Tropical Ophthalmology. Part Three of Three Dr. Steve Waller

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Tropical Ophthalmology. Part Three of Three

• Dr. Steve Waller
• Uniformed Services University
• of Health Sciences
• Bethesda, Maryland, USA
• stephen.waller_at_usuhs.mil

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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

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Atypical TB

• after LASIK or transplant, steroid gtts
• incidence resurging

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Leprosy

• neurotrophic cornea
• entropion
• can have uveitis in lepromatous disease

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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)

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• case seen in
• military hospital
• in San Antonio

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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
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Loa loa the eye worm

• Filarial nematode of West and Central Africa
• mango fly (Chrysops), bites at dawn/dusk
• 20 million infected, gt30 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)

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Manifestationsand life cycle

• pruritis, skin tracks
• fever
• meningitis
• larvae travel in
• vessels
• mango fly stages
• 1-4 years to mature

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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

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Excision of subconjunctival loa loa worm
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Tarantula keratopathy

• Uriticating hairs - dorsal abdomen
• Cloud of hairs easily rubbed off

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diagnose by history of exposure and pain
without inflammation
?
?
fine barbed hairs in cornea, can migrate to
retina
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Zoonotic eye diseases

• Preferred host is non-human
• Paratenic (dead-end) visit by parasite, but
  damage still done!
• Two examples
• Toxocara vitreoretinopathy
• orbital myiasis

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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

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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

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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

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Myiasis

• Infestation of tissue or cavities by maggot
  (Diptera)

• Internal subretinal migratory tracks
• External lids or conjunctiva
• Orbital debilitated patient, abscess
• Treatment is excision

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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

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Dermatobia hominis

• Life cycle of 3-4 months
• Female attaches 15-30 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 14-24 days
• Adult does not eat, mates within one day, and
  lives only one week

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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

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Ophthalmomyiasis externa

• Treatment
• Occlude breathing tube with beeswax, gum,
  ointment, fat, drop of nicotine
• Excision
• Subretinal larva argon laser

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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

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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

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trophozoite and cyst
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clinical appearance
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Signs and symptoms
radial keratoneuritis infiltrate along radial
corneal nerves
?
?
?

• pain out of proportion to findings
• paracentral ring infiltrate
• prior medical failure or diagnosis of HSV

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Working Together

• International partnerships are key!
• Address the cultural gap in research
• Common understanding of disease
• Common understanding of science

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The good news

• Increasing access to eye surgery
• Inexpensive intraocular lenses now available
  worldwide
• Ivermectin and the UNs Onchocerciasis Control
  Program
• Improving nutrition
• Increasing opportunities for service

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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

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Questions?

• stephen.waller_at_usuh
  s.mil