Lens-related Dry eye
Managing Contact Lens-Related Dry Eye
Resolving this common condition is essential to reducing the number of contact lens dropouts.
|Dr. Pult is a CEO of the optometric practices of Horst Riede GmbH, Weinheim, Germany, and an investigator of the independent research group “Dr Heiko Pult – Optometry and Vision Research,” Weinheim, Germany. He is also involved in contact lens and anterior eye research at Cardiff University in the United Kingdom. He is a lecturer and independent investigator for several research groups, companies, and schools.|
|Dr. Miller is an associate professor and chair of the Clinical Sciences Department at the University of Houston College of Optometry. He is a consultant or advisor to Alcon and Vistakon and has received research funding from Alcon and CooperVision and lecture or authorship honoraria from Alcon and B+L. You can reach him at firstname.lastname@example.org.|
By Heiko Pult, PhD, MSc, FAAO, FBCLA, FEAAO, & William L. Miller, OD, MS, PhD, FAAO
About 50 percent of lens wearers experience contact lens-related dry eye (CLDE) (Nichols et al, 2002; Begley et al, 2000; Nichols and Sinnott, 2011) (Figure 1). Discomfort and dryness during wear appear to be the major causes of discontinuing contact lens wear (Richdale et al, 2007). Approximately 50 percent of patients who drop out of contact lens wear in the United Kingdom and 75 percent in the United States do so because of discomfort related to contact lens wear (Pritchard, 2001). Furthermore, 12 percent of new contact lens patients discontinue lens wear within five years due to these symptoms (Pritchard et al, 1999).
Figure 1. A poorly wetting surface of a silicone hydrogel contact lens.
Many factors that contribute to lens discomfort (Table 1) (Evans and Pult, 2012) need to be considered in CLDE management. This article will discuss these factors and how to manage them.
Check for Pre-Existing Dry Eye
For patients who are experiencing discomfort during contact lens wear, first diagnose and address any pre-existing dry eye before making any changes to the contact lenses, care solutions, or wearing schedule (Pult, 2011; Sindt and Longmuir, 2007). There are two categories of dry eye. Aqueous deficient dry eye (ADDE) results from insufficient production of tears and is often addressed with either punctal occlusion (Giovagnoli and Graham, 1992) or lubrication of the ocular surface by instilling topical wetting agents (Ramamoorthy et al, 2008).
The most common dry eye category appears to be evaporative dry eye (EDE), which commonly results from a lipid abnormality due to meibomian gland dysfunction (MGD) (Giannoni and Nichols, 2012; Nichols et al, 2011). MGD is a chronic, diffuse abnormality of the meibomian glands, commonly characterized by terminal duct obstruction (Figure 2) and/or qualitative/quantitative changes in the glandular secretion. This may cause an altered tear film, symptoms of eye irritation, clinically apparent inflammation, and ocular surface disease (Nelson et al, 2011).
Figure 2. Inspissated meibomian gland orifices in a patient who has meibomian gland dysfunction.
Liposomal eye sprays are a promising, newer treatment option for EDE (Craig et al, 2010; Pult et al, 2012), and older, conservative therapies such as daily application of warm and moist compresses followed by appropriate lid hygiene can help improve MGD (Spiteri et al, 2007; Geerling et al, 2011). The lipid layer is an important component in stabilizing the tear film (King-Smith et al, 2009). Meibomian gland dropout is significantly correlated to reduced lipid layer thickness, faster non-invasive tear breakup time, and dry eye symptoms (Pult and Riede-Pult, 2012) as well as to contact lens discomfort.
To Change or Not to Change the Contact Lens
A contact lens patient’s comfort can be contact lensspecific and may depend on the material’s surface and bulk properties, lens design, and modality of use. Refitting hydrogel contact lens wearers into a silicone hydrogel (SiHy) lens may have the potential to improve CLDE symptoms, but this remains controversial in the literature and among practitioners (Guillon, 2013; Schafer et al, 2007). Lens comfort may also be significantly influenced by the lens replacement frequency and the lens care system used (Guillon, 2013). Changes to the contact lens diameter, edge design, back surface design, and thickness may help improve comfort (Dumbleton, 2002; Santodomingo-Rubido and Rubido-Crespo, 2008).
Brennan et al (2009) reported that the coefficient of friction (CoF) was the main parameter related to end-of-day comfort, followed by the material modulus and water content in a SiHy contact lens study. Internal wetting agents were reported to improve pre-lens tear film stability, vision, CoF, and consequently, wearing comfort (Wolffson et al, 2010; Peterson et al, 2006; Koh et al, 2008).
Because CoF is an in vitro test, in vivo assessments conduring a blink cycle are likely to be different due to variations in individual tear film properties of contact lens wearers, blink rates, and lid pressure (Berry et al, 2012). However, observed signs such as lid parallel conjunctival epithelial folds (LIPCOFs) and lid wiper epitheliopathy (LWE) may be clinical—and thus in vivo—indicators of friction. Both may be good predictors of successful contact lens wear in both new and experienced contact lens wearers (Pult et al, 2008; Pult et al, 2009).
|Factors Associated With Contact Lens-Related Dry Eye|
PRE-EXISTING DRY EYE
• Reduced tear volume (tear meniscus height)
– Meibomian gland dysfunction
• Ocular surface physiology (corneal and conjunctival staining) Task-related
– Poor wettability
• High modulus
• Low humidity
• Preservatives in eye drops and/or care regimens
LIPCOFs manifest as folds in the lateral, lower quadrant of the bulbar conjunctiva, parallel to the lower lid margin (Höh et al, 1995) (Figure 3). Evaluate LIPCOFs in the area perpendicular to the temporal and nasal limbus on the bulbar conjunctiva above the lower lid using a slit lamp biomicroscope (no lens, white light, no fluorescein) with 18x to 27x magnification as necessary. Table 2 shows the optimized grading scale (Pult et al, 2008). Make sure to differentiate between LIPCOFs and micro-folds. A LIPCOF thickness is commonly 0.08mm (around half of the normal tear meniscus height), while a micro-fold is much smaller at approximately 0.02mm (Pult and Riede-Pult, 2011). LIPCOFs may share the same etiology as conjunctivochalasis (Pult et al, 2011; Watanabe et al, 2004; Wang et al, 2007), representing an initial or sub-clinical presentation as well as not being influenced by the force of a blink.
Figure 3. Temporal LIPCOF grade 2.
Optimized LIPCOF Grading Scale
|No conjunctival folds||0|
|One permanent and clear parallel fold||1|
|Two permanent and clear parallel folds (normally lower than 0.2mm)||2|
|More than two permanent and clear parallel folds (normally higher than 0.2mm)||3|
LWE is a clinically observable alteration in the epithelium of the posterior portion of the lid margin, named the lid wiper. LWE is visible using a combination of instilled 1% lissamine green and 2% fluorescein, and is evaluated for the upper lid only. Instill both dyes a second time after five minutes (Korb et al, 2006). LWE is classified by width and length (Pult et al, 2008; Berry et al, 2008; Korb et al, 2002) (Table 3), and care should be taken to differentiate between physiological staining associated with Marx’s line (Pult et al, 2010; Korb and Blackie, 2010) and staining of the lid wiper (Korb et al, 2002; Korb et al, 2005) (Figure 4).
Figure 4. Line of Marx (A) versus lid wiper epitheliopathy (B).
Classification of Lid Wiper Epitheliopathy
|HORIZONTAL LENGTH OF STAINING GRADE||GRADE|
|2mm to 4mm||1|
|5mm to 9mm||2|
|SAGITTAL WIDTH OF STAINING GRADE|
|25 percent of the width of wiper||0|
|25 percent to 50 percent of the width of wiper||1|
|50 percent to 75 percent of the width of wiper||2|
|>75 percent of the width of wiper||3|
LWE is caused by an insufficient tear film, which results in constant interaction between the ocular surface and lid wiper (Pult et al, 2010). Therefore, the lid wiper is continually subjected to trauma throughout the excursive movements of the eyelid (Korb et al, 2002; Korb et al, 2005). Based on a strong correlation between LWE and LIPCOFs, they may share a common frictional origin (Pult et al, 2008; Berry et al, 2008). Therefore, LIPCOFs and LWE are considered representations of indirect, in-vivo measures of ocular surface friction during blinking (Pult et al, 2010).
Patients displaying evidence of such ocular surface abnormalities should be fitted or refitted with lenses that have a low CoF and improved wettability. However, you must consider the number of different methodologies used to establish referent frictional values and wettability for individual lens materials. Consequently, you might consider fitting two different lenses, one to each eye, to observe any subjective and objective differences between them. LWE appears to be a quick indicator, becoming evident after two to three weeks, while LIPCOFs are assumed to provide more longitudinal information (Pult et al, 2010).
Lens Care Solution Considerations
A contact lens care system may be as important to comfortable lens wear as is the lens itself.
Many newer lens care solutions contain wetting agents to promote comfort upon application and to maintain wettability throughout the day. Some contain hyaluronic acid, while Opti-Free PureMoist (Alcon) contains a HydraGlyde Moisture Matrix to enhance surface hydrophilicity and thereby supply a continuous shield of moisture on the lens surface (Evans and Pult, 2012).
It is important to always bear in mind that cytotoxicity of some disinfecting agents and preservatives can cause discomfort and symptoms of dryness in selected contact lens wearers (Lievens et al, 2006). Therefore, lenses soaked in such care solutions need to be rinsed with a nonpreserved saline solution before wear to avoid potential cytotoxic effects. Alternatively, you can advise patients to switch to a care system that uses a different preservative. Additionally, preservative-free care solutions or one-step peroxide systems can be useful problem-solvers for these sensitive patients (Evans and Pult, 2012; Pult, 2012). Even though peroxide-based systems are used less frequently (Efron and Morgan, 2008), they cause fewer solution-related dry eye symptoms, are not toxic once neutralized, and are compatible with most soft contact lens materials (Carnt et al, 2007; Dalton et al, 2008; Dursun et al, 2002).
Dryness symptoms appear to be the major cause of contact lens discomfort, but dry eye symptoms in lens wearers are multifactorial. You must first address any pre-existing dry eye, the most likely cause of which is typically MGD. LWE and LIPCOFs may be useful in evaluating dry eye and the CoF in clinical routine.
The success our contact lens patients’ experience will depend on how well we address the issues of CLDE. Current approaches may include refitting symptomatic hydrogel contact lens wearers into a SiHy material that has a low CoF, improving contact lens surface and bulk wettability, and avoiding or switching preservatives.
For references, please visit www.clspectrum.com/references. asp and click on document #212.