Source: http://www.google.com/patents/US20070229760?dq=5,966,702
Timestamp: 2017-12-12 20:42:47
Document Index: 346099062

Matched Legal Cases: ['art 602', 'art 602', 'art 603', 'art 603', 'art 620', 'art 603', 'art 620', 'art 4', 'art 601', 'art 602', 'art 40', 'art 602', 'art 600', 'art 602', 'art 600', 'art 600', 'art 600', 'art 601', 'art 600', 'art 604', 'art 604', 'art 604', 'art 604', 'art 601', 'art 604', 'art 604', 'art 604', 'art 604', 'art 604', 'art 604', 'art 700', 'art 21', 'art 21']

Patent US20070229760 - Ophthalmologic measuring apparatus - Google Patents
A subject is placed in a more natural state or is encouraged to blink at specified intervals to obtain a measurement result under a fixed condition, and the judgment of the degree of dry eye is facilitated. A measurement part obtains, based on a reflected light flux from a subject eye, optical characteristic...http://www.google.com/patents/US20070229760?utm_source=gb-gplus-sharePatent US20070229760 - Ophthalmologic measuring apparatus
Publication number US20070229760 A1
Application number US 11/723,624
Also published as US7677728
Publication number 11723624, 723624, US 2007/0229760 A1, US 2007/229760 A1, US 20070229760 A1, US 20070229760A1, US 2007229760 A1, US 2007229760A1, US-A1-20070229760, US-A1-2007229760, US2007/0229760A1, US2007/229760A1, US20070229760 A1, US20070229760A1, US2007229760 A1, US2007229760A1
Inventors Yoko Hirohara, Toshifumi Mihashi
Referenced by (9), Classifications (4), Legal Events (4)
US 20070229760 A1
A subject is placed in a more natural state or is encouraged to blink at specified intervals to obtain a measurement result under a fixed condition, and the judgment of the degree of dry eye is facilitated. A measurement part obtains, based on a reflected light flux from a subject eye, optical characteristic data of a two-dimensional vector form representing the time course of each optical characteristic of the subject eye in an blink interval from a certain blink to a next blink with respect to the first to the nth blink intervals. An analysis part one-dimensionally arranges each of the optical characteristic data with respect to the first to the nth blink intervals measured by the measurement part, and arranges the one-dimensional arrangement of the optical characteristic in a p-th blink interval at a p column to create a two-dimensional array, and performs a principal component analysis processing on the two-dimensional array.
a measurement part that obtains, based on the received light signal formed by the light receiving part, optical characteristic data of a two-dimensional matrix form to represent a time course of each optical characteristic of the subject eye in a blink interval from a blink to a next blink with respect to a first to an n-th (n is an integer of 2 or more) blink intervals;
an analysis part that one-dimensionally arranges each of the optical characteristic data with respect to the first to the n-th blink intervals measured by the measurement part, arranges a one-dimensional array of the optical characteristic in a p-th (1≦p≦n) blink interval at a p-th column to create a two-dimensional matrix, and performs a principal component analysis processing on the two-dimensional matrix; and
2. The ophthalmologic measuring apparatus according to claim 1, wherein the optical characteristic data includes coefficients of Zernike polynomials.
3. The ophthalmologic measuring apparatus according to claim 1, wherein the analysis part subtracts a time average of each element from each element of the optical characteristic data measured by the measurement part, and forms the optical characteristic data.
the analysis part, with respect to principal components obtained by the principal component analysis processing, for each of the principal components of the two-dimensional matrix, converts the one-dimensional array at the p-th column into two-dimensional data to represent the time course of each optical characteristic, and arranges the first to the n-th optical characteristic data, reversely to a manner in which each of the optical characteristic data concerning the first to the n-th blink intervals measured by the measurement part is arranged one-dimensionally, to obtain a two-dimensional space representing a time change of each optical characteristic, and
5. The ophthalmologic measuring apparatus according to claim 1, wherein the display part displays, as a code map, typical gray codes or color codes of a normal, a light dry eye, an intermediate dry eye, and a serious dry eye, for judgment of a measured case, on a screen, or, the display part displays these gray scale codes or color codes on the screen by a simple operation.
6. The ophthalmologic measuring apparatus according to claim 1, further comprising a sign signal formation part to encourage a subject to blink,
wherein the measurement part measures the optical characteristic of the subject eye varying with elapsed time from an end of the blink of the subject.
7. The ophthalmologic measuring apparatus according to claim 1, further comprising a judgment part to detect a blink of a subject,
wherein when the judgment part detects the blink of the subject, the measurement part measures the optical characteristic of the subject eye varying with elapsed time from an end of the blink of the subject.
9. The ophthalmologic measuring apparatus according to claim 8, wherein the measurement part simultaneously measures the wavefront aberration of the whole subject eye based on the reflected light flux from the ocular fundus, and the cornea aberration of the cornea of the subject eye based on the reflected light flux from the corneal surface.
12. The ophthalmologic measuring apparatus according to claim 1, wherein
the measurement part measures a wavefront aberration of the whole subject eye based on the reflected light flux from the ocular fundus, and/or measures a corneal aberration of the cornea of the subject eye based on the reflected light flux from the corneal surface.
Non-Patent document 1: “41st The Japanese Society of Ophthalmological Optics, 20th Ophthalmologic ME Society, Joint Society General Meeting, Abstracting Journal”, Sep. 3, 2005, page 42
In view of the above, the invention has an object to provide an ophthalmologic measuring apparatus in which a measurement result is obtained under a fixed condition while a subject is in a more natural state, or a subject is encouraged to blink at specified periods and a measurement result under a fixed condition is obtained, judgment of the degree of dry eye is more facilitated, and meaningful measurement can be realized. The invention has another object to provide an ophthalmologic measuring apparatus which further includes an analysis part so that diagnosis assistance of dry eye useful for clinic is performed, and automatic diagnosis is also enabled.
FIG. 1 is a structural view of an optical system of an ophthalmologic measuring apparatus.
FIG. 12 is an explanatory view of a time change in corneal shape.
FIG. 13 is an explanatory view of a time change in blur of a Pracido ring image.
FIG. 17 is an explanatory view concerning a histogram when a blink does not occur.
FIG. 18 is an explanatory view concerning a histogram when a blink is occurring.
DETAILED DESCRIPTION OF THE INVENTION 1. Outline (Blink Interval Data)
(1) Data in a Blink Interval by a Blink sign First Embodiment
In this case, in conformity to a sign signal such as a metronome sound, a subject blinks at, for example, intervals of 10 seconds. At this time, measurement is performed at, for example, intervals of 1 second, and a measurement time is made one minute.
(2) Data in a Natural Blink Interval Second Embodiment
In this case, a natural blink of a subject is detected, measurement is performed in a period from a certain blink to a next blink, a change in aberration is extracted with respect to a common time from the blink, and a principal component analysis is performed.
The judgment part 602 mainly judges the presence/absence of the blink of the subject eye. When detecting the first blink, the judgment part 602 sends its signal to the sign signal formation part 603. The sign signal formation part 603 gives an instruction to generate a sign at specified time intervals to the sign generation part 620 based on the signal. In accordance with the instruction from the sign signal formation part 603, the sign generation part 620 generates the sign to encourage the subject to blink at intervals of a specified period (for example, 10 seconds). The sign may be anything as long as the subject can recognize, and for example, there are conceivable visual light generation, buzzer sounding appealing to the ear, and the like. As an example, in an aural type, in order to provide good timing, for example, rhythmic timing is produced like a metronome, timing is informed by a sound “pipipipii” like a telephone or a time signal of a television, or a signal to provide timing at intervals of 1 second is issued, and a tone of a blink sign is issued at intervals of 10 seconds.
4. Measurement Flowchart 4-1. Measurement Flowchart First Embodiment
FIG. 3 shows a measurement flowchart of a first embodiment.
4-2. Measurement Flowchart Second Embodiment
FIG. 4 shows a measurement flowchart of a second embodiment.
(1) corneal wavefront measurement mode,
(2) ocular wavefront measurement mode, and
(3) both-wavefront measurement mode of the corneal wavefront measurement mode and the ocular wavefront measurement mode.
Next, in a period in which the measurement part 601 measures the aberration, the judgment part 602 performs blink detection in real time while acquiring the anterior eye image by the anterior eye observation part 40 (S208 a). At this time, for example, 100 FPS (the number of captured images per second) can be set. In the case where a blink is detected by the judgment part 602, in order to perform measurement from the point when the blink is detected (for example, for the case where the blink occurs in the measurement interval of 1 second), the arithmetic part 600 returns N to the initial value (for example, N=0) (S208 b). On the other hand, in the case where the blink is not detected by the judgment part 602, the arithmetic part 600 judges whether or not a previously set measurement end time has occurred (S208 c). In the case where the measurement end time has not occurred, the arithmetic part 600 increments the variable N (in this example, N=N+1) (S208 d), a return is made to step S207, and the wavefront aberration measurement of the subject eye is performed. Here, the arithmetic part 600 repeats the wavefront aberration measurement processing by the measurement part 601 until the measurement end time has occurred, and obtains the wavefront aberration of the subject eye (S208 c). The arithmetic part 600 ends the measurement when the measurement end time has occurred, and a shift is made to step S211 of the principal component analysis.
1. Method in which a minimum value of a blink interval to be adopted is previously determined. 2. Method in which after a measurement value is seen, a blink interval to be adopted is determined.
First, a description will be given to “1. Method in which a minimum value of a blink interval to be adopted is previously determined”. For example, it is assumed that the blink interval to be adopted is 7 seconds or more. In this case, the analysis part 604 selects only a case where the blink interval is 7 seconds or more, and uses data up to 7 seconds therein. For example, when the measurement interval is 1 second, the unit of the principal component analysis becomes 25 rows by 7 columns. This is transformed into a one-dimensional vector similarly to the case of the fixed blink interval of the first embodiment. Then, the vector having 175 elements is formed. When the analysis part 604 arranges such vectors the number of which is the number of the previously selected blink intervals, a two-dimensional matrix for the principal component analysis is formed.
Next, a description will be given to “2. Method in which after a measurement value is seen, a blink interval to be adopted is determined”. In this case, with respect to plural blink intervals, the analysis part 604 sets an interval obtained as a rough blink interval. Alternatively, when the minimum value of the blink interval is a specified value (for example, 5 seconds) or more, the minimum value of the blink interval is made the measurement interval, and when it is not higher than the specified value, only values not lower than the specified value are made analyzable, and the minimum value therein is made the measurement interval. In addition, with respect to the plural blink intervals, it is judged whether data satisfies a condition of measurement interval and the like, and setting is performed. A specified number of data of blink intervals are adopted and the two-dimensional matrix is created.
5. Principal Component Analysis 5-1. Outline
Next, a description will be given to a method in which the principal component analysis is performed by using the matrix Z formed by the above procedure, and its interpretation is performed in the clinical field (incidentally, see, with respect to the principal component analysis, for example, “Haruo Yanai “Multivariate Data Analysis Method” Asakura Shoten”). Here, only minimum expressions necessary for performing the principal component analysis will be indicated.
S=(1/n)ZZ T
(n: the number of times of measurement in the time direction, in this example, because of 9 times and 6 sets, n=54). Next, an eigenvalue problem set forth below is solved.
Saj=λjaj
The covariance matrix S has an eigenvalue λj of the number of times of blink intervals, and an eigenvector aj. For example, under the measurement condition here, j=1 to 6, and 6 eigenvalues and 6 eigenvectors can be obtained.
Z′=(a 1 a 2 , . . . a m)
First, the analysis part 604 reads measurement data from the memory 800. Alternatively, the analysis part obtains measurement data from the measurement part 601 (step S301). In this example, as described above, the form of the measurement data is a matrix of 25 rows by 54 columns, the vertical 25 rows correspond to the Zernike coefficients, and the horizontal 54 columns correspond to the measurement points in the time direction. Besides, in the measurement data, 54 points in the time direction correspond to measurement data of (6 blink intervals)×(9 points in the time direction). Next, the analysis part 604 takes an average for the row of the measurement data, and subtracts the average from the data of each row (step S303). Next, the analysis part 604 regards the whole data (25 rows by 54 columns) as 6 arrays, each having 25 rows and 9 columns, for the respective blink intervals, transforms the two-dimensional array of 25 rows by 9 columns into a one-dimensional vector (the number of elements is 225), and further, the analysis part 604 arranges the one-dimensional data in the P-th blink interval at the P-th column (step S305). In this example, vectors each of which has 225 elements and the number of which is the number of times of blink, that is, 6 are arranged to create a matrix of 225 rows by 6 columns. Next, the analysis part 604 performs the principal component analysis while the matrix of 225 rows by 6 columns is made input data (step S307). The analysis part 604 transforms the obtained principal components into a two-dimensional array in the completely opposite direction to the transformation into the one-dimensional array at step S305, and stores the two-dimensional principal components into the memory 800 (step S309). The analysis part 604 reads the obtained two-dimensional principal components from the memory 800, executes the processing for display, and displays the gray scale map or color code map on the display part 700 (step S311).
Dry   eye   index 1 = Magnitude   of   first   principle   component   λ 1 ∑ i = 1 6  Magnitude   of   i  -  th   principle   component   λ i
The second example is the sum of all principal components (λ1 to λ6) as indicated by a following expression.
Dry   eye   index 2 = ∑ i = 1 6  Magnitude   of   i  -  th   principle   component   λ i
It is estimated that as the dry eye index 1 becomes small, or as the dry eye index 2 becomes large, the degree of dry eye is large.
6-1. Measurement of Corneal Shape: S107
FIG. 11 is a flowchart of a corneal shape measurement. This corresponds to the step S107 of FIG. 3.
Hereinafter, the step S405 will be described. As an example, a measurement method of the corneal shape will be described along “Rand R H, Howland H C, Applegate R A “Mathematical model of a placido disk karatometer and its implications for recovery of corneal topography”, Optometry and Vision Science 74 (1997) p 926-930”.
x s = 2  ( z s - f ) f x 2 + f y 2 - 1  f x ,    y s = 2  ( z s - f ) f x 2 + f y 2 - 1  f y
( x s 2 + y x 2 ) = Constant
f  ( x , y ) = ∑ j = - i , - i + 2 , , , i - 2 , i 6  c i j  Z i j  ( x r n , y r n )
W  ( X , Y ) = ∑ i = 0 n  ∑ j = 0 i  c i 2  j - i  Z i 2  j - i  ( X , Y )
∂ W  ( X , Y ) ∂ X = Δ   x f ,  ∂ W  ( X , Y ) ∂ Y = Δ   y f
Where, the Zernike polynomials Zi 2j−1 is expressed by a following expression.
Z n m = R n m  ( r )  { sin cos }  { m   θ } m > 0   sin m ≦ 0   cos R n m  ( r ) = ∑ S = 0 ( n - m ) / 2  ( - 1 ) S  ( n - S ) ! S !  { 1 2  ( n - m ) - S } !  { 1 2  ( n + m ) - S } !  r m
Incidentally, with respect to the Zernike coefficients ci 2j−l, specific values can be obtained by minimizing the square error expressed by a following mathematical expression.
S  ( x ) = ∑ i = 1 data   number  [ { ∂ W  ( X i , Y i ) ∂ X - Δ   x i f } 2 + { ∂ W  ( X i , Y i ) ∂ Y - Δ   Y i f } 2 ]
Where, W(X, Y): wavefront aberration, (X, Y): Hartmann plate coordinates, (Δx, Δy): movement distance of the point image received by the first light receiving part 21, and f: distance between the Hartmann plate 22 and the first light receiving part 21.
RMS i 2  j - i = ɛ i 2  j - i 2  ( i + 1 )  c i 2  j - i  ( ɛ i 2  j - i = 2  ( 2  j = i ) , ɛ i 2  j - i = 1  ( 2  j ≠ i ) )
The invention can be widely applied to an ophthalmologic measuring apparatus, a surgical apparatus and the like.
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