Protect the eye from foreign object and perspiration.
The name of the tissue that lines the inside of the eyelid.
The conjunctiva.
Name of the opening that the tears drain through.
Puncta opening.
The eyelids' 3 types of closing are:
Blinking, voluntary winking and blepharospasm (involuntary rapid closing of the eyelids).
What is blepharospasm.
Involuntary rapid closing of the eyelids.
What is another name for involuntary rapid closing of the eyelids.
Blepharospasm.
Name the tissue that makes the eyelid continuous with the eyeball.
The conjunctiva.
What does the conjuctival membrane do?
It makes the eyelid continuous with the eyeball.
What does the conjuctivaMembrane consist of?
Epithelium and an underline Substantia propria.
What happens to the conjunctiva During inflammation?
The blood vessels can be seen as they dilate.
Part of the eye aka "whites of the Eye."
Scerla.
What are the phyiscal characteristics Of the sclera?
It's very rigid and vascular. It also Has dense fibrous tissue.
T/F. Sclera contributes to eye stability.
True.
What is the cornear important for?
Vision.
How does the cornea work?
The curved transparent window of the eye allows light to enter, become focused to give rise to an image in the retina.
The 3 layers the cornea consists of:
Epithelium, substantia propia and endothelium.
T/F. The cornea contains blood vessels.
False
What happens to the cornea during inflammation and what can be the consequence of this?
Vascular tissue forms on the cornea and can lead to impairment of vision.
How does the cornea receive oxygen?
Through passive diffusion from the nearby tears chamber and blood vessels.
How many ul of tears are in the eye annd what is the rate @ which they are cont. replaced?
7ul; 1ul/min.
The functions of tears are to?
To remove foreign matter, moisturize cornea, destroy bacteria and supply oxygen to cornea.
List the ophthalmic dosage forms.
GODSS: Gels, ointments, drug impregnated inserts, Suspensions and Solutions.
Part of the eye tear fluid is contained.
Cul de sac.
What is the normal volume of tear fluid?
7-8 ul.
A nonblinking eye can hold how much fluid?
30ul.
A blinking eye can hold how much?
10ul.
The approx. % of drug that is absorbed intraoccularly.
1%.
Dosage forms that increase contact time, thus increase bioavailability.
Gel and cream.
Name the 2 chambers where most of the drug goes to.
Tear and anterior.
What are the drug barriers/things that reduce Drug absorption @ the tear chamber.
Tear drainage, dilution, metabolism, protein binding, Loss from blinking (non-productive loss).
What are the barriers/things that reduce drug abs. @ Cornea?
Lipophillic/hydrophillic barrier and metabolism.
What are the barriers/things that reduce drug abs. @ Anterior chamber?
Metabolism, protein binding, turnover of aq. Humor.
What is one issue of systemic administration of an ophthalmic?
Dilution can occur in a large volume of distribution.
You can lose up to __% of drugs administered topically to eye, and have as little as __% or less absorption of drug.
90 and 1.
What dilutes the drug?
Tears from tear chamber.
Approx. how much dilution can we expect?
10-20%.
Why is there solution drainage ?
So that the instilled soln can = normal volume of tears.
Explain the relationship b/w volume of soln instilled and rate of draining.
As volume increases, draining increases.
How can draining be decreased?
Increasing viscosity.
Does drug loss increase or decrease if pt. closes eye forcefully?
Increases.
Most commercial droppers deliver how much soln?
30-75ul.
Besides viscosity, what is another way to reduce draining?
Use smaller drops.
How does tear turnover rate affect drug loss? What is the rate of tear t/o?
The rate is 15%/min. Tear t/o reduces the time that the eye has to absorb the drug.
T/F. only protein bound drugs can be removed by drainage in tear and aq. Humor
False. Free drugs can be removed too.
How can you minimize protein binding?
Prewash the eye to remove protein that binds.
Enzymes that metabolize opth drugs are found where?
Tears, cornea and aq. Humor.
T/F. Extensive metabolism occurs in the tear chamber.
False.
Extension metabolism occurs where in the eye?
Cornea and aq. Humor (contact time is longer).
What is the main barrier to absorption to the eye?
Cornea.
List thhe 3 parts of the cornea.
Epithelium, substantia propia, endothelium.
What factors affect the absorption of lipoliphillic drugs across corneal epithelium? How do each effect it?
pH, tonicity, and state of ionization. pH below 3 or above 11 can destroy epithelium= Increased drug uptake. Tonicity can stimulate tears= more dilution and drainage. State of ionization= nonionized =Better corneal penetration.
Most drugs cross the cornea by what mode of diffusion?
Passive.
Sodium and small molecules cross the cornea by what kind of diffusion?
Active.
What is the optimum partition coefficient for corneal penetration?
1000:1.
What can you do if you cannot include preservations in an ophthalmic soln (due to allergies)?
Put in single use container.
How can you modify an ophthalmic to increase effectiveness of preservative?
Increases it's viscosity to increase conact time w/ microorg. Use a thickening agent such as: Polyvinyl EtoH, methylcellulose and hydroxypropylcellulose/cellulose derivatives.
T/F. Cellulose thickening solns cannot be filtered; they must be autoclaved.
True.
T/F. Solubility of cellulose decreases in hot water.
True.
The preservative most effective against strains of P.aeruginosa?
Mix of Benzalkonium Cl (1:10000) and Polymyxin B Sulfate (1000USP units/mll) or benzalkonium cl (1:10000) and Disodium ethylenediaminetetraacetate (1:1000).
Which method of filtration is safe to use for ophthalmics? Why? Drawback of these methods?