PURPOSE: To calculate the more accurate degree of an intraocular lens by performing small incision self-closing valve lens ultrasonic emulsifying and sucking cataract operation and removing the nucleus and cortex of a lens to cause physiological intraocular pressure and, thereafter, determining the degree of the intraocular lens to be inserted using a measured refraction value.

CONSTITUTION: The radius R of curvature of the cornea before operation is measured to be inputted to an intraocular lense degree operation circuit. A small width self- closing incised cut 1 is formed before operation to start lens ultrasonic emulsifying and sucking cataract operation and, after a lens 2 and the cortex 3 of the lens are removed, physiological intraocular pressure is caused by using the self-closing incised cut l and an artificial aq. humor to measure a refraction value. The refraction value is automatically inputted to the intraocular lens degree operation circuit and the axial length L of an eye is calculated from the previously inputted radius R of curvature of the cornea and the refraction value. Estimate anterior sac depth C is calculated from the A-constant possessed by an intraocular lens 4, the radius R of curvature of the cornea and the axial length L of the eye and the degree of the intraocular lens and the estimate refraction value after operation are calculated and displayed.