Eye diseases are commonly encountered in day to day life, which are cured or prevented through the conventionally used dosage forms. Delivery to the internal parts of the eye still remains troublesome due to the anatomical and protective structure of the eye. Drugs may be delivered to the eye through the application of four primary modes of administration: topical, systemic, intravitreal, and periocular.

1. 1
APPROACHES OF DRUG
DELIVERY TO EYES

2. 2
CONTENTS
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•
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INTRODUCTION
ANATOMY AND PHYSIOLOGY OF EYE
BARRIERS
FORMULATION CONSIDERATIONS
IDEAL CHARACTERISTICS
DRUG DELIVERY SYSTEMS
EVALUATION
ADVANTAGES AND DISADVANTAGES
CONCLUSION
REFERENCES

3. 3
INTRODUCTION
• Eye diseases are commonly encountered in day to day life, which are
cured or prevented through the conventionally used dosage forms
like eye drops, ointments, etc., Ocular drug delivery systems are
intended for installation into the cul-de-sac, i.e., the space between
the eye ball and the eye lids. Delivery to the internal parts of the eye
still remains troublesome due to the anatomical and protective
structure of the eye. Drugs may be delivered to the eye through the
application of four primary modes of administration: topical,
systemic, intravitreal, and periocular.

4. 4
ANATOMY AND PHYSIOLOGY OF
EYE

5. 5
BARRIERS FOR DRUG ABSORPTION
• Tears
• Cornea
• Conjuctiva
• Sclera
• Retina

6. 6
FORMULATION CONSIDERATIONS
• Physicochemical
characteristics
polymers.
• Buffering capacity and pH.
• Instillation volume.
• Osmotic pressure.
of
drug
and

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Ideal characteristics of ocular drug
delivery system
• Good corneal penetration.
• Prolong contact time with corneal tissue.
• Non irritative and non toxic.
• Good rheological properties.
• Non greasy
• Patient compliance.

8. DRUG DELIVERY SYSTEMS TO EYE:
IMPLANTS
DENDRIMERS
IONTOPHORESIS
MICROEMULSION
MICRONEEDLE
NANOSUSPENSION
CONTACT LENSES
8

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1.CONVENTIONAL SYSTEMS
• EYE DROPS: To prolong the retention time of topically
applied drugs, anterior DDSs for eye-drops utilizing
interaction
physiological
between
drug
environment
carrier
of
(excipients)
cornea
and/or
and
sub-
conjunctiva are being developed. These are administered in
the form of Solutions, Emulsion and Suspension eye drops
and are used only for anterior segment disorders.

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•OINTLENTS AND GELS
Prolongation of drug contact time with the external ocular surface can be achieved
using ophthalmic ointment vehicle but, the major drawback of this dosage form like,
blurring of vision and blinking of eyelids can limits its use. These products will stay on
eyes longer than eye drops.
•INSERTS
Ocular insert are sterile preparation that prolong residence time of drug with a
controlled release manner and negligible or less affected by naso-lacrimal damage. The
ocular inserts maintain an effective drug concentration in the target tissues and yet
minimize the number of applications.

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2.VESICULAR SYSTEMS
• LIPOSOMES: Liposomes are vesicles composed of lipid membrane
enclosing an aqueous volume. These structures are formed simultaneously
when a matrix of phospholipids are agitated in an aqueous medium to
disperse the two phases. They are having an intimate contact with the
corneal and conjunctival surfaces which is desirable for drugs that are
poorly absorbed.
• NIOSOMES AND DISCOMES : Niosomes are nonionic surfactant
vesicles that have potential applications in the delivery of hydrophobic or
amphiphilic drugs. Discomes
are discoidal vesicles and may act as
potential drug delivery carriers by releasing the drug in a sustained manner
at the ocular site.

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•PHARMACOSOMES: Drugs possessing a free carboxyl group or an active
hydrogen atom can be esterified to the hydroxyl group of a lipid molecule, thus
generating an amphiphilic prodrug. This amphiphilic prodrug is converted to
pharmacosomes on dilution with water. pharmacosomes show greater shelf stability,
facilitated transport across the cornea, and a controlled release profile.

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3.CONTROLLED RELEASE
• IMPLANTS: implants are effective drug delivery system for chronic
ocular diseases like cytomegalovirus (CMV), retinitis. Intravitreal implants
of fluocinolone acetonide were developed for the treatment of posterior
segment.
• DENDRIMERS: Dendrimers are repetitively branched molecules and can
be successfully used for ocular drug administration and have better watersolubility, bioavailability and biocompatibility.

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•IONTOPHORESIS: Iontophoresis is a noninvasive technique for ocular drug
delivery. In iontophoresis the drug solution is in contact with the cornea in an eye-cup
bearing an electrode and the diffusion of drug
occurs by electrical potential
difference.
•MICROEMULSION: Microemulsion is dispersion of water and oil stabilized using
surfactant and co-surfactant to reduce interfacial tension and usually characterized by
small droplet size(100 nm), higher thermodynamic stability and clear appearance.
They reduce the frequency of administration as compared to the conventional systems.

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•NANOSUSPENSION: Nanosuspensions have emerged as a promising strategy
for the efficient delivery of hydrophobic drugs because they enhanced not only
the rate and extent of ophthalmic drug absorption but also the intensity of drug
action with significant extended duration of drug effect.
•CONTACT LENSES: Water soluble drugs soaked in drug solutions can be
absorbed through Contact lenses. The drug saturated contact lenses are placed in
the eye which releases the drug in eye for a long period of time. For prolongation
of ocular residence time of the drugs, hydrophilic contact lenses can be used.

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4.PARTICULATE SYSTEMS (NANOPARTICLES
AND MICROPARTICLES)
• Nanoparticles are prepared using bioadhesive polymers to provide
sustained effect to the entrapped drugs. An optimal corneal penetration of
the encapsulated drug was reported in presence of bioadhesive polymer
chitosan.
• Microemulsions have a transparent appearance, with thermodynamic
stability and a small droplet size in the dispersed phase (aqueous and
nonaqueous phase) (<1.0μm). Microspheres of poly lacto gylcolic acid
(PLGA) are prepared for topical ocular delivery.

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5.ADVANCED DRUG DELIVERY SYSTEMS
• Several kinds of viruses including adenovirus, retrovirus,
adeno-associated virus, and herpes simplex 140virus, have
been manipulated for use in gene transfer and gene therapy
applications. The advanced delivery systems such as gene
delivery, SiRNA, stem cells that prolong the contact time of
the dosage form with the surface of the eye and facilitate noninvasive administration.

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Evaluation of ocular drug delivery
system
• Thickness of the film.
• Drug content.
• Irritancy test.
• Percentage moisture loss.
• In vitro drug release.

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ADVANTAGES
• Localized drug delivery is possible.
• Drops are easy to apply and have good patient acceptance.
• Intravitreal , periocular sub-conjuctival injections improve drug absorption
and have no systemic toxicity.
• Micro particles , Nanoparticles, liposomes increase half life of drug.
• ocular inserts increased ocular residence releasing drugs at a slow
and constant rate.

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DISADVANTAGES
• Physical instability of the dosage form.
• Frequent administration reqired with conventional
systems.
• Leaking of entrapped drug.

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CONCLUSION
• Ocular drug delivery systems provide local as well as
systemic delivery of the drugs. The novel advanced
delivery systems offer more protective and effective
means of the therapy for the nearly inaccessible diseases
or syndromes of eyes. Further developments are
preferable which will eliminate the cons of these
available
advanced
delivery
systems
and
acceptable with the regulatory authorities as well.
readily

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REFERENCES
• Text book of pharmaceutical sciences by Remington.
• Novel and controlled drug delivery by N.K Jain.
• Patel Vishal, Agrawal Y.K. CURRENT STATUS AND
ADVANCED APPROACHES IN OCULAR DRUG DELIVERY
SYSTEM, Journal of Global Trends in Pharmaceutical
Sciences, Vol.2, Issue 2, pp -131-148.

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