Ophthalmic Surgery, Lasers and Imaging Retina

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Surgical Removal of Intraocular Parasite in a Patient With Diffuse Unilateral Subacute Neuroretinitis

Anne L. Kunkler, MD; Nimesh A. Patel, MD; Nathan L. Scott, MD; Jayanth Sridhar, MD; Daniel Vitor Vasconcelos-Santos, MD, PhD; Thomas A. Albini, MD

Abstract

Diffuse unilateral subacute neuroretinitis (DUSN) is a rare ocular infectious disease caused by migrating larvae of a nematode. DUSN is often a diagnostic challenge as it is difficult to identify the pathogenic nematode on funduscopic examination because it moves frequently and often resides within the subretinal space. Herein, the authors present a patient with unilateral, chronic visual loss who was noted to have a live, motile worm within the vitreous cavity. Initial attempts to treat with laser photocoagulation were unsuccessful. In the accompanying video, the authors report the first case of a live intraocular parasite successfully removed with pars plana vitrectomy.

Abstract

Diffuse unilateral subacute neuroretinitis (DUSN) is a rare ocular infectious disease caused by migrating larvae of a nematode. DUSN is often a diagnostic challenge as it is difficult to identify the pathogenic nematode on funduscopic examination because it moves frequently and often resides within the subretinal space. Herein, the authors present a patient with unilateral, chronic visual loss who was noted to have a live, motile worm within the vitreous cavity. Initial attempts to treat with laser photocoagulation were unsuccessful. In the accompanying video, the authors report the first case of a live intraocular parasite successfully removed with pars plana vitrectomy.

Daniel Vitor Vasconcelos-Santos, MD, PhD

Daniel Vitor Vasconcelos-Santos, MD, PhD

The authors present an interesting case of a middle-aged woman with fundus features consistent with late-stage diffuse unilateral subacute neuroretinitis (DUSN), characterized by decreased vision to hand motions in the right eye and a live nematode larva that was found moving on the retinal surface. Although initial laser photocoagulation was unsuccessful, the authors were able to remove the motile larva by surgically aspirating into a vitreous cutter. DUSN is typically associated with a subretinal motile nematode larva, with migration to the vitreous being exceedingly rare. Treatment consists of direct laser photocoagulation of the organism when possible, or systemic anti-helminthic therapy such as oral albendazole.

The particularly unique aspect of this case is the observation of a live, moving larva within the vitreous months after the subretinal insult that resulted in optic and chorioretinal atrophy as well as subretinal fibrosis. Difficulties with laser photocoagulation of this highly motile intravitreal “target” led the surgeons to an elegant transvitreal approach. Key aspects of the surgery include clamping the infusion line to minimize vitreous turbulence and deferring the lifting of the posterior hyaloid before aspiration of the organism. The initial unsuccessful attempt to aspirate the larva with a soft tip cannula from above was followed by successful aspiration from the side with a vitreous cutter attached to a syringe on manual suction. The authors are to be congratulated for their refined and ingenious technique. This is a rare opportunity to surgically address an intravitreal moving larva that may have caused even more intraocular damage if were not removed in a timely manner.

Daniel Vitor Vasconcelos-Santos, MD, PhD

Adjunct Professor of Ophthalmology and Head of Uveitis

Universidade Federal de Minas Gerais

Belo Horizonte, Brazil

Nimesh A. Patel

Nimesh A. Patel

Anne L. Kunkler

Anne L. Kunkler

Thomas A. Albini

Thomas A. Albini

Nathan L. Scott

Nathan L. Scott

Jayanth Sridhar

Jayanth Sridhar

A 54-year-old woman presented with 4 months of progressive vision loss in her right eye. She was originally from Honduras and lived in Louisiana for the previous 12 years. At presentation, her visual acuity was hand motions in the right eye and 20/25 in the left. An afferent pupillary defect was present on the right side. Anterior segment exam was unremarkable in both eyes. Posterior exam in the right eye was significant for mild vitritis, optic atrophy, and numerous yellow chorioretinal atrophic and fibrotic changes in the macula and posterior pole. A live, motile, intravitreal parasite was identified to reside on the surface of the retina. Posterior exam was unremarkable in the left eye.

We initially attempted to immobilize the parasite using laser photocoagulation with indirect ophthalmoscopy; however, this was unsuccessful due to its residing anterior to the retina and the absence of pigmentation. The decision was then made to remove the worm surgically using 23-gauge pars plana vitrectomy (PPV). An attempt to remove the parasite was made with a soft tip cannula attached to a syringe with the infusion line clamped, but this was ultimately futile. An alternate method was trialed by means of a vitreous cutter, with the aspiration line connected to a syringe, to approach the parasite from the side rather than from above. With success, the organism was removed from the eye alive and was confirmed to be moving within the specimen syringe (see Video below).

Discussion

Originally described by Gass et al. in 1978, DUSN presents with varying degrees of vitritis, papillitis, and gray-white retinal lesions depending on early or late stage at presentation.1,2 A subretinal nematode is identified on examination in only 25% to 40% of cases.2,3 Various parasites have been reported as the etiologic agent of DUSN, including Toxocara canis, Baylisascaris procyonis, and Ancylostoma caninum; however, most reports do not present conclusive evidence on the specific organism.3

To our knowledge, this case represents the first report of surgical removal of a live intravitreal worm in a patient with DUSN. Given the chronicity of symptoms, our patient likely had significant retinal atrophy, which allowed the worm to break through the retina and reside beneath the posterior hyaloid. Brasil et al. described the only other reported case in which the larva had migrated through the retina and was found entrapped within the vitreous.4 The suspected etiology of the worm was B. procyonis based on serology, as the patient was lost to follow-up before any intervention could be performed.

Surgery intervention was performed on the same day as the initial presentation. This was important because the organism may escape visualization if treatment was delayed; our patient was previously seen by multiple ophthalmologists without a diagnosis. The infusion remained clamped at the outset of the case to prevent fluid shifts, as this had potential to create turbulence and prevent visualization of the nematode for extraction. The hyaloid was not lifted prior to securing the organism in the specimen syringe in light of this concern.

Prior literature of case reports involving surgical removal of a worm from the eye have only been reported within the subretinal space. De Souza et al. recovered a subretinal nematode intact with a PPV approach in a young patient due to poor cooperation with standard laser treatment.5 In this procedure, the authors first encircled the subretinal nematode with endolaser. A retinotomy was then created, and the nematode was aspirated in its entirety with a 20-gauge silicone-tipped needle on manual suction. A similar approach was unsuccessfully attempted in our patient with a soft tip and syringe before switching to using the vitreous cutter.

It is unfortunate for us to report that the sample was lost in route to surgical pathology before any further analyses could be performed. Based on consultation with our infectious disease specialists, the etiologic parasite is presumed to be Baylisascaris based on its pattern of motility and size. The patient was subsequently treated with high-dose oral albendazole (Albenza; Impax Laboratories, Hayward, CA) (200 mg twice a day) for 28 days in the postoperative period. Her vision never improved beyond count fingers.

In conclusion, DUSN is a vision-threatening ophthalmic infectious disease. Early identification and treatment are key in preventing vision loss. In rare cases where the organism has migrated into the vitreous cavity, immediate removal with PPV may be the preferred treatment.

References

  1. Gass JD, Gilbert WR Jr, Guerry RK, Scelfo R. Diffuse unilateral subacute neuroretinitis. Ophthalmology. 1978;85(5):521–545. doi:10.1016/S0161-6420(78)35645-1 [CrossRef] PMID:673332
  2. de Amorim Garcia Filho CA, Gomes AH, de A Garcia Soares AC, de Amorim Garcia CA. Clinical features of 121 patients with diffuse unilateral subacute neuroretinitis. Am J Ophthalmol. 2012;153(4):743–749. doi:10.1016/j.ajo.2011.09.015 [CrossRef] PMID:22244523
  3. Arevalo JF, Arevalo FA, Garcia RA, de Amorim Garcia Filho CA, de Amorim Garcia CA. Diffuse unilateral subacute neuroretinitis. J Pediatr Ophthalmol Strabismus. 2013;50(4):204–212. doi:10.3928/01913913-20121211-03 [CrossRef] PMID:23244243
  4. Brasil OF, Lewis H, Lowder CY. Migration of Baylisascaris procyonis into the vitreous. Br J Ophthalmol. 2006;90(9):1203–1204. doi:10.1136/bjo.2006.095323 [CrossRef] PMID:16929065
  5. de Souza EC, Nakashima Y. Diffuse unilateral subacute neuroretinitis. Report of transvitreal surgical removal of a subretinal nematode. Ophthalmology. 1995;102(8):1183–1186. doi:10.1016/S0161-6420(95)30892-5 [CrossRef] PMID:9097745
Authors

Anne L. Kunkler, MD, can be reached at Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 900 NW 17th St., Miami, FL 33131; email: alk145@miami.edu.

Nimesh A. Patel, MD, can be reached at Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 900 NW 17th St., Miami, FL 33131; email: nimeshpatel300@gmail.com.

Nathan L. Scott, MD, can be reached at Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 900 NW 17th St., Miami, FL 33131; email: nls67@med.miami.edu.

Jayanth Sridhar, MD, can be reached at Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 900 NW 17th St., Miami, FL 33131; email: jsridhar1@med.miami.edu.

Daniel V. Vasconcelos-Santos, MD PhD, can be reached at Faculdade de Medicina da Universidade Federal de Minas Gerais, Av. Alfredo Balena 190 sala 199, Belo Horizonte, MG 30130-100, Brazil; email: dvitor@ufmg.br or dvitorvs@gmail.com.

Thomas A. Albini, MD, can be reached at Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 900 NW 17th St., Miami, FL 33131; email: talbini@med.miami.edu.

Disclosures: Dr. Sridhar is a consultant for Alcon, DORC, Regeneron, and Oxunion outside the submitted work. Dr. Albini is a consultant for Allegro, Eye Point Pharmaceuticals, Allergan, Beaver-Visitec, Adverum Biotechnologies, Novartis, Santen Pharmaceutical, Genentech, Valleaut Pharmaceuticals, Notal Vision, Janssen Biotech, Regenex Bio, and Clearside Biomedical. The remaining authors report no relevant financial disclosures.

10.3928/23258160-20201202-10

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