Tropical Ophthalmology. Part One of Three

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Tropical Ophthalmology. Part One of Three

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

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Author

• ophthalmologist and global health faculty at
  Uniformed Services University of the Health
  Sciences, a US government school
• US Air Force officer for over 30 years
• taught and performed eye surgery in 16 countries
• dedicated to reducing preventable blindness
  throughout the world

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Overview ofthree lectures

• Tropical Ophthalmology in
• three parts topically divided
• Epidemiology of blindness cataract
  (toxoplasmosis)
• Synergy of diseases vitamin A measles,
  trachoma bacterial keratitis, HIV many
  diseases
• Disease Control EKC, oncho
• Environmental fungal keratitis, pterygium
• Exotics atypical TB, leprosy, beach apple, loa
  loa, tarantula
• Zoonotics toxocara, myiasis
• Iatrogenic rabies, acanthamoeba
• Working together for a better world

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Epidemiology of Blindness

• Blindness is a tropical disease!
• Poor vision is 3 cause of disability worldwide
• Approximately 75 of global blindness is curable
  or preventable (US National Eye Institute, Nov
  2006)
• Top worldwide cause is cataract
• India, China, Africa
• Solution is efficient, accessible surgery
• Uncorrected refractive error big issue

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Global Distribution of Blindness by Cause
Macular degeneration
Other 28
Diabetic retinopathy
Onchocerciasis 1
Glaucoma 14
Cataract 42
Trachoma 15
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State of Global Blindness
80 of blindness is preventable or curable

• Present estimate
• 45 million people blind
• 135 million visually disabled

International classification ignores the burden
of uncorrected refractive error
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Prevalence of Blindness
90 live in lower income countries
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Relationship between blindness and
socio-economic status
Blindness
Poverty
However - the link between prosperity and health
is not automatic -
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National cataract surgical ratesand
corresponding GDP
Real GDP per capita ()
outliers prove the case!
?
?
Cataract operations per million population per
year
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Cataract the 1 cause
efficient, accessible surgery a huge impact
on blindness
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Toxoplasmosis

• Chrorioretinal scars hidden by cataract
• Very common in developing world
• Significant cause of strabismus (evil eye)
• 1 cause (20) of
• reduced vision after
• successful cataract
• surgery in Central
• American country in
• our study, 2004

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Toxoplasma gondii

• Intracellular protozoan
• Global distribution
• Transmission
• Direct ingestion of oocyst
• Uncooked meat
• Mucosal inoculation
• Transplacental
• Cats are definitive host,
• but infects all mammals

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Ocular Manifestations

• Prominent vitritis
• headlight in the fog
• Necrotizing
• retinochoroiditis

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Toxoplasmosis

• Clinical diagnosis with help from ELISA, Western
  blot, PCR
• Negative serology argues against infection, but
  positive serology does not prove disease
• Tx sulfadiazine, pyrimethamine, Septra (off
  label), cryotherapy
• Cover sandbox dont shake litter box
• Freezing temperatures are not adequate cysts
  survive in sand up to one year

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Synergistic Diseases

• Sum is greater than
• individual parts
• Etiology often cultural
• and economic
• Three examples
• Vitamin A measles
• trachoma bacteria
• HIV many diseases

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Vitamin A deficiency

• a leading cause of preventable childhood
  blindness
• associated with other deficiencies
• first symptom - night blindness
• scaly skin, dry eye, prone to ulcer
• prompt response to 200,000 unit pill x 3

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WHO classification

• XN night blindness (easy to screen)
• X1A conjunctival xerosis
• X1B Bitots spot
• X2 corneal xerosis
• X3A keratomalacia and small ulcer
• X3B large ulcer
• XS corneal scar
• XF xerophthalmic fundus

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Bitot spot early sign, foamy appearance to
conjunctiva
progression of untreated disease to blindness
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Vitamin A and measles
Vitamin A deficiency greatly enhances measles
virulence and lethality
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Trachoma

• Chlamydia trachomatis, eye disease same strains
  as genital disease
• Multiple infections, poor hygiene
• Direct contact, children worst
• Passed on hands and by flies
• Upper lid scarring, lashes in-turned
• Soap/water, TCN or erythro ung
• Zithromycin helpful, temporarily

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Trachoma epidemiology

• 500 million people infected
• Most common preventable blindness
• 2 million blind in endemic areas
• North and sub-Sahara Africa
• Middle East
• North India
• Southeast Asia

Infectious (WHO TF stage)
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Clinical diagnosis of trachoma

• at least two of the following
• lymphoid follicles on upper tarsal conjunctiva
• typical conjunctival scarring (Arlts line)
• limbal follicles or
  Herberts pits
• vascular pannus

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Conjunctivalscarring(Arlts line )
?
?
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chronic irritationsetup for blinding bacterial
keratitis
Chronic epithelial defect from misdirected
lashes
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Secondary bacterial infection
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HIV eye disease

• Most blinding opportunistic infections are
  chorio-retinal
• cytomegalovirus (beta Herpes 5) - most common
• toxoplasmosis, others
• Kaposis sarcoma of conjunctiva
• Corneal microsporidiosis (no photo)

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Cotton-wool spots
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CMV retinitis
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Kaposis sarcoma
inner canthus tumor
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Kaposis sarcoma of nose
see lecture parts two and three for more
Tropical Ophthalmology