Scleral cyst is an unusual, rare clinical condition. Most of the cases reported have described the cyst to occur at the limbus, with or without involvement of the cornea.1–3 In this case report, we describe a case of posterior scleral cyst that presented as an intraocular mass.
An 11-year-old boy was referred to our outpatient department with a diagnosis of choroidal melanoma in right eye picked up on routine fundus examination by the referring ophthalmologist. His best-corrected visual acuity was 20/20 in both eyes. Intraocular pressure was 20 mm Hg and 18 mm Hg in right and left eye, respectively. Anterior segment examination of both the eyes was normal. There was no evidence of vitreous cells on fundus examination and the optic disc was normal. A well-defined, oval, hypopigmented, elevated, subretinal lesion with a smooth surface was seen 2 disc areas in size and was located 4 to 5 disc diameters superotemporal to the optic disc (Figure 1A). No overlying pigmentation or subretinal fluid around the lesion was noticed. The lesion was brilliantly transilluminant. Its location was not in proximity to the vortex veins. Posterior segment examination of left eye was unremarkable, with presence of paving stone degeneration in the inferotemporal quadrant periphery.
(A) Fundus photograph showing a well-defined, oval, hypopigmented, elevated, subretinal lesion. (B) Fundus autofluorescence imaging showing hyperautofluorescence. (C) B-scan ultrasound showing a well-defined cystic lesion with hyperreflective walls and internal hyporeflectivity, with no evidence of retinal detachment. (D) T2-weighted parasagittal section magnetic resonance imaging showing a small hypointense lesion in the eyewall, in the superior part of the left globe, demarcated with red circle.
The lesion was slightly hyperautofluorescent (Figure 1B) on autofluorescence imaging. It showed a high surface reflectivity and an anechoic cavity corroborating to its cystic nature on ultrasonography. There was no associated retinal detachment or focal calcification within the cyst (Figure 1C).
On magnetic resonance imaging, the lesion was inconspicuous with T1-weighted image showing an isointense nodular lesion on the superior aspect of posterior choroid. T2-weighted imaging, revealed a small hypointense lesion in the coats of the eyeball (Figure 1D).
Swept-source optical coherence tomography (SS-OCT) (DRI-OCT Triton; Topcon Medical Systems, Tokyo, Japan), showed a well-defined oval lesion in the sclera with a hyperreflective wall and internal hyporeflectivity suggestive of a cyst (Figure 2). The cyst had a smooth, dome-shaped surface topography, and the posterior wall of the cyst was discernible. The choroid sclera interface over the surface of the lesion was well-delineated with attenuation of the choroidal vessels overlying the lesion. There was no associated subretinal fluid, pigment epithelium detachment, or retinal pigment epithelium atrophy. The photoreceptor layer and the inner retinal layers over the surface of lesion were intact and normal.
Swept-source optical coherence tomography imaging showing a well-defined scleral cyst with hyperreflective walls and internal hyporeflectivity, with smooth dome-shaped topography, elevating the choroid inward, compressing the choriocapillaries, with no subretinal fluid and intact photoreceptor layer.
Considering the benign nature of the lesion located in a visually inconspicuous location, no treatment other than regular follow-up was advised to the patient.
Various theories were proposed to explain the origin of the congenital and acquired variants of the scleral cyst.3 Introversion and sequestration of conjunctival or corneal epithelium developing into a cyst corroborates the presence of nonkeratinized epithelium that lines the cyst wall.1,2 Congenital cyst representing a diverticulum of the Schlemm's canal does not explain the presence of epithelium in the cyst wall. The location of cyst in adherence to the location of the embryonic fissure has also been contemplated. Sequestration and proliferation of corneal or limbal epithelial cells post trauma or surgery develops into an acquired cyst.
The case presented here is unique in that there was no history of trauma or any ocular surgery to explain the origin of the cyst. The cyst is not located along the embryonic fissure. The theory of origin of the cyst from Schlemm's canal cannot explain its posterior location. Introversion of conjunctival epithelium may possibly give rise to a cyst in such a location. Posterior scleral cysts have seldom been reported in literature. There is a mention of such a posterior scleral cyst being mistaken for a melanoma and enucleated, the diagnosis arrived at on histopathological examination. The posterior, subretinal dome shaped appearance of the lesion, appearing irregularly brown due to overlying atrophy / hypertrophy of the RPE can mimic a melanoma. Hence, a posterior scleral cyst should be considered as a differential diagnosis of a small choroidal melanoma.
The clues to diagnosis are: a) an asymptomatic patient; b) a transilluminant lesion; c) absence of associated signs of a neoplastic process, such as subretinal fluid, orange pigmentation, exudation, etc.; and d) cystic nature of the lesion seen on OCT and ultrasound. The SS-OCT, with its deeper imaging capability, was particularly useful in identifying the lesion to be scleral in location.
Characteristic features of choroidal tumors have been identified on enhanced depth imaging OCT.4 SS-OCT also facilitates exact localization of the choroidoscleral interface.5 It is unclear if this posterior scleral cyst would remain stable or would alter over time; serial follow-up is likely to shed some light.
This case report describes a postequatorial scleral cyst that may mimic a choroidal melanoma. Certain clinical features and SS-OCT are useful for elucidating the location of intraocular lesions anatomically, as well as distinguishing its structural characteristics.
- Mahmood MA, Awad A. Congenital sclerocorneal epithelial cyst. Am J Ophthalmol. 1998;126(5):740–741. doi:10.1016/S0002-9394(98)00128-7 [CrossRef]
- Bloomfield SE, Jakobiec FA, Iwamoto T. Traumatic intrastromal corneal cyst. Ophthalmology. 1980;87(9):951–955. doi:10.1016/S0161-6420(80)35141-5 [CrossRef]
- Vrolijk M. Corneoscleral cyst. Acta Ophthalmol. 1941;19:44–51. doi:10.1111/j.1755-3768.1941.tb07423.x [CrossRef]
- Shields CL, Manalac J, Das C, Saktanasate J, Shields JA. Review of spectral domain enhanced depth imaging optical coherence tomography of tumors of the choroid. Indian J Ophthalmol. 2015;63(2):117. doi:10.4103/0301-4738.154377 [CrossRef]
- Michalewska Z, Michalewski J, Nawrocka Z, Dulczewska-Cichecka K, Nawrocki J. Suprachoroidal layer and suprachoroidal space delineating the outer margin of the choroid in swept-source optical coherence tomography. Retina. 2015;35(2):244–249. doi:10.1097/IAE.0000000000000281 [CrossRef]