Sirius is a high precision instrument that is used for 3D analysis of the cornea and tomography of anterior ocular segment. It works by combining placido disk topography with Sheimpflug tomography of the anterior segment. Sirius helps in obtaining information on elevation, pachymetry, dioptric power and curvature of both corneal surfaces over a diameter of 12 nm. 25 sections of cornea help in obtaining measurements of the anterior chamber. The speed of measurement lowers the effect of eye movement, thus, generating a very good quality accurate measurement.