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Claims  |
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We claim:
1. An apparatus for measuring molecular changes in a patient having an
ocular lens that, when illuminated, is capable of backscattering radiation
including fluorescent and Rayleigh components of determinable intensities,
comprising:
a. means for illuminating the ocular lens with light having a wavelength
between approximately 400-430 nm, thereby causing the ocular lens to
backscatter radiation in response to the illumination;
b. means, responsive to the backscattered radiation, for collecting the
backscattered radiation;
c. means, connected to the collecting means, for separating the
backscattered radiation into its fluorescent and Rayleigh components; and
d. means, connected to the separating means, for (i) detecting the
intensity of each of the separated fluorescent and Rayleigh components and
(ii) forming the ratio of the detected intensities, thereby producing a
measurement of molecular changes in the ocular lens.
2. An apparatus according to claim 1 in which the illuminating means
comprises:
a. a light source selected from the group consisting of lasers, laser
diodes coupled to nonlinear frequency doubling devices, light emitting
diodes, and broadband sources coupled to optical filters;
b. a lens, optically responsive to the light from the light source, for
focusing the light; and
c. a lens system, optically responsive to the focused light, having a
focus, and defining an aperture at its focus greater than approximately
fifteen micrometers.
3. An apparatus according to claim 2 further comprising an eyepiece means,
responsive to the backscattered radiation, for permitting an operator to
view the ocular lens.
4. An apparatus according to claim 3 in which the separating means
comprises at least one dichroic beam splitter.
5. An apparatus according to claim 4 in which the detecting and forming
means comprises at least one single chip silicon detector and the
wavelength of the fluorescent component of the backscattered radiation is
selected from the group consisting of between approximately 460-500 nm and
520-600 nm.
6. An apparatus according to claim 5 in which the detecting and forming
means further comprises an amplifier.
7. An apparatus according to claim 6 in which the illuminating means
further comprises means for adjusting the power level of the illuminating
light.
8. An apparatus for measuring molecular changes in a patient having an
ocular lens having a volume that, when illuminated, is capable of
backscattering radiation including fluorescent and Rayleigh components of
determinable intensities, comprising:
a. a laser for providing light having a selected wavelength and power
level;
b. means, optically responsive to the provided light, for adjusting the
power level of the light;
c. a lens, optically connected to the adjusting means, for focussing the
light;
d. a first optical fiber, optically connected to the lens, for receiving
the focused light;
e. a lens system, optically connected to the first optical fiber and
defining an aperture having a focus greater than approximately fifteen
micrometers, for delivering the focused light to a selected approximately
two hundred micrometers of the volume of the ocular lens, thereby causing
the ocular lens to backscatter radiation in response to the delivered
light;
f. a collector (i) having a focal point encompassing the selected volume of
the ocular lens to which the focused light is delivered and (ii)
responsive to the backscattered radiation, for collecting the
backscattered radiation;
g. a second optical fiber, optically connected to the collector, for
receiving the collected radiation;
h. means, connected to the connecting means, for separating the
backscattered radiation into its fluorescent and Rayleigh components; and
i. means, connected to the separating means, for (i) detecting the
intensity of each of the separated fluorescent and Rayleigh components and
(ii) forming the ratio of the detected intensities, thereby producing a
measurement of molecular changes in the optical lens.
9. An apparatus according to claim 8 in which the wavelength is
approximately 406.7 nm, the separating means is a spectrometer, and the
detecting and forming means comprises a computer.
10. An apparatus according to claim 9 further comprising an eyepiece means
responsive to the backscattered radiation, for permitting an operator to
view the selected volume of the ocular lens, and in which the measured
molecular changes assist in diagnosing conditions selected from the group
consisting of diabetes, the prediabetic condition, and cataracts.
11. An apparatus according to claim 8 in which the separating means
comprises at least one dichroic beam splitter.
12. An apparatus according to claim 11 further comprising an eyepiece means
responsive to the backscattered radiation, for permitting an operator to
view the selected volume of the ocular lens, and in which the measured
molecular changes assist in diagnosing conditions selected from the group
consisting of diabetes, the prediabetic condition, and cataracts.
13. A method for measuring molecular changes in a patient having tissue
that, when illuminated, is capable of backscattering radiation including
fluorescent and Rayleigh components of determinable intensities,
comprising the steps of:
a. illuminating the tissue with light having a wavelength selected from the
group consisting of between approximately 400-430 nm and between
approximately 800-860, thereby causing the tissue to backscatter radiation
in response to the illumination;
b. separating the backscattered radiation into its fluorescent and Rayleigh
components;
c. detecting the intensity of each of the separated fluorescent and
Rayleigh components; and
d. forming the ratio of the detected intensities.
14. A method according to claim 13 in which the illuminating step comprises
the steps of:
a. providing a light source selected from the group consisting of lasers,
laser diodes coupled to nonlinear frequency doubling devices, light
emitting diodes, and broadband sources coupled to optical filters, for
emitting the light at a wavelength of approximately 406.7 nm; and
b. focusing the light using a lens system having a focus and defining an
aperture at its focus greater than approximately fifteen micrometers; and
further comprising the step of comparing the ratio of the detected
intensities against at east one preselected value for assisting in
diagnosing conditions selected from the group consisting of diabetes and
the prediabetic condition.
15. A method according to claim 14 in which the detecting step comprises
the step of detecting the separated fluorescent component at a wavelength
selected from the group consisting of between approximately 460-500 nm and
520-600 nm and in which the comparing step comprises the step of comparing
the ratio of the detected intensities against two preselected values,
thirteen and fifteen, so that if the ratio is less than thirteen the
patient may be diagnosed as unlikely to have the selected condition and if
the ratio is greater than fifteen the patient may be diagnosed as likely
to have the selected condition.
16. A method according to claim 15 in which the separating step comprises
the step of separating the backscattered radiation using at least one
dichroic beam splitter. |
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Claims |
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Description |
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This invention relates to evaluating changes in biological tissues and more
specifically to apparatus and methods for quantitatively measuring
molecular changes in the lens of the eye.
BACKGROUND OF THE INVENTION
Existing methods for diagnosing diseases, particularly diabetes, are often
less than desirable. One such method, the oral glucose tolerance test,
attempts to assist diagnosis of diabetes mellitus by determining whether
elevated blood glucose levels exist in patients suspected of having the
disease. Because many patients having elevated levels fail subsequently to
develop the clinical symptoms of the disease, however, the reliability of
the test is generally questioned.
A second diagnostic method, the Islet Cell Antibody (ICA) test, may be used
to predict those patients at risk for type I diabetes and can predate the
onset of debilitating clinical symptoms by as much as five years. The ICA
test is not typically utilized, however, because of its complexity,
expense, and lack of specificity and because of a lack of standardization
among evaluating laboratories. Furthermore, the test is useful only for
detecting type I diabetes, which strikes only approximately ten percent of
the entire diabetic patient population. By contrast, patients suspected of
having the prediabetic condition for type II diabetes currently have no
confirming diagnostic procedure.
It is well known that certain portions of the eye fluoresce when
illuminated. The lens of the eye, for example, can be made to fluoresce
intensely when illuminated with radiation having a wavelength between
approximately 350 nm and 550 nm. Utilizing radiation of a wavelength less
than approximately 400 nm typically is avoided (unless power levels and
exposure times are restricted), however, since this higher frequency
radiation is known to cause damage to ocular tissue.
The presence of certain diseases in the human body cause chemical changes
in the lens of the eye, altering the amount of the fluorescent response to
an illumination of the lens. The lenses of cataract patients, for example,
become opaque due to lipid peroxidation, protein glycosylation, and the
conversion of sulfhydryl (--SH) bonds to disulfide bonds (--SS).
Similarly, in diabetes mellitus and galactosemia, the glucose and
galactose are converted to sorbitol and dulcitol, respectively.
Accumulation of these compounds results in a high osmotic gradient within
the lenticular cells. Prolonged therapy with drugs such as corticosteroids
and chlorpromazine also causes opacities of the human lens.
U.S. Pat. Nos. 4,895,159 and 4,883,351 to Weiss (which patents are
incorporated herein in their entireties by this reference), thus, disclose
methods for detecting the existence of diabetes using light scattered from
lenticular cells. As described in the Weiss patents, the backscattered
light from a patient suspected of having diabetes is used to calculate a
diffusion coefficient for that patient. A second determination of
diffusion coefficients is made for a control group of nondiabetic
patients, and the diffusion coefficient of the suspected diabetic is
compared with those of nondiabetic, control group patients of the same
age.
Because lenses typically cloud naturally as patients age, however,
measurements made in connection with the methods of the Weiss patents can
be taken only from clear sites in the patients' lenses. The Weiss
techniques also appear unable to distinguish the ultimate cause of changes
in diffusion coefficients or to detect the prediabetic condition (i.e.
where no overt clinical signs of diabetes are displayed but will be
exhibited within approximately five years as, for example, when a positive
ICA test occurs), since myriad diseases and physiological conditions are
known to affect the lens in the manner therein described. Use of the
diffusion coefficient as a stand-alone diagnostic test also suffers from
its variability as a function of patient age, particularly since results
have both age-dependent and age-independent variance.
Other patents, such as West German Patent No. 261957A1 to Schiller and U.S.
Pat. No. 4,852,987 to Lohmann (each of which is incorporated herein in its
entirety by this reference), describe alternate diagnostic methods in
which the fluorescence signal intensities are compared. The Schiller
patent, for example, discloses comparing fluorescence signal intensities
at two wavelengths using a single excitation wavelength in an effort to
detect the presence of cataracts. The ratio of the resulting fluorescence
intensities is compared to the ratio obtained at the same wavelengths from
known cataract patients to achieve the desired diagnostic result. As
described in the Schiller patent, the excitation wavelengths are selected
from the ranges 320-340 nm, 380-390 nm, and 430-450 nm, while the
intensity of fluorescence peaks is measured within wavelength ranges of
410-440 nm, 450-460 nm, and 500-520 nm. In contrast to the Schiller
patent, the Lohmann patent measures the magnitude of fluorescence
intensity at a single wavelength created by light of one excitation
wavelength and compares this intensity to known intensities at the given
wavelengths in order to determine the degree of eye lens cloudiness.
Neither of these patents, however, teaches or suggests detection of
diabetes or the prediabetic condition.
SUMMARY OF THE INVENTION
The present invention provides apparatus and methods for noninvasively
diagnosing selected diseases, including diabetes and the prediabetic
condition, in tissues of humans or other animals. Utilizing a narrow-band
light source of wavelength between 400-430 nm (and, preferably,
approximately 406.7 nm) from a laser or similar device and a confocal lens
system, the present invention illuminates the ocular lens tissue and
determines the intensity of the backscattered radiation at both the peak
of the fluorescent response (typically at approximately 490 nm within the
range 460-500 nm) and the peak of the Rayleigh component (at the
excitation wavelength). The detected radiation subsequently is transmitted
to a spectrometer to be divided into its various components (e.g.
fluorescence and Rayleigh). The intensity of the fluorescent component is
then normalized to the intensity of the Rayleigh component by forming the
ratio of the fluorescent intensity to the Rayleigh intensity. The relative
amounts of the backscattered fluorescent and Rayleigh radiation provide a
reliable indicator of the onset and progression of diseases such as
diabetes mellitus, the prediabetic condition, and cataracts in the human
or other body.
Unlike existing techniques such as those described above, the present
invention essentially eliminates the age-dependent measurement variations
previously shown to be present. By measuring the Rayleigh component of the
backscattered radiation and using it for normalization, the precise amount
of illumination energy delivered to the subject lens tissue area relative
to the amount of fluorescence signal generated by the tissue can be
determined. This approach reduces complications associated with variances
in lens opacity which can alter, in an unknown fashion, the level of
illumination delivered to the subject area. By diminishing the effect of
the subjects' ages on the test results, the technique permits
establishment of a clear threshold--independent of age--separating the
diabetic and prediabetic patients from those without the disease. The
invention also neither requires use of a coherent light source nor suffers
from the lack of specificity (existing in, e.g., the Weiss techniques) in
discriminating the ultimate cause of the effect being measured.
It is therefore an object of the present invention to provide apparatus and
methods for noninvasively diagnosing diabetes mellitus, the prediabetic
condition, cataracts, and the presence of other diseases.
It is another object of the present invention to provide apparatus and
methods permitting normalization of a fluorescence signal scattered from a
subject eye by the Rayleigh component of the scattered radiation.
It is a further object of the present invention to provide apparatus and
methods essentially eliminating the age-dependent measurement variations
previously shown to be present in existing diagnostic techniques.
It is yet another object of the present invention to provide apparatus and
methods for monitoring the lens tissue over time for, e.g., evaluating the
efficacy of diabetes mellitus treatment or preventative techniques dealing
with the prediabetic condition.
Other objects, features, and advantages of the present invention will
become apparent with reference to the remainder of the written portion and
the drawings of this application.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of an apparatus of the present
invention.
FIG. 2 is a schematic representation of an alternate embodiment of the
apparatus of FIG. 1.
FIG. 3 is a graphical representation of the fluorescent signal intensity as
a function of age of both diabetic and nondiabetic patients obtained using
the apparatus of FIG. 1 as described in the EXAMPLE herein.
FIG. 4 is a graphical representation of the ratio of the fluorescent to
Rayleigh signal intensities as a function of age of both diabetic and
nondiabetic patients obtained using the apparatus of FIG. 1 as described
in the EXAMPLE herein.
FIG. 5 is a graphical representation of the fluorescent signal intensity as
a function of age of both diabetic and nondiabetic patients obtained using
the apparatus of FIG. I for an illumination radiation wavelength outside
the range of that used in connection with the present invention.
FIG. 6 is a graphical representation of the ratio of the fluorescent to
Rayleigh signal intensities as a function of age of both diabetic and
nondiabetic patients obtained using the apparatus of FIG. 1 for an
illumination radiation wavelength outside the range of that used in
connection with the present invention.
DETAILED DESCRIPTION
FIG. 1 illustrates an optical system 5 of the present invention. Optical
system 5 includes a light source 15, lens 25, a confocal lens system 35,
collector 45, and a spectrometer 55. Source 15, which provides narrow-band
illumination, typically may be a low power krypton laser tuned to produce
radiation having a wavelength between approximately 400-430 nm. In one
embodiment of optical system 5, source 15 provides radiation at a
wavelength of 406.7 nm. Also shown in FIG. 1 are ocular lens tissue L,
attenuator 65, eyepiece 75, detection and processing assembly 85, an fiber
optic waveguides 95 and 105.
According to FIG. 1, attenuator 65, used to reduce the power level of the
transmitted radiation, receives radiation from source 15 and forwards it
to lens 25. Lens 25, which may be a 40.times. microscope objective or
other similar device, then focuses the (attenuated) radiation onto the end
of waveguide 95, which in turn transmits the radiation to confocal lens
system 35. Lens system 35 subsequently delivers the radiation to a
selected volume of ocular lens tissue L (typically approximately 200 cubic
micrometers). A modified slit lamp base may be used to house and position
lens system 35 for easy access to lens tissue L, while lens system 35
itself is designed to permit the same volume of lens tissue L to be held
in the focal point of collector 45. In an embodiment of the present
invention consistent with FIG. 1, the aperture 115 of lens system 35 at
its focus is greater than approximately fifteen micrometers, ensuring that
the excitation radiation diverges rapidly after passing through the focal
point of lens system 35 and thereby reducing the spot intensity of the
radiation should it encounter any other portions of the ocular tissue.
Collector 4 receives the radiation backscattered from lens tissue L as a
result of it being illuminated by radiation from source 15. From collector
45, the backscattered radiation is directed into waveguide 105 and
transmitted to the entrance slit 125 of the monochromator 135 forming
spectrometer 55. If desired, collector 45 also may direct a portion of the
backscattered radiation to eyepiece 75, permitting an operator to view the
exact location of the selected volume of lens tissue L.
Division and processing of the backscattered radiation occurs in
spectrometer 55 and detection and processing assembly 85. Radiation
transmitted to spectrometer 55 initially is separated into its Rayleigh
and florescence components. The two components subsequently are directed,
respectively and as necessary, to amplifiers forming part of assembly 85,
for determination of the intensities of each. Assembly 85 also may include
a digital computer or similar computing device for forming the ratio of
the fluorescent and Rayleigh components of the backscattered radiation,
thereby normalizing the peak intensity of the fluorescent component.
An alternate embodiment 10 of optical system 5 is illustrated in FIG. 2.
According to FIG. 2, light source 20, which may be a laser diode, produces
radiation of wavelength approximately 813.4 nm (within the range of
approximately 800-860 nm) and is coupled to a nonlinear frequency doubling
device 30 to produce the desired wavelength output of 406.7 nm (within the
range 400-430 nm). Light source 20 alternatively may be a laser, light
emitting diode, or other narrow-band light source (including broadband
sources coupled to optical filters). The radiation subsequently is
directed through an optical delivery system 40 into the eye 50 of a
patient. As with the optical system 5 of FIG. 1, alternate embodiment 10
includes an optical collector 60 confocal to the delivery system 40 to
collect the backscattered radiation from the lens of eye 50. Similarly as
noted above, the backscattered radiation collected includes both a
fluorescence signal (typically approximately 490-500 nm within the range
460-500 nm, or within the range 520-600 nm) and an intense Rayleigh
component at the illumination wavelength.
FIG. 2 additionally discloses means for separating the components of
interest of the backscattered radiation, including dichroic beam splitters
70 and 90, and for detecting the intensity of the components
simultaneously using single chip silicon detectors 100 and 120 or similar
devices. Alternatively, component separation may be accomplished using
beam splitters in conjunction with optical bandpass filters or dispersive
elements such as diffraction gratings. Hybrid detector/filter assemblies
also may be used. Electronic circuitry 130, such as but neither limited to
nor necessarily requiring analog amplifiers, analog to digital (A/D)
converters, and a digital computer, processes the data detected by
detectors 100 and 120, calculates the normalized fluorescent/Rayleigh
component ratio, and, if desired, makes the result available to an
operator through a digital display or other suitable means. Eyepiece 80,
finally, may be used by the operator to view the location of the
excitation focal point in eye 50.
The present invention may further be understood with reference to the
following non-limiting EXAMPLE.
EXAMPLE
FIGS. 3-6 illustrate data obtained from clinical trials conducted using
sixty-nine (69) human patients aged twelve (12) to sixty-five (65).
Forty-eight (48) of the patients had previously been diagnosed as having
diabetes, while the remaining twenty-one (21) had not. FIGS. 3 shows the
total fluorescence signal obtained for each patient (expressed in
"Counts.times.10.sup.5," where the number of Counts is a function of the
number of emitted photons per unit time) using an illumination wavelength
of 406.7 nm. FIG. 4 details the results when those same fluorescence
signals ar normalized by the Rayleigh component of the backscattered
radiation in accordance with the present invention. As illustrated in FIG.
4, although the normalized signals trend upward as a function of age, they
evidence clear distinctions between those patients known to have diabetes
or the prediabetic condition and those who did not. The normalized signals
for the nondiabetics, for example, were less than thirteen (13), while
those for diabetics exceeded fifteen (15).
By contrast, use of an illumination wavelength of 441.6 nm (outside the
range of the present invention) produced much less desirable results.
FIGS. 5-6, which correspond, respectively, to FIGS. 3-4, show (in FIG. 6)
much less of a distinction between the normalized signals for the diabetic
as opposed to nondiabetic patients. Furthermore, those patients who tested
ICA positive are shown to have fluorescent/Rayleigh ratios within the
range of nondiabetic patient values. As a result, no clearly established
threshold is available for diagnostic purposes.
The foregoing is provided for purposes of illustration, explanation, and
description of embodiments of the present invention. Modifications and
adaptations to these embodiments will be apparent to those of ordinary
skill in the art and may be made without departing from the scope or
spirit of the invention.
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