Freeing and Removing an IOL

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.

Phaco Machine Basics

Phacoemusification machines can be overwhelming at first. Here i will try to simplify them as best i can to help those that are just getting started using them. I think it is important to have a good understanding of how they operate and not simply rely on past settings, equipment representatives, and/or the circulating nurses to run these devices critical to your success as a cataract surgeon.

These machines have four main components and software that ties the components together. First a system of irrigation which is typically just a bottle that is hung at variable heights above the surgical eye. Second the foot pedal which allows the surgeon to control the machine. Third an ultrasound hand piece which typically has crystals which vibrate the phaco needle with various power waveforms controlled by the phaco machine. And finally and most importantly, the pump, which is classically either a flow based or vacuum based device.

The irrigation system on phaco machines is typically is just an adjustable bottle held higher than eye to allow infusion of fluid. The machine can adjust the bottle height for various phases of the surgery. For example when the vacuum goes up during segment removal the bottle height typically will need to be higher to maintain the anterior chamber. similarly when you are doing anterior vitrectomy the bottle height should go way down. The machine can also turn the fluid on and off. When the foot pedal goes from position 0 to 1 the fluid is typically turned on by the phaco machine. Some phaco machines can detect when the irrigating fluid bottle is getting near empty but most cannot.

The foot pedal is typically controlled with the dominant foot (w/o shoes w/socks). although some such as the famous surgeon Jim Davidson (marshaltown iowa) suggests that the phaco foot pedal is simpler than the microscope pedal and uses his non-dominant foot for the phaco machine saving the dominant foot for the microscope. The most basic function of the accelerator like portion of the foot pedal is common across all brands with 4 positions: Position 0 – everything is off; Position 1 – irrigation is on, no pump, no U/S; Position 2 – irrigation is on, pump is on, no U/S; Position 3 – irrigation is on, pump is on, U/S is on. some of the foot pedals are wireless now such (eg. Stellaris) but most have a cable that connects to the phaco machine

The ultrasound (U/S) hand piece vibrates the phaco needle at a set rate in the 20,000 to 40,000 HZ range. The vibration is typically delivered by electrically stimulating crystals with a resonate frequency and the crystals are connected to the phaconeedle. many of the modern hand pieces have as many a 4 crystals to allow the needle to handle more load from a hard cataract. Increasing the U/S power typically increases the excursion of the needle but not the frequency which usually remains stable. With increasing load, such as a very hard cataract, the frequency and excursion may not keep up. when setting up the pahco machine for the case one must "tune" the handpiece. the machine sends pulse to the handpiece and sees how much power must be delivered to move the needle. this "tuning" helps to adjust for subtle variations from different needles and handpieces.

The phaco machine can set up a variety of ultrasound modes. In continuous mode the ultrasound energy is on on when the pedal is in position 3 and increases in excursion or power the deeper the surgeon is into position 3 up to a set maximum. In pulse mode the ultrasound contains pulses of ultrasound where it is on (set %) and then off (set %) for a set frequency. the deeper the pedal is into position 3 the more power each pulse will have up to a set maximum. The typical pulse will have a 50% duty cycle with an on time equal to the off time. the classic pulse setting is the howard fine "choo choo chop" setting with a low frequency of about 4 Hz and 50% duty cycle that is useful to acquire a piece for chopping and kind of sounds like a choo choo train. another common setting is to increase the frquency to about 100 Hz and have an on time which is less than off time creating hyperpulses which seem to run more cool to protect against wound burn. finally most machines feature a burst mode where stepping further into position 3 decreases the time between bursts of phaco such that when the pedal is fully engaged the power is continuous.

Recently some machine handpieces have featured an oscillatory component in addition to the classic longitudinal ultrasound. AMO features a figure 8 motion of the phaco needle in it latest phaco machine. Alcon in the infinity Ozil machine has a rotational feature in addition to the longitudinal ultrasound. as this rotational energy does not directly push away the nucleus pieces like the longitudinal ultrasound does the nuclear bits seem to come more readily to the tip in these modes.

The phaco pump is the most important and complex part of the phaco machine. The pump comes in two basic varieties: vacuum based (eg venturi) and flow based (eg peristaltic). A vacuum based pump creates more vacuum (mmHg) when the pump works harder. A flow based pump creates more flow (cc of fluid/min) when the pump works harder. In a real world it is hard to separate flow from vacuum as the resisitance in the tubing keeps the two related. the parameters of the pump will depend on the phase of the surgery. you will want very little fluid flow during sculpting and you will want alot of vacuum when removing the segments or when holding onto the nucleus during chopping. You might want to look over the classic definitive text in this area by Barry S. Seibel, Phacodynamics.

In pumps the vacuum, flow rate and resistance to flow in the tubing are related. I find it useful (maybe because i used to be an electrical engineer) to compare the fluid relationship to Ohm's law (E=IR) where the relationship between current I (analgous to flow rate) , voltage E(analogous to vacuum) and resistance R (analogous to resistance to flow in tubing) are related. just like it is impossible to have a pure current source or voltage source it impossible to create a pure vacuum or flow based pump. but these pumps do behave differently in practice and so it is important to understand how to operate them to your specifications.

Vacuum Pumps. The most common of these are Venturi pumps (Stellaris, Millennium, Accurus) where compressed air passes over a column of air creating a vacuum proportional to the flow of air over the column (this is similar to the way a wing creates lift). Increasing pump power increases vacuum directly; flow rate indirectly based on the amount of resistance to flow. Typically a Venturi pump requires an external source of compressed air (Millennium) or an internal compressor (Accuris or Stelaris) which has limited acceptance of this pump. The compressed gas flows over the open top of a rigid column or cassette attached to tubing creating vacuum. Flow rate for a particular amount of vacuum is then dependant on the resistance of flow to the fluid. This is roughly analogous to electric current voltage relationship (Ohm’s. This law) i=e/r where e = voltage (analogous to vacuum); i = current (analogous to flow rate); r = resistance (analogous to tubing and occlusion). As such with a given vacuum setting of the pump when you have less resistance in the tubing the flow rate will increase and conversely when you have more resistance you will get less flow through the tubing.

Controlling the vacuum based pump is very simple as you only have to set the vacuum and have no setting for flow rate. Typically you would use a fixed vacuum (ie. no matter how deep you are into position 2 or 3 the vacuum stays the same) for sculpting and to hold while chopping. You would typically use a variable vacuum (ie. the deeper into position 2 the more vacuum and faster the pump) to remove epinuclear material and for I/A of the cortex.

Flow based pumps. The most common flow based pump is the peristaltic pump (Infinity, Sovereign, and Legacy). With peristaltic pumps the faster the pump goes the more cc/min of fluid passes through the tubing or the more flow. This is often refered to as the aspiratiion flow rate (AFR). Increasing the power of the pump increases the flow rate directly and vacuum indirectly through the resistance of the tubing. So the vacuum is just dependant on the amount of fluid flow and this relationship is roughly analogous to electric current voltage relationship (Ohm’s law): e=ir where e = voltage (analogous to vacuum); i = current (analogous to flow rate); r = resistance (analogous to tubing resistance). As such you will only get some vacuum if there is some resistance to flow (or some occlusion).

These flow based machines typically have a setting for the flow rate but also have a vacuum cut off. the vacuum cut off is the point at which the pump will stop if a certain vacuum is reached. so you set the flow rate and pump humms along until the vacuum rises (due to increased resistance) to the vacuum cut off point and then the pump simply stops. so even though with peristaltic machines you have a vacuum and a flow rate setting you can only make the pump work harder by increasing the flow rate. setting the vacuum higher only sets the point higher at which the pump stops when this vacuum is reached.

With modern peristaltic pumps (eg. Infiniti) for each foot position 2 you can have fixed or variable flow; fixed or variable vacuum cut off. if you want the pump to be responsive to pressing harder on the pedal (eg for I/A) you would use a variable setting such that the aspiration flow rate or at least the vacuum cut off increases as you step down into position 2. when you set both the flow rate and the vacuum cut off to be variable so that it increases as you step into position 2 the peristaltic pump begines to feel more like a venturi pump. you typically would set the pump low and fixed for sculpting (80 mmHg vacuum cut off: 20 cc/min flow rate); higher but still fixed for chopping and segment removal (300 mm Hg and 30 cc/min); and high and vairable for I/A where you need more control (500 mmHg and 50 cc/min flow rate). i usually use roughly a 10:1 ratio of vacuum cut off:flow rate with the infinity and legacy for segment removal, chopping and I/A.

Which pump is better?. There is no clear favorite for every situation. For certain parts of the procedure the flow based pumps seem better like sculpting the groove as you can set the vacuum low with a reasonble flow rate. For other parts of the procedure like I/A and anterior vitrectomy vacuum based pumps are better as the vacuum is not related as much to occlusion (resistance to flow). for years the flow based pumps were most popular in part at least because the early vacuum based pumps required an external compressed gas line and as the peristalitic were cleverly marketed as "safer" for divide and conquer. recently, as the phaco procedure has moved more toward higher vacuum for chopping and away from scupting the vacuum based pumps are getting more popular.

Vacuum based pumps seem to have less post occlusion surge during segment removal and material seems to come to the tip better for irrigation aspiration. vacuum based pumps are clearly better for vitrectomy as the vitreous comes to the tip even without occlusion from the guillotine which can be frustrating with flow based pumps. The disadvantage of the venturi pump which is the most common vacuum based pump is the need for compressed gas and the need for a rigid cassette.

Flow based pumps seem to be better for low vacuum jobs like sculpting. With modifications such as setting the vacuum and the flow to increase with increasing position 2 on the foot pedal the flow based pumps can be more responsive for I/A like the vacum based pumps. The flow based pumps do not require compressed gas.

Iris Prolapse

Iris prolapse can create problems during surgery and can lead to iris damage which can be dysfunctional.

Iris prolapse typically comes from a wound which is too short or from an iris which is floppy and/or poorly dilated.  The actual prolapse of the iris usually occurs during hydrodissection and can create transillumination defects, loss of iris tissue, iridodialysis, and hyphema.   It is important for eye surgeons to know how to preserve the iris when prolapse occurs and i suppose, more importantly, to prevent it from occuring in the first place.


     

Wound too short.  When the wound is too short one of the best options to prevent iris prolapse is to simply close the short wound and move to another site.  Often however moving to another site is difficult as the brow, a bleb, or the surgeons handedness get in the way of this solution.   A nice simple solution is to place a single iris hook under the incision to pull the iris under the incision preventing prolapse.  If the pupil is also small it can be useful to place 4 hooks in a diamond configuration with one hook under the wound to both prevent iris prolapse and to open the small pupil.  Iris rings such as the Malyugin ring can be used also but if the wound is very short the iris can still prolapse with the ring. 

Floppy iris.  When the patient is at risk for a floppy iris (intraoperative floppy iris syndrome) from an alpha blocker (especially Flomax or tamsulosin) or some other cause (eg ischemia ) it may be best to prevent iris prolapse with iris hooks or a Malyugin ring especially if the pupil is small.  The most common time for iris prolapse is during hydrodissection when the fluid wave passes around the lens and out the eye taking the iris out too.  Excessive and especially dispersive viscoelastic can make hydrodissection more risky for iris prolapse.  I like to remove viscoelastic above the lens prior to hydrodissection to help prevent this complication.   Gentle rocking of the lens will help to release trapped fluid behind the lens which will lower the pressure and deepen the anterior chamber.

Repositing the iris.  When iris prolapse occurs the emphasis should be on preserving the iris and preventing further prolapse.  The first step following prolapse is to use the paracentesis to remove fluid pressure from within in the eye which is pushing the iris out.  Then using a viscoelastic cannula gently reposit the iris.  After the iris is back into position consider placing an iris hook under the wound to keep the iris from further prolapse.   below you will find a video showing these techniques  Rarely, iris prolapse willl occur when you face posterior pressure from a choroidal hemorrhage, choroidal effusion, or misdirection of aqueous.

References:

Chang DF, Braga-Mele R, Mamalis N, Masket S, Miller KM, Nichamin LD, Packard
RB, Packer M; ASCRS Cataract Clinical Committee. ASCRS White Paper: clinical
review of intraoperative floppy-iris syndrome. J Cataract Refract Surg. 2008
Dec;34(12):2153-62. 

Chang DF. Use of Malyugin pupil expansion device for intraoperative
floppy-iris syndrome: results in 30 consecutive cases. J Cataract Refract Surg.
2008 May;34(5):835-41.

Chang DF, Campbell JR. Intraoperative floppy iris syndrome associated with
tamsulosin. J Cataract Refract Surg. 2005 Apr;31(4):664-73.

converting to ECCE

Conversion to ECCE often comes at a difficult time. The lens is about to fall south, the vitreous has prolapsed and the surgeon is stressed. 

Understanding the steps and process of conversion to ECCE is essential and study before the crisis will help soothe the stress when this inevitable process occurs. We will cover several areas: identifying patients at risk for the need for conversion to ECCE, indications for conversion, conversion from topical to sub-tenon’s, wound preparation, expressing the lens material, closure of the wound, placement of the IOL, post operative issues and a brief section on anterior vitrectomy. For more detailed instructions please refer to: http://webeye.ophth.uiowa.edu/eyeforum/tutorials/Cataract-ECCE/Cataract-Surgery-Complex-Conversion-Extracaps-ECCE.htm

One of the most important parts of the pre-operative process for cataract patients is to assess the difficulty factors that may lead to conversion to ECCE or otherwise complicate the procedure. You may want to add operative time to your schedule or ask for additional equipment. You may want to change to a superior limbal wound which facilitates conversion to an ECCE rather than a temporal clear corneal incision. You may want to do a retrobulbar block rather than topical anesthesia as the case may last longer or is more likely to become complicated. Or you may want someone more experienced to do the case. for more detail on dkifficulty factors please see: http://www.medrounds.org/cataract-surgery-greenhorns/2005/09/chapter-1-assessment-difficulty.html

Conversion to ECCE is indicated when phacoemulsification is failing. Sometimes this is due to a very hard lens which does not submit to ultrasound or a lens that is hard enough that the surgeon is concerned that the required ultrasound energy will harm a tentative cornea, e.g. Fuchs’ endothelial dystrophy or posterior polymorphous dystrophy (PPMD). Sometimes one will convert to ECCE when an errant capsulorhexis goes radial especially with a hard crystalline lens when the surgeon is concerned that the risk of dropping the lens is too great with continued phacoemulsification. Rarely now with Trypan Blue dye, a surgeon will choose to convert to ECCE when the anterior capsule is hard to see and capsulorhexis must be completed with the can opener technique. More often the conversion is indicated when the crystalline lens is loose from weak zonules or a posterior capsule tear which make phacoemulsification less safe than extending the wound and removing the residual lens material. Indications for conversion to ECCE include: Hard crystalline lens or unstable endothelium, Radial tear in anterior capsule with hard lens, Poor visualization despite Trypan dye,

Posterior capsular tear, and Zonular dialysis.

Converting to subtenon’s anesthesia. Often we convert cases from topical clear corneal to ECCE. While the ECCE can be done under topical it is usually more comfortable and safer to give additional anesthetic which is typically a sub tenon’s injection of bupivicaine and lidocaine. This will provide some akinesia and additional anesthesia. There is usually subconjunctival hemorrhage and if the injection is made too anterior it can cause chemoisis and ballooning of the conjunctiva. The steps of the sub tenon’s injection are shown in the video below(1):

A major decision step when converting to ECCE is to either extend the existing wound or close and make another. The ECCE will require a large incision of from 9-12 mm which is closed with suture. The decision to extend the existing wound or make a new wound hinges on several factors: location of the original wound, size of the brow, past surgical history, and possible need for future surgery.

Making a new incision during conversion is identical to that for a planned ECCE. The original incision is closed with a 10-O nylon suture. The surgeon and microscope are rotated as the surgeon should sit superior. The steps to make a new superior incision are:

• Conjunctival peritomy of about 170 degrees
• Use 64 or crescent blade to make limbal groove with a chord length of 11mm
• Bipolar cautery for hemostasis
• Use keratome to make initial incision starting in groove into AC
• Extend initial incision to full length of groove (with scissors or knife)
• Safety sutures are preplaced usually 7-O vicryl

Extending an existing incision can be tricky and the technique is different for scleral tunnels compared to clear corneal incisions. However in both cases the original extension is brought to the limbus. In the case of an original scleral incision the incision is brought anterior to join the limbus on either end before extending along the limbus for a chordlength of about 11mm. In the case of an existing corneal incision the corneal incision is brought posterior toward the limbus before extending the wound along the limbus for a chord length of about 11mm. When iris hooks are being used in a diamond configuration the wound can be extended to preserve the sub-incisional hook and the large pupil(2). The steps include:

• Conjunctival peritomy of about 170 degrees,
• Use 64 or crescent blade on either side of the existing wound to make a limbal groove with a chord length of 11mm
• Bipolar cautery for hemostasis
• Use Crescent to bring existing scleral wound anterior or existing corneal wound posterior to join limbus
• Extend initial incision to full length of groove (with scissors or knife)
• Safety sutures are preplaced usually 7-O vicryl.

One has to be far more careful when removing the nucleus during the typical conversion to ECCE which comes along with vitreous loss. First the anterior capsule must be large enough to allow the nucleus to express which may require relaxing incisions in some cases. When the zonules are weak or the posterior capsule is torn the lens cannot be expressed with fluid or external pressure as is often done with a planned ECCE with intact capsule/zonlules. After any vitreous is removed, the lens must be carefully looped out of the anterior chamber with minimal pressure on the globe. If the posterior capsule and zonlues are in tact than the lens can be expressed as described with a planned ECCE.

Placement of the IOL IOL selection with ECCE conversion depends on the residual capsular complex(3,4). The key to IOL centration is to get both of the haptics in the same place: either both in the bag or both in the sulcus.

When the posterior capsule is intact following a conversion to ECCE the anterior capsular opening is usually poorly defined which can make bag placement difficult. If the anterior capsule and thus the bag is well defined, then place a single piece acrylic IOL without folding it directly and gently into the bag using kelman forceps.

When the posterior capsule is intact and the anterior capsule is poorly defined then place a 3 piece IOL in the sulcus such as a large silicone IOL or the MA50 acrylic by placing these directly and unfolded into the sulcus with kelman forceps. Make sure that both haptics are in the sulcus.

When the posterior capsule is damaged, if enough anterior capsule and posterior capsule is left to support the IOL, define the sulcus with viscoat and place the IOL directly in the sulcus. Make sure both haptics are in the sulcus. If the IOL does not seem stable then place McCannel sutures to secure the IOL to the iris or remove and replace with an AC IOL (don’t forget to place a PI with vitrector).

When the capsule is severly damaged and cannot support an IOL then place the IOL in the anterior chamber. Use kelman forceps to place the IOL, then secure the chamber, and use a sinsky hook to place the AC IOL into its final position. (don’t forget to place a PI with vitrector).

Postoperative care for patients following conversion from phaco to ECCE is a bit more complicated and focuses on preventing cyctoid macular edema and limiting induced astigmatism. Often the care is very similar to that of a planned ECCE with about 3 post operative visits one the same day or next, one a week later, and one about 5-6 weeks later. Depending on the amount of astigmatism the patient may require several visits to sequentially remove sutures to eliminate induced astigmatism.

References

1. Oetting, TA, Cataract Surgery for Greenhorns, Available at http://medrounds.org/cataract-surgery-greenhorns.%20accessed%20September%209, 2007

2. Dupps WJ Oetting TA, Diamond iris retractor configuration for small-pupil extracapsular or intracapsular cataract surgery. J Cataract Refract Surg Vol 30(12):2473-2475

3. Chang DF, Oetting TA, Kim T, Curbside Consultations in Anterior Segment Surgery, Slack Inc, Thorofare NJ, 2007

4. Henderson BA, Essentials of Cataract Surgery, Slack Inc, Thorofare NJ, 2007

operating microscope basics

It is very important to learn how to operate the microscope before your first day in the OR.

Basics of the Microscope pedal.  While there are some subtle variations among models and manufacturers the basics of the microscope footpedal and operation of the micropscope are similar.  The microscope has a starting XY position which is centered at the start of the case and then small variations in this initial position are made using the foot pedal which makes small XY adjustments of the microscope.  The scope also has a starting focal point (i suppose this is the Z position) which is set up at the start of the cases and small variations from this are made during the case using the foot pedal which moves the focal point of the scope up and down.  Often the intensity of the light can be also be controlled with the foot pedal.

All of your extremities will be busy:  one foot for the microscope pedal, one foot for phaco pedal, one hand for the phaco handpiece, and the other hand for the chopper.  Most surgeons use non dominant foot to control the microscope pedal.  unless you are a soccer player your left foot is probably not that coordinated.  as such you should practice using the pedal way before your first case.  most people take off their shoes so that they can feel the microscope pedal better.

Foot pedal switches.  The typical positions of the microscopes foot switch controls are shown below.  The foot pedal is designed so that the foot can sit on a rasied foot rest.  A rocker swith in front of the foot rest is most important and moves the scope up and down to make small changes in focus.    a rocker switch behind the foot rest controls the zoom or magnification.  the magnification is typically low during wound construction and is increased during steps such as capsulorhexis which require more magnification.  Several inches in front of the foot rest is the joy stick which controls the XY position of the scope.  both the XY position and the focus shuold be centered prior to the case (usually a switch on the scope) and manually put into optimal initial position to allow maximal excursion of these functions during the case.


When you arrive in the OR ask yourself: “where will I be sitting?   Are you operating from a superior approach -- Superior approach is preferred when you may have a large incision with lots of sutures (eg. ICCE, ECCE, tough phaco when you may convert) and/or when you may have iris trauma (tolerated better under the lid) and when you are doing a trabeculectomy and want the bleb under the lid. Typical phaco is from a temporal approach to avoid the brow. i usually do rights eyes a bit inferior and temporal (eg 8 oclock) and left eyes superior andtemporal (eg 2 oclock); however. some surgeons like Dr Tim Johnson are always true temporal whether operating on the right or left eye. 

  

Proper Sequence to adjust Equipment to your body

1.     Place retrobulbar block first (give it time to work while setting up scope)

2.     Put assistant’s eyepiece and camera on proper side of microscope

3.     Push center focus and center XY position buttons on microscope (may be same button)

4.     Adjust ocular inter-pupillary distance and zero both objectives

5.     Lower surgeons chair

6.     Raise bed height to just allow both feet under bed onto both pedals

a.     Dominant foot – phaco pedal

b.     Non dominant foot microscope footswitch

c.     Take off shoes (wear white Nike crew length socks)

7.     Manually move entire microscope (not footswitch) so that you are in focus

8.     Raise surgeon chair height enough to allow surgeon to see comfortably into oculars

9.     Prep and Drape

 

staining the vitreous with kenalog

One of the trickiest parts of an anterior vitrectomy is seeing the vitreous.

You can often see the nearly invisible vitreous strands pushing another structure aside or detect that the vitreous has occluded an I/A aspiration port. However directly seeing the vitreous is difficult. Scott Burk at Cincinatti Eye helped to solve this problem with his description of using Kenalog (off label) to stain vitreous that had prolapsed into the anterior chamber (ref below). As Kenalog is not approved by the FDA for this indication and as some retinal surgeons have had sterile and even infectious endophthalmitis from using Kenalog its use is controversial. However it is a very useful adjunct to anterior vitrectomy. For more detail on vitrectomy pls see: http://www.medrounds.org/cataract-surgery-greenhorns/2005/10/chapter-5-managing-surgical.html or the section in this blog.

Dr Burk described a process to wash the preservative off of the Kenalog to use in the anterior chamber. His process dilutes the 40mg/ml Kenalog 10:1 and washes off the preservative with a filter. I have summarizied the steps of his technique below and show the technique in the video. Please keep in mind that this is not approved by the FDA for this technique and does carry some risk of TASS (sterile anterior chamber inflamation) and of endophthalmitis.   you can also use the preservative free kenalog which is now available and dilute it 10:1 which although more expensive is easier and is approved for intraocular use.

Preparing the Kenalog Stain

• TB syringe to withdrawn 0.2 ml of well shaken Kenalog (40mg/ml)
• Remove the needle and replace with a 5 (or 22) micron syringe filter (Sherwood Medical)
• Force the suspension through the filter and discard the preservative filled vehicle
• The Kenalog will be trapped on the syringe side of the filter
• Transfer the filter to a 5 ml syringe filled with balanced salt solution (BSS)
• Gently force the BSS through the filter to further rinse out preservative
• Repeat rinsing a few times
• Place a 22 gauge needle on the distal end of the filter
• Draw 2 ml of BSS into the syringe through the filter to resuspend the Kenalog
• The Kenalog (now without preservative and dilute 10:1) will stain vitreous strands white

one of the nice things about the kenalog stain is that you can better understand the fluid dynamics of vitreous removal.  you can see the vitreous streaming around the cutter with a leaking wound.  you can see the vitreous heading better toward the cutter if you hold the cutter low and the irrigation cannula high.  here is a video showing these principles. 

References

Burk SE, Da Mata AP, Snyder ME, Schneider S, Osher RH, Cionni RJ. Visualizing vitreous using Kenalog suspension J Cataract Refract Surg. 2003 Apr;29(4):645-51

Burk, SE, Question 32: When and How Do I Stain the Vitreous With Intracameral Kenalog? from Chang DF, Oetting TA, Kim T, Curbside Consultations in Anterior Segment Surgery, Slack Inc, Thorofare NJ, 2007.