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Ocular Toxocariasis
Introduction
Helminths have been causing disease in human beings for since long.[1] Helminths are divided into phylum, Nemathelminthes, and Platyhelminths. Nematodes are a class of Nemathelminthes that include human worms (Ascaris lumbricoides, Trichuris trichiura), animal worms (Toxocara canis, Toxocara catis), and filarial worms (Wuchereria bancrofti). Platyhelminths are divided into trematodes (Schistosoma mansoni) and cestodes (Taenia solium). Worldwide around 1 billion people are infected with helminths.[2]
They are pathogenic to humans. They parasitize the intestine and cause tissue damage by direct invasion. Ocular toxocariasis is a zoonotic infection. It is caused by the nematode Toxocara canis and Toxocara cati.[3] In 1950, Wilder described the ocular infection caused by a nematode.[4] She studied 46 enucleated eye specimens and found nematode larva in 24 of them. Beaver, in 1952, identified the Toxocara larva in the liver biopsies of children.[5] Nichols in 1956 demonstrated T. canis in 24 enucleated eye specimens.[6]
These findings implicated Toxocara as a common etiology for systemic and ocular pathology. Ocular toxocariasis may present with peripheral granuloma, posterior granuloma, or endophthalmitis. This review discusses etiology, epidemiology, pathophysiology, clinical features, investigations, differential diagnoses, management, complications, and the role of interprofessional coordination for patients with ocular toxocariasis.
Etiology
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Etiology
Ocular toxocariasis is caused by Toxocara. The Toxocara genus consists of 21 species.[7] Toxocara canis species is the most common cause of toxocariasis.[8] It is a natural parasite of dogs. The adult worms are cylindrical. The length of adult male worms is 42.5 to 45 mm, and female worms are usually 54 to 60 mm long.[9]
Puppies are the definitive host.[7] Adult worms are found in the small intestine of puppies and pregnant dogs. The puppies get infected either through maternal transmission or through ingestion of contaminated soil and feces. Inside them, the larva reaches the lungs. These larvae are coughed up and swallowed. They then reach the small intestine and quickly mature into adult worms that produce infectious ova. These eggs are shed in the feces.[10]
The eggs mature into an embryo in 2-6 weeks in the external environment. Humans get infected through the ingestion of contaminated soil or contaminated food. The embryo reaches the intestine and matures into a larva. The larva penetrates the intestinal wall and enters the systemic circulation. It is then carried to various organs like the heart, liver, lungs, and eyes.[11]
Epidemiology
Ocular toxocariasis is widespread around the world. According to the National Health and Nutrition Examination Survey (NHANES, 1988-1994), 13.9% of the US population was seropositive for Toxocara. But the recent NHANES (2011-2014) data reported 5.1% seropositivity.[12] Seropositivity was higher in blacks than whites.[13] It is prevalent in warmer areas such as the Southern United States.[14] According to a study, 45% of Toxocara patients belonged to this region.
In other parts of the world, the antibody titer against Toxocara was found to be positive in 2.4% to 76.6% of individuals.[15] Seroprevalence above 80% was reported among the children in some regions of Nigeria.[16] It is generally seen in the younger population. The median age of infection is 11.5 years (1 to 66 years).[17] The majority of them are male. According to a study, 69% of patients had a history of contact with a dog or a cat, 85% reported vision loss, and 70% had permanent vision loss.[18]
Pathophysiology
Humans get infected after ingestion of eggs or larvae through contaminated vegetables or uncooked meat. Close contact with puppies or soil infested with embryonated eggs can lead to accidental ingestion of eggs.[19][20] The perianal region of dogs is a reservoir of embryonated eggs. The dogs also harbor the eggs in their fur. According to a study, puppies harbor many eggs on their hair at densities higher than in the soil.[21] Thus direct contact with puppies can lead to infection of T. canis.[22] Sometimes people get infected after consumption of uncooked contaminated raw meat of chicken and cows.[23][24] After ingestion, the eggs reach the small intestine. There they turn into larva. The larva penetrates the intestinal wall and enters the systemic circulation.
The body tries to contain the infection by inciting an eosinophilic granuloma around the parasite.[25] It tries to contain the Toxocara parasite within the granuloma. Toxocariasis can manifest in the form of visceral larva migrans and ocular toxocariasis. The clinical manifestation depends upon host immunity, the severity of inflammatory response, the quantity of larva ingested, and organ localization.[26] Eosinophilia is often present in Toxocara infection. The greater the degree of exposure greater is the eosinophil count.[27]
Histopathology
The eosinophilic granulomas are often multiple, with central necrosis surrounded by eosinophils, neutrophils, lymphocytes, epithelioid histiocytes, and/or giant cells. They are present predominantly around the blood vessels. Charcot-Leyden crystals are often present. Remnants of parasites might be present in some cases. Serologic test for Toxocara may be positive. Immunohistochemical staining using polyclonal antisera against Toxocara larvae demonstrates positivity in macrophages in sixty percent of cases.[25]
History and Physical
Ocular toxocariasis generally affects young children. A history of close contact with a dog, cat, or soil contamination is usually present. The average age of presentation is eight years.[28] It is generally not seen in adults and very young children.[29]
Most of the time, the children do not complain. The parents notice ocular changes, including a deviation of the eye (squinting), white (leukocoria), and redness. Children may present with unilateral loss of vision, redness, and pain. Vision may range from 20/80 to perception of light (PL).[30][31][32] The slit-lamp evaluation may reveal anterior chamber cells, flare, cataract, and retrolental cells.[33]
Retinal findings can manifest in 3 forms. The patient can present with any manifestation.
- Peripheral granuloma presents as an elevated white mass in the periphery with surrounding vitreal membranes, pigmentation, and tractional detachment. The usual age of onset is 6 to 40 years. A fold of membrane may extend from the peripheral granuloma to the posterior pole.[34][35] This traction band can cause macular displacement and optic neuropathy. Generally, there is no vitritis.[31] The prognosis is usually good. Children present with unilateral leukocoria, vision loss, or squint. A very young child may not present as the disease is peripheral and visual acuity is good.[34] It is most commonly found incidentally after an ophthalmic examination. Adults present with unilateral loss of vision.[36]
- Posterior granuloma presents as a solitary elevated yellow-white mass at the posterior pole (at macula or around the optic disc) ranging from 0.5 to 3 disc diameter. The patients are usually 6 to 14 years old. Usually, the intraocular inflammation is absent or minimal. Generally, it is well defined and lies in the subretinal space.[37] But when the disease is active, it appears as an ill-defined mass with surrounding exudates and hemorrhage.[34] Traction bands may form in between the granuloma and the surrounding retina. Vision loss occurs by macular or optic disc involvement, epiretinal membranes, retinal folds, or choroidal neovascularization.[34]
- Endophthalmitis: The usual age at presentation is 2 to 9 years. Patients present with signs of severe inflammation, pain, redness, watering, and photophobia.[20][38] There is intense vitritis that may preclude posterior segment visualization. The slit-lamp examination shows flare and cells in the anterior chamber. The intraocular pressure may be lower than normal. Peripheral granuloma or grayish-white exudates may be hazily seen near the pars plana.
The diagnosis of ocular Toxocara is mainly clinical, supported by antibody testing to Toxocara. The disease, if untreated, can cause complications like cataracts, glaucoma, tractional retinal detachment, macular scarring, and phthisis bulbi.[26][39][40]
Evaluation
Ocular toxocariasis is suspected if a child presents with unilateral loss of vision or squint. Definitive diagnosis is made by the demonstration of Toxocara larva in the histological sections of the affected tissue.[41] In ocular infection, the retinal biopsy is not feasible, so this test is rarely performed.[42][43] Thus the diagnosis is mainly clinical and presumed most of the time without histopathology or other direct confirmation.[44] When in doubt, as in cases presenting with endophthalmitis, ultrasonography (USG) B scan or computed tomography (CT) scan can be done.
USG shows a hyperreflective retinal mass located in the posterior pole or periphery. Often, vitreous membranes are noted to be adherent to the mass with or without calcification.[45] If calcification is present, it is focal and limited and does not involve the whole vitreous as in retinoblastoma.[46] The fibrous band extending from the periphery to the posterior pole or optic disc may also be demonstrated. In a healed peripheral and posterior pole granuloma, a CT scan shows a focal or diffuse, non-enhancing, well-defined hyperdense lesion.[47]
Immunological tests can be done for the diagnosis of toxocariasis. The enzyme-linked immunosorbent assay (ELISA) test, which employs antigens of the second-stage larva (usually excretory/secretory antigens), is the best indirect test for diagnosing the infection. It is a qualitative immunoenzymatic determination of antibodies against the Toxocara. ELISA may show cross-reactivity with Ascaris lumbricoides which can be minimized by using excretory/secretory antigens for the assay. ELISA has a high degree of sensitivity (78%) and specificity (92%) at a titer of more than 1:32.[48] However, serum ELISA may be negative in ocular toxocariasis.[49] ELISA on the aqueous and vitreous aspirate may improve the rate of detection. Positive ELISA reports may be noted in patients with past infections or asymptomatic Toxocara infection. A significant rise in antibody level over time confirms active infection.
Complete blood count may show eosinophilia.[50] Other indirect indicators are hypergammaglobulinemia (IgM) and an elevated isohemagglutinin titer. In humans, the intestinal form of toxocariasis does not occur, so stool studies for parasites and ova may not be helpful.[51] Tissue biopsy may show a granuloma surrounding a larva but is rarely recommended. Thus, the constellation of clinical signs described above, a history of pets, pica, eosinophilia, and positive serology, strongly point to the diagnosis.
Serum total immunoglobulin-E (IgE) level may be markedly raised in patients with toxocariasis, though the titer may be lower in ocular toxocariasis due to reduced worm burden.
Treatment / Management
Ocular toxocariasis can present with or without active inflammation. In cases with anterior chamber cells/flare and vitritis, the inflammation must be controlled with topical and systemic corticosteroids. This helps in reducing anterior chamber reaction, vitreous haze, and vitreous membranes.[52]
Topical cycloplegic mydriatic prevents posterior synechia formation and seclusio pupillae. Increased intraocular pressure can be controlled with topical antiglaucoma medications. The role of systemic anthelmintic drugs such as albendazole and thiabendazole is unclear. It is not proven to kill intraocular Toxocara.[53][54] Though some cases have been described in the literature showing favorable results in combination with oral corticosteroids.[55][56][57] (B3)
In one study, treatment resulted in an improved vision in all patients. There were no recurrences of uveitis during the study period of 13.8 months. In adults, the dose of albendazole was 800 mg orally twice a day for two weeks with prednisolone at 1.5mg/kg tapered over three months. The children received 200 mg orally twice a day for two weeks with prednisolone at 1mg/kg.[58](B3)
Sometimes, the larva is seen migrating in the subretinal space. It can then be destroyed with laser photocoagulation over and around it.[59][60] The laser can be done with a neodymium-doped yttrium aluminum garnet (Nd: YAG) frequency-doubled 532 nm green laser. The laser power can be in the range of 250 to 300 mW and 100 to 150 ms duration. The reaction should produce a white burn over the retina.[61] Secondary complications like choroidal neovascularization can be treated with intravitreal anti-vascular endothelium growth factor agents.[62] (B3)
Some patients present late without active inflammation. There is a peripheral focal granuloma with a vitreal fold radiating from it to the posterior pole. There can be accompanying tractional retinal detachment and a cataract. In such cases, surgery is indicated. Lens aspiration with intraocular lens implantation is preferred for the cataract. Pars plana vitrectomy is done for vitreous opacification and membranes.[63] It also relieves the traction bands and allows retinal reattachment. Epiretinal membrane over the macula and disc can be peeled off.[64] (B3)
With such maneuvers, vision improves or remains stable in 85% of cases.[65] Sometimes a retinal tear occurs secondary to the traction from a peripheral granuloma. A scleral buckle can be placed to relieve the retinal traction and improve visual acuity.[30](B3)
The most important step in the management of toxocariasis is prevention. Good hygiene should be maintained in children.[66] They should be prohibited from coming in close contact with dogs and cats. They should not play with contaminated soil and not walk bare feet outside. Meat should be properly cooked before consuming it. The puppies and dogs should be given anthelmintic drugs.[67] Their litter should be disposed of in plastic bags. Educating the parents and child about clean and hygienic habits is essential.(B2)
Differential Diagnosis
Differential diagnosis of toxocariasis includes retinoblastoma, endophthalmitis, retinopathy of prematurity (ROP), toxoplasmosis, panuveitis, Coats disease, persistent hyperplastic primary vitreous (PHPV), familial exudative vitreoretinopathy (FEVR), combined hamartoma of the retina, and retinal pigment epithelium (CHRRPE), and seasonal hyperacute panuveitis (SHAPU).[68][69]
Retinoblastoma is the most common intraocular malignancy of childhood.[59] It is generally diagnosed before three years of life which is a younger age group than that seen in toxocariasis. It presents with solid intraocular mass with calcification on the USG B scan. The tumor appears hyperechoic with irregular borders. The calcification is highly hyperechoic with back shadowing.[70]
Coats disease is generally seen in males. It is a unilateral condition and presents with retinal exudation, aneurysmal dilatation, telangiectasia, and occasional neovascularization.[71][69] Fluorescein angiography shows localized vascular anomalies (beading, telangiectasia, aneurysm) and peripheral non-perfusion.[72]
ROP usually presents within two months of birth.[73] There is a history of prematurity and/or low birth weight. It usually presents with peripheral retinal avascularity and a definite line or ridge with or without neovascularization.[74] In advanced cases (stages 4 and 5), retinal detachment may be noted.[75] So careful ultrasound is important to rule out peripheral and posterior pole granuloma.
PHPV is a congenital condition usually diagnosed in the first month of life. It presents with leukocoria, cataract, and a fibrovascular stalk extending from the optic disc to the posterior lens surface. The involved eye is usually microphthalmic with prominent ciliary processes.[76]
FEVR is a congenital condition that presents with straightening of the retinal vessel, retinal detachment, and peripheral avascular retina.[77] It is an autosomal dominant disorder with a positive family history.[78]
Endophthalmitis presents with lid edema, conjunctival congestion, discharge, hazy cornea, and vitreous exudates.[79]
Toxoplasmosis causes a focal necrotizing retinochoroiditis which appears as a yellowish elevated lesion at the posterior pole.[80] It usually reactivates at the edge of a scar which is often pigmented. There may be accompanying vitritis which gives the headlight in fog appearance.[81]
CHRRPE is a hamartomatous malformation involving the retina, retina pigment epithelium, and vitreoretinal interface.[82][83] It appears as a grey, elevated retinal lesion over the posterior pole with retinal vessel tortuosity and epiretinal membrane. On optical coherence tomography, it appears as a hyper-reflective retinal surface with underlying shadow due to the dense tissue and an epiretinal membrane.[83] Omega sign (omega-shaped appearance of inner retinal layers, the posterior margin of which is formed by the outer plexiform layer) has been recently described for this condition.[84]
SHAPU is a unilateral childhood ocular inflammatory disease reported only from Nepal since 1975. Initially, it occurred every two years, but recent reports have described it to occur annually during the summer or autumn months. It occurs suddenly in a healthy child. The child presents with complaints of sudden onset of redness, decreased vision, white pupillary reflex, and minimal pain. On examination, circumciliary congestion, fibrinous anterior chamber reaction, hypopyon, and shallow anterior chamber are present. The eyeball is soft (malignant hypotension). "White pupillary reflex in red-eye" and minimal pain is the hallmark of the disease. The cause is unknown though some studies have linked it to exposure to moths.[85]
It is treated with injectable methylprednisolone for three days followed by oral steroids, topical antibiotics, steroids, and cycloplegic. Early core vitrectomy has shown promising results.[86] The prognosis is poor as two-thirds of patients present with blindness, and most of the rest lose vision rapidly.[87]
Prognosis
Patients presenting early in the course of the disease have a good prognosis.[88] The inflammation can be adequately controlled with oral corticosteroids and topical cycloplegic mydriatic.[58] This prevents vision loss and long-term complications.[89] Patients presenting late generally have guarded visual prognosis because of optic atrophy, macular changes, and retinal detachment.[90]
Complications
Prolonged inflammation leads to posterior synechia formation, which can cause iris bombe and angle-closure glaucoma.[29] Uncontrolled inflammation can cause ciliary body shutdown and hypotony.[91] Long-standing vitritis causes cystoid macular edema, epiretinal membrane, and macular degeneration.[66] Vitreal folds can cause tractional retinal detachment. Phthisis bulbi is the end stage of the disease.[92][40]
Deterrence and Patient Education
As ocular toxocariasis can cause permanent vision loss, preventative measures must be taken by the patients' families. The patients' family members should be adequately counseled regarding the prognosis of ocular toxocariasis and the importance of long-term follow-up.[93]
Enhancing Healthcare Team Outcomes
Any patient presenting with ocular toxocariasis should not only receive treatment by an ophthalmologist as it requires an interprofessional team evaluation by pediatricians and physicians. Interprofessional communication can lead to better patient management. The patient will most often present to the primary clinician, and these professionals should be aware of the condition as it is treatable.
Retinoblastoma is a close differential; therefore, prompt referral to an ophthalmologist is necessary. These patients can then be followed by their primary clinicians and should ensure compliance with treatment. The nursing staff will be the first to the department to come in contact with patients on follow-up. It can assess treatment progress, evaluate compliance with medication and lifestyle measures, and report any issues to the primary care clinician. This collaborative, interprofessional approach to care can ensure optimal patient outcomes.
Media
(Click Image to Enlarge)
A posterior pole toxocara granuloma with a fibrous band extending to the optic disc. Contributed by Koushik Tripathy, MD
References
Hotez PJ, Brindley PJ, Bethony JM, King CH, Pearce EJ, Jacobson J. Helminth infections: the great neglected tropical diseases. The Journal of clinical investigation. 2008 Apr:118(4):1311-21. doi: 10.1172/JCI34261. Epub [PubMed PMID: 18382743]
Level 3 (low-level) evidenceHotez PJ,Molyneux DH,Fenwick A,Kumaresan J,Sachs SE,Sachs JD,Savioli L, Control of neglected tropical diseases. The New England journal of medicine. 2007 Sep 6; [PubMed PMID: 17804846]
Glickman LT,Magnaval JF, Zoonotic roundworm infections. Infectious disease clinics of North America. 1993 Sep; [PubMed PMID: 8254168]
Level 3 (low-level) evidenceWILDER HC, Nematode endophthalmitis. Transactions - American Academy of Ophthalmology and Otolaryngology. American Academy of Ophthalmology and Otolaryngology. 1950 Nov-Dec [PubMed PMID: 14798648]
Level 3 (low-level) evidenceBEAVER PC,SNYDER CH,CARRERA GM,DENT JH,LAFFERTY JW, Chronic eosinophilia due to visceral larva migrans; report of three cases. Pediatrics. 1952 Jan; [PubMed PMID: 14911260]
Level 3 (low-level) evidenceNICHOLS RL, The etiology of visceral larva migrans. I. Diagnostic morphology of infective second-stage Toxocara larvae. The Journal of parasitology. 1956 Aug; [PubMed PMID: 13346427]
Level 3 (low-level) evidenceChieffi PP,Santos SV,Queiroz ML,Lescano SA, Human toxocariasis: contribution by Brazilian researchers. Revista do Instituto de Medicina Tropical de Sao Paulo. 2009 Oct-Dec; [PubMed PMID: 20209265]
Level 3 (low-level) evidenceSchantz PM, Of worms, dogs, and human hosts: continuing challenges for veterinarians in prevention of human disease. Journal of the American Veterinary Medical Association. 1994 Apr 1 [PubMed PMID: 8045801]
Level 3 (low-level) evidenceAlexander U,Lim CW,Kim B,Hong EJ,Kim HC,Park BK, Morphological and Molecular Characterization of Toxocara tanuki (Nematoda: Ascaridae) from Korean Raccoon Dog, Nyctereutes procyonoides koreensis. The Korean journal of parasitology. 2018 Dec; [PubMed PMID: 30630277]
Mok CH, Visceral larva migrans. A discussion based on review of the literature. Clinical pediatrics. 1968 Sep; [PubMed PMID: 4877895]
Despommier D, Toxocariasis: clinical aspects, epidemiology, medical ecology, and molecular aspects. Clinical microbiology reviews. 2003 Apr; [PubMed PMID: 12692098]
Level 3 (low-level) evidenceFarmer A, Beltran T, Choi YS. Prevalence of Toxocara species infection in the U.S.: Results from the National Health and Nutrition Examination Survey, 2011-2014. PLoS neglected tropical diseases. 2017 Jul:11(7):e0005818. doi: 10.1371/journal.pntd.0005818. Epub 2017 Jul 31 [PubMed PMID: 28759601]
Level 3 (low-level) evidenceWon KY,Kruszon-Moran D,Schantz PM,Jones JL, National seroprevalence and risk factors for Zoonotic Toxocara spp. infection. The American journal of tropical medicine and hygiene. 2008 Oct [PubMed PMID: 18840743]
Level 3 (low-level) evidenceChorazy ML,Richardson DJ, A survey of environmental contamination with ascarid ova, Wallingford, Connecticut. Vector borne and zoonotic diseases (Larchmont, N.Y.). 2005 Spring [PubMed PMID: 15815147]
Level 3 (low-level) evidenceStensvold CR,Skov J,Møller LN,Jensen PM,Kapel CM,Petersen E,Nielsen HV, Seroprevalence of human toxocariasis in Denmark. Clinical and vaccine immunology : CVI. 2009 Sep; [PubMed PMID: 19641098]
Level 3 (low-level) evidenceWinders WT,Menkin-Smith L, Toxocara Canis StatPearls. 2021 Jan; [PubMed PMID: 30860759]
Alabiad CR,Albini TA,Santos CI,Davis JL, Ocular Toxocariasis in a Seronegative Adult. Ophthalmic surgery, lasers [PubMed PMID: 20429500]
Woodhall D, Starr MC, Montgomery SP, Jones JL, Lum F, Read RW, Moorthy RS. Ocular toxocariasis: epidemiologic, anatomic, and therapeutic variations based on a survey of ophthalmic subspecialists. Ophthalmology. 2012 Jun:119(6):1211-7. doi: 10.1016/j.ophtha.2011.12.013. Epub 2012 Feb 14 [PubMed PMID: 22336630]
Level 3 (low-level) evidenceMarmor M,Glickman L,Shofer F,Faich LA,Rosenberg C,Cornblatt B,Friedman S, Toxocara canis infection of children: epidemiologic and neuropsychologic findings. American journal of public health. 1987 May; [PubMed PMID: 3565646]
Level 3 (low-level) evidenceSchantz PM,Meyer D,Glickman LT, Clinical, serologic, and epidemiologic characteristics of ocular toxocariasis. The American journal of tropical medicine and hygiene. 1979 Jan; [PubMed PMID: 434311]
Level 3 (low-level) evidenceRoddie G,Stafford P,Holland C,Wolfe A, Contamination of dog hair with eggs of Toxocara canis. Veterinary parasitology. 2008 Mar 25 [PubMed PMID: 18242861]
Level 3 (low-level) evidenceAmaral HL,Rassier GL,Pepe MS,Gallina T,Villela MM,Nobre Mde O,Scaini CJ,Berne ME, Presence of Toxocara canis eggs on the hair of dogs: a risk factor for Visceral Larva Migrans. Veterinary parasitology. 2010 Nov 24; [PubMed PMID: 20728996]
Level 3 (low-level) evidenceYoshikawa M,Nishiofuku M,Moriya K,Ouji Y,Ishizaka S,Kasahara K,Mikasa K,Hirai T,Mizuno Y,Ogawa S,Nakamura T,Maruyama H,Akao N, A familial case of visceral toxocariasis due to consumption of raw bovine liver. Parasitology international. 2008 Dec; [PubMed PMID: 18771749]
Level 3 (low-level) evidenceBorg OA,Woodruff AW, Prevalence of infective ova of Toxocara species in public places. British medical journal. 1973 Nov 24; [PubMed PMID: 4758452]
Level 3 (low-level) evidenceKaplan KJ,Goodman ZD,Ishak KG, Eosinophilic granuloma of the liver: a characteristic lesion with relationship to visceral larva migrans. The American journal of surgical pathology. 2001 Oct [PubMed PMID: 11688468]
Level 3 (low-level) evidenceMolk R, Ocular toxocariasis: a review of the literature. Annals of ophthalmology. 1983 Mar; [PubMed PMID: 6342500]
Level 3 (low-level) evidenceGlickman LT,Schantz PM, Epidemiology and pathogenesis of zoonotic toxocariasis. Epidemiologic reviews. 1981; [PubMed PMID: 7030762]
Level 3 (low-level) evidenceRaistrick ER,Hart JC, Ocular toxocariasis in adults. The British journal of ophthalmology. 1976 May; [PubMed PMID: 952806]
Badri M,Eslahi AV,Olfatifar M,Dalvand S,Houshmand E,Abdoli A,Majidiani H,Eslami A,Zibaei M,Johkool MG,Taghipour A,Hashemipour S, Keys to Unlock the Enigma of Ocular Toxocariasis: A Systematic Review and Meta-analysis. Ocular immunology and inflammation. 2021 Apr 28; [PubMed PMID: 33909531]
Level 1 (high-level) evidenceGiuliari GP,Ramirez G,Cortez RT, Surgical treatment of ocular toxocariasis: anatomic and functional results in 45 patients. European journal of ophthalmology. 2011 Jul-Aug [PubMed PMID: 21188682]
Level 3 (low-level) evidenceStewart JM,Cubillan LD,Cunningham ET Jr, Prevalence, clinical features, and causes of vision loss among patients with ocular toxocariasis. Retina (Philadelphia, Pa.). 2005 Dec [PubMed PMID: 16340531]
Level 3 (low-level) evidenceMartinez J,Ivankovich-Escoto G,Wu L, Pediatric Ocular Toxocariasis in Costa Rica: 1998-2018 Experience. Ocular immunology and inflammation. 2020 Aug 18 [PubMed PMID: 32809906]
Benitez del Castillo JM,Herreros G,Guillen JL,Fenoy S,Bañares A,Garcia J, Bilateral ocular toxocariasis demonstrated by aqueous humor enzyme-linked immunosorbent assay. American journal of ophthalmology. 1995 Apr; [PubMed PMID: 7709979]
Level 3 (low-level) evidenceWilkinson CP,Welch RB, Intraocular toxocara. American journal of ophthalmology. 1971 Apr; [PubMed PMID: 5553025]
Cella W,Ferreira E,Torigoe AM,Macchiaverni-Filho N,Balarin V, Ultrasound biomicroscopy findings in peripheral vitreoretinal toxocariasis. European journal of ophthalmology. 2004 Mar-Apr; [PubMed PMID: 15134110]
Gillespie SH,Dinning WJ,Voller A,Crowcroft NS, The spectrum of ocular toxocariasis. Eye (London, England). 1993; [PubMed PMID: 8224297]
Level 3 (low-level) evidencedo Lago A,Andrade R,Muccioli C,Belfort R Jr, Optical coherence tomography in presumed subretinal Toxocara granuloma: case report. Arquivos brasileiros de oftalmologia. 2006 May-Jun; [PubMed PMID: 16936967]
Level 3 (low-level) evidenceSchantz PM,Weis PE,Pollard ZF,White MC, Risk factors for toxocaral ocular larva migrans: a case-control study. American journal of public health. 1980 Dec; [PubMed PMID: 7435744]
Level 3 (low-level) evidenceIRVINE WC,IRVINE AR Jr, Nematode endophthalmitis: Toxocara canis: report of one case. American journal of ophthalmology. 1959 May; [PubMed PMID: 13649858]
Level 3 (low-level) evidenceTripathy K, Chawla R, Temkar S, Sagar P, Kashyap S, Pushker N, Sharma YR. Phthisis Bulbi-a Clinicopathological Perspective. Seminars in ophthalmology. 2018:33(6):788-803. doi: 10.1080/08820538.2018.1477966. Epub 2018 Jun 14 [PubMed PMID: 29902388]
Level 3 (low-level) evidenceHuang L,Sun L,Liu C,Li S,Zhang T,Luo X,Ding X, Diagnosis of Ocular Toxocariasis by Serum and Aqueous Humor IgG ELISA. Translational vision science & technology. 2021 Jul 1 [PubMed PMID: 34323951]
DENT JH,NICHOLS RL,BEAVER PC,CARRERA GM,STAGGERS RJ, Visceral larva migrans; with a case report. The American journal of pathology. 1956 Jul-Aug [PubMed PMID: 13339953]
Level 3 (low-level) evidenceHotez PJ,Wilkins PP, Toxocariasis: America's most common neglected infection of poverty and a helminthiasis of global importance? PLoS neglected tropical diseases. 2009; [PubMed PMID: 19333373]
Level 3 (low-level) evidenceWoodhall DM, Garcia AP, Shapiro CA, Wray SL, Shane AL, Mani CS, Stimpert KK, Fox LM, Montgomery SP. Assessment of U.S. Pediatrician Knowledge of Toxocariasis. The American journal of tropical medicine and hygiene. 2017 Oct:97(4):1243-1246. doi: 10.4269/ajtmh.17-0232. Epub 2017 Aug 18 [PubMed PMID: 28820703]
Morais FB,Maciel AL,Arantes TE,Muccioli C,Allemann N, [Ultrasonographic findings in ocular toxocariasis]. Arquivos brasileiros de oftalmologia. 2012 Jan-Feb [PubMed PMID: 22552417]
Level 3 (low-level) evidenceJansen RW,de Bloeme CM,Brisse HJ,Galluzzi P,Cardoen L,Göricke S,Maeder P,Cassoux N,Gauthier A,Schlueter S,Hadjistilianou T,Munier FL,Castelijns JA,van der Valk P,Moll AC,de Jong MC,de Graaf P, MR Imaging Features to Differentiate Retinoblastoma from Coats' Disease and Persistent Fetal Vasculature. Cancers. 2020 Nov 30 [PubMed PMID: 33266342]
Edwards MG,Pordell GR, Ocular toxocariasis studied by CT scanning. Radiology. 1985 Dec [PubMed PMID: 4059556]
Level 3 (low-level) evidenceSchantz PM, Toxocara larva migrans now. The American journal of tropical medicine and hygiene. 1989 Sep; [PubMed PMID: 2679161]
Level 3 (low-level) evidenceSharkey JA,McKay PS, Ocular toxocariasis in a patient with repeatedly negative ELISA titre to Toxocara canis. The British journal of ophthalmology. 1993 Apr; [PubMed PMID: 8494866]
Level 3 (low-level) evidenceEllis GS Jr,Pakalnis VA,Worley G,Green JA,Frothingham TE,Sturner RA,Walls KW, Toxocara canis infestation. Clinical and epidemiological associations with seropositivity in kindergarten children. Ophthalmology. 1986 Aug [PubMed PMID: 3763150]
Level 3 (low-level) evidenceChen J, Liu Q, Liu GH, Zheng WB, Hong SJ, Sugiyama H, Zhu XQ, Elsheikha HM. Toxocariasis: a silent threat with a progressive public health impact. Infectious diseases of poverty. 2018 Jun 13:7(1):59. doi: 10.1186/s40249-018-0437-0. Epub 2018 Jun 13 [PubMed PMID: 29895324]
Bird AC,Smith JL,Curtin VT, Nematode optic neuritis. American journal of ophthalmology. 1970 Jan; [PubMed PMID: 5411662]
Ahn SJ, Ryoo NK, Woo SJ. Ocular toxocariasis: clinical features, diagnosis, treatment, and prevention. Asia Pacific allergy. 2014 Jul:4(3):134-41. doi: 10.5415/apallergy.2014.4.3.134. Epub 2014 Jul 29 [PubMed PMID: 25097848]
Inagaki K,Kirmse B,Bradbury RS,Moorthy RS,Arguello I,McGuffey CD,Tieu B,Hobbs CV, Case Report: Ocular Toxocariasis: A Report of Three Cases from the Mississippi Delta. The American journal of tropical medicine and hygiene. 2019 May; [PubMed PMID: 30860012]
Level 3 (low-level) evidenceRubin ML,Kaufman HE,Tierney JP,Lucas HC, An intraretinal nematode (a case report). Transactions - American Academy of Ophthalmology and Otolaryngology. American Academy of Ophthalmology and Otolaryngology. 1968 Nov-Dec; [PubMed PMID: 5726673]
Level 3 (low-level) evidenceSeong S,Moon D,Lee DK,Kim HE,Oh HS,Kim SH,Kwon OW,You YS, A case of ocular toxocariasis successfully treated with albendazole and triamcinolon. The Korean journal of parasitology. 2014 Oct; [PubMed PMID: 25352704]
Level 3 (low-level) evidenceStürchler D,Schubarth P,Gualzata M,Gottstein B,Oettli A, Thiabendazole vs. albendazole in treatment of toxocariasis: a clinical trial. Annals of tropical medicine and parasitology. 1989 Oct [PubMed PMID: 2694978]
Level 3 (low-level) evidenceBarisani-Asenbauer T,Maca SM,Hauff W,Kaminski SL,Domanovits H,Theyer I,Auer H, Treatment of ocular toxocariasis with albendazole. Journal of ocular pharmacology and therapeutics : the official journal of the Association for Ocular Pharmacology and Therapeutics. 2001 Jun [PubMed PMID: 11436948]
Level 3 (low-level) evidenceShields JA, Ocular toxocariasis. A review. Survey of ophthalmology. 1984 Mar-Apr; [PubMed PMID: 6719335]
Level 3 (low-level) evidenceSudharshan S,Ganesh SK,Biswas J, Current approach in the diagnosis and management of posterior uveitis. Indian journal of ophthalmology. 2010 Jan-Feb [PubMed PMID: 20029144]
Natesh S,K H,Nair U,Nair K, Subretinal worm and repeat laser photocoagulation. Middle East African journal of ophthalmology. 2010 Apr; [PubMed PMID: 20616929]
Yoon DY,Woo SJ, Intravitreal Administration of Ranibizumab and Bevacizumab for Choroidal Neovascularization Secondary to Ocular Toxocariasis: A Case Report. Ocular immunology and inflammation. 2018; [PubMed PMID: 27775459]
Level 3 (low-level) evidenceWerner JC,Ross RD,Green WR,Watts JC, Pars plana vitrectomy and subretinal surgery for ocular toxocariasis. Archives of ophthalmology (Chicago, Ill. : 1960). 1999 Apr [PubMed PMID: 10206586]
Level 3 (low-level) evidenceMaguire AM,Green WR,Michels RG,Erozan YS, Recovery of intraocular Toxocara canis by pars plana vitrectomy. Ophthalmology. 1990 May [PubMed PMID: 2342813]
Level 3 (low-level) evidenceHagler WS,Pollard ZF,Jarrett WH,Donnelly EH, Results of surgery for ocular Toxocara canis. Ophthalmology. 1981 Oct; [PubMed PMID: 7335312]
Level 3 (low-level) evidenceMaroufi Y,Faridi A,Khademerfan M,Bahrami F,Zamini G, Seroepidemiological Study of Toxocariasis in Children Aged 6-14 Year Old in Sanandaj, Western Iran. Iranian journal of parasitology. 2020 Jul-Sep [PubMed PMID: 33082809]
Level 2 (mid-level) evidenceBurke TM,Roberson EL, Fenbendazole treatment of pregnant bitches to reduce prenatal and lactogenic infections of Toxocara canis and Ancylostoma caninum in pups. Journal of the American Veterinary Medical Association. 1983 Nov 1; [PubMed PMID: 12002591]
Level 3 (low-level) evidenceSimakurthy S, Tripathy K. Endophthalmitis. StatPearls. 2024 Jan:(): [PubMed PMID: 32644505]
Gupta A, Paulbuddhe VS, Shukla UV, Tripathy K. Exudative Retinitis (Coats Disease). StatPearls. 2024 Jan:(): [PubMed PMID: 32809517]
Aironi VD, Gandage SG. Pictorial essay: B-scan ultrasonography in ocular abnormalities. The Indian journal of radiology & imaging. 2009 Apr-Jun:19(2):109-15. doi: 10.4103/0971-3026.50827. Epub [PubMed PMID: 19881064]
Dundar SO,Verdi F,Unsal AIA, Coats disease with retinal neovascularization under subfoveal nodule: optical coherence tomography-angiography findings before and after ranibizumab treatment. Arquivos brasileiros de oftalmologia. 2021 Jul-Aug [PubMed PMID: 34008799]
Cunha-Vaz JG, The blood-retinal barriers. Documenta ophthalmologica. Advances in ophthalmology. 1976 Oct 15; [PubMed PMID: 1009819]
Level 3 (low-level) evidenceAdemola-Popoola DS,Fajolu IB,Gilbert C,Olusanya BA,Onakpoya OH,Ezisi CN,Musa KO,Chan RVP,Okeigbemen VW,Muhammad RC,Malik ANJ,Adio AO,Bodunde OT,Rafindadi AL,Oluleye TS,Tongo OO,Badmus SA,Adebara OV,Padhi TR,Ezenwa BN,Obajolowo TS,Olokoba LB,Olatunji VA,Babalola YO,Ugalahi MO,Adenekan A,Adesiyun OO,Sahoo J,Miller MT,Uhumwangho OM,Olagbenro AS,Adejuyigbe EA,Ezeaka CVC,Mokuolu O,Ogunlesi TA,Ogunfowora OB,Abdulkadir I,Abdullahi FL,Fabiyi AT,Hassan LHL,Baiyeroju AM,Opara PI,Oladigbolu K,Eneh AU,Fiebai BE,Mahmud-Ajeigbe FA,Peter EN,Abdullahi HS, Strengthening retinopathy of prematurity screening and treatment services in Nigeria: a case study of activities, challenges and outcomes 2017-2020. BMJ open ophthalmology. 2021 [PubMed PMID: 34514173]
Level 3 (low-level) evidenceMulticenter trial of cryotherapy for retinopathy of prematurity. Three-month outcome. Cryotherapy for Retinopathy of Prematurity Cooperative Group. Archives of ophthalmology (Chicago, Ill. : 1960). 1990 Feb [PubMed PMID: 2405827]
Level 2 (mid-level) evidenceEarly Treatment For Retinopathy Of Prematurity Cooperative Group., Revised indications for the treatment of retinopathy of prematurity: results of the early treatment for retinopathy of prematurity randomized trial. Archives of ophthalmology (Chicago, Ill. : 1960). 2003 Dec; [PubMed PMID: 14662586]
Level 1 (high-level) evidenceMaqsood H,Younus S,Fatima M,Saim M,Qazi S, Bilateral Persistent Hyperplastic Primary Vitreous: A Case Report and Review of the Literature. Cureus. 2021 Feb 3 [PubMed PMID: 33728125]
Level 3 (low-level) evidenceShute CL,McLoone E, Reaching a FEVR Pitch: A Case Series of Familial Exudative Vitreoretinopathy in Northern Ireland. Journal of pediatric ophthalmology and strabismus. 2021 Sep 1 [PubMed PMID: 34592872]
Level 2 (mid-level) evidenceKondo H, Complex genetics of familial exudative vitreoretinopathy and related pediatric retinal detachments. Taiwan journal of ophthalmology. 2015 Apr-Jun [PubMed PMID: 29018668]
. Results of the Endophthalmitis Vitrectomy Study. A randomized trial of immediate vitrectomy and of intravenous antibiotics for the treatment of postoperative bacterial endophthalmitis. Endophthalmitis Vitrectomy Study Group. Archives of ophthalmology (Chicago, Ill. : 1960). 1995 Dec:113(12):1479-96 [PubMed PMID: 7487614]
Level 1 (high-level) evidenceKarska-Basta I,Romanowska-Dixon B,Pojda-Wilczek D,Mackiewicz N, Ocular Toxoplasmosis Associated with Unilateral Pigmentary Retinopathy That May Mimic Retinitis Pigmentosa: Diagnostic Dilemmas. Medicina (Kaunas, Lithuania). 2021 Aug 27 [PubMed PMID: 34577815]
Dutta Majumder P,Shah A,Madhuravasal Krishnan J,Rishi E,Curi ALL, Driving in Fog without Headlight: Management of a Challenging Case of Presumed Ocular Toxoplasmosis. Ocular immunology and inflammation. 2021 Jan 2; [PubMed PMID: 31577475]
Level 3 (low-level) evidenceGupta R,Pappuru RR,Dave VP,Chhablani J, Choroidal neovascularization associated with combined hamartoma of retina and retinal pigment epithelium: Multimodal imaging. Indian journal of ophthalmology. 2018 Dec [PubMed PMID: 30451207]
Chawla R, Kumar V, Tripathy K, Kumar A, Venkatesh P, Shaikh F, Vohra R, Molla K, Verma S. Combined Hamartoma of the Retina and Retinal Pigment Epithelium: An Optical Coherence Tomography-Based Reappraisal. American journal of ophthalmology. 2017 Sep:181():88-96. doi: 10.1016/j.ajo.2017.06.020. Epub 2017 Jun 29 [PubMed PMID: 28669779]
Kumar V,Chawla R,Tripathy K, Omega Sign: A Distinct Optical Coherence Tomography Finding in Macular Combined Hamartoma of Retina and Retinal Pigment Epithelium. Ophthalmic surgery, lasers [PubMed PMID: 28195614]
Upadhyay M,Kharel Sitaula R,Shrestha B,Khanal B,Upadhyay BP,Sherchand JB,Ghimire P, Seasonal Hyperacute Panuveitis in Nepal: A Review over 40 Years of Surveillance. Ocular immunology and inflammation. 2019 [PubMed PMID: 29543556]
Upadhyay MP,Rai NC,Ogg JE,Shrestha BR, Seasonal hyperacute panuveitis of unknown etiology. Annals of ophthalmology. 1984 Jan; [PubMed PMID: 6703576]
Level 3 (low-level) evidenceShrestha E, A profile and treatment outcome of seasonal hyper-acute panuveitis. Nepalese journal of ophthalmology : a biannual peer-reviewed academic journal of the Nepal Ophthalmic Society : NEPJOPH. 2010 Jan-Jun [PubMed PMID: 21141325]
Level 2 (mid-level) evidenceWang H,Tao Y, Clinical Features and Prognostic Factors in Northern Chinese Patients with Peripheral Granuloma Type of Ocular Toxocariasis: A Retrospective Cohort Study. Ocular immunology and inflammation. 2020 Nov 13 [PubMed PMID: 33185484]
Level 2 (mid-level) evidenceWakabayashi T,Kamuro R,Hashida N,Shiraki N,Sakaguchi H,Ohguro N,Nishida K, Acute endophthalmitis and hyphema mimicking pink hypopyon associated with ocular toxocariasis: A case report. American journal of ophthalmology case reports. 2021 Sep; [PubMed PMID: 34430757]
Level 3 (low-level) evidenceChieffi PP,Zevallos Lescano SA,Rodrigues E Fonseca G,Dos Santos SV, Human Toxocariasis: 2010 to 2020 Contributions from Brazilian Researchers. Research and reports in tropical medicine. 2021 [PubMed PMID: 34040480]
Wang Q,Thau A,Levin AV,Lee D, Ocular hypotony: A comprehensive review. Survey of ophthalmology. 2019 Sep - Oct; [PubMed PMID: 31029581]
Level 3 (low-level) evidenceGómez-Marín JE,Londoño ÁL,Cabeza-Acevedo N,Torres E,Navarrete-Moncada L,Bueno O,Nati A,Nieto-Rodríguez P,Ariza-Pardo S,Isaza KJ,Chacón-Álvarez V,Romero-Delgado SA,Grijalva-Plaza S, Ocular Toxocariasis in Parasitology Consultation in Quindío, Colombia: Description of Cases and Contact Studies. Journal of tropical pediatrics. 2021 Jan 29 [PubMed PMID: 33313750]
Level 3 (low-level) evidenceAuer H,Walochnik J, Toxocariasis and the clinical spectrum. Advances in parasitology. 2020 [PubMed PMID: 32381193]
Level 3 (low-level) evidence