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The Pharmaceutical Journal 235
Continuing professional development
Care and advice for
contact lens wearers
It is believed that the idea of the contact lens came from Leonardo da Vinci and it
took over 300 years before the concept was realised, in the form of a piece of blown
glass that covered the whole white of the eye. Corneal contact lenses became
available in 1936. By 2008, contact lenses were worn by around 3.5 million people
in the UK. Marvyn Elton discusses salient points for pharmacists
Marvyn Elton
Most people wear contact lenses for their
corrective function (eg, for myopia,
hypermetropia or astigmatism) — lenses
works by refracting light rays onto the
retina — but the wearing of lenses for
cosmetic purposes is becoming increasingly
popular. Contact lenses lie on the cornea (see
Panel 1, p236) and there are two main types:
rigid gas permeable and soft.
Types of contact lens
Before the late 1970s, people wore contact
lenses made of Perspex (polymethylmethacrylate or PMMA). These were the so-called
hard lenses. When more modern materials
(fluorocarbon or fluorosilicate materials)
became available, the lenses were described as
“rigid gas permeable” (RGP).
RGP lenses do not fold and are typically
smaller than the cornea, at around 9.0 to
9.6mm. Their material allows oxygen to
diffuse through to the cornea. RGP lenses also
move on the cornea and this allows the tear
film to move. RGP lenses are useful if a
person has a high prescription because thicker
lenses can be used with relatively little danger
to eye health. They also allow the best vision to
be attained in conditions such as keratoconus
(where the shape of the cornea is distorted)
and can have a two to three year lifespan.
Soft lenses are larger in diameter (about
14mm) than RGP lenses and completely
cover the cornea so that the edge of the lens
can be seen on the white of the eye (sclera).
This type of lens is most commonly used
because it is generally comfortable straight
away and the fitting is easier and quicker.
Soft lenses fold easily. They are hydrogels
containing between 38 and 74 per cent water.
The higher the water content, the softer and
more comfortable the lens. High water content
also results in greater oxygen permeability
through the lens, so the healthier the lens is for
the cornea. However, lenses with a higher
water content have shorter lifespans and are
more fragile.
Most soft contact lens wearers wear daily,
two-weekly or monthly disposable lenses
(yearly lenses are becoming obsolete). Daily
disposables are convenient because no
cleaning or disinfection is required but they
are very thin and are not as easy to handle as a
monthly disposable lens, which contains more
water so is thicker (which also tends to result
in better vision and more comfort).
A few monthly disposables are “extended
wear”. They are made from silicone hydrogel
and marketed for 30-day wear, 24 hours a day,
including during sleep. These lenses feel
greasy and, in my opinion, the visual acuity is
not as good as with the conventional monthly
disposables. Extended wear soft lenses first
became available in the 1980s but they were
linked to increasing rates of corneal infection
and withdrawn. In 2001, silicone hydrogel
extended wear lenses became available. It was
hoped that there would be a reduction in the
level of corneal infection compared with the
older extended wear lenses but this has not
been the case. Two studies carried out in
Australia and New Zealand and one casecontrol study from Moorfields Eye Hospital,
London, demonstrated no difference in the
risk of corneal infection between the older and
the newer extended wear lenses and indicated
an increased risk of infection with overnight
wear.1 (I do not fit 24 hour soft lenses because
I am worried about corneal vascularisation
and infection — see later.)
Cleaning and disinfecting
Most contact lenses require daily cleaning and
disinfection to remove bacteria and deposits,
such as protein and lipids, which can decrease
visual acuity, damage the lens and pose a risk
to eye health. Cleaning contact lenses used to
be a process that required a number of steps
and a number of products, such as a cleaner, a
disinfectant, a product to neutralise the
disinfectant and a protein remover. This
complicated regimen, which could be difficult
to follow correctly, has now been replaced
with simpler one- or two-step systems.
Contact lens solutions are classed as medical
devices and all products meeting EU
standards will bear a CE mark.
RGP lenses
Most RGP cleaning regimens involve a
cleaning solution containing a surfactant, and
a conditioning and disinfecting solution.
Conditioning and disinfecting solutions
contain ingredients such as
polyhexamethylene biguanide (PHMB; also
known as polyhexanide, polyaminopropyl
biguanide and Dymed). PHMB is a broad
spectrum antibacterial. It is bacteriostatic at
low concentrations but is rapidly bactericidal
at higher concentrations. It kills bacteria by
causing an irreversible loss of essential cellular
Reflect
Plan
Evaluate
Act
REFLECT
1 What is the treatment for Pseudomonas
aeruginosa infection of the cornea?
2 What types of contact lens solutions are
available?
3 Can you list three possible drug-contact
lens interactions?
Before reading on, think about how this article
may help you to do your job better.
components as a direct consequence of
cytoplasmic membrane damage. Before
inclusion in contact lens products, PHMB was
used in the food, brewing and dairy industry.
It was also used as a swimming pool
disinfectant. PHMB is a long-chain polymer
(molecular weight 1,300 compared with the
359 of chlorhexidine).
The RGP lens is removed from the eye
and placed in the palm of the hand. A few
drops of cleaning solution are then placed in
the palm and the lens is rubbed for about 30
seconds to help the cleaning process.
The contact lens case is then filled with the
conditioning and disinfecting solution and the
lens is stored in the case for at least six hours
The author
Marvyn Elton, MCOptom, MRPharmS, is an
optometrist practising in London and Essex
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(usually overnight). After disinfection, the
wearer rinses the lenses with the conditioning
and disinfecting solution before putting them
in. The solution in the contact lens case should
be thrown away and the case left to air dry.
It is important to stress that conditioning
and disinfecting solutions must be used after
cleaning because there have been instances
where people have cleaned an RGP lens and
put it straight into the eye, resulting in a
corneal abrasion and pain. In such cases, the
eye should be washed out with 0.9 per cent
saline or water, and a visit paid to an
optometrist.
Soft lenses
Soft contact lenses that are reworn should be
cleaned daily. Conventional monthly
disposables are generally not old enough for
deposits to build up but bacteria must be
removed. There are two main types of
cleaning and disinfecting product: hydrogen
peroxide based and multipurpose. When
recommending a solution an optometrist will
consider the patient’s history, the lens to be
worn and the likelihood of patient compliance.
Teenagers, for example, can be lax with
cleaning and disinfecting steps so a
multipurpose solution might be preferred.
Extended wear lenses do not require cleaning
or disinfecting but if wearers wish to do so soft
lens solutions can be used.
Hydrogen peroxide The antimicrobial
properties of hydrogen peroxide (H2O2) have
been well known since its discovery in 1818. A
3 per cent solution was introduced as a
method of disinfection for soft contact lenses
in the early 1970s (as an alternative to boiling)
and this is still considered to be the most
effective disinfecting agent for soft contact
lenses because it is able to kill large numbers
of microorganisms quickly, including
pseudomonas and acanthamoebae.2
However, the peroxide must be neutralised
before the lenses can be worn (a neutralising
tablet is placed in the contact lens container,
producing water and oxygen). Forgetting to
neutralise the peroxide is a danger and, along
with the inconvenience of neutralisation, has
reduced the use of peroxide systems.
Multipurpose solutions Most soft lens
wearers now use a single solution, which both
cleans and disinfects. The lens is cleaned in
the same way as an RGP (rubbing has been
shown greatly to reduce the bacterial
contamination). Some multipurpose solutions
with a “no rub” feature are now available, but
I still advise the soft lens wearer to rub both
sides of the contact lens when cleaning.
The contact lens case is filled with the
solution and the lenses placed in it for
overnight disinfection (or for a minimum of
four hours). When the lenses are removed
from the case they can be rinsed with the
solution and worn.
Multipurpose solutions generally contain:
• A cleaning agent (a surfactant, such as
poloxamer, tyloxapol or poloxamine, to stop
protein and bacteria adhering to lenses)
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PANEL 1: ANATOMY OF THE CORNEA
The cornea is at the front of
the eye. It is about 12mm in
diameter and covers the iris. A
healthy cornea is transparent
and convex. The cornea is the
main structure for bending the
light rays to a focus on the
retina, contributing about 70
per cent of the refracting
power of the eye.
Average corneal thickness
is 550μm. The cornea consists
of five layers. The outermost
layer, as with all tissues, is the
Light micrograph of outer corneal layers (Herve Conge ISM/SPL)
epithelium. This is usually
between 70 and 100μm thick.
Underneath the epithelium is Bowman’s membrane. Below this is the stroma, which is the thickest
corneal layer, and under this is Descemet’s membrane. The innermost layer is the endothelium.
This is in direct contact with the aqueous fluid in the eye and continually pumps out fluid from the
cornea, maintaining corneal transparency.
The cornea is rich with nerve fibres (so corneal damage or infection can be extremely painful).
Tear film keeps the cornea (and the conjunctiva) moist and this is necessary for corneal integrity
and health.
• A disinfectant
• A moisturising or conditioning agent, which
adheres to the lens surface (“wetting”) thus
making it more comfortable to wear
• Buffers and preservatives (solution discard
dates can range between two and six months
after opening)
ISO/DIS 14729, the standard for the
antimicrobial efficacy of soft lens care
products, requires the solutions to
demonstrate the required log reduction
against three bacteria and two fungi. The
primary standard for disinfection requires a 1
million organisms/ml challenge (6 log units)
and for the organisms to be killed to the
following levels:
• Bacteria 99.9 per cent (3 log) reduction
within the stated soaking time for
Staphylococcus aureus, Pseudomonas
aeruginosa and Serratia marcescens
• Fungi 90 per cent (1 log) reduction within
the stated soaking time for Candida albicans
and Fusarium solani
Common disinfectants used in
multipurpose solutions include PHMB (eg,
Complete Multi Purpose, ReNu) and
polyquad. PHMB is effective at
concentrations of 0.00003–0.0001 per cent
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and at such low levels the risk of adverse
ocular reactions is minimised. Polyquad (also
called polyquaternium-1) has a molecular
weight of 5,000 so tends not to diffuse into the
lens matrix. This minimises hypersensitivity
reactions.3 Polyquad is a less potent
antimicrobial than PHMB so is used in higher
concentrations (0.001–0.01 per cent). It
performs relatively poorly against fungi and
acanthamoebae. (In Opti-Free Express
solution, this problem is addressed by the
addition of myristamidipropyl dimethylamine
[MAPD]).
Water
Tap water must never be used in lens cleaning
regimens, storage or in contact lens cases. This
is because it contains sight-threatening microorganisms, such as acanthamoebae. Contact
lens cases should be rinsed out with contact
lens solutions and not tap water. Furthermore,
I would not recommend wearing contact
lenses in the shower or during swimming.
Swimming while wearing swimming goggles
over the contact lenses may be acceptable.
Prescription swimming goggles are available.
Switching solutions
With so many apparently similar products
available, consumers may wish to switch
between products. It is my opinion that, in
general, there should be no problem with
changing to another multipurpose solution
but pharmacists selling these products should
advise the person to ensure that he or she
complies with the instructions for use on the
pack. It is worth noting, however, that the
College of Optometrists advises the public not
to switch solutions unless advised by their
optometrist. Different solutions do contain
different ingredients and at varying
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Continuing professional development
Corneal vascularisation
Figure 1: small corneal abrasion (Marvyn Elton)
Figure 2: mild acanthamoeba keratitis (Karl
Southerton, Western Eye Hospital)
concentrations and some patients may find a
particular solution more compatible with their
eyes than others. Moreover, some solutions
have been found to stain certain lens
materials.3
The ideal contact lens solution would kill
all pathogens that can infect the eye and
effectively remove deposits, and be non-toxic,
easy to use and affordable.
Eye health
Contact lens wearers are at increased risk of
eye infections and other ocular problems and
pharmacists must be aware of this. If a lens
wearer complains of an uncomfortable or
painful eye, or the eye is red, or both, lenses
must not be worn until symptoms resolve.
Corneal abrasions and erosions
If, when putting a lens in the eye or taking it
out, the wearer’s fingernail or edge of an RGP
lens accidently catches the cornea, this can
cause a corneal abrasion (see Figure 1).
Corneal abrasions are usually painful and
can take a few days to heal. Once a person has
had a corneal abrasion, they are at greater risk
of recurrent corneal erosions. These erosions
typically cause eye pain on waking in the
morning (when we sleep the eye becomes
drier and on opening the eyes, the eyelid pulls
on the cornea causing an erosion and giving
rise to severe pain).
Optometrists can assess corneal
disturbances with fluorescein, an orange dye
that glows green under blue light (see Figure
1). I usually treat the pain of a corneal
abrasion with 1 per cent cyclopentolate eyedrops to relax the iris and prevent iris spasm
in response to light. The patient can also be
given single use drops (eg, Minims) to use
two or three times a day.
A combination of the oxygen diffusible
material in RGP lenses and tear film
movement allows sufficient oxygen to get to
the cornea from the air so wearers are not at
risk of hypoxia in the eye. In contrast, soft
lenses hardly move on the cornea — they
generally grip onto the front of the eye so do
not allow the tear film to circulate. In addition,
soft lens material is not as oxygen permeable
as RGP lens materials and, as a result, soft
lens wearers have less oxygen reaching the
cornea. If the lenses are worn too much the
resulting hypoxia causes blood vessels to grow
into the cornea from the limbus (the corneoirido junction).
Corneal vascularisation is usually most
prominent in the 10 o’clock to 2 o’clock
positions around the iris. If one or more blood
vessels extends 2mm into the cornea, the
wearing time of the soft lens must be reduced.
The danger of corneal vascularisation is
that the blood vessels will continually grow
and eventually reach the pupillary area,
causing blindness. (I have seen a couple of
cases of vascularisation causing blindness.)
People wearing soft lenses most of the time
(eg, five days a week and 12 hours a day),
must have regular aftercare (ideally every six
months) from their optometrist. Aftercare
appointments involve the optometrist
checking vision with the lenses but, most
importantly, looking at the front of the eyes
for corneal vascularisation. (If a soft lens
wearer does not attend six-monthly aftercare
appointments, I refuse to supply any more
contact lenses.)
Microbial keratitis
The worst complication associated with
contact lens wear is inflammation of the
cornea (keratitis) caused by pathogens.
Microbial keratitis can easily lead to blindness,
even with treatment. The two worst organisms
to infect the eye are Pseudomonas aeruginosa
and acanthamoeba. The wearing of soft
contact lenses is a big risk factor for
pseudomonas and acanthamoeba corneal
infection but the wearing of RGP lenses does
not rule out infection. As well as improper
contact lens care, overnight wearing of contact
lenses is a major risk factor.
Pseudomonas Pseudomonas aeruginosa is a
Gram negative aerobic rod, measuring
0.5–0.8µm by 1.5–3.0µm. Nearly all strains
are motile by means of a flagellum.
Pseudomonas is commonly found in water
and soil. It can also grow in distilled water.
The bacterium is an opportunistic pathogen,
exploiting some break in host defences. It can
infect any tissue in the body as long as the
tissue defences are compromised. It is also a
common nosocomial pathogen.
A patient presenting with a pseudomonas
keratitis will commonly be a soft lens wearer.
Inflammation is usually unilateral. The eye will
typically be painful and red. Because of the
eye pain, the eyelid will be shut and there will
be a lot of watering. (It can be difficult to
examine the front of the eye because the
patient will want to keep the eye closed.)
On examination, an optometrist would
usually see a small, round, white opacity near
the edge of the cornea. This is a corneal ulcer
(also known as ulcerative keratitis or, when
due to pseudomonas, pseudomonas keratitis).
About 30 per cent of corneal ulcers are
associated with wearing contact lenses.
Bacteria can colonise the lens storage case
or the lens itself. During contact lens wear,
pathophysiological changes in the corneal
epithelium occur, decreasing the defence
capability of the eye. Bacteria can adhere to
the contact lens and, when the lens is placed
on the eye, detach from it and invade the
compromised epithelium. If untreated, the
bacteria will invade the underlying corneal
layers and cause a full thickness corneal ulcer.
The higher risk of disease in overnight lens
wear has led to the speculation that contact
lens induced corneal hypoxia predisposes
contact lens wearers to a greater rate of
corneal infection because of compromised
corneal epithelial integrity, impaired wound
healing and an increased susceptibility of
corneal epithelial cells to bacterial binding.1
Patients diagnosed with microbial keratitis
are admitted to hospital because hourly
instillation of antibiotic eye-drops is required
to try to control the infection — if the patient
falls asleep (which may be unlikely due to the
pain) a nurse will wake him or her up to instil
the drops.
Chloramphenicol eye-drops are ineffective
against Pseudomonas aeruginosa and
fluoroquinolones, such as ofloxacin or
ciprofloxacin, are commonly prescribed. The
hourly instillation of the drops may be
necessary for weeks. Only once the infection is
under control, is the dosage tapered.
Gentamicin eye-drops can be used but, again,
hourly instillation is required.
Prednisolone eye-drops can be used (eg,
one drop three times a day) for inflammation
once the infection is under control. It is
important not to use a steroid drop before this
stage because steroids can exacerbate corneal
ulcers and worsen infections.
Even if treatment is successful, a corneal
scar can be left. If this is in front of the pupil,
vision will be reduced or the eye will be blind.
Acanthamoeba Acanthamoeba is an amoeba
Marvyn Elton will be available to answer
questions online on the topic of this article
until 20 September 2010
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expert
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found in water and soil. Acanthamoeba
species have two stages in their life cycle, a
trophozoite stage that feeds on bacteria and
fungi (if a lens storage case has become
contaminated with pseudomonas,
acanthamoebae can feed on it) and a nondividing cyst stage, which is resistant to stress.
Wearing soft contact lenses is the most
common risk factor for development of
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PANEL 2: CASE REPORTS
1. A 19-year-old man presented with a five-day
history of red, painful eyes and he could not
see. On examination, he had large corneal
ulcers in both eyes; these were located in the
central cornea rather than the corneal
periphery (see Image), explaining the patient’s
blindness. The patient was admitted to hospital
for hourly instillation of ofloxacin eye-drops.
Corneal epithelial scrapes confirmed that
Pseudomonas aeruginosa and acanthamoebae
were present.
The patient was started on hourly PHMB
0.02 per cent eye-drops and propamidine 0.1
Large corneal ulcer (Karl Southerton, Western Eye
Hospital)
per cent drops in addition to the ofloxacin.
Within a few days, both eyes became more
comfortable, the ulcers were reducing in size and vision in both eyes improved. This patient was
fortunate to regain normal visual acuity because, in some cases, corneal scars can cause
permanent blindness. His case is of interest because he wore daily disposable lenses. On
questioning, he said that he was reusing the lenses after disinfecting them. The disinfecting
solution and the contact lens case were not available for analysis. It emphasises that even when a
patient wears daily disposables, it is worth checking that these are not being misused.
2. A 34-year-old man presented with a three-day history of a red, painful right eye and blurred
vision. On examination, there was mild disturbance of the cornea; that is, there were corneal
epithelial erosions but no ulceration. However, because the eye was painful and the patient was a
soft contact lens wearer he was assumed to have an early bacterial keratitis and started on
ofloxacin eye-drops six times a day, prescribed in case Pseudomonas aeruginosa was present.
Two days later there was no improvement in his symptoms; the corneal erosions were still present
but were more linear and dendritic in appearance. The patient was thought to have a herpes
simplex keratitis and was treated with aciclovir eye ointment five times a day. When there was still
no improvement the following week, acanthamoeba keratitis was suspected. The patient was
admitted to hospital and started on PHMB 0.02 per cent and propamidine 0.1 per cent eye-drops
hourly. A corneal epithelial scrape confirmed the presence of acanthamoebae. There was good
response to the treatment and as the eye improved the drops were tapered. On questioning this
patient revealed that he was using tap water in his contact lens case. This case also shows how
early acanthamoeba keratitis can look like a herpes simplex keratitis.
acanthamoeba keratitis — 80–90 per cent of
cases are contact lens wearers. Patients
typically present with a red, painful eye (see
Figure 2, p238), which he or she will try to
keep closed.
Like a pseudomonas keratitis,
acanthamoeba keratitis is an ocular
emergency, requiring hospital admission for
hourly instillation of eye-drops and specialist
attention. Polyhexamethylene biguanide
(PHMB) 0.02 per cent eye-drops (eg, from
Moorfields Pharmaceuticals) are used.
Propamidine can also be used with the
PHMB. As the keratitis improves, the dosage
of the eye-drops can be tapered.
The bottom line is that if a contact lens
wearer complains of a red, painful eye
chloramphenicol eye-drops or ointment must
not be supplied. If the person wears soft
contact lenses, alarm bells should ring loudly.
In such cases the best action would be to send
the person to an optometrist or eye casualty in
hospital to rule out a pseudomonas or
acanthamoeba infection. The pharmacist
could write a letter to this effect for the patient
to take. Topical chloramphenicol is ineffective
against these two micro-organisms. I describe
two cases in Panel 2.
4 September 2010 (Vol 285)
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Drug-lens interactions
Pharmacists will be aware that many eyedrops cannot be used while wearing soft
contact lenses because of the risk of
adsorption of ingredients, typically
preservatives such as benzalkonium chloride,
onto them. Lenses should not be worn for the
duration of treatment or preservative-free
drops used, although, according the British
National Formulary, RGP lenses can be worn.
Eye ointments should not be used with
contact lenses and oily eye-drops should be
avoided.
Consequences of drug-lens interactions
include eye discomfort, contact lens damage
and toxic interactions. Examples of
interactions include:
• Increased deposits (eg, with dopamine)
• Lens discoloration (eg, with rifampicin and
sulfasalazine)
• Lens dehydration (eg, with isotretinoin)
• Corneal oedema (eg, with oral
contraceptives, especially high strength
oestrogens)
• Reduced blink reflex and eye movement (eg,
with tricyclic antidepressants)
• Reduced tear production (eg, with sedating
antihistamines)
An example of a recent advance in contact
lens practice is orthokeratology (ortho-K),
which uses specially designed RGP lenses,
worn during sleep, to reshape the cornea.
When removed in the morning, vision is
corrected and there is no need for glasses or
contact lenses during the day. Research into
the field of contact lenses, new materials and
new solutions continues. Pharmacists might
be interested to know that there has also been
research into the possibility of using contact
lenses for drug delivery (eg, lens wear might
enable glaucoma medicines to be given for up
to 30 days).4
Signposting
• The British Contact Lens Association website
(www.bcla.org.uk) contains answers to
frequently asked questions.
• “Look after your eyes” (www.lookafteryoureyes.
org), run by the College of Optometrists,
explains common eye health issues.
Resources
• For further details of drug-lens interactions,
read GL Muntigh’s “Drug and contact lens
interactions” in SA Family Practice
(2005;47:24–28).
References
1 Stapleton F, Keay L, Jalbert I, Cole N. The
epidemiology of contact lens related
infiltrates. Review. Optometry and Visual
Science 2007;84:4.
2 Griffiths H. Soft contact lens care products: an
update. Optometry in Practice 2003;4:31–42.
3 Atkins N. Developments in lens care solutions.
Optician 2006;231:6037.
4 Bowers Ciolino J, Hoare TR, Iwata NG, Behlau
I, Dohlman CH, Langer R et al. A drug-eluting
contact lens. Investigative Ophthalmology
and Visual Science. Available at www.iovs.org
(accessed on 23 August 2010).
CPD articles are commissioned by The
Journal and are not peer reviewed.
PRACTICE POINTS
Reading is only one way to undertake CPD
and the regulator will expect to see various
approaches in a pharmacist’s CPD portfolio.
1 Do you know your local opticians? FInd
out how they might like you to refer
people with eye problems requiring
investigation with a slit lamp.
2 How would you advise a person wanting
to switch multipurpose solutions? Use the
article by Atkins N (reference 3) to inform
your decision.
3 Make sure your staff are trained on the
correct sale of chloramphenicol and how
to deal with contact lens wearers.
Consider making this activity one of your nine
CPD entries this year.