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LETTER TO THE EDITOR
Year : 2014  |  Volume : 62  |  Issue : 8  |  Page : 899-901

Live Subretinal Nematode: Management by Focal Argon Laser Photocoagulation with Spectral Domain OCT Analysis


1 Department of Ophthalmology, Lotus Eye Care Hospital, Coimbatore, Tamil Nadu, India; Department of Ophthalmology, Vita-Salute University, San Raffaele Scientific Institute, Via Olgettina 60, 20132, Milan, Italy
2 Department of Ophthalmology, Lotus Eye Care Hospital, Coimbatore, Tamil Nadu, India

Date of Web Publication18-Sep-2014

Correspondence Address:
Ashish Sharma
Consultant Retina and Research, Lotus eye Care Hospital, Coimbatore, Tamil Nadu

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0301-4738.141081

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How to cite this article:
Sheth J, Sharma A, Sundaramoorthy S. Live Subretinal Nematode: Management by Focal Argon Laser Photocoagulation with Spectral Domain OCT Analysis . Indian J Ophthalmol 2014;62:899-901

How to cite this URL:
Sheth J, Sharma A, Sundaramoorthy S. Live Subretinal Nematode: Management by Focal Argon Laser Photocoagulation with Spectral Domain OCT Analysis . Indian J Ophthalmol [serial online] 2014 [cited 2020 Jul 7];62:899-901. Available from: http://www.ijo.in/text.asp?2014/62/8/899/141081

Sir,

Diffuse unilateral subacute neuroretinitis (DUSN) is a rare form of ocular larva migrans associated with damage to outer retinal layers and retinal pigment epithelium (RPE) by motile parasitic worms such as Ancylostoma caninum, Toxocara canis, Ascaris lumbricoides, Baylisacaris procyonis, and Dirofilaria spp. [1],[2],[3],[4] We report a case of DUSN in a 37-year-old male, who presented with sudden onset of decreased vision in OS since one week. His best corrected visual acuity (BCVA) was 6/6, N 6 (OD) and 4/60, N 36 (OS). The OD examination was unremarkable. Fundus examination of OS revealed mild vitritis, multiple RPE de-pigmented patches, multifocal evanescent gray-white lesions in outer retina along with multifocal neurosensory detachment (NSD) involving macula. A glistening white, non-segmented motile worm approximately 2 disc diameter (~3000 μm) with tapered ends was located in supero-temporal quadrant outside temporal arcade [Figure 1]a with track marks in inferior quadrant [Figure 1]b. Snake-like wriggling movements of worm increased on light stimulation by fundus photography [Figure 1] c-d. Fluorescein fundus angiography (FFA) revealed multiple RPE leaks with window defects and pooling of dye in NSD's [Figure 2]. Spectral domain-optical coherence tomography (SD-OCT) demonstrated NSD's over macula and surrounding area with unhealthy RPE [Figure 3]a.
Figure 1: Fundus picture showing the location and track marks of live subretinal worm

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Figure 2: Fundus fluorescein angiography showing punctuate hyerfluorescent areas which leak as the phases of angiograph proceed suggestive of unhealthy retinal pigment epithelium

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Figure 3: Spectral domain OCT showing pre laser appearance of subretinal worm along with sequential events post laser photocoagulation starting from early inflammation and late scarring

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Argon laser barrage (Zeiss Inc.; 45 spots, 200 mW, 200 μ, 350 ms) of 532 nm was performed in an attempt to restrict mobility of worm [Figure 4]a. The worm showed increased movements in an attempt to come out of barraged area [Figure 4]b-d. When it succeeded [Figure 4]e, it was killed directly by laser (15 spots, same settings; [Figure 4]f. Although, the effect of laser barrage may take 1-2 weeks, continuous evaluation on experimental basis was done to gauge its effectiveness by limiting further worm migration, for which we had restricted favorable result, as the worm could migrate out of the barraged area only after 15 minutes of coiling and uncoiling effort. Pre-laser 3D SD-OCT revealed the worm as subretinal coiled hyper-echogenic structure [Figure 3]b while immediately post-laser, it showed intense laser reaction in form of hypoechogenic areas [Figure 3]c. Single dose of oral albendazole 400 mg along with tapered dose of oral prednisolone (starting from 60 mg/day) and diethylcarbazine 100 mg three times/day were given for 3 weeks.
Figure 4: Fundus photograph showing worm movements (coiling and uncoiling) during the process of laser photocoagulation along with complete destruction of worm on follow-up revealed by scar formation

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Next day, a small streak of blood was seen along the vessel in region of worm [Figure 4]g. SD-OCT findings showed minimal increase in OCT thickness compared to the previous day, which could be due to inflammatory reaction [Figure 3]d. Though investigation including blood and stool was negative.

On day 10 of post-laser, BCVA was stagnant at 4/60. Fundus examination demonstrated minimal vitritis, faded laser spots and dead worm (Interrupted white line; Black arrowhead in [Figure 4]h. 3D SD-OCT revealed sub retinal fibrosis in lasered region [Figure 3]e.

On day 25, BCVA was unchanged. The vitritis resolved with complete disintegration of worm [Figure 4]i. SD-OCT shows fibrotic scar [Figure 3]f-g along with normal foveal contour with damaged photoreceptor and RPE [Figure 3]h. The patient was lost to follow-up following this visit.

Direct killing of worm with laser has been associated with significant increase in intraocular inflammation. [2] In other parts of body, systemic treatment may be associated with fever, myalgia and headache. [5]

There has only been a single correspondence regarding post-laser OCT analysis of worm. [6] We have utilized 3D SD-OCT imaging technique to analyze post-laser worm degradation along with retinal inflammation secondary to worm toxins and laser.

In conclusion, our report adds to an existing data [2],[3],[4] for laser photocoagulation being used as first line of management for cases of DUSN, in which live worm can be identified. OCT is an additional tool other than fundus photograph, which may be helpful in understanding the amount of photoreceptor and RPE destruction caused by worm, which may not be visible on fundus photographs. It can be proposed as another vital non-invasive modality in our armamentarium along with fundus photographs to image the eyes with DUSN.

 
  References Top

1.
Myint K, Sahay R, Mon S, Saravanan VR, Narendran V, Dhillon B. ''Worm in the eye'': The rationale for treatment of DUSN in south India. Br J Ophthalmol 2006;90:1125-7.  Back to cited text no. 1
    
2.
Albert MD, Miller WJ, Azar TD, Blondi AB. Albert and Jakobiec's Principles and Practice of Ophthalmology. 3 rd ed, Vol 2. Philadelphia: Saunders Elsevier; 2008. p. 2135-40.  Back to cited text no. 2
    
3.
Gass JD, Braunstein RA. Further observations concerning the diffuse unilateral subacute neuroretinitis syndrome. Arch Ophthalmol 1983;101:1689-97.  Back to cited text no. 3
[PUBMED]    
4.
de Souza EC, da Cunha SL, Gass JD. Diffuse unilateral subacute neuroretinitis in South America. Arch Ophthalmol 1992;110:1261-3.  Back to cited text no. 4
    
5.
Dunyo SK, Nkrumah FK, Simonsen PE. A randomized double-blind placebo-controlled field trial of ivermectin and albendazole alone and in combination for the treatment of lymphatic filariasis in Ghana. Trans R Soc Trop Med Hyg 2000;94:205-11.  Back to cited text no. 5
    
6.
Ahmed E, Houston MA, Husain D. High-definition spectral domain OCT of a subretinal nematode. Eye (Lond) 2010;24:393-4.  Back to cited text no. 6
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