ISSN 2249-3875

International Journal of Pharmaceutical Erudition

Review Article
Ocular Inserts: A Rate Controlled Drug Delivery System – A Review
Bade Madhuri *, Gawali Vikas B., Bhalsing Mahesh
*
Abasaheb Kakade College of Pharmacy, Bodhegaon, Shevgaon, Ahmednagar (MH) India

Ocular inserts are sterile preparations, with a thin, multilayered, drug-impregnated, solid or
semisolid consistency devices placed into cul-de-sac or conjunctiva sac. They are usually
made up of polymeric vehicle containing drug. Ocular drug delivery is one of the most
fascinating and challenging tasks facing 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 therapeutic efficacy of an ocular drug can be greatly
improved by prolonging its contact with the corneal surface. Newer ocular drug delivery
systems are being explored to develop extended duration and controlled release strategy.
Some of the newer, sensitive and successful Ocular delivery systems like inserts,
biodegradable polymeric systems, and collagen shields are being developed in order to attain
better ocular bioavailability and sustained action of ocular drugs.
Key Words: Ocular inserts, Controlled release strategy, Rate Controlled drug delivery,
Bioavailability

INTRODUCTION
Ocular inserts are defined as sterile obtain and maintain a therapeutic level at
preparations, with a thin, multilayered, the site of action for prolonged period of
drug-impregnated, solid or semisolid time. The anatomy, physiology and
consistency devices placed into cul-de-sac biochemistry of the eye render this organ
or sac of conjunctiva and whose size and exquisitely impervious to foreign
shape are especially designed for substances. The challenging to the
ophthalmic application. These inserts are formulator is to circumvent the protective
placed in lower fornix and less frequently, barriers of the eye without causing
in upper fornix or on the cornea. They are permanent tissue damage. The
usually made up of polymeric vehicle development of newer, more sensitive
containing drug and are mainly used for diagnostic techniques and therapeutics
topical therapy. agents renders urgency to the development
Ocular drug delivery is one of the most of maximum successful and advanced
fascinating and challenging tasks facing ocular drug delivery systems.
the Pharmaceutical researchers. One of the The therapeutic efficacy of an ocular drug
major barriers of ocular medication is to can be greatly improved by prolonging its
contact with the corneal surface. For
*Address for correspondence
bademadhuri@yahoo.co.in achieving this purpose, viscosity-

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enhancing agents are added to eye drop inserts, biodegradable polymeric systems,
preparations or the drug is formulated in a and collagen shields are being developed
water insoluble ointment formulation to in order to attain better ocular
sustain the duration of intimate drug-eye bioavailability and sustained action of
contact. Unfortunately, these dosage forms ocular drugs.
give only marginally maximum sustained 1. Characteristics of Ocular Inserts:
drug-eye contact than eye drop solutions • Bio stable & Biocompatible with tissue
and do not yield a constant drug of eye
bioavailability. Repeated medications are • Nontoxic & Non carcinogenic
still required throughout the day. • Retrievable & Release at a constant
These practical issues have stimulated the rate.
search for alternative methods for ocular • Non immunogenic & Non mutagenic
drug delivery. Much of the work recently • Good mechanical strength
devoted to ocular inserts, which serves as • Free from drug leakage
the platform for the release of one or more • Easily sterilizable
active substances. It has become clear, • Easy and inexpensive to manufacture
however that the development of an ocular • Applicability to variety of drugs
insert that reliably combines controlled • Non-interference with vision and
release with absence of any irritation to the oxygen permeability
patient, poses a formidable technical
Approach
challenge. Ocular insert is defined as a preparation
In order to overcome the constraints with solid or semisolid consistency, whose
placed by these conventional ocular size and shapes are especially designed for
therapies viz. ophthalmic application (i.e., rod or shield).
• Short residence time They are composed of a polymeric support
• Pulsed dosing of drug. containing or not drug(s), the latter being
• Frequent instillation incorporated as dispersion or a solution in
• Large drainage factors the polymeric support. The inserts can be
Newer ocular drug delivery systems are used for topical therapy. The main
being explored to develop extended objective of the ophthalmic inserts is to
duration and controlled release strategy. increase the contact time between the
Some of the newer, sensitive and preparation and the conjunctival tissue to
successful Ocular delivery systems like ensure a sustained release suited to topical

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or systemic treatment. In comparison with fabrication cost, as well as by the

the traditional ophthalmic preparation i.e., physical/physiological constrains of
eye drops, the solid ophthalmic devices application site.
presents some advantages . 2. Disadvantages of Ocular Inserts:
Advantages of Ocular Inserts: A capital disadvantage of ocular inserts
In comparison with the traditional resides in their ‘solidity’, i.e., in the fact
ophthalmic preparation i.e., eye drops, the that they are felt by the (often
solid ophthalmic devices presents some oversensitive) patients as an extraneous
advantages : body in the eye.
Increasing contact time and thus Their movement around the eye, in rare
improving bioavailability. instances, the simple removal is made
Possibility of providing a prolong drug more difficult by unwanted migration of
release and thus a better efficacy. the inserts to upper fornix.
Reduction of systemic side effects and The occasional inadvertent loss during
thus reduced adverse effects. sleep or while rubbing the eyes.
Reduction of the number of Their interference with vision, and
administrations and thus better patient Difficult placement of the ocular inserts
compliance. (and removal, for insoluble types).
Reduction in systemic absorption Classification of Ocular Inserts:
Possibility of targeting inner ocular A.Insoluble ocular inserts:
tissues through non-corneal The insoluble inserts have been classified
(conjunctival sclera) routes into three groups:-
Possibility of incorporation of various I. Diffusion systems
novel chemicals and technological II. Osmotic systems
approaches such as pro-drug, III.Contact lenses.
mucoadhesives, permeation enhancers, The first two classes include a reservoir in
microparticulate, salts acting as buffers. contact with the inner surface of the rate
Of course not all benefits listed above controller and supplying drug there to. The
can present in single, ideal device. Each reservoir contains a liquid, a gel, a colloid,
type of inserts represents compromise a semisolid, a solid matrix or a carrier-
between desirable properties inherent containing drug homogeneously or
by solid dosage forms and negative heterogeneously dispersed or dissolved
constraints imposed by structure and therein. The reservoir contains a liquid, a
components of insert itself, by gel, a colloid, a semisolid, a solid matrix or
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a carrier-containing drug. The third class During the first hour the system releases
including the contact lenses. The pilocarpine at a rate, which is three times
insolubility of these devices is their main higher than the programmed rate i.e. 20
disadvantages, since they have to be microgram per hour. Ocular inserts of this
removed after use. type have been reported for various other
I. Diffusion controlled ocular inserts ophthalmic therapeutic agents like
The diffusion systems are compares of a carbonic anhydrase inhibitors, epinephrine,
central reservoir of drug enclosed in anesthetics, antibiotics, anti inflammatory
specially designed semi permeable or steroids etc.
micro porous membranes, which allow the Central reservoir Glycerin, ethylene
drug to diffuse the reservoir at a precisely glycol, propylene glycol, water, methyl
determined rate. The drug release from cellulose mixed with water, sodium
such a system is controlled by the alginate, poly (vinylpyrrolidone), poly ox
lachrymal fluid permeating through the ethylene Stearate Micropores Membrane
membrane until a sufficient internal Polycarbonates, polyvinyl chloride,
pressure is reached to drive the drug out of polysulfones, cellulose esters, crosslinked
the reservoir. The drug delivery rate is poly (ethyl oxide), cross-linked
controlled by diffusion through the polyvinylpyrrolidone, and cross-linked
membrane, which one can be controlled. polyvinyl alcohol
This consists of medicated core prepared II. Osmotic Inserts:
out of a hydro gel polymer like alginates, The osmotic inserts are generally
sandwiched between two sheets of compared of a central part surrounded by a
transparent, lipophillic, rate controlling peripheral part. The central part can be
polymer like ethylene /vinyl acetate composed of a single reservoir or of two
copolymer membrane designed to the distinct compartments. In first case, it is
required geometry suitable for insertion in composed of a drug with or without an
to the cul-de-sac. When the device is additional osmotic solute dispersed
placed in a cul-de-sac the drug molecule through a polymeric matrix, so that the
penetrates through the rate controlling drug is surrounded by the polymer as
membranes at zero order rate process as discrete small deposits. In the second case,
defined : the drug and the osmotic solutes are placed
Dq/dt=dpkm (cr-ct)/dm. in two separate compartments, the drug
A typical In vivo release rate profile of reservoir being surrounded by an elastic
pilocarpine from the ocusert pilo-20. impermeable membrane and the osmotic
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solute reservoir by a semi permeable Carbohydrates – Sorbitol, mannitol,

membrane. The second peripheral part of glucose and sucrose.
these osmotic inserts comprises in all cases III. Contact lenses:
a covering film made of an insoluble semi These are shaped structure made up of a
permeable polymer. covalently crosslinked hydrophilic or
The tear fluid diffuse into peripheral hydrophobic polymer that forms a three-
deposits through the semi permeable dimensional network or matrix capable of
polymeric membrane wets them and retaining water, aqueous solution or solid
induces their dissolution. The solubilized components8. When a hydrophilic contact
deposits generate a hydrostatic pressure lens is soaked in a drug solution, it absorbs
against the polymer matrix causing its the drug, but does not give a delivery as
rupture under the form of apertures. Drug precise as that provided by other non-
is then released through these apertures soluble ophthalmic systems. The drug
from the deposits near the surface of the release from such a system is generally
device which is against the eye, by the sole very rapid at the beginning and then
hydrostatic pressure. This corresponds to declines exponentially with time. The
the osmotic part characterized by zero release rate can be decreased by
order drug release profile. incorporating the drug homogeneously
Water permeable matrix Ethylene - during the manufacture or by adding a
vinyl esters copolymers, Divers- hydrophobic component. Contact lenses
plasticized polyvinyl chloride (PVC), have certainly good prospects as
polyethylene,cross-linked (PVP)poly vinyl ophthalmic drug delivery systems.
pyrrolidone. This type of device substantially prolongs
Semi permeable membrane Cellulose the drug /eye contact time and thus
acetate derivatives, Divers – Ethyl vinyl increases bioavailability. Some of the
acetate(EVA), polyesters of acrylic and polymers that could be used for preparing
methacrylic acids (Eudragit ®). the device are 2-hydroxyethylmethacry-
Osmotic Agents late, vinyl pyrrolidone acrylic co polymer
Inorganic – magnesium sulfate, sodium etc. When contact lenses are used as
chloride,potassium phosphate dibasic device, the lenses are presoaked in the
sodium carbonateand sodium sulfate. drug solution for sufficient time for
Organic- calcium lactate, magnesium equibrilliation and are then inserted just
succinateand tartaric acid. like a contact lenses

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B. Soluble ocular inserts: D – Diffusion coefficient of the ocuserts

Soluble inserts correspond to the oldest membrane.
class of ophthalmic inserts. They offer the Since all the terms on the right hand side
great advantage of being entirely soluble of the above equation are constant, so is
so that they do not need to be removed the release rate of the device.
from their site of application thus, limiting The soluble insert made of cellulose
the interventions to insertion only. derivatives can be sterilized by exposure to
Types gamma radiation without the cellulose
a) Based on natural polymers e.g. components being altered.
collagen. Soluble synthetic Polymers
b) Based on synthetic or semi synthetic Cellulose derivatives – Hydroxypropyl
polymers. cellulose, methylcellulose, hydroxyethyl
The therapeutic agent is preferably cellulose and hydroxypropyl cellulose.
absorbed by soaking the insert in a Divers – Polyvinyl alcohol, ethylene vinyl
solution containing the drug, drying and acetate copolymer.
rehydrating it before use on the eye. The Additives Plastisizer – Polyethylene
amount of drug loaded will depend upon glycol, glycerin, propylene glycol
the amount of binding agent, upon the Enteric coated polymer – Cellulose acetate
concentration of the drug solution into phthalate,
which the composite is soaked, as well as hydroxypropyl methylcellulose phthalate.
the duration of the soaking Complexing agent – Polyvinyl
The release of the drug from such a system pyrrolidone.
is by penetration of tears into the insert Bioadhesives – Polyacrylic acids.
which induces release of the drug by C. Bioerodible ocular inserts:
diffusion and forms a gel layer around the This type of device is fabricated from bio-
core of the insert, this external gelification erodible or bio- degradable polymer of
induces the further release, but is still hydro gel or non hydro gel type. The
controlled by diffusion. The release rate, mechanism of drug release in this system
J, derived from Fick’s law yields the is dependent on rate of erosion or rate of
following expression degradation. Several erodible type of
When A - Surface area of the membrane. ocuserts have been prepared using polymer
K – Diffusion coefficient of the drug like carboxymethyl cellulose, poly vinyl
L – Membrane thickness alcohol, collagen etc. containing drug like
Cs – Drug solubility in water pilocarpine, gentamicin etc in the form of
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disc and wafers. Some of the products are -15 min. the film
also marketed recently as, is turn into viscous polymer mass, there
Lacrisert after in 30-60 min it becomes a polymer
Soluble ocular drug insert, (SODI) solution.
Ocular therapeutic system or Advantages:
(minidisk) Single SODI application has been reported
Corneal collagen shield to replace 4-12 drops instillation or 3-6
• LACRISERT : applications of ointment for treatment of
It is sterile rod shaped device made of glaucoma & trachoma.
hydroxypropyl cellulose without any • MINIDISC: (Ocular Therapeutic System)
preservative. i.e. used for the treatment Consist of countered disc with a convex
of dry eye syndrome. front & concave back surface in contact
It weighs 5 mg & measures 1.27 mm in with eyeball.
diameter with a length of 3.5 mm. It is like a miniature contact lenses with
It is inserted into the inferior fornix a diameter of 4-5mm.
where it imbibes water from The major component of it is silicone
conjunctiva and forms a hydrophilic based prepolymer.
film which stabilizes the tear film and The OTS can be hydrophilic or
hydrates & lubricates the cornea. hydrophobic to permit extended release
Day long relief from dry eye syndrome of both water soluble and insoluble
has been reported from a single insert drugs.
placed in the eye early in the morning. • Corneal Collagen Shield:
Advantages :- Prepared by molding collagen mixed with
Replacement of 4 times an hr regimen by the drug into a contact lens configuration
once or twice daily regimen is the benefit is dehydrated and sterilized by gamma
achieved by this dosage forms. radiation and packed. Drugs like
• SODI:(Soluble Ocular Drug Inserts) antibiotics, steroids have been reported
(Bloomfield, 1978)
The biodegradable inserts are composed of
oval shaped Weighing 15-16 mg homogeneous dispersion of a drug
- included or not into a hydrophobic coating
de-sac where wetted by tear film , it soften which is substantially impermeable to the
in 10-15 seconds and assumes the curved drug. They are made of the so-called
configuration of globe. biodegradable polymers. Successful
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biodegradable materials for ophthalmic content was calculate using the following
use are the poly (orthoesters) and poly formula:
(orthocarbonates). The release of the drug Mg of drug in one patch= As X Cr
from such a system is the consequence of Ar
the contact of the device with the tear fluid Where:
inducing a superficial diversion of the As =Absorbance of sample solution.
matrix. Ar =Absorbance of standard solution.
Evaluation of Ocular Inserts: Cr =Concentration of drug in Standard

1. Film thickness solution.

2. Content uniformity Same procedure is adopts for all the
3. Uniformity of Weight batches of cast films in triplicates and
4. Percentage moisture absorption mean drug content and standard deviation
5. Percentage moisture loss
of variance are calculate.
6. In-vitro drug release
3. Uniformity of Weight:
7. In-vivo drug release
8. Accelerated stability studies. The weight variation test is carried out by
9. Compatibility study. weighing three patches cut from different
places of same formulation and their
1. Thickness of Film:
individual weights are determine by using
Film thickness is measured by using dial
the digital balance. The mean value is
caliper at different points and the mean
calculate. The standard deviation of
value was calculated .Reading were taken
weight variation is compute from the mean
over an circular film of area of 38.5 mm
value.
square. The standard deviation in thickness
4. Percentage moisture absorption: The
was computed from the mean value.
percentage moisture absorption test is
2. Drug Content Uniformity:
carried out to check physical stability or
To check the uniformity of the drug in the
integrity of ocular inserts. Ocular inserts
cast film inserts are cut at different places
are weigh and place in a desiccators
in the cast films and each film is place in
containing 100 ml of saturated solution of
vials containing 5 ml of pH 7.4 phosphate
aluminum chloride and 79.5% humidity is
buffer and shaken to extract the drug from
maintain. After three days the ocular
patch. 1 ml from above resulting solution
inserts are taken out and reweigh. The
is taken and dilute. The solution is
percentage moisture absorption is calculate
analyzed by spectrophotometer using pH
using the formula
7.4 phosphate buffer as blank. The drug
Percentage moisture absorption =
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Final weight – Initial weight donor compartment. The entire surface of

X 100 the membrane is in contact with reservoir
Initial weight
compartment, which contains 25ml of pH
5. Percentage Moisture Loss:
7.4 phosphate buffers and stirs
The percentage moisture loss is carries out
continuously using a magnetic stirrer.
to check integrity of the film at dry
Samples of 1ml are withdrawn from the
condition. Ocular inserts are weighing and
receptor compartment at periodic intervals
keep in a desiccators containing anhydrous
and replace with equal volume of distilled
calcium chloride. After 3 days, the ocular
water. The drug content is analyze at 246
inserts are taken out and reweigh, the
nm against reference standard using pH
percentage moisture loss is calculate using
7.4 phosphate buffer as blank on a
the formula Percentage moisture loss =
UV/visible spectrophotometer.
Initial weight – Final weight 7. In-vivo Drug Release Rate Study:
X 100
Initial weight The inserts are sterilized by using UV
6. In-vitro drug Release: radiation before in-vivo study. Inserts are
To simulate the actual physiological taken in a Petri dish along with 100 mg of
conditions prevailing in the eye an in-vitro pure drug, which are spread to a thin layer.
dissolution is use in the present work. This Petri dish along with polyethylene
In-vitro release studies are carried out bags and forceps are place in UV
using bi-chamber donor-receiver sterilization chamber (hood).
compartment model design using The inserts and other materials are
commercial semi-permeable membrane of exposing to UV radiation for one hour.
transparent and regenerated cellulose type After sterilization, inserts are transferee
(sigma dialysis membrane). It is tie at one into polyethylene bag with the help of
end of the open cylinder, which acts as the forceps inside the sterilization chamber
donor compartment. The ocular insert is itself. The pure drugs which are sterilized
place inside the donor compartment. The along with inserts are analyzing for
semi permeable membrane is use to potency by UV spectrophotometer after
simulate ocular in vivo condition like suitable dilution with pH 7.4 phosphate
corneal epithelial barrier in order to buffer.
simulate the tear volume, 0.7 m1 of The male albino rabbits, weigh between
distilled water is place and maintain at the 2.5-3.0 kg are require for the experiment.
same level through out the study in the The animals are house on individual cages
and customized to laboratory conditions
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for 1 day. Receive free access to food and content of each individual film using the
water. The ocular inserts containing drug drug content uniformity procedure.
are taken for in-vivo study which are 8. Polymer Systems in Ocular Inserts:
previously sterilize on the day of the The use of solid ophthalmic devices will
experiment and are place into the lower certainly increase owing to the
conjunctivas cul-de-sac. The inserts are development of new polymers, the
inserting into 7 eyes at same time and each emergence of new drugs having short
one eye of seven rabbits is serving as biological half lives or systemic side
control. effects and the need to improve the
Ocular inserts are removing carefully at 2, efficacy of ophthalmic treatment by
4, 6, 8, 10, 12 and 24 hours and analyze ensuring an effective drug concentration in
for drug content as dilution mention in the eye over an extended period of time.
drug content uniformity. The drug Polymers used in ocular inserts can be of
remaining is subtracted from the initial natural, synthetic or semi synthetic in
drug content of inserts which will give the nature. Further, they can be either water
amount of drug release in the rabbit eye. soluble polymers with linear chains or
Observation for any fall out of the inserts water insoluble polymers joined by cross
is also recording throughout the linking agents. Most commonly used
experiment. After one week of wash polymer groups include nonionic polymer
period the experiment is repeating for two such as hydroxypropylmethylcellulose
times as before. (HPMC); polycationics such as chitosan,
8. Accelerated Stability Studies: DEAE-dextran and polyanionics like
The accelerated stability studies are carries polyacrylic acid (PAA) derivatives e.g.
out to predict the breakdown that may carbopols, polycarbophils, carboxy-
occur over prolong periods of storage at methylcellulose.
normal shelf condition.The films of the Earlier sustained release ocular dosage
formulation are taken in a separate Petri form included lamellae or disks of
dish and are keep at three different glycerinated gelatin and sterile drug
temperatures 400C, 500C and 600C and impregnated paper strip. The aqueous tear
the period for break down or degradation fluids dissolve the lamella and the drug is
of the ocular inserts is check. When ocular released for absorption.
inserts show degradation the time in days A. Cellulose polymers:
is note and subject to determine the drug Cellulosic polymers such as methyl
cellulose; hydroxyethylcellulose (HEC);
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hydroxypropylmethylcellulose (HPMC); epithelial toxicity lead to use of PVA as a

hydroxypropylcellulose(HPC) were drug delivery vehicle and artificial tear
introduced as viscolizers into artificial tear preparation. Polyvinylalcohol (PVA) has
preparations to retard canalicular drainage been used as a carrier to formulate
and improve contact time. All cellulose- polymeric inserts and were found to
ethers impart viscosity to the solution, enhance bio-availability in comparison to
have wetting properties and increase the solutions
contact time by virtue of film forming C. Poly (ethylene oxide) (PEO):
properties. Poly Ethylene Oxide(PEO) exhibits good
Drug release was found to be better in compressibility and thus is easy for the
terms of extent and amount.Controlled manufacturing of matrix tablets. In contact
release has been observed with various with an aqueous medium, poly(ethylene
beta-blockers from HPM inserts with oxide) hydrates and gels superficially, the
improved ocular bioavailability and polyether chains of PEO forming strong
reduced toxicity and dosing frequency. hydrogen bonds with water. Drug release
HPC, HPMC, PVP and PVA were also from poly(ethylene oxide) matrices is
used in different ratios to prepare the controlled by polymer swelling and
ocular films with the objective to reduce erosion, or drug diffusion through the gel,
the frequency of drug administration, or by both processes. Various release
patient compliance, controlled drug release patterns can be achieved depending on the
and greater therapeutic efficacy for ocular poly(ethylene oxide) molecular mass and
infections such as conjunctivitis, keratitis, physicochemical properties of the drug.
kerato-conjunctivitis and corneal ulcers. Good mucoadhesive properties and lack of
B. Polyvinyl Alcohol (PVA): irritancy to the rabbit eye has been
Alginic acid and derivatives PVA was reported. It points that this polymer can be
introduced into ophthalmic preparations an interesting candidate material for
and reported to have a superior corneal controlled release erodible ocular inserts.
contact time. PVA lowers the surface D. Pluronics, Poloxamer F127
tension of water reducing interfacial Sustained drug delivery can also be
tension at an oil/water interface and achieved by use of a polymer that changes
enhances tear film stability. This film- from solution to gel at the temperature of
forming property together with ease of the eye (33 to 34o C). An example of this
sterlisation, compatibility with a range of type of polymer is poloxamer F127, which
ophthalmic drugs and an apparent lack of consists of linked polyoxyethylene and
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polyoxypropylene units. At room stability and drug release features by

temperature, the poloxamer remains as a topical administration in the rabbit eye and
solution. When the solution is instilled was compared with an aqueous solution of
onto the eye surface, the elevated the same drug.
temperature causes the solution to become G. Poly(Lactic Acid) /Poly ( Glycolic
a gel, thereby prolonging its contact time Acid )
with the ocular surface. Polymers such as poly (lactic acid) or poly
E. Collagen (glycolic acid) undergo hydrolytic
Collagen is widely used for biomedical degradation in the body and become
applications. It accounts for about 25 % of monomers of lactic acid or glycolic acid.
the total body protein in mammals and is These monomers can be metabolized and
the major protein of connective tissue, eliminated from the tissues. It is possible
cartilage and bone. Importantly, the to incorporate drugs in the matrix of these
secondary and tertiary structures of polymers. The polymer containing the
human, porcine, and bovine collagen are drug releases the drug for a sustained
very similar, making it possible to use period and undergoes degradation
animal-sourced collagen in the human simultaneously. These polymers have been
body. Collagen shields are designed to be used as materials of absorbable surgical
sterile, disposable, temporary bandage sutures for many years and proved to be
lenses that conform to the shape of the eye safe and biocompatible. Feasibility of
and protect the cornea. Their dissolution delivering drugs to the retina and vitreous
time on cornea ranges from 12-17 hrs and as well as the subconjunctival space using
is controlled by varying degree of cross- the microspheres of biodegradable
link of the polymer. polymers has been reported.
F. Eudragit H. Alginate and derivatives
The polymer system avoids of any irritant Alginate is a linear co-polysaccharide
effect on cornea, iris and conjunctiva up to isolated from brown seaweeds and certain
24 h after application and seems to be a bacteria. Chemically it is a (1-4)-linked
suitable inert carrier for ophthalmic drug. block copolymer of â-D-mannuronate (M)
Similarly, In another study, Eudragit and its C-5 epimer R-L-guluronate (G),
RL100 polymer nanoparticle system with residues arranged in homopolymeric
loaded with cloricromene polymer matrix sequences of both types and in regions
was prepared and characterized on the which approximate to the disaccharide
basis of physicochemical properties, repeating structure (MG) Commercially
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alginate is widely used as a gelling agent sodium fluorescent, lissamine green

not only in foods but also in other and rose Bengal)
industries such as pharmaceutical, e) Soft contact lenses, implants, flexible
biomedical, and personal care). As it is coils and cotton pledgets (Drug
easy to prepare alginate ionotropic gels at presoaked hydrogel type, polymeric
mild conditions, it is possible to entrap gels)
drugs and living cells in alginate gels, f) Phase Transition systems (in-situ gel
which allow a wide application of alginate formation system: ion- activated based,
as scaffolds for tissue engineering, drug pH changed based, temperature change
delivery systems, and cell encapsulation based).
and transplantation. Drug release from g) Nanoparticles (Microspheres,
such matrices may be controlled by nanosuspension, Amphiphilogels,
polymer swelling or erosion or drug Niosomes, Liposomes, Dendrimers and
diffusion in hydrated gel or by these Quantom dots)
processes all together. All these properties h) Ocular Iontophoresis and pumps
and applications are ultimately dependent i) Chemical delivery systems vesicular
on the molecular architecture and gelling systems
mechanism. Recently alginate-chitosan Utilization of the principal of controlled
ocular inserts has been studied as an release as embodied by ocular inserts
efficient means of delivering therefore offers an attractive alternative
antibiotics(gatifloxacin). approach to the difficult problem of
Recent Trends: prolonging pre-corneal drug residence
The following recent trends are in time.
existence: SUMMARY:
a) Membrane-bound ocular inserts In summary the ideal ocular inserts as a
(biodegradable and non-biodegradable) therapeutic system should be bio stable,
b) Mucoadhesive dosage forms (ocular biocompatible with minimal tissue-implant
films or sheath, ophthaCoil, polymer interaction, stable, nontoxic, non
rods, HEMA hydrogel, Dispersion, carcinogenic, retrievable and should
polysulfone capillary fiber) release the drug at a constant programmed
c) Collagen shields, cyclodextrine based rate for a predetermined duration of
system, ophthalmic rods. medication. As ocular inserts release the
d) Filter paper strips (drug-impregnated drug for prolong period, so it reduces the
filter paper strips for staining agent- no. of administrations and increases
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patient complaience. 2000;37(9): 400-406.

The concept of ocular inserts as a drug 4. Chatterjee, C.C., Special senses, in:
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