Image: SimonQ / CC BY
Margaret Lam BOptom
NSW president, Cornea and Contact Lens Society of Australia
Visiting lecturer, School of Optometry, UNSW
Dry eye is a multifactorial ocular surface disease that can exist alone without the presence of a contact lens and as per the findings of the Dry Eye Workshop (DEWS) Report, contact lenses induce dry eye symptoms in as many as 50 per cent of wearers.1 Then, in a confusing twist, when patients suffer from severe ocular dryness, the condition can be relieved by the prescription of bandage and scleral contact lenses.
This article highlights a few findings from key landmark papers in this field that can be useful to guide dry eye and contact lens management in clinical practice.
Interaction between contact lenses and the tear film
The ‘dry eye’ associated with contact lens wear consists of many tear film alterations and dysfunctions that are created when the thickness of a contact lens is interspersed into the much thinner tear film system. These changes can add to what is termed contact lens discomfort (CLD).
The DEWS Report found that, parallel to dry eye in general, in the non-contact lens wearing population, a hormonal association is suggested for dry eyes, with female wearers reporting symptoms at a rate roughly 50 per cent higher than in men.2 Other associated factors include loss of corneal sensitivity, increased tear osmolarity, trigeminal denervation, shortened blink intervals and higher water content contact lenses.2 In addition, the presence of the contact lens causes pre-lens lipid layer thinning of the tear film to mimic an evaporative dry eye.2
The International Workshop on Meibomian Gland Dysfunction (MGD Workshop) is also an important landmark paper about dry eye.3 From this, we know to recognise that differences in lipid attraction among the different groups of contact lens polymers influence contact lens-related dry eye, and that non-ionic, low-water content contact lens materials minimise CLD.
In contact lens wearers, the rate of evaporation of the tear film is 1.2 to 2.6 times faster than the non-lens wearing eye.4,5,6 As a result of these changes, a tear film dysfunction that mimics an evaporative dry eye can result from contact lens wear.
The MGD Workshop also reconfirmed that the presence of the contact lens causes an increased instability of the tear film, and this leads to evaporative dryness, which then leads to higher rates of contact lens discomfort or intolerance.3,7,8,9
Contact lenses and how to minimise dry eye
Appropriate dry eye interventions for either dry eye or contact lens related dry eye sufferers should include the following findings from Workshop on Contact Lens Discomfort from the Tear Film and Ocular Surface Society (TFOS).10
Patients with contact lens discomfort require intervention similar to that for dry eye patients. In other words, the interventions for traditional evaporative dry eye would also be appropriate management for contact lens related dry eye sufferers. Dietary supplements, like omega-3 and omega-6, are appropriate to consider for this group. An examination of any medications that may induce dry eye symptoms would be appropriate.
However, although the role of topical anti-inflammatory medications, such as cyclosporin A 0.05% emulsion (or compounded solution), steroids and/or NSAIDs, may be useful, concerns about their use include preservative binding to the contact lens medium, opportunistic infection with topical steroid use and a lack of studies documenting their use in contact lens wearers.
Studies by Ramamoorthy and Nichols have found that switching to daily disposables can minimise dry eye symptoms.11
Improve the cleaning regimen
Optimise the combination of the contact lens and lens care solution combinations to minimise CLD. The Andrasko corneal staining grid is a useful clinical tool in assisting you with this (Figure 1).12 The employment of a hydrogen peroxide cleaning system over a multipurpose solution also assists by reducing CLD.
Figure 1. Based on the Andrasko corneal staining grid. Percentage of corneal staining area at two hours
Due diligence at the after-care appointment
Conducting after-care and thoroughly asking about any CLD symptoms allows the practitioner to prescribe changes in polymers to reduce their effects.
Change the lens material
It was well established that there was a considerable improvement in symptoms of contact lens comfort when traditional hydrogel patients were changed in their contact lens material to silicone hydrogels.13-18
However, new developments in contact lens technology have made significant inroads in reducing ocular dryness and reducing CLD further, and there is more exploration of the boundaries of when hydrogels and silicone hydrogels can be employed or even fused to improve CL comfort.
Alcon’s Dailies Total1 lenses are manufactured from a new material, Delfilcon A, which is the first water gradient contact lens. The material combines the benefits of a silicone hydrogel with high oxygen transmissibility and a hydrogel material with high water content for comfort. At the core of the Dailies Total1 contact lens is a silicone hydrogel material with a water content of 33 per cent. The surface of the lens is designed with a water content approaching 100 per cent at the interface with the tear film. A water gradient is created by cross-linked polymeric wetting agents that form a soft, hydrophilic surface gel, which is embedded into the core. The surface of the lens becomes highly lubricious.
Bausch and Lomb
Bausch and Lomb’s new Biotrue ONEday contact lenses are made from ‘Hypergel’ a ‘bio-inspired’ material that allows patients to feel hydrogel-like comfort through the material’s dehydration resistance that helps the contact lens retain moisture and optical shape while allowing oxygen to flow freely through the lens.
Other material developments include reworking hydrogel materials to have wetting agents that are partially embedded in the contact lens modulus to remain on the lens surface during lens wear. Others, such as CooperVision’s MyDay lenses, are made with a structural backbone of a long silicone chain polymer surrounded by smaller molecular chains of non-silicone polymers to envelope the silicone backbone. This reduces the amount of silicone exposed to the ocular surface, which seems to minimise any potential adverse silicone hydrogel responses but retains the advantages of silicone hydrogel properties. MyDay has certain unique combinations of hydrogel and silicone hydrogel properties for their lenses in their modulus and lens behaviour to minimise CLD.
Johnson & Johnson
The new 1-Day Acuvue Moist platform from Johnson & Johnson utilises ‘Lacreon Technology’, a process that the company says permanently embeds the wetting agent ‘polyvinylpyrrolidone (PVP) in the lens material. This PVP creates a cushion of moisture from the lens core to the lens surface to help reduce symptoms of CLD.
Chicken or egg?
Contact lenses and dry eye symptoms can appear to be a chicken or egg conundrum but thoughtful clinical management and diligent after-care should mean dry eye symptoms can be minimised in contact lens wear to prevent contact lens drop-out.
By examining each part of the equation to solve this puzzle, we can optimally manage the needs of our dry eye and contact lens patients to improve their quality of life.
About the CCLSA
The Cornea and Contact Lens Society of Australia was established in 1962 with the goal of providing education in the cornea and contact lens field. The CCLSA encourages collegiality in the eyecare industry through education, hosting conventions and lectures, and generates funds for scientific research.
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