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Alcon Centurion Versus Alcon Infiniti Phacoemulsification machines
In 2014 I started using the Alcon Centurion phacoemulsification machine instead of the Alcon Infiniti machine. The change was smooth but there were a few small adjustments that had to be made.
The main adjustments to be made were as follows:
A. Differences in the Foot pedal.
Foot pedal of the Infinity Phacoemulsification machine (pic 1)
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Foot pedal of the Centurion Phacoemulsification machine (pic 2)
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If I had the choice, I would have kept the Infinity foot pedal and put up with a chord attaching to the new Centurion.
B. Bimanual cortical aspiration
| Ultraflow Bimanual I/A, versus Alcon 0.3mm Polymer I/A, versus Medicel Bi-Manual hand pieces. (Pic 3) For three years I have used the disposable Ultraflow bimanual aspirator and infusion cannulas.The instrument pass nicely through a 1.2 mm paracentesis.I have been very happy with them but in late 2014 there seemed to be a continuous disruption in supply. I was then offered the choice of the new Alcon 0.3 Polymer I/A bimanual set and the Medicel 21G Bimanual set. |
My thoughts are as follows:
Alcon/ Grieshaber Ultraflow Bimanual I/A disposable set. 170.71/2 (pic 4)
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Alcon 0.3 Polymer I/A Bimanual set, part of the Intrepid micro-coaxial system (pic 5)
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Medicel Bi-Manual set – MCEL-SBS110A (pic 6)
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My feeling is that the Ultraflow is the safest and most efficient of these products, followed closely by the Medicel bi-manual set.
The Laser technique is relatively simple and with practice the surgeon can also operate the laser and verify settings. For the patient it is not traumatic and we do not sedate our patients. The discomfort is minimal and comes mainly from the use of the speculum which is why the choice of the first patient is being considered. Few patients seem to be aware of the suction from the Patient Interface (PI) and lying still for the less than two minutes of the procedure seems to be of no concern.
Aim
The ideal first patient should have a well-dilated pupil and a wide palpebral aperture.
Principles
Choose a patient who can hear and understand commands and is able to see the fixation light. Avoid significant head tremor, dementia and claustrophobia. As the procedure is relatively painless not many patients are excluded.
Language barriers do not seem to be an issue as the patient really only needs to lie still and look towards the PI lights.
The palpebral aperture should not be to not be too tight to allow for easy docking.
The nasal bridge should not be too prominent on first case to allow the patient interface (PI) to descend easily without abutting on the nose.
The eye should not be too deep or sunken in the first few patients as it is harder to judge the PI position when looking from the side.
Assess the preoperative pupil size with tropicamide in the clinic and note this down. The pupil will usually dilate more than this after the pre-operative drop regimen in theatre.
Tip
Keep a flash torch and pupil gauge in admitting room. Minimum pupil size is 5.0 mm. The laser can treat close to the pupil margin. The error of parallax is very small and with experience you will feel comfortable doing the laser through pupils as small as 4.4 mm
Also make at least a mental note of the following in the clinic during the pre=-operative assessment.
- The femtosecond laser will not cut through opaque structures, so dense arcus might impede perfect wound construction. However it would be reasonable to go ahead and be aware that a blade may be required to complete the incision.
- A prominent brow or nasal bridge makes docking under visual guidance bit more challenging for the first few operations.
- Cheek fat pads may ride up and cause the eyelashes to turn in under the speculum. This is not a real problem but may cause slight discomfort.
Aim
A well docked stable patient interface (PI) with minimal patient discomfort. The new SoftFit PI makes this step intuitive and simple.
Principles
Measure the patient’s pupil dilation before wheeling them to the femtosecond laser as it interrupts patient flow if you have to wheel them out again while they continue to dilate.
Use a guarded Leibermann-style speculum with a drop of Benoxinate for anaesthesia. Sedation is not required and IV sedation should be avoided as the patient should be compliant. The cornea should be moist when the PI is positioned but probably not over wet.
Make sure the patient’s eye is parallel to the laser, and centered in the speculum gap. Raising the patient’s chin may assist. This will decrease “lens tilt” as the laser will be perpendicular to the cornea.
It is useful to note if the patient has significant arcus before the docking takes place. Once the eye is docked, the arcus resembles the sclera and a definite boundary is not always easy to see. You might be tempted to move the incisions too centrally as you mistake the arcus for the sclera. This is easy to avoid with experience and checking for the arcus soon becomes second nature.
Some patients have excessive fatty cheek pads and floppy lids. Putting in the speculum then pushes the eyelids onto these cheek pads and limits the amount of opening of these lids. As the eyelids are floppy, opening the speculum wider can cause the lids to roll in. Have a look and confirm that the speculum is sitting snugly.
If the nose is prominent, turn the head turned slightly towards the machine for right eye or slightly away from the machine for left eye to keep nose from touching the PI. Excessive rotation should be avoided as this may have the PI contact the lateral canthus.
The SoftFit insert is placed in the PI after the application of a lubricant. The PI is then inserted onto the laser and the fit of the SoftFit Insert checked on the monitor. Bubbles can be manually expressed.
The PI is best positioned just at the eyebrow to allow for sufficient movement of the joystick control.
Lubricate the cornea and move the PI until it moves anterior to the cornea and watch from the side while you slowly lower the PI. You will see if the lid or speculum is in the way.
If the PI touches the patient’s nose or the speculum, the pressure on the sensor will increase without you seeing a “wave “of fluid on the cornea. Reposition the PI and dock again.
Don’t hover once you’re central and clear of the lids (you are not a helicopter pilot). Descend and dock.
A “wave “of fluid is seen to cross across the cornea. Once it crosses the center point, suction is applied and the joystick turned so that the pressure bar is in the green.
If corneal folds are seen on the screen, the power needs to be increased on the computer to ensure a free cut through the anterior capsule. This happens in less than 1 in 50 cases.
The PI is forgiving in terms of the ability to maneuver centration and incisions but is best placed to expose the lateral limbus and with the globe well centered. If the eye is excessively rotated superiorly the corneal incisions may be oblique and the nucleus will be tilted. For final adjustments just tapping the joystick allows for finer control.
With suction engaged commence the positioning of the various elements (limbus, centration of capsulorhexis, size of capsulorhexis, depth of nuclear cuts and the corneal incisions). The rhexis size can be reduced to avoid contact with a small pupil down to 4.4 mm. A 0.5 mm clearance is sufficient.
In vary few cases the contact lens comes off the SoftFit and remains on the cornea after the procedure. This can be gently removed. I do not try look for the contact lens on the eye straight after the procedure as the PI is in the way. Rather I look at the screen and see if I can see the SoftFit contour and the small white line showing where the incision was made. Only if I cannot see the outline on the screen do I look at the patient’s cornea.
Tip
Wait for the audible click before applying the laser treatment. If you eagerly press the foot pedal before the click, an error message will appear. Simply reset the treatment and then press the foot pedal again.
During the treatment note the suction pressure. If it falls or the limbal contact is lost then the corneal incisions which are undertaken last may be aborted. If treatment has commenced and suction is lost do not reengage but go to a manual procedure as it is impossible to accurately line up a partial treatment.
Do not be afraid if you have placed a gentian violet dot on the cornea to mark the axis of a toric lens as the femtosecond laser is not impeded by this.
Aim
A patent side port.
Principles
Stabilize the eye with a Thornton ring or alternative.
You will know from your programmed parameters how many degrees your side ports will be from your main incision. They can sometimes be difficult to find. If so, dry the cornea and they may be easier to see.
The incision is much more horizontal or “flatter “than you imagine.
Move the Slade spatula in a plane horizontal to the iris. Force is not required.
When using a blade to enter the eye you can see the tip enter into the anterior chamber. In femtosecond laser surgery you may not be sure where the opening through the endothelium is. Sweeping vigorously from side to side in order to open the wound is not encouraged.
Insert the cannula of the viscoelastic syringe and fill the anterior chamber starting in the anterior chamber distal to the entry. By placing your cannula across and over the central pupillary area you ensure that the viscoelastic is above the capsulorhexis. This also will allow any bubbles to be moved towards the limbus and then towards the incision site and away from the central pupillary area.
Avoid injecting viscoelastic underneath the free capsular flap as it then will roll into the angle of the eye, (which is not a problem as it can be easily removed but it does take away the flourish with which you can usually remove the central capsule.)
Do not overfill the anterior chamber.
Tip
A small amount of Balanced Salt Solution (BSS) mixed with unpreserved phenylephrine (with or without lignocaine) injected before the viscoelastic will help to re-dilate a pupil which may have constricted.
Aim
A clean open self-sealing incision.
The SoftFit makes superb wounds which are usually easy to open, especially if the PI was well docked.
Principles
Stabilize the eye with a Thornton ring or similar.
You can often identify the main incision site by looking for a line of gas bubbles in the stroma. Insert the Slade spatula or the capsulorhexis forceps just distal to this line into the opening of the main incision.
Push gently forward and downwards and the incision opens. If there has been a tilted dock, the incision may not be completely patent. If so, you can sweep the wound and the incision will open. I always sweep backwards in a circular motion to avoid causing any damage to Descement’s membrane.
Tip
Regard the laser incision as a perforate potential space rather than a distinct opening in patients with severe arcus as the laser does not cut well through opaque cornea.
Aim
A free circular capsulorhexis .
Principles
Inspect the capsulorhexis and look for the appearance of a “clear red gutter” around the central capsular button to see if it looks free. It almost always is free and may even be floating in the anterior chamber.
Use a capsulorhexis forceps to grab the central circular flap and gently lift it off the surface of the lens.
Tip
Keep your eye on the area where the capsule separates and not where your forceps are grabbing.
In the very rare event that there are micro-adhesions gently fold the capsule over and continue as for a manual capsulorhexis.
After removing the capsule from the eye I push on the posterior lip of the incision for a few seconds. This allows some of the viscoelastic to egress from the eye and “decompresses the anterior chamber”. I don’t rush this to allow pressures within the eye to equilibrate.
Aim
In the rare event of a micro-adhesion you must complete the circular capsulorrhexis without having the anterior capsule tear.
Principles
Very very occasionally there will be capsular micro-adhesions where the capsule has not been cut completely free. There are various types of tags.
- One or two small micro-adhesions in an otherwise free flap
- A localised area with multiple small tags which may be due to a corneal opacity blocking the laser from reaching the capsule.
Grab the free end of the capsulorrhexis flap and gently guide the leading edge so that the capsulorhexis is completed. This can be done by lifting the flap and pulling centrally, which will generate a circumferential vector.
Alternatively you can continue separating the capsulorrhexis in the opposite direction until you return to the area of the tag. This usually will allow the two ends to join.
If the imperforate area is larger, you can also fold the capsule and complete the capsulorrhexis in a shearing manner. This sometimes creates a new line of cleavage either inside or outside the laser induced capsulorrhexis, but this does not seem to cause any problems if it joins the original capsulorrhexis again. It is preferable if the new line of cleavage is outside the original incision rather than inside it.
Tip
Avoid any rapid intraocular movements and let your fingers “muscle memory” guide you into completing the capsulorrhexis, just as you would have done if you never had a femtosecond laser.
Next step: Hydrodisection
Comments
Each surgeon will personalize the way they perform this operation.
The changes that made the most difference to the way I operate evolved over the first 500 operations. Perhaps starting off by incorporating these changes earlier will shorten any learning curve.
The biggest change in my technique was using bimanual cortical aspiration to remove the cortex. This reduced the operating time by 3 minutes per cataract as the sub-incisional cortex was no longer a problem.
Taking time to re-dock on an eye that was not centered in the Patient Interface initially, was time well spent. Starting to laser on a tilted eye is unwise, when a few minutes more diligence would result in a well centered complete capsulorhexis.
Taking time to have a mobile nucleus with good hydrodisection improves the safety of the operation. The initial fear of “blowing out” the posterior capsule has proved to be unfounded.
After performing 3000 cases I have decided to abandon using the laser to make the main incision as the site is not always predictable. I now use a metal blade to make the main incision.
There is no doubt in my mind that the femtosecond laser makes cataract surgery, which is a safe operation with excellent results, even safer.