Pigmented Free-floating Vitreous Cyst

Introduction

Intraocular cysts have been classified as those that occur in the anterior chamber, retrolental space, or vitreous cavity. This condition is generally seen in patients between the ages of 10 and 20 years, although it has been known to occur in patients as young as 6 to 8 years. Presentations include single unilateral, single bilateral, and multiple unilateral. Cyst dimensions range from 0.15 to 12 mm, with shapes described as spherical, oval, or lobulated and a smooth or sharp surface. Cysts can have a yellow-gray (nonpigmented) or brown (pigmented) appearance.^1–3

Case Report

A 45-year-old man reported a mobile shadow in his left central visual field for the preceding 4 months. He had no pertinent medical history. He denied any previous trauma or ocular surgery.

Ophthalmological examination revealed a visual acuity of 20/20 in both eyes. Slit lamp biomicroscopy showed a healthy anterior segment, with no signs of inflammation, and iris translucency, transparent media, isochoric and photoreactive pupils, and a clear vitreous. Intraocular pressure was 16 mm Hg bilaterally.

Funduscopy of the right eye did not reveal any abnormality. A brownish, oval-shaped structure was observed floating in the vitreous cavity in the left eye. The macula and peripheral retina appeared normal. Fundus photography (Figure 1A–B) showed a translucent cyst with a smooth, brown-pigmented surface. B-scan ultrasound (Figure 1C–D) of the left eye demonstrated an oval-spherical hypoechogenic structure with a 4.2-mm maximal diameter floating at the posterior pole, unattached to any other ocular structures. No calcification was seen.

Figure 1. (A–B) Fundus photography of the left eye shows a normal macula and a pigmented, oval-shaped cyst with a smooth brown-pigmented surface floating in the posterior vitreous cavity. (C–D) An oval-spherical hypoechogenic mass with a 4.2-mm maximal diameter was detected by real-time B-scan ultrasound of the left eye.

The differential diagnoses for this condition include Toxoplasma gondi, Toxocara, echinococcosis, and cysticercosis. A complete physical examination, imaging studies, and blood tests were performed in order to rule out these causes. Observation was recommended. Over the past 6 years, no changes have been observed.

Discussion

Although the origin of intraocular cysts is still debated, free-floating vitreous cysts have been classified mainly as congenital and acquired. Congenital cysts can originate from remnants of the hyaloid artery or glial remnants of Bergmeister’s papilla, although they are occasionally detected in otherwise healthy eyes. Acquired vitreous cysts have been found in patients affected by degenerative diseases such as retinitis pigmentosa, choroidal atrophy, retinoschisis, uveitis, toxoplasmosis, parasitic vitritis, and endophthalmitis due to nematodes. However, the etiology of cyst development is not clear. Other authors have indicated that these could be ciliary adenomas that have become detached in the vitreous, newly arising formations in the anatomic structure of a coloboma, or a vitreous reaction to chorioretinal degenerations.^1–5

Congenital vitreous cysts are rare findings and frequently asymptomatic. Visual acuity is usually normal in patients with these cysts, which require only regular observation. The etiology continues to be idiopathic. The mean age of presentation varies between 5 and 68 years. Differentiating between congenital and acquired vitreous cysts is important in order to establish an adequate therapeutic approach.

However, there are limited data concerning the treatment of this condition. Awan⁶ successfully used argon laser to treat a congenital cyst that caused disabling visual symptoms due to its location in the visual axis, collapsing and dispersing the pigment granules in the vitreous cavity, without recurrence. Gupta et al² applied a simple laser photocystotomy with single-frequency Nd:YAG in an 8-year-old girl with a free-floating pigmented cyst in the anterior vitreous that was causing a large, visually disturbing floater. The procedure resulted in a reduction in the size of the cyst but persistence of the floater. An attempt at further laser fragmentation of the cyst resulted in iatrogenic cataract formation.

Orellana et al¹ aspirated a cyst via the pars plana. This treatment is contraindicated in patients who are asymptomatic or whose symptoms are not severe. The option of pars plana vitrectomy is reserved for cases in which disabling symptoms persist after laser photocystotomy.

Our patient denied intravitreal injections, trauma, ocular surgery, travel abroad, or systemic inflammation during the past few years. The cyst could correspond to a congenital cyst dislocated spontaneously or by trauma (not referred). Although symptoms had not been reported previously by the patient, the growth of cysts over years is a rare occurrence that remains a possibility in this case. Pigmented cysts are believed to originate from the pars ciliaris, whereas nonpigmented cysts are likely to be derived from the remnants of the hyaloidal artery system.^1,3–5

Further studies are needed to fully understand the pathogenesis of pigmented free-floating vitreous cysts.