City Research Online

Abstract

Corneal touch threshold (CTT) was investigated by aesthesiometry in patients with keratoconusq with and without contact lens wear. Using a matching control group it was established that CTT was significantly higher for the central corneal position in keratoconus. No difference inCTT was found in four peripheral corneal positions in keratoconic and normal corneas. Central CTT correlated inversely with central corneal curvature and central corneal thickness. Central corneal curvature was the most significant single factor to correlate with central CTT and indicates that CTT increases (sensitivity reduces) as the cornea steepens. Corneal surface irregularityq as measured by mire image distortion, correlated positively with central CTT as did corneal scarring. Central CTT did not show a relationship with duration of the disease nor the visibility of the corneal nerve fibres. Lid margin touch thresholds (LTT) were investigated for the central position on the lower and upper eyelid margins. No statistical differences were found between keratoconic and normal eyes nor between upper and lower eyelid margins. The magnitude of LTT was in the order of that established for the peripheral corneal CTT. Innervation of the human corneal stroma and epithelium was investigated by light and electron microscopy in the central and mid-peripheral positions. All nerve bundles were located in the anterior two thirds of the. corneas. In keratoconic corneas mid-peripheral stromal nerve bundles were disorganised and irregular taking up the shape of the adjacent collagen lamellae. Nerve bundles had a regular oval appearance in the control corneas. In both groups Schwann cell cytoplasm was sparse and of varying degree of electron density; axon varicosities were not uncommon and axon content with respect to organelles were similar. The axon density showed large variation in keratoconic: specimens and averaged more than threefold that of control specimens for stromal and epithelial nerves. The control corneas showed a greater proportion of large diameter stromal axons than in keratoconic corneas. This result was reversed for epithelial axons. The results are discussed with respect to the disease process and influence on tactile sensitivity.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > Q Science (General)
Departments:	School of Health & Psychological Sciences > Optometry & Visual Sciences Doctoral Theses School of Health & Psychological Sciences > School of Health & Psychological Sciences Doctoral Theses

Export

Downloads