answer 3

11-21 mmHg

more than 21 considered ocular HTN but note corneal thickness is a correction factor for this

Question 4

how does a raised IOP link to glaucoma?

Answer 4

it is a significant RF for glaucoma, but does NOT mean that a diagnosis of glaucoma can be made-this refers to a progressive optic neuropathy which can occur in the presence of normal IOP (normal tension glaucoma).

Question 5

functions of the cornea?

Answer 5

maintain transparency of eye
ocular protection (including corneal reflex)
refraction of incoming light (along with overlying tear film)

Question 6

5 layers of the cornea?

Answer 6

epithelium-non-keratinized stratified squamous
bowman's membrane
stroma
descemet's membrane
endothelium