History
The presentation of ocular cysticercosis varies based on cyst location, from asymptomatic to vision loss or disturbance and a moving sensation in the eye. Redness, photophobia, and pain may occur. Epileptiform seizure can occur if the CNS is infected.
Physical
Ocular cysticercosis may affect almost all eye tissues. The vitreous cavity, subretinal space, and subconjunctival space are common sites, while involvement of other regions (eg, extraocular muscles, optic nerve) is relatively less common. [8]
While either eye may be affected, bilateral involvement is rare. [11] Multiple cysts may develop in the same eye. [12]
Ocular manifestations may be devastating as the cysticercus enlarges. The cysticercus, if left untreated, may lead to blindness in 3-5 years. [13] Decreased vision, pain, and recurrent redness of the involved eye are common symptoms of intraocular cysticercosis.
Clinically, the cyst appears as a well-defined translucent mass with a dense white spot (scolex) at one region. When alive, the cyst appears motile due to larval invagination or evagination. The cyst measures between 1.5 and 6 disc diameters and might undulate under the examining light. This motility is absent if the larvae are dead. A live cyst can induce intraocular inflammation because of its motility. Cyst death causes the release of toxic products, which induce a severe zonal granulomatous inflammatory reaction. The cyst becomes less translucent with a surrounding inflammatory membrane.
Up to 46% of patients with ocular cysticercosis present with the cyst in the subretinal space or vitreous cavity, where it can be observed ophthalmoscopically. [14] The site of entry into the eye is the posterior ciliary arteries, from which the cyst migrates into the subretinal space, bores a hole in the retina, and enters the vitreous cavity. This passage incites inflammation, leaving behind a chorioretinal scar. [15] Other sites of entry include the ciliary and retinal blood vessels. Within the vitreous cavity, the cyst may be free-floating [16, 17] and may produce vitritis.
Apart from uveitis, [18] cysticercosis may also lead to retinal hemorrhages, proliferative vitreoretinopathy, retinal detachment, disc edema, cyclitic membrane formation, and phthisis. In individuals with intense inflammation in which the cyst cannot be clinically visualized, imaging modalities help in making the diagnosis.
Cysticerci may develop in the anterior chamber. In these instances, they may produce iridocyclitis and secondary glaucoma. [19] The cyst may be freely mobile or may be attached by inflammatory membranes to surrounding structures, such as the cornea, lens capsule, or iris. [20] The cyst may enter the anterior chamber either from the posterior ciliary arteries or from the angle. Intraocular inflammation may also cause cataract formation [21] and iris atrophy.
Subconjunctival cysticercosis usually presents as a painful, yellowish, nodular subconjunctival mass with surrounding conjunctival congestion. Spontaneous extrusion of an anterior subconjunctival cyst has been reported. [22, 23] Subconjunctival cysticercosis may even present as an eyelid nodule.
Acquired strabismus, diplopia, recurrent redness, and painful proptosis are some of the clinical signs in patients with orbital cysticercosis. One or more extraocular muscles may be simultaneously involved, although a propensity for involvement of the superior muscle complex and the lateral rectus muscles has been reported. [24, 25] Depending on the muscle involved, clinical findings of Duane retraction syndrome or Brown syndrome may be observed. Blepharoptosis may occur due to the presence of the cyst in the superior muscle complex. An intraorbital cyst may cause decreased vision due to external compression of the eyeball. [26]
Optic nerve compression by the cyst may cause decreased vision and disc edema. Optic nerve cysticercosis produces similar symptoms. [25] Lacrimal canalicular obstruction due to adnexal cysticercus has also been reported. [27]
Causes
Factors facilitating the spread of T solium infection include inadequate sanitation, breeding pigs in unsanitary conditions, and eating uncooked pork.
Risk factors include a family history of parasitic infestation, history of travel to an endemic area, or household visitors from an endemic area.
Complications
Excessive intraoperative dissection of the subconjunctival cyst may damage the extraocular muscle fibers, leading to postoperative diplopia and strabismus.
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CT scanning of the orbit demonstrating cysticercus within the medial rectus muscle observed as a hypodense area with a central hyperdensity suggestive of the scolex.
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B-scan ocular ultrasonography demonstrating cysticercus within an extraocular muscle observed as a well-defined cystic mass with a central hyperechoic area.
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MRI of the orbit demonstrating deep orbital cysticercus within superior muscle complex observed as a hypointense area with central hyperintensity compressing the optic nerve posteriorly.
