NK is diagnosed on the basis of the patient's medical history and a careful examination of the eye and surrounding area. With regard to the patient's medical history, special attention should be paid to any herpes virus infections and possible surgeries on the cornea, trauma, abuse of anaesthetics or chronic topical treatments, chemical burns or, use of contact lenses. It is also necessary to investigate the possible presence of diabetes or other systemic diseases such as multiple sclerosis. The clinical examination is usually performed through a series of assessments and tools: * General examination of cranial nerves, to determine the presence of nerve damage. * Eye examinations: # Complete eye examination: examination of the eyelids, blink rate, presence of inflammatory reactions and secretions, corneal epithelial alterations. # Corneal sensitivity test: performed by placing a cotton wad or cotton thread in contact with the corneal surface: this only allows to determine whether corneal sensitivity is normal, reduced or absent; or using an esthesiometer that allows to assess corneal sensitivity. # Tear film function test, such as Schirmer's test, and tear film break-up time. # Fluorescein eye stain test, which shows any damage to the corneal and conjunctival epithelium Classification According to Mackie's classification,<unk>  can be divided into three stages based on severity: # Stage I: characterized by alterations of the corneal epithelium, which is dry and opaque, with superficial punctate keratopathy and corneal oedema. Long-lasting<unk>  may also cause hyperplasia of the epithelium, stromal scarring and neovascularization of the cornea. # Stage II: characterized by development of epithelial defects, often in the area near the centre of the cornea. # Stage III: characterized by ulcers of the cornea accompanied by stromal oedema and/or melting that may result in corneal perforation.
Neurotrophic keratitis
Nummular keratitis
Fungal keratitis
Peripheral ulcerative keratitis
Interstitial keratitis
Fuchs heterochromic iridocyclitis
Lattice corneal dystrophy
Subepithelial mucinous corneal dystrophy