Dry Eye Dx and Tx
Lens Intolerance and MGD
By Eric E. Schmidt, OD
It is estimated that between 30 percent and 50 percent of lens wearers experience symptoms of dry eye. Proposed etiologies for contact lens-induced dry eye include inflammation, decreased surface wetting of the contact lens itself, increased tear film osmolarity, and increased evaporation of the pre-ocular tear film.
Dry eye symptoms greatly reduce lens wearing time and can lead to contact lens intolerance. As symptoms become more severe, lens wearers often take a hiatus from wearing their contact lenses. When this occurs, patients are less likely to return to full-time lens wear and may even drop out completely. Even changing to different contact lens modalities, such as to daily disposable lenses, may not be successful. Thus, preemptive recognition and aggressive intervention of the signs and symptoms of contact lens-related dry eye will benefit patients' ocular health as well as allow them to stay in contact lenses for a longer period of time.
The Effects of MGD
Although the signs and symptoms of dry eye are rather consistent, the etiologies vary greatly. One recognized cause of lens-related dry eye is meibomian gland dysfunction (MGD). Ong and Larke (1990) showed that contact lens wear can lead to dysfunction of meibomian glands. Their study showed that MGD was abnormally high among lens wearers and that this was the case regardless of the type of contact lenses worn (GP or soft). The authors postulated that the mechanical trauma on the lid margin caused by the contact lenses during blinking caused a chronic form of irritation that led to MGD.
Recently, Arita et al (2009) used a technique to perform non-contact meibography that enabled them to examine meibomian glands morphologically. This group graded meibomian gland loss on a 0-to-3 scale. The “meiboscore” of lens wearers was statistically significantly higher than the meiboscores of the non-lens-wearing control group. Though the average age of the lens wearers in the study was 31.8 years, their average meiboscore was similar to that of a 60- to 69-year-old non-lens wearer. The only variable that was significantly associated with the increased meiboscore was the presence and duration of contact lens wear.
This study also showed that tear film breakup time was less in lens wearers than in non-wearers and that a greater prevalence of superficial punctate keratitis was seen in the lens-wearing group. It was hypothesized that the simple presence of the contact lenses caused the accelerated meibomian gland dropout and the resulting dry eye symptoms and signs.
A Possible Therapy
Nichols et al presented a poster last month at ARVO looking at the ability of topical azithromycin (Azasite, Inspire Pharmaceuticals) to increase comfortable wearing time in contact lens patients who have dry eye symptoms. This study utilized a Contact Lens Dry Eye Questionnaire to subjectively assess contact lens comfort and wearing time when using artificial tears or Azasite. After four weeks, the Azasite group showed a significant increase of at least two hours of comfortable wearing time from baseline as compared to the artificial tear arm of the study. Subject-related ocular dryness was also significantly improved from baseline in the Azasite arm as compared to the control arm of the study.
It is important to understand that MGD can be caused by contact lens wear and can lead to dry eye symptoms. Treatment with a pharmaceutical has been shown to increase contact lens wearing time and to decrease the symptoms associated with lens-related dry eye. CLS
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #187.
Dr. Schmidt is the president of Omni Eye Specialists, a multispecialty practice headquartered in Wilmington, North Carolina. He specializes in the treatment of ocular disease with a special interest in glaucoma and neuro-ophthalmic disease. He is an adjunct professor at various Colleges of Optometry. He is a consultant or advisor to Ista Pharmaceuticals, Allergan, and Inspire Pharmaceuticals and has received an educational grant or contract from Allergan and Alcon.