Generic function for presentation of stimulus stim.
Depending on your choice of OPI implementation set using
chooseOpi(),
different parameters are available for opiPresent.
opiPresent(stim, nextStim=NULL, ...)A list of class opiStaticStimulus, opiKineticStimulus, or
opiTemporalStimulus.
As for stim, but the next presentation to be made.
This might be useful
on some machines, particularly projector based systems, where preparations
for the next presentation can be made while waiting for a response to the
current.
Parameters specific to your chosen opi implementation.
A list containing
NULL if no error occurred, otherwise a machine specific error
message.
This should include errors when the specified size cannot be achieved by
the device (for example, in a projection system with an aperture wheel of
predefined sizes.) If stim is NULL, then err contains the status of the
machine.
TRUE if a response was detected in the allowed
responseWindow, FALSE otherwise. (Note, see Octopus900F310 above).
The time in milliseconds from the onset (or offset, machine
specific) of the presentation
until the response from the subject if seen is TRUE.
If seen is FALSE, this
value is undefined.
For kinetic perimetry on the O900, this value is unknown...
Only returned for Octopus600. Can be the following values:
0 = stimulus not seen;
1 = stimulus seen;
132 = Response button was pressed before stimulus presentation (Patient needs a break - hold on examination);
36 = Eye is closed before stimulus presentation;
68 = Fixation lost before stimulus presentation (pupil center is out of green window in video image);
260 = Forehead rest lost before stimulus presentation;
516 = Fast Eye movements before stimulus presentation;
258 = Forehead rest lost during stimulus presentation;
66 = Fixation lost during stimulus presentation (pupil center is out of green window in video image);
34 = Eye was closed during stimulus presentation;
18 = Patient answer was too early (<=100ms after stimulus presentation) - lucky punch;
514 = Fast Eye movements during stimulus presentation
Only returned for KowaAP7000 and an opiStaticStimulus or O900 and staic/kinetic. x-coordinate of centre of pupil in pixels during presentation.
Only returned for KowaAP7000 and an opiStaticStimulus or O900 and staic/kinetic. y-coordinate of centre of pupil in pixels during presentation.
Only returned for KowaAP7000 and an opiStaticStimulus. x-coordinate of centre of Purkinje Image in pixels during presentation.
Only returned for KowaAP7000 and an opiStaticStimulus. y-coordinate of centre of Purkinje Image in pixels during presentation.
Only returned for KowaAP7000 or Octopus900 and an opiKineticStimulus. x coordinate of stimuli when button is pressed.
Only returned for KowaAP7000 or Octopus900 and an opiKineticStimulus. y coordinate of stimuli when button is pressed.
Only returned for Compass. Time since epoch that the opiPresent command was received by the Compass in ms.
Only returned for Compass. Hardware time of button press or response window expired (integer
ms).
To get the hardware time that a presentation began, subtract responseWindow from th (for aligning with
fixation data returned by opiClose().
Only returned for Compass. Time since epoch that the response was received or response window expired (in ms).
Only returned for Compass. The number of tracking events associated with this presentation.
Only returned for Compass. The number of time the motor could not keep pace with eye movements.
Only returned for Compass. The diameter of the pupil on milimetres on presentation.
Only returned for Compass. The x location in pixels of the presentation on the retinal image returned
by opiInitialize.
Only returned for Compass. The y location in pixels of the presentation on the retinal image returned
by opiInitialize.
opiPresent
is blocking in that it will not return until either a response
is obtained, or at least the responseWindow milliseconds has expired. (Note
that more time might have expired.) Specifying nextStim
allows the implementing
machine to use the time waiting for a
response to stim to make preparations
for the next stimuli. (For example retargeting the projector or moving
aperture and/or filter wheels.)
There is no guarantee that the next call to
opiPresent will have nextStim as the first argument; this
could be checked by the machine specific implementations (but currently is not, I think).
Also note that to allow for different parameters depending on the
implementation chosen with chooseOpi, every parameter MUST
be named in a call to opiPresent.
opiPresent(stim, nextStim=NULL, fpr=0.03, fnr=0.01, tt=30)
If the chosen OPI implementation is SimHenson, then
the response to a stimuli is determined by sampling from a
Frequency-of-Seeing (FoS) curve (also known as the psychometric
function) with formula $$\mbox{fpr}+(1-\mbox{fpr}-\mbox{fnr})(1-\mbox{pnorm}(x, \mbox{tt},
\mbox{pxVar})),$$
where \(x\) is the stimulus value in Humphrey dB, and pxVar is
$$\min\left(\mbox{simH.global.cap}, e^{A\times\mbox{tt}+B}\right).$$
The ceiling simH.global.cap
is set with the call to opiInitialize, and A and B
are from Table 1 in Henson et al (2000). Which values are used is
determined by simH.type which is also set in the call to
opiInitialize.
Note that if the stimulus value is less than zero, then the Henson
formula is not used. The probability of seeing is fpr.
opiPresent(stim, nextStim=NULL, fpr=0.03, fnr=0.01, tt=NULL,
criteria=0.95, rt_shape=5.3, rt_rate=1.4, rt_scale=0.1)
For determinng seen/not-seen for kinetic, the first location (to a fidelity of
0.01 degrees) on the path (it only works for single paths now) where the probability of seeing
is equal to criteria is found.
If no such location exists, then the stimuli is not seen.
The probability of seeing at each location
is determined using a frequency-of-seeing curve defined
as a cumulative Gaussian with parameters controlled by tt and
opiInitialize.
At each location along the path, the mean of the FoS is taken from the
tt function, which takes a distance-along-path (in degrees)
as an argument, and returns a dB value which is the static threshold
at that distance along the path.
Function tt can return NA for not thresholds that are always not seen.
At each location along the path, the standard deviation
of the FoS is sampled from a Gaussion with mean
taken from the formula of Henson et al (2000),
as parametrised by opiInitialize, and standard deviation 0.25.
The location of a false positive response (for the total kinetic path) is sampled uniformly from the start of the path to the 'seeing' location, or the entire path if the stimuli is not seen.
Note that the false positive rate fpr and the false negative rate
fnr
are specified for the whole path, and not for the individual static responses
along the way.
The actual location returned for a seen response
is the location where the probability of seeing equals criteria,
plus a response time sampled from a Gamma distribution parameterised
by rt_shape and rt_rate and multiplied by rt_scale.
That is: rgamma(1, shape=rt_shape, rate=rt_rate) / rt_scale.
opiPresent(stim, nextStim=NULL, fpr=0.03, fnr=0.01, tt=30, dist=stim$level - tt)
For static stimuli, this function is the same as for SimHenson, but reaction
times are determined by sampling from rtData as passed to
opiInitialize. The dist parameter is the distance
of the stimulus level from the true threshold, and should be in the
same units as the Dist column of rtData. The default
is just the straight difference between the stimulus level and the
true threshold, but you might want it scaled somehow to match
rtData.
opiPresent(stim, nextStim=NULL, fpr=0.03, fnr=0.01, tt=30)
If the chosen OPI implementation is SimGaussian, then
the response to a stimuli is determined by sampling from a
Frequency-of-Seeing (FoS) curve (also known as the psychometric
function) with formula fpr+(1-fpr-fnr)*(1-pnorm(x, tt, simG.global.sd)),
where x is the stimulus value in Humphrey dB, and simG.global.sd is
set with opiInitialize.
opiPresent(stim, nextStim=NULL)
If the chosen OPI implementation is SimYes, then
the response to a stimuli is always yes, hence opiPresent always returns
err=NULL, seen=TRUE, and time=0.
opiPresent(stim, nextStim=NULL)
If the chosen OPI implementation is SimNo, then
the response to a stimuli is always no, hence opiPresent always returns
err=NULL, seen=FALSE, and time=0.
opiPresent(stim, nextStim=NULL)
This functions as for the Octopus900, but responses are
taken from the F310 Controller.
If the L button is pressed, seen is set to 1.
If the R button is pressed, seen is set to 2.
If no button is pressed within responseWindow, then seen is set to 0.
opiPresent(stim, nextStim=NULL)
If the chosen OPI implementation is Octopus600, then nextStim is ignored. If eyeControl is non-zero,
as set in opiInitialize, answer codes describing patient state may arise (see answer field in the Value section).
opiPresent(stim, nextStim=NULL)
If the chosen OPI implementation is KowaAP7000, then nextStim is ignored.
opiPresent(stim, nextStim=NULL)
If the chosen OPI implementation is Compass, then nextStim is ignored.
Note that the dB level is rounded to the nearest integer.
If tracking is on, then this will block until the tracking is obtained, and the stimulus presented.
If the chosen OPI implementation is DayDream, then nextStim is ignored.
Note that the dB level is rounded to the nearest cd/\(\mbox{m}^2\) that is in the lut specified in
opiInitialise.
Currently uses the most simple algorithm for drawing a 'circle' (ie not Bresenham's).
Currently only implemented for opiStaticStimulus.
Please cite: A. Turpin, P.H. Artes and A.M. McKendrick "The Open Perimetry Interface: An enabling tool for clinical visual psychophysics", Journal of Vision 12(11) 2012.
http://people.eng.unimelb.edu.au/aturpin/opi/index.html
David B. Henson, Shaila Chaudry, Paul H. Artes, E. Brian Faragher, and Alec Ansons. Response Variability in the Visual Field: Comparison of Optic Neuritis, Glaucoma, Ocular Hypertension, and Normal Eyes. Investigative Ophthalmology & Visual Science, February 2000, Vol. 41(2).
opiStaticStimulus,
opiKineticStimulus,
opiTemporalStimulus,
chooseOpi
opiInitialize
# NOT RUN {
# Stimulus is Size III white-on-white as in the HFA
makeStim <- function(db, n) {
s <- list(x=9, y=9, level=dbTocd(db, 10000/pi), size=0.43, color="white",
duration=200, responseWindow=1500)
class(s) <- "opiStaticStimulus"
return(s)
}
chooseOpi("SimHenson")
if (!is.null(opiInitialize(type="C", cap=6)))
stop("opiInitialize failed")
result <- opiPresent(stim=makeStim(10,0), tt=30, fpr=0.15, fnr=0.01)
# Will not work as 'stim' is not named
#result <- opiPresent(makeStim(10,0), tt=30, fpr=0.15, fnr=0.01)
if (!is.null(opiClose()))
warning("opiClose() failed")
# Same but with simulated reaction times
chooseOpi("SimHensonRT")
data(RtSigmaUnits)
if (!is.null(opiInitialize(type="C", cap=6, rtData=RtSigmaUnits)))
stop("opiInitialize failed")
dist <- (10 - 30)/min(exp(-0.098 * 30 + 3.62), 6)
result <- opiPresent(stim=makeStim(10,0), tt=30, fpr=0.15, fnr=0.01, dist=dist)
if (!is.null(opiClose()))
warning("opiClose() failed")
# }
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