Patent Application
20230218166
The present invention relates to the technical field of medical equipment, in particular to an ophthalmic portable laser slit lamp and a method of eye inspection.
In ophthalmology, optically reflected corneal images are commonly used as a diagnostic tool to identify various eye diseases. The conventional LED and halogen slit lamp microscope is a conventional ophthalmic optical inspection tool. It enables the doctor to observe the superficial lesions of the human eye, but also can clearly show the lesions in the deep tissues of the eyes. With the aid of the slit image, structures and layers in the eye can be better recognized during diagnostic and surgical procedures. Surgical slit lamps are used for the most part in combination with a surgical microscope in intraocular and especially in retinal surgery. By means of the illuminated field on the retina, membranes that have become diseased, which are very thin but nevertheless greatly reduce the patient's sight, can be detected early and successfully operated on.
Most existing slit lamps are relatively bulky, and are usually fixed indoors for eye examination, being inconvenient to carry, and having a limited application range. Surgical slit lamps of this kind are on the market, for example, under the name “Leica® Slit Illuminator,” and are described in Leica® web page www.Leica-microsystems.com/products/surgical-microscopes/p/leica-m822-f20/gallery/
Other existing surgical slit lamps such as (i) Ray Vision® portable slit lamp (www.lunar-health.com) or (ii) Digital Eye center® S150 Ultra Potable Slit Lamp® (https://www.digitaleyecenter.com/product/ultra-portable-slit-lamp-s150/) are portable but show the following disadvantages: a. they use conventional LEDs for light generation instead of laser diodes, b. they lack of a fixed focus, c. they comprise no internal safety timers and d. they lack of a fixed slit.
Document CN 208610812 discloses a pen type slit lamp with magnifying glass for the eye examination, and a casing upper end connected with a volume bracket that is used for holding the patient's forehead. The lighting system has a slit for emitting light to the patient's eye. The magnifying glass is used for observing the patient's eye on the casing. The pen type slit lamp magnifying glass has five kinds of light fence pieces available, for providing omni-directional inspection. However, the document fails to describe the main features of the present invention, namely, it uses a conventional LED for light generation instead of a laser diode. Also its focus is not fixed; it does not comprise internal safety timer and its slit is not fixed; all of these features being essential for assuring safety for the patient's eye.
Document U.S. Pat. No. 8,277,047 B2 describes an illumination unit for the generation of optical sectional images in transparent media, particularly in the eye. In the arrangement, the low-divergence beams emitted by a laser serving as illumination source are imaged on or in the eye under examination by a reflection element which is controllable in a defined manner and beam deflection elements present in the beam path. The optical sectional images resulting in and on the eye can be observed and/or recorded, further processed and evaluated with an image processing unit in a known manner. In the solution according to the document, a sectional image is generated by the deliberate periodic beam deflection of a particularly fine laser beam with high depth of focus, which sectional image remains sharp through the entire dimension of the object to be examined and makes possible an improved evaluation. The intensity of the laser beam bundle can be varied in such a way that it is sufficient for observation and documentation, but so that the diameter of the beam bundle is fine enough for a high detail resolution. However, the unit of the cited document is not portable. It is mainly designed for carrying out surgical incisions in a sterilized environment and it has to be used together with a surgical microscope that amplifies the image by means of its slit lamp binoculars. Also, due to the way it is used, the unit comprises no internal safety timer.
Document U.S. Pat. No. 7,724,429 B2 relates to a microscope (10) having an illumination apparatus (26) having a light source (1) and an optical system. The light source (1) is embodied to output a coherent light beam bundle along a defined illumination beam path (2a), and the optical system in the illumination beam path (2a) encompasses a spatial light modulator (3) for modifying the illuminated field (4). A surgical microscope (10) is preferably equipped with an illumination apparatus (26) of this kind that is arranged adjustably in two directions on the surgical microscope (10). However, the unit of the cited document is not portable and, unlike the present invention, it cannot be used with any other microscope. Also, due to the way it is used, the unit comprises no internal safety timer.
Document US describes a laser collimator that includes an optical lens having an optical axis; a sliding lens holder for housing the lens having a longitudinal opening parallel to the optical axis; a stationary lens holder ring for fitting to the front of the sliding lens holder and having a protruding key for receiving the longitudinal opening; and a focusing ring movable along the optical axis, wherein the protruding key placed within the longitudinal opening prevents the sliding lens holder from rotating. However, the document is aimed to another usage, namely for geometric alignment of telescope focusing and, since it is not to be aimed into an eye, it includes no safety timer.
Document US20150085254 describes methods and apparatuses for a micro-display based slit lamp illumination system. A first optical element is configured to generate a micro-display image including an illuminated area. A second optical element is configured to receive the micro-display image, and focus the micro-display image upon an eye to be examined, wherein light is reflected from the eye as a result of the illuminated area. However, the principles of the cited document are different from those of the present invention which does not generate an illuminated are but a fine light line instead. Also, the apparatus of the cited document is not portable and does not comprise an internal safety timer.
Therefore, since the known non-portable slit lamps use halogen lamps and the known portable slit lamps use LEDs, it is apparent that none of the prior art slit lamps (portable or desk-type) use laser diodes for generating the required light for a correct eye inspection. Through medical practice has proven that laser light has better illuminating power than halogen and conventional LEDs in this field and is much less damaging to the eye.
Also, none of the prior art documents mention the use of safety feature such as an internal safety timer that will set a time limit to laser exposure of the eye. Also, none of the prior art documents mentions or suggests that the focus is fixed and that the slit is fixed (not capable of being broadened) which guarantees a very detailed vision of the surgical defects.
The technical problem mainly solved by the present invention is to provide a safe portable laser slit lamp that overcomes the above-mentioned drawbacks in the prior art and a method of eye inspection using the new laser slit lamp.
In order to solve the above technical problem of the state of the art, the technical solution offered by the present invention is to provide an ophthalmic portable laser slit lamp for ophthalmic examination and a method of eye inspection. The device comprises a portable housing containing an electronic timer circuit, a rechargeable battery, a laser module containing a laser emitting diode, a fixed focusing lens that sets the appropriate focal distance for the examination method and a line generator lens acting as a slit aperture. The laser beam aimed to the eye of the patient illuminates the eye with a very thin straight laser line at a fixed focal distance. The device also comprises a safety timer circuit that protects the patient's eye against irradiation overload. The method of the invention allows the surgeon to detect surgical eye disorders at the operating room and helps to carry out a correct diagnosis in a much more precise and effective way than any light or laser spot device.
The preferred embodiments of the present invention are described in detail below with reference to the enclosed drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art.
The present invention provides a portable laser slit lamp, which is used for ophthalmic examination, having a small size, light weight, convenient simple operation, and low cost.
Referring to
In this embodiment, the power source is preferably a 3.7 VDC (1000 mAH) rechargeable battery 6A, which is convenient for replacement.
The operation of the timer and control board 6 is based on integrated circuit 555. It was configured as a monostable multivibrator in order to obtain a programmable delay to control the emission of laser light. The IC 555 timer is an integrated circuit that is used in the generation of timers, pulses and oscillations. The IC 555 can be used to provide time delays, as an oscillator, and as a flip flop chip. Its derivatives provide up to four synchronization circuits in a single package. When used as a monostable multivibrator the circuit delivers a single pulse of a width set by the designer, thus supplying the possibility of setting a programmable delay.
The power supply of device based on rechargeable battery 6A is controlled by S2 slide switch. When S2 is slid to ON position the status red LED turns on indicating that the system is energized and ready to use. Push button S1 is in charge of sending laser activation signal to the timer and control board.
The trigger signal of the 555 integrated circuit 7 is set to high level through pull up resistor R18; once S1 push button is pressed the signal changes to a low level state. The logic of the integrated circuit 7 reacts to this change of state sending to the output an activation pulse of predetermined duration.
The duration of the activation pulse is determined by discharge time of capacitive-resistive circuit and is given by the following equation T=ln (3)*R2*C2. In this case, values of electronic components R28 and C29 were selected in order to obtain a time delay of 60 seconds Finally, laser activation signal is sent to Q1 transistor 10 in order to adapt power level to manage the load that is connected to jumper JP313, namely the electric consumption of the laser diode module 5.
The illumination laser source is a laser diode module 5 supplied by third parties with the following specifications:
Laser module 5 comprises a heat dissipation housing 15 that contains the laser diode control board 16, a semiconductor laser diode 17, a fixed focusing lens 19 and a line generator lens 20.
Once the device is activated, the physician must carefully aim the laser straight line forming an angle of 30° to 50°, but not greater to avoid interfering the light with his hand. Also, keeping the angle between 30° and 50°, the laser light will not touch the macula, which is the most sensitive area of the retina. The timer comprised in the device will keep the eye exposure to laser impingement well below safety periods. A period of 60 seconds should be considered a maximum time limit for this exposure. The color of the laser beam can be violet, green or red, but the latter is the one best suited for visualizing abnormalities and it has proven to be less damaging for the eye.
Using a laser straight line for inspecting the eye instead of using a small circular LED or halogen spot is the heart of the present invention and has shown to have great advantages such as:
In another aspect the present invention comprises a method of eye inspection which is based on the usage of the device of the present invention. In a preferred embodiment the method may comprise a method for detecting surgical ophthalmic abnormalities.
In a first preferred embodiment, the method of the present invention for detecting surgical ophthalmic abnormalities comprises scroll positioning verification (correct placement of the donor graft) during DMEK (Descemet membrane endotheilial kerastoplasty) surgery using the device of the present invention after using an eye inspection microscope.
The method comprises the following steps after turning off the microscope and ambient lights:
Steps a and b are quite straightforward. However, when the device is turned on in step a, the safety timer is automatically activated and this is one of the novel features of the present invention since it guarantees that the patient's eye is protected against irradiation overload.
Step c comprises forming an angle of 30° to 50° with the laser beam respect of a line which is perpendicular to the plane of the eye, but not greater, to avoid interfering the light with the surgeon's hand.
Step d is essential when projecting a laser light line inside the eye. DMEK surgery is a laminar corneal graft operation in which only Descemet's membrane and endothelium are replaced. During this procedure, at the moment of implantation and injection of the donor graft, the graft takes a double scroll shape. The graft scrolling in DMEK surgery refers to the tendency that donor eye tissues have, for being usually very thin, to naturally roll-up over themselves, with the endothelial at the outer side. Therefore, it is very important to check the orientation of donor tissue in order to keep the cornea structure unchanged and avoid reversing the order of cornea layers. If this issue is detected, the surgeon must change the orientation of the donor tissue, otherwise the scroll being oriented upside down will result in a transplant failure.
The endothelium must be in contact with aqueous humor and, therefore, if the scroll is attached upside down (e.g. the endothelium in touch with the stroma instead of the aqueous humor) it will detach in 3 days and the transplant will surely fail.
Other real life cases testing the device in action and in relation to the correct scrolling may be seen in the following figures:
Once the scroll positioning is verified the surgeon can further inspect the status of the patient's eye.
Step f is the beneficial result of using a laser light line instead of a laser light dot. This difference is the main core of the present invention and can be clearly understood when looking the photos of
The laser device of the present invention provides a high quality and detail level image of the cornea that allows the surgeon to differentiate the layers of ocular tissue in order to confirm the attachment or detachment of the donor graft. The donor graft is completely attached when no gap is seen between the posterior stroma and the donor tissue. If a gap is present the surgeon can confirm the detachment and this can only be clearly seen if the area is illuminated with a laser light line but not with a light or laser dot.
The present invention can also be applied to other surgical ophthalmic checks which do not imply donor tissue grafting. In these applications the method consists of the following steps after turning off the microscope and ambient lights:
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/028728 | 4/17/2020 | WO |
