The samples of poly(methyl methacrylate) (PMMA) were subjected to 100 keV N+ and Ar+ ion implantation up to a maximum fluence of 2 x 10(16) ions/cm(2). The effect of ion implantation on the optical energy gap and the refractive index has been studied through UV-visible spectroscopy. The results clearly indicate a decrease in the values of optical energy gap and an increase in the values of refractive index as an effect of ion implantation corresponding to both of the ions. It has also been observed that the changes induced by the implanted ions are more pronounced for N+ ions in comparison to Ar+ ions. This variation has been correlated with the calculated ranges of these ions in PMMA polymer using Stopping and Range of Ions in Matter (SRIM) code. Finally, an attempt has been made to correlate all the observed changes with the induced structural changes as revealed through Raman spectroscopy. (C) 2012 Elsevier B.V. All rights reserved.