Background: The measurement of corneal sensitivity threshold is important for several ocular surface diseases. The current study assesses the precision, agreement and utility of corneal sensitivity threshold measurement using a new, purpose-built non-contact corneal aesthesiometer.
Methods: A new instrument and an established non-contact corneal aesthesiometer device was used to measure the corneal sensitivity threshold on the right eye of 40 healthy human participants. Exclusion criteria included: corneal pathology, previous ocular surgery, ocular trauma, contact lens wear, diabetes or peripheral neuropathy. A forced-response, double-staircase method was used to obtain corneal sensitivity threshold from the mean of three readings per participant, for each non-contact corneal aesthesiometer. Screen demarcations relative to the corneal limbus facilitated alignment with the new device. Repeatability of the new instrument was tested three consecutive times on the same day. Intra-observer and inter-observer reproducibility and agreement were determined using one-way analysis of variance or analysis of variance and Bland-Altman analysis, respectively.
Results: Forty eyes of 40 participants were assessed (15:25 M:F, 30.5 ± 11.4 years). The new instrument demonstrated good repeatability (p = 0.47). There was no difference in the mean corneal sensitivity threshold between the new (0.60 ± 0.36 mbar) and established (0.60 ± 0.34 mbar) aesthesiometers (p = 0.92). Utilising the new instrument, inter-observer reproducibility (on a different subset of 10 participants) yielded thresholds of 0.41 ± 0.16 mbar and 0.42 ± 0.13 mbar (p = 0.88) for the two observers. Bland-Altman analysis confirmed good intra and inter-observer agreement. Screen demarcations relative to the limbus, enabled easier corneal alignment.
Conclusion: The new non-contact corneal aesthesiometer confirmed very good repeatability and reproducibility, as well as good agreement with the long-established instrument. Overall, this contemporary approach enables accurate and precise assessment of corneal sensitivity and thus, corneal nerve function, in normal and diseased cornea.
Keywords: corneal nerve function; corneal sensitivity threshold; instrument precision; non-contact corneal aesthesiometer.
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