■Dry eye is a multifactorial disease of the ocular surface characterized by a loss of homeostasis of the tear film, and accompanied by ocular symptoms, in which tear film instability and hyperosmolarity, ocular surface inflammation and damage, and neurosensory abnormalities play etiological roles.
■Meibomian gland dysfunction (MGD) is thought to be the leading cause of dry eye disease.
■Meibomian glands or glandulae tarsales are large sebaceous glands present in eyelids which secrete lipids (Meibum) that form the superficial layer of tear film to protect evaporation of the aqueous phase.There are about 25-40 glands in the upper eyelid and about 20-30 in the lower eyelid. Each gland opens into the lid margin secreting lipids to form tear film. Meibum contains over 100 major individual complex mixture of lipids, over 90 proteins, electrolytes that contribute to the stability of tear film in health and disease.
■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. This may result in alteration of the tear film, symptoms of eye irritation, clinically apparent inflammation, and ocular surface disease.
■The importance of MGD has gone beyond its key role in dry eye disease causation to its role in ophthalmic surgery outcome, owing to the fact that “ocular surface is key to surgical outcomes”. The correct diagnosis and treatment of any possible cause of dry eye e.g. MGD, is mandatory for any type of surgical procedure.
Unrecognized MGD can compromise refractive surgery results as the final visual result of refractive surgery is largely dependent on the status of the tear film.
Tear film irregularities change corneal reflectivity and can lead to inaccurate preoperative K readings and mistaken IOL power, causing dissatisfaction with the refractive results.
Untreated MGD can put cataract patients at higher risk for infection and inflammation.
MGD is the most underrecognized, underappreciated and undertreated disease in ophthalmic care. It is so common as to be taken as ‘normal’ in many clinical practices despite its key role in overall eye and vision health.
■Risk factors
■Classification
■Diagnosis
■Treatment