Calculation of intraocular phakic lenses (embedded in the eye) - we continue about the eye and its biomechanics
In the last post, I told you what phakic lenses are in general terms. Now the details of how they are put, a review of possible complications and a bit of "tin". Let me remind you that such a lens is mounted directly into the eye while preserving its own crystalline lens - in front of it in front of or behind the iris:
The key to the success of the operation in the absence of surgeon error is the accuracy of the lens calculation and the accuracy of its manufacture. The task is not to touch the lens and not interfere with the natural circulation of intraocular fluid. An improperly created lens can damage the lens and a cataract will appear. If it is wrong to diagnose the camera and install a lens of a larger diameter than necessary, then it will bend and cause glaucoma (increase the pressure inside the eye) or a number of other unpleasant effects. That is, you need to calculate the model of this lens very accurately.
The basis for the accurate calculation of a phakic lens is UBM, that is, ultrasound biomicroscopy.
')
The lens is implanted in the anterior chamber quite simply, there is a sufficiently large space, the lenses in the anterior chamber are stable in their position over time (with mounting in the CPC), the optical calculation of the lens is simple and does not require complicated technology, the material of the front-chamber lenses can be hard ( PPMA - then the incision for its implantation is 5-5.5 mm) and elastic (2.5-3 mm incision).
But there are also enough potential problems with them:
If the lens "clings" to the iris:
With back-camera lenses, the opposite is true: implantation is more difficult from a technical point of view, there is little space in the back chamber, rotation of the lens position is potentially possible over time (that's okay, but this is important for astigmatic phakic lenses), optical calculation of the lens is more complicated and requires measurements with special devices, the material of the posterior chamber lenses must be elastic and repeat the geometry of the lens.
However, the posterior chamber lenses are not visible cosmetically; they can only be detected under a microscope. If the patient does not say, the doctor may not notice. In the usual clinic, for example, almost certainly not see.
A lens in the back of the camera can also cause cataracts due to impaired circulation of intraocular fluid or direct contact. Now the risk of cataracts in the 10-year perspective for posterior chamber ICL is 3-5%, but this study is older than the last generation ICL. New soft lenses have a special perforation - in theory, this means reducing the risk to 1-2%, but there is no practice for a 10-year term - the technology is 4 years.
The combined figure for reversible and irreversible complications in such operations is up to 6% in a 15-year term. The highest percentage of complications is characteristic of operations with the wrong selection of the lens - this lies on the conscience of manufacturers with models with little clinical practice, a wrong diagnosis, and then already on the mistakes of the surgeon.
Ultrasound biomicroscopy - UBM is a method of acoustic visualization of intraocular structures of the anterior segment of the eye (cornea, iris, anterior chamber angle and lens) - a multifunctional combine for any type of ultrasound (B-scan, A-biometry, pachymetry).
The device allows you to receive images of excellent quality, detailed, clear, with the highest accuracy. Circular matrix multifrequency sensor allows you to get the most accurate image of the entire eye. The scanning system shoots at 22 frames per second. Based on the received image, the software automatically calculates the corresponding details of the "relief". The OBM sensor visualizes the front part of the eye chamber without disturbing the integrity of the eyeball, allows for a qualitative and quantitative assessment of its structures, clarifying the spatial relationships of the cornea, ciliary body, iris, lens with opaque refracting media, assess the condition of the surgically created outflow paths.
Such a device is not in every clinic. Therefore, I immediately say that if in your city phakic lenses are ordered without UBM results, then the surgeon orders them on the basis of other diagnostic methods. Not that “by intuition”, but the risks are quite strong. For obvious reasons, it is better to know exactly the size of the spaces where the implantation takes place, especially since the technique allows. Another thing is that the UBM device is quite expensive, and not every center can afford such equipment for the sake of 10 operations per year. Well, this is also a contact method of research, it must be able to do it: separate skills and training are required.
The result is approximately as follows:
Eye with a phakic IOL
Then such an order is sent to the lens manufacturer; here is a sample form:
We most often place a Worst Iris-claw lens (with claws for attachment to the iris) in the anterior chamber. In the back - a line of very soft elastic lenses ICL or EYEPCL, they are very thin and correct complex cases well. Both types of lenses are ordered in Europe. For about a month or two, our partners manufacture (if to be a little more precise, produce and grow) an intraocular lens. The implantation operation resembles the ReLEx SMILE correction, but instead of cutting out the lens in the stroma and evacuating the tissue (extracting lenticles), we get access to the already available free space inside the eye, and unfold the lens there. In general, by and very simplified - SMILE, scrolled in reverse. Walter Sekundo, my partner, generally loves these particular lenses very much - he is a developer of several tools (in particular, tweezers) for installing flexible phakic IOLs.
In short, the choice is simple: the posterior chamber is safer, but after -14 the risk of cataracts increases significantly, so somewhere around -15-16 the anterior chamber becomes safer. This is a global trend, and now almost all clinics make the choice according to this scheme (taking into account the individual characteristics of the patient).
Depending on the clinic, they can offer different types of lenses. Most often - according to the preferences of the surgeon and the clinic as a whole - someone relies on long-term stability, it is important for someone to put it as painlessly as possible, and so on, someone simply has vast experience in one of the types of lenses.
If side effects started with the endothelium (and this is possible in case of incorrect diagnosis in an anterior chamber lens operation, and not immediately, but in a 15-year term), then the only option to keep the vision in perspective is an endothelium transplant. In Russia, it is almost not done (by the way, in our clinic we are just engaged in such transfers), in Europe the cost starts from 10 thousand euros. This operation is often not included in the insurance against side effects and complications. Recently there was a case where the manufacturer recalled the entire batch of lenses due to the increased risk of complications with endothelization. Yes, and the diagnosis is quite expensive. A microscope is used for counting endothelial cells: as a rule, only experienced physicians who work with complex patients can afford it.
Surgical errors are quite interesting. One of the most unpleasant (by the way, frequent cases) that I happened to encounter is the need to “flip the phakic lens” that another surgeon implanted before me “back to front”. It is quite difficult to determine the orientation inside the eye during an operation with ultrathin lenses, it must be done before putting the lens in the injector correctly. The situation was accompanied by an increase in intraocular pressure, pain, low vision, and required urgent intervention. In this case, it ended perfectly - as soon as the operation to reposition the lens was completed, the eye calmed down, and the next day the patient saw 100%. Until now, periodically shown and sees just as well.
Naturally, as in the case of laser correction, doctors first study the pig's eyes with any new material (it is very important to feel its plasticity inside the eye) and implant dozens of lenses to develop skills. Then, patients who are aware of the risk, under the guidance of an experienced mentor, and then - the first independent patients.
The general scenario of the operation is in the last post . This is what we have not touched yet:
1. Before the operation, a very thorough diagnosis is done . The fundus of the pupil with a wide pupil is necessarily examined: if there are any tears in the retina or zones that are dangerous in terms of detachment, they are coagulated by a laser. If this was done - wait two weeks to form a dense spike. Further a few days later (or on the day of surgery, depending on the preferences of the surgeon), prophylactic laser iridectomy is performed - this is a pinhole in the iris, like a valve to relieve excess pressure. Diameter about 0.5 millimeter. And although modern lenses have holes for the circulation of fluid (the lens manufacturers claim that they prevent the pressure from increasing), such a “laser shot” also serves as a reinsurance against a surge in intraocular pressure in the future. Many surgeons, without relying on the recommendations of the manufacturers of lenses, were traditionally insured by performing iridectomy and, as it turned out in a 10-year perspective, not in vain - their patients had no problems with IOP.
2. On the day of surgery, the pupil expands as much as possible. Under local anesthesia, a puncture is performed in the limbal part of the cornea (on the border between the transparent and non-transparent part). This is done there, so that the place of entry after a month cannot be determined visually, there are no turbidity and adhesions. The front chamber is filled with a special viscoelastic preparation. With the help of the injector is implanted lens, rolled up in the form of a tube. This lens is injected into the anterior chamber of the eye, straightened, then its legs are tucked into the back of the iris with a special spatula - the lens is gradually transferred. It is for this purpose that the pupil expands - a big thing should be placed almost in an unfolded form under the iris. Then the pupil is narrowed by a special preparation, and the lens is fixed itself. Then the viscoelastic is removed from the eye cavity. We blind the patient for a couple of hours to prevent infection. Then drops for a month, two weeks without a bath. As a rule, you can see "to the full" in the evening. Restrictions - as with any abdominal operations, a two-week ban on sports.
3. What does the patient see during surgery? Light in front of my eyes. The lens itself is not visible, it does not get into focus at all. Blink, as usual, will not work, the spring will hold the eyelids. The eye feels only touches; there are no painful sensations. The "nervous" part of the operation, when you have the tools in your eye - about 5 minutes. Both eyes are not done immediately - in turn, usually every other day. This is the rule of abdominal operations.
4. Price. Usually, patients can rather easily decide on phakic lenses when they realize that this is a full-blown operation, but for them the only possible and comparable risk is with laser correction. The main limiter is the cost of the operation: implantation of a phakic lens in one eye costs 180,000 rubles, which is more expensive than any type of laser correction.
Everything, now the topic of phakic intraocular lenses is closed - you know almost everything you need about this method of correction (well, you can ask questions). Then I will talk about safe glasses, contact lenses and their features, and then we will touch on issues of view for IT-specialists.
The key to the success of the operation in the absence of surgeon error is the accuracy of the lens calculation and the accuracy of its manufacture. The task is not to touch the lens and not interfere with the natural circulation of intraocular fluid. An improperly created lens can damage the lens and a cataract will appear. If it is wrong to diagnose the camera and install a lens of a larger diameter than necessary, then it will bend and cause glaucoma (increase the pressure inside the eye) or a number of other unpleasant effects. That is, you need to calculate the model of this lens very accurately.
The basis for the accurate calculation of a phakic lens is UBM, that is, ultrasound biomicroscopy.
')
Pros and cons of methods
The lens is implanted in the anterior chamber quite simply, there is a sufficiently large space, the lenses in the anterior chamber are stable in their position over time (with mounting in the CPC), the optical calculation of the lens is simple and does not require complicated technology, the material of the front-chamber lenses can be hard ( PPMA - then the incision for its implantation is 5-5.5 mm) and elastic (2.5-3 mm incision).
But there are also enough potential problems with them:
- A progressive reduction in the number of corneal endothelium cells, which may at some point lead to the need for a new operation (in decades).
- Atrophy of the iris (especially in lenses with attachment to the iris) is unlikely, but the attachment can damage the iris.
- Changing the shape of the pupil - ovalization, the eye turns into a "cat" with an elongated shape,
- Chronic inflammation (because the iris is a plexus of blood vessels and nerves),
- Secondary glaucoma
- Colored halos and highlights.
If the lens "clings" to the iris:
- There is a potential risk of damage to the lens;
- There is a potential risk of hemorrhage from the iris and tearing of its pupillary margin;
- The lens may shift as a result of atrophy of the iris and sagging;
- Another feature - the lens in the anterior chamber is often noticeable to others. When hitting the rays of light in the eye lens flashes and the interlocutor may notice that something is wrong.
With back-camera lenses, the opposite is true: implantation is more difficult from a technical point of view, there is little space in the back chamber, rotation of the lens position is potentially possible over time (that's okay, but this is important for astigmatic phakic lenses), optical calculation of the lens is more complicated and requires measurements with special devices, the material of the posterior chamber lenses must be elastic and repeat the geometry of the lens.
However, the posterior chamber lenses are not visible cosmetically; they can only be detected under a microscope. If the patient does not say, the doctor may not notice. In the usual clinic, for example, almost certainly not see.
A lens in the back of the camera can also cause cataracts due to impaired circulation of intraocular fluid or direct contact. Now the risk of cataracts in the 10-year perspective for posterior chamber ICL is 3-5%, but this study is older than the last generation ICL. New soft lenses have a special perforation - in theory, this means reducing the risk to 1-2%, but there is no practice for a 10-year term - the technology is 4 years.
The combined figure for reversible and irreversible complications in such operations is up to 6% in a 15-year term. The highest percentage of complications is characteristic of operations with the wrong selection of the lens - this lies on the conscience of manufacturers with models with little clinical practice, a wrong diagnosis, and then already on the mistakes of the surgeon.
What is ultrasound biomicroscopy?
Ultrasound biomicroscopy - UBM is a method of acoustic visualization of intraocular structures of the anterior segment of the eye (cornea, iris, anterior chamber angle and lens) - a multifunctional combine for any type of ultrasound (B-scan, A-biometry, pachymetry).
The device allows you to receive images of excellent quality, detailed, clear, with the highest accuracy. Circular matrix multifrequency sensor allows you to get the most accurate image of the entire eye. The scanning system shoots at 22 frames per second. Based on the received image, the software automatically calculates the corresponding details of the "relief". The OBM sensor visualizes the front part of the eye chamber without disturbing the integrity of the eyeball, allows for a qualitative and quantitative assessment of its structures, clarifying the spatial relationships of the cornea, ciliary body, iris, lens with opaque refracting media, assess the condition of the surgically created outflow paths.
Such a device is not in every clinic. Therefore, I immediately say that if in your city phakic lenses are ordered without UBM results, then the surgeon orders them on the basis of other diagnostic methods. Not that “by intuition”, but the risks are quite strong. For obvious reasons, it is better to know exactly the size of the spaces where the implantation takes place, especially since the technique allows. Another thing is that the UBM device is quite expensive, and not every center can afford such equipment for the sake of 10 operations per year. Well, this is also a contact method of research, it must be able to do it: separate skills and training are required.
The result is approximately as follows:
Eye with a phakic IOL
Then such an order is sent to the lens manufacturer; here is a sample form:
EYEPCL Data Sheet
FULL NAME. Doctors / Contact Information / Dr Name & Contect Details | ||||||||||||||||||
FULL NAME. Patient Name: | ||||||||||||||||||
Date of birth of the patient / Data of Patient's Birth | ||||||||||||||||||
Date | ||||||||||||||||||
Right Eye / Right Eye | Left Eye / Left Eye | |||||||||||||||||
Spherical / Spherical | Toric / Toric | Presbyopic / Presbyopic | Toric Diffractive / Toric. diffr | Spherical / Spherical | Toric / Toric | Presbyopic / Presbyopic | Toric Diffractive / Toric. Diffraction | |||||||||||
Refraction / Refraction | Spherical | Cylinder | Refraction / Refraction | Spherical | Cylinder | |||||||||||||
Axis | * Addition for near vision | BCVA | Axis | * Addition for near vision | BCVA | |||||||||||||
W to W (mm) | Method: Digital Caliper / Optical Biometry / IOL Master / Orbscan / S to S (by UBM) | W to W (mm) | Method: Digital Caliper / Optical Biometry / IOL Master / Orbscan / S to S (by UBM) | |||||||||||||||
Pachymetry (µm) | Pachymetry (µm) | |||||||||||||||||
ACD from endo (mm) | ACD from endo (mm) | |||||||||||||||||
K1 (Flat) | Power | Axis | K1 (Flat) | Power | Axis | |||||||||||||
K2 (Steep) | Power | Axis | K2 (Steep) | Power | Axis | |||||||||||||
Axial Lenght (mm) | Optical / Ultra sonic | Axial Lenght (mm) | Optical / Ultra sonic | |||||||||||||||
Lens Thickness / Lens Thickness (mm) | Lens Thickness / Lens Thickness, (mm) | |||||||||||||||||
Rear camera depth / PCD (mm) | Rear camera depth / PCD (mm) | |||||||||||||||||
Hir Hindu astigmatism / SIA | Localization of the incision / Inc. loc | Hir Hindu astigmatism / SIA | Localization of the incision / Inc. loc | |||||||||||||||
Fill out CARE GROUP / Filled by CARE GROUP | ||||||||||||||||||
Model IPCL / IPCL MODEL Size | Model IPCL / IPCL MODEL Size | |||||||||||||||||
Calculated Diopter / Calculated Power | Difference / Residual | Calculated Diopter / Calculated Power | Difference / Residual | |||||||||||||||
one | one | |||||||||||||||||
2 | 2 | |||||||||||||||||
3 | 3 | |||||||||||||||||
What's next?
We most often place a Worst Iris-claw lens (with claws for attachment to the iris) in the anterior chamber. In the back - a line of very soft elastic lenses ICL or EYEPCL, they are very thin and correct complex cases well. Both types of lenses are ordered in Europe. For about a month or two, our partners manufacture (if to be a little more precise, produce and grow) an intraocular lens. The implantation operation resembles the ReLEx SMILE correction, but instead of cutting out the lens in the stroma and evacuating the tissue (extracting lenticles), we get access to the already available free space inside the eye, and unfold the lens there. In general, by and very simplified - SMILE, scrolled in reverse. Walter Sekundo, my partner, generally loves these particular lenses very much - he is a developer of several tools (in particular, tweezers) for installing flexible phakic IOLs.
In short, the choice is simple: the posterior chamber is safer, but after -14 the risk of cataracts increases significantly, so somewhere around -15-16 the anterior chamber becomes safer. This is a global trend, and now almost all clinics make the choice according to this scheme (taking into account the individual characteristics of the patient).
Depending on the clinic, they can offer different types of lenses. Most often - according to the preferences of the surgeon and the clinic as a whole - someone relies on long-term stability, it is important for someone to put it as painlessly as possible, and so on, someone simply has vast experience in one of the types of lenses.
If side effects started with the endothelium (and this is possible in case of incorrect diagnosis in an anterior chamber lens operation, and not immediately, but in a 15-year term), then the only option to keep the vision in perspective is an endothelium transplant. In Russia, it is almost not done (by the way, in our clinic we are just engaged in such transfers), in Europe the cost starts from 10 thousand euros. This operation is often not included in the insurance against side effects and complications. Recently there was a case where the manufacturer recalled the entire batch of lenses due to the increased risk of complications with endothelization. Yes, and the diagnosis is quite expensive. A microscope is used for counting endothelial cells: as a rule, only experienced physicians who work with complex patients can afford it.
Surgical errors are quite interesting. One of the most unpleasant (by the way, frequent cases) that I happened to encounter is the need to “flip the phakic lens” that another surgeon implanted before me “back to front”. It is quite difficult to determine the orientation inside the eye during an operation with ultrathin lenses, it must be done before putting the lens in the injector correctly. The situation was accompanied by an increase in intraocular pressure, pain, low vision, and required urgent intervention. In this case, it ended perfectly - as soon as the operation to reposition the lens was completed, the eye calmed down, and the next day the patient saw 100%. Until now, periodically shown and sees just as well.
How are trained in microsurgery skills for IOL?
Naturally, as in the case of laser correction, doctors first study the pig's eyes with any new material (it is very important to feel its plasticity inside the eye) and implant dozens of lenses to develop skills. Then, patients who are aware of the risk, under the guidance of an experienced mentor, and then - the first independent patients.
What else is important to know about the operation?
The general scenario of the operation is in the last post . This is what we have not touched yet:
1. Before the operation, a very thorough diagnosis is done . The fundus of the pupil with a wide pupil is necessarily examined: if there are any tears in the retina or zones that are dangerous in terms of detachment, they are coagulated by a laser. If this was done - wait two weeks to form a dense spike. Further a few days later (or on the day of surgery, depending on the preferences of the surgeon), prophylactic laser iridectomy is performed - this is a pinhole in the iris, like a valve to relieve excess pressure. Diameter about 0.5 millimeter. And although modern lenses have holes for the circulation of fluid (the lens manufacturers claim that they prevent the pressure from increasing), such a “laser shot” also serves as a reinsurance against a surge in intraocular pressure in the future. Many surgeons, without relying on the recommendations of the manufacturers of lenses, were traditionally insured by performing iridectomy and, as it turned out in a 10-year perspective, not in vain - their patients had no problems with IOP.
2. On the day of surgery, the pupil expands as much as possible. Under local anesthesia, a puncture is performed in the limbal part of the cornea (on the border between the transparent and non-transparent part). This is done there, so that the place of entry after a month cannot be determined visually, there are no turbidity and adhesions. The front chamber is filled with a special viscoelastic preparation. With the help of the injector is implanted lens, rolled up in the form of a tube. This lens is injected into the anterior chamber of the eye, straightened, then its legs are tucked into the back of the iris with a special spatula - the lens is gradually transferred. It is for this purpose that the pupil expands - a big thing should be placed almost in an unfolded form under the iris. Then the pupil is narrowed by a special preparation, and the lens is fixed itself. Then the viscoelastic is removed from the eye cavity. We blind the patient for a couple of hours to prevent infection. Then drops for a month, two weeks without a bath. As a rule, you can see "to the full" in the evening. Restrictions - as with any abdominal operations, a two-week ban on sports.
3. What does the patient see during surgery? Light in front of my eyes. The lens itself is not visible, it does not get into focus at all. Blink, as usual, will not work, the spring will hold the eyelids. The eye feels only touches; there are no painful sensations. The "nervous" part of the operation, when you have the tools in your eye - about 5 minutes. Both eyes are not done immediately - in turn, usually every other day. This is the rule of abdominal operations.
4. Price. Usually, patients can rather easily decide on phakic lenses when they realize that this is a full-blown operation, but for them the only possible and comparable risk is with laser correction. The main limiter is the cost of the operation: implantation of a phakic lens in one eye costs 180,000 rubles, which is more expensive than any type of laser correction.
Everything, now the topic of phakic intraocular lenses is closed - you know almost everything you need about this method of correction (well, you can ask questions). Then I will talk about safe glasses, contact lenses and their features, and then we will touch on issues of view for IT-specialists.
Source: https://habr.com/ru/post/401403/
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