removing an IOL can be tricky. first you have to free the IOL from its capsular adhesions. then you have to get it out. here i will share a few tips on removing IOLs.
freeing the IOL from the capsule. The ease of IOL removal is mostly dependant on how long the IOL has been in the bag. IOLs which have been in the bag for a few weeks are very easy to free from the bag. IOLs that have been in the bag for years can be very hard to remove. Removing an IOL with an intact posterior capsule is far easier than when the patient has had a YAG capsulotomy.
the first step is to somehow get a visco dissection plane started between the IOL and the capsule. I like to use dispersive OVD especially when the posterior capsule is not intact. with IOLs that have been in place for a while i like to use a 27 gauge needle attached to viscoat and use the sharp end to get under the capsule and then inject the viscoat. then i will sometimes use the Duet micro forceps (as shown in the video) to lift the capsule to get a canula under for more viscodissection. I also like to use a flat hydrodissction cannula for visco dissection as the flat surface makes it easier to get between the capsule and the IOL. most of your attention should be directed to freeing up the haptics with viscodissection. If the posterior capsule is intact the viscoat will often track around the optic and free it from it posterior attachments. after the capsular adhesions are freed try to spin the IOL clockwise to allow the haptics to spin free. sometimes the haptics are just too stuck and must be cut to free separately or are even left in the bag.
removing the IOL can be done through a small incision (refolding or cutting) or by extending the incision to the size of the optic.
The high index of refraction acrylic IOLs (eg. MA60, SA 60) can be refolded within the eye either using the folding forceps or the henderson technique. The standard refolding technique uses a paracentesis across from the main wound (3.5 mm) to introduce a spatula to place under the optic while using an open IOL insertion forcep above the optic in the anterior chamber. while lifting with the spatula and coming down on top of the optic with the open insertion forceps the IOL can be folded inthe anterior capsule. once folded the optic is simply removed through a 3.5 mm or so wound please use lots of OVD during this process. refolding the IOL only works well with thin acrylic IOLs likem the SNWF, SA60, MA60 and in my hands is virtually impossible with thick acrylic IOLs like the AR40 and the slippery IOLs like the silcon three piece IOLs. see video of refolding.
The henderson (bonnie henderson boston ma) technique for folding soft IOLs such as the IQ single piece acrylic is very slick. dr henderson's technique is to simply pull on an externalized haptic (with 0.12 or similar toothed forcep) while pushing on the optic 180 degrees across from the wound (inside the eye) with a hook (eg. Kuglen) amazingly the IOL folds itself and pops out of the eye. see video.
There a few ways to cut an IOL to get the optic small enough to remove through a small incision. One classic technique is to only cut about 2/3 through the IOL and make what looks like a Pac Man and rotate the IOL out through the wound as shown in the video.
You can also cut the IOL completely in half or into thirds and bring out the pieces. i like to use the Osher mildly serrated cutter from Duckworth and Kent as shown in this video. you can usually keep the IOL from flopping around too much by holding the externalized haptic with this cutter. if you are in a bind you can even use Vanna scissors to cut the IOL.
i also think the Duet forceps and IOL cutters can be handy to cut IOLs and haptics. you can use the Duet forceps through a paracedntesis to stop the IOL from flopping about and hitting the cornea. both the cutter and the forceps can pass through a paracentesis. here the Duet system forcep is used to hold an IOL while cutting in the video.
Showing posts with label IOL. Show all posts
Showing posts with label IOL. Show all posts
Dec 14, 2015
Dec 12, 2015
IOL centration and placement
A perfectly placed IOL is centered and right side up in the capsular bag. Perfect placement of the IOL relies on controlling the preceding steps of the cataract surgery. The first step of IOL placement immediately follows the removal of all the lens material. The capsular bag is reformed with an ophthalmic viscoelastic device (OVD) or viscoelastic. I typically use a cohesive OVD to fill the capsular bag. I am careful to inject a wave of OVD ahead of the cannula to protect the posterior capsule from the relatively sharp cannula. I try to fill the capsular bag without releasing OVD anterior to the anterior capsule into the sulcus, as this can compresses the bag and makes IOL placement more difficult.
Sometimes the wound must be extended to allow IOL placement. With typical coaxial phacoemulsification the needle requires an incision from 2.5-3.0 mm. Depending on the type of IOL and the insertion technique you may need to extend the wound to as much as 4.0 mm for a foldable IOL and 6.0 mm for a PMMA IOL. Extension of the wound is typically done with the keratome or a crescent blade. It is better to make a well formed and controlled extension of the wound than stretch the wound during lens placement. Stretched wounds often leak and require sutures or increase the risk of infection. Many of the newer IOL insertion systems do not require enlargement of the wound beynd that required of the phacoemulsification needle.
Placing a PMMA IOL is simple, as no folding is required, but does require a larger wound that can extend rehabilitation time and induce astigmatism. The wound is extended to 6.0 mm for a typical PMMA IOL with an optic size of 6.0 mm. Kelman-McPherson (or similar) forceps are used to grasp the trailing haptic and adjacent ½ of the optic. Hold the forceps on their side to keep the IOL flat while placing the leading haptic through the wound and down into the capsular bag. The forceps are released and repositioned onto the trailing haptic which is then placed into the capsular bag. A Kuglen hook (or similar instrument) may be used to place the trailing haptic.
Foldable IOLs may be placed with forceps rather than with an injector especially when using a three piece IOL design. Forceps placement requires a larger incision than is needed when using an IOL injector but is a very controlled process. As IOLs get thicker with increasing dioptric power, the incision may need to be slightly larger with high power IOLs (4.0 vs. 3.5 mm). There are 2 basic folding strategies using forceps. The first strategy involves folding the IOL axially along the axis of the haptics and the second strategy shifts the fold 90 degrees so that the haptics fold onto each other which looks something like a “moustache” (see video). An IOL with an axial fold is easier to insert, allowing for a smaller incision, but requires a 2 step procedure to place both haptics in the bag. An IOL with a moustache fold is harder to insert, requires a larger incision, but as the IOL unfolds both haptics slip into the bag in one step.
The most common technique to insert a foldable IOL is through an injector. These systems use a plunger to squeeze an IOL through a cartridge into the eye. The single piece acrylic and silicone plate haptic IOLs are the simplest to use with injectors. These designs have haptics that are sturdy and resistant to damage from the plunger as it forcefully pushes the IOL through the cartridge. The three piece IOLs are more difficult to inject as the haptics are more fragile and susceptible to plunger damage. The cartridge tip of the injector system can damage Descemet’s membrane. Surgeons should ensure that the tip is under Descement’s by placing the “toe down” as the cartridge passes through the posterior cornea.
Sometimes the wound must be extended to allow IOL placement. With typical coaxial phacoemulsification the needle requires an incision from 2.5-3.0 mm. Depending on the type of IOL and the insertion technique you may need to extend the wound to as much as 4.0 mm for a foldable IOL and 6.0 mm for a PMMA IOL. Extension of the wound is typically done with the keratome or a crescent blade. It is better to make a well formed and controlled extension of the wound than stretch the wound during lens placement. Stretched wounds often leak and require sutures or increase the risk of infection. Many of the newer IOL insertion systems do not require enlargement of the wound beynd that required of the phacoemulsification needle.
Placing a PMMA IOL is simple, as no folding is required, but does require a larger wound that can extend rehabilitation time and induce astigmatism. The wound is extended to 6.0 mm for a typical PMMA IOL with an optic size of 6.0 mm. Kelman-McPherson (or similar) forceps are used to grasp the trailing haptic and adjacent ½ of the optic. Hold the forceps on their side to keep the IOL flat while placing the leading haptic through the wound and down into the capsular bag. The forceps are released and repositioned onto the trailing haptic which is then placed into the capsular bag. A Kuglen hook (or similar instrument) may be used to place the trailing haptic.
Foldable IOLs may be placed with forceps rather than with an injector especially when using a three piece IOL design. Forceps placement requires a larger incision than is needed when using an IOL injector but is a very controlled process. As IOLs get thicker with increasing dioptric power, the incision may need to be slightly larger with high power IOLs (4.0 vs. 3.5 mm). There are 2 basic folding strategies using forceps. The first strategy involves folding the IOL axially along the axis of the haptics and the second strategy shifts the fold 90 degrees so that the haptics fold onto each other which looks something like a “moustache” (see video). An IOL with an axial fold is easier to insert, allowing for a smaller incision, but requires a 2 step procedure to place both haptics in the bag. An IOL with a moustache fold is harder to insert, requires a larger incision, but as the IOL unfolds both haptics slip into the bag in one step.
The most common technique to insert a foldable IOL is through an injector. These systems use a plunger to squeeze an IOL through a cartridge into the eye. The single piece acrylic and silicone plate haptic IOLs are the simplest to use with injectors. These designs have haptics that are sturdy and resistant to damage from the plunger as it forcefully pushes the IOL through the cartridge. The three piece IOLs are more difficult to inject as the haptics are more fragile and susceptible to plunger damage. The cartridge tip of the injector system can damage Descemet’s membrane. Surgeons should ensure that the tip is under Descement’s by placing the “toe down” as the cartridge passes through the posterior cornea.
When placing the IOL surgeons need to be sure that the IOL is right side up. All common IOLs (except plate haptic) are made with the haptics in the same configuration. IOLs are designed to rotate in only one direction safely – clockwise. The haptics are designed so that a right handed surgeon can most easily rotate the IOL into position using a hook at the junction of the optic and haptic. If the IOL is upside down the haptics will create an “S”, reminding you to Stop and flip the IOL. When a 3 piece IOL is left upside down it can cause a significant myopic shift. This is because the haptics in 3 piece IOLs are often angulated to push the optic posteriorly and support the vitreous face. When the IOL is upside down, the haptics push the optic into a more anterior position which creates a myopic shift.
IOL designed for rotation by right handed surgeon
IOL designed for rotation by right handed surgeon
When upside down the IOL looks like an “S” so Stop
While placing the IOL surgeons should confirm that both haptics are in the capsular bag. When one haptic is in the bag and one in the sulcus the IOL will not center. As the diameter of the capsular bag is more constrained than the sulcus, the optic of the misplaced IOL will decenter toward the sulcus placed haptic. This can be remedied by adding OVD and rotating the IOL clockwise while pushing posteriorly with a hook at the junction of the optic and IOL.
If the IOL still does not center despite having both haptics in the bag there are 2 most likely possibilities: haptic damage requiring IOL removal and zonular dialysis. IOL decentration from small amounts of zonular dialysis can often be overcome by rotating the IOL. Rotation of the IOL is especially effective with three-piece IOLs. Aligning the the three-piece haptics to the axis of weakness supports the zonules and often centers the IOL. If rotation does not work adding a capsular tension ring may center the IOL.
When the capsular bag is not perfect IOL placement is more difficult. A single anterior capsular tear that has not gone radial is a common problem that usually causes no long term problems. Some surgeons will make a controlled radial incision 180 degrees away and place an IOL in the bag. Another option is to place a single piece acrylic in the bag as this IOL places little tension on the bag which makes extension of the radial tear less likely (figure 7). The final option for an anterior capsular tear is to place a three-piece IOL in the sulcus. The foldable single piece IOLs (both the acrylic and plate haptic) are not a good choice for the sulcus as their haptics can cause pigment disruption of the iris and inflammation and their smaller size allows lens dislocation.
If the posterior capsule is not intact the IOL is usually placed in the sulcus. The wound can be extended to allow placement of a large PMMA IOL into the sulcus but more commonly a foldable IOL is placed into the sulcus using either forceps or an injector. If the posterior capsular tear is round or has been rounded by creating a continuous posterior capsulotomy, the IOL can be gently placed into the bag.
If the capsule is not adequate for IOL support the surgeon has several options, none of which is clearly superior. An anterior chamber IOL can be placed if the angle is healthy, although this requires extension of the wound to 6 mm. The IOL can be sutured to the iris with 10-O Prolene suture using a foldable IOL. Another option is to suture the IOL to the sclera using either a foldable IOL, or extending the wound to for a large PMMA IOL with eyelets on the haptics designed for suturing to the sclera.
If the IOL still does not center despite having both haptics in the bag there are 2 most likely possibilities: haptic damage requiring IOL removal and zonular dialysis. IOL decentration from small amounts of zonular dialysis can often be overcome by rotating the IOL. Rotation of the IOL is especially effective with three-piece IOLs. Aligning the the three-piece haptics to the axis of weakness supports the zonules and often centers the IOL. If rotation does not work adding a capsular tension ring may center the IOL.
When the capsular bag is not perfect IOL placement is more difficult. A single anterior capsular tear that has not gone radial is a common problem that usually causes no long term problems. Some surgeons will make a controlled radial incision 180 degrees away and place an IOL in the bag. Another option is to place a single piece acrylic in the bag as this IOL places little tension on the bag which makes extension of the radial tear less likely (figure 7). The final option for an anterior capsular tear is to place a three-piece IOL in the sulcus. The foldable single piece IOLs (both the acrylic and plate haptic) are not a good choice for the sulcus as their haptics can cause pigment disruption of the iris and inflammation and their smaller size allows lens dislocation.
If the posterior capsule is not intact the IOL is usually placed in the sulcus. The wound can be extended to allow placement of a large PMMA IOL into the sulcus but more commonly a foldable IOL is placed into the sulcus using either forceps or an injector. If the posterior capsular tear is round or has been rounded by creating a continuous posterior capsulotomy, the IOL can be gently placed into the bag.
If the capsule is not adequate for IOL support the surgeon has several options, none of which is clearly superior. An anterior chamber IOL can be placed if the angle is healthy, although this requires extension of the wound to 6 mm. The IOL can be sutured to the iris with 10-O Prolene suture using a foldable IOL. Another option is to suture the IOL to the sclera using either a foldable IOL, or extending the wound to for a large PMMA IOL with eyelets on the haptics designed for suturing to the sclera.
References:
Thomas A. Oetting, MD, Cataract Surgery for Greenhorns, MedRounds Publishing, 2005, (available at http://www.medrounds.org/cataract-surgery-greenhorns)
Oetting, TA, Beaver HA, Johnson AT, Intraocular Lens Design Material and Delivery, in Essentials of Cataract Surgery, Henderson, Slack, Thorofare NJ, chapter 17, pages 133-146.
Chang, DF, TA Oetting, T Kim, Curbside Consultation in Cataract Surgery, Slack, Thorofare NJ, 2007.