Comparing Dry Eye and CLIDE
By William L. Miller, OD, PhD, FAAO
Dry eye complaints are fairly common in our contact lens-wearing patients. Some symptoms are episodic and occur infrequently in a given day. Other patients complain of more frequent dry eye symptoms or report end-of-the-day comfort issues. Your patient may experience symptoms only under certain environmental conditions, such as extended computer work or air travel.
Given its prevalence and potential interference with contact lens wear, it bodes investigating the differences between contact lens-induced dry eye (CLIDE) and other dry eye conditions. According to the 2007 Dry Eye Workshop Report (DEWS), contact lenses represent a categorically separate dry eye. The report distinguishes CLIDE as an evaporative dry eye caused by extrinsic (ocular surface effect) factors. This is different from other forms of dry eye, such as intrinsic evaporative or aqueous deficient.
Uncovering the root cause of dry eye is important in determining the long-term treatment. From the patient's point of view, symptoms are similar regardless of the underlying cause; especially in the mild-to-moderate category. The primary difference in CLIDE patients is the rapid diminution of symptoms when the lenses are removed, although some patients experience lingering symptoms. We know surface deposition and material properties can influence dry eye. Surface deposition causes tear film disruption, increasing pre-lens tear film breakup. Material properties may negatively affect lens surface wettability. For example, high water content and thinner materials may demonstrate higher evaporation profiles than their counterparts. In addition, some lenses, depending on their ionic flux/water diffusion, may lead to dehydration staining in the inferior cornea. At least one report (Chalmers, 2008) suggested that refitting symptomatic hydrogel contact lens wearers into silicone hydrogel lenses may eliminate dry eye complaints.
Thus, it's important to evaluate contact lens wettability in vivo to ascertain its suitability for each of our patients. To do so, you may employ high magnification, diffuse light observation with a biomicroscope or Tearscope, or observing the characteristics of the pre-lens tear film. In addition, diagnostic predictors, such as lid parallel conjunctival folds, non-invasive tear break-up time and the Ocular Surface Disease Index questionnaire (Pult, 2009), may be useful to help identify patients who have a higher risk of experiencing CLIDE.
Some of your treatment modalities may be similar, if not identical, to treating other forms of dry eye. These include punctal occlusion, adequate systemic hydration and nutraceuticals. However, in the case of CLIDE, you must also consider material and/or solution changes as well as tear supplements suitable and approved for contact lenses.
CLIDE patients should avoid topical drops that include certain preservatives (for example, BAK), which can cause tear film disruption and ocular surface damage. In addition, with the aid of sodium fluorescein and a barrier filter, you should identify possible care solution sensitivities, since these may mimic dry eye due to their alteration of the ocular surface. You should monitor for pan-corneal staining, especially circumcorneal, to uncover solution-lens incompatibilities that may cause dry eye discomfort.
You can recommend a tear supplement that is safe for use with contact lenses, but don't forget the usefulness of other tear supplements for times when your patient isn't wearing contact lenses, especially overnight. You should also educate patients at each visit about the proper cleaning, disinfection and care of their lenses to decrease the likelihood of deposit-related tear film instability. Daily disposable contact lenses may be indicated for patients who experience heavy deposits. CLS
For references, please visit www.clspectrum.com/references.asp and click on document SE2011.
Dr. Miller is an associate professor and chair of the Clinical Sciences Department at the University of Houston College of Optometry. He is a member of the American Optometric Association and serves on its Journal Review Board. You can reach him at firstname.lastname@example.org.