Description

A 31-year-old woman presented with right eye sudden loss of vision of 15 days duration. On examination, the best corrected visual acuity was 20/600 in the right eye and 20/20 in the left eye. Bilateral anterior segment examination was normal. Right eye fundus showed hazy media due to vitritis (grade 2), with a thin subretinal translucent cyst attached to optic disc with bright white spot (scolex) at its edge, suggestive of subretinal cysticercosis (figure 1A). Left eye fundus was unremarkable. There was history of eating undercooked pork. She was started on oral anti-helminthics and oral steroids. She underwent pars plana vitrectomy with in toto removal of cyst. Neuroimaging ruled out any intracranial cysticercosis.

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Figure 1

Serial fundus photographs at day 1 (A), day 3 (B), 1 week (C), 2 weeks (D) showing changing shape of cyst with position of scolex. (D) Overlying retinitis through which the cyst has travelled (red arrow).

When the patients serial fundus photographs at day 3 (figure 1B), 1 week (figure 1C) and 2 weeks (figure 1D) were reviewed, an interesting observation was noted; when the scolex was present at the edge of the cyst, it was fixed and formed an irregular oval shape (figure 1A–C) but when the scolex was at the centre of the cyst, it was mobile and formed a perfect sphere (figure 1B–D). Also, the overlying retinitis (red arrow) clearly demarcated the path travelled by the cyst.

Cysticercosis is a parasitic infestation caused by larval form of cestode tapeworm Taenia solium. It is considered endemic in India.1 The parasite may get access to posterior segment of the eye through the choroidal circulation and reaches subretinal space. The larvae may stay there itself (subretinal) or reaches vitreous cavity after perforating through overlying retina.2 3 The diagnosis of intraocular cysticercosis is mainly clinical where a live cyst can be seen as a translucent white cyst in the vitreous cavity or subretinal space. Differentials include non-pigmented vitreous cyst, Coats disease, diffuse unilateral subacute neuroretinitis and hydatid cyst. On illumination with bright light, cyst wall may show undulating movements due to mobile scolex. The vitality of parasite is established by looking at undulating movements of scolex, periodic evagination of scolex, motility of the cyst and postoperative examination of parasite.4 However, the relationship between the scolex and shape of cyst has not been reported prior in the literature.

We observed, the spherical shape corresponds to a free-floating mobile cyst and the oval shape relates to a fixed cyst. Possible explanation is when the scolex is fixed at one end, it pushes the intracystic fluid to opposite end making it oval and when the scolex is in the centre, intracystic fluid is distributed all around it making it spherical. A free-floating mobile cyst in subretinal space can migrate transretinally into the vitreous cavity. Thus, knowing the shape of cyst may help in better surgical planning and avoiding intraoperative mishaps. This may help in surgical planning of the cyst removal, as a fixed cyst is easier to locate and remove compared with a free-floating mobile one.