Title : the Variability of Corneal and Anterior Segment Parameters

30 Purpose: To analyse, describe and test diverse corneal and anterior segment parameters 31 in normal and keratoconic eyes to better understand the geometry of the keratoconic 32 cornea. 33 34 Method: 44 eyes from 44 keratoconic patients and 44 eyes from 44 healthy patients 35 were included in the study. The Pentacam System was used for the analysis of the 36 anterior segment parameters. New ad-hoc parameters were defined by measuring the 37 distances on the Scheimpflug image at the horizontal diameter, with chamber depth now 38 comprising of two distinctive distances: corneal sagittal depth and the distance from the 39 endpoint of this segment to the anterior surface of the lens (DL). 40 41 Results: Statistically significant differences (p<0.05) between normal and keratoconic 42 eyes were found in all of the analysed corneal parameters. Anterior chamber depth 43 presented statistical differences between normal and keratoconic eyes (3.06 ± 0.43 mm 44 versus 3.34 ± 0.45 mm, respectively; p = 0.004). This difference was found to originate 45 in an increase of the DL distance (0.40 ± 0.33 mm in normal eyes against 0.61 ± 0.45 46 mm in keratoconic eyes; p = 0.014), rather than in the changes in corneal sagittal depth. 47 48 Conclusion: These findings indicate that keratoconus results in central and peripheral 49 corneal manifestations, as well as changes in the shape of the scleral limbus. The DL 50 parameter was useful in describing the forward elongation and advance of the scleral 51 tissue in keratoconic eyes. This finding may help in the monitoring of disease 52 progression and contact lens design and fitting. 53