A control apparatus for an ophthalmic surgical system for phacoemulsification of an eye lens has an optical system for generating an object region wherein at least part of the eye lens and part of a needle of a phacoemulsification handpiece are arranged. The handpiece is provided with an aspiration line； an image evaluation unit is suitable for evaluating the generated image in such a way that an evaluation variable, dependent on an occlusion of the aspiration line, is determined, which is a kinematic measurement variable and/or a geometric measurement variable and/or an optical measurement variable of a particle, produced by emulsification, of the eye lens to be treated. A control unit, dependent on the evaluation variable supplied thereto, determines a control variable to control an absolute value of a parameter of the ophthalmic surgical system.
