What is ocular surface disease?

The definition of ocular surface and ocular surface diseases is a new concept put forward in recent years. Trauma, inflammation and other injury factors can lead to a series of pathological changes such as corneal and conjunctival epithelial phenotype changes, corneal neovascularization, xerophthalmia and so on, and then cause visual dysfunction of patients. Therefore, normal ocular surface structure and function are the premise of obtaining clear vision. Anatomical definition of ocular surface: all mucosal epithelium between the beginning of ocular surface and the gray line of upper and lower eyelid margins, including corneal epithelium and conjunctival epithelium (bulbar conjunctiva, palpebral conjunctiva and fornix conjunctiva). Clinical ocular surface includes conjunctiva, cornea, eyelid, lacrimal apparatus and lacrimal passage, which generally refers to all extraocular appendages involved in maintaining the ocular surface health protection system. Eye surface disease (Nelson, 1980): refers to diseases that damage the normal structure and function of cornea and conjunctiva. Eye tear diseases: including all superficial keratopathy, conjunctival diseases and external eye diseases, as well as lacrimal gland and lacrimal duct diseases affecting tear film. Second, the classification of ocular surface diseases 1) Squamous metaplasia: pathological non-keratinized epithelium becomes keratinized metaplasia. There is a clear cause of disease. Such as chemical or thermal injury, Stevens-Johnson syndrome and pemphigoid. The decrease of tear film stability or local keratoconjunctival inflammation is the main cause of corneal metaplasia, which can also lead to the disappearance of conjunctival goblet cells, thus aggravating tear film instability. 2) Limbal stem cell deficiency: characterized by the invasion and replacement of normal corneal epithelium by conjunctival epithelium. ① Lack of corneal limbal stem cells caused by injury: such as Stevens-Johnson syndrome or toxic epidermal necrosis and dissolution, repeated surgery or condensation of corneal limbus, toxicity of antimetabolic drugs, corneal diseases caused by contact lenses, severe microbial infection, etc.