[Critical corneal radii may skew correct IOL calculation by using the SRK/T formula]

The popular SRK/T formula for IOL calculation is analysed with respect to the underlying optical model and identified as a "thin-lens formula". As far as the prediction algorithm for the "optical anterior chamber depth" is concerned, it is shown that mathematically there exists a critical value for the radius of corneal curvature which marks the onset of a nonphysiologic formula behaviour. Within the algorithmic framework of the SRK/T formula, this critical curvature is solely dependent on the axial length. Clinically, the effect of this insufficiency of the formula is not of great importance: a check through our biometry database showed that 4 out of every 1000 IOL calculations were affected.