Blepharitis: The Most Common Eye Lid Disease
By Dana N. Koff, MSc, BSc Optometry. Former lecturer of Optometry at the Jordan University of Science & technology, Ingrid
Definition of Blepharitis:
Blepharitis is a chronic, intermittent and bilateral inflammation of the eyelids 1 it is the most common disease of the eye lids 2-9 . About 20% of the adult population over the age of 45 suffers from blepharitis and meibomian gland dysfunction. 10 The disease includes cutaneous and infectious manifestations affecting the eyelids and the eye lashes, with the involvement of the eye lid margins and the meibomian glands 11 leading to ocular damage. 12
A couple of studies conducted on blepharitic patients have shown that the tear physiology and the meibomian gland function are both affected in those patients10, 13 when compared to the normal ones. 14 The difference seen in blepharitic patients was explained by the presence of an abnormal lipid layer composition of the tear film in the ocular surface, which in turn increases tear film osmolarity and leads to an evaporative type of dry eye disease. 10, 11, 13,15 Thus, it's hard to differentiate between blepharitis, meibomian gland dysfunction and dry eye disease only from their ocular manifestations since they all over-lap in their pathophysiology. 10 In another one, researchers found that the inflammation and irritation which accompany chronic blepharitis, result from bacterial lypolysis and the abnormal secretion of the meibomian glands.17 In fact, this specific study has proved that the more the meibomian gland abnormalities are present, the more the bacterial lipolysis is found there. 17
Classification of Blepharitis:
Blepharitis is a complex disease that can be divided according to its location into: An anterior type; by affecting the anterior lid margins of the eyes or the eye lashes, or a posterior type which affects the meibomian glands; both types can lead to infection and inflammation of the eyelids if not treated properly. 1 Another classification of blepharitis is according to the cause of the disease and is divided into: A seborrheic type, in which the meibomian gland free fatty acids show changes in their composition when compared to the other type which is the staphylococcal one, which results from a staphylococcal infection as the name indicates 18 , a mixed staphylococcl-seborrheic disease, and finally a meibomian gland dysfunction type of the disease. 1
Lid margin diseases are seen with blepharitis, conjunctivitis, and external inflammation. 12 Blepharitis can be either seborrheic or staphylococcal in nature in the anterior type of the disease. 1 Staphylococcal bacterial infection is a major cause of infection of the eyelids and the meibomian glands 19 , which can lead to the formation of a hordeolum in this type of the disease. 12 Younger age females group is the most common group to suffer from this kind of infection, which doesn't usually last for a long period of time and is easily treated. 20 Staphylococcal blepharitis can sometimes result from the presence and formation of Staphylococcal toxins caused by dermal irritation. 21 Though in the cutaneous type of the disease, allergy and hypersensitivity reactions will be the most apparent and obvious symptoms suffered from by those patients rather than the infectious ones. 12 The atopic type of the disease leads to inflammation of the lid margins, conjunctivitis, and dermatitis of the skin of the eyelids. 12
Cutaneous type of blepharitis can be either bacterial or viral in origin. 12 The viral type of the disease leads to ulceration. 12 Whereas, the bacterial disease can be either purulent or ulcerative, leading to an angular blepharitis in the lateral canthus. 12 Other non-common causes of cutaneous blepharitis, leading to chronic inflammation in the eyelids are parasites. 12 The prevalence of cutaneous blepharitis due to parasites increases with age. 12 This type of the disease is less common than the other types. 5 The cutaneous type of blepharitis is also less common than the other types of blepahritis. 12 From the skin infections that are associated with blepharitis, are: Seborrheic dermatitis 18, 19, acne rosacea 3, 11, 18, 20, 22,23, atopic dermatitis 1, 5, or eczema 1 .
The anterior portion of the eyelid with Zeis gland or the posterior eyelid with the meibomian glands 24 are usually affected by blepharitis. 20 Involvement of the meibomian gland is either; seborrheic, obstructive in nature or the combination of both. 1
The disease starts at childhood and continues through life. 2 Climate plays a major role in the disposition of staphylococcal blepharitis, that's why in hot countries such as Egypt and India, the prevalence of the disease is high, reaching more that 50% of the whole population. 2
It has been also found that the body of the demodexfolliculorum contains bacteria, which suggests that these mites can be vectors that carrystaphylococci and have a major role in the disposition of the staphylococcal type of blepharitis in addition to other infectious causes of the disease. 2 Staphylococcal blepharitis is subdivided into: A squamous type and an ulcerative type. 2 The most common type of the two is the squamous one, which is characterised by brittle, hard and fibrinous scales, Where as the ulcerative type is usually present with hard, matted crusts around each individual cilia; when crusts are removed bleeding ulcers can be clearly seen in the hair follicles. 2 Both types are associated with conjunctival and corneal complications. 2
Posterior blepharitis (Meibomian gland dysfunction):
It is the most common disease of the meibomian glands; present with inflammation of the lid margins and is associated with abnormal orifices of the meibomian glands and abnormal tear secretion, the disease accounts for 39-50% of the meibomian gland diseases. 1 The disease can be; primary or secondary, either focal or diffused. Secondary meibomian gland dysfunction results from problems in the sebaceous glands. 1 Excessive secretion of the meibomian gland can be obviously seen in seborrheic dermatitis, rosacea and atopy. 1 Dryness of the eyes maybe also associated with the disease in this case. The obstructive type of the disease is associated with skin infection and by obstruction of the meibomian glands, with foreign body reaction, dilatation of blood vessels, changes in the keratinization status of the meibomian glands, and squamous cells metaplasia. 1 One study conducted by Sullivan and his colleagues has linked meibomian gland dysfunction to androgen hormone deficiency. 25 Meibomian gland dysfunction can be asymptomatic or it can lead to consistent inflammation and irritation of the eyelids. 1 The disease is more common among the aging population, reaching up to 68% in patients over the age of 60 .10
Pathophysiology of the disease:
Abnormal tear film, abnormal meibomian tear secretion and microbial infection can all induce blepharitis.1 Blepharitis can result from the reduction of the secretion reaching the lid margins or it might be due to variation in the content of the tear secretion itself. 1
Other reasons for the formation of blepharitis may be due to plugging or keratinisation of the orifices of the meibomian glands leading to inflammation of the lid margin. 1 In the seborrheic type of the disease hyper-secretion of lipids lead to obstruction of the meibomian glands orifices, also scarring in the lid margin leads to changes of the orifices, which as a result affect their function, ending up with lesser secretion to the different parts of the lid margin. 1
Chronic blepharitis disease leads to changes in the composition of the meibomian gland secretion. 1 With these changes, the lipid layer doesn't spread evenly on the surface anymore, which leads to more evaporation of the tear film ending up with dry eye disease. 1 The interaction of poor distribution of the lipid secretion, plugging of the meibomian gland orifices and bacterial infection, all lead to thinning of the tear film; in which with more aqueous tear evaporation, raises the osmolarity of the tear film and the level of inflammatory cytokines, ending up with a damaged ocular surface and tear dysfunction. 1 In a study conducted by Shine and his colleagues, it was clearly noticed that the changes seen on the meibomian glands lipid were mainly due to the peroxisomal and endoplasimic reticulum defects of its cells, leading to the chronic blepharitis signs seen in this case. 26 Interestingly, not only bacteria, scientists discovered that demodex fungi which affects the skin, can also be a major causative of blepharitis. 1
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