From Istanbul University, Istanbul Faculty of Medicine, Department of Ophthalmology, Ocular Oncology Service, Istanbul, Turkey.
The authors have no financial or proprietary interest in the materials presented herein.
Address correspondence to Samuray Tuncer, MD, Istanbul University, Istanbul Faculty of Medicine, Department of Ophthalmology, Ocular Oncology Service, Capa 34390, Istanbul, Turkey. E-mail: firstname.lastname@example.org
Free-floating vitreous cysts are rare, round to oval, transparent, unilateral or bilateral, mobile intraocular cystic structures. They can be congenital or acquired.1 Congenital cysts are thought to be remnants of the hyaloidal vascular system, which are usually nonpigmented and relatively immobile. They exhibit no association with previous or concomitant ocular pathology. Acquired cysts originate from the pigmented epithelium of the iris and ciliary body, and therefore are pigmented and freely mobile. They are most often associated with trauma, intraocular inflammation due to intraocular infection (parasitic endophthalmitis, toxoplasmosis), uveitis, or degenerative diseases such as retinitis pigmentosa, retinoschisis, and chorioretinal atrophy.2
We present the clinical features, ultrasonography, and magnetic resonance imaging (MRI) findings of a free-floating pigmented vitreous cyst in a 60-year-old woman with high myopia and uveal coloboma simulating a choroidal melanoma.
A 60-year-old woman was referred with a pigmented lesion in her right eye that was suspected to be a choroidal melanoma. The patient complained of a floater in the central visual field of her right eye for 10 years that had worsened over time. Ocular history revealed indirect trauma to her right eye (due to severe non-penetrating trauma to the right side of her nose by a cow’s horn) that occurred 10 years prior. The visual acuity was hand motions in the left eye, possibly due to severe myopic maculopathy. In the right eye, the visual acuity was 20/100. Slit-lamp examination demonstrated inferior iris coloboma and aphakia with no signs of intraocular inflammation.
Funduscopy showed peripapillary atrophy and posterior staphyloma due to degenerative myopia, choroidal coloboma in the inferior hemispheric portion of the fundus (Fig. 1A), and a pigmented preretinal mass measuring 7 mm in diameter and 3 mm in thickness located under the inferotemporal vascular arcade when the patient was in the upright position. The lesion appeared to be freely mobile and cystic with clear contents, and had a thin, pigmented wall. There were some glial remnants overlying the lesion that could reflect the previous site of attachment (Fig. 1B). Ultrasonography confirmed that the lesion was cystic with low-echogenicity, freely mobile, and located in the posterior vitreous (Figs. 1C and 1D). MRI taken in another center before referral showed a well-defined, nodular preretinal intraocular lesion that was hypointense in both T1- and T2-weighted, non-contrast axial images. There was minimal contrast enhancement in T1-weighted, axial, post-contrast image (Fig. 2). A diagnosis of free-floating pigmented vitreous cyst was made, and there has been no change in 3 years of follow-up.
Figure 1. (A) Color Fundus Photograph of the Right Eye Showing the Peripapillary Atrophy and Posterior Staphyloma Due to Degenerative Myopia, and the Superior Edge of the Large Inferior Choroidal Coloboma (arrow). (B) An Inferiorly Located Pigmented Preretinal Mass Was Visible Just Behind the Iris. The Mass Appeared to Be Freely Mobile, Was Cystic with Clear Contents, and Had a Thin, Pigmented Wall. Glial Remnants that Probably Reflect the Previous Site of Attachment Were Visible Overlying the Tumor (arrow). (C) Ultrasonography Confirmed that the Inferiorly Located Lesion Was Cystic and Freely Mobile with No Attachment to the Inner Ocular Structures. (D) Following Supine Positioning, Ultrasonography Showed that the Lesion Floated Superiorly over the Optic Disc.
Figure 2. Magnetic Resonance Imaging Findings of the Free-Floating Vitreous Cyst Demonstrated a Well-Defined, Nodular Preretinal Intraocular Lesion over the Optic Disc in the Right Eye. Note that the Eyes Are Myopic with Increased Anteroposterior Diameter (egg-Shaped Contour). (A) The Lesion Was Hypointense in T1-Weighted, Axial, Non-Contrast Image. (B) The Lesion Was Hypointense in T2-Weighted, Axial, Non-Contrast Image. (C) The Lesion Showed Minimal Contrast Enhancement in T1-Weighted, Axial, Post-Contrast Image.
Intraocular cysts most often occur in the anterior segment and arise from the iris pigment epithelium. Four types of intraocular cysts are recognized and are named according to their location. These are pupillary margin, mid-zone of iris, iridociliary sulcus, and free-floating cysts. Free-floating vitreous cysts are exceedingly rare.3
Considering their pigmented nature, the literature focuses on the hyaloidal vascular system remnants, iris pigment epithelium, and ciliary body in the possible etiopathogenesis of these vitreous cysts. Under electron microscope, pigmented vitreous cysts have shown a heavily pigmented single cuboidal layer of cells containing large, spherical melanin granules resembling the iris pigment epithelium. These findings led the authors to hypothesize that the cyst was due to trauma.4 Several theories other than trauma include cystic growths at the site of a coloboma that enter the vitreous, or a vitreous reaction to underlying retina or choroidal degeneration.5
In our case, the history of indirect ocular trauma coincides with the appearance of her symptoms. Thus, it seems that trauma may be specifically related as a possible cause for this free-floating vitreous cyst in the presence of predisposing ocular structural abnormalities, including high myopia and uveal coloboma. Hyaloid system was also considered as the possible origin by documenting Mittendorf’s dot, Bergmeister’s papillae, and a vitreous cyst confined within the Cloquet’s canal.6 In our case, the pigmented nature of the free-floating cyst and the absence of any hyaloid system remnants suggested that it arose from the iridociliary sulcus and subsequently dislodged into the posterior vitreous.
The differential diagnosis of intraocular cysts includes congenital iris epithelial, post-traumatic (penetrating ocular injury) epithelial, parasitic (cysticercosis), and neoplastic (retinoblastoma, medulloepithelioma, and ectopic lacrimal choristoma) cysts.7 In adulthood, pigmented vitreous cysts can be rarely misdiagnosed as choroidal melanoma.8 Benign evolution, long and stable clinical history, intermittent nature of symptoms (floaters), absence of any signs of ocular inflammation (vitritis), and funduscopic appearance and imaging (ultrasonography and MRI) findings consistent with mobile cystic vitreous structure with no attachment to the underlying retina/choroid help the clinician in the diagnosis of a pigmented vitreous cyst.
Ultrasonography is a useful procedure in differentiating a choroidal melanoma from various simulating lesions. With this technique, a typical choroidal melanoma demonstrates a non-mobile choroidal mass pattern with acoustic hollowness (low-to-medium internal echogenicity) and choroidal excavation. On the other hand, a free-floating vitreous cyst shows a freely mobile vitreous lesion pattern with low-echogenic internal reflectivity and posterior vitreous location with no attachment to the inner ocular surface.
MRI is also important in the differentiation of a vitreous cyst from a choroidal melanoma. MRI findings of the free-floating vitreous cyst in our patient are probably the first to be reported in the literature. They have distinctive features from a choroidal melanoma. Most uveal melanomas are hyperintense to vitreous in T1-weighted images and hypointense to vitreous in T2-weighted images. The tumor shows marked enhancement after injection of a contrast material. In contrast, the vitreous cyst in our case was hypointense to vitreous in both T1-weighted and T2-weighted images, with minimal contrast enhancement. The lesion had a distinct clear cystic structure over the surface of the retina with no attachment to the inner ocular surface.
Management of vitreous cysts depends on the patient’s symptoms and degree of visual impairment. Vitreous cysts are generally asymptomatic and require no treatment. Some cysts may cause intermittent visual field defects.
We have described a unique case of an acquired pigmented free-floating vitreous cyst in a patient with high myopia and uveal coloboma in the presence of a previous history of indirect ocular trauma. Benign evolution, long and stable clinical history, intermittent nature of symptoms (floaters), cystic appearance on funduscopy, ultrasonography findings (a freely mobile vitreous lesion pattern with low-echogenic internal reflectivity and posterior vitreous location with no attachment to the inner ocular surface), and MRI findings (a cystic vitreous structure that was hypointense in both T1- and T2-weighted images with no attachment to the underlying retina/choroid) helped us in diagnosing a pigmented vitreous cyst and to differentiate it from a choroidal melanoma.
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