The present work addresses a demand for cationically UV-curable optically transparent monomers and oligomers with high photopolymerization activity and high refractive indexes (RIs). Two novel kinds of epoxy silicones, carbazole-bound epoxy tetramethylcyclotetrasiloxane (Ep-Cz-Si) and carbazole-bound epoxy methylhydrogen silicone oil (Ep-Cz-SiO), were synthesized from 1,3,5,7-tetramethylcyclotetrasiloxane (D4H) and methylhydrogen silicone oil (HHSiO), respectively. Their structures were confirmed by proton nuclear magnetic resonance (H-1 NMR) and Fourier transform infrared (FT-IR) spectroscopy. Ep-Cz-Si and Ep-Cz-SiO show strong self-photosensitizing effects in photopolymerization and can be photoinitiated directly by a common onium salt photoinitiator under a high-pressure mercury lamp. The RIs of Ep-Cz-Si and Ep-Cz-SiO improve with increasing carbazole content. The photocured networks from Ep-Cz-Si and Ep-Cz-SiO show good thermal stabilities.