Mie computations are performed to evaluate light scattering on the virtual microstructures relevant to lithium disilicate glass internal crystallisation. The computations are expressed in the form of optical transmission (OT) patterns evolved on a scale of growing lithium disilicate crystals. Input data include the crystals number density, their size, the wavelength of the incident electromagnetic radiation, the indices of refraction of the lithium disilicate glassy and crystalline phases and the thickness of the virtual glass slab. In the computations, the spherical shape of crystals and their random distribution are assumed. The results reveal the quantitative effects of individual input data constants on the overall course of the computed OT patterns. They also relate the computed OT data magnitudes to the corresponding glass crystallinity (α). In addition, they point to singular combinations of the input data constants defining the conditions under which the OT data could potentially stand for the kinetically important α data. Finally, the results aid better recognition of some fundamental as well as practical properties of the optical thermal methods based on the optical transmission measurements.