6^th^ Meeting of the Washington Group on Disability Statistics

Kampala, Uganda

October 10-13, 2006

**[Summary of pre-test results for WG short set of questions:
VISION]{.underline}**

**Introductory phrase:**

The next questions ask about difficulties you may have doing certain
activities because of a HEALTH PROBLEM.

**[Question on vision]{.underline}**

Do you have difficulty seeing, even if wearing glasses?

a.  No - no difficulty

b.  Yes -- some difficulty

c.  Yes -- a lot of difficulty

d.  Cannot do at all

[Summary of pre-test results]{.underline}:

In the cognitive tests, 191 of the cases (out of 1014) fell into the
"problematic" group of response patterns for the vision questions.
Responses were more consistent when the difficulty and effort
questions[^1] were taken into account; only 117 out of 1014 remained in
the "problematic" group of response patterns after considering responses
to these additional questions. For example, there were instances where
respondents answered the WG question affirmatively, but answered "no" to
the near/far vision questions. This was considered a problematic
response pattern because responses did not agree. However, if
respondents expressed that it was difficult or required effort to see
well on the difficulty/effort questions, then the difference in
responses to the WG question and the near/far vision questions was no
longer considered problematic since it appeared that the WG question was
detecting a different aspect of vision than the more detailed near/far
vision questions. Thus, it was suggested that the near and far vision
questions[^2] may not be capturing all the relevant cases. In addition,
difficulties with understanding the glasses clause and it's location
within the question appeared to explain only part of the discrepancies
between the WG question and the near/far vision questions. Seven
countries had response patterns suggesting that respondents were missing
or misinterpreting the glasses clause (Argentina, Brazil, Egypt, Kenya,
Mexico, Paraguay and Vietnam). However, the clause was understood by
respondents in 4 countries (Argentina, Brazil, Mexico and Paraguay).
There were very few cases where respondents replied "no difficulty" to
the WG question but reported "a lot of difficulty"/ "a lot of effort"/
"\[difficulties\] very often" to the extended vision questions^1,2,^[^3]
(n=5 of 1014). There were only 15 instances where respondents reported
"a lot of difficulty" or "unable" to the WG question but "no difficulty"
/ "no effort"/ "\[difficulties\] never" to the extended vision
questions. It was suggested that the near and far vision questions may
be missing aspects of visual problems (such as cataracts, problems with
one eye only) that are being reported using the WG question.

Vietnam expressed concern about the discrepancy in responses of "unable"
on the WG question compared to the near/far vision questions. Their
field test data indicated that while 3.3% (of 3409 persons) reported
"unable" to the near/far vision questions, only 0.7% reported "unable"
to the WG question. Subsequent discussion suggested that this supported
the premise that the near and far vision questions detect specific
aspects of visual problems whereas the WG question was more
comprehensive (it appeared that respondents that were unable to see
near/far reported only some difficulty seeing on the WG question because
they were not unable to see at all...that is, a person unable to see
closely may be able to see in the distance; this requires further
analysis). WHO/ESCAP analyses indicated moderate correlation between the
WG question and the extended questions and low sensitivity of the WG
question compared to the extended questions. However, three issues
confound the comparison of responses: the extended questions refer to a
health problem lasting 30 days while the WG question has no reference to
duration; the WG question asks about the quantity of the problem while
the extended questions ask about severity; and finally, the extended
questions have a 5 points response scale versus a 4 point scale for the
WG questions. It was noted that the results of sensitivity and
specificity analyses need to be interpreted with caution since there is
no gold standard and to reset the cut point and re-analyze the data from
the WHO/ESCAP test.

Overall, the WG question on vision was interpreted consistently across
countries. Consideration will be given as to how to best address the
glasses clause. It was suggested that better concept translation is
needed rather than direct language translation since "even if" is not
easily interpretable in some languages.

[^1]: Difficulty and effort questions: *Without/ With your glasses,* (i)
    *how often do you have difficulty seeing well?* (ii) how much effort
    do you have to put into seeing*?*

[^2]: Near and far vision questions: *Without/ With your glasses, do you
    have difficulty,* (i) *seeing the print in a map, newspaper or
    book?* (ii) *seeing/recognizing a person you know from 7 meters
    away?*

[^3]: Additional extended question: *Do you wear glasses all of the
    time, only for certain activities, or none of the time?*