Ocular therapeutics

Question 1

What is the sclera?

Answer 1

tough outerprotective membrane coat that protects the eye

Question 2

What is the lens?

Answer 2

Transparent, biconvex structure that helps create optical images and focus vision, suspended by lens zonules

Question 3

What supplies the eye with blood?

Answer 3

choroid

Question 4

What is the role of the lacrymal duct

Answer 4

provide tears which maintain the tear film on the corneal surface and induce a response to chemical and mechanical irritation

Question 5

What are the 3 layers of the pre corneal tear film?

Answer 5

outer thin lipid layer, central thick aqueous layer, inner mucus layer

Question 6

What is the role of the pre corneal tear film?

Answer 6

Protect eye against infection
Keeps cornea smooth and clean
Prevents corneal drying

Question 7

Is the cornea hydrophobic or hydrophilic?

Answer 7

Hydrophobic

But underling stroma is hydrophilic

Question 8

What is the role of the cornea?

Answer 8

Allows for passage and refraction of light and provides protection to the eye as it is a highly impermeable membrane that won’t allow particles to cross the eye

Question 9

What is the role of the aqueous humour

Answer 9

Transparent viscous fluid in the anterior chamber of the eye and maintains intraocular pressure and inflates the globe

• provides nutrition for avascular tissue
• transports antioxidants in anterior
• contains immunoglobulins for immune response

Question 10

What is the vitreous humour

Answer 10

Fills space between lens and retina - maintains anatomic expansion of the globe and impedes diffusion of substances between retina and anterior segmen.
Reservoir for O2, glucose, ascorbic acid, metabolic waste products
contains 99% water, collagen and large molecules

Question 11

What are photoreceptors

Answer 11

These are on the retinal surface - rods act in low light levels, no colour and no. spatial resolution, whereas Cones act in. higher light levels, have colour and spatial resolution

Question 12

What is the optic nerve

Answer 12

Rod/cone photoreceptors cause an action potential to generate in the optic nerve - pass into skull via the optic canal to meet at the optic chiasma. Nerves project to the visual cortex in occipital lobes

Question 13

What are the 4 main barriers to ocular drug delivery?

Answer 13

1. Corneal impermeability and enzymes
2. Tear reflex
3. Nasolacrimal drainage and blinking
4. Non-corneal absorption

Question 14

What are the desirable attributes for a drug for it to cross corneal epithelium?

Answer 14

Hydrophilic and hydrophobic properties

Question 15

What is the role of the iris?

Answer 15

Controls the diameter of the pupil and regulates how much light enters the eye e.g. pupil dilation

Question 16

when is the pH of the tear film at its lowest?

Answer 16

On awakening as you lose the carbon dioxide (have acid by products that produce when eyes are closed), then it increases as they open