Psychophysical studies of ocular surface sensory processing

This series of experiments demonstrated that the quality of the sensation evoked from the human ocular surface (cornea and conjunctiva) by mechanical, thermal (cold) and chemical (CO2) stimulation could be differentiated at threshold and suprathreshold levels. A proposed hypothesis is that the ocular surface processes the sensory information by means of different psychophysical channels. These channels, however, are not independent, as mechanical and chemical, non-noxious cold and chemical, and noxious heat and chemical channels interact with each other. This interaction is not only within the cornea at absolute threshold level, but it is proposed that it is also between corneal and conjunctival channels at suprathreshold levels. These channels exhibit adaptive characteristics. This was demonstrated clinically by the observation that acute soft toric contact lens wear causes an increase in corneal and conjunctival sensitivity.