LENS-RELATED DRY EYE
The
Latest Research and Treatment Options for Lens-Related Dry Eye
Recent studies shed light on what's new and
what's on the horizon for managing lens-related dry eye.
By Kelly K. Nichols, OD, MPH, PhD, & Jason
J. Nichols, OD, MPH, PhD
We
can't seem to get away from dry eye. With up to 12 million North Americans experiencing
the disorder and more than 25 percent of contact lens wearers experiencing dry eye
symptoms, there's been a push for new treatments, improved diagnostic techniques
and new theories on dry eye etiology.
Dry eye syndrome is a disorder of the
anterior ocular surface characterized by symptoms of dryness, irritation (discomfort)
and grittiness. Contact lens-related dry eye is a related disease characterized
by reduced comfortable contact lens wearing time and feelings of dryness or irritation,
which may or may not go away following lens removal.
Something Old, Something New
Over the last 15 years, research in the area of
dry eye with and without contact lenses has significantly increased, largely driven
by the report of the National Eye Institute and Industry workshop on clinical trials
in dry eye (Lemp, 1995). This workshop attempted to systematically define dry eye,
to set forth a classification scheme for different types of dry eye and to recommend
diagnostic criteria for the diagnosis of dry eye for clinical researchers. While
the workshop provided a framework for the study of dry eye, the report highlighted
many areas in which knowledge about dry eye, including contact lens-related dry
eye, was lacking.
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Figure 1. Does
reduced tear break-up time demonstrate "dysfunctional tear film"? |
Two groups, the Delphi Panel and the Dry Eye
Workshop (DEWS), recently assembled expert clinicians and researchers to redefine
and reach consensus regarding dry eye treatment, the status of the field and emerging
research directions. The pending peer-reviewed reports of these two groups will
provide the most comprehensive overview of dry eye in terms of research and of treating
patients.
The NEI/Industry report set forth a
definition of dry eye as follows: "Dry eye is a disorder of the tear film due to
tear deficiency or excessive tear evaporation which causes damage to the interpalpebral
ocular surface and is associated with symptoms of ocular discomfort." This is somewhat
different from the term "Dysfunctional Tear Film," developed by the Delphi Panel.
This term, while different from "Dry Eye Syndrome," is more encompassing and supports
the common notion that some characteristic unifies all the sub-categories of dry
eye (Figure 1).
Symptoms in Contact Lens Patients
We've
all had patients for whom the dry eye symptoms outweigh the abnormal ocular signs.
In contrast, some severe dry eye patients who have significant surface damage report
symptoms that don't seem to correlate with the clinical signs. Regardless of the
severity of the disorder, asking the appropriate dry eye questions can assist you
in monitoring change in the disorder over time or with treatment.
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Figure
2a. In-vivo OSU interferometric images of PLTF (roughly 8mm surface).
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Figure 2b. Unlike 2a (stable PLTF after blink),
this image shows few fringes, and much of the lens surface is exposed. |
In general, contact lens wearers report
more ocular symptoms than do non-contact lens wearing patients. Both groups report
symptoms of dryness, soreness, grittiness, light sensitivity, pain or itching. Contact
lens wearers typically report increased ocular dryness compared to non-lens wearers,
and their complaints of dryness often increase with daily wearing time.
In addition, patients frequently cite
complaints of dryness as reasons for discontinuing lens wear. Prichard and coworkers
(1999) found that after 5 ±6 years of lens wear, 12 percent of contact lens
patients discontinued contact lens wear permanently, primarily due to discomfort
(49 percent) and dryness (9 percent) symptoms. Schlanger (1993) surveyed 199 individuals
who had discontinued contact lens wear and again showed the most common reason for
lens discontinuation was discomfort (72 percent of individuals cited this reason).
In addition, patients who undergo refitting because of dryness complaints are more
likely to discontinue lens wear altogether.
We know little about factors other
than symptoms (such as demographics, differences in lens types, etc.) associated
with lens discontinuation. Why do certain patients tolerate uncomfortable lens wear
while others seek refractive surgery? Why do some patients find contact lens wear
too inconvenient (solutions, drops, out-of-pocket costs)? Few studies to date have
examined differences in patient factors when comparing self-perceived satisfied
current lens wearers with self-perceived dissatisfied current wearers. At the 2005
American Academy of Optometry annual meeting, Nichols et al presented data demonstrating
that in patients reporting current or previous experience with contact lenses, 26.3
percent reported that contact lenses weren't the ideal form of visual correction
for them (contact lens dissatisfaction) and 24.1 percent had permanently discontinued
contact lens wear. Previous lens wearers were more likely than current lens wearers
to be male, to be older, to have started contact lens wear at a later age and to
have tried either rigid or both soft and rigid lenses. The primary self-reported
reason for both contact lens dissatisfaction and discontinuation was ocular symptoms
(dryness and discomfort) followed by preference for another corrective modality.
Factors Associated with Lens-related Dry Eye
Nichols and Sinnott (2006) showed that several
factors are related to contact lens-related dry eye status, including female gender,
lenses with higher nominal water content, rapid pre-lens tear film thinning time,
frequent usage of over-the-counter pain medication, limbal injection and increased
tear film osmolality. While some of this is common sense and well accepted, some
findings, including the increased tear film osmolality and rapid tear film thinning,
suggest potential mechanisms for dry eye in contact lens wearers.
Osmolality has often been touted as a gold
standard test for dry eye, and this study is the first to confirm higher osmolality
in lens-related dry eye using a new generation, small sample tear osmometer.
In summary, monitoring changes in lens
comfort, particularly in female patients wearing high-water contact lenses, may
help prevent this group from contact lens dropout.
Contact Lens and Tear Film Interactions
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Figure 3. Superior lid staining with fluorescein. |
The stability of the tear film during contact
lens wear depends on the surface chemistry of the lens and its physical interactions
with each layer of the tear film. The superficial lipid layer prevents evaporation
of the tear film, which helps maintain lens hydration in contact lens wearers. In
general, the pre-lens tear film (PLTF) provides comfort and lubrication to the conjunctiva,
especially during the blink, in addition to providing a smooth optical surface.
An irregular PLTF, similar to what happens during the dewetting or evaporative process,
results in light scatter and reduced visual acuity, especially in low contrast situations.
This finding is consistent with clinical reports and symptom research findings describing
changing or fluctuating vision which may clear with a blink (Begley et al, 2001).
The
past several years have brought the development of optical techniques to investigate
tear film thickness and stability, including interferometric analysis (King-Smith
et al, 2000, 2006; Goto et al, 2004), OCT analysis (Wang et al, 2003) and methods
of quantitatively evaluating tear film breakup dynamics (Begley et al, 2006). Figure
2 illustrates
the process of PLTF dewetting and breakup on the surface of a hydrogel lens using
imaging interferometry techniques.
Diagnostic Advances
It's been a unique challenge to improve our ability
to diagnose contact lens-related dry eye beyond symptomatology. Many of the diagnostic
tests have existed for many years, and we've largely performed them without change.
Recent advances in real-time digital video assessment of tear film break-up patterns
and interferometric techniques have not reached a level to which the technology
is commercially available.
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Figure
4. Conjunctival lissamine green staining in a symptomatic lens wearer.
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What's new in this area? Over the past few
years, Korb et al coined the term "lid wiper epitheliopathy" (Figure 3) to represent
staining of the anterior superior tarsal conjunctiva, which is highly associated
with symptomatic contact lens wear. To evaluate this staining, instill fluorescein
and lissamine green in the eye in a sufficient quantity to cover the ocular surface.
Then evert the superior lid and evaluate for staining. Grade the horizontal length
and the width of the staining, with a grade 2 representing approximately 50 percent
staining of the "lid wiper" area (a staining pattern of approximately 6mm x 1mm
coverage). Although studies using different treatment regimens haven't utilized
this as an outcome measure, if you do see this staining pattern in symptomatic patients,
you should monitor it for possible improvement with changes in the management plan.
Along the lines of using vital dyes,
lissamine green has essentially replaced rose bengal dye in clinical practice. In
evaluating contact lens-related dry eye, lissamine green assessment of conjunctival
staining is often the most significant abnormal finding and can be very dramatic
(Figure 4). You can also monitor this staining for improvement with treatment.
Don't Change Everything at Once
It's
often more successful to take a step-wise approach to managing contact lens-related
dry eye patients rather than changing several components simultaneously. Such an
approach may involve changes to lens materials, wearing schedules, replacement frequency,
solutions and rewetting drops, as well as punctal occlusion and pharmacological
intervention. Since the approval of cyclosporine A (Restasis, Allergan) and with
the advent of several good lubricating eye drops for treating dry eye, contact lens
management strategies have moved away from multiple contact lens refittings or only
changes in solution use.
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TABLE 1 |
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Studies
of Dry Eye Symptoms During Lens Wear
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STUDY |
SAMPLE
SIZE |
FREQUENCY
OF
CL/DE SYMPTOMS |
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Brennan, et al (1989) |
104 |
75% |
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Guillon, et al (1997) |
184 |
44% |
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Doughty, et al (1997) |
3285 |
50% |
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Vajdic, et al (1999) |
171 |
73% |
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Begley, et al (2000) |
83 |
50% |
|
Nichols, et al (2005) |
893 |
52% |
In
addition, the popularity of silicone hydrogel lens materials has changed initial
and refitting patterns, leading many practitioners to fit dry eye patients with
silicone hydrogel lenses. Peer-reviewed data supporting increased comfort with silicone
hydrogel lenses in contact lens-related dry eye patients is limited. Manufacturers
continue to market both hydrogel and silicone hydrogel lenses for patients who have
dryness symptoms, such as Acuvue Oasys (Vistakon), Proclear Compatibles (CooperVision)
and Extreme H2O (Hydrogel Vision Corp.). Future studies are needed to
determine whether changing to a different lens material or changing the lens mater-ial/solution
combination is more effective in managing dryness.
Studies have demonstrated that
pre-lubrication of the ocular surface with a lubricant eye drop before applying
a contact lens may increase the comfortable lens wearing time. The use of cyclosporine
A in contact lens patients before lens application and after lens removal can also
significantly increase comfortable wearing time. Studies in this area have been
relatively small, and we need larger-scale studies that control for additional factors
such as additional rewetting drop/artificial tear usage, contact lens material,
age of lens, solutions and associated patient factors.
Management strategies for contact lens
wearers are the same as those for non-wearing dry eye patients, with the caveat
that patients who can wear lenses are most likely not in the severe dry eye diagnosis/management
category. However, you will occasionally see a patient who has significant dry eye
and extremely high motivation to wear contact lenses. In these cases, the typical
management strategy fails. Adding omega fatty acid supplementation (recommended
dose ~2g per day), lid massage and warm compresses and/or tetracycline/doxycycline,
in addition to cyclosporine, are clinically recommended to ensure adequate management
of any concurrent lid disease. Clinical evidence and scientific studies in this
area are beginning to support improvement on the basis of this management strategy,
which will continue to undergo evaluation in ongoing and future ocular surface research.
Team Players in the Future
Future recommendations for contact lens wearers
who have symptoms of dryness may include the pairing of specific solutions and materials
to maximize comfort and vision with lens wear. Proteomic and lipidomic studies to
investigate changes in tear film composition and lipid and protein deposition on
contact lenses in well-defined groups of patients may lead to customized lens/lens
care approaches through the development of biomarkers to diagnose and monitor changes
in dry eye disease. Current and anticipated advances in technology related to contact
lenses will change practitioner patterns in the next decade, and with those changes
will come the opportunity to reduce the rate of contact lens dropout and improve
the practice of contact lenses.
To obtain references for this article,
please visit http://www.clspectrum.com/references.asp and click on document #130.
Dr. Kelly Nichols is an associate professor
at The Ohio State University College of Optometry focused on the area of dry eye
research.
Dr. Jason Nichols is an assistant professor of optometry and vision
science at The Ohio State University College of Optometry.
Contact Lens Spectrum, Issue: September 2006