Meibomian Gland Dysfunction

Meibomian gland dysfunction is a well recognised cause of dry eyes. Over the years, there has been a great deal of confusion regarding classification of this condition but recently, a detailed document has been produced that describes various aspects of this disease. This report was drafted by a panel of experts for the Tear, Film and Ocular Surface Society (TFOS) and provides a detailed guideline on classification and treatment of meibomian gland dysfunction.

It is an unfortunate fact that this condition is a rather under-recognised one. These new guidelines however have shed some interesting light on this condition. There are certain aspects of meibomian gland dysfunction that have an impact on the outcomes following anterior segment surgery. It is believed that the final lead to with regards to a patient’s vision depends primarily on the status of the film of tears from the eyeball. It is essential to have a good ocular surface in order for any surgery to be successful.

Another aspect that has been noticed with regards to surgical outcomes is the status of the tear film and its irregularities. This can cause inaccurate readings of the power of the eye which can in turn lead to in an error in prescription of intraocular lenses. In adds to, patients who have meibomian gland dysfunction are at higher risk of developing infections and inflammation of the eye following cataract surgery.

Essential terminology

There are certain aspects of meibomian gland dysfunction that one needs to be aware of. These are closely related to the pathogenesis and pathophysiology of this condition. Below is a list of some of the commonly mentioned terms in the genesis of MGD.

1. Blepharitis - this is a clinical condition that is characterised by inflammation of the entire eyelid. Inflammation that only involves the margin of the island is called marginal blepharitis.
2. Anterior blepharitis refers to inflammation of the eyelid that lies in front of the gray line. Inflammation here can extend to the posterior eyelid margin.
3. Posterior blepharitis refers to inflammation of the posterior aspect of the eyelid margin.
4. Meibomian gland dysfunction is defined as a chronic abnormality that affects meibomian glands and one that is characterised by obstruction of the terminal ducts and an alteration in the secretion of the glands. In essence, it results in a destruction of the eyelid films and can make the eye rather dry.

The meibomian gland

The meibomian glands are sspecializedglands that are present at the removal of the eyelids. They are sebaceous glands that are responsible for the secretion of meibum, and oily substance that allows the tear film to stay on the eyeball and prevents it from getting evaporated. In adds to, meibum prevents tears from pouring out of the eyeball onto the cheeks by forming a barrier between the eyelids and the eyeball.

The meibomian glands are located within the castle plates of the eyelids. Anatomically, there are around 50 glands in the upper eyelid and around 25 meibomian glands in the lower eyelids. The secretions from the meibomian glands are sebaceous and typically rich in lipids. Overall, research has shown that the meibomian gland secretions contain over 90 different kinds of proteins.

Pathogenesis

Meibomian gland dysfunction results from reduced secretion of meibum from the meibomian glands or from excessive secretions as well. The former is called a low delivery state while the latter is called a high delivery state.

As is evident from the discussion above, meibomian glands are essential to keep the eyes healthy. Unfortunately, in the event that these glands become dysfunctional, the eyes can become dry. Furthermore, inflammation of the meibomian glands, may be called meibomitis, can lead to in obstruction of the glands by its own secretions. This results in bacterial overgrowth, increased formation of free fatty acids, irritation of the eyes and the development of dry eyes and keratopathy.

Diagnosing eyelid problems

There are certain ways through which meibomian gland dysfunction can be identified. A slit lamp examination or simple meibum analysis could be sufficient. Once meibomian gland dysfunction has been detected, patients could require some form of surgery once this has been controlled through medical measures.

Effect on quality of life

There is concern that MGD can affect a patient’s quality of life rather substantially. Patients can struggle to wear contact lenses and could even find that their eyes look rather unsightly and puffy. This can have an impact on their personal and professional lives. 

Staging and Treatment of Meibomian Gland Dysfunction

Stage 1

Symptoms

• No symptoms of ocular discomfort, itching or photophobia
• Clinical signs of MGD based on gland expression 
  • Minimally altered secretions: Grade  ≥   2 to
  • No ocular surface staining

Treatment

• Inform patient about MGD, the potential impact of diet and the effect of work/home environments on tear evaporation, and the possible drying effect of certain systemic medications
• Consider eyelid hygiene including warming/expression as described below (±) 

Stage 2

Symptoms

• Minimal to mild symptoms of ocular discomfort, itching or photophobia
• Minimal to mild MGD clinical signs
      Scattered lid margin features
      Mildly altered secretions: Grade ≥ 4 to <8
      Expressibility: 1
• None to limited ocular surface staining(DEWS grade 0–7; Oxford grade 0–3)

Treatment

• Advise patient on improving ambient humidity; optimizing workstations and increasing dietary omega-3 fatty acid intake (±)
• Institute eyelid hygiene with eyelid warming (a minimum of four minutes, once or twice daily) followed by moderate to firm massage and expression of MG secretions (+)
• All the above, plus (±)
      Artificial lubricants (for frequent use, nonpreserved preferred)
      Topical emollient lubricant or liposomal spray
      Topical azithromycin
      Consider oral tetracycline derivatives

Stage 3

Symptoms

• Moderate symptoms of ocular discomfort, itching or photophobia with limitations of activities
• Moderate MGD clinical signs
       ↑  lid margin features: plugging, vascularity
      Moderately altered secretions: Grade ≥  8 to <13
      Expressibility: 2
• Mild to moderate conjunctival and peripheral corneal staining, often inferior (DEWS grade 8–23; Oxford grade 4–10)

Treatment

• All the above, plus
      Oral tetracycline derivatives (+)
      Lubricant ointment at bedtime (±)
      Anti-inflammatory therapy for dry eye as indicated (±)

Stage 4

Symptoms

• Marked symptoms of ocular discomfort, itching or photophobia with definite limitations of activities
• MGD clinical signs
     ↑  lid margin features: dropout, displacement
     Severely altered secretions: Grade ≥ 13
     Expressibility: 3
• Increased conjunctival and corneal staining,including central staining (DEWS grade 24–33; Oxford grade 11–15)
• ↑ Signs of inflammation: e.g., ≥ moderate conjunctival hyperemia, phlyctenules

Treatment

• All the above, plus
      Anti-inflammatory therapy for dry eye (+)
• KEY
  (+) = supported by evidence; (±) = limited or emerging evidence.
• Meibum quality is assessed in each of 8 glands of the central third of the lower lid on a 0–3 scale for each gland: 0=clear meibum; 1=cloudy meibum; 2=cloudy with debris (granular); 3=thick, like toothpaste (range 0–24).
• Expressibility of meibum is assessed from 5 glands: 0= all glands expressible; 1=3–4 glands expressible; 2=1–2 glands expressible; 3=no glands expressible. This can be assessed in the lower or upper lid.
• Numerical staining scores refer to a summed score of staining of the exposed cornea and conjunctiva. The Oxford scale has a range of 0–15 and the DEWS scale has a range of 0–33.