Method of detecting neurological disease
A method and apparatus are provided for characterizing square wave jerks in the eye movements of a person, which may provide a powerful tool in the differential diagnosis of oculomotor and neurological disease. The method includes the steps of a) providing a sequence of saccades, b) identifying pairs of consecutive saccades of the sequence, c) determining whether each saccade of each identified pair is opposite the direction of the other saccade and, if not, then discarding the pair, d) determining whether a magnitude of each saccade of each identified pair is comparable and, if not, then discarding the pair, e) determining whether the pair of saccades of each identified pair are temporally related by a predetermined time period and, if not, then discarding the pair and f) collecting any remaining pairs of saccades as square wave jerks.
1. A method of detecting and characterizing square wave jerks (SWJs) in the eye movements of a person, for the diagnosis of progressive supranuclear palsy (PSP) disease comprising:
a) providing an apparatus for obtaining a sequence of saccades and obtaining a sequence of saccades from both eyes of a person;
b) identifying via an apparatus pairs of consecutive saccades of the sequence;
c) determining via an apparatus whether each saccade of each identified pair is opposite the direction of the other saccade and, if not, then discarding the pair;
d) determining via an apparatus whether a magnitude of each saccade of each identified pair is comparable and, if not, then discarding the pair;
e) determining via an apparatus whether the pair of saccades of each identified pair are temporally related by a predetermined time period and, if not, then discarding the pair;
f) collecting via an apparatus any remaining pairs of saccades as square wave jerks;
h) using an apparatus to determine one or more of the following parameters:
(A) the number of SWJs per second;
(B) the percentage of small saccades that are part of SWJs;
(C) the average magnitude of the saccades that are part of SWJs;
(D) the number of saccades per second;
(E) the average peak velocity of the saccades in SWJs;
(F) the standard deviation of the direction difference; and
(G) the standard deviation of the difference between the horizontal and direction of the saccades in the SWJs; and
h) comparing the one or more determined parameter with the parameter for a healthy person, whereby a statistical difference between the parameters indicates the presence of PSP.
2. The method of detecting and characterizing square wave jerks as in claim 1 further comprising defining the opposite direction of the saccades in the pairs as 180 degrees, plus or minus 80 degrees.
3. The method of detecting and characterizing square wave jerks as in claim 1 further comprising defining the magnitude of each saccades in the pairs comparable as the dissimilarity index is in the range ±100%.
4. The method of detecting and characterizing square wave jerks as in claim 1 further comprising defining the inter saccadic interval between the two saccades in the pair as the range 70 ms-650 ms.
5. The method of detecting and characterizing square wave jerks as in claim 1 wherein the step of providing the sequence of saccades further comprises identifying any pairs of saccades of the sequence that share a saccade and if the number identified pairs is an odd number, then discarding the pairs of the sequence in even positions within the sequence.
6. The method of detecting and characterizing square wave jerks as in claim 1 wherein the step of providing the sequence of saccades further comprises identifying any pairs of saccades of the sequence that share a saccade and if the number identified pairs is an even number, then discarding either the odd or even pairs of the sequence depending upon which provides a relatively longer average inter-saccadic interval.
7. The method of detecting and characterizing square wave jerks as in claim 1 , wherein a single apparatus is utilized.
8. An apparatus for detecting and characterizing square wave jerks (SWJs) comprising:
apparatus that obtains a sequence of saccades from a person;
apparatus that identifies a first pair of consecutive saccades of the sequence;
apparatus that determines whether the pair of saccades are opposite in direction and, if not, then discards the pair;
apparatus that determines whether a magnitude of each saccade of the pair is comparable and, if not, then discards the pair;
apparatus that determines whether the pair of saccades are temporally related by a predetermined time period and, if not, then discards the pair;
apparatus that forms a square wave jerk sequence from the pairs of saccades; and
apparatus that compares at least one of the number of SWJs per second, the percentage of small saccades that are part the SWJ sequence, the average magnitude of the saccades that are part of the SWJ sequence, the number of saccades per second, the average peak velocity of the saccades of the SWJ sequence, the standard deviation in the direction difference and the standard deviation of the difference between the horizontal and direction of the saccades of the SWJ sequence with a corresponding parameter of a healthy population of persons.
9. The apparatus for detecting and characterizing square wave jerks as in claim 8 further comprising defining the opposite direction of the pairs of saccades as 180 degrees, plus or minus 80 degrees.
10. The apparatus for detecting and characterizing square wave jerks as in claim 8 further comprising defining the magnitude of each saccades in the pairs comparable as the dissimilarity index is in the range ±100%.
11. The apparatus for detecting and characterizing square wave jerks as in claim 8 further comprising defining the inter saccadic interval between the two saccades in the pair as the range 70 ms-650 ms.
12. The apparatus for detecting and characterizing square wave jerks as in claim 8 wherein the means for providing the sequence of SWJs further comprises means for identifying any pairs of saccades of the sequence that share a saccade and if the number identified pairs is an odd number, then discarding the pairs of the sequence in even positions within the sequence.
13. The apparatus for detecting and characterizing square wave jerks as in claim 8 wherein the means for providing the sequence of SWJs further comprises means for identifying any pairs of saccades of the sequence that share a saccade and if the number identified pairs is an even number, then discarding either the odd or even pairs of the sequence depending upon which provides a relatively longer average inter-saccadic interval.
14. An apparatus for detecting and characterizing square wave jerks (SWJs) in a person comprising:
a saccade processor that provides a sequence of saccades from measured eye movements of a person;
a pairing processor that identifies a first pair of consecutive saccades of the sequence, that determines whether the two saccades in the pair have an opposite, horizontal direction and, if not, then discarding the pair, that determines whether a magnitude of each saccade of the pair is comparable and, if not, then discarding the pair, that determines whether the pair of saccades are temporally related by a predetermined time period and, if not, then discarding the pair and that forms a square wave jerk sequence from the pairs of saccades; and
a statistics processor that compares at least one of the number of SWJs per second, the percentage of small saccades that are part the SWJ sequence, the average magnitude of the saccades that are part of the SWJ sequence, the number of saccades per second, the average peak velocity of the saccades of the SWJ sequence, the standard deviation in the direction difference and the standard deviation of the difference between the horizontal and direction of the saccades of the SWJ sequence with a corresponding parameter of a healthy population of persons.
15. The apparatus for detecting and characterizing square wave jerks in claim 14 wherein the opposite direction further comprises the pairs of saccades having an angle difference of 180 degrees, plus or minus 80 degrees.
16. The apparatus for detecting and characterizing square wave jerks in claim 14 wherein the opposite direction further comprises the magnitudes of the pairs of saccades having a dissimilarity index of ±100%.
17. The apparatus for detecting and characterizing square wave jerks in claim 14 wherein the opposite direction further comprises the inter saccadic interval between the two saccades in the pair being in the range 70 ms-650 ms.
18. The apparatus for detecting and characterizing square wave jerks as in claim 14 wherein the pairing processor further comprises an elimination processor that identifies any pairs of saccades of the sequence that share a saccade and if the number identified pairs is an odd number, then discards the pairs of the sequence in even positions within the sequence.
19. The apparatus for detecting and characterizing square wave jerks as in claim 14 wherein the pairing processor further comprises an elimination processor that identifies any pairs of saccades of the sequence that share a saccade and if the number identified pairs is an even number, then discards either the odd or even pairs of the sequence depending upon which provides a relatively longer average inter-saccadic interval.