Dealing With Discomfort
An in-depth look at the epidemiology, diagnosis and treatment of contact lens-related dryness.
|Dr. Blackie is a charter member of the Ocular Surface Society of Optometry. She is the clinical research scientist for TearScience Inc. as well as for Korb & Associates in Boston.|
|Dr. Korb is cofounder and chief technical officer at TearScience and cofounder and director of research of Korb & Associates. He has a proprietary interest in Alcon.|
|Dr. Nichols is a professor at the University of Houston College of Optometry. She has stock options in TearLab and is a consultant/advisor to Alcon, Allergan, Bausch + Lomb and SarCode. She has received research support from Alcon Allergan, SarCode, TearLab and Vistakon.|
By Carol ine A. Blackie, OD, PhD, FAAO, Donald R. Korb, OD, FAAO, & Kelly Nichols, OD, MPH, PhD, FAAO, Dipl PH
Despite years of research and discovery, contact lens-related discomfort (CLD) remains highly prevalent, with an estimated 50 percent of U.S. lens wearers affected.1 Wearers frequently report general symptoms of dryness and discomfort, as well as specific complaints, such as grittiness and itchiness.2
A study involving patients in the United States and Canada found that 79 percent of contact lens wearers reported discomfort, and 77 percent reported dryness.3 Together these symptoms represent the number one reason why patients stop wearing their contact lenses, which is particularly significant when we consider that about 3.5 million people start wearing contact lenses each year, but approximately 2 to 3 million established lens wearers discontinue lens wear each year.4
Recognizing symptoms is relatively straightforward for clinicians, but identifying signs can be challenging. In a recent study, 23 percent of soft lens wearers with self-reported dryness showed no signs upon clinical examination using various standard tests.5 Furthermore, no single sign — significant corneal staining or reduced tear meniscus height, for example — was present in the majority of lens wearers.
This study supports the findings of previous studies: Symptoms, even when significant, frequently do not correlate with ocular signs. Young and colleagues5 also reported that some contact lens-related findings appear to be common among these patients, such as poor lens wetting, rapid tear breakup times and higher levels of deposits on lenses. They also found that asymptomatic individuals consistently report longer average comfortable lens-wearing times and less end-of-day discomfort. In contrast, patients with dryness symptoms reported, on average, 3.9 to 4.3+ hours of uncomfortable lens wear per day.
Epidemiology of CLD
Researchers have determined that more women than men have CLD,6 but the reasons for the higher prevalence among women are not fully understood. Some have hypothesized that hormones may play a role or that women are more likely to report symptoms.7
Studies reveal interesting information about age and contact lens wear. Richdale and colleagues,2 who correlated contact lens dropout with ocular discomfort and dryness, found in their study that older patients (by approximately 9.5 years) and those who had started contact lens wear at a later age (approximately 4 to 5 years later) were more likely to stop wearing contact lenses.
As we would expect, contact lens wearers bothered by symptoms will decrease wearing time and eventually discontinue lens wear.5 In a cross-sectional survey of 730 people, the permanent discontinuation rate was 24 percent,2 and a more recent survey of more than 4,000 Canadian patients found that about 23% of those surveyed had discontinued contact lens wear permanently.8
In our experience, some patients who have stopped wearing contact lenses, as well as some current lens wearers who have significant discomfort or visual symptoms, feel their quality of life has decreased, because many appreciate the improved vision and self-perception of physical appearance while wearing contact lenses.
Mechanisms Underlying Contact Lens Discomfort
Over the past 10 years, numerous mechanisms have been identified as key contributors to dryness in contact lens wearers.
•Altered Tear Film: Wearing a contact lens can produce a spectrum of ocular changes, including increased reflex tear secretion, deprivation of the wiping action of the lids over the covered ocular surfaces, elevated tear osmolarity and increased mucus production by non-goblet cells in the tarsal conjunctiva.9 As first reported by Tomlinson,10 however, the most important factor influencing discomfort with contemporary contact lenses is increased evaporation from the lens and ocular surfaces.9,10 The importance of prelens humidity was clinically demonstrated when 30 minutes of 100 percent humidity improved the prelens lipid layer thickness and comfort of hydrogel lenses.9
•Lens Wettability: A key factor in the biocompatibility of a contact lens is the tear film’s ability to adequately cover and maintain its integrity over the lens surface. Unfortunately, the surface of a contact lens lacks the mucus-attaching properties of the cornea and the ocular surfaces and is not well equipped to secure the foundational mucus layer(s) essential for forming all layers of the tear film. Thus, the tear film over the contact lens cannot duplicate the characteristics of the tear film over the cornea.
With contact lens wear, the lipid layer is rarely equivalent to the usual lipid layer of the tear film in thickness or other characteristics.11 Therefore, the rate of evaporation increases, tear film constituents denature on the lens surface and, in combination with the thinner pre- and postlens tear films, friction between the cornea and the contact lens, and the lid wiper and the contact lens is inevitable with resulting discomfort.12
•Corneal Desiccation: Because contact lens wear increases evaporation of the tear film, water is drawn from the tear film, thinning the postlens tear film. Consequently, the cornea may desiccate beneath a thin, high water content lens, leading to corneal epithelial defects and generalized discomfort.13
•Lid Wiper Epitheliopathy (LWE): When associated with contact lens wear, LWE in otherwise suitable contact lens wearers is most likely a result of the altered characteristics of the tear film between the lens and the lid wiper, compromising lubrication. An inadequate lipid layer is believed to play a significant role. Without adequate lubrication, the anterior surface of the contact lens is presented to the lid wiper at a rate on average of 12 to 15 blinks per minute,14 thousands of times a day. This activity can cause physical trauma, mechanical abrasion and inflammation of the epithelial cells of the lid wiper, resulting in symptoms of discomfort.12 Without an adequate lubricating layer, the lid wiper becomes a primary source of discomfort with contact lenses.
•Giant Papillary Conjunctivitis (GPC): With the increased use of disposable contact lenses, particularly daily disposables, GPC is less of an issue today, but it still may occur. Generally, it is related to the difficulty in keeping the lenses wet and clean. With compromised wettability or a buildup of deposits, the friction/trauma applied by the lens to the palpebral conjunctiva escalates, as does the likelihood of GPC.
•Blinking: Blinking is critical for wetting the ocular and contact lens surfaces, maintaining the lipid layer and minimizing evaporation, yet it is often overlooked in the clinical examination of a patient presenting with symptoms. Forceful blinking helps increase the lipid layer thickness, presumably by augmenting the expression from the meibomian glands.9 Contact lens wear affects the blink rate and amplitude, frequently inhibiting proper blinking and further exacerbating the detrimental effects of the contact lens on the tear film.9
•Meibomian Gland Dysfunction (MGD): The blink is considered the primary mechanism for expressing oil from the glands, thus chronically reduced blink rate and amplitude, which are frequently observed with contact lens wear, can result in a reduced meibomian gland function and secretion output within hours.15 MGD may lead to significant symptoms of ocular discomfort with contact lens wear.16-17 Reduced meibomian gland secretion contributes to contact lens discomfort, because evaporation from the tear film increases. This may initiate the cascade of LWE, which may further inhibit blinking. Similarly, if MGD develops during contact lens wear, discomfort may develop.
Although the mechanisms involved in ocular dryness associated with contact lens wear are numerous and complex, we know that MGD may well be the leading cause of dry eye18 and the most common cause of contact lens intolerance.19 These facts play an important role in diagnosing and managing CLD.
To appreciate the numerous tests required to evaluate the ocular surface, we must understand the effects of a contact lens on the eye. Even on a healthy ocular surface and tear film, a contact lens disrupts normal tear physiology through multiple mechanisms. For example, it will:20
• Increase prelens tear film thinning and breakup time
• Alter and thin the lipid layer
• Increase evaporation.
In addition, the edge of a contact lens introduces physical and rheological challenges, including those resulting from meniscus formation. The surface of a contact lens and adherent material may also traumatize the ocular and conjunctival surfaces and present immunological challenges.9 Thus, a thorough assessment of the patient’s symptom history, including management successes and failures, as well as a complete evaluation of the ocular surface, the eyelids, the blink and the interaction of the contact lens with the tear film and ocular environment is important for successful contact lens wear.
The following tests are often used in clinical practice:
•Questionnaires: The Contact Lens Dry Eye Questionnaire,21 the Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire22 or other surveys that ask about frequency and intensity of symptoms and late-day dryness may reveal important information.
•Tear Film Breakup Time: Measured before contact lens application and generally performed with fluorescein, an average of two or more readings in seconds should be taken with the biomicroscope. Tear film breakup time can also be measured using the Keratograph 5M (Oculus Inc.).
• Corneal Staining (fluorescein): Extent and location graded from 0 to 4.
• Conjunctival Staining (lissamine green): Extent and location graded from 0 to 4.
• Bulbar, Limbal and Eyelid Margin Hyperemia: Graded from 0 to 4.
• Palpebral Conjunctival Evaluation:
– Hyperemia, roughness, papillary response graded from 0 to 4.
– GPC graded from 0 to 4.
• Lid Wiper Epitheliopathy: Graded from 0 to 4.
• Meibomian Gland Evaluation:
– Function (e.g., oil availability upon light pressure).
– Secretion quality graded from 0 to 4.
– Appearance (e.g., orifice capping, telangiectasia, etc.).
• Meibography: Graded from 0 to 4; can be performed via transillumination or with a meibographer.
• Blink Completeness
• Tear Osmolarity: Scores greater than 307mOsm/L indicate dry eye.
• Contact Lens Surface Wettability: Graded from 0 to 4.
• Schirmer or Phenol Red Thread Test: Recorded in mm/min. or seconds.
For more insights, see “Clinical Patterns Aid Assessment.”
What Are We to Do?
While some patients experience CLD symptoms only in certain environments, such as the extremely low humidity in an airplane, others experience severe and constant symptoms that lead to termination of contact lens wear. Thus, while we can choose from numerous management strategies, we must be mindful that each patient is unique, and a tailored medical management approach, including ocular surface and lid assessment or if indicated, temporary or permanent cessation of lens wear, may be necessary. Treatment options include the following:
• Adjust Ambient and External Environment: Increased periocular humidity can have a dramatic and positive effect on the prelens tear film and contact lens comfort. Experiments with goggles to control evaporation have demonstrated decreased evaporation of the tear film thinning rates23 and reduced corneal epithelial erosions.24
These results continue to affirm what we know is the key to increasing ocular comfort during contact lens wear: a robust tear film with an adequate lipid layer and a healthy blink mechanism. A tear film that is adequate or marginally adequate without a contact lens may not be adequate in the presence of a contactlens. Work environment, room humidity, outdoor humidity/aridness and drying environments (heating/air conditioning) all play a role and can be discussed with patients. Indoor humidifiers and appropriate placement of computer monitors in the workplace can have a noticeable impact on a contact lens patient’s comfort and may be important in the overall management plan.
•Recommend Rewetting Drops: Rewetting drops may help relieve symptoms of dryness and improve for some individuals however, patients may view them as inconvenient if they must use them frequently. Numerous brands of contact lens rewetting drops are available to consumers. We believe eyecare professionals should recommend a specific product, including instructions for use.
•Change Lens Replacement Interval: Patients with CLD may benefit from replacing their lenses more frequently. When compared with frequent replacement (1 to 3 months) and 2-week replacement lenses, daily disposable hydrogel lenses showed fewer lens surface deposits, and wearers reported better comfort and overall satisfaction.25 Daily disposable hydrogel lenses may also help alleviate end-of-day dryness symptoms.26
• Change Lens Material: Certain polymers and surface treatments provide better wettability and a more normal prelens tear film than others. Refitting soft lens wearers who have CLD symptoms into silicone hydrogel materials may improve comfort. A study found that patients who had CLD symptoms and were wearing soft lenses experienced significantly improved dryness and comfort, and they increased their comfortable wearing time after they were refit with a silicone hydrogel material.6 In addition, we have found that patients may be more comfortable with a lower modulus silicone hydrogel lens, or even a conventional hydrogel lens, if they find a higher modulus silicone hydrogel lens uncomfortable. Additional recent studies have concluded that mechanical properties, such as the coefficient of friction of a lens, surface lubricity and lens stiffness are properties driving lens comfort.27,28 For instance, we know that a contact lens wearer will blink thousands of times a day, leading to a repeated mechanical interaction between the eyelid and contact lens surface and edge. There has been at least one study that has showed that a contact lens wearer has a reduction in the number of functional meibomian glands than nonlens wearers.29 One implication that the authors make is that the mechanical interaction between the lids and contact lens surface may lead to an atrophy of some of the meibomian glands. Thus, it seems reasonable to look at material characteristics such as coefficient of friction to help reduce the mechanical interaction and frictional drag between the lens and the lid as much as possible.
|Clinical Patterns Aid Assessment|
The broad range of ocular signs associated with CLD coupled with a potential lack of correlation between signs and symptoms underscore the need for a variety of tests to screen for CLD.5
An equally important part of the clinical workup is uncovering symptoms that may be associated with CLD. By routinely administering surveys or asking specific questions about each patient’s lens-wearing experience, you can obtain valuable information that reveals the presence and severity of dryness, for example:
• Reduced overall satisfaction with lens wear
•Inability to wear lenses as long as desired
•Use of rewetting drops
• Recent contact lens refitting to improve comfort or other symptoms.33
This information can help paint a clinical picture that points toward CLD, even when signs and symptoms fail to correlate.
•Change Care Regimen: When contact lens wearers complain of discomfort, practitioners often change contact lens disinfecting solutions. Researchers have found a particular brand of multipurpose solutions (MPS) may provide improved overall and end-of-day comfort and overall satisfaction for a lens wearer when compared to other MPS brands.4,30 Changing a patient’s care regimen from an MPS system to a hydrogen peroxide-based system may result in longer comfortable lens wear times.31 As with many aspects of clinical practice, each lens wearer responds differently to each solution. Therefore, an individualized approach may be necessary to find the most appropriate lens care solution.
•Discuss Essential Fatty Acid Supplementation: Patients with CLD have reported improved symptoms of dryness and increased overall comfort, and they have demonstrated improved tear meniscus height while using omega-3 and omega-6 dietary supplements.32
Adding to the CLD Armamentarium
Our understanding of CLD has advanced during the past several years. We can now direct our efforts toward alleviating these symptoms to multiple areas: new lens polymers, 1-day lenses, lens care products and methods to prevent evaporation, treatments for LWE, and, most importantly, the treatment of the meibomian glands to improve their secretion by various methods. With current treatments and new advances still in the pipeline, the future appears promising for reducing discomfort so that our patients can wear their contact lenses long term. CLS
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