Abstract
Purpose: :
Choroidal osteoma (CO) was regarded as a rare benign intraocular tumor. However, an increasing number of reports from different regions of the world suggest the incident of CO may be much higher than predicted. The etiology and pathophysiology of CO remain largely unknown. We studied the retinal functions and fundus changes in CO patients.
Methods: :
Dark- and light-adapted full field electroretinograms (ERGs), including S- and M-/L-cone ERGs, multifocal ERG, color vision tests were performed in eyes at early and late stages of CO. Routine eye examinations, FP, FFA, ICG, OCT, CT and ultrasonic B-scan tests were also conducted.
Results: :
A diagnosis of CO was confirmed with CT and ultrasonic B-scan tests. At the advanced stages of CO, FP showed four concentric lesion rings with different colors. ICG also showed four well-defined concentric rings corresponding to lesion rings observed in the FP. An area of decalcification was evident in the center of the lesion. At the early stages of CO, less concentric rings were seen and no decalcification was observed. At the late stages, full field ERGs and multifocal ERGs indicated slightly decreases of rod system functions and moderately decrease of cone system functions. Interestingly, S-cone driven responses were severely decreased by 62-68%, while M-/L-cone driven responses were moderately decreased by 43-52%. In consistent with ERG findings, color vision test showed loss of blue color vision. Despite apparent fundus changes at the early stages, ERG measurements and color vision were normal.
Conclusions: :
We proposed that fundus lesion rings in CO may represent four underling eccentric pathological processes: infiltrations of osteoblasts, ossification, calcification, decalcification and bone resorption. It is generally accepted that loss of visual functions in the late stages of CO is a consequence of retinal pigment epithelium atrophy or/and secondary choroidal neovascularization. Here, we provide the first piece of evident that photoreceptors are affected during the development of the diseases. More interestingly, the S-cones are more vulnerable than other photoreceptors in CO.
Keywords: electroretinography: clinical • tumors • imaging/image analysis: clinical