By Paul T. Finger, MD
Choroidal osteoma can grow within the eye. These bone-like tumors arise within the blood-vessel layer “choroid” beneath the retina. Choroidal osteoma are usually found near the optic nerve and can cause vision loss. The choroidal osteoma impedes the circulation to (and harms) the overlying retina and can be associated with adjacent subretinal neovascularization.
A choroidal osteoma will tend to be relatively flat (less than 2 mm thick), lightly pigmented, with well-defined and scalloped edges. Clumps of black or brown pigment can be seen on the choroidal osteoma surface. Choroidal osteoma can be associated with the development of subretinal neovascularization (particularly at the edges of the osteoma). Periodic observation of patients with choroidal osteoma for growth and the development of subretinal neovascularization is warranted.
Choroidal osteoma is characterized by bone in the choroidal vascular layer of the eye. These bone deposits are more likely to be found near to the optic nerve.
When your eye care professional looks into your eye, a typical choroidal osteoma will appear like a yellow subretinal tumor near the optic nerve. Pigment can be seen to dust its surface. The choroidal osteoma typically has well defined scalloped edges. Hemorrhage near the edge of a choroidal osteoma suggests the presence of subretinal neovascularization.
Photography is used to document the choroidal osteoma size and shape. Baseline photographs are helpful for subsequent evaluations for growth and neovascularization.
Fluorescein angiography: Since a choroidal osteoma is made of bone, when fluorescein dye circulates through the eye, it will be slow to penetrate the tumor. Once the fluorescein dye is inside the choroidal osteoma, it also has trouble getting out. This is why the fluorescein pattern of choroidal osteoma is one of slow uptake and persistent “late” fluorescence.
Ultrasound: Ultrasound examination of an eye with a choroidal osteoma will demonstrate intense reflectivity from the tumor and shadowing of the posterior orbital contents. If the intensity (gain) of the ultrasound machine is decreased, the eye-care specialist is likely to see persistent reflectivity or “brightness” from the tumor. Ultrasound can also be used to measure the thickness of a choroidal osteoma.
Radiographic imaging: Computed tomography (CT) can be particularly helpful to see the calcification of a choroidal osteoma in unusual cases.
Choroidal osteoma is a benign tumor; therefore, most patients do not require treatment. Choroidal osteoma related vision loss is not usually treatable. On occasion, a choroidal osteoma may be associated with subretinal neovascularization (abnormal blood vessels beneath the retina), which are typically treated with laser. Treatment can cause a small blind spot, but is used to protect central vision.
Eye tumor specialists request that choroidal osteoma is monitored with periodic dilated ophthalmoscopic examinations.