Posterior Etiologies of Dry Eye
By Leo Semes, OD, FAAO
A contributor to evaporative dry eye is an incomplete or poorly formed oily layer of the tear film. This can result from meibomian gland dysfunction (MGD), a frequently encountered clinical condition and a significant cause of evaporative dry eye. Patients experience discomfort, visual disturbance, and contact lens intolerance.
Despite the early description of the anatomy and physiology of the meibomian gland, recognition of MGD and therapeutic options to treat it have been limited.
Attempting to encourage meibomian gland secretion may be futile. A recent histological study found that aging may reduce meibomian gland counts. In a group of patients who underwent eyelid surgery, it was found that the older patients had fewer meibomian glands (Nien et al, 2011). The authors concluded that aging may lead to acinar atrophy and to development of an age-related hyposecretory MGD. The study included data from patients ranging from 19 years to 85 years with no controls.
Other evidence for meibomian gland “dropout” comes from a 2008 study by Korb and Blackie that looked at more than 130 symptomatic patients to evaluate functioning meibomian gland units. The authors reported a correlation between the number of meibomian gland yielding liquid secretion (MGYLS) in the lower eyelid and dry eye symptoms. In addition, the number of MGYLS varies significantly across the lower eyelid, with the highest number of MGYLS in the nasal third and the lowest number of MGYLS in the temporal third of the lower eyelid. What should be significant for clinicians here is that careful evaluation of the lower lid is critical for diagnostic purposes.
In a small group of patients whose tear evaporation rates were measured, those who had keratoconjunctivitis sicca (KCS) as well as those who had KCS and MGD demonstrated meibomian gland dropout that was correlated with increased tear film evaporation (Arciniega et al, 2011). Meibography was used to assess this significant dropout.
One simple suggested treatment for MGD is to use warm compresses for five minutes. The initial five minutes improved tear film lipid layer thickness (TFLLT) by 120 percent (Olson et al, 2003). Longer application of heat did not significantly increase TFLLT. Since that brief report in 2003, several additional approaches have emerged.
What evidence is there for treatments beyond five minutes of warm compresses? The warm compresses in conjunction with massage actually offer relief for up to three months (Korb and Blackie, 2008). Application using a proprietary device for a single 12-minute treatment produced these results.
Another noninvasive protocol involves azithromycin applied topically. Results appearing in April 2011 suggested that the signs and symptoms associated with posterior blepharitis improved following a 30-day treatment strategy (Opitz and Tyler, 2011). Unfortunately, no controls, sham procedures, or alternative treatments were evaluated. But, importantly, this study establishes safety and efficacy for topical azithromycin.
Finally, an invasive procedure that involves probing of the meibomian glands has been described (Maskin, 2010). This procedure also uses a proprietary device. An initial report found a significant improvement in signs and symptoms among a small number of patients.
If interested you can view a narrated video of the procedure at eyetube.net/series/new-mix-tape-created-7222010-64407-pm/intraductal-meibomian-gland-probing/. An advantage of the procedure is to determine integrity of the meibomian glands. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #188.
Dr. Semes is a professor of optometry at the UAB School of Optometry. He is also a consultant or advisor to Alcon, Allergan, Optovue, and Zeiss.