Tropical

Ophthalmology. Part One of Three

Dr. Steve WallerUniformed Services

University

of Health Sciences

Bethesda, Maryland, USA

stephen.waller@usuhs.mil

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