Dry Eye disease

What is Dry Eye Disease?

Dry Eye Disease is a disease of the ocular surface and tears which causes symptoms such as gritty, sandy, red eyes, stinging pain and even blurry vision. In dry eye, a multitude of causes results in an unstable tear film that spreads poorly across the surface of the eye. Long term, this tear film instability can cause inflammation and permanent damage to the ocular surface.  Dry eye disease significantly and negatively impacts quality of life and is a major public health concern.

Dry Eye Disease affects 15%-40% of the total population at any point in time [1].  The two types of Dry Eye Disease are (1) Tear Deficient Dry Eye: where there is reduced tear production and (2) Evaporative Dry Eye: where the tear film does not spread across and remain on the ocular surface long enough to provide adequate lubrication and nourishment. Of these types, 85% of dry eye is evaporative [3].

There are specialised glands in the eyelids, known as Meibomian glands, which secrete oil known as meibum. Meibum is critical in slowing tear film evaporation.

 

Meibomian Glands are found in the eyelids

 

Meibomian Gland Dysfunction refers to the blockage and eventual decay of these glands from a change in meibum quality. Meibum should flow freely from these glands, with the consistency of olive oil. In MGD, meibum becomes thick with a consistency like butter, which form plugs within the glands. This clogging of the glands can lead to permanent gland damage and deterioration.

Studies show that Meibomian glands begin to deteriorate in the third decade of life [4], which explains why dry eye disease is commonly associated with ageing. However, dry eye disease can affect people of any age.

Environmental, general health conditions and medication use also affects disease onset and severity.

 

Meibomian gland dysfunction and blepharitis are common causes of Dry Eye Disease

 

There is a poor correlation between signs and symptoms of dry eye disease.  Many people with the condition do not present with symptoms, or their symptoms correlate poorly with clinical findings.  

For some, the condition progresses this way until the damage becomes irreversible and causes obvious discomfort, a bit like tooth decay!  It is not possible to predict an individual’s risk without a comprehensive dry eye examination.

References:
1.  Report of the International Dry Eye Workshop (DEWS). The Ocoular Surface. 5(2):61-204
2.  Schaumberg DA, Nichols JJ, Papas EB, Tong L, Uchino M, Nichols KK. The international workshop on meibomian gland dysfunction: report of the subcommittee on the epidemiology of, and associated risk factors for, MGD. Invest Ophthalmol Vis Sci. 2011 Mar; 52(4):1994-2005. Epub 2011 Mar 30.
3.  Horwath-Winter J, Berghold A, Schmut O, et al. Evaluation of theClinical Course of Dry Eye Syndrome. Arch Ophthalmo l. 2003; 121:1364 –1368.Apr;65(2):137-42.
4.  Norn M.Expressibility of meibomian secretion. Relation to age, lipid precorneal film, scales, foam, hair and pigmentation.Acta Ophthalmol (Copenh). 1987