[IOL power determination using regression formula of lens location].

Postoperative lens location was expressed as a linear regression formula of axial length and corneal curvature. Using the formula, the IOL power of a convexplano, biconvex, and planoconvex lens was calculated by Ray Tracing Error Correction (RTEC). The calculated power of a convexplano lens coincides with Sanders, Retzlaff, Kraff (SRK) II in axial length less than 28 mm and corneal curvature between 7 to 9 mm. Varying regression coefficients changes lens power continuously and simulates the theoretical formulas SRK II and SRK. RTEC predicted that formula SRK II is valid only for a convexplano lens and needs correction in a biconvex or planconvex lens and in corneal curvature less than 7.0 mm. IOL power determination requires a learning process based on the postoperative refraction. The difference of learning between SRK and RTEC is also discussed.