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 Table of Contents  
Year : 2022  |  Volume : 2  |  Issue : 2  |  Page : 485-487

Highly motile intravitreal worm in epiretinal plane: Is surgical removal the only option?

1 Vitreo Retina Services, Aravind Eye Hospital, Thavalakuppam, Pondicherry, India
2 Department of Vitreo Retina Services, Aravind Eye Hospital, Thavalakuppam, Pondicherry, India

Date of Submission03-Oct-2021
Date of Acceptance25-Oct-2021
Date of Web Publication13-Apr-2022

Correspondence Address:
Divya Yadav
Vitreo Retina Services, Aravind Eye Hospital, Thavalakuppam, Pondicherry - 605 007
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijo.IJO_2532_21

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A 37-year-old-man presented with the perception of wriggling movements in the left eye. The fundus revealed a highly motile nematode epiretinally. The location and plane of the movements were confirmed with optical coherence tomography (OCT), which also showed its intraretinal attachment. Multiple attempts of laser photocoagulation failed due to its incessant rapid movements in the antero-posterior axis. Immediate vitrectomy was deferred due to the risk of breakage. With combination therapies of peribulbar lignocaine and oral anti-helminthics for 2 days, a marked reduction in the motility, thickening, and swelling was noticed and it could finally be killed with laser. To the best of our knowledge, this is the first case report of a live intravitreal worm treated non-invasively.

Keywords: Intravitreal worm, ocular parasitoses, posterior segment nematode

How to cite this article:
Yadav D, Sonawane N, Singh HV. Highly motile intravitreal worm in epiretinal plane: Is surgical removal the only option?. Indian J Ophthalmol Case Rep 2022;2:485-7

How to cite this URL:
Yadav D, Sonawane N, Singh HV. Highly motile intravitreal worm in epiretinal plane: Is surgical removal the only option?. Indian J Ophthalmol Case Rep [serial online] 2022 [cited 2022 May 24];2:485-7. Available from: https://www.ijoreports.in/text.asp?2022/2/2/485/342964

Diffuse unilateral subacute neuroretinitis (DUSN), first described in the 1960s, is an ocular infection caused by several nematodes, including Toxocara canis, Baylisascaris procyonis, and Ancylostoma caninum[1] Gass et al.[2] first gave a mention of a mobile subretinal worm as “successive crops of evanescent lesions” in the deep retinal layers, which faded over several days, leaving color changes in the pigment epithelium. It was later proven that a motile subretinal nematode is responsible for severe inflammation in such cases. The eggs may enter inside the human body through the respiratory or oral route. The patient can present with early or late manifestations. The acute stage is characterized by mild to severe inflammation manifesting as vitritis, optic nerve head edema, retinal pigment epithelial alterations, and/or deep retinal edema. The late manifestations include disk pallor, vascular sheathing or sclerosis, pigment epithelial tracts, and atrophic patches.[3] The clinical presentation can be similar irrespective of the sizes of the worm, which can vary, the smaller type being approximately 500 μm and the longer ones measuring between 1500 and 2000 μm.[4] Here, we describe non-invasive management of a worm in the vitreous, partly present intraretinally.

  Case Report Top

A 37-year-old-man presented with the perception of wriggling movements in front of his left eye for 2 days. The best-corrected visual acuity was 20/20 in both eyes. The anterior segment examination was unremarkable with normal intraocular pressure bilaterally. The right eye fundus examination was normal while the left eye examination revealed a highly motile worm over the retinal surface near the supero-temporal arcade with multiple depigmented tracts [Figure 1]a and [Figure 1]b. The patient was immediately shifted to the laser room for direct killing with a green laser. The location and plane of movements were confirmed to be epiretinal on OCT, which also showed the attachment of an end of the worm intraretinally (presumed head with hooklets) [Figure 2]a. Multiple attempts of direct laser photocoagulation (power: 200–350 mW, duration: 200 ms) over the head region failed due to its incessant rapid movements in three-dimensional space, especially in the antero-posterior axis [Video 1][Additional file 1]. The patient was started on oral albendazole 400 mg once daily. Failed attempts of chemo-paralysis with peribulbar and retrobulbar lignocaine were made to intoxicate and immobilize the worm for 2 consecutive days with multiple laser sessions. The main challenge here was the inability to focus and deliver a laser shot due to the swift movements of the worm in multiple axes. With no immediate results, the patient was planned for pars plana vitrectomy, which also did not seem to be a feasible option here due to the high risk of breakage and inability to remove the intraretinal portion. On the following day, i.e., after 2 days of combination therapy with anti-helminthics, periocular lignocaine, and laser attempts, there was a remarkable reduction in the motility, the worm was now thicker, swollen, and sluggish [Figure 2]b, and therefore, could finally be killed with direct laser photocoagulation [Figure 1]c. Further follow-up demonstrated dissolving the dead remains of the worm followed by complete resolution of inflammation [Figure 1]d and [Figure 2]c, [Figure 2]d.
Figure 1: (a) Fundus image of the left eye shows the nematode wriggling over the retinal surface (white square, worm zoomed in inset), diffuse depigmented retinal pigment epithelial changes are seen in the background. (b) Laser edema following an unsuccessful attempt at direct laser killing (black arrow). (c) Fundus image of the left eye shows dead swollen nematode over the retinal vessel (white arrow). (d) Laser scars indicating multiple laser attempts (black arrows)

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Figure 2: (a) OCT showing the slender epiretinal location of the worm. The intraretinal attachment can be appreciated well. (b) OCT showing thickened epiretinal worm with posterior vitreous cells, intraretinal and subretinal fluid. (c) OCT showing disintegrating worm, resolution of posterior vitreous cells, intraretinal fluid, and neurosensory detachment (d) Completely dissolved worm remnants with residual scarring

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  Discussion Top

Being highly motile, nematodes can move from the original location from the time of examination to the time of laser treatment, and therefore, make re-finding them very difficult. It is, therefore, crucial to immediately perform a laser as soon as it is located. Both Neodymium-doped Yttrium Aluminum Garnet (Nd: YAG) and argon lasers have previously been used for the same.[5] In our case, unsuccessful laser shots, however, might have helped to break the blood-retinal barrier to reach high-dose oral anti-helminthics into the vitreous. OCT can be used to locate the exact plane where the worm lies. The evidence in various layers of the retina and in the subretinal space indicates that the worm may move freely through different layers. Although the subretinal worm can easily and effectively be killed by direct laser photocoagulation, the presence of the intravitreal worm requires surgical removal. Oral albendazole, thiabendazole, and diethylcarbamazine have been used with variable success.[6],[7],[8] There are a few techniques described in the literature for in toto removal of the worm-like syringe with a plunger to aspirate it, an angiocath needle connected to the viscous fluid extraction tubing for gentle and controlled aspiration, etc.[9],[10] However, we faced a special situation where the worm could be seen freely moving over the retinal surface. The diagnosis was not effortful here as the patient had very precise symptoms and the worm was clearly seen in the absence of the vitritis. As we confirmed the epiretinal location of the worm on OCT, a part of it was also noticed to be anchoring intraretinally which we presumed to be the head. There are hitherto no reports of similar presentation and its management. We went ahead with multiple unsuccessful sessions of hitting the presumed head of the worm with the green laser, the main challenge being unable to focus and deliver laser beam due to its incessant rapid movements, even of the head, in a relatively free space compared to the subretinal space which is usually too compact to exhibit swift motion. Moreover, the worm was slender and thready which made identifying the head difficult clinically. The pars plana vitrectomy did not seem to be a sure shot choice here as there was an inevitable risk of breakage and incomplete removal due to its intraretinal attachment. Here, we could successfully manage to kill the worm with a combination of oral anti-helminthics, peribulbar lignocaine, and double frequency Nd-YAG laser followed by oral and topical steroids which helped in promptly achieving good structural as well as the functional outcomes.

  Conclusion Top

Combination therapy with oral anti-helminthics, periocular lignocaine, and laser to disrupt blood-retinal barrier may be an effective way to paralyze a highly motile epiretinal worm, which can subsequently be shot dead with laser in a non-invasive way.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Mazzeo TJ, Dos Santos Motta MM, Curi AL. Diffuse unilateral subacute neuroretinitis J Ophthalmic Inflamm Infect 2019;9:1-8.  Back to cited text no. 1
Gass JD, Gilbert WR Jr, Guerry RK, Scelfo R. Diffuse unilateral subacute neuroretinitis. Ophthalmology 1978;85:521-45.  Back to cited text no. 2
Gass JDM, Braunstein RA. Further observations concerning the diffuse unilateral subacute neuroretinitis syndrome. Arch Ophthalmol 1983;101:1689-97.  Back to cited text no. 3
Garcia CA, Sabrosa NA, Gomes AB, Segundo Pde S, Garcia Filho CA, Sabrosa AS. Diffuse unilateral subacute neuroretinitis-DUSN. Int Ophthalmol Clin 2008;48:119-29.  Back to cited text no. 4
Garcia CA, Gomes AH, Garcia Filho CA, Vianna RN. Early-stage diffuse unilateral subacute neuroretinitis: Improvement of vision after photocoagulation of the worm. Eye 2004;18:624-7.  Back to cited text no. 5
Barisani-Asenbauer T, Maca SM, Hauff W, Kaminski SL, Domanovits H, Theyer I, et al. Treatment of ocular toxocariasis with albendazole. J Ocul Pharmacol Ther 2001;17:287-94.  Back to cited text no. 6
Maizels RM, Yazdaubakhsh M. Immune regulatory by helminth parasites: Cellular and molecular mechanisms. Nature Rev 2003;3:733-44.  Back to cited text no. 7
Souza EC, Casella AM, Nakashima Y, Monteiro ML. Clinical features and outcomes of patients with diffuse unilateral subacute neuroretinitis treated with oral albendazole. Am J Ophthalmol 2005;140:437-45.  Back to cited text no. 8
Basak SK, Sinha TK, Bhattacharya D, Hazra TK, Parikh S. Intravitreal Live Gnathostoma spinigerum. Indian J Ophthalmol 2004;5257-8.  Back to cited text no. 9
Lee J, Chung S-H, Lee SC, Koh HJ. A technique for removal of a live nematode from the vitreous. Eye 2006;20:1444-6.  Back to cited text no. 10


  [Figure 1], [Figure 2]


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