This write up is based on my own learning experience over many years and what I have observed while training fellows. This also includes the common mistakes that I have made and what the fellows make during the training process.
Today with micro incisional vitreous surgery (MIVS) and better fluidics, learning basic Vitrectomy is a very quick process for most trainees. I will now enumerate 10 steps which may be useful for a beginner.
Pre-operatively assess the eye to be operated. Is it the right eye or the left eye I am going to operate? Is it a sunken eye placed in a deep socket? It is more easy to operate the right eye because the dominant right hand performing most of the manoeuvre has a wide field of action. The same is not true for the left eye where the movement of the dominant right hand may be restricted because of the brow and the nose. This becomes even more pronounced in a deep-set eye. Therefore your nasal sclerotomy in the left eye should be about half clock hour towards the 12 O’clock from where we normally place the sclerotomy. This makes a lot of difference and eases the manoeuvres like membrane peeling and ILM peeling. This is a very important step.
Look at the lens and decide on combined surgery in certain situations. Presence of a small central spec of posterior cortical cataract, which sometimes we feel may not be of any significance can act as an impediment especially in cases of vitreous surgery for PDR where there are membranes in the posterior pole that needs careful dissection. Similarly, peripheral cortical cataractous changes that come as multiple spokes can make peripheral skirting and base vitrectomy difficult and incomplete.
In a combined surgery after the cataract surgery and IOL placement is over, look at the cornea. If there is significant epithelial and stromal edema, visualization will become very difficult and in case it is a complex vitreous surgery it may be judicious to perform a two-stage procedure.
Placement of the Infusion cannula: Today with MIVS there is the freedom to make as many ports as required. It is a simple process. Always before you start the vitrectomy, check whether the infusion port is inside the vitreous cavity. In a deep-set eye and in any eye where the pupillary dilation is not good you may have to bend tangential to the eye to visualize better or in a pseudophakic eye, you can hold the edge of the infusion cannula outside and bend it forward to visualize better.
Two clinical situations you need to check the infusion cannula carefully before you begin Vitrectomy:
- Eyes with bullous retinal detachment
- Presence of choroidals
If there is a bullous retinal detachment in the temporal quadrant I sometimes prefer to keep an additional port in the inferonasal quadrant. Similarly in the presence of choroidals if there is a quadrant free of choroidals I would prefer to place the infusion cannula in that quadrant. Lastly, in a situation like this, I would prefer to use the longer cannula in the MIVS.
Posterior vitreous detachment induction. This is the most important step in a case of simple vitrectomy for macular holes, epiretinal membranes etc. Following are the steps for a safe PED induction:
- Check the fine focus of the operating microscope before you start inducing posterior vitreous detachment.
- Adjust the magnification so that it is neither too much or too little. The idea is to get good depth perception.
- Good visualization is mandatory and irrigates the cornea well.
- Start in the nasal quadrant because it is safe.
- Hold the cutter close to the surface of the retina and activate the suction to the settings (350mm) and gently and slowly slide the cutter from the edge of the optic disc into the inferonasal quadrant on the surface of the retina towards you.
- The cutter should be very close to the surface of the retina. It should slide over the surface so that the posterior hyaloid holds to the port of the cutter and it is a sliding movement.
- A common mistake made by beginners is after applying the suction by placing the cutter at the margin of the optic disc the beginner lifts the cutter up immediately. This should not be done. He has to slide it gently on the surface so that the posterior cortical vitreous and the hyaloid is detached from the edge of the optic disc and then raise the cutter from the surface of the retina.
Use of Triamcinolone: Intraoperative use of triamcinolone is very useful both for performing posterior vitreous detachment and identifying the posterior cortical vitreous. There are a few important tips or take-home points when using triamcinolone.
- Dilute the triamcinolone so that it just smears the vitreous, this is very important. Never use it undiluted.
- Inject a small quantity, don’t inject too much so that the posterior pole becomes invisible.
- Place the cannula just inside the vitreous cavity and inject it. The purpose is to stain the vitreous and not the retina.
- Don’t carry the cannula right over the optic disc and posterior pole
- Be very gentle when you inject
- Once you have injected the triamcinolone it stains the posterior cortical vitreous. Remove the posterior cortical vitreous first with the cutter. This makes the PVD induction easier. Subsequently, make sure when you start inducing PVD that the underlying retina is visible and you have assessed the depth of the instrument.
- Inadvertent touch on the retina with cutter can result in retinal tear and avulsion of the retinal vessels resulting in bleeding.
Peripheral hyaloid separation: Sometimes the peripheral hyaloid may be adherent at the equator and beyond esp. in the inferior quadrant. How to tackle this?
- Try to lift it from one end, it may just peel off
- Use additional triamcinolone to stain the vitreous and proceed with vitrectomy. This may lift the posterior hyaloid and facilitate the process.
- Attempts to lift the posterior hyaloid from the vitreous base can be tried judiciously but care should be taken to avoid large retinal breaks.
Prevention of lens touch: This is very important and this is the most common mistake performed by trainees. When does it happen?
Most often, when performing vitrectomy in the opposite quadrant where the shaft of the vitrector goes across to the opposite quadrant and removing the peripheral vitreous. How to prevent it?
- Be aware of the possibility of lens touch when performing certain manoeuvres.
- If you are using a non-contact wide angle lens increase the distance between the eye and the non-contact lens. This allows visualization of the posterior capsule and anterior vitreous.
- Keep an eye on the shaft of the cutter when performing manoeuvres in the opposite quadrant.
- Depress the ora serrata from outside when performing peripheral excision.
- Be more careful especially when the pupillary dilatation is not good because part of the lens is not visible for you.
Eye with dense vitreous hemorrhage: In an eye with dense vitreous hemorrhage you may have the following problems:
The infusion cannula after insertion may not be visible, because of the presence of thick blood just behind the lens. How do you manage this?
First, perform a two-port vitrectomy of the anterior vitreous with the cutter in one port and the infusion in the other port holding the infusion in your hand through a 25 gauge bent cannula. With this two-port vitrectomy you remove all the blood that is just behind the lens and also in the region of the port. This will definitely help you to visualize the infusion cannula inside the vitreous cavity before you proceed further.
Use of chandeliers: Placement of a chandelier through an additional port is another important step that you need to take in certain specific situations especially in eyes where you feel there may be a need for bimanual dissection or any form of bimanual maneuvers. This may happen in eyes with an intraocular foreign body where you may have to use a two-hand technique to remove the IOFB, removal of dense adhesions in case of proliferative diabetic retinopathy or in cases of complex retinal detachment where you may have peripheral membranes which are adherent to the retina and it may require bimanual maneuvers. Also, chandelier illumination improves visualization in the vitreous cavity and it may also be useful in certain specific cases like dense vitreous hemorrhage where an additional illumination system in the early part of the vitrectomy helps you to understand the morphology and the anatomy better.