Anterior Vitrectomy

This tutorial has been adapted from Dr. Tom Oetting's Cataract Surgery for Greenhorns blog and is shared here with his kind permission.

Vitreous can be very difficult for the anterior segment surgeon. When it presents, we can be tempted to take short cuts which can lessen the safety of our surgery. Being prepared is your best defense and here I will present a few tips based on my experience with the vitreous.

The cause of vitreous prolapse in your case is important as it may guide your surgical reatment and Intraocular lens (IOL) location. A capsular tear can cause vitreous prolapse, with an anterior tear extending posteriorly probably being most common. Primary posterior tears from the phaco needle being too deep or from a strike from the I/A device or another instrument are also common. It is best to find a cause which does not involve the surgeon such as a tear extending from a preexisting weakness from a posterior polar cataract, iatrogenic (different surgeon) from pars plana vitrectomy, or from penetrating lens trauma. Besides tears zonular dialysis can lead to vitreous prolapse and can come from your surgery with forceful rotation or pulling on the capsule with the I/A or from pre-existing conditions such as trauma, pseudoexfoliation, or Marfan’s Syndrome.

For me the first sign of vitreous prolapse is denial. I begin to think that something is not right but try to find lots of reasons why everything is really OK. More objective signs of vitreous loss are the chamber suddenly deepens, the pupil widens, the residual lens lens material is no longer centered or doesn't spin, lens particles no longer come to the phaco needle, and a big sign would be lens particles sink to the back of the eye.

3 basic principles of vitrectomy are to (1) go bimanual with separate irrigation and cutting devices, (2) close the chamber, and (3) cut low and irrigate high. If you follow these three principles you can keep most of the vitreous out of the front of the eye and away from the wound, iris, and cornea where it can cause so much trouble. Most importantly, you can help to limit the amout of vitreous expression and its risk of retinal detachment.

• Go bimanual with separate devices for irrigation and cutting is fairly easy now as most machines will allow this or assume it from the start. Some machines such as the Alcon 10,000 had a coaxial device and you had to remove a sleeve to make it bimanual. I like to use a 23-gauge cortex extractor cannula to irrigate, with the cutter usually in my dominant hand.
• Close the chamber so that no fluid can get out with the vitrectomy instruments in the eye. This will typically require you to close your main incision and add a paracentesis if you are doing traditional coaxial phaco. Through one paracentesis, you will place your irrigation cannula, and through another larger paracentesis you will place your vitreous cutter/aspirator. If you use a 3.0 mm or similar phaco wound for the vitreous cutter apsirator, the chamber will not be controlled and fluid and vitreous will stream through this wound around the cutter. You need to make the area of least resistance for any fluid or vitreous to leave the eye be the aspiration/cutter device. See the video showing the importance of closing the chamber to control the flow of vtreous.

[video] (opens video in external player)

• With control of the chamber and bimanual instruments you can cut low and irrigate high. You will want to have the cutter/aspirator low to get at the root of the vitreous while irrigating high in the closed chamber to create a fluid pressure differential to push the vitreous toward the cutter. If you irrigate in the area of the cutter/aspirator you may push the vitreous away from the cutter and even worse more anterior toward the wound. In this video you can see the use of the three principles to remove the vitreous and some residual cortical material.

[video] (opens video in external player)

There are 3 basic phases in the case when vitreous presents: (1) early in the case with most of the crystalline lens in the eye, (2) with only some cortical material left (most common), and (3) while placing the IOL.

When vitreous presents early during nucleus removal, clean up is the most difficult. The vitreous is often entwined in the nuclear pieces. It can be very difficult to get posterior enough with the cutter to cut off the vitreous at its source with all of the nuclear pieces in the way; and most importantly, it is hard to not bump the pieces through the capsular tear to fall south into the back of the eye. You have a big decision to make right up front: convert to ECCE or not. If the nucleus is hard and mostly in one piece I would strongly consider converting to a large incision ECCE. The video below outlines the issue with conversion to ECCE and the steps are listed below:

• If topical, do subtenons injection
• Close temporal incision and create standard ECCE superiorly (or extend existing wound)
• Have Wescott scissors ready when looping out lens to cut vitreous
• Close with 2 vicryl safety sutures
• Anterior vitrectomy, Weck cell vitrectomy
• Dry removal of residual cortical material with syringe on 27-gauge cannula
• Use J-cannula if needed for subincisional material
• Consider staining with preservative free dilute kenalog
• Place IOL if possible in sulcus or anterior chamber (AC)—if AC, don’t forget peripheral iridotomy
• Miochol to bring pupil down—seats sulcus IOL, peaked pupil helps to detect vitreous

[Video] (open video in external player)

Sometimes even with early loss of vitreous with nuclear material left you can carefully proceed with phacoemulsification. The key is to provide some separation between the space with vitreous and the area of phacoemulsification. The pace is slowed down with a low bottle height and low vacuum (Osher slow motion phaco). Here are the steps:

• Seal off capsular hole with liberal use of Viscoat (cohesive OVD will not work)
• Keep phaco occluded in the lens as much as possible to avoid pulling on the vitreous
• Lower the vacuum and bottle height
• Consider using a sheets glide to seal off hole—trap nucleus in AC
• Work with one or two large pieces (rather than chopping into many small bits that can more easily fall south

The most common time for vitreous is while removing the last bit of nuclear material or during cortical removal. The main emphasis during this phase is to remove any residual cortical material following vitrectomy. Loss of small amounts of cortical material to the back of the eye or leaving small amounts in the anterior segment will often present no difficulty. Preserving capsule for lens placement in the sulcus is important also. The steps when vitreous comes in this phase are:

• Place Viscoat in area of tear or dialysis before removing instruments
• As always, split into irrigating cannula (eg. 23g. cortex extractor) and the vit cutter (w/o sleeve)
• Suture wound and use two paracenteses one for the cutter and one for irrigating cannula
• Irrigate high and cut/suck low – creates a pressure gradient to push the V back
• Settings low vacuum 100 range, low bottle height 50 range, max cut rate
• Dry removal of residual cortical material with syringe on 27-gauge cannula
• Use J-cannula if needed for subincisional material
• Consider staining with Kenalog (see below)
• Place IOL if possible in sulcus (see video below) or AC (if AC don’t forget peripheral iridotomy)
• Miochol to bring pupil down

[Video] (open video in external player)

[Video] (open video in external player)

The least common time for vitreous is while placing or just after placing the IOL. Usually in this phase, very little vitreous comes forward. The main issues surround the IOL. Will it be stable in the bag or should the IOL (or often an appropriate IOL) be placed in the sulcus? Here are the steps for dealing with vitreous in this phase and a video showing this situation:

• Stabilize the IOL by placing one haptic out of the wound or in the AC
• Anterior vitrectomy as described above—attempt to get the cutter below the IOL
• Place both haptics in the sulcus if possible (cannot use SA60 in sulcus consider alt fixation)
• Use Weck cell sponge to ensure wound is clear
• Consider stain
• Miochol to check pupil

[Video] (open video in external player)

Most patients who have an anterior vitrectomy do very well. It is important to be honest with the patient about what happened. I usually tell them:

"The thin membrane that surrounds the cataract tore during surgery. I had to take some extra time to remove the gel from the back of the eye. I was able to remove all of the cataract and place the artifical lens. I think everything is going to be great but I will have to watch you a little more closely for a while."

In summary, the most important thing to remember with anterior vitrectomy is to control the chamber and use bimanual instrumentation.

Thomas A. Oetting, MD, July 19, 2009

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