A Lens Fit for Dry Eye
Here are some clinical pearls to help treat and fit contact lens patients who present with dry eye.
This article offers some clinical pearls to help treat and fit contact lens patients who present with dry eye.
Lakshman N. Subbaraman, PhD, BSOptom, MSc, and Sruthi Srinivasan, PhD, BSOptom
Dr. Srinivasan is a research assistant professor at the Centre for Contact Lens Research, School of Optometry and Vision Science, University of Waterloo, Canada. She is a fellow of the American Academy of Optometry, member of the Association for Research in Vision & Ophthalmology and the Tear Film & Ocular Surface Society.
Dr. Subbaraman is the head of Biological Sciences at the Centre for Contact Lens Research, School of Optometry and Vision Science, University of Waterloo. He is a two-time recipient of the American Optometric Foundation’s prestigious William Ezell Fellowship, a fellow of the American Academy of Optometry and a member of the Association for Research in Vision & Ophthalmology.
This course is COPE approved for 1 hours of CE credit. COPE ID 37163-CL. Check with your local state licensing board to see if this counts toward your CE requirements for relicensure.
This continuing education course is joint-sponsored by the Pennsylvania College of Optometry.
The authors have no financial relationships to disclose.
Almost 50% to 80% of contact lens wearers experience symptoms of dry eye.1 Contact lens-related dry eye (CLDE) may be reported as dryness, discomfort, gritty sensation, irritation, stinging, burning or foreign body sensation.2,3 Discontinuations and dropouts from lens wear are primarily due to symptoms of discomfort and dryness.
CLDE is complex and multifac-torial. Increased tear evaporation, altered tear osmolarity, poor or low tear film quality and quantity, oxygen deprivation, lens deposits, reactions to lens care solutions and non-wetting surfaces are some of the factors that exacerbate dry eye in contact lens wearers. Environmental components, allergies and lid disease can also influence this condition.
This article provides an overview of the factors that influence CLDE and outlines some strategies for effective treatment.
Clinicians should start by determining which time of day is most problematic for the patient who complains of CLDE. Symptoms that develop two to three hours into lens wear are normally indicative of solution toxicity. On the other hand, end-of-day dryness may be due to lack of lens surface wetting or other material-related factors.
The FDA classifies commercially available hydrogel contact lens materials into four groups, depending upon their charge and water content: non-ionic, low water content (Group I); non-ionic, high water content (Group II); ionic, low water content (Group III); and ionic, high water content (Group IV). This material classification seems to be a very strong predictor of CLDE.
- Deposition. Hydrogel contact lenses absorb components from the tear film, particularly proteins, lipids and mucins.4-7 Deposits are associated with diminished visual acuity, dryness and discomfort, and lid-related inflammatory changes.8-13
High water content materials have been associated with significant tear film deposition.9,14-16 In particular, Group II lenses are prone to lipid deposition whereas Group IV lenses have been shown to attract more protein than lipids.6,17 Further, once tear proteins (such as lysozyme) firmly adsorb onto contact lens materials, the protein undergoes conformational changes and dena-turation.7,15,18,19 Protein denaturation is closely linked to inflammatory conditions, such as papillary conjunctivitis, and can also impact subjective comfort.11-13,20,21
Practitioners should advise their patients to maintain a clean and deposit-free lens surface, as well as review appropriate lens replacement schedules. Practitioners should also recommend that their patients rehydrate the lenses with rewetting drops since proteins exposed to hydrophobic surfaces are more likely to denature, which could potentially result in reduced comfort. Heavy lipid depositors should be advised to use a separate surfactant cleaner.
- Wettability. Deposition of
tear film-derived material reduces
wettability due to denatured protein and increased lipid deposition.17,22,23 This produces areas of
hydrophobicity, resulting in further
deposition and comfort problems.
If patients do exhibit reductions in
wettability, changing to another
lens material will likely have a minimal impact. Such patients are best
managed by switching to lenses
that are replaced more frequently,
such as daily disposable lenses, or
by prescribing rewetting drops that
- Water content and ionicity. Non-ionic, high water content
(Group II) and ionic, high water
content (Group IV) contact lens
wearers have a two to three times
greater likelihood of experiencing
dry eye than individuals wearing
Group I lenses.25 Further, Group II
lens materials are more commonly
associated with dry eye than the
Group IV lens materials.25 This
could be because the polar head
groups associated with the tear film
lipid molecules may be attracted to
higher water content lens materials,
which would leave their non-polar
tails away from the surface of the
lens and potentially lead to evaporation and/or dewetting. Patients
who wore low water content lenses
and maintained their hydration
generally reported that their eyes
"never felt dry" during lens wear.26 Thus, evidence to date suggests that
patients wearing lower water content contact lenses are less likely to
complain of CLDE.
- Dehydration. Dehydration is influenced by several factors, including the surrounding environment, water content, water binding properties, thickness and wearing period.30-38 Dryness symptoms occur more frequently in soft lens wearers during open-eye wear, when conditions are favorable for greater dehydration.27 Previous studies have shown that wearing thin, high water content lenses can result in increased epithelial staining due to pervaporation. Pervaporation is a process in which a permeate passes through a membrane and subsequent evaporation in the vapor phase.28,30 Factors that explain dehydration-induced discomfort include increased lid to lens interaction, changes in lens surface wettability or lens fit, and the development of epithelial staining due to pervaporation and subsequent desiccation.28-30
Conventional hydrogel material dehydrates more than silicone hydrogel lens materials.33,34 Remember, dehydration can affect the fit of a hydrogel lens by both altering the lens parameters and lowering the oxygen transmissibility.39
Clinicians must examine the patient for corneal staining after lens removal. The dye of choice in most clinical practices globally is sodium fluorescein. This dye aids in highlighting the extent of cellular damage/exposure of epithelial cells by staining in the form of punctate or coalescent areas. The use of a yellow barrier filter, in addition to cobalt blue excitation filter, is essential to visualize subtle changes. Examine the location of staining (i.e., mid-inferior smile staining patterns), advise proper blinking habits for patients with incomplete blinks and prescribe artificial tear supplements if necessary.
- Silicone hydrogel. Several studies have shown that silicone hydro-gel lens wearers reported reduced dryness and end-of-day discomfort compared to hydrogel contact lens patients.40-42 Silicone hydrogel lens wearers also reported better comfort after napping or sleeping, and in dry air or smoky environments because silicone hydrogel lens materials are less prone to evaporation (possibly due to their lower water content) and absorb fewer airborne pollutants than lenses with higher water content.40,43-46
Clinicians should consider refitting the patient with a high-Dk lens if oxygen deficiency is suspected. Practitioners should be careful when using lenses with an increased modulus of elasticity or poor surface wettability as they may cause other conditions, including contact lens-associated papillary conjunctivitis.
In dry and low-humidity environments, such as artificially heated rooms or during the winter months, quicker and greater lens dehydration likely exacerbate dryness in existing patients or induce symptoms in otherwise asymptomatic patients. Those who complain of CLDE due to such environmental conditions would benefit by rehydrating their lenses with rewetting drops.
- Solutions. Hydrogen peroxide solutions are considered the gold standard for disinfecting contact lenses. However, when residual peroxide is present on the lenses in sufficiently high concentrations, it can be toxic to the cornea and can cause discomfort. When peroxide-based systems are used at the right concentration, they can provide improved comfort in contact lens wearers.47,48
Over the last few years, several novel components have been added to multipurpose solutions, such as surfactants or ocular demulcents, to improve comfort, enhance water retention and improve surface wetting properties of contact lenses.
Clinicians should examine the lens and corneal surface carefully, ensure the appropriate cleaning solution is being used and check for patient compliance. Examine corneal staining to check if solution induced-corneal staining (SICS) is present. If SICS exists, advise appropriate lens-solution combinations or switch to daily disposables.
- Rewetting drops. Rewetting (or comfort) drops can be used to alleviate discomfort that is caused by dryness. Although they provide temporary relief from these symptoms, there is currently no rewetting drop that can provide sustained comfort and relief from dry eye symptoms for the length of an entire wearing day. The drops drain through the patient's nasolacrimal duct quickly after instillation, with the remainder absorbed by the cornea, conjunctiva and nasal mucosa. With at least 90% loss in each application, rewet-ting drops have to be re-instilled frequently throughout the day to provide effective comfort.49
Instilling rewetting drops in the eye prior to lens wear may increase the hours of comfortable wear time. Remember, methylcellulose-containing drops instilled upon lens insertion will neutralize the effects of the preservative on the ocular surface.50 Preservative-free rewetting drops will be beneficial for patients with sensitive eyes. The use of lubricant drops prior to lens wear and after lens removal may increase the hours of comfortable wear time.50
Meibomian gland dysfunction (MGD) is one of the major causes of evaporative dry eye and often is under-diagnosed by clinicians. Evaluation of the eyelids, meibomian gland orifices, the ocular surface and tear film (tear break-up time, tear meniscus height, debris in tears and Schirmer test) are necessary to administer appropriate treatment.
The novel LipiFlow device (TearScience) is a thermal pulsation system believed to effectively relieve the meibomian gland blockage. This tool applies a controlled amount of heat and massage to the eyelids, treating the upper and lower lids simultaneously. LipiView (TearScience) is an interferometer to evaluate lipid layer thickness. It is valuable to obtain the lipid layer thickness using LipiView before and after the treatment of MGD with the LipiFlow.
|A Checklist for Your Patient Visit|
Based on the evaluation, interventions such as lid hygiene techniques (lid scrubs and warm compresses), nutraceuticals (omega-3 fatty acids), rewetting drops/ artificial tears, and topical cyclospo-rine or doxycycline for dry eye and severe MGD may be required.
Because CLDE cannot easily be traced to one cause, preventing contact lens dropouts can be quite a challenge with patients suffering from this condition. Several factors, such as lens material and solutions, can play a role in exacerbating or improving dry eye symptoms. Clinicians should stay abreast of the latest research and developments to identify underlying causes of this condition and, ultimately, better treat their patients.
Disclosure: Over the past three years, CCLR has received research support or honoraria from the following companies: Alcon, Allergan, AMO, Bausch + Lomb, CIBA Vision, CooperVision, Essilor, Inspire, Johnson & Johnson, Menicon, OcuSense and Visioneering. Drs. Subbaraman and Srinivasan are not paid consultants, do not serve on an advisory board or own shares in any optometric company.
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