A method to compute optical errors subject to temperature variations in the optical components is presented. In general, temperatures, displacements and stresses at arbitrary located FE nodes can not be input directly into optical software. This paper discusses integrated techniques coupling finite element analysis and optical design software. The theory of the method is Zernike polynomials are useful to describe optical surface deformations and wave-front error due to thermal variations and mechanical stress. Thus Zernike polynomials act as the data transmission tool between optical and finite element analysis programs. The coefficient of Zernike polynomials as computed by which we designed codes may be output as CODE V files to evaluate the mechanical effects on the optical performance. An example is demonstrated for thermo-elastic affects the optical performance of a primary mirror of Cassegrain telescope.