Ocular Delivery

Question 1

What is the anterior segment of the eye?

Answer 1

Front

Question 2

What is the posterior segment of the eye?

Answer 2

Back

Question 3

What is the eye volume?

Answer 3

7 µL

Question 4

What are usual eyedrops doses?

Answer 4

20 to 50 µL

Question 5

Why is there limited uptake of eyedrops?

Answer 5

Tear dilution
Short acting
Limited volume of the eye

Question 6

What percentage of eyedrops are usually absorbed?

Answer 6

6.5%

Question 7

How are posterior segment diseases treated?

Answer 7

Intravetreal injection

Question 8

What eye condition would intavetrial injections be used for?

Answer 8

Age Related macular degeneration (avastin)

Question 9

What are periocular injections?

Answer 9

Subconjunctival
Subtenon
Peribublar
Retrobublar

Question 10

What are the routes can be used to treat eye conditions?

Answer 10

Parental – blood aqueous barrier and blood retinal barrier overcome
Oral – limited accessibility to many targeted ocular tissues

Question 11

What are the six static ocular barriers?

Answer 11

Cornea
Sclera
Tear film
Conjunctiva
Vitreos humour
Retina

Question 12

How does the cornea act as a barrier?

Answer 12

It is the outermost transparent layer
Drugs need to be negatively charged but anti-microbials positively charged

Question 13

How does the sclera act as a ocular barrier?

Answer 13

It is structurally supportive
Drug moves through holes in matrix
The matrix is made from mucopolysaccharides and collagen

Question 14

What gland releases tears and how they spread?

Answer 14

Lacrimal gland
Spread via blinking creating a tear film

Question 15

How thick is the tear film and what is its pH?

Answer 15

7 µm thick
PH 7.3 to 7.7

Question 16

What is the role of the tear film?

Answer 16

Remove material from surface of eye (drugs)

Question 17

What layers make up the tear film?

Answer 17

External lipid layer
Middle aqueous layer
Adherent mucus layer

Question 18

what is the surface area of the conjunctiva

Answer 18

18 cm²

Question 19

What is the function of the conjunctiva?

Answer 19

Help form and maintain pre-corneal tear film

Question 20

How does the conjunctiva act as a barrier?

Answer 20

It has tight junctions

Question 21

What is the function of the virtuous humour?

Answer 21

Shape support of retina and lens

Question 22

How does the retina act as a barrier?

Answer 22

The blood retina barrier
Drugs enter choroid but struggle in the retina

Question 23

What are other barriers to ocular delivery other than static barriers?

Answer 23

Dynamic ocular – blood and lymphatic system
Metabolic ocular and eflux pumps

Question 24

What are three types of ocular implants?

Answer 24

Subconjunctival implant – for anterior segment disease
Intrasceral- both anterior and posterior
Intravetreal- posterior

Question 25

What drug does Ocusert deliver, for how long and for what condition?

Answer 25

Pilocarpine, one week, glaucoma

Question 26

How does Ocusert treat glaucoma ?

Answer 26

Increases aqueous humour outflow, decreasing intra ocular pressure

Question 27

What kinetics does Ocusert follow?

Answer 27

Zero order kinetics, membrane permeation control and depends on excess drug in reservoir

Question 28

What is the mechanism of Ocusert?

Answer 28

Water enters through ethylene membrane, dissolves drug

Question 29

What are the advantages of Ocusert?

Answer 29

Reduced installations of eyedrops

Question 30

What are two other examples of non-biodegradable ocular implants?

Answer 30

Vitrasert- aids Related retinitis. Attached to sclera- side effect is retinal detachment Retisert- prevents blindness. 30 month delivery ,smaller so smaller incision.

Question 31

What are disadvantages of non-biodegradable implants?

Answer 31

Large incisions Need expert Cost Need surchers, or other anchors Need re-implantation once drug completely released Side effects include retinal detachment and cataracts

Question 32

What are examples of biodegradable ocular implants?

Answer 32

Lacrisert- Made of HPC, treats dry eye by stabilising and thickening the pre-corneal tear film- prolongs tear break up time. Side effects include blurred vision and irritation. Ozurdex- Dexamethasone for macular Odema, intro, PLGA matrix. Six month delivery.