P 174 Ultrastructure of organ-cultured human cornea after deswelling in exosol medium

makes it impossible to express the results in a general and informative manner. We felt, therefore, that it was useful to define two index that can be used for the purposes of such analysis. Metho& The axial and toric components of ametropia are such that it can be seen as a point within a threedimensional reference. The distance between the point and the centre of a reference defines the Refractive Error Index. After treatment, residual ametropia has a similar refractive error index. The distance between the points symbolising the two refractions is then defined as the Refractive Variation Index. Resulrs: The lower the refractive error index, the closer the patient’s refraction is to emmetropia. This index is much more powerful than the spherical equivalent since there is no compensation between axis and cylinder when calculating this index. Conclusions: These index seem to be particularly wellsuited to the expression of results obtained during the treatment of axial and cylindrical ametropia. INFLUENCE OF PREPARAIION AND STORAGE ON HUMAN CORNEAL TWICKNESS NILIUS R. AEDBRAKE C. SALLA S. and M. REM