Biomedical Engineering Reference
In-Depth Information
Figure 5.1. Test battery design consisting of three main pillars to address conflicting
requirements. These pillars are 1st: a set of psychophysical tests, 2nd: a set of tests
to estimate performance in tasks of daily living, 3rd: a set of questionnaire to address
subjective perception.
The first pillar is based on classical psychophysical testing utilizing and
extending regular clinical ophthalmologic tests. These tests can be highly
standardized, and examiner and patient bias can be minimized. Thus this pillar of
the test design mainly contributes to good reliability, validity, and objectiveness
of the whole set of tests. However, this kind of tests could turn out to be the least
relevant ones in terms of the needs of a patient in coping with everyday life.
The second pillar therefore consists of a setup for testing performance in
everyday tasks. This should consist of tests that are as close to real conditions
as possible to be relevant, but as “artificial” as needed to be well standardized.
As AVDs may provide visual impressions that are different from natural vision,
this test is highly important to gain an estimate about the efficacy of such
devices in supporting blind patients in leading a more independent life. Testing
performance in activities of daily life is not a well-standardized task and there
are some methodological obstacles. As there is no direct physical correlation
that can be measured, the test has to rely on indirect measuring techniques.
The patient himself, or better in cooperation with an experienced, independent
mobility trainer, has to give an assessment of performance in this test. As this
proceeding is prone to reasonable subjectivity by nature, strategies to control
this handicap gain great importance. These strategies include a double-blind or
placebo-controlled test design as well as the use of standardized subjective scales
rather than free descriptions or even narrations of the patient.
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