- Truncation: To relieve all the surrounding traction 360 degree
- Segmentation: Dividing a larger membranes/FVP into smaller islands of FVP by 360-degree truncation around them.
- Delamination: Separation of these membranes/FVP from the retinal surface to which they are firmly adherent by creating a plane of dissection between them.
Pearl #1 When not to perform vitrectomy in diabetic retinopathy?
Answer: In cases of extramacular tractional retinal detachment (TRD) when the fovea is attached and the patient has a comparative good vision the extramacular TRD can be observed. Charles and Flinn reported only 21% of extramacular TRD extending into macula without any surgical intervention. Also, DRVS (Diabetic retinopathy vitrectomy study) reports that only 23% of eyes with TRD developed severe visual loss at 2 years. Also, early intervention in such extramacular TRD’s can sometimes lead to more harm than benefit owing to the surgery itself.
Pearl #2 First step should always be core vitrectomy followed by finding a plane in posterior hyaloid to perform truncation vitrectomy to relieve the anteroposterior traction as much as possible. In such a way the anteroposterior traction is relieved and inadvertent break formation can be avoided. Once you find a plane of truncation always keeps the cutter under that plane to avoid any unnecessary traction. In areas where truncation is not possible should be left in situ and should be dealt with later in an inside out approach with the help of segmentation. Always remember only use the cutter when you are under the membrane and above the retina (in between the membrane and retinal surface), life the membrane a bit, and then cut.
Pearl #3 After segmentation of a membrane if there is no surrounding traction on the retina the membrane can be left in situ but if there is traction and you are not able to find a plane to enter your vitrectomy cutter between the FVP and retinal surface the best approach is to either do a bimanual vitrectomy wherein after putting a chandelier illuminator and with the help of scissors and forceps a plane is created. This is also called as Delamination. With the help of scissors often a plane is created and those membranes can be removed again by segmentation and delamination.
Pearl #4 Sometimes during membrane removal by using forceps when a plane is achieved and the membrane is getting peeled off easily a lot of small bleeders can be identified. In the awe of peeling membranes, one tends to ignore these bleeders, later these bleeders can lead to the formation of larger clots that are difficult to remove, and in process of clot removal, it may lead to the formation of multiple breaks. In such a scenario, bleeders should be cauterized as and when identified, avoid excessive cautery and if excessive cauterization has been done they should be lasered after the fluid air exchange. During laser take care to clear the blood around the break otherwise the blood may absorb the laser energy which will not be transmitted to the underlying RPE.
Pearl #5 In cases of diabetic retinopathy a pre-op OCT should always be asked to understand the level of posterior hyaloid separation, to understand the presence of the second membrane, and also to look for the level of detachment. A pre-op helps you to better plan your surgical approach. It helps you to plan the starting point of your membrane dissection from an area where the separation of posterior hyaloid is maximum from the underlying retinal surface.
Pearl #6 Thin or fine membranes should be peeled off using an ILM forceps or an End grasping forceps whereas Thicker or heavy membranes should be peeled off using a Maxigrip or a Serrated forceps. Additionally sometimes in cases of taut posterior hyaloid when there is no point of entry between the retina and overlying membrane these ILM forceps can be used to make an opening in posterior hyaloid where it is seen separated from underlying retina.
Pearl #7 Tackling bleeding from the vessels over the disc: Peeling of the membranes over the disc is relatively easy due to the absence of ILM but inadvertent peeling can lead to torrential hemorrhage which is rather difficult to stop. In such cases the bleeding can be tackled by the following measures:
- Raising the infusion pressure above 60-70 mm of hg for a short period until a clot is formed. The important point to remember is that the clot should then not be engaged to avoid any rebleed
- Injecting PFCL: PFCL being a heavy density liquid helps in controlling the hemorrhage and formation of a blood clot.
Pearl #8 If a retinal break is encountered during the membrane peeling and the corresponding area is still not free from traction the membrane peeling in such areas should be advanced very cautiously to avoid enlargement of the preexisting break or creation of a new break. The direction of peeling now should be towards the break and not away from the break, as the retina is already thin and ischemic any traction pulling the break may lead to its enlargement.
Pearl #9 In case a retinal break has happened during membrane peeling, it is always better to put silicone oil than intravitreal gas. But if there is no break than it is always better to put gas or air.
Pearl #10 In case of a one-eyed patient while performing diabetic vitrectomy following points should be kept in mind
- Always operate early in cases of non-resolving vitreous hemorrhage
- Always use silicone oil as a post-operative tamponade agent in such patients for the below-mentioned reasons:
- The patient will be able to see early in the postoperative period as compared to gas or air where post-operative vision will be poor for a long period.
- If rebleed occurs it will be limited and under oil and will not cause the patient to loose vision.