discovering dry eye

Imaging the Meibomian Glands: An Insider's View

discovering dry eye
Imaging the Meibomian Glands: An Insider's View

In every discussion of dry eye, the meibomian glands are mentioned. These small and highly specialized glands remain an enigma. The lipid they produce is integral to tear film function. Clinically, meibomian gland disease may accompany aqueous deficient dry eye, or may be at the root of the problem in the form of a pure evaporative dry eye. Which came first­dry eye or meibomian gland disease?

Figure 1. Healthy meibomian glands viewed with meibography.

Figure 2. Partial meibomian glands seen in our patient.

The lipid secreted by the meibomian glands retards evaporation from the preocular surface. As the lids open, meibomian oil is drawn over the tear film from a pooled reservoir at the lid margin. The continual replenishment of the lipid layer maintains a stable tear film. The lower lid has 30 to 40 glands, and the upper lid shows 20 to 25 glands. At any given time, about 45 percent of the glands are active. Meibomian gland acinar walls thicken with age, and decreasing androgen hormonal levels have been associated with decreased gland function. Knowing all that, why are we not better at classifying meibomian gland function?

Over the last 25 years, in vivo biomicroscopy has evolved, allowing clinical imaging of the meibomian glands. Jester and coworkers (1982) were the first to describe the technique which involves transilluminating the lid with near infrared light for direct examination of the glands through the palpebral conjunctiva. At that time, photography of the glands was performed using high-speed infrared film; however, Mathers and Daley (1994) have more recently described video technology which provides an instantaneous record of the glands and potentially higher resolution than still film. This is the technique we have employed in our laboratory (Figure 1).

Case Study

A 76-year old female presented for evaluation of ocular surface disease. She reported symptoms of ocular irritation over the past three months, including ocular discomfort with prolonged reading. She was not currently using hormone replacement therapy, and she was not a contact lens wearer. Ocular surface evaluation revealed stenosis of the meibomian gland orifices and normal lid margins. The tear prism showed mild debris, and her blink function was normal. Tear break-up time was reduced and showed a streaky, linear pattern. Diffuse Grade 1 fluorescein staining was seen in the inferior region of the cornea OU, and Grade 1 lissamine green stain was seen adjacent to the caruncle OU. Schirmer test was normal. Tear film osmolarity was 325mOsm. We imaged her meibomian glands with infrared video meibography (Figure 2).

According to Mathers (1991), this patient would be diagnosed with obstructive meibomian gland disease characterized by low secretion and gland drop-out (stenosis), which is supported by reduced TBUT, partial meibomian glands seen via meibography and increased tear osmolarity. Clinically, she is symptomatic. The view of the meibomian glands with infrared video meibography may help us to understand this complex process.

Dr. Kelly Nichols is assistant professor of clinical optometry at The Ohio State University College of Optometry in the area of dry eye research. Dr. Jason Nichols is a senior research associate at The Ohio State University College of Optometry.