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Routine exam in elderly man reveals retinal lesion
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An 88-year-old white male presented for a comprehensive eye exam. He was largely asymptomatic aside from some mild asthenopia with reading. He was pseudophakic in both eyes and had had a YAG capsulotomy in the left eye.
His medical history was significant for benign prostatic hyperplasia, chronic obstructive pulmonary disease, gastroesophageal reflux disease, gout, hearing loss, hypertension, osteoarthritis and paroxysmal atrial tachycardia. He also had a right frontal lobe meningioma resulting in simple partial seizures, treated with prednisone and radiation therapy 3 years ago.
He was taking albuterol, fluticasone/salmeterol and tiotropium inhalers, aspirin and digoxin.
The patient’s visual acuity was 20/20 OD and OS. Extraocular movements and confrontation visual fields were full. IOP was normal. His anterior segment exam was normal in both eyes, and his fundus exam was normal in the right eye.
His left eye, however, had a 1 DD round creamy, yellow-white elevation with focal overlying hyperpigmentation in the inferotemporal arcade, which was surrounded by a small subretinal fluid (SRF) cuff with underlying atrophy. Fundus autofluorescence (FAF) indicated mild lesional autofluorescence, surrounding adjacent hypoautofluorescence associated with the SRF and atrophy, which was then surrounded by mild hyperautofluorescence. A B-scan indicated that the lesion had roughly homogenous hyperintensity with minimal posterior shadowing.
Fundus photo of the left eye indicating the 1 DD creamy, yellow-white elevation with surrounding atrophy.
Images: Weidmayer S
Optical coherence tomography was performed and showed an elevated choroidal lesion with eruption into the subretinal space causing overlying retinal atrophy with adjacent subretinal fluid and minimal spread beyond the lesion. Head CT scans from previous years were reviewed, and each indicated a focal hyperintensity in the left eye at the location of the lesion.
This patient was seen by an ocular oncologist and was ultimately diagnosed with choroidal osteoma that has remained stable over several years of follow up.
Differential diagnoses
There are several differential diagnoses to consider, and differentiating similar lesions can be tricky.
Amelanotic choroidal nevus, amelanotic choroidal melanoma and metastatic choroidal carcinoma, unlike osteomas, typically have ill-defined margins. Melanomas are also generally more elevated than osteomas. Choroidal lymphoma and sclerochoroidal calcifications are more likely to be multifocal and bilateral, and blood testing can help distinguish these entities. Rather than focusing on the many facets of each differential, it will be helpful in the case of osteomas to focus on the more unique characteristics of osteomas.
FAF of the left eye indicating a round lesion with mild homogenous lesional autofluorescence, surrounding adjacent hypoautofluorescence associated with SRF and atrophy, then surrounded by mild hyperautofluorescence.
The B-scan shows a hyperreflective, largely decalcified lesion with minimal acoustic shadowing.
Choroidal osteomas are rare, ossifying benign tumors of the choroid. They are formed from mature trabecular (cancellous, spongy) bone tissue with fine vessels and connective tissue that span the marrow spaces. They typically present as irregularly shaped, but well defined whitish-yellow choroidal elevations that may have small superficial networks of vascularization.
They most frequently are unilateral and juxtapapillary or macular and typically affect young females in their second or third decade, but often are seen congenitally. Their etiology is unknown, and there has been no correlation to systemic disease, genetic disorders or abnormal blood chemistries; however, they have been rarely associated with pregnancy and a history of various ocular diseases.
Choroidal osteomas have been reported to develop after intraocular inflammation, surgical procedures or laser, similar to how intraocular calcification can be seen post-inflammation or trauma; however, choroidal osteomas are associated with normal serum calcium, phosphorus and alkaline phosphatase levels.
Osteomas may grow over time and, if they do, the growth generally slowly progresses from the noncalcified margins of the tumor with arm-like projections. Interestingly, the osteoma usually decalcifies with time and can even resolve, leaving a thin yellowish remnant under atrophic RPE and choriocapillaris. This underlying atrophy leads to photoreceptor and outer retinal loss and ultimately vision loss in the affected area.
Appearance, testing
Osteomas are generally diagnosed clinically based on their appearance and with ancillary testing, which can produce characteristic signs given the calcification associated with osteomas. Calcified osteomas cause acoustic hyperreflectivity and shadowing ultrasonically, so on B-scans, calcified osteomas appear dense and highly reflective with acoustic attenuation or shadowing. Ocular malignancies, such as retinoblastomas and other tumors, will also often have calcified portions and would produce similar B-scan and CT findings.
A large echo spike will be seen on A-scan with osteomas. Similarly, the tumor will appear hyperdense, generally isodense with bone, on CT imaging; they show high intensity on T-1 weighted and low intensity on T-2 weighted MRI imaging with contrast enhancement.
Fluorescein angiography shows hyperfluorescent patchy choroidal filling with late lesional staining; other angiographic findings will depend on the degree of decalcification and RPE atrophy (hypofluorescent), choriocapillaris atrophy (defective filling), choroidal neovascularization (CNV), SRF (late leakage) and hemorrhaging (blockage).
FAF will also vary depending on numerous factors. Note that bone, even when decalcified, autofluoresces; however, depending on the FAF excitation wavelength, it may be absorbed by RPE, preventing the hyperfluorescence of calcium within the osteoma. Generally, calcified portions of the osteoma will be isoautofluorescent; partially decalcified portions will be hyperautofluorescent; and completely decalcified or atrophic areas will be hypoautofluorescent. There is increased autofluorescence in areas of lipofuscin accumulation, which is associated with metabolically stressed areas; this tends to occur at the junction of atrophic and non-atrophic retina.
The OCT indicates a largely decalcified choroidal osteoma with disorganized retinal pigment epithelium (RPE) with intraretinal migration, RPE and photoreceptor loss, adjacent choriocapillaris atrophy and posterior shadowing.
The axial CT shows focal hyperintensity in the left posterior choroid.
OCT patterns within the tumor are variable, but calcified portions of the osteoma may indicate a lattice-like pattern consistent with the arrangement of cancellous bone. The overlying retina is generally normal in structure over the calcified tumor but will show lost outer retina over decalcified or atrophic zones. Decalcified osteomas tend to produce a stacked linear pattern on OCT imaging, although partially decalcified ostomas may produce a more irregular hyperreflective pattern with posterior shadowing.
Enhanced depth imaging (EDI) OCT allows better visualization of the structures obscured by shadowing in spectral domain (SD) OCT images. With EDI-OCT, the osteoma has the same spongy reflective pattern as seen on SD-OCT, but with better visualization of the multiple layer pattern of such within the tumor: the choriocapillaris generally appears compressed, the medium and larger choroidal vascular layers appear disorganize and the osteoma is fairly transparent in that the sclerochoroidal junction is clearly visible.
Patient complaints
Patients may present with complaints of blur, visual field defects or metamorphopsia depending on the location and extent of the lesion, but up to 30% may be asymptomatic. Osteomas can lead to vision loss secondary to choroidal neovascularization (CNV), overlying serous retinal detachments or RPE and ultimately overlying retinal atrophy; the degree of visual decline certainly depends on the location of the osteoma.
Unfortunately, CNV is commonly associated with osteomas, and neovascularization can even arise from the tumor itself. SRF and subretinal hemorrhaging can occur in the absence of CNV, thought to be due to scattered focal leakage through a compromised Bruch’s membrane and RPE overlying the osteoma.
Possible treatments
The osteoma itself is benign so is generally not treated unless secondary complications occur. However, laser photocoagulation or photodynamic therapy (PDT) may help stimulate osteoclastic activity and decalcification of the osteoma itself, which may prevent further growth. However, recall that decalcification leads to overlying retinal damage.
Either treatment could be used for secondary CNV; PDT can be used for subfoveal CNV, although it may require multiple treatments; whereas photocoagulation is only appropriate for extrafoveal CNV. Anti-VEGF intravitreal injections have also been efficacious in resolving SRF associated with CNV in some cases, but this is off-label and may require a series of injections. Serous detachments not associated with CNV may respond to anti-VEGF therapy or could be treated with focal laser.
Choroidal osteomas that are raised and have protruded into the retina, particularly those that are focal, as reported here, are atypical but certainly must be considered in the differential of similar choroidal lesions. This patient’s osteoma has remained largely stable over the several years he has been under our clinic’s care.