[Corneal thickness progression from the thinnest point to the limbus: study based on a normal and a keratoconus population to create reference values].

PURPOSE: To study the variation and progression of the pachymetric values from the thinnest point towards the limbus in normal and keratoconic corneas; to establish reference curves for this parameter.

METHODS

One hundred eyes with normal corneas and twenty-five eyes with mild keratoconus (stages I and II - Krumeich) were analyzed using the Orbscan. Concentric circles were drawn on the thinnest point of the cornea with increasing radii from 1 to 7 mm. The average results of each circle were calculated and inserted in an Excel table in order to arrange a progression chart for each case starting on the thinnest point. The SPSS software was also used for statistical analysis. Student's t test was then used to compare the found values.

RESULTS

The average values on the thinnest point in normal patients was 511.6 microm (standard deviation 30.6). The average values of the thinnest point in patients with keratoconus was 424.4 microm (standard deviation 56.57). Statistically significant different values were reported (p<0.01) for all circles, and for 6 and 7 mm radii p=0.01.

CONCLUSION

There is a greater pachymetric variability in patients with keratoconus. Keratoconic corneas also have a faster progression of pachymetric values than healthy eyes. Pachymetric progression complements traditional single point evaluation of corneal thickness and must be considered for the screening at refractive candidates. This parameter may represent an indirect index of the biomechanics of corneal tissue but this hypothesis still needs further studies.