This document discusses contact lens care and maintenance. It provides an overview of the various products used, including daily cleaners, rinsing solutions, disinfecting solutions, protein removers, rewetting drops, and lens storage cases. It describes how these products work and the proper procedures for their use. Specifically, it explains that daily cleaners use surfactants to remove debris from lenses, while disinfecting solutions kill microorganisms using various active ingredients like hydrogen peroxide, thimerosal, or polyhexanide. Proper cleaning, disinfection, and storage are important to minimize contamination and deposits on contact lenses.
5. Daily Cleaners
• Daily cleaners usually contain surfactants
• and are used to remove most loosely
• bound foreign matter on the lens surface.
• Such matter includes:
– • Cell debris.
– • Mucus.
– • Lipid.
– • Protein.
– • Cosmetics.
– • Micro-organisms.
6. How daily cleaners work
• Surfactant molecules emulsify,
dissolve and/or disperse lipid
globules, debris and other lens
contaminants. This is
accomplished by the surfactant
forming a mono-molecular layer
over the contaminant using the
polar ends of its molecules to
bind the layer to the
contaminant’s surface.
• The ‘coated’ contaminants repel
one another mutually or exhibit
a lowered surface tension.
7. • Viscosity-enhancing agents such as polyvinyl
alcohol or methylcellulose also facilitate cleaning.
• Hypertonicity and abrasiveness are properties
that have been added to enhance the efficacy of
some lens cleaners. Hypertonicity results in
extraction of water from soft lenses which may
help remove some soluble contaminants.
• Polymeric beads in some cleaners have a mildly
abrasive effect on protein and other surface
deposits.
8. • The additional components in a cleaner
include
– Osmolality adjusting agents,
– a buffer system to adjust the pH,
– Chelating agents for removing lens contaminants
and
– viscosity enhancing agents- Viscosity-enhancing
agents such as polyvinyl alcohol or
methylcellulose also facilitate cleaning
9. Procedures for daily cleaners
• Lenses should be cleaned daily after removing
from the eye
– Wash hands thoroughly, soap or oil without
fragrance
– Put the lens in the palm 2-3 drops of daily
cleaners press with to and fro motion 15 sec
• It is important to understand that performing
the cleaning is more important than the brand
or type of cleaner used
10. • Cleaning should be done with:
– All lens types including disposables.
– All care systems, especially multipurpose solution-
based care.
• The mechanical action of rubbing and rinsing
reduces significantly the amount of loose debris
and the number of microorganisms on a lens.
• Rubbing also enhances the efficacy of the
cleaning solution’s surfactant properties
11. Rinsing Solution
• After cleaning, lenses should be rinsed.
• Rinsing performs a variety of functions.
• Buffering agents are included in rinsing solution
formulations so that their pHs approximate that
of tears.
• The pH of normal tears is, on average 7.2, but is
subject to individual variation.
• To enhance the compatibility of solution and tear
pHs at lens insertion, the solution is normally
buffered lightly
12. Rinsing Agent
• Saline
– once-common form of rinsing solution
– Risk of contamination discard in 2 weeks
• Homemade saline has no role in contact lens
care. In the Donzis et al. (1987) study, homemade
saline was contaminated with bacteria and some
preparations were contaminated with
Acanthamoeba sp.
• Meanwhile, preserved saline solution remained
uncontaminated for a period of up to 21 days
after opening.
16. Terminologies
• Sterilization is the killing of all microbial life forms, a
situation impossible to achieve with normal lens care
products and procedures.
• Disinfection is a dynamic process, usually preceded by a
cleaning and rinsing step, intended to kill and/or remove
microbial and viral contaminants from contact lenses.
• Preservation is the killing or inhibition of growth of a select
range of microorganisms to prevent product spoilage
during consumer use.
• The choice of preservative is governed to a large extent by
the resistance of the microbial targets and the sensitivities
of the eye exposed to the preservative via contact lenses or
eye drops
17. Disinfection
• Mode of action:
– Cell membrane disruption
– Enzyme inhibition
– Protein coagulation/ complex formation
18. Disinfection System
• Thermal
– Heat-based disinfection systems
use heat in the range from 70°C
to 125°C to kill or deactivate
living lens contaminants.
– Heat disinfection systems
generally decrease lens life span
and eventually cause lens
discoloration.
• SOFT MATE Barnes Hind
19. • Bausch & Lomb
Thermal Disinfecting
System
• Soft contact lenses are
placed in the lens case
with saline solution and
heated to 70 - 80°C for
10 - 20 minutes.
• The controlled heating
and automatic shut-off
prevents over-heating
and possible shortening
of lens life.
20. Chemical Disinfection
• a wide variety of types exist
• Two type discussed here
– Disinfectant-based solutions (Cold chemical)
• Thimerosal, chlorhexidine Gluconate, BAK, Sorbic acid
– Hydrogen peroxide based solutions (Oxidative)
21. Thimerosal
• A mercurial antibacterial also effective as an
antifungal
• Many Drawbacks
– Cytotoxic activity to corneal epothelium
– Cessation of mitosis cell division
– Delayed hypersensitivity reactions showing
subepihtelial opacities
22. Chlorhexidine Gluconate
• A biguanide antimicrobial) uptake and release
has also been studied because of its historic
use by manufacturers in combination with
thimerosal or other agents to enhance its
effectiveness
• CHG is adsorbed onto RGP lenses (siloxane
acrylates) as a monolayer until they become
saturated and no further uptake occurs
• Concentrations: 0.0025-0.006%
• A tablet form of CHX(0.004%) is under
name of OptimEyes
• Hypersensitivity reactions may occur
23. Benzalkonium Chloride (BAK)
• creates cytotoxic reactions in the corneal epithelium in
a shorter period of time than thimerosal or
chlorhexidine
• BAK’s uptake by rigid gas permeable (silicone acrylate)
lenses has been shown to be one of self-aggregation
whereby the positively charged molecules continue to
bind to the negatively charged surface of the lens until
they reach toxic concentrations.
• BAK release onto the cornea from soft and rigid
contact lenses has been shown to be beyond the
critical limits of safety
24. Sorbic acid
• has antibacterial and limited antifungal
activity. Its concentration in SCLs has not been
shown to cause death of the corneal epithelial
cells
• Causes yellow or brown discoloration of lens
due to its interaction with Amino Acid (lysine)
and tear protein.
25. Benzyl Alcohol
• It is a disinfectant and preservative for RGP and
PMMA lenses
• It is unsuitable for use with soft contact lenses
• It is non-cytogenic and relatively non-sensitizing
• It is a bactericidal and viricidal but ineffective
against Pseudomonas aeruginosa in low
concentrations
• Like other alcohols (isopropyl alcohol,
isopropanol, ethanol), it behaves like a lipid
solvent
26. Chlorbutanol
• it is a chlorinated alcohol preservative with
broad spectrum of action.
• it is however, slow acting against and bacteria
and has a distinctive odour.
• it is effective in acidic pH and used along with
other preservatives
• it is used in a concentration of 0.5 %
27. EDTA
• are not strictly preservatives.
• they are variously described as preservative enhancers,
preservative potentiators and chelating agents
• EDTA’s action removes, by chelation, divalent cations
such as calcium and magnesium ions from solutions
and/or cell walls of gram-negative organisms
• EDTA does not bind to lens materials significantly and
is normally used in combination with other
preservatives.
• it has a synergistic action with BAK, which enhances
the effectiveness of the blended solution
28. Iso-propyl Alcohol
• Used as 1-20% concentration
• Suitable for soft contact lenses
• Benzyl alcohol which is used as disinfectant
for RGP lenses is not suitable for soft lenses
29. Biguanide
• The first biguanide used was chlorhexidine
(CHX)
• Polymeric biguanides include - PHMB,
PAPB. Polyhexanid
30. Biguanide: PHX/PHMB
• Polyhexanide (PHX) properties include:
• Polyhexanide = polyhexamethylene biguanide, PHMB
• Fast acting, broad spectrum antimicrobial.
• Good fungicide.
• Variable virucide .
• Good Gram-negative (e.g . Pseudomonas spp.) biocide.
• Broad range of pHs (4-IO).
• Stable (>2 years).
• Heat stable to > 140°C (autoclavable).
• Odourless, clear, colourless, non-foaming.
• Miscible with water in all proportions.
• Incompatible with chloride, calcium and magnesium ions
31. Polyquad
• Polyquad is the marketing name for a high
molecular weight (polymeric) quaternary
ammonium compound: Poly(quaternium),
polidromium chloride, onamer M
• This type of preservative is used in both rigid and
soft lenses in concentrations of 0.001 – 0.005 %
• Its high molecular weight of 5000 restricts its
entry into lens materials thus minimizing ocular
reactions
32. • Disinfectant/Preservative Sensitivity
– The most common observable sign of this
condition is mild conjunctival redness in both eyes
which affects the exposed nasal and temporal
quadrants as well as the upper and lower bulbar
conjunctiva.
34. Hydrogen Peroxide based solution
• PH 3-4; suitable for all lens type
• Hydrogen peroxide-based disinfection systems
may be either preservative-free or preserved
and can be divided into two main types:
– One-step systems
– Two-step systems
• Hydrogen peroxide disinfection systems are
normally formulated with a 3% peroxide
concentration
35. • For a lens to be wearable following disinfection,
neutralization is required.
• Various neutralization techniques have been designed
by manufacturers to simplify the disinfection and
neutralization steps and thereby lessen the likelihood
of non-compliance or discomfort on insertion.
• Most systems catalytically decompose hydrogen
peroxide into saline and oxygen
• Disinfection in hydrogen peroxide is reasonably
effective in 10 - 15 minutes for bacteria, 1 hour for
fungi and 3-6 hours for acanthamoeba
36. • Advantage of hydrogen peroxide
– Very effective
• Disadvantages:
– If stored for a longer period of time or exposed,
the solution may have already gone oxidation.
• In this case the desired effect is not obtained. And
there is no proper way we can monitor how much
percentage of hydrogen peroxide has undergone
oxidation.
37. Disadvantages (contd…)
• It is not perfectly compatible especially with
high water content, ionic contact lenses in
that it can reversibly alter lens parameters and
water content
• once it is neutralized, a peroxide system has
no antimicrobial power and can sometimes
cause irritation in the eye if not neutralized
properly
38. One-step
• One step procedure is formulated so that the peroxide
disinfection and neutralization are performed during
the recommended time. With tablet-using systems a
delay is applied to the neutralization phase.
• With disc-based systems, no delay is applied to the
neutralization phase. Regardless of which of these
systems is used special vented lens cases are required
to allow the oxygen generated to escape.
• One step systems use either a catalytic (platinum) disc
or a time-delayed catalase tablet.
39. Two-step
• When neutralization is performed as a separate step, the system is
called a two-step system.
– Step 1: Disinfection
– Step 2: Neutralization
• Very early systems ‘neutralized’ peroxide using premeasured
quantities of sodium bicarbonate for a minimum of 10 minutes.
• In fact, the process was not true neutralization and usually took
longer than 10 minutes. Rather, the bicarbonate altered the
solution pH (upwards) to levels at which peroxide was inherently
less stable. The peroxide solution then began to decompose slowly
into water and oxygen.
• With two-step systems it is recommended that lenses are stored
overnight in the peroxide and neutralized immediately before lens
usage.
41. • Be sure to use the special contact lens case that
comes with your hydrogen peroxide contact lens
solution.
• Be sure to leave your contacts in the solution
for at least 6 hours to allow the neutralizing
process to finish.
• For the purpose of neutralization substances like
sodium pyruvate, sodium thiosulphate, sodium
sulphite, catalase and sodium bicarbonate have
been used
42. Protein Remover
• Protein removers, also known erroneously as
enzymatic cleaners, are included in the care systems
for soft contact lenses, and some RGP lenses, that are
not replaced regularly (>1month).
• Not all protein removers are enzyme-based. Those that
are, are usually supplied in tablet form.
• Chemical based systems are usually supplied as ready-
to-use liquids. These cleaners are effective in loosening
tightly bound protein deposits. However, they cannot
be expected to remove all proteins.
• Also marketed in the name of intensive cleaners
43. • Protein treatment is usually done weekly or at a
frequency dependent on the rate of patient
protein deposition.
• Heavy protein depositors, especially ionic high
water material lens wearers, may require an
increased frequency.
• Lenses should be soaked in the remover for 15
minutes to two hours, depending on the type of
protein remover used and rate of protein build-
up. Enzymes used include papain, subtilisin,
pronase and pancreatin.
44. Protein removers
• Papain
– Derived from papaya plant
– Bind to CL materials and can cause sensitivity rxn
– Short soaking time: 15 min
• Pancreatin
– Pig panreas derivative
– Cleaning efficacy similar to papain.
• Subtilisin
– Derived from bacillus bacteria
– Low toxicity: used in food products
– Less specific binding characteristics
– More effective than papain & pancreatin
45. • Enzyme tablets act
as protein
removers by
cleaving the
peptide bonds in
tear proteins
deposited on
contact lens
surfaces
46. Rewetting Eye Drops and Lubricants
• Tear fluid supplements are often used by contact
lens wearers to:
– Promote comfort.
– Overcome the sensation of dryness that can occur
with soft lenses due to insufficient lubrication by the
tear film.
– Rehydrate the lens and flush debris from the surface
of the eye and lens.
– Reduce the deposit-induced friction between the
eyelids and the corneal surface.
– Cushion the lens on the eye.
47. Lens Storage and Cases
• To avoid contamination, the lens case should be
rinsed after every use and the lenses stored in
fresh solution.
• A soiled lens case can be the cause of ocular
irritation when contaminants are transferred to a
contact lens and from the lens into the eye. It can
also be the cause of lens discoloration.
• If a case is heavily contaminated with
microorganisms, it may reduce the efficacy of the
disinfection system by exceeding the disinfectants
capacity to kill the target micro-organisms.
48. • Bacterial contamination of storage cases for both soft and
rigid contact lenses has been reported by a number of
investigators
• Biofilm or glycocalyx formation on the surface of contact lens
storage cases can harbour Pseudomonas aeruginosa and
Serratia marcesens.
• The biofilm is produced by the bacteria themselves. It
protects the host bacterial cells from chemical or
preservative attack and traps nutrient particles and
organisms.
– Human biofilm formed around CL is beneficial for CL adaptation
because it makes surface biocompatible
– Bacterial biofilm is on the other hand is hazardous
• Pseudomonas aeruginosa and Serratia marcesens are also
able to produce their own biofilm in storage cases
49. Care of lens case
• This prevents loss of disinfecting efficacy when fresh
solution is mixed with used solutions.
– Scrub with a toothbrush and detergent weekly. Oil free
soaps or detergents are recommended for this step.
– Rinse with hot water and rub thoroughly with a clean, dry
tissue. Acanthamoeba can be killed at temperatures of
≥70°C. Rubbing will help disrupt the biofilm that may be
forming on the case surfaces.
– Air dry. Keeping the lens case dry will prevent colonization
by micro-organisms such as protozoa that thrive in moist
or wet environments.
– Frequent Replacement of case
50. MPS
• For cleansing, rinsing, disinfecting and storing
CL
• Clean lenses as we do in daily cleaners
• Store in the same solution until use
• With MPS, no other lens care products
required
• Also called no rub solution or all-in-one
solution
51. • Based on results of different microbiological and cleaning
efficacy tests recommended by FDA , manufacturers are allowed
to label their products as:
• Multi-purpose solutions (MPS)
• Multi-purpose disinfecting solutions (MPDS)
• No Rub Required
Stand alone test = soaking only
Regimen test = all steps i.e rub, rinse and soak
52. Stand Alone Test
• The Stand Alone Test evaluates the innate antimicrobial activity of
the CL disinfectant within the recommended disinfection time. With
this procedure, three lots of product are evaluated. In the test, each
lot of product is challenged with a large challenge (106 CFU/ml) of
five different microorganisms
• The microorganisms include
– Gram-negative bacteria (Serratia marcescens and Pseudomonas
aeruginosa),
– Gram-positive bacteria (Staphylococcus aureus),
– yeast (Candida albicans),
– and mold (Fusarium solani).
• The product is sampled for survivors at 25, 50, 75, and 100% of the
disinfection time for bacteria
53. Stand Alone test
• Primary Criteria:
– Reduction not less than 99.9% (3.0 logs) for
bacteria; and reduction not less than 90% for
mould and yeasts within in 100% of the soaking
period recommended by the manufacturer
• Secondary criteria:
– A minimum of 5 log unit reduction for three species
of bacteria and a minimum of 1 log unit reduction
for each bacteria within 100% of the soaking period
recommended by the manufacturer.
– The solution must also show no growth (Stasis) of
two test fungi during the labeled soak time.
54.
55. • The FDA permits contact lens products to be
labeled as contact lens disinfecting solutions if
they meet the primary criteria of the Stand Alone
test for contact lens disinfectants against five
representative challenge micro-organisms.
• This test uses no lenses, no soil and no rubbing or
rinsing steps. Nevertheless, meeting the criteria
of this test is proof of principle to the regulatory
agencies that the product will perform as
indicated during use
56. Regimen test
• The product must kill or remove five logs of
each test organism.
• In contrast to the Stand Alone test, the FDA
Regimen test is carried out with lenses in the
presence of organic soil representing the
components of the tear during consumer use. If
the rubbing step is eliminated, then the product
must be tested to determine effect of soil and
tested by the FDA Regimen test to assure product
efficacy during consumer use.
59. MPS Formulations
• Both PHX and PQ-I adhere to negatively charged
(anionic) sites on hydrogel lens surfaces leading
to lens wettability issues.
• To address these, additional solution excipients
are incorporated as follows:
60. • Chelating agents, buffers or surfactants are
incorporated that either:
• Compete for the charged lens surface sites
(e.g. the Trischem system in AMO's
Complete MPS) or,
• Bind to the charged sites on the
antimicrobial polymer thereby preventing
it from adhering to the lens (e.g. the
citrate buffer system in Alcon's Optifree) .
61. • Bausch & Lomb's RENu MultiPlus product
incorporate Hydranet to aid protein removal but
does not affect lipid removal because their
hydrophobic nature requires a surfactant to
solubilize them (Tonge et al. 2001a )
62. • To address the problems of lipids, manufacturers of
MPSs include high -molecular-weight (e.g. 12,600 or
larger ) nonionic surfactants
• Usually block copolymers of Poly(ethylene oxide )
and poly(propylene oxide) known as poloxamers
(also a trade name - Poloxamer ), a family of
products differentiated by a number (e.g. Poloxamer
407, average molecular weight: 12,500), or
polyethylenepolypropylene glycol, or poloxamines .
• These high-molecular weight surfactants are
reputedly non-irritating because they cannot cross
the corneal glycocalyx readily and stimulate corneal
nerve endings (Tonge et al.2001 ).
63. • CIBA Vision uses the Tri –Klens, combination
(EDTA, a phosphate buffer system, and Poloxamer
407 that targets proteinaceous lens deposits) in
their Solo-care 10 Minute MPS.
• EDTA and the phosphate buffer work together to
break the calcium bridges between protein deposit
and lens (Hydranate) while Poloxamer 407
surfactant dislodges the now 'undocked' protein ,
thereby facilitating its dissolution and removal.
64. • Generally, MPSs contain high molecular weight
surfactants (e.g. poloxamer poloxamines) because
they have a lower potential to cause discomfort by
crossing the corneal glycocalyx and stimulating the
free nerve endings within the cornea.
• Complete Comfort PLUS contains a high molecular
weight surfactant (Christie 1999 )
65. Multipurpose solutions
- RGP lenses
• The principal differences in RGP MPSs is their greater
concentration of disinfectant.
• For example: the soft lens solution ReNu MPS has
0.00005% PHX and EDTA and ReNu Multiplus with
Hydranate has 0.000 1% PHX and EDTA, whereas
Boston Simplicity Multi-Action RGP solution
contains 0.0005% PHX, 0.003% CHX and 0.05% EDTA.
• This is possible because of the lower adsorption and
absorption of disinfectant by RGP materials because of
their non-ionic nature, small pore size and
insignificant water content.
66. Opti-Free Express
(Alcon)
• MPS
• Contains Polyquad (Polyquaternium-1)0.001% as
preservative in addition to Aldox (Myristamidopropyl
Dimethylamine) 0.0005%, an antifungal agent
• Contains surfactant poloxamine and sodium citrate which
interacts with cationic organic molecules dislocating the
bound lysosome
• Sodium citrate also chelates calcium and other metals
• Approved for “no rub” .
• Citrate: remove daily protein deposits, dirt, and shield lenses
against build up
• Sodium Chloride, Boric Acid, Sorbitol, Edetate
Disodium: Maintains pH of lens to closely match natural
tears
67. Solocare (Ciba Vision)
• MPS
• Preservatives /disinfectant –EDTA and polyhexidine .
• FDA approved for both RGP and soft lens.
• Disinfection after 10 min of storage .
68. • The Hydrolock Effect:
•Pro-Vitamin B5: the special moisturizing
ingredient that locks in moisture and prevents lens
dehydration giving comfortable, moist lenses all day
long
•Sorbitol: A moisturizing effect that promotes water
retention and moisture
•With a speedy, 10-second rub and 5-minute soak,
SOLO-Care AQUA can rapidly and effectively care for
the soft contact lenses
•Lenses cleaned in SOLO-care AQUA are fond to keep
up to 90 percent more moisture than lenses cleaned
in other leading lens care products.
69. ReNu Multiplus (B&L)
• MPS
• A sterile, isotonic solution that contains:
• poloxamine,
• diglycine,
• sodium citrate,
• boric acid,
• sodium borate,
• edetate disodium,
• sodium chloride,
• preserved with a triple disinfectant system
(polyaminopropyl biguanide 0.00005%,
polyquaternium 0.00015% and alexidine
0.0002%).
70. Horien Aqua Comfort
• Horien Aqua Comfort Solution cleans,
rinses, disinfects and preserves, and also
moisturizes the lens
• Composition:
• PHMB 0.0001%, 0.05% EDTA, Poloxamer,
Boric Acid, Sodium Chloride, HPMC,
Disodium Hydrogen Phosphate, Sodium
Hyaluronate, Propylene Glycol.
• Supplemented by three ingredients -
Disodium Hydrogen Phosphate, Sodium
Hyaluronate, Propylene Glycol, which
nourishes contact lenses by creating
unique protective layer retaining optimum
moisture level
71. AOSEPT(Ciba Vision)
• A one-bottle, no-rub, hydrogen peroxide-
based lens care solution that cleans, disinfects
and stores all soft contact lenses (including
silicone hydrogel lenses) and rigid gas
permeable lenses.
• Good cleaning agent by isopropyl alcohol.
• 3% H2O2 neutralized by platinum disc
• 6 hours for Disinfection
• Provides triple-action power:
• A built-in cleaner hydrogen peroxide
penetrates the lens to provide deep cleaning
and disinfection.
• Mechanical forces caused by the bubbling
boost surface protein removal.
72. Complete (AMO)
• Multi-Purpose Solution
• Cleans, loosens and removes accumulations of
film, protein, other deposits and debris from soft
(hydrophilic) contact lenses.
• Destroys harmful microorganisms on the surface
of the lenses and also rinses and stores the
lenses.
• A sterile, isotonic, buffered solution, preserved
with polyhexamethylene biguanide (0.0001%), a
phosphate buffer, poloxamer 237, edentate
disodium, sodium chloride, potassium chloride
and purified water.
• Contains no chlorhexidine or thimerosal.
73. Aqua Soft
• A multipurpose solution for soft contact
lenses.
• A sterile, isotonic and aqueous solution
that contains sodium and potassium
chloride, poloxamer, polyhexanide and
sodium phosphate buffer compounds.
74. Purecon Puresoft
• A sterile
buffered
isotonic solution
which contains
purified water,
HPMC, EDTA,
Borax in Sodium
Chloride Base
75. Unique pH(Menicon)
• MPS
• For RGP lens
• EDTA /polyquad as disinfectant
• A sterile, buffered aqueous solution that
removes dirt, protein deposits and debris
from contact lenses
• Adjusts to the eye's natural tear pH to
enhance the wettability and comfort of
rigid gas permeable contact lenses upon
insertion.
• Contents:
• Hydroxypropyl Guar, Polyethylene Glycol,
Poloxamine, Boric Acid, Propylene Glycol,
Polyquaternium-1, Edetate Disodium
76. Boston Simplus
• One-bottle cleaning, disinfecting and conditioning
product that has the added convenience of a built-
in protein remover and an easy-to-use lens care
regimen.
• For cleaning, removing protein, rinsing,
disinfecting, conditioning, storing and cushioning
fluoro-silicone acrylate and silicone acrylate gas
permeable lenses
• A sterile, aqueous, buffered solution that contains
poloxamine, hydroxyalkyl phosphonate, boric acid,
sodium borate, sodium chloride, hydroxypropyl
methyl cellulose, Glucam and preserved with
chlorhexidine gluconate (0.003%),
polyaminopropyl biguanide (0.0005%).
77.
78. Deposits
• Depends upon:
– Water content of the material
– Ionic charges at the surface
– Age of the lens
– Wear time
• High water content and high Ionicity favors
protein deposition (Group IV lysozyme at
the surface)
• Group II Lipid deposits
79. • Silicone Hydrogels lipid deposits due to the
migration of siloxane materials to the surface
– So needs surface treatment
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