1.06 Ciliary body, aqueous humour & IOP

Question 1

What is the ciliary body

Answer 1

it produces the aqueous
it has a ring shaped structure situated behind the limbus

Question 2

what are the two parts that the ciliary body can be divided into

Answer 2

the pars plicata (closer to the iris, pupil and lens)
and the pars plana (closer to the retina)

Question 3

what are the layers of the ciliary body

Answer 3

1. supraciliary layer
2. ciliary muscle
3. stroma
4. epithelial layers –> outer basement, pigmented epithelium, non pigemneted epithelium, inner basement membrane

Question 4

which type of muscles are only found in the pars plicata

Answer 4

sphincteric muscles

Question 5

production of aqueous humour

Answer 5

flow of aqueous from posterior to anterior and then out through the angle. the aqueous starts at the blood supply so a good blood supply is needed.

Aqueous is formed in ciliary body processes, moves out around the lens and through pupil and flows out of anterior chamber through trabecular meshwork into Schlemm’s canal and then to episcleral veins.

Question 6

what is aqueous humour?

Answer 6

• A clear fluid in the anterior and posterior chambers of the eye
• produced by the epithelial cells or the ciliary body
• Provides nutrition to cornea and lens
• Removes excretory products from lens and cornea
• Contributes to the maintenance of the intraocular pressure of the eye.

Question 7

what are the 3 mechanisms that contribute to production and secretion of aqueous humour

Answer 7

1. diffusion (passive) - movement from high to low concentration, small molecules, lipid-soluble substances.
2. ultrafiltration (passive) - involves hydrostatic pressure, movement from high to low pressure
3. active secretion (active) - high energy bond (ATP) not dependent on conc gradient.

Question 8

Intraocular pressure

Answer 8

IOP relies on the balance between the:
1. secretion of aqueous humour from the ciliary body
2. outflow resistance in the trabecular meshwork

Question 9

what is the normal range of IOP that 95% of the population have

Answer 9

11-22mmHg

Question 10

what is the range of aqueous production

Answer 10

2.75 +/- 0.63 micro litres per minute

Question 11

what could too low IOP mean

Answer 11

retinal detachment
hypotony maculopathy (leakage)
suprachoroidal haem

Question 12

what does high IOP result in

Answer 12

glaucoma

Question 13

factors which increase IOP

Answer 13

lying down
lid pressure
drinking (not alcohol)
pulse
diurnal variation
apprehension

Question 14

factors that can reduce IOP

Answer 14

accommodation
exercise
seasonal
some drugs

Question 15

what can we use to detect glaucoma

Answer 15

tonometry
visual field
optic disk assessment
history: age, race, family history, myopia, diabetes and blood pressure

Question 16

indentation tonometer

Answer 16

• indent the cornea
• the amount your cornea gets indented by the plunger is proprtional to the IOP
• px lies down and the cornea is anaesthetised
• rest vertically on the cornea and read off the scale

Question 17

what are the disadvantages of the indentation tonometer

Answer 17

• difficult to read the scale
• The tonometer weighs a lot
• disliked by patients as they have to lie down flat and is quite invasive

Question 18

what is the applanation tonometer

Answer 18

• flattening the cornea
• displace less aqueous