Ying-Sheng
Hu, Ph.D.
Associate Professor
Statistical Research
Learning Patterns
of Amblyopic Patients and Change Analysis
Amblyopia
is a spatial vision disorder that causes patients to suffer significant
reduction in visual acuity and positional acuity. Unfortunately, this serious
condition cannot be corrected with ordinary optical system, and it is
irreversible if treated late.
In searching for effective
remedies, optometry clinicians and visual scientists have developed a special
vision-training program for patients. According to the neural plasticity and
cognitive theory, one hopes that intensive visual practicing will allow
patients to accumulate their experience incrementally, until the positive
experience they have collected reaches a certain threshold where perceptual
learning should occur. This slow-sudden learning-phase transaction may repeat
until training has stopped.
More than 20 patients were accepted
into the training program during 1996-1997, and most patients experienced some
visual improvements after training. To assess the training effect on patients’
visual function (particularly in vernier acuity), the
following questions should be answered: (1) Is perceptual learning really
obtainable through training? (2) If a patient did learn, when did the learning
take place? and (3) What would the learning curve look like?
Statistical approach. (1) The definition
of perceptual learning: The instant at which learning occurs is transactional,
the mean vernier acuity prior to the moment changes
to a different level of vernier acuity. (2) We use CuSum method to locate the level change point in a series
of observations on vernier acuities. (3) We use an optimal
approximation approach to determine single or multiple level change points. (4)
Segmented regression.
Discussion. (1) The equivalence
between the CuSum and optimal approximation
approaches. (2) Assessment of the probability of a change.