The eye is the most interesting organ due to its drug disposition characteristics. ▪ The Novel approach of drug delivery system in which the drug that can be Instilled on the cull de sac cavity of the eye is known as the Ocular drug delivery system.  (cull de sac cavity: the space between eyelids and eye balls) ▪Ocular drug delivery is one of the most challenging tasks faced by Pharmaceutical researchers. ▪One of the major barriers of ocular medication is to obtain and maintain a therapeutic level at the site of action for a prolonged period of time. ▪The bioavailability of ophthalmic drugs is very poor due to efficient protective mechanisms of the eye.

1. Barriers of Drug Permeation in
Ocular Drug Delivery System
By – Sakshi Mishra
M.Pharm 1st year (Pharmaceutics)
Institute of Pharmaceutical Research
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2. CONTENTS
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• Introduction
• The anatomy of the eye
• Mechanism of Drug Absorption
• Barriers of Drug Permeation
• Various factors responsible for disposition of ocular drugs
• Eye infections

3. LEARNING OBJECTIVES
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 The learning objective of this topic is to provide
the knowledge about designing a therapeutic
system to achieve an optimal concentration of a
drug at the active site for the appropriate
duration.

4. INTRODUCTION
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 Eye is most interesting organ due to its drug
disposition characteristics.
 The Novel approach of drug delivery system
in which drug can Instilled on the cull de sac
cavity of eye is known as Ocular drug
delivery system.
 (cull de sac cavity: the space between eye
lids and eye balls)

5. Ocular drug delivery is one of the most challenging
tasks faced by the Pharmaceutical researchers.
One of the major barriers of ocular medication is to
obtain and maintain a therapeutic level at the site of
action for prolonged period of time.
The bioavailability of ophthalmic drugs is very poor
due to efficient protective mechanisms of the eye.
5

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7. THE ANATOMY OF THE EYE
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 Diameter 23 mm
 Structure comprises of three layers
1. Outermost layer : The clear, transparent cornea and the white,
opaque sclera
2. Middle layer: The iris anteriorly, the
choroid posteriorly, and the ciliary body at the
intermediate part
3. Inner layer : Retina (extension of CNS)
 Other parts-
A.Sclera (white portion of the eye) is the tough
white sheath that forms the outer-layer of the
ball. It maintains the shape of the eye.



8. THE ANATOMY OF THE EYE
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 B. The conjunctiva is a thin transparent mucous
epithelial barrier, lines the inside of the eyelids,
and covers the anterior one-third of the eyeball.
 C. The cornea is a strong clear bulge located at
the front of the eye. It refracts light entering the
eye which then passes through the pupil and
onto the lens.
 D. The aqueous humor is a watery fluid that fills
the "anterior chamber of the eye" which is
located behind the cornea and in front of the lens

9. THE ANATOMY OF THE EYE
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 E. Pupil - circular aperture in the centre of the iris
through which light passes into the eye.
 F. The iris is a thin circular contractile curtain located
in front of the lens but behind the cornea.
 G. The ciliary muscle controls accommodation for
viewing objects at varying distances and regulates
the flow of aqueous humour into schlemm’s canal.
 H. The lens located behind the pupil of the eye and
encircled by the ciliary muscles. It helps to refract
light travelling through the eye.

10. THE ANATOMY OF THE EYE
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I. The vitreous humour is a perfectly transparent
thin-jelly-like substance that fills the chamber
behind the lens of the eye
 J. The retina may be described as the "screen"
on which an image is formed by light that has
passed into the eye via the cornea, aqueous
humour, pupil, lens, and vitreous humour before
reaching the retina.
 K. The center of the retina is called the macula.
They convert light into nerve signals

11. THE ANATOMY OF THE EYE
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 L. The choroid layer is located behind the retina
and absorbs unused radiation and nourishes the
outer portions of the retina.
 M. The optic nerve - responsible for transmitting
nerve signals from the eye to the brain..

12. Barriers in Ocular Absorption
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Precorneal constraints
• Spillage of drug by overflow/Solution drainage
• Nasolachrimal drainage/systemic absorption
• Tear dilution,
• Enzymatic metabolism

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14. Barriers in Ocular Absorption
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Corneal constraints
1.Outer-Epithelium (lipophilic)
2.Middle-Stroma (hydrophilic), Conjunctival
absorption
3.Inner-Endothelium (lipophilic )

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16. Various factors responsible for disposition of
ocular drugs
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• Bioavailability of drugs.
• Size of the protein drug complex.
• Rapid and extensive elimination of drugs from the precorneal
lachrymal fluid.
• Metabolic degradation of the drug substance.
• Drugs, which are highly water insoluble, do not readily
permeate the cornea.

17. EYE INFECTIONS
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A) Conjunctivitis:
 Conjunctivitis is infection of the membrane lining the eyelids
(conjunctiva).
 Causative agents- Staphylococcus aureus, Haemophilus
influenzae, Streptococcus pneumoniae.

18. B) Corneal ulcers/ Keratitis: Inflammation of cornea (Keratitis)
is characterized by corneal oedema, cellular infiltration & ciliary
congestion.
•Associated bacteria- Staphylococcus aureus, Pseudomonas
pyocyanea, E.coli and Proteus etc.
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19. C) Endophthalmitis: It is severe form of intraocular inflammation
(purulent uveitis) involving ocular cavities & inner coats of
eyeball.
•Causative organisms- Streptococci, E.coli, Pseudomonas, etc.
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20. References
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1. http://samples.jbpub.com/9781284025682/9781449674250_CH10.pdf
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4289909/
3. https://ijpsr.com/bft-article/ocular-drug-delivery-system-an-
overview/?view=fulltext
4. https://www.slideshare.net/sagarsavale1/ocular-drug-delivery-system-
odds-
62796410#:~:text=%EF%81%B6%20%E2%80%9CThe%20Novel%20approa
ch%20of,solutions%2C%20suspensions%2C%20and%20ointments.
5. https://image.slidesharecdn.com/ophthalmicdrugdeliverysystem-
140807032711-phpapp02/95/ophthalmic-drug-delivery-system-14-
638.jpg?cb=1407382074
6. https://image.slidesharecdn.com/oculardrugdeliverysystemodds-
160607054339/95/ocular-drug-delivery-system-odds-11-
638.jpg?cb=1538550547

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