Upload
alexandra-bradford
View
222
Download
1
Embed Size (px)
Citation preview
Tropical
Ophthalmology. Part One of Three
Dr. Steve WallerUniformed Services
University
of Health Sciences
Bethesda, Maryland, USA
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
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
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
Global Distribution of Blindness by Cause
Cataract42 %
Trachoma15 %
Glaucoma14%
Onchocerciasis1 %
Other28 %
Macular degenerationDiabetic retinopathy
State of Global Blindness
Present estimate:
– 45 million people blind
+
– 135 million visually disabled
LowVision
BlindBlind< 6/18 - 3/60 < 3/60 (or 20/400)
International classification ignores the burden of uncorrected refractive errorInternational classification ignores the burden of uncorrected refractive error
80% of blindnessis preventableor curable
Prevalence of Blindness
90%+ live in90%+ live inlower incomelower income
countriescountries
Relationship between blindness and socio-economic status
Blindness Poverty
However - the link between prosperityand health is not automatic -
National cataract surgical ratesand corresponding GDP
0
5,000
10,000
15,000
20,000
25,000
30,000
0 1,000 2,000 3,000 4,000 5,000 6,000
Cataract operations per million population per year
Real GDPper capita
($)
outliersprove thecase!
Cataract – ‘the #1 cause’
efficient, accessible surgery = a huge impact on blindness
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
Toxoplasma gondii
• Intracellular protozoan• Global distribution• Transmission:
– Direct ingestion of oocyst• Uncooked meat• Mucosal inoculation
– Transplacental• Cats are definitive host,
but infects all mammals
Ocular Manifestations
• Prominent vitritis
“headlight in the fog”
• Necrotizing
retinochoroiditis
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; don’t shake litter box• Freezing temperatures are not adequate – cysts
survive in sand up to one year
Synergistic Diseases• Sum is greater than
individual parts• Etiology often cultural
and economic• Three examples:
– Vitamin A + measles– trachoma + bacteria– HIV + many diseases
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
WHO classification
• XN – night blindness (easy to screen)• X1A – conjunctival xerosis• X1B – Bitot’s spot• X2 – corneal xerosis• X3A – keratomalacia and small ulcer• X3B – large ulcer• XS – corneal scar• XF – xerophthalmic fundus
Bitot spot: early sign, foamy appearance to conjunctiva
progressionof untreated disease toblindness
Vitamin A and measles
Vitamin A deficiencygreatly enhances measles virulence andlethality
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
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 AsiaInfectious (WHO ‘TF’ stage)
Clinical diagnosis of trachoma
at least two of the following:– lymphoid follicles on upper tarsal
conjunctiva–typical conjunctival scarring (Arlt’s line) – limbal follicles or
Herbert’s pits –vascular pannus
Conjunctivalscarring
(Arlt’s line )
chronic irritationsetup for blinding bacterial keratitis
Chronic epithelial defect from misdirected lashes
Secondary bacterial infection
HIV eye disease
• Most blinding opportunistic infections are chorio-retinal– cytomegalovirus (beta Herpes 5) -
most common– toxoplasmosis, others
• Kaposi’s sarcoma of conjunctiva• Corneal microsporidiosis (no photo)
Cotton-wool spots
CMV retinitis
Kaposi’s sarcoma
inner canthus tumor
Kaposi’ssarcoma of nose
see lecture parts two andthree for more TropicalOphthalmology