Ocular discomfort by environmental and personal risk factors altering the precorneal tear film.

Ocular discomfort (e.g. burning, dry and itching eyes) is among top 2 symptoms in office environments. The ophthalmological explanation is aqueous-deficient dry eye and evaporative dry eye and exposure to allergens, while indoor air pollutants causing chemesthesis generally is the rationale of the indoor environmental community. Review of salient environmental, occupational, and personal risk factors, that alter the precorneal tear film (PTF), reveals at least three mechanisms resulting in ocular discomfort. First, the PTF structure is altered by a physical process that increases the emission rate of aqua loss resulting in hyperosmolarity, gland dysfunctions, and associated discomfort. Second, the structural composition of the outermost lipid layer of the PTF is altered by aggressive aerosols and combustion products, both indoors and outdoors, that facilitate loss of aqua, and possibly chemesthesis. Third, strong sensory irritating pollutants cause chemesthesis by trigeminal stimulation. In general, organic and inorganic indoor air pollutant concentrations are too low causing chemesthesis, but the odor may cause reported discomfort. The total risk of ocular discomfort is exacerbated by physical alteration of the PTF by visual tasking and climate conditions (low humidity, high temperature, and draft); further, personal factors like age, gender and use of certain medication also influence the overall stability of the PTF.