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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 result 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 result in an error in prescription of intraocular lenses. In addition, 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 addition, 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 result 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 gt_eql  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 gt_eql 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
        up_arrow lid margin features: plugging, vascularity
        Moderately altered secretions: Grade gt_eql  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
       up_arrow lid margin features: dropout, displacement
       Severely altered secretions: Grade gt_eql 13
       Expressibility: 3
  • Increased conjunctival and corneal staining,including central staining (DEWS grade 24–33; Oxford grade 11–15)
  • up_arrow Signs of inflammation: e.g., gt_eql 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.