Meibomian gland dysfunction (MGD) is one of the most common causes of an abnormality of the tear film lipid layer and evaporative dry eye.^1–5 Numerous risk factors of MGD are reported (Table 1).⁶ Its prevalence varies between countries from 20% to 60%, with the highest rate in Japan.⁶ MGD is a chronic, diffuse abnormality of the meibomian glands, commonly characterized by terminal duct obstruction and/or qualitative/quantitative changes in the glandular secretion.⁷ This may result in alteration of the tear film, symptoms of eye irritation, clinically apparent inflammation and ocular surface disease.⁷

MGD results in stasis of meibum inside the glands, dilatation of the ductal system and loss of glandular tissue (gland dropout) (Figure 1).⁵ It is recommended that the diagnosis of MGD is made by assessing ocular symptoms, lid morphology, meibomian gland mass, gland expressibility, lipid layer thickness and meibography.¹

Meibography is the only clinically in vivo technique to visualize the morphology of the meibomian glands. When using this method, the structure of the meibomian glands, including the ducts and acini, can be observed.^8–16 Meibography provides photographic documentation of the meibomian gland under specialized illumination techniques.¹⁷ This article is aimed to summarize recent development and investigation in meibography and its clinical relevance.

Meibography principles

There are two principles in meibography. One is the transillumination of the everted lid^11,18,19 the other is direct illumination, named the non-contact meibography.^15,20–22 In the transillumination technique, the eyelid is everted over a light source.^11,13,23 The most basic version uses white light, for example from a Finoff transilluminator. This is applied to the cutaneous side of the everted eyelid and allows observation from the palpebral conjunctival surface. Tapie²⁴ was probably first describing evaluation of meibomian glands by transilluminating lids in 1977. He also captured the meibomian glands using infrared film (IR). Jester et al. ¹⁶ adapted the biosmicroscopic and photographic techniques to improve upon Tapie's technique.¹⁶ Subsequently many other groups have used the transillumination IR techniques in meibomian gland observation.^11,18,19,25

Figure 1: Hypothesized long-term changes of meibomian glands in MGD (1. Increased viscosity of the meibomian oil; 2. Orifice plugging and duct obstruction (hyper-keratinisation); 3. Stasis and dilatation of glands; 4. Glands atrophy and dropout)

Arita et al. ^15,20–22 were the first describing noncontact meibography in 2008. In the non-contact technique, a camera and IR light source do not touch the patient during the meibography procedure.¹⁵ Their non-contact meibograph¹⁵ consists of a slit-lamp microscope equipped with an IR charge-coupled (CCD) device video camera and an IR transmitting filter¹⁵ to allow the observation of the everted lid. The light and dark contrast of the meibomian glands is opposite that of the transillumination technique in that they appear light instead of dark.