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Tropical Ophthalmology. Part Three of Three Dr. Steve Waller Uniformed Services University of Health Sciences Bethesda, Maryland, USA

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Presentation on theme: "Tropical Ophthalmology. Part Three of Three Dr. Steve Waller Uniformed Services University of Health Sciences Bethesda, Maryland, USA"— Presentation transcript:

1 Tropical Ophthalmology. Part Three of Three Dr. Steve Waller Uniformed Services University of Health Sciences Bethesda, Maryland, USA

2 Unusual tropical eye diseases Not commonly found in U.S., even in teaching hospitals Five examples: – atypical tuberculosis (TB) – leprosy – manzanillo keratopathy – loa loa conjunctivitis – tarantula keratopathy

3 Atypical TB – after LASIK or transplant, steroid gtts – incidence resurging

4 Leprosy neurotrophic cornea entropion can have uveitis in lepromatous disease

5 Manzanillo tree sap keratopathy Manzanillo or “beach apple” tree –common to Caribbean, east coast of Florida Sap is milky latex vesicant known for delayed dermal effects; folk medicine for conjunctivitis Acute ocular effects first described in US troops during WWII Other natural blistering agents: – cantharidine (beetle) – no known antidote – poison ivy/oak – podophyllum (mandrake root)

6 case seen in military hospital in San Antonio

7 Vesicant toxicity to cornea Mustard gas: alkylation – crosslinks DNA and denatures protein – clinical effect: cornea edema ischemia secondary melt or ulcer World War I scene, France

8 Loa loa: the “eye worm” Filarial nematode of West and Central Africa mango fly (Chrysops), bites at dawn/dusk 20 million infected, >30% in hyperendemic areas adult worms live for 20 years, up to 60 mm long subcutaneous or subconjunctival migration “Calabar swelling” from allergic angioedema (named for eastern Nigeria seaport)

9 Manifestations and life cycle pruritis, skin tracks fever meningitis larvae travel in vessels mango fly stages 1-4 years to mature

10 Prevention, Diagnosis, Treatment Prevention: avoid vector contact, apply insecticide to mango groves Diagnosis: clinical or find microfilariae on Wright or Giemsa stains of daytime blood Treatment: surgery, ivermectin*, albendazole*, mebendazole* * off label use

11 Excision of subconjunctival loa loa worm

12 Tarantula keratopathy Uriticating hairs - dorsal abdomen ‘Cloud’ of hairs easily rubbed off

13 diagnose by history of exposure and pain without inflammation fine barbed hairs in cornea, can migrate to retina  

14 Zoonotic eye diseases Preferred host is non-human Paratenic (dead-end) visit by parasite, but damage still done! Two examples: – Toxocara vitreoretinopathy – orbital myiasis

15 Ocular larva migrans (Toxocara canis or cati) Worldwide distribution Risk factor: exposure to canine/feline feces sandbox is infective up to one year after feces deposited

16 Toxocara life cycle adults in canine intestine fecal contact by human eggs hatch in GI tract migrate in blood vessels exits at end organ –brain, eye –liver –lungs

17 Manifestations Visceral larva migrans Ocular larva migrans –Uveitis, hypopyon –Macular / peripheral granuloma –Vascular occlusive disease Treatment –Steroids, laser if larva alive –Value of antihelminthics unclear

18 Myiasis Infestation of tissue or cavities by maggot (Diptera) Internal: subretinal migratory tracks External: lids or conjunctiva Orbital: debilitated patient, abscess Treatment is excision


20 Dermatobia hominis AKA human botfly, torsalo (Central America), ‘beef worm’ (Belize), ‘mosquito worm’ Habitat: forests and river valleys in Latin America, imported to USA case in Dallas County, TX, 2003 Hosts: man, cattle, dogs, birds

21 Dermatobia hominis Life cycle of 3-4 months Female attaches eggs to a fly, mosquito, or (rarely) tick, who then transmit to egg to human host 1mm ‘bot’ hatch, enter host at bite grows over 6-12 weeks to 20 mm Mature larvae exit furuncle opening, drops to ground, pupates for days Adult does not eat, mates within one day, and lives only one week

22 Larva Furuncular myiasis: movement often observed within opening Two oral hooks at distal end, two dark respiratory ‘spiracles’ near skin break Adult fly: ½”, yellow, resembles a bee

23 Ophthalmomyiasis externa Treatment: –Occlude breathing tube with beeswax, gum, ointment, fat, drop of nicotine –Excision –Subretinal larva: argon laser

24 Iatrogenic Diseases Rabies in corneal transplant – Most recent case - Iran, 1996 – 8 reported cases (one US case in 1979) – implications for regulation and eye banking in developed and developing world

25 Acanthamoeba Keratitis Ubiquitous, warm water Homemade contact lens solutions and hot tubs Chronic pain and ulcer Medications (all off label use): Brolene (0.1% propamidine), PHBG 0.02%, neomycin, miconazole, others

26 trophozoite and cyst

27 clinical appearance

28 Signs and symptoms pain out of proportion to findings paracentral ring infiltrate prior medical failure or diagnosis of HSV radial keratoneuritis: infiltrate along radial corneal nerves   

29 Working Together International partnerships are key! Address the cultural gap in research –Common understanding of disease –Common understanding of ‘science’

30 The good news Increasing access to eye surgery Inexpensive intraocular lenses now available worldwide Ivermectin and the UN’s Onchocerciasis Control Program Improving nutrition Increasing opportunities for service

31 Summary Epidemiology: still much needless suffering around the world Synergy: culture and disease Environment: protection is affordable Exotics: rare but important Iatrogenics: preventable The future is bright

32 Questions?

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