A new liquid jet aesthesiometer prototype was developed with the aim to measure ocular surface sensitivity by employing a liquid jet.

This study aims to validate this new prototype by means of correlating its measurement with a previously validated air jet aesthesiometer, the non-contact aesthesiometer (NCCA; by Murphy et al. 1996) and by exploring the repeatability of ocular surface sensitivity measurement.

Currently, no aesthesiometer is available that delivers reliable and repeatable measurement of ocular surface sensitivity in a routine clinical setup. The only commercially available Cochet- Bonnet aesthesiometer uses a tactile-mechanical stimulus (the tip of a nylon thread), which can cause a microerosion when applied to the corneal surface. Additional disadvantages represent poor stimulus reproducibility, a limited stimulus bandwidth and the influence of humidity and age on the bending capibility of the nylon thread. For research purposes prototypes of non-contact air aesthesiometers (eg by Murphy et al. and Belmonte et al) are being used.

This study aims to correlate ocular surface sensitivity measurements of a newly developed prototype, the liquid jet aesthesiometer, with the non-contact air jet aesthesiometer by Murphy et al. 1996 and to explore its repeatability of measurement.

In this repeated measures design 60 subjects participate in corneal sensitivity measurements during two appointments with each described aesthesiometer.

Inclusion Criteria:

• Ocular surface index score < 13.0

Exclusion Criteria:

• systemic disease such as diabetes, diseases, injuries and operations in the anterior segment of the eye
• systemic medication and / or eyedrops / ointments that may have an influence of the tearfilm.
• contact lens wear less than 48 hours before commencement of study measurements.

30 healthy subjects within age range of 18-30 years 30 healthy subjects within age range of 50-65 years

individual participant data will not be made available to other researchers. The statistical analysis of the data overall will be however published, but individual participant data will not be discussed.