Cysticercosis is a tissue infection caused by the larval stage of the tapeworm Taenia solium, which typically occurs after consumption of food contaminated by human feces that contain eggs. It is commonly seen in individuals residing in Africa, Asia, and Latin America. When affecting the eye, cysticercosis can invade the orbit or structures in the anterior or posterior segment.1 Cases of intraocular cysticercosis are rare, and in this report, we describe a case of a subretinal cyst secondary to intraocular cysticercosis and describe our surgical technique for successful cyst drainage and extraction.
A 16-year-old male presented with new-onset blurred vision in his right eye. He had traveled to Nicaragua 3 weeks prior. Visual acuity was 20/25 in the right eye (OD) and 20/20 in the left eye (OS). Intraocular pressures and anterior segment examination were normal in both eyes (OU). There was a translucent subretinal cyst superior to the optic nerve OD with adjacent subretinal fluid and circumferential retinal pigment epithelium (RPE) atrophy (Figure 1A). Funduscopic exam OS was unremarkable. Fluorescein angiography (FA) revealed early phase staining of the cyst wall, late-phase pooling of fluorescein in the subretinal space, and window defects in the area of surrounding RPE atrophy (Figure 1B). B-scan confirmed a subretinal lesion with medium to high reflectivity (Figure 1C). An optical coherence tomography (OCT) image showed a well-demarcated cystic lesion in the subretinal space (Figure 2A).
(a) A subretinal cyst is seen superior to the optic nerve with adjacent subretinal fluid and circumferential retinal pigment epithelium (RPE) atrophy in the right eye without macular or optic nerve involvement. (b) Fluorescein angiography shows early phase staining of the cyst wall, late-phase pooling of fluorescein in the subretinal space, and window defects in the area of surrounding RPE atrophy. (c) An irregularly shaped lesion is seen with medium to high reflectivity with adjacent subretinal fluid on B-scan. (d) Stable retinal atrophy is seen in the area of the previous cyst with attached retina and normal macula.
(a) The optical coherence tomography (OCT) scan delineates a cystic lesion in the subretinal space with hyperreflective material and adjacent subretinal fluid. (b) Postoperative OCT demonstrates secondary retina / retinal pigment epithelium / choroid in the area of the previous cyst. (c) OCT 5 months postoperatively of the macular region reveals no epiretinal membrane formation.
Neuroimaging and serology for cysticercosis and toxocariasis were negative. However, due to the degree of retinal damage, surgical intervention was pursued to excise the cyst in attempts to mitigate further inflammation and avoid any worsening of vision. A three-dimensional (3-D), heads–up-assisted, 25-gauge pars plana vitrectomy (PPV) was performed. First, induction of the posterior vitreous detachment (PVD) was performed. Triamcinolone was used stain the vitreous and help lift the anterior hyaloid face. A flexible loop was used to grasp and successfully lift the vitreoretinal interface without the use of pharmacological vitreolysis.2 After the vitrectomy was completed, diathermy was used to access the subretinal cyst through the creation of a retinotomy. The subretinal fluid was abnormally thick and viscous. The cyst was noted to be markedly adherent to the RPE and underlying choroid. Bimanual surgery with an endoilluminator was performed after several attempts at extraction. The sclerotomy was enlarged and the cyst was externalized in total. Fluid-air exchange and 18% C3F8 followed. Due to the extent of RPE atrophy, the posterior location of the cyst, and the presence of a complete PVD, no laser was deemed necessary. Subtenon's triamcinolone injection was administered at the end of the case to reduce inflammation (Supplemental Video).
Histopathology was consistent with intraocular cysticercosis (Figure 3). Repeat serological testing in the postoperative period was negative. Five months postoperatively, the patient's vision is 20/20 OD with mild, non-visually significant cataract formation, an attached retina, no cystic structures, no epiretinal membrane, and no intraocular inflammation (Figures 1D, 2B, and 2C).
A well-demarcated cyst is seen that is encapsulated by collagenous material, as highlighted with positive trichrome staining, with cilia-like processes within, surrounded by degenerated fibrillar tissue. This was morphologically consistent with cysticercosis.
In cases of intraocular cysticercosis, posterior segment involvement is most common and can manifest as vitreous cysts, retinal cysts, or subretinal cysts. The parasite reaches the posterior segment of the eye through the choroidal circulation, after which it can lodge into the subretinal space, perforate, and enter the vitreous cavity, inciting inflammation throughout the process. Once the larva is encysted, it undergoes a life-cycle. Initially, the cyst can contain a live, well-defined scolex. However, with time, the larva begins to die, and toxins are released through the permeable cyst wall, leading to adjacent retinal inflammation. This is known as the colloidal vesicular stage and likely the stage that was seen in our patient. Lastly, when the larva is dead, it is resorbed, eventually calcifies, and enters the calcified nodular stage.1
The diagnosis of cysticercosis is largely clinical, but serological testing, imaging, and histopathological analysis can be useful for further elucidation. Serology can oftentimes be negative, and imaging in these cases plays a larger role. Imaging modalities that can be applied include ultrasonography or magnetic resonance imaging, which can reveal well-defined cysts with central hyperintensities, likely reflecting the tapeworm's scolex. Histopathology typically shows cystic structures containing scolex tissue. In our patient, hooklets were not seen on cross-sections of the cyst, but the overall appearance of the cyst was most consistent with cysticercosis.1,3
Long-term sequelae of untreated ocular cysticercosis can include secondary glaucoma, cataract formation, hypotony, anterior chamber inflammation, vitreous exudation, chorioretinitis, exudative or rhegmatogenous retinal detachments, proliferative vitreoretinopathy or ultimately phthisis. As such, timely treatment of the intraocular cysticercosis is emphasized. Medical therapy is recommended for orbital forms of the condition; however, surgery is the treatment of choice for anterior and posterior segment cases. Anti-helminthic medication can incite inflammation if the live cyst is degenerating and must therefore be used judiciously; steroids are typically employed before and after surgery to quell inflammation.1
The goal of vitreoretinal surgery in these cases is to remove the cysts in total and ensure that the contents do not extrude and incite inflammation. Sharma et al. showed that in a series of 45 patients with subretinal cysts from ocular cysticercosis, 86.6% of cases had successful removal of cysts with either a trans-scleral or transvitreal approach. A trans-scleral approach was used for subretinal cysts anterior to equator while a transvitreal approach was used for cysts posterior to equator or in the vitreous, as in our case.4 In vivo cyst lysis is traditionally employed as a last resort in attempts to mitigate intraocular inflammation; however, a series by Azad et al. proposed early cyst lysis with subsequent aspiration as a surgical technique for removal with anatomical success in 13 of 15 cases.5
In our case, a transvitreal approach using the 3-D, heads–up-assisted vitrectomy enhanced the visualization quality of the posterior hyaloid (during PVD induction) and cyst structures as recognized by the experienced surgeon (AMB). Intraoperative OCT can assist surgeons in identifying the location and precise depth of the cystic structures within the retinal and choroidal tissue. However, we could not use intraoperative OCT simultaneously with the 3-D, heads-up system that we had at our institution. Common surgical approaches of transvitreal extraction do not address removal of the cyst when it is tightly adherent to the RPE and choroid, as in this case. After several attempts for its removal, the best option was the bimanual use of forceps and curved scissors to cut the cyst at its base with a chandelier. The visual outcome was very favorable with minimal inflammation.
- Dhiman R, Devi S, Duraipandi K, et al. Cysticercosis of the eye. Int J Ophthalmol. 2017;10(8):1319–1324.
- Cernichiaro-Espinosa LA, Berrocal AM. Novel surgical technique for inducing posterior vitreous detachment during pars plana vitrectomy for pediatric patients using a flexible loop. Retin Cases Brief Rep. 2017Nov22. doi: . [Epub ahead of print] doi:10.1097/ICB.0000000000000664 [CrossRef]
- Li JJ, Zhang LW, Li H, Hu ZL. Clinical and pathological characteristics of intraocular cysticercosis. Korean J Parasitol. 2013;51(2):223–229. doi:10.3347/kjp.2013.51.2.223 [CrossRef]
- Sharma T, Sinha S, Shah N, et al. Intraocular cysticercosis: Clinical characteristics and visual outcome after vitreoretinal surgery. Ophthalmology. 2003;110(5):996–1004. doi:10.1016/S0161-6420(03)00096-4 [CrossRef]
- Azad S, Takkar B, Roy S, Gangwe AB, Kumar M, Kumar A. Pars plana vitrectomy with in vivo cyst lysis for intraocular cysticercosis. Ophthalmic Surg Lasers Imaging Retina. 2016;47(7):665–669. doi:10.3928/23258160-20160707-09 [CrossRef]