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Volume 1, Issue 5
2013
A Learning Resource for Optometrists from the School of Optometry & Vision Science, University of Waterloo, and the School of Optometry, University of Montreal
Corneal Infiltrates With Silicone Hydrogel
Contact Lens Wear and the Role of Compliance
B Y K ATHRYN D UMBLETON , P H D, MCO PTOM , FAAO, AND
D OERTE L UENSMANN , P H D, D IPL I NG (AO), FAAO
Corneal infiltrates occur as a result of corneal inflammation and can range from very mild, selflimiting focal infiltrates to sight-threatening microbial keratitis. The primary focus of this
issue of Optometry Rounds is on non-sight threatening infiltrates, which are seen frequently in
contact lens wearers and represent an inconvenience for the both the patient and the eye-care
practitioner due to additional chair time, therapeutic management and counseling.
Corneal infiltrates are discrete accumulations of inflammatory cells that have migrated into
the usually transparent corneal tissue in response to a variety of stimuli. They can be indicative of
both inflammatory and infectious corneal disease. Eye care practitioners (ECPs) have been
observing corneal infiltrates in their soft contact lens wearers since the introduction of these
lenses in the 1970s.1-3 Corneal infiltrates have historically been reported to be associated with
hypoxia, contamination of contact lenses or storage cases with microorganisms, and sensitivity to
cleaning solutions.3-5
Since the 1970s there have been many changes in the types of soft lens materials available, the
recommendations for replacement frequency, wearing modality, and the care systems used for
cleaning and disinfecting lenses. Arguably the most significant change has been the introduction
of highly oxygen permeable silicone hydrogel materials, which now account for the majority of
contact lenses prescribed in Canada, the United States (US), and many other countries.6 Despite
these significant improvements in contact lenses and their care products, infiltrates continue
to occur in some wearers.7,8
Classification
The first detailed analysis of corneal infiltrates in contact lens wearers was made more than
30 years ago. Josephson and Caffery3 categorized infiltrates primarily according to their presumed etiology – many of which are not as relevant in contemporary contact lens wear – but also
with reference to the associated signs and symptoms. Another approach is to classify infiltrates
according to their severity.9,10 Despite its inherent difficulties, the most frequent method of classifying infiltrative events is to consider them as being either “sterile” or “microbial”.11-14 Further
classification of infiltrates has also been suggested according to clinical subtype.15 Three broad
categories have been proposed using this classification:
• Serious and symptomatic
• Clinically significant and symptomatic
• Clinically insignificant and asymptomatic
“Serious and symptomatic” infiltrates are limited to those associated with microbial keratitis.
The more common cases of corneal inflammation fall under the latter 2 categories; this review
will concentrate principally on these infiltrates, while still recognizing that it is not always possible to be certain about the underlying etiology. The clinical presentation, epidemiology, and incidence of microbial keratitis with silicone hydrogel lenses have been reported elsewhere,16-18 and
will not specifically be discussed in this review.
Available online at www.optometryrounds.ca
Paul Murphy, FCOptom, PhD, FAAO
Professor and Director
Thomas F. Freddo, OD, PhD, FAAO
Professor and Co-Editor, Optometry Rounds
Contributing Faculty Authors:
Kathryn Dumbleton, PhD, MCOptom, FAAO
Head of Clinical Research,
Centre for Contact Lens Research
Doerte Luensmann, PhD, Dipl Ing (AO), FAAO
Clinical Scientist,
Centre for Contact Lens Research
École d’Optométrie
School Administration:
Christian Casanova, PhD
Director and Professor
Neurophysiology and Imaging
Danielle de Guise, OD, MSc
Associate Director of Cycle 1 Studies
Binocular Vision and Orthoptics
Jocelyn Faubert, PhD, FAAO
Associate Director of Research and Advanced Studies
Professor, Psychophysiology and Visual Perception
Jacques Gresset, OD, PhD, FAAO
Secretary and Professor
Epidemiology and Low Vision
Editorial Committee:
Jean-François Bouchard, BPharm, PhD
Associate Professor, Neuropharmacology
Pierre Forcier, OD, MSc
Associate Professor, Ocular Health
Langis Michaud, OD, MSc, FAAO (Dipl.)
Associate Professor, Contact Lenses
Co-Editor, Optometry Rounds
Judith Renaud, OD, MSc
Assistant Professor, Low Vision
University of Waterloo
School of Optometry & Vision Science
200 University Avenue West, Waterloo, ON N2L 3G1
Université de Montréal
École d’Optométrie
3744 Jean-Brillant, Montreal, QC H3T 1P1
The editorial content of Optometry Rounds is determined
solely by the School of Optometry & Vision Science,
University of Waterloo, and the School of Optometry,
University of Montreal.
Figure 1: Focal corneal infiltrates
Clinical Appearance
When observed with the slit lamp biomicroscope, “sterile” corneal infiltrates have the appearance of small round
hazy greyish-white opacities, which may be focal (Figure 1)
or diffuse. They may be located just beneath the epithelium
or in the anterior stroma. These areas of opacity are composed of inflammatory cells, in particular polymorphonuclear leukocytes. The size of the infiltrates can vary from
<0.5 mm to 1.5 mm in diameter.4 Infiltrates may be graded
according to number, severity, size, and area affected.3,19
Commonly Used Terminology
Infiltrative keratitis (IK) is a general term used to
describe the presence of infiltrates in the cornea.7,20,21 Many
cases of IK are thought to be due to the presence of grampositive exotoxins found on or near the lid margin. 21,22
Symptoms associated with IK include mild to moderate
irritation (often described as a foreign body discomfort),
mild redness, lacrimation, photophobia and occasionally
mild discharge. 7,20,21 In many cases, however, patients
report no associated symptoms. In most cases, discontinuation of contact lens wear for a few days results in full resolution of any signs and symptoms. While no specific
treatment is required in these cases, ocular lubricants may
alleviate symptoms and topical corticosteroid therapy may
expedite resolution.7,23
The term contact lens peripheral ulcer (CLPU) is frequently used to describe the inflammatory response that
presents as a single small, circular, peripherally or midperipherally located infiltrate in the anterior stroma, with
associated fluorescein staining of the overlying epithelium
(Figure 2).20,24,25 This condition has been described as being
a hypersensitivity reaction to the (usually gram-positive)
exotoxins released by pathogenic bacteria.26,27 CLPU may
cause mild to moderate pain (foreign body sensation),
mild lacrimation, and mild photophobia.7,20,25 Following
acute presentation with associated symptoms, the corneal
epithelium regenerates within a few days. During this time,
Figure 2: Contact lens peripheral ulcer with surrounding
diffuse infiltration
diffuse infiltration surrounding the lesion may also
develop. In some cases, there is no acute presentation and
the only telltale sign is a well-defined circular “scar” that
fades with time. Because of the similarities in appearance
to microbial keratitis, particularly in the early stages of
development, differential diagnosis between the 2 conditions is extremely important.7,9 Since CLPUs are self-limiting, no specific treatment is required for their resolution;
however, antimicrobial treatment may be instigated as a
precautionary measure in cases of suspected microbial keratitis. Similar to IK, ocular lubricants may be dispensed to
alleviate symptoms and topical corticosteroid therapy may
also expedite the recovery process.7,23
Phlyctenulosis is an inflammatory response that presents with white nodules and associated hypermia in the
limbal region.28 This condition is typically self-limiting;
however, in more severe cases it progresses to the peripheral
cornea and may require treatment with topical steroids.28
Contact lens acute red eye (CLARE) is a generally unilateral, acute inflammatory condition that occurs with
overnight lens wear and is thought to occur in response to
gram-negative organisms (eg, Pseudomonas species) colonizing the lens surfaces and releasing endotoxins. 22,29-31
CLARE has been reported to be associated with upper respiratory infections, which may be due to the presence of
other gram-negative organisms including Haemophilus
influenzae.31 Cases of CLARE generally occur in the early
hours of the morning, following sleeping while wearing
contact lenses, and are accompanied by a moderately
painful (foreign body sensation) red eye, with associated
epiphora and photophobia (Figure 3). The inflammation
manifests as either focal or diffuse subepithelial infiltrates,
which are usually observed in the mid-periphery of the
cornea, close to the limbus.20 The infiltrates rarely stain
with fluorescein and rapidly resolve. Since CLARE is selflimiting on removal of contact lenses, management
involves simply temporary discontinuation of lens wear
and ocular lubricants during the acute stage.
Figure 3: Contact lens acute red eye
Smoking
Smoking is associated with a doubling of risk of developing corneal infiltrates in hydrogel lens wearers,19 and a
similar increase in risk (1.4–4 times greater) has been
reported for silicone hydrogel lens wear, 41,42 but not in
younger wearers.37
Previous inflammatory events
Risk Factors
Historically, incidence rates for infiltrates ranging from
0%–41% have been reported with conventional hydrogel
materials. 4 A literature review by Szczotka-Flynn and
Chalmers32 concluded that the incidence rate was approximately 2 times greater with silicone hydrogel lens wear,
with rates in daily wear of 2%-3% for symptomatic infiltrates and 7%-20% when asymptomatic events were
included. Patient-related risk factors associated with the
corneal infiltrates in contact lens wearers, regardless of the
lens material worn, are discussed below.
Age
Both young (<25 years) and older (>50 years) contact
lens wearers have been reported to be at a greater risk of
developing corneal infiltrates.33-36 Until recently, the risks
for children and adolescents had not been specifically
investigated; however, a large retrospective chart review of
>3500 soft (hydrogel and silicone hydrogel) contact lens
wearers aged 8–33 years reported a peak risk for infiltrates
in the 15–25-year age group, with a lower risk in younger
children.37 These increased risk rates in adolescents may be
related to both physiological and behavioural differences
in this demographic group.36,37
Sex
In some studies, males have been reported to be at
greater risk of developing infiltrates. A relative risk of 1.3–
1.4 was reported in male subjects by Morgan et al,38 which
is similar to the rate reported for microbial keratitis.12,16,39
This may be related to different perceptions of health risks
between males and females,40 or possibly due to differences
in hygiene with respect to lens care. Males have also been
reported to be greater risk takers.36 Interestingly, a retrospective chart review study found no difference in rates
between sexes in a younger population (8–15 years).37
A history of previous inflammatory events has been
shown to be associated with a 4–7-fold increase in risk for
developing corneal infiltrates in silicone hydrogel wearers.34 Dumbleton et al43 reported that 25% of overnight
wearers of silicone hydrogel lenses with infiltrates or CLPU
experienced repeated episodes. Conversely, Morgan et al41
found that patients who experienced previous ocular complications were 1.8 times less likely to develop corneal infiltrates. The reason for this is not clear but may be related to
the fact that these individuals are more likely to take
greater care when wearing their lenses.
Daily wear versus overnight lens wear
Most clinical trials investigating the incidence of
inflammatory events with silicone hydrogel lenses have
been reported for overnight wear.8,35,41,44-49 These studies
describe incidence rates for sterile keratitis of 1.3–5.5 per
100 patient-years for conventional hydrogel lenses and 2.9–
6.7 per 100 patient-years for silicone hydrogel lenses.50 A
meta-analysis by Szczotka-Flynn and Diaz51 determined
nearly twice the corneal inflammatory event (CIE) rate
with extended wear (≤30 days) of silicone hydrogel lenses as
with 7 days of conventional hydrogels (14.4 versus 7.7 per
100 eye-years). A prospective study evaluating corneal infiltrative events with continuous wear of silicone hydrogel
lenses reported a cumulative 1-year incidence of 26.7%.42 A
multicentre case-control risk analysis for the development
of symptomatic infiltrative events by Chalmers et al, 52
including >50 different contact lens types and >10 different
care regimens, found that the risk associated with extended
wear was 4.6 times higher than daily lens wear.
Incidence rates for corneal infiltrates in patients using
daily-wear silicone hydrogel lenses are not as well defined
as they are for overnight wear, which have been investigated in large post-marketing surveillance studies. 45,46
A 1-year incidence rate of 19.6% identified by Carnt et al53
with daily-wear silicone hydrogel lenses conflicts with
reports of few or no adverse events in other daily wear
studies.48,54,55 This disparity is most likely due to differences
in study design, particularly the more frequent subject
follow-up in the Carnt study.
Replacement frequency
The majority of contemporary soft contact lenses are
replaced after 1 day, 2 weeks, or 1 month. More frequent
replacement has been associated with fewer complications in patients wearing hydrogel lenses.56 A recent
retrospective study by Chalmers et al52,57 found that
wearers of reusable lenses are at an 8-fold greater risk
of developing corneal infiltrates than daily disposable
lens wearers. Counterintuitively, Dart et al16 found
that the use of daily disposable conventional hydrogel
lenses increase the risk of developing microbial keratitis 1.6-fold. They further reported on differences
between daily disposable lens types and concluded
that the interaction between the lens and the ocular
surface may play a more important role in the development of microbial keratitis than oxygen permeability of the lens material and lens case contamination.
The relative risks for daily disposable silicone hydrogel lenses are unknown as these lenses were not available commercially when the previous studies were
conducted.
Care regimens
Multipurpose solutions have been reported to
confer a significantly higher risk of infiltrates than
hydrogen peroxide disinfection solutions.37,53 Recent
speculation and discussion among ECPs that specific
combinations of multipurpose solution and silicone
hydrogel contact lens material may be more likely to
cause corneal infiltrates has largely been based on the
reports of case series.58-63 This has been supported by
results of a recent study by Carnt et al,53 who investigated the incidence rates of CIEs in 20 combinations
of silicone hydrogel contact lenses and lens solutions.
They reported substantial differences between the
combinations, and found significantly lower incidence rates of CIEs with hydrogen peroxide systems
than with combination solutions. However, to date,
there has been no prospective, controlled study in
which the incidence of infiltrates has been compared
between users of various combinations of silicone
hydrogel lenses and multipurpose solutions. A recent
retrospective analysis of 166 cases of corneal infiltrates in younger (<34 years) contact lens wearers
found no association between the presentation of
infiltrates and a specific lens material and solution
combination.57
Compliance
Noncompliance among contact lens wearers
remains a significant problem despite many recent
improvements in lens materials and care regimens. A
recent study in the US reported that only 32% of
patients are compliant in their lens wear and care
behaviours.64
Hygiene and disinfection
Failure to wash hands prior to handling lenses
confers a 1.5-fold increased risk for developing
microbial keratitis16 and 2-fold higher risk for developing sterile keratitis. 50 Many contact lens wearers
also fail to use their care systems as recommended.
It has been reported that 40%–75% of wearers regularly fail to rub and rinse lenses65-67 despite evidence
that these steps reduce the risk of microbial keratitis
when using multipurpose care systems, 68 and may
be beneficial in avoiding corneal infiltrates. 67
Incomplete contact lens disinfection can occur
when patients “top up” their solution rather than
completely replacing it with fresh solution.
This practice was implicated in both of the recent
outbreaks of Fusarium keratitis and Acanthamoeba
keratitis.69,70
Lens replacement
The most commonly reported aspect of noncompliance by contact lens wearers is lens replacement.71-75
Two recent studies have shown that failure to replace
lenses appear to be associated with a higher overall
risk of lens-related complications.75,76
Contact lens case cleaning and replacement
Proper lens case cleaning includes daily rubbing
and rinsing of the case with the multipurpose solution, tissue wiping, and air-drying the case. Poor case
hygiene confers a 6.4-fold greater risk of developing
microbial keratitis, 17,77 and an association has also
been reported between inadequate case cleaning and
“sterile” infiltrates.78 Infrequent case replacement is
another common problem, and was found by
Stapleton et al77 to increase the risk of microbial keratitis by 5.4 times. The recommended replacement
interval ranges from monthly to every 6 months. It is
unknown whether patients with older cases are also
at greater risk of developing corneal infiltrates, particularly since studies have confirmed that biofilm
builds up in lens cases over time. 79,80 Patients who
experienced previous lens complications were subsequently 3.4 times more compliant with case replacement than those who had never experienced ocular
problems.64
Conclusion
Despite the fact that corneal infiltrates are not
sight threatening as they are for microbial keratitis,
they affect the patient’s ocular health and well-being
as well as the ECP’s time in evaluation, management,
and counseling. ECPs should be aware of the various
patient-related factors associated with corneal infiltrates for proper fitting of prospective wearers with
contact lenses. Factors over which the ECP has more
control include the wearing schedule, replacement
frequency, and care system recommended for each of
their contact lens wearers. Despite careful product
selection and patient instructions, compliance
remains a significant factor in the risk of developing
infiltrates. Therefore careful counseling and education
with respect to all aspects of contact lens wear and
care are essential in the reduction of risk of all contact
lens-related complications.
Dr. Dumbleton is the Head of Clinical Research, Centre
for Contact Lens Research, University of Waterloo,
Waterloo, Ontario, and President of the American
Optometric Foundation. Dr. Luensmann is a Clinical
Scientists in the Centre for Contact Lens Research,
University of Waterloo, Waterloo, Ontario.
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In the preceding 2 years, Dr. Dumbleton has received a grant
from the Canadian Optometric Education Fund, honoraria
from Alcon and Abbot Medical Optics, and travel grants from
Alcon. Dr. Luensmann has also received travel grants from
Alcon. The Centre for Contact Lens Research has received
research funding from Advanced Vision Research, Alcon,
Allergan, Cooper Vision, Essilor, Johnson & Johnson, and
Visioneering.
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