Purpose: To evaluate the retinal status overlying choroidal osteoma using optical coherence tomography (OCT)., Design: Retrospective noncomparative case series., Participants: Twenty-two eyes with choroidal osteoma., Methods: Choroidal osteoma was studied with fundus photography, ultrasonography, and OCT., Main Outcome Measure: Retinal status over the calcified and decalcified portions of choroidal osteoma., Results: There were 8 completely calcified and 14 partially decalcified choroidal osteomas. Optical coherence tomography was performed over the calcified portion in 21 eyes and over the decalcified portion in 10 eyes. The calcified portion displayed an overlying intact inner retina (n = 21 [100%]), intact outer retina (n = 20 [95%]), and intact photoreceptor layer (n = 21 [100%]). In contrast, the decalcified portion showed an intact inner retina (n = 9 [90%]) and markedly thinned to absent outer retina and photoreceptor layers (n = 10 [100%]). Of the 18 eyes with subfoveolar choroidal osteoma, visual acuity (VA) was 20/20 to 20/50 in all 11 eyes with calcified tumor, and OCT confirmed preservation of retinal architecture. In contrast, VA was 20/200 or worse in all 7 eyes with subfoveolar decalcified tumor, correlating with OCT findings of outer retinal thinning and photoreceptor loss., Conclusions: The retina shows profound outer layer thinning and photoreceptor loss over decalcified choroidal osteoma. These findings correlate with poor VA over decalcified subfoveolar choroidal osteoma compared with good VA over calcified subfoveolar tumor.