Cytological changes and conjunctival hyperemia in relation to sensory eye irritation

In general, irritation is a physiological response to a chemical or physical stimulus involving objective changes (e.g., local redness and edema) and subjective sensations (e.g., pruritus and pain). The perception of an irritating stimulus in the eyes and the upper airways is called sensory irritation. Sensory irritation is a prevalent symptom in relation to complaints about indoor air quality. The intensity of perceived sensory irritation in humans has mainly been evaluated using psychophysical methods. However, perceived sensory irritation is dependent on the subject expressing the symptoms; that is, it is a subjective measure. This is a problem in assessment of irritation effects from air pollution or other factors, since the expression of the irritation symptoms may be biased by, for example, interaction with other people and odors. The subjectivity of the measures is an important complication in several studies dealing with problems regarding indoor air quality. The bias problems make it important to complement the psychophysical measurements of sensory irritation with objective assessments of irritation. In addition, only little is known about the association between sensory irritation and possible physiological/ pathological changes in the mucosal membranes in relation to studies of indoor air. Two studies (study 1 and study 2) were conducted to investigate changes in conjunctival hyperemia and conjunctival fluid cytology for subjects exposed to volatile organic compounds (VOCs) in their eyes only. Eight subjects participated in study 1. Each subject was exposed to three different mixtures of VOCs. A total of 16 subjects participated in study 2. Half of the subjects were exposed to 1-octene and the other half, to n-butanol. In both studies, photographs of bulbar conjunctiva were taken and conjunctival fluid was sampled before and after exposure. Moreover, the perceived irritation intensities were registered continuously during exposure. Overall, perceived irritation intensity and conjunctival hyperemia increased with increasing exposure concentrations, whereas cytological changes in the conjunctival fluid samples did not seen to be related to exposure concentration, perceived irritation, or changes in conjunctival hyperemia.