Download Tropical Ophthalmology. Part III.

Tropical Ophthalmology.
Part Three of Three
Dr. Steve Waller
Uniformed Services
University
of Health Sciences
Bethesda, Maryland, USA
[email protected]
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
Atypical TB
– after LASIK or transplant, steroid gtts
– incidence resurging
Leprosy
• neurotrophic cornea
• entropion
• can have uveitis in
lepromatous disease
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)
case seen in
military hospital
in San Antonio
Vesicant toxicity to cornea
Mustard gas: alkylation
– crosslinks DNA and denatures protein
– clinical effect:
World War I scene, France
• cornea edema
• ischemia
• secondary melt
or ulcer
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)
Manifestations
and life cycle
•
•
•
•
pruritis, skin tracks
fever
meningitis
larvae travel in
vessels
• mango fly stages
• 1-4 years to mature
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
Excision of
subconjunctival
loa loa worm
Tarantula keratopathy
• Uriticating hairs - dorsal abdomen
• ‘Cloud’ of hairs easily rubbed off


fine barbed
hairs in cornea,
can migrate to retina
diagnose
by history
of
exposure
and pain
without
inflammation
Zoonotic eye diseases
• Preferred host is non-human
• Paratenic (dead-end) visit by
parasite, but damage still done!
• Two examples:
– Toxocara vitreoretinopathy
– orbital myiasis
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
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
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
Myiasis
• Infestation of
tissue or cavities
by maggot
(Diptera)
• Internal: subretinal migratory tracks
• External: lids or conjunctiva
• Orbital: debilitated patient, abscess
• Treatment is excision
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
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
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
Ophthalmomyiasis externa
• Treatment:
–Occlude breathing tube with
beeswax, gum, ointment, fat,
drop of nicotine
–Excision
–Subretinal larva: argon laser
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
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
trophozoite
and cyst
clinical
appearance
radial
keratoneuritis:
infiltrate along
radial corneal
nerves

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Signs and symptoms
• pain out of proportion to findings
• paracentral ring infiltrate
• prior medical failure or diagnosis of HSV
Working Together
• International partnerships are key!
• Address the cultural gap in research
– Common understanding of disease
– Common understanding of ‘science’
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
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
Questions?
[email protected]