Meibomian gland dysfunction - MGD
Keratitis Sicca syndrome is the most commonly treated ophthalmic condition in the world. The associated visual disturbances such as blurred vision, fluctuating vision or glare sensitivity are becoming more and more prominent in the daily routine of ophthalmologists. Meibomian gland dysfunction MGD becomes a chronic condition that has manifested itself in 80% of dry eye cases.
MGD is manifested by inflammation of the meibomian glands, which are typically obstructed, displaced or atrophied. Meibum is inadequately produced, the tear film destabilizes, and the evaporation rate of the aqueous layer increases. Pathogens, hyperosmolarity, nutrient deficiency, and dehydration put stress on the cornea, which in turn leads to even more inflammation. This vicious cycle is the root cause of the chronic inflammation that underlies dry eye disease.
One of the main risk factors for MGD is skin rosacea with several mechanisms of action appearing to be causative for this association. For example, in rosacea abnormal blood vessels (telangiectasias) release pro-inflammatory mediators that can easily spread to the eyelids. There are also demodex mites that settle on the skin affected by rosacea. These parasites play an important role in causing eyelid inflammation.
In addition, demodex mites are infested with bacteria, especially bacillus olerinus. The proliferation of this bacterium not only contributes directly to inflammation, but also increases the melting temperature of the meibum, causing thickened meibum to block the meibomian glands. Thickened secretions and blocked glands therefore lead to an insufficient lipid content in the tear film, resulting in instability and, in turn, a further increase in ocular surface inflammation