| (1) Genetic Causes:
|
| (a) Riley–Day syndrome (hereditary sensory neuropathy type III, familial dysautonomia) |
| (b) Möbius syndrome |
| (c) Familial corneal hypoesthesia (familial trigeminal anesthesia) |
| (2) Systemic Diseases:
|
| (a) Diabetes mellitus |
| (b) Leprosy |
| (c) Vitamin A deficiency |
| (d) Amyloidosis |
| (e) Multiple sclerosis |
| (3) Central Nervous System Diseases:
|
| (a) Intracerebral tumors |
| (b) Postoperative, particularly after brainstem surgery |
| (c) Aneurysm |
| (d) Cerebrovascular diseases of the brainstem |
| (e) Stroke (brainstem) |
| (f) Degenerative CNS diseases (Alzheimer’s disease, Parkinson’s disease) |
| (g) Acoustic neuroma |
| (h) Trigeminal neuralgia |
| (i) Other surgical injuries to the trigeminal nerve |
| (4) Ocular Causes:
|
| (a) Corneal infections: |
| (i) Herpes infections (Herpes simplex and Herpes zoster) |
| (ii) Other infections, e.g., Acanthamoeba |
| (b) Chemical burns |
| (c) Side effects of topical medications and their conversants: |
| (i) Benzalkonium chloride (BAK), Timolol, Betaxolol, Sulfacetamid 30%, Trifluridine, Diclofenac |
| (ii) Abuse of local anesthetics |
| (d) Diseases comprising ocular surface disorders: |
| (i) Ocular surface Chronic severe blepharitis and/or rosacea |
| (ii) Entropion |
| (iii) Ocular injuries or chemical burns Graft-versus-host disease |
| (iv) Sjögren’s syndrome |
| (v) Ocular cicatricial pemphigoid |
| (vi) Trachoma |
| (e) Eye surgeries: |
| (i) Cataract surgery |
| i. Photorefractive keratectomy (PRK) and Laser in situ keratomileusis (LASIK) |
| ii. Penetrating keratoplasty and deep anterior lamellar keratoplasty (DALK) |
| iii. Collagen cross-linking for the treatment of keratoconus |
| iv. Following excessive laser coagulation of the retina or ciliary body as Pan-retinal photocoagulation or during vitrectomy |
| v. Multiple ocular surgeries |
| (f) Other ocular causes: |
| i. Contact lens use |
| ii. Orbital tumors |
| iii. Corneal dystrophies |
| iv. Radiotherapy sequelae |
