Blepharitis and Eyelid Margin Disease
Blepharitis and Eyelid Margin DiseaseBlepharitis is an Inflammation of the Eyelid Margins
Blepharitis is an inflammation of the eyelid margin that may have several causes and can result in mild to severe discomfort and irritation as well as possibly blurred vision. It is a chronic condition that can be controlled with a daily routine that varies based on severity of the disease. The treatment must be continued consistently long term or there is a risk of it recurring.
There are two types of blepharitis commonly known as anterior and posterior (Meibomian Gland Disease, MGD) blepharitis. The two types affect different parts of the eyelid and have different treatments but they commonly occur together and cause the same symptoms.
Blepharitis Signs and Symptoms
The symptoms include burning, itching, redness, dry eyes, sensitivity to light, variable vision and a gritty sensation which may be worse in the morning. It's important to take note of when these symptoms are better or worse and how long they last. 
Anterior blepharitis affects the eyelids around the eyelashes and consists of inflammation, scaling, flakes, debris, lid ulceration and lid crusting. It is also possible to experience loss or misdirection of eyelashes as well as a hordeolum (stye) along the eyelid margin. Only about 10% of cases have anterior blepharitis alone. It is much more common to have both types of blepharitis together.
Posterior blepharitis or Meibomian Gland Disease (MGD) will present with the same 
symptoms but the inflammation will also involve the Meibomian glands which are tiny glands located in the eyelids that secrete oil into the tears of the eyes to form the outermost layer of the tears. This oily outer layer of tears is very important because it slows down the evaporation of the other tear layers. The eyelid margin will often become thickened and the clear, thin oil normally secreted by the meibomian glands may become turbid and yellow often blocking the gland and contributing to dry eyes. The oily fluid is secreted through tiny holes on the eyelid margin that can become blocked during MGD. When the glands become blocked dry eyes also develop.
Causes of Blepharitis
Anterior blepharitis is usually caused by an over colonization of bacteria (usually staphylococcus aureus) at the eyelid margin. It's necessary to have some bacteria in the area but the problems start when there is too much. Another cause could be demodex, which is a mite that can live in the eyelash follicles or the meibomian glands. The bacteria and demodex leave excrement and toxins behind that start the inflammatory reaction. The eyelids eventually become red, swollen and much less efficient at keeping the tear film even and thick. The eyes then become dry, which causes vision to fluctuate and possible injury to the cornea due to friction of the eyelids during a blink. 
Posterior blepharitis can occur without a specific cause or it could be secondary to something else such as acne rosacea, seborrheic dermatitis, atopic disease (asthma, seasonal allergies and dermatitis), cicatrizing disorders and demodex. Eventually, if posterior lid disease isn't treated, the meibomian glands can begin to atrophy and become non-functional. Once the glands clog or atrophy, the eyes will become increasingly inflamed and dry causing discomfort and blurred vision as well as creating an opportunity for infection.
