A scheme is proposed for the automatic control of tolerance sensitivity during the course of lens optimization. The criteria used in the scheme involve the lens form parameters (S and W) suggested by Sasian and Descour, which quantify the symmetry of the optical system and the optical power distribution among the individual lens elements. It is demonstrated that design results with smaller values of S and W tend to achieve better aberration balance. Thus systems of small S and W values can usually provide good image quality with loose tolerances to manufacturing errors. A test program is developed using the Macro-PLUS language in CODE V. A penalty function is added to the error function for optimization in order to reduce the values of S and W during the automatic design process. Results of manufacturing simulations are given for systems optimized with or without the penalty function, which show that our scheme can successfully reduce the tolerance sensitivity of the design results.