Teaching Case

A 2-year-old child consults in the Ophthalmology Service for suspected of having strabismus. Ocular fundus examination showed a pigmented lesion in the anterior part of the left vitreous that moved freely with eye movements (Figure 1). No other abnormalities were identified

Real time B-scan ultrasound of the left eye demonstrated a spherical anechoic and well-defined lesion, with a maximal diameter of 10 mm, which was floating in the anterior portion of the vitreous (Figure 2). Color Doppler examination reveals an absence of vessels (Figure 3). The rest of the ocular ultrasound study did not show other significant alterations.

Free-floating vitreous cysts were first described by Tansley in 1899 [2, 3]. It is usually an incidental clinical or radiological finding.

It can be diagnosed at any age, but it is more frequent in children and young adults [1, 2, 7].

it has been described in the literature as single monolateral, single bilateral and even multiple monolateral. It can be diagnosed in healthy or diseased eyes, or in association with other congenital anomalies [2, 8].

Although its pathogenesis remains unclear, free-floating vitreous cyst has been classified as congenital or acquired, and a number of possible etiologies have been proposed over the last decades. Histopathological findings of Nork and Millecchia [10], suggest that congenital cysts are choristomas of the primary hyaloid system, a congenital anomaly of the eye that results from failure of embryological primary vitreous and hyaloid vasculature to regress. Acquired cysts can be associated with multiple pathologies such as intraocular infection, uveitis, retinitis pigmentosa, toxoplasmosis, and retinal detachments. They have also been described in patients undergoing eye surgeries and with a history of ocular trauma [1-9].

Generally, vitreous cysts are spherical or oval lesions, with smooth or lobed edges, and they usually measure between 0.15 - 12 mm. They may have a yellow-grey color (non-pigmented) or brown color (pigmented) [1- 4, 7, 9].

Diagnosis is easily made during a dilated-pupil fundus examination, showing a rounded or oval lesion with a cystic aspect, mobile, pigmented or not, located in the vitreous chamber [1-6]. Ocular ultrasound is the radiological test of choice, especially when the posterior chamber cannot be assessed with direct vision, for example, in patients with cataracts. Ultrasound studies reveal vitreous cysts as anechoic lesions, with well-defined edges, smooth or lobed, without vessels in the Doppler study.

Pigmented cysts can be mistaken for pigmented tumors like melanoma [11], and grey ones may resemble parasitic cysts like in cysticercosis. Clinical examination, serological tests and eye ultrasound may help to make the correct diagnosis.

Different treatments have been described in the literature for symptomatic vitreous cyst, such laser photocystotomy or pars plana vitrectomy with cyst excision [2, 6, 7, 9]. In our case, follow up was decided because our patient did not have symptoms.

Written informed patient consent for publication has been obtained.