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Description  |
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FIELD OF THE INVENTION
This invention relates to a light coagulation system, particularly a light
coagulating system for treatment of eye disorders.
THE PRIOR ART
Light coagulation, a method developed by medical and optical scientists for
treating certain eye disorders, is gaining increasingly wide acceptance by
the medical profession. In this treatment, an intense beam of light is
focused on the eye, e.g. iris or retina, for a preselected time, to burn,
weld, cauterize, i.e. coagulate the target area, usually a few milimeters
in diameter. Through this method, various eye diseases, such as vascular
diseases, retinal detachment, tumors, diabetic retinopathy and others can
be treated without the need for conventional surgery.
Specifically, in diabetic retinopathy there is caused a proliferation of
new blood vessels in the eye which lead to retina detachment and
blindness. In diabetic retinopathy the blood vessels are cauterized by
light coagulation before they overspread. Light coagulation treats this
condition by cauterizing these vessels and checking the proliferation
thereof.
In conventional light coagulation, a high intensity lamp, usually a Xenon
arc lamp, is positioned in line with a series of lenses, e.g. five or
more, called a condenser, which receives a portion of the light emitted
and converts it to a beam which converges to a focal point and thereafter
diverges.
Another lens, the objective, is positioned to receive the diverging beam
and converts it to a parallel beam. The beam then passes to a mirror where
it is reflected to the desired target area, e.g. the pupil of a patient's
eye. The lens of the eye behind the pupil then focuses the entering beam
to a point of convergence on the retina. The retina is thus treated,
usually for a fraction of a second, then the light beam is cut off. The
operator of the equipment, an M.D. eye specialist, observes and controls
the treatment of the retina by observation through an aperture on the
mirror. See, for example, FIG. 1 herein.
The above treatment, while successful, has in the past required a light
coagulator that is both large and expensive. Some models are as wide as an
office desk and higher and moveable only on wheels. Moreover, the lamps
used in the light coagulators heretofore available have had high power
requirements because, as indicated in FIG. 1, only a fraction of the light
emitted is used, the remainder being wasted.
Because of their power requirements, size, and especially cost, light
coagulators are usually found only in the larger hospitals. Often these
hospitals are many miles from the patient and his doctor's office. The
inconvenience and expense of transferring a patient to a remote hospital
often leads to a delay in the patient receiving needed treatment.
A simplified light coagulator has heretofore not been available and there
is a need and a market for a system that substantially overcomes these
shortcomings. In particular, there is a need for a low cost light
coagulator that is readily available in the office of the local
opthamologist.
There has now been developed a light coagulator that is simpler in
construction, portable, and considerably lower in cost than the above
described system. At the same time, the light coagulator of the invention
is at least as effective as its predecessors.
SUMMARY
Broadly, the present invention provides a light coagulator comprising a
converging light beam source which directs high intensity light to a focal
point and then diverges, an adjustable aperture diaphragm situated at said
focal point for permitting adjustment of the size of the image field in
the desired target area, a lens situated in the path of the diverging
light beam for directing said diverging beam into a parallel light beam,
means for directing said beam to a target area and means for observation
of said target area.
By collimated optical system, as used herein, is meant an optical system
that transforms a beam of light of a certain diameter or size to a
parallel beam of another diameter or size.
DESCRIPTION
The invention will become more apparent from the following detailed
description in which:
FIG. 1 is a schematic view of a light coagulating unit exemplifying the
prior art;
FIG. 2 is a schematic view of a light coagulating unit embodying the
present invention;
FIG. 3 is a block diagram of the power system suitable for powering the
embodiment of FIG. 2.
FIG. 4 is a schematic view of a portion of another embodiment of the light
coagulating unit of the invention;
FIG. 5 is a schematic view of a portion of yet another embodiment of the
light coagulating unit of the invention;
FIG. 6 is a schematic view of a portion of still another embodiment of the
light coagulating unit of the invention;
FIG. 7 is a schematic view of a beam splitter employed in the present
invention; and
FIG. 8 is a schematic view of another beam splitter employed in the present
invention.
Referring now to the drawings, light coagulator 10 has Xenon arc lamp 12
which emits light ray 16 through lenses 20, 22, 24, 26 and 28, i.e. the
condenser, as shown in FIG. 1. At lens 26 at point 30 the ray 16 is
converted to converging beam 32 which is reduced by pupil diaphragm 36 to
convergent beam 34 which has focal point 40 as shown in FIG. 1. Situated
at the focal point 40 is image field diaphragm 38 which permits adjustment
of the size of the image field in the desired target area. From the focal
point 40 the beam 34 inverts and diverges until contacting objective lens
46 which converts beam 34 to parallel beam 44 as illustrated in FIG. 1.
Beam 44 is then reflected to a desired target area by rotatable mirror 48
which has aperture 50 therein for observation of the target area, e.g. the
patient's retina, by the operator and a filter 52 which covers the
aperture 48 and shields the operator's eye from the beam 44 as shown in
FIG. 1. As further shown in FIG. 1, only a fraction of the emitted light
is used by light coagulator 10, that light within the angle .alpha. .
In a considerably more compact unit, light coagulator 54 has lamp unit 56
which includes Xenon arc lamp 58 and paraboloid reflector 60 which is
shaped to direct the major portion of the light emitted therefrom forward
as parallel beam 62, as shown in FIG. 2. Beam 62 passes through pupil
diaphragm 64 and lens 66 where beam 62 is converted to convergent beam 68
having focal point 70 which is surmounted by image field diaphragm 72 as
shown in FIG. 2. At focal point 70, beam 68 inverts and diverges until it
contacts objective lens 74 which converts beam 68 to parallel beam 75 as
shown in FIG. 2. Parallel beam 75 is then reflected off rotatable mirror
76 to the desired target area, the patient's eye 82, having lens 85 and
retina 86. The reflected beam 75 is converted by the lens 85 to convergent
beam 88 which focuses to a small area or point 90 on retina 86. The retina
86 is treated by exposure for a fraction of a second to beam 88, which
quickly heats and coagulates the area 90.
The treatment is observed and controlled by the operator who watches the
treatment of the retina 86 through aperture 78 of mirror 76, filter 80
serving as a shield for the operator's eye 92 as shown in FIG. 2. Lenses
66, diaphragm 72 and lens 74 are referred to herein as the collimated
system of the unit wherein the emitted light beam 62 is reduced in
diameter and considerably intensified. The beam 75 is cut off by pivotably
mounted shutter 63 which when activated quickly swings into position
blocking light beam 62.
Light coagulator 54 is powered as shown in FIG. 3, wherein the input
voltage enters on line 114, is subject to rectification at rectifier and
power control 100, then is passed to filter 102, ignition, system 104 and
thence to the Xenon arc lamp 106. The circuit trigger 110 controls the
timer 96 which is connected via power control driver 98 to rectifier and
power control 100 as shown in FIG. 3. The intensity of the lamp 106 is
controlled and adjusted by the power control 98 shown in FIG. 3.
In addition to the paraboloid reflector described above, other rotationally
symetric concave reflectors can be employed. Thus, in another embodiment
of the invention, lamp 116 is backed by elipsoid reflector 118 which
directs a light beam 120 to a focal point 122, without the need of an
intervening lens, as shown in FIG. 4.
In a further embodiment of the invention, lamp 124 is backed by conoid
reflector 126 which directs beam 128 through first lens 130 which focuses
said beam to focal point 132 as shown in FIG. 5. Shown in phantom in FIG.
5 are other possible light beams 134 and 136 from said lamp reflector and
lens to the prospective focal points 138 and 140. The inner beam 134,
being already convergent, can, of course, dispense with the lens 130 if
desired.
In yet another embodiment of the invention, where the light beam is first
expanded, then reduced, lamp 142 is fronted by convex reflector 144 which
reflects the light back to rotationally symetric concave reflector 146
which directs the light beam 148 forward to lens and/or focal point (not
shown) as shown in FIG. 6.
In addition to apertured rotational mirror 76, other means can be employed
to direct the intensified light beam to the target area, while permitting
observation thereof. Thus, other rotational reflectors can be employed
such as partially transparent beam splitter 150 which directs the greater
portion of the collimated light beam 152 to the patient's eye 154, the
operator 156 observing the treatment through the beam splitter 150 as
shown in FIG. 7. A small portion 158 of the collimated light beam is lost
through the beam splitter 150 as shown in FIG. 7.
In another embodiment partially transparent beam splitter 160 permits the
greater portion of the collimated light 162 to pass therethrough to the
patient's eye 164, the reflected portion of the beam 166 being lost, with
the operator 168 observing the treatment as reflected off the beam
splitter 160 as shown in FIG. 8.
From the above, it can readily be seen that the present invention provides
a novel, efficient, simplified and compact light coagulating unit. More
specifically, the invention provides a novel combination of a convergent
light beam source, a collimated optical system and a rotatable mirror to
direct the resultant light beam to the target area. The invention is
particularly effective for treatment of eye disorders, e.g. iris, retina,
by photo-coagulation of the treated area.
Although other types of lamps can be employed, e.g. the carbon-arc lamp,
such lamp would be overly large and have undesirable spectrum
characteristics compared to the Xenon arc lamps available. The Xenon arc
lamps are of compact size and deliver a light beam of high intensity and
have desirable spectrum characteristics, i.e. have a spectrum more closely
approximating that of the sun. Accordingly, the Xenon arc lamp is
preferred in the practice of the present invention.
As indicated above, various rotationally symetric concave reflectors
backing the lamp can be employed within the present invention including
conoid, elipsoid and paraboloid and optical deformations of conoid by
means known in the art. A convex frontal reflector can be employed as
shown in FIG. 6.
With certain conoid reflectors backing a lamp, e.g. elipsoid, a convergent
beam is projected therefrom and the first lens is dispensed with. With
other conoid reflectors backing a lamp, e.g. as shown in FIGS. 2 and 5,
such first lens renders the beams convergent. Both types of lens systems
are defined herein as a "convergent light beam source".
Of these reflectors preferred are the conoid shapes, particularly elipsoid
and paraboloid. Particularly preferred is a Xenon arc lamp that emits a
parallel beam of light. As indicated in FIG. 2, a lamp having a built-in
paraboloid reflector emits such a parallel beam and utilizes about 80
percent of the light generated by the lamp. Alternatively, a paraboloid
reflector can be separately added to a Xenon arc lamp or other high
intensity lamp to provide a parallel beam of light within the scope of the
present invention.
The addition of a concave reflector to a lamp, whether built-in or
separate, permits the lamp to project a beam and utilizes for light
coagulation more than 80 percent of the light generated by the lamp.
Without such a reflector, only aobut 20 percent of the light generated is
utilized for light coagulation. This is why, in the prior art, extra high
powered lamps have been required to offset the considerable light losses
inherent in the prior systems. Lamps of 1600 watts have been required,
whereas the light coagulator of the present invention can employ a lamp of
150 watts or less, for a reduction ratio of more than 10 to 1.
Because of the reduction of the power requirement, the size and weight of
the light coagulator of the present invention is reduced over the prior
art by a factor of about 5 times.
Moreover, the light coagulator of the present invention can be plugged into
the conventional 110 or 220 volt outlet, where the prior art instruments
have required costly three-phase electrical installation in addition to
its high purchase price.
The purchase price of the light coagulation of the present invention is
reduced over the prior art by a factor of 3 to 5 times. Accordingly, the
light coagulator of the invention is accessible to widespread distribution
in local opthamologists' offices allowing for greater number of patients
to be treated earlier for eye disorders.
The lamp employed can have any power rating sufficient to provide a beam of
the desired intensity. A suitable Xenon arc lamp employed in the present
invention is one rated at 150 watts or less, up to 500 watts or more.
A suitable first lens for the present invention, where required, is a lens
which can direct a beam of light to a focal point or near focal point
(focal zone). Preferred is a lens which can bend a beam of light to a
focal point or near point. Particularly preferred is a lens that can bend
a beam of light to a focal point or zone including the rays at the
infrared end of the spectrum, i.e. a lens that can correct up to the
infrared rays, e.g. the coated achromat lens, which corrects for various
wavelengths so as to focus all colors at the same point or zone, including
the infrared (up to 1000 nanometers).
The objective lens, that lens situated beyond the above described focal
point, is a lens similar to the first, specifically it is a coated
achromat lens. It is preferably positioned so that its focal point
coincides with that of the first lens and it is structured to convert the
rays diverging from the focal point into the resultant parallel beam of
light.
In sum, both lenses are coated to minimize spherical aberrations and
achromatic to correct for chromatic aberrations as discussed above.
The diaphragms are standard available diaphragms in the optical field
having adjustable apertures therein to regulate the light beam sizes as
discussed above. The first diaphragm adjusts the beam size reaching the
patient's pupil. The recommended maximum beam diameter is 8.5 mm to fit
safely inside a fully dilated pupil.
The second diaphragm is positioned at the lenses' focal point and by
adjustment of the aperture thereof, one can adjust the size of the treated
area on the patient's retina at angles, for example of 2.degree. through
3.degree., 4.5.degree. and 6.degree.. This angle is measured at the nodal
point of the eye.
The resultant light beam is aimed to the target area directly as shown in
FIG. 8 or by a rotational reflector including a mirror or partially
transparent beam splitter as described above. The beam splitter can be
constructed of plastic (mylar), glass and preferably coated glass. The
rotatable mirror can be constructed of various reflective materials
including glass and is preferably constructed of 100 percent high
reflectance aluminum for high reflective efficiency.
In the mirror, usually at the center thereof, is a small aperture, about 2
mm, to permit the operator, e.g. an M.D. eye specialist, to observe and
control the treatment of the retina.
The filter is adapted to be positioned over the observation aperture to
protect the observor's eye. The filter can be of tinted glass or plastic,
and preferably is of black glass. The preferred rotational reflector is an
apertured aluminum mirror.
As indicated in FIG. 3, an automatic timer controls the length of treatment
of the beam on the retina. Recommended for most treatments are times of
0.5 seconds or less. However, greater time periods up to 3.0 seconds or
more can be employed where desired.
The following example is presented to illustrate the invention and should
not be construed in limitation thereof.
EXAMPLE I
Portable light coagulators according to the present invention have been
built, tested and used by opthamologists in their offices. The units weigh
only about 50 lbs., operate off the readily available 110 v/220v systems,
and require only a 150 watt Xenon arc lamp. These lamps have successfully
treated eye disorders, including diabetic retinopathy, tumors and have
successfully welded detached retinas back to the choriod of the eye.
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