Meibomian gland dysfunction (also known as MGD) is a chronic disease of the meibomian glands, which is commonly characterized by obstruction of the end of the duct that delivers the secretion produced by the glands (called meibum) to the eye surface,  which prevents the glandular secretion to reach the ocular surface. The dysfunction could be that the amount of secretion produced may be abnormal (either too little or too much meibum produced). Dysfunction could also be related to the quality of the meibum produced. MGD may result in evaporative dry eye, blepharitis, chalazion, unsealed lid during sleep, and meibomian gland atrophy.MGD causes the glands to be obstructed by thick, cloudy-to-yellow, more opaque and viscous-like, oily and waxy secretions, a change from the glands normal clear secretions. Besides leading to dry eyes, the obstructions can be degraded by bacterial lipases, resulting in the formation of free fatty acids, which irritate the eyes and sometimes cause punctate keratopathy. MGD has been described as "the most underrecognized, underappreciated and undertreated disease in ophthalmic care [...] so common as to be taken as ‘normal’ in many clinical practices".The dysfunction is more often seen in women, and is regarded as the main cause of dry eye syndrome. Factors that contribute to the dysfunction can include things such as a persons age and/or hormones, or severe infestation of Demodex brevis mites. Treatment can include warm compresses to thin the secretions and eyelid scrubs with baby shampoo or eyelid cleanser, or emptying ("expression") of the gland by a professional.
Chemistry
Neostigmine, which can be viewed as a simplified analog of physostigmine, is made by reacting 3-dimethylaminophenol with N-dimethylcarbamoyl chloride, which forms the dimethylcarbamate, and its subsequent alkylation using dimethyl sulfate forming the desired compound. Spectral data
Neostigmine shows notable UV/VIS absorption at 261 nm, 267 nm, and 225 nm.Neostigmines 1H NMR Spectroscopy reveals shifts at:
7.8, 7.7, 7.4, 7.4, 3.8, and 3.1 parts per million. The higher shifts are due to the aromatic hydrogens. The lower shifts at 3.8 ppm and 3.1 ppm are due to the electronic withdrawing nature of the tertiary and quaternary nitrogen, respectively. History
Neostigmine was first synthesized by Aeschlimann and Reinert in 1931 and was patented by Aeschlimann in 1933.Neostigmine is made by first reacting 3-dimethylaminophenol with N-dimethylcarbamoyl chloride, which forms a dimethylcarbamate. Next, that product is alkylated using dimethyl sulfate, which forms neostigmine. : 103

References
External links
"Neostigmine". Drug Information Portal. U.S. National Library of Medicine. "Neostigmine methylsulfate". Drug Information Portal. U.S. National Library of Medicine. "Neostigmine bromide". Drug Information Portal. U.S. National Library of Medicine.