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An evaluation of corneal nerve morphology and function in moderate keratoconus
Luisa Simo Mannion1, Cindy Tromans, Clare O'Donnell
1Optometry and Neuroscience, Moffat Building, The University of Manchester, PO Box 88, Manchester, M60 1QD, UK. Maria.L.Simo-mannion@manchester.ac.uk
Purpose:
To investigate corneal nerve morphology and corneal sensitivity in keratoconus.
Methods:
The central cornea of 13 subjects with keratoconus and 13 age-matched control subjects was assessed using in vivo confocal microscopy and corneal aesthesiometry.
Results:
Significant differences in corneal nerve fibre density were found between the subjects with keratoconus and the control subjects (keratoconus versus control; 1018.3+/-489.6 microm versus 1820.7+/-789.5 microm; p = 0.006). The mean diameter of nerve fibres in the stroma was found to be greater in subjects with keratoconus compared to control subjects (keratoconus versus control; 10.2+/-4.6 microm versus 5.5+/-1.9 microm; p = 0.007). The orientation of corneal nerve fibres in the subjects with keratoconus appeared to be altered from the predominantly vertical orientation seen in the control subjects. Corneal touch threshold was found to be similar in the two groups, although the subjects with keratoconus using contact lens correction had reduced corneal sensitivity compared to the contact lens-wearing control subjects (keratoconus with contact lenses versus controls with contact lenses; 1.18+/-0.19 g/mm2 versus 0.98+/-0.05 g/mm2; p = 0.03).
Conclusion:
This study reveals significant reductions in nerve density in the keratoconic cornea. The thickened stromal nerve fibres observed in the keratoconic corneas may explain why prominent corneal nerves are often seen using slit lamp biomicroscopy in keratoconic patients.
