The refractive index for a family of optical glasses (tellurite containing halide) has been analyzed. From the dielectric theory, the relationship between the refractive index and number of ions/unit volume (N/V) with polarizability α has been discussed. Halogen substitution resulted in a lower dielectric constant, along with lower density and lower refractive index. The reduced number of polarizable ions per unit volume was primarily responsible for the reduction in the dielectric constant, although reductions in electronic polarization also affected the dielectric properties.