otl ln / D0 {

/

D0 ^{

ITOBID IIEAIITIH ORGAIIIZATION

Oachocerclasls

Control

Prograrme

ln ^{the Volta}

^R:Lver

^Beeir

^Area

IJJ

t*

\!)

.,A ,r!:

./C

.'iN

otl

Dpldeuiologloal Evaluatlon Unlt

lechnlcal

Docrment W\P/Ff[.fi 6 .e

DR.

B.

IIffL,E:IORS

VISION SCNE]NffiJIG OF IIJ.LITEI?ATE PO}UIJATIOTS

a _C)

.-\

Ouagadougour May 1976

\)

\I

IT

eo

Dr. B. t\y1efors,

OphthaS-nologlet

Onchocerciasis ControL Programe

i.:l the Volta Blver

^{Baeln Area}

Ouagad,ougou, Upper Volta

INTHODUCTIOTI

Ihe

present study deal-s

with the introductton of the

SJdgren Hard-Test as ar

altencatlve to the

E-Test

for vislon

screerriag

of il.Lfterate

populations.

MATEIUI\IS AI{D IIEIHODS

In

^moEt

ophthalnological field

surreya

lt ls of great lnterest to test

^the

visuaL

acuity ln

ord,er

to estirate the

^amormt

of

^reduced

rislon ln a

poBuLatlon.

The most weLl-ktown and

trled teet is

certaln-\ir

the illlterate E-test

^(Snelfen),

ugett

at 5 or

6

aeters

distance

ryith

a

metric or decinal sca1e, llhis teet

^however,

qrthough

very accurate,

^rngJr be

cl.ifflcult for illiterate

poptrlatlons

to

^urderstand

(nfoorc D65i

Oanley 1971i Sarldes 1952) especial-\y

if sultural

and sooiolog:ical environmental

factors are

taken

lnto consitleration

(f.fppnann 1971i Ol-Iver, NawratslL

t971i

Sawlrlns 1964).

[be

experlence from

a

nrmber

of fte]d

sunreys

in

^{Ylest Af,rica}

^durfng

¹⁹⁷⁵

showetl

that the llliterate

E-Chart gave

a relative\y high r.mtestabilityr

1.?.

rllnabl1ity to

leane

the test

^arrt

to glve

re11abLe responsesrr (ltppnann ¹⁹⁷¹

).

^Thus

nuch

lnfomation

about

the rrisual acuity ln

some age groups was

lost. Altenrative

lLllterate teste

have been used

by

several

authors (gorg,

Sunduark 1967; trEooks 1965i Koh1er,

Stignnr

19771,

Iippuann

1971i Nordlow, Joachl-msson 1962;

hessl ^Austin

^19@;

SJUgren 1979).

1 o Untegt_a!_4l r

An

illlterate

^E-Chart (Aec:-uat scalee

distance

5

neters)

was used

for visual acuity testing

i:o

flve

rl11ages

(fvory

Coast a^nd Upper

YoJ.ta).

|Ihe

test

was

lntro-

cluced

wlth e big

netaLLlc

E-test-[Ype in front of

each case,

w'ith

explanations

afil

exercise

a'rr also

group

tralnlng

when possible

to

lmprove

the cooperatlon.

Each eye was

tested

separately

without

^gLass

comecti.on.

The l-evels of,

visua}

aculty.examined.

ln this

etudy

wer"r -tro

(e/e)i or?

(approx,

A/g)i ^or3

(approx, 6/1a)onil 0r1'

(6/60), [he teet

was always _Bezfo:med

unler

^good

drylfuht

condltj.ons and

the

presentatlon

of ^the test

^arranged

to

be as unlfozm as 1rcsslble, ^w"lth e naxi-urm

of

approrrmate\y

1O minutes spent

for

eaoh

c&s€. fhe teet ^procdure

^{was conlucted}

W

one olhth41mis nurse

or

two

tralned asslstants

r:rrder

cllrect

strperv'lsion

of the

ophthaLtoologist, who

participated,

i-n

testircg d,ifflcuLt

^ca,Ees.

Parts of thie

docrnent were pr€sentetl

at the

WHO

late:reg"ional

Meeting on the Preventlon

of Bllrdness,

Baghdad, 1976.

t?

-2-

In five other

viL1a6es ^(Ctrana and Upper

Yolta) the

^{Hand-fest lvas}

used..

^The test-ca.nls were supplietl

by

Stil1e-Wernerf Sweden,

in a

stard.ard

series

comprising

vlsual aculty levels ffia

5/5O

io 5/7,

^metrj-c scale ^a'ral

test

ctistance 5 meterg.

The

test

was presented

in front of

each

patient with the

5/5O

teet-type ard after

explanatlons and

tralnlng, ^the test

was perforsned as w'ith

the

E-Test

with

corres- pording

vlsual aculty levels

exarnined.

qpl test

cond.itions.

In order to

^obtai:a

identical test conditlons for the E-

ard

lland-[est a

set

of

separate

E-{a,rtls,

equal f,6 flqsimel

ii-Chart

⁽⁵

neters)

were

u6ed.

lllre cantrs had

a single test-type ln different sizes

and

the

paper streets were

ld.entical

i.:a size and

quality to the llanil4ards.

Visua1

acuity teeting

was conducted

ln four

vilLa6ee

(enana antl Upper

Volta)

w'ith these E-Cards, using

the

sane ^mqrmer

of

presentation,

tralning, test

clistance

arrl other conditions

as

for the

Hand-test.

Flnally, a sinple

screerdr:g proced.ure was deslgned

to cletect

cases

of visual

impai-rment. llhe lland.-Test was used

at

5 meters

tllstance with

presentatlon

of

the

test

as mentioned above,

but

w:ith

testing of only binocular rrision at the

leveL

of

Or5

(e/rc

and,

5/15),

0n1y cases

that failed to

^pass

this

threstrold were then tested more

in deta1l. Thls test

^procedure was conductetl

in

²⁰

villages in

^{Northern Ghana.}

2. Correlation

between

the E-[est

and

the

Harrt-0est

As

the

^Hamd-Test has

a less well-defined test-type

than

the

geometrleal

E,

a

comparison

of ^the

^two

tests

was necessarSr

to co:relate the

Hand-fest

for the

actua].

levels of visr-nl aculty

exqmined..

In flve villages

^(Cfrana and Upper

Volta)

both

tests

were performed

with

the

saroe

trntient with itlentical

presentation

of the tests, trainlngl test dlstance

^a,nc1

risuaL aculty IeveIs

examined. Only

the

D-Test-Cards were used as

E-[est,

As the

onler of the tests

^may be

of

i-mport&rrcel

the E-[est

was used as

the first test,

^ar:d

Yice

verear irr

an appro{i-mpte}y equal number

of cases. Ihe

requlrenents

for

^a

certaj.:o

level of vlsual aculty

were

in

accortlance

rylth: 4

oonsecutlve

co:rect posi- ti-ons, or 5 co:rect out of 5

shoninge,

or 6 correct out of B

strowlngs

(Borg,

Surrd.mark

1967i ltlordLow 1962).

RESULT'S

The populatlons examiraetl

with the different

methodologtes

of rieuaL

^aouity

testing are

shovcn

in table

¹

.

^These populations _resemble

a stardant

poprrlation,

calculated fron this reglon

(ltortnenc. Ghana a^nd

Ivory

Coastl l.XaJ.i and Upper Vo1ta).

The age-groups correspond

to

those

of

epideruiological srurreyo

of the

Onchocercj-asis

Control

Progranme

ln ^the

^VoLta

River

Basin Area.

r+

_Ad.drees

r

Bondegat.Zl

10251 S'fOCIfrOtM . Swed.en

The

r'mtestablIlty rates

obtainetl

with the different

methotls

of visual aculty testr'n8 are

^ghown

ln

tabLe

2. rhere

i,q a

higtrty slgnlflcarrt dd;";;";;-fu.o;;i"

between

the totar results

obtained

with the ilriterate

E-.cbart versus

E-[est-cardsl

and

also

between both

versions of

E-Test

against the Harid-fest. fhe

d.lfference

is

most than prominent 11

f0 /€&?so fhe the

^two 5-9

versions

yealps age-group

of ttaa-rest but also

show no evident

significarrt differenee ln feuales

aged uoreconcerF

ning untestability.

lable 1.

Poprrlation _examined

,

^by age-groups and sex

575

565

1 o9a

Table

2. Untestability

_rates

(It

₎

Age-Group

E-[est

Chart

M rl

E-Test

Canls Hand-Test Hand-Test

binocular

soreenLng

M F ^&[ F

22r5 o19

oro

'

_0r7

1t1

72t5

1r1 1t1

3i

2r'l

M F

5 -9

10-14 15-29 70-49

5o+

I 69,1 7rB or0 2t2

715

8512

16 15 711

17 tO 2019

50r,

215

oro

116 116

4411

4t3

4i

11r5 2016

21rD

1t5 or8 org

1r1

21 2

1

3 4 , , , , ,

1

9 7 5 3

Totalx

1417

21rB

17fl

^y'o

1or

1

¹⁷ _r7

1112 _%

4t5

⁶¹¹

5rl

^%

416

5r2 4r7 %

iland-[est

Age-Group Hand-test

blnocuLar sereening

I,I F

5-9

10

-

¹⁴

15-29 7o-49

5O+

84 102

BO

11a 5B

88 85 11V 17a 47

111

115 110 144 B9

96 88 176 151 71

579 599 621 655 758

525

449 827 727 746

M F }I F M F

1 127

1 6 1

1

09 20

?2 50 77 25

63

E-Test

Chart E-Test

Cards

91

Bota-l

929

462

⁴⁶⁷

569

594

1

167

2772

2e70

5

⁶⁴²

x)

_{Rates adjusted}

for

a6e and sex

t

I t

t tl

I tI I t

I I

I

I I I 1

rI

I I

a

I

-4-

Itre results of the

comparison

of the E-fest (single test-typeu) d the

^Hanit- Test

are

shown

in table

1a ^and.

7b.

^A prelj-rnlnary

test of the E-

arid I'IaaC-test scales was done

in a p1lot vlllage

^(taUte

5a). ^lach

^eye

is correlated

separately amd the

orig:lnaI levels of the

llard-Test

are

used, as defined

by

SJUgren

(tSlS).

Thor.rg[ the

colrelation

1s

relative\y

^good

there is

an obvlous and systematio tendency

for

the Ha.nd-test

to

^be

easier

than

the

correspording

E-[est

1evels.

[he

llanct-Test scale was then modified so

that the

nearest ma]-l-er

test-type in the

avail-ab1e star',la^rrl

serles

was used

for the various levels of

lri.sual

aculty.

This

cotresporv{s

to

^one metrj-c

step, or a factor of 0r5 -

^OrB

to the

varj-ous

test- types.

rTae

5/5 test-type

was

thus

slrnnged

to _5/4i

5/715

to->/Si Z/t5 to

D/10 arfi,

fir:ally

5/rO

to 5fiot

^and

this

new scale was

then

co:reIated.

to the

same E-scale as

before.

The

result is

^shown

ln _{table Jb,}

which

also

shows

the total

nrmber

of

^eyes

exami.ned, as no ctifference was for,ral d.ependlng on

the

ord.er

of ^the tests. It

^was

howevel

not

poesible

to double-test

every case a^nd then

only rrisual aoulty other

than l rO (S/+ SJUgren) was

verlfied with the other test in

two

vi[ages.

Ttrig erplalns

the hlgh proportlon of rrisual

impainnent

in the table

and was necessary 1n

order to obtaln a sufficient

^nr.mber

of

cases

in

each category.

Tbe

comelation

1n

table

5b

is very

^good

but with a slight

^tenlency

for

the 5/,4

test-type to

be more

easily

seen than

tne

_{t rO}

E-Ievel.

T[e Hand-Card designed,

5/7

was

also

used.,

but

gave

a very

obvious tendency

of

being uore

tllfflcu-Lt to

see

than

the

¹

_r0 E-Ievel,

and was

therefore rejected.

DISCT'SSIO1,{

[estlng of the

vtsua].

aoulty le a

complex

situation

where

not on\r test-types or

angles

of vision

detezuine

the result, but also prychological factors play

an i-mportant

role ^(Borg,

sr.rntmark 1967i

nro6rc $65i

^lip-pmann

^79e2,

¹⁹⁷¹ⁱ fvordfow ^1962).

lhe E-'Iest

has been much i-n use end

the untestabl].lty is ^general\r

consi-dered

to

^be

Iow from

the

age

of 44 ^years,

though important

variations are

seen (liptrmaffr 1971i Nordlow, Joachi-msson 1962;

Oliver,

Nawratskl ¹⁹⁷¹

i

^Sew:Ltz

^et aI.

^1964).

llre untestabillty rates

four:d

in this

study

with the

E-Test

are relatively hi&r especially

when usi-ng

a visual chart. fhere are very

few eomparabLe reports

fron field

sunreysr

but

some

results

from

the

Cemereons

indlcate

about _{5 11}

totat tmtestability with the illiterate

E-Chart (Atderson,

fhglsang 1974). This

^mA)r how-

ever be

a

question

of different test

procedure

or

population examlned..

ltre

pattenn

of untestablllW

1n

the

age-groups and

relatecl to

sex 1s

the

sa$e

ln thls

str.lrly

for alL

verstons

of tests arrl is elso

confirmed. fnon previous

fieLd

surveys (anAer-son,

I\iglsang

1974i canJ-ey

197r).

The naJor

part of

r.&testabLe cases

is

found

in chil-

dren Less

tban

10

years olil,

and

also in

nomen,

especlally

i-n

the

oLder age-gloups.

The funportance

of

sho!1ing

single test-types to

^improve

the

cooperation has been -9mnha9fer1.!1 ^pone

authors (ffoofs

1965i

KohILr,

Stigmar 1969; Llppna:en 1g71r O1iver, Nawratski 1971) anct

thls is also the

experience j.n

thls rtudy.

^The trisua,l

chart

has-

the

disadv.anta6e

of

belng

dlffictrlt to

undersf,nnd,

but also

w:tth

very

few

test-types

for the 6/60 Level. It

^caJx

not

be considered

as sufflclent to

^diagnose

a

rrlsual I-npafu:nent

upol

on-\y

2-5

tested.

positlons

orur

fjnger-cor:ntlng in

these cases means

less

accuracy

(Canfq 877). Patients without v:isual

impairilent rnay uansge

with

the

first line

by chartce, and then

not

be

able to

eooperate

iurther. fhis

means

a rlsk of nisintertrrretlng

cases

of r:ntestabllity

as

a

rrisu,al lmpairment.

-

1l:

^d1arrtaqe

^of

^Br'oup

^trainlng

^{has been}

snderllnea

^{(eanrey 1977} alrd, 1g75j Iaruttgen,

pers.

_colm,.

)

^axtd

this

undoubtedly nay tnp:rove

the

cooperation

but on\y to a

f.im{ted

ertentr as maII

ohiLdren a.rd slqr women are

difficuJ.t to involve in the trainlng.

9**p ^txalning

_"1se ^JmPlles

^a

^need

for a very

good

ard acttve Local interpreter/

leader ln the

vi1_Iage.

the llfLuence of

crrlturaL

deprlvation, lsolation

anrt

a

1.ow

social

Level has been potnted

out in

some papers (lippmann 1971i

Ollver,

IlarryratsH.

19I1i Sarkies l95li

Sawitz 1954) ard. these

factors,ay b; of great

lmportnnce

but are dlfflcrflt to

^eya-

luate ln afrlcan populatlons.

_However,

it

stroufa be erophasizecl

that the

vlLtages

e:camlned

ln thls sttdy are situatetl in

renote areas end

with a very low

soclo-"corro-

nic Ieve}.

Ihe

Har:d-[est has

given

]-ower

rrntestabillty rates ln th1s

etuily than

the

E-Test

a^nd

this

conftums

the

ldeas

of

some authors

(rrotrc

l.965i

oliver;

Nawratskl 1971) thougfu

it

has neYer been

testetl in the fieltt. [he

Hand-iest seens

to

^be

easler to

understarrcl

strildngly

and

in favour the

d.ifference

of thi-s test. ln

^shown However,

tnterest

both and

the

cooperatlon

E-

and

the of

Har:d-Test

the

populatlon have the

is

disadvanta€e

that

a developed

spati.al onieniatlon j.s

necessarlr

(aorg, s*rarr.t

¹⁹⁶⁷ j Ffooks 1965i

lippann

1971).

.

^.T1r" SjUgren Hand-fest was lxtroduced Ln 1g5g

ln

a modified

version

where the

prlnclple of

Snellen has been

used. [he size of the fingers ard their

lrrtenrentng angles

are

calorrlated so

that the

ar:gle

of vislon is

one

olnute

wtren

the canl

1s seen

at a

certaj.:e di-stance, narked on

the

backslcle (Sl6gren

1g7g).

However, ,roi

on\y the fingers but

al-so

the

shape 1n general

are lnportant for thls test-type

as

the oval

aBpearance naJr

facllitate to locate the ctirection of the iitg;;; (#8,

Srrndnark 1967).

-

^{. m93}

^{u!r.!8 the orlginal metrlc scale} of

SjUgren,

it

does

not dlrectJy

corres- pond step

to gives a the

E-Test Yery good

levels cornelation

exa,ulned..

to fhe the E-Test, reduction but of-the test-type slze this

has been

tested

one

for

metriconlgr

four levers of rrisual aculfir. It

should be

strong\r

emihasized,

that the copelation

found

in this stu{y is emplrlcal, as

complicatlng

factors are

involved. e.g.

fls6imq1 aJal

metric scales.

However,

for

screening purposes

of il].lterate

populations

the

Harrd-Test has lrnportarrt advarrtages

ard

shows

a

comelati.on

that

1s

suffi-cient to pe:mit

categorJ.zing

of vislon leveIs with a

^good, accuracy.

SI]T,IMANY

lwo

verslons of ^the llliterate E-Iest

have been used.

together

w:lth tJre Sjdgren Hanl-Test populations

for In lfest

vlsr.pL Af:rica.

acuity teetlng in

op&rthaLuol-ogical

field

sunreys

of illlterate

lhe illlterate E-chart

noqlr

glve a high proportion of lmtestabllity

because

of d'ifficultj-es to

r.urlersta$d

the test. rhis

^problen can be

signlflcant]y

reduced by Ssing

a single E-lest-$rpr.

on separate

cartds. _Ihe

Hand-Tesf has

glven slgnlfloarrtly less untestabllity

_{than both versi-ons}

of the E-test in thls

studJr.

It is

posstble

to co:relate the

ilard-Test

direct\y to the

E-Test

results for

certa:in

levels of visual aculty ard

using

a slightly ,&itrea metrlc

sca1e.

the

E-Test

is still better defined

and.

preferable to

^use

for

a detailed.

risual

acuity testlng of a limited

nr.mber

of

cases,

iut for vislon

screening

of i-Lllterate

popurations i.n

field

surreys

the

Hand-Test

is a better

arternati.ne.

-6-

Iab1e

5.

Comelation E-Test _{versus Hand-I}

est for

for.u leve1s

of visual

aerri Table

5a:

^Oulginal

metrie _scale of

Hand_Test (SSUgren)

(each eye exami^ned comelated separately) E-Test

Heud-Test

HanI-[est

or7 or7

0rl

726 )t 0 o 357

1 4 11 o 16

o 1 2 1 6

o o 4 4

127 36 17 7 783

Tabl-e

3b:

^Modified

metric

scale

of

Hanrt_Test

(each eye exqmj-ned, correlated, separate\y)

E-[est

(r ₌

or84)

1rO or7

B

orl

0r1

,/4

716 o 0 724

5/5 4

o

B1 o

o 117

o B5

5/10 _{o 117}

5/zo o o o 36 76

720 ^B9 117

,6

962

(3 =

⁰¹⁹⁹⁾

5/so ^I

II I

o

I I I I I

Anderoon,

J et 41. (lSl+)

str-rOies on onchocerciasis

ln the

Untted Ca:ueroon

Republic.

Comparison

of

popul-atlons

with

ar:d

without

0nchocerca volrmlus

[raas.

Roy. Soc.

frop.

^Ivied. Hvs_,at

@, 7,

^19o-2o8

2.

3.

4.

12.

13.

Borg,

chlld.ren, G.

&

sundrnalk, Acta

E:trthal., E.

^(tS0Z)

E, A

conparative str:dy ^1OD-117

of

visuaL acn:ltJr

tests for

trfooks,

0. (ts0l) vislon test for child,ren, Brit. J.

^ophthral

,1

491 112 Garrley,

J.?.

(Docr-ment

llSl1)

I{6thode de mesure de

I' t6 ^visuelle Ie te:rai:r

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5,

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the

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al

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1'