Clinical Study
Eye (2009) 23, 586–592; doi:10.1038/eye.2008.52; published online 14 March 2008
Laser scanning in vivo confocal microscopy and quantitative aesthesiometry reveal decreased corneal innervation and sensation in keratoconus
D V Patel1, J Y F Ku1, R Johnson1 and C N J McGhee1
1Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
Correspondence: CNJ McGhee, Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland 1, New Zealand. Tel: +64 9 373 7599 ext. 86712; Fax: +64 9 367 7173; E-mail: c.mcghee@auckland.ac.nz
Received 1 October 2007; Revised 4 February 2008; Accepted 4 February 2008; Published online 14 March 2008.
Abstract
Purpose
The purpose of this study was to quantitatively analyse laser scanning in vivo confocal microscopy images of the corneal epithelium and sub-basal nerve plexus in patients with keratoconus and to correlate these microstructural observations with corneal sensitivity.
Methods
A total of 31 eyes of 31 normal human subjects, and 27 eyes of 27 subjects with an established diagnosis of keratoconus were recruited. Twelve subjects with keratoconus had never worn contact lenses (K-NCL). Fifteen subjects with keratoconus wore contact lenses routinely (K-CL). All eyes were examined using slit-lamp biomicroscopy, Orbscan topography, non-contact corneal aesthesiometry, and laser scanning in vivo confocal microscopy.
Results
Central corneal sensation was significantly lower in K-CL compared to normal (P=0.028). However, there was no significant difference in corneal sensation between the normal and K-NCL groups (P=0.059). Both sub-basal nerve density (P<0.001) and basal epithelial density (P<0.001) were significantly lower than normal in all keratoconic subjects. Central corneal sensation was only significantly correlated with sub-basal nerve density (P=0.001) and was not significantly correlated with any of the basal epithelial parameters. Sub-basal nerve density showed significant positive correlation with basal epithelial density (P<0.001).
Conclusion
This quantitative study reveals decreased corneal innervation, sensation, and basal epithelial density in keratoconus. The results of this study provide strong evidence that both the sub-basal nerves and the basal epithelium may be involved in the pathogenesis of keratoconus, although it is uncertain whether these are primary or secondary changes.
Keywords:
cornea, keratoconus, in vivo confocal microscopy, epithelium, nerves, sensation
