RU2749301C1 - Method for calculating parameters of selective micro-pulse mode on navilas 577 laser system, taking into account return and type of appearance on fitzpatrick scale - Google Patents

Abstract

FIELD: medicine; ophthalmology.SUBSTANCE: to select the parameters of the selective micro-pulse mode on the Navilas 577s navigation laser system (hereinafter – Navilas 577s NLS), when the pathological process is localized in the foveal avascular zone, a micro-pulse mode with a selective effect on the retinal pigment epithelium is selected, taking into account the technical characteristics of the Navilas 577s NLS: the micro-pulse duration is 50-100 mcs, the interval between pulses is 2000 mcs, the duty cycle is 2.4-4.8%, the pulse packet duration is 10 ms, the number of pulses per packet is 5, the spot diameter is 100 mcm, power is from 0.4 to 1.9 W, the wavelength is 577 nm. The laser power is calculated according to the original calculation formula, taking into account the age and type of appearance on the Fitzpatrick scale. At an estimated power of 1.9 W and below, the value of the estimated power is rounded up to tenths and treatment is performed with this power and micro-pulse duration of 50 mcs. With an estimated power of 1.91 to 2.28 W, the resulting power value is multiplied by 5/6 and rounded up to tenths and used for treatment with micro-pulse duration of 60 mcs. With an estimated power of 2.29 to 2.66 W, the resulting power value is multiplied by 5/7 and rounded up to tenths and used for treatment with micro-pulse duration of 70 mcs. With an estimated power of 2.67 to 2.7 W, the resulting power value is multiplied by 5/8 and rounded up to tenths and used for treatment with micro-pulse duration of 80 mcs. The obtained values of the power and the micro-pulse duration for the selective micro-pulse mode are set in the Navilas 577s NLS and treatment is performed.EFFECT: method reduces the time for selecting the necessary parameters for treatment in the avascular zone of the retina and reduces retinal damage due to determining individual parameters for treatment for each patient, which will lead to the adhesion of retinal pigment epithelium and neuroepithelium detachment, resorption of edema and subretinal fluid, resorption of drusus, reduction of the central height of the retina, restoration of visual acuity and photosensitivity.1 cl, 4 ex

Description

The invention relates to medicine, namely to ophthalmology, and is intended for the individual calculation of the parameters of the micro-pulse mode with a selective effect on the retinal pigment epithelium (RPE), according to the formula taking into account the age and type of appearance for treatment in the foveal avascular zone on the navigation laser Navilas 577s (NLU Navilas 577s).

Currently, the micropulse mode of laser radiation is widely used in the treatment of various diseases of the fundus. Depending on the selected parameters, a different degree of effect on the retina is achieved. The main purpose of using the micropulse mode in clinical practice is to reduce damage to eye tissue, which is especially important in the treatment of various diseases with localization in the foveal avascular zone. The key feature of the micropulse mode, in contrast to continuous laser radiation, is the ability to selectively influence the RPE, but this requires the correct selection of energy parameters (Zheltov GI, Glazkov VN, Ivanova EV. Selective action of laser pulses on the retinal pigment epithelium. Physical basics ARS-MEDICA 2012; 58 (3): 78-85 Volodin PL, Ivanova EV Computer simulation of laser action in the regime of single micropulse and reactions of proteins chorioretinal complex for selective and effective action on the retinal pigment epithelium cells . Laser Medicine. 2018; 1: 61-66).

An important role in the development of many diseases of the central retinal zone belongs to defects in the RPE layer with impaired barrier and pumping functions. Therefore, the modern method of treatment should be aimed at effective restoration of the external hematoretinal barrier, without causing unnecessary damage to the adjacent tissues. Therefore, in some diseases of the macular zone (acute and chronic central serous chorioretinopathy, macular edema of various etiologies, some forms of age-related macular degeneration), in order to achieve a clinical effect, it is necessary to target RPE, damage to the sensorineural retina is a negative consequence of treatment.

For selective damage to RPE and keeping the neuroepithelium and choroid intact, more stringent conditions are required for the selection of parameters. Deviations can lead to unwanted damage to adjacent structures, which is especially dangerous for treatment in the foveal avascular zone, or will not give the desired effect. Therefore, selective treatment can be implemented only in a narrow "window" of parameters. Available commercial lasers have different specifications from each other. Micropulse modes differ in a number of parameters: power, number of pulses in a packet, pulse duration and interval between them. Consequently, the selection of parameters for selective action on RPE with minimal damage to adjacent structures must be carried out taking into account the technical capabilities of the laser system.

In clinical practice, a laser unit with NLU Navilas 577s is used to treat diseases of the central zone of the retina using a micropulse mode. Thanks to the navigation system, a targeted, clear and topographically oriented effect on the pathological focus occurs without affecting the surrounding tissues. With the help of computer simulation, the parameters of a selective and effective micropulse mode have been determined, which have been successfully introduced into clinical practice. However, the same regimens cannot be used to treat all patients. The use of energy parameters not sufficient to damage RPE will not lead to a clinical effect. Performing the treatment with an energy above the threshold will damage the neurosensory retina and choroid. Therefore, taking into account the individual characteristics of each patient, it is preferable to test before treatment and select the power at which the effect on RP is achieved.

The closest analogue is the RF patent for invention No. 2669858 "Method of individual selection of energy parameters of a micropulse mode on a Navilas 577s laser (NLU Navilas 577s)". In the present invention, before treatment, a micro-pulse mode is tested and the parameters with the lowest power are selected for the treatment, at which the laser applications are detected by the autofluorescence method. The disadvantage of this method is the need for preliminary testing to take into account individual characteristics. Before applying test laser applications, autofluorescence is performed to determine the test areas. The laser then creates a plan and tests, which often take longer than the treatment. After 1-2 hours after testing, a second study of autofluorescence is carried out to select the optimal parameters for treatment. Treatment is performed only after determining the minimum parameters at which RPE damage is observed. Thus, the individual selection of the parameters of the selective micropulse mode significantly increases the time, complexity and cost of treatment.

The objective of the invention is to create a formula, taking into account the age and type of appearance on the Fitzpatrick scale, for the individual selection of the energy parameters of the micropulse mode with a selective effect on RP on the Navilas 577s NLU for laser treatment in the foveal avascular zone.

The technical result of the proposed method is the calculation according to the formula of the parameters of a micropulse mode with a selective effect on RPE, taking into account the age and type of appearance on the Fitzpatrick scale, without preliminary testing, performing autofluorescence to assess the test results and determine the threshold damage to RPE, which will reduce damage to the retina, significantly reduce the time of selection of the necessary parameters for treatment in the avascular zone, which will lead to adherence of RPE and neuroepithelium detachment, resorption of edema and subretinal fluid, resorption of druses, decrease in the central height of the retina, restoration of visual acuity and photosensitivity.

The technical result is achieved by the fact that in the method for calculating the parameters of the micropulse mode on the NLU Navilas 577s for selective exposure to RP using the formula taking into account the age and type of appearance on the Fitzpatrick scale, which consists in the fact that in order to determine the individual energy parameters required for treatment, preliminary carry out computer modeling by solving the heat conduction equation and applying the Arrhenius integral and determine the micropulse mode, taking into account the technical characteristics of the Navilas 577s NLU, in which a selective effect on the RPE is realized and high selectivity values are maintained, with the parameters: the duration of the micropulse is 50-100 μs, the interval between pulses -2000 μs, duty cycle - 2.4-4.8%, pulse packet duration - 10 ms, number of pulses in a packet - 5, spot diameter - 100 μm, power - from 0.4 to 1.9 W, length wavelength - 577 nm, then based on the results of testing the micropulse mode (for a long time micropulse rate - 50 μs, pulse interval - 2000 μs, duty cycle - 2.4%, micro-pulse packet duration - 10 ms, number of pulses in a packet - 5, spot diameter - 100 μm, power - from 0.4 to 1, 9 W, wavelength - 577 nm) with a selective and effective effect on RP, carried out on patients aged 30-65 years and 1-4 types of appearance on the Fitzpatrick scale and determination of laser applications with different powers on autofluorescence images (488 nm) with a probability visualization 90%, found that the probability of visualization 90% is a function of 3 variables (power, age, type of appearance on the Fitzpatrick scale) with 4 free parameters (P1-P4), and in form is a logistic function over a linear expression of arguments, that is logistic regression,

Where P (1-4) are the parameters to be adjusted.

P1 is the scale factor, which is responsible for the width in the central part of the logistic function.

P2 - coefficient of influence of age

Р3 - coefficient of influence of the type of appearance

P4 - constant

Based on the results of testing the micropulse mode on patients aged 30 to 65 years with 1-4 types of appearance according to the Fitzpatrick scale, we selected a logistic regression using the method of maximizing the likelihood function on the training sample, for this, 4 free indicators (P1-P4) were fitted for 3 arguments (power, age and type of appearance on the Fitzpatrick scale),

From Equation 2, we obtain the inverse function for determining the power at which RPE damage is achieved according to autofluorescence data with a probability of 90% (Equation 3).

Appearance type on the Fitzpatrick scale + 1.65, which after transformation takes the form:

Considering that logistic regression was selected on patients aged 30 to 65 years with 1-4 types of appearance on the Fitzpatrick scale, the formula (equation 3) is not applicable for ages under 30 and over 65 years old, as well as for 5-6 types of appearance according to the Fitzpatrick scale. Fitzpatrick scale, with a calculated power value of 1.9 W and below, the power value is rounded up to tenths and treatment is carried out with this power and a micropulse duration of 50 μs; with a calculated power value of more than 1.9 W, it is required to reduce the power and increase the duration proportionally micropulse, so that the energy of the laser action remains the same, taking into account that on the Navilas 577s NLU it is possible to set the duration of the micropulse with a step of 10 μs, and the power is 1.9 W and below, therefore, for each power range, which are calculated by the formula, the correction was calculated proportionality factor for the corresponding micropulse duration, with a calculated power from 1.91 to 2.28 W, the resulting value the power is multiplied by 5/6 and rounded up to tenths, a micropulse duration of 60 μs is used, with a calculated power from 2.29 W to 2.66 W, the resulting power value is multiplied by 5/7 and rounded up to tenths , apply a micropulse duration of 70 μs, with a calculated power of 2.67 to 2.7 W, the resulting power value is multiplied by 5/8 and rounded up to tenths, a micropulse duration of 80 μs is used, the obtained values of the power and micropulse duration for selective micropulse mode is installed in the NLU Navilas 577s and treatment is carried out.

The method is carried out as follows.

For laser treatment of various diseases, with the localization of the pathological process in the foveal avascular zone, a micropulse mode with a selective effect on RPE is selected taking into account the technical characteristics of the Navilas 577s NLU with parameters (duration of a micropulse - 50-100 μs, interval between pulses - 2000 μs, duty cycle - 2.4-4.8%, the duration of the micropulse packet is 10 ms, the number of pulses in the packet is 5, the spot diameter is 100 microns, the power is from 0.4 to 1.9 W, the wavelength is 577 nm). For each patient, the type of appearance is determined according to the Fitzpatrick scale based on external signs (skin, eye and hair color). Fitzpatrick age and appearance values are substituted into the formula (Equation 3) and the required power values for a particular patient are calculated, taking into account his individual characteristics. With a calculated power value of 1.9 W and below, the power value is rounded up to tenths and treatment is carried out with this power and a micropulse duration of 50 μs. At a value of the calculated power of more than 1.9 W, it is required to reduce the power and proportionally increase the duration of the micro-pulse, so that the energy of the laser action remains the same. According to the computer simulation for the micropulse mode (the duration of the micropulse is 50-100 μs, the interval between pulses is 2000 μs, the duty cycle is 2.4-4.8%, the duration of the pulse packet is 10 ms, the number of pulses in the packet is 5, the diameter is spots - 100 microns, power - from 0.4 to 1.9 W, wavelength - 577 nm), the power is proportional to time, therefore, with a decrease in power, in order to maintain the same effect, it is necessary to proportionally increase the duration of the micropulse. On the NLU Navilas 577s, it is possible to set the duration of the micropulse in 10 μs steps, and the power of 1.9 W and below. Therefore, for each range of calculated power, which are calculated by the formula for patients aged 30 to 65 years with 1-4 types of appearance on the Fitzpatrick scale, a proportionality correction factor was calculated for the corresponding micropulse duration. With a calculated power from 1.91 to 2.28 W, the resulting power value is multiplied by 5/6 and rounded up to tenths and a micropulse duration of 60 μs is used. With a calculated power from 2.29 W to 2.66 W, the resulting power value is multiplied by 5/7 and rounded up to tenths, and a micropulse duration of 70 μs is used for treatment. With a calculated power from 2.67 to 2.7 W, the resulting power value is multiplied by 5/8 and rounded up to tenths, a micropulse duration of 80 μs is used. The obtained values of the power and duration of the micropulse for the selective micropulse mode are set in the NLU Navilas 577s and used for treatment. Before treatment with the NLU Navilas 577s, the results of modern diagnostic tests are imported, the fundus is photographed and a treatment plan is drawn up. To do this, a pattern is selected from one or several applications and positioned in such a way as to completely cover the areas with pathological changes. Additionally, two safety zones are installed on the areas of the fundus, which should not be exposed to laser radiation. One safety zone is installed on the optic disc. The other is installed next to the avascular zone in an arbitrary place. The setting of two safety zones is necessary for the auto-tracking system to work. Before treatment, individually selected energy parameters are set in patterns on the Navilas 577s NLU, the laser activation mode with an auto-tracking system is turned on, and by pressing the pedal, laser applications are applied according to a predetermined plan. Laser treatment is fast, comfortable, safe and without a contact lens.

The invention is illustrated by the following examples.

Example 1.

A 30-year-old patient with dark skin, dark brown eyes, dark brown hair, corresponds to type 4 on the Fitzpatrick scale, complained of decreased visual acuity in the left eye. Suffers from type 1 diabetes mellitus. Corrected visual acuity was 0.8. When examining the fundus, macular edema was determined, involving the foveal avascular zone and deposits of solid exudates. Optical coherence tomography (OCT) was used to diagnose focal cystic macular edema with a maximum retinal thickness of 276 μm. According to microperimetry data, a decrease in photosensitivity to an average of 24.1 dB was revealed. To select the required power, the age (30 years) and the type of appearance according to the Fitzpatrick scale (4) were substituted into the formula (equation 3). Power (W) = 0.017 * 30-0.41 * 4 + 2 = 0.51-1.64 + 2 = 0.87. The power value is rounded up to tenths up to 0.9 W and is used for treatment with a micropulse duration of 50 μs. Thus, treatment is carried out with the following parameters: micropulse duration of 50 μs, the interval between pulses is 2000 μs, and the duty cycle is 2.4 %, pulse burst duration - 10 ms, power - 0.9 W, number of pulses in a burst - 5, spot diameter - 100 μm, wavelength - 577 nm. Laser treatment was carried out on the Navilas 577s NLU according to the method described above in a selective micropulse mode with a power of 0.9 W. 94 laser applications were applied close to each other, completely covering the edema zone. After 1 month, the visual acuity in the left eye increased to 0.9. According to OCT data, the thickness of the retina decreased to 261 μm, and single microcysts remained in the macula. After 3 months, visual acuity was 1.0. According to OCT data, single cysts disappeared, and restoration of the retinal architectonics was noted. According to computer microperimetry data, the light sensitivity increased to 27.6 dB. With ophthalmoscopy, a significant decrease in solid exudates was noted.

Example 2.

A 42-year-old patient with fair skin, dark blond hair and brown eyes complained of decreased visual acuity, the appearance of a gray spot in front of the right eye about 3 months ago. In terms of appearance, the patient corresponded to type 3 of appearance on the Fitzpatrick scale. Visual acuity without correction was 0.9. With the correction sph + 0.5D, the visual acuity increased to 1.0. When examining the fundus, detachment of neuroepithelium in the macular zone was determined. OCT revealed a local neuroepithelial detachment, under which subretinal fluid was noted. The retinal thickness in the fovea was 410 µm. According to microperimetry data, a decrease in photosensitivity to an average of 26.9 dB was revealed. According to OCT data in En Face mode, the RPE defect in the foveal avascular zone was determined. To select the required power, the age (42 years) and the type of appearance according to the Fitzpatrick scale (3) were substituted into the formula (equation 3). Power (W) = 0.017 * 42-0.41 * 3 + 2 = 0.71-1.23 + 2 = 1.48. The power value is rounded up to tenths up to 1.5 W and is used for treatment with a micropulse duration of 50 μs. Thus, the treatment is carried out with the following parameters: the duration of the micro-pulse is 50 μs, the interval between pulses is 2000 μs, the duty cycle is 2.4%, the duration of the pulse packet is 10 ms, the power is 1.5 W, the number of pulses in the packet is 5, spot diameter - 100 microns, wavelength - 577 nm. Laser treatment was carried out on the NLU Navilas 577s according to the method described above with an individually selected power of 1.5 W. 11 applications were applied close to each other, completely covering the RPE defect in the foveal avascular zone. After 1 month, the visual acuity in the right eye increased to 1.0. According to OCT data, complete resorption of the subretinal fluid with complete adherence of the neuroepithelium was noted. Light sensitivity has increased to 29.6 dB.

Example 3.

A 57-year-old female patient with fair skin, light brown hair, gray-green eyes, has been complaining of decreased visual function for a long time. According to external signs, the patient corresponds to type 2 on the Fitzpatrick scale. When examining the fundus, multiple drusen were observed in the macular region of the right eye. According to OCT data, detachment of the pigment epithelium was diagnosed in the avascular zone. Visual acuity 0.8. Photosensitivity according to computer microperimetry data was 23.1 dB. To select the required power, the age (57 years) and the type of appearance according to the Fitzpatrick scale (2) were substituted into the formula (equation 3). Power (W) = 0.017 * 57-0.41 * 2 + 2 = 0.97-0.82 + 2 = 2.15. On the NLU Navilas 577s, it is possible to set the power of 1.9 W and below. The resulting calculated power value of 2.15 W falls within the range from 1.91 to 2.28 W. Therefore, the resulting power value of 2.15 W is multiplied by 5/6. 2.15 W * 5/6 = 1.79. The power value is rounded up to tenths up to 1.8 W and is used for treatment with a micropulse duration of 60 μs. Thus, the treatment is carried out with the following parameters: the duration of the micropulse is 60 μs, the interval between pulses is 2000 μs, the duty cycle is 2.9%, the duration of the pulse packet is 10 ms, the power is 1.8 W, the number of pulses in the packet is 5, the diameter is spots - 100 microns, wavelength - 577 nm. Laser treatment was carried out on the NLU Navilas 577s according to the method described above, 122 applications were applied to the area of drusen and RPE detachments. One month after treatment, complete adherence of the detachment of the pigment epithelium was noted. After 3 months, OCT showed a decrease in drusen. Visual acuity was 0.9. According to computer microperimetry data, the photosensitivity was 24.6 dB.

Example 4.

A 65-year-old female patient with blue eyes, fair skin and blond hair complained of decreased visual acuity in the right eye. On examination of the eye, thrombosis of the superior temporal branch of the central retinal vein was diagnosed. According to OCT data, focal macular edema was determined, involving the foveal avascular zone. Visual acuity was 0.7. According to microperimetry data, a decrease in photosensitivity to an average of 20.8 dB was revealed. To select the required power, the age (65 years) and the type of appearance according to the Fitzpatrick scale (1) were substituted into the formula (equation 3). Power (W) = 0.017 * 65-0.41 * 1 + 2 = 1.11-0.41 + 2 = 2.7. On the NLU Navilas 577s, it is possible to set the power of 1.9 W and below. The calculated power of 2.7 W falls in the range from 2.67 to 2.7 W, so the resulting power value is multiplied by 5/8. 2.7 * 5/8 = 1.68. The power value is rounded up to tenths up to 1.7 W and is used for treatment with a micropulse duration of 80 μs. Thus, the treatment is carried out with the following parameters: the duration of the micropulse is 80 μs, the interval between pulses is 2000 μs, the duty cycle is 3.8%, the duration of the pulse packet is 10 ms, the power is 1.7 W, the number of pulses in the packet is 5, spot diameter - 100 μm, wavelength - 577 nm). Laser treatment was carried out on the NLU Navilas 577s according to the method described above. 143 applications were applied close to each other completely covering the edema area, including the foveal avascular zone. After 1 month, the visual acuity in the left eye increased to 0.8. According to OCT data, the thickness of the retina decreased, and isolated microcystic cavities in the macula remained. Light sensitivity has increased to 22.7 dB. After 3 months, visual acuity was 0.9. According to OCT data, single cysts disappeared, and restoration of the retinal architectonics was noted. According to computer microperimetry data, the light sensitivity has increased to 25.2 dB.

Claims (1)

A method for selecting the parameters of a selective micropulse mode on the navigation laser device Navilas 577s (NLU Navilas 577s), characterized in that when the pathological process is localized in the foveal avascular zone, a micropulse mode is selected with a selective effect on the retinal pigment epithelium, taking into account the technical characteristics of NLU Navilas 577s: duration of the micropulse - 50-100 μs, the interval between pulses is 2000 μs, the duty cycle is 2.4-4.8%, the duration of the pulse packet is 10 ms, the number of pulses in the packet is 5, the spot diameter is 100 μm, the power is from 0, 4 to 1.9 W, wavelength - 577 nm, then, in order to determine individual parameters for treatment, each patient is determined by the type of appearance according to the Fitzpatrick scale, taking into account external signs: the color of the skin, eyes and hair, the power is calculated by substituting the value of age and type of appearance on the Fitzpatrick scale into the following formula: power (W) = 0.017 * Age - 0.41 * type of appearance on the Fitzpatrick scale + 2, pr and a calculated power of 1.9 W and below, the value of the calculated power is rounded up to tenths and treatment is carried out with this power and a micropulse duration of 50 μs, with a calculated power from 1.91 to 2.28 W, the resulting power value is multiplied by 5 / 6 and rounded to tenths upward and used for treatment with a micropulse duration of 60 μs, with a calculated power from 2.29 to 2.66 W, the resulting power value is multiplied by 5/7 and rounded up to tenths and is used for treatment with a micropulse duration of 70 μs, with a calculated power from 2.67 to 2.7 W, the obtained power value is multiplied by 5/8 and rounded up to tenths and is used for treatment with a micropulse duration of 80 μs, the obtained values of the power and micropulse duration for the selective micropulse mode, the Navilas 577s are installed in the NLU and the treatment is carried out.