WO2022260615A1

WO2022260615A1 - A laser cutting device for implementing laser assisted capsulorhexis for cutting a circular opening in the anterior lens capsule

Info

Publication number: WO2022260615A1
Application number: PCT/TR2021/050636
Authority: WO
Inventors: Ebubekir DURMUS
Original assignee: Durmus Ebubekir
Priority date: 2021-06-08
Filing date: 2021-06-22
Publication date: 2022-12-15

Abstract

A laser cutting device for implementing laser assisted capsulorhexis for cutting a circular opening in the anterior lens capsule, characterized by comprising a laser light source of a continuous wave laser or high frequency laser which can be absorbed by unpainted and pigmentless tissues and by intracellular and extracellular water, power control means for adjusting the output energy of the said laser light source for creating ablation by photothermolysis in the anterior lens capsule with a thickness of 14-21 microns, pulse calibration means for ensuring the pulse duration of the laser light source is less than 1 millisecond which is approximately equal to the thermal relaxation time of 20-30 micrometers of water, frequency calibration means for ensuring the frequency of the laser light source of said high frequency laser is in the range of 1 kHz to 15 kHz, in order to make a continuous incision on the anterior lens capsule, control means for regulating the laser beam spot diameter to the smallest spot diameter, preferably to 50 micron, and characterized in that the laser burning pattern consists of adjacent laser spots (2) positioned on a circle or an ellipse, such that the distance (m) between the centers of the two adjacent laser spots (2) is half of one spot diameter, D/2 and two peaks (4) are formed on every half diameter distance in order to ensure a uniform ablation depth and thus achieve a smooth circular incision on the anterior lens capsule.

Description

A LASER CUTTING DEVICE FOR IMPLEMENTING LASER ASSISTED CAPSULORHEXIS FOR CUTTING A CIRCULAR OPENING IN THE ANTERIOR

LENS CAPSULE

Technical Field

This invention relates to a laser cutting device for implementing laser assisted capsulorhexis for cutting a circular opening in the anterior lens capsule.

Background Art

As the closest technical document to our present invention among known technical implementations, we can mention the US patent numbered US 9,579,235 B2 titled “Laser assisted thermal separation of tissue”, the applicant of which is EXCEL-LENS, INC. As mentioned in Claim 1 of this patent document, a circular or elliptical closed curve-shaped opening, that is, an incision, is created in the anterior capsule by applying a laser beam to the anterior lens capsule. Here, a light-absorbing agent, that is, a colorant, is surgically injected onto or inside the lens anterior capsule for the laser to be applied. The 3 main differences between the laser cutting device in accordance with our present invention and the device in US 9,579,235 B2 can be briefly explained as follows: 1) In the present invention, light absorbing agent, i.e. colorant, is not applied to the anterior lens capsule in order to obtain laser incisions, since the laser types used here are selected from laser types that can also have a cutting effect on water and similar transparent materials. Trypan blue or indocyanine green and similar coloring dyes have toxic effects on the corneal endothelium. Since the application of the present invention does not contain coloring dye, the toxic effects of the dye on the corneal endothelium are avoided [1] 2) In order to be able to use laser without applying colorant in a preferred embodiment of the present invention, the types of lasers used are preferably, but not limited to, Nd:YAG laser, Erbium YAG laser and carbon dioxide laser. Whereas, in US 9,579,235 B2 document, there is no restriction on laser types since light absorbing agent, that is, colorant is used. 3) In the laser cutting device according to the present invention, a precise cut is described and planned using a mathematically precisely defined laser burning pattern. However, in the patent document numbered 9,579,235 B2, there is no mathematical description of how the laser spots formed by the laser beams on the organic tissue will be arranged one after the other. The absence of such a description makes the person skilled in the art doubt about the smoothness of the circular or elliptical incision made with the laser.

Below are given some basic information about capsulorhexis.

Capsulorhexis:

Capsulorhexis is one of the most important and difficult stages of cataract surgery. Today, capsulorhexis is applied manually and a certain level of surgical experience and knowledge is required to perform a correct and regular capsulorhexis. We aim to make capsulorhexis a smooth, millimetric, easy and practical clinical application by using appropriate laser energy and technique. In this way, we aim to reduce the complications of cataract surgery, which has become the routine of eye clinics, and to make cataract surgery easier. A regular anterior capsulorhexis is essential for the artificial intraocular lens placed in cataract surgery to take a healthy position in the capsule. It is vital that the capsulorhexis is correct, especially in the implantation of premium lenses, which are popular recently and are known as smart lenses among the people. We hope that application with the device of the present invention will become the gold standard practice in specific cases such as premium lens implantation.

For this purpose, there are various brands of femtosecond phaco devices known as laser cataract surgery among the public [2]. The cost of these devices is quite high. In addition, due to their size, they occupy an additional operating room. Alternatively, the selective laser capsulorhexis device known as the zepto [3] and excel lens [4] has recently emerged. This new product has not yet become widespread in our country and in the world. Capsulorhexis is performed by placing a surgical device inside the eye with Zepto. Here, intraocular manipulation is required, which can cause surgical trauma. In the selective laser capsulorhexis method, an apparatus is added to the operating room microscope and laser capsulorhexis is performed by staining the capsule with trypan blue.

With the present invention, we have produced a new capsulorhexis device that is "paintless and can be applied in a biomicroscope", unlike the known laser capsulorhexis. Since the application will be made without dye, the toxic effects of the dye on the corneal endothelium will be avoided. In addition, the fact that the application is preoperative and can be implemented in the slit lamp microscope will provide great convenience and time savings. With a short and simple laser application in the ward or in the operating room, the patient will be ready for surgery, having completed the capsulorhexis stage, which is an important step of cataract surgery. Since it will save time in clinics with high surgical volume, it will provide important clinical practice.

Some basic concepts in laser technology:

As seen in Figure 2, the laser beam (1) coming from the air (15) to the tissue and the skin (14) enters into various interactions such as reflection (10), absorption (11), transmission (12), dispersion (13). It can pass through tissue (transmission), can disperse in tissue (dispersion), can reflect off tissue (reflection) or it can be absorbed by tissue (absorption).

In order for the laser beam to produce the desired effect on the target tissue, it must be absorbed in that tissue. Chromophores absorb certain wavelengths of laser light. Each tissue can absorb certain laser wavelengths according to the type and amount of chromophore in it. Chromophores for different wavelengths are shown in Figure 2b. In this figure, the absorption graph for water (16), the absorption graph for hemoglobin (17), the absorption graph for melanin (18) and the scatter graph (19) are shown. Absorption data for Hb:Argon, KTP, pulsed dye laser, Diode laser, Nd:YAG laser, CO2 laser, Er:YAG laser are shown here. In the absorption graph for water (16), it is seen that the absorption peaks occur for the CO2 and Er:YAG laser. This shows that Nd:YAG, Er:YAG and CO2 lasers can be used easily in water and similar transparent materials at certain wavelengths.

When the laser beam is absorbed in the tissue, it causes various effects such as photothermal, photoablation, photochemical and photomechanical effects. The photothermal effect is due to the increase in tissue temperature. [5]

42°C, Hyperthermia

60°C, Coagulation

100°C, Evaporation

150°C, Carbonization

Photothermolysis causes tissue removal by evaporation and fume generation (smoke) due to an increase in tissue temperature (100°C-120°C). The photomechanical effect causes disruption of the surrounding tissue with the generation of the shock wave secondary to rapid energy absorption. The photochemical effect is due to the interaction between the laser energy of the photosensitizer and the sensitized tissue. It is known as Photodynamic Therapy (PDT). [5] Photo stimulation effect is used in pain relief and wound healing. To understand the effect of laser on tissue, the basic laser parameters are summarized below.

Energy Flow (Fluence=j/cm2): It is the amount of energy per unit area. Power is a measure of how much energy (in Joules) is transferred per unit time of a second. Thus, 1 Watt of power is equal to 1 Joule of energy delivered in 1 Second exposure time. [6]

Energy Density (irradiance=w/cm2): It is the amount of radiant energy per unit area of a surface. Simply, it is the total amount of light falling on a surface. Energy density indicates the capacity to shear, vaporize and/or coagulate tissue. While it cuts the tissue at high energy density, it acts on the tissue by coagulating the tissue at low energy density. [6]

Spot Size (Beam diameter=mm): The laser spot size is equal to the cross section of the laser light beam. Energy flow and energy density are inversely proportional to the square of the radius of the spot size. [6]

Pulse Duration (ps or ms): Laser light can produce continuous waves or pulse waves in the form of on-off. Pulsed laser allows more selective tissue damage. [6]

Thermal Relaxation Time (TRT): The tissue exposed to the laser starts to cool after a while by spreading its energy to the surrounding tissue. This is called the thermal relaxation time. In order for the laser energy to be effective in the tissue, it must be of sufficient energy and the exposure of the tissue to the laser must be shorter than the thermal relaxation time. Otherwise, undesirable damage may develop in the neighboring tissues, as heat energy will spread to the environment. Although the thermal relaxation time of each tissue is different, when the tissue is exposed to laser in a shorter time than this time, heat energy will not spread to the surrounding tissues, so there will be no damage to the surrounding tissues or it will be at a minimal level. [6]

Lens Capsule:

The lens capsule is an elastic and transparent basement membrane lined by epithelial cells and composed of type 4 collagen. Figure 3a illustrates the anatomical position of the lens in the eye. Here, the lens (5), cornea (6) and retina (7) parts of the eye are seen. Also, Figure 3b shows the thickness of the lens capsule in different regions. The thickness of the anterior lens capsule (8) is 14-21 microns, and the thickness of the posterior lens capsule (9) is 4 microns. Capsulorhexis is a continuous circular incision created by the cataract surgeon on the anterior surface of the lens capsule to allow cataract removal of the lens that has lost its transparency. Figures 4a and 4b illustrate manual capsulorhexis application on the lens. Here, the circular lens capsule incision (3) made with a cutting handpiece is seen.

SUMMARY OF THE INVENTION

A laser cutting device for implementing laser assisted capsulorhexis for cutting a circular opening in the anterior lens capsule comprises: a laser light source of a continuous wave laser or high frequency laser which can be absorbed by unpainted and pigmentless tissues and by intracellular and extracellular water, power control means for adjusting the output energy of the said laser light source for creating ablation by photothermolysis in the anterior lens capsule with a thickness of 14-21 microns, pulse calibration means for ensuring the pulse duration of the laser light source is less than 1 millisecond which is approximately equal to the thermal relaxation time of 20-30 micrometers of water, frequency calibration means for ensuring the frequency of the laser light source of said high frequency laser is in the range of 1 kHz to 15 kHz, in order to make a continuous incision on the anterior lens capsule, control means for regulating the laser beam spot diameter to the smallest spot diameter, preferably to 50 micron, and the laser burning pattern consists of adjacent laser spots positioned on a circle or an ellipse, such that the distance (m) between the centers of the two adjacent laser spots is half of one spot diameter, D/2 and two peaks are formed on every half diameter distance in order to ensure a uniform ablation depth and thus achieve a smooth circular incision on the anterior lens capsule.

DESCRIPTION OF FIGURES

Figure 1 shows the laser burning pattern of the laser cutting device according to the present invention,

Figure 2a illustrates the interaction of laser beams after contact with tissue,

Figure 2b illustrates the absorption-wavelength graphs of various laser types in different environments,

Figure 3a illustrates the anatomical position of the lens inside the eye,

Figure 3b illustrates the thickness of the lens capsule in different regions.

Figures 4a and 4b illustrate manual capsulorhexis application on the lens. REFERENCES

1 Laser beam

2 Laser spot

3 Lens capsule incision

4 Two peaks

5 Lens

6 Cornea

7 Retina

8 Thickness of the anterior lens capsule

9 Thickness of the posterior lens capsule

10 Reflection

11 Absorption

12 Transmission

13 Dispersion

14 Skin

15 Air

16 Absorption graph for water

17 Absorption graph for hemoglobin

18 Absorption graph for melanin

19 Scatter graph m Distance between the centers of the two adjacent laser spots D: Spot diameter

DETAILED DESCRIPTION OF THE INVENTION

With the present invention, a laser cutting device for implementing laser assisted capsulorhexis for cutting a circular opening in the anterior lens capsule is provided. As seen in Figures 1 to 4, a laser cutting device according to the present invention, comprises: a laser light source of a continuous wave laser or high frequency laser which can be absorbed by unpainted and pigmentless tissues and by intracellular and extracellular water, power control means for adjusting the output energy of the said laser light source for creating ablation by photothermolysis in the anterior lens capsule with a thickness of 14-21 microns, pulse calibration means for ensuring the pulse duration of the laser light source is less than 1 millisecond which is approximately equal to the thermal relaxation time of 20-30 micrometers of water, frequency calibration means for ensuring the frequency of the laser light source of said high frequency laser is in the range of 1 kHz to 15 kHz, in order to make a continuous incision on the anterior lens capsule, control means for regulating the laser beam spot diameter to the smallest spot diameter, preferably to 50 micron, and the laser burning pattern consists of adjacent laser spots (2) positioned on a circle or an ellipse, such that the distance (m) between the centers of the two adjacent laser spots (2) is half of one spot diameter, D/2 and two peaks (4) are formed on every half diameter distance in order to ensure a uniform ablation depth and thus achieve a smooth circular incision on the anterior lens capsule.

Furthermore, the laser cutting device according to the present invention comprises a fixation apparatus for fixing said laser cutting device to a biomicroscope.

In a preferred embodiment of a laser cutting device according to the present invention, said laser light source is preferably selected from, but not limited to, Nd:YAG laser, Erbium YAG laser or carbon dioxide laser.

Application of the present invention:

Laser capsulorhexis:

With the present invention, we want to do the application without dye and on the biomicroscope, unlike the recently released zepto and excel lens. Since we will perform the application on dye-free and pigment-free tissue, we use laser types that absorb water, such as Nd: Yag laser, Erbium YAG laser or carbon dioxide laser. Our aim is to achieve circular, well-circumscribed capsulorhexis by creating ablation in the anterior lens capsule of 14-21 micron thickness by selective photothermolysis.

Application parameters of the laser cutting device according to the present invention: Pattern: An ideal capsulorhexis is well-circumscribed, 5 mm in diameter, ring-shaped. In order to ensure uninterrupted capsule incision, the spot diameters will overlap, right in the middle and the pattern will be in the form of a circular ring. [5]. As shown in Figure 1, two peaks (4) (energy profiles of two adjacent spots overlapping at half-spots) formed due to the distance between one half of the spot diameter and the diameter of the adjacent spot provide a uniform depth of ablation. Here, the laser beam (1) creates various laser spots (2) on living tissue in bundles.

Spot Diameter: We prefer the laser spot (2) to have the smallest spot diameter we can make, preferably 50 micron spot diameter.

Frequency: Since we will make continuous incisions in the capsule, the laser must be continuous without interruption. The tissue responds to the laser at a frequency of 15,000 pulses per second as if it were continuous. [7] Therefore, a continuous wave laser or a pulse mode laser (frequency in the range of 1 kHz to 15 kHz per second) will be preferred. Duration: It is reported in the literature that the thermal relaxation time of 20-30 micrometer water absorbing the carbon dioxide laser is less than 1 millisecond. [7] For this purpose, we aim to have the pulse duration shorter than 1 millisecond at the level of microseconds or nanoseconds. Therefore, when the tissue is exposed to high laser energy for a very short time, which is shorter than the thermal relaxation time, effective photothermolysis can be achieved in the target tissue without damaging the surrounding tissue.

Energy: The tissue to which we will apply the laser is the anterior capsule of the eye lens and is approximately 14-21 microns thick. The amount of energy that will create ablation with photothermolysis in the anterior capsule can be adjusted, and we think that 1-10 mJ of energy will be sufficient, with an average of 3-4 mJ intervals. In the Yag capsulotomy we apply in clinical practice, the posterior capsule of the lens can be fragmented with approximately 3-4 mJ [8].

Power Source: Nd: Yag laser, Erbium YAG laser or carbon dioxide laser, which can absorb intracellular and extracellular water, will be preferred as the power source, since the application will be made in dye-free and pigment-free tissue.

Possible undesirable side effects in application:

As the laser beam is absorbed in the target tissue, it can cause unwanted side effects in neighboring tissues through reflection, thermal diffusion and scattering. In order to minimize undesirable side effects, first of all, the laser wavelength suitable for the dominant chromophore in the target tissue should be selected. The effect of the laser beam on the tissue can be controlled by providing a combination of laser parameters such as power setting, duration, spot size, focusing and application mode. [9] If the laser beam has a high enough power density and short pulse duration for the target effect, all the energy will be instantly absorbed and very little dispersed within the tissue. The superpulse and ultrapulse modes have high peak power with short pulse duration and therefore minimal scattering in the tissue. Because the duration of the peak energy is shorter than the thermal relaxation time, so there is no diffusion, all the heat is used for photothermolysis in the target tissue. In addition, the sharply focused laser beam with the contact lens has maximum energy and instantly evaporates the water at the point of impact, causing photoablation of the tissue. [9]

If the tissue is rich in water, the dispersion of the laser beam within the tissue will be less because water is the chromophore for laser energy and all incoming energy will be completely absorbed. Scattering will only occur when the water in the tissue at the point of impact is depleted. Since water is the only chromophore for the Nd:Yag laser, Erbium YAG laser or carbon dioxide laser and instantly absorbs any thermal diffusion, it minimizes undesirable side effects. The presence of aqueous fluid in the anterior chamber acts as a heat sink, acting as a type of hydrodissection, removing excess heat from the laser. The presence of aqueous fluid in the anterior chamber has the additional advantage of preventing damage to the surrounding tissue. [9]

Clinical Practice Examples:

Medical laser applications are mostly used in dermatology and eye diseases clinical practices. There are laser applications that are preferred for different purposes in pigmented and non-pigmented tissues. In deep sclerectomy surgery applied in the treatment of glaucoma, thermolysis (melting) is performed in the sclera tissue (similar to cartilage tissue) with carbon dioxide and erbium YAG laser. [10] There are also studies in which corneal ablation is performed with erbium and nd YAG lasers. [11] The tissue to which we will apply laser to create capsulorhexis is the anterior capsule of the eye lens and is approximately 14-21 microns thick. For this purpose, we think that 1-10 millijoules of energy will be sufficient. In the Yag capsulotomy we apply in clinical practice, the posterior capsule of the lens can be fragmented with approximately 3-4 millijoules [8]. Citation List:

[1] Nagashima T, Yuda K, Hayashi T. Comparison of trypan blue and Brilliant. Blue G for staining of the anterior lens capsule during cataract surgery: short-term results.

International ophthalmology. 2019;39(l):33-9.

[2] Abell RG, Davies PE, Phelan D, Goemann K, McPherson ZE, Vote BJ. Anterior capsulotomy integrity after femtosecond laser-assisted cataract surgery. Ophthalmology. 2014;121(l):17-24.

[3] Chang DF. Zepto precision pulse capsulotomy: a new automated and disposable capsulotomy technology. Indian journal of ophthalmology. 2017;65(12): 1411.

[4] Stodulka P, Packard R, Mordaunt D. Efficacy and safety of a new selective laser device to create anterior capsulotomies in cataract patients. Journal of Cataract & Refractive Surgery. 2019;45(5):601-7.

[5] ATA§ M. Oftalmolojide lazerler. Ankara: Anadolu Trp Kitapevi; 2020. 71-2,102 p.

[6] Koc E, Dinger D. Lazere Giri§ ve Genel Bilgiler. Archives of the Turkish Dermatology & Venerology/Turkderm. 2012;46.

[7] Herd RM, Dover JS, Arndt KA. Basic laser principles. Dermatologic clinics.

1997 ;15(3):355-72.

[8] Min JK, An JH, Yim JH. A new technique for Nd: YAG laser posterior capsulotomy. International journal of ophthalmology. 2014;7(2):345.

[9] Laser physics [Internet].

[10] Klink T, Schlunck G, Lieb W, Klink J, Grehn F. C02, excimer and erbium: YAG laser in deep sclerectomy. Ophthalmologica. 2008;222(2):74-80.

[11] Telfair WB, Bekker C, Hoffman HJ, Yoder PR, Nordquist RE, Eiferman RA, et al. Histological comparison of corneal ablation with Er: YAG laser, Nd: YAG optical parametric oscillator, and excimer laser. Slack Incorporated Thorofare, NJ; 2000.

Claims

1) A laser cutting device for implementing laser assisted capsulorhexis for cutting a circular opening in the anterior lens capsule, characterized by comprising

- a laser light source of a continuous wave laser or high frequency laser which can be absorbed by unpainted and pigmentless tissues and by intracellular and extracellular water,

- power control means for adjusting the output energy of the said laser light source for creating ablation by photothermolysis in the anterior lens capsule with a thickness of 14-21 microns,

- pulse calibration means for ensuring the pulse duration of the laser light source is less than 1 millisecond which is approximately equal to the thermal relaxation time of 20- 30 micrometers of water,

- frequency calibration means for ensuring the frequency of the laser light source of said high frequency laser is in the range of 1 kHz to 15 kHz, in order to make a continuous incision on the anterior lens capsule,

- control means for regulating the laser beam spot diameter to the smallest spot diameter, preferably to 50 micron, and characterized in that the laser burning pattern consists of adjacent laser spots (2) positioned on a circle or an ellipse, such that the distance (m) between the centers of the two adjacent laser spots (2) is half of one spot diameter, D/2 and two peaks (4) are formed on every half diameter distance in order to ensure a uniform ablation depth and thus achieve a smooth circular incision on the anterior lens capsule.

2) A laser cutting device for implementing laser assisted capsulorhexis for cutting a circular opening in the anterior lens capsule, characterized in that it comprises a fixation apparatus for fixing said laser cutting device to a biomicroscope.

3) A laser cutting device for implementing laser assisted capsulorhexis for cutting a circular opening in the anterior lens capsule, characterized in that said laser light source is selected from Nd:YAG laser, Erbium YAG laser or carbon dioxide laser.