Dry eye vs air pollution

  

The study reviews eye irritation using a multidisciplinary approach. Potential risk factors and objective gender differences are identified, and possible hypotheses for eye irritation caused by indoor air pollution are discussed. Eye irritation depends somewhat on destabilization of the outer-eye tear film. An integrated physiological risk model with blink frequency, destabilization, and break-up of the eye tear film as inseparable phenomena may explain eye irritation among office workers in terms of occupational, climate, and eye-related physiological risk factors. Certain volatile organic compounds that are both chemically reactive and airway irritants may cause eye irritation. If airborne particles alone should destabilize the tear film and cause eye irritation, their content of surface-active compounds must be high. Personal factors (eg, use of contact lenses, eye make-up, and certain medication) may also affect destabilization of the tear film and possibly result in more eye symptoms. Ocular discomfort (e.g. burning, dry and itching eyes) is among top 2 symptoms in office environments. The optometrists 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. Tear film breakup time (BUT) was measured in 40 normal subjects and 30 tandoor workers on 8 different occasions over a period of one month. Reproducibility of the BUT test and factors involved in interpretation of tear film breakup were studied. It was found that of 50 eyes, the average BUT ranged from five to 100 seconds, and that there were noticeable variations (P ≤.05) in an individual eye from one patient visit to the next. The BUT is not a closely reproducible phenomenon in an individual eye.