Dr. Georges Mollayess, MD
Chief of Ophthalmology | Monla Hospital, Tripoli, North Lebanon, Lebanon
Diabetic retinopathy (DR) is the leading cause of blindness among the working population in the developed world. It is classified into Non-proliferative phase and Proliferative phase. Diabetic Maculopathy causes decreased vision in both phases. Vitreous hemorrhage and tractional retinal detachment occur in the proliferative phase. Laser Photocoagulation and intravitreal injections of Anti-VEGF are the treatments for nontractional macular edema and vitreous hemorrhage (Figure 1 and 2). Patients with tractional macular edema caused by an epiretinal membrane, nonclearing vitreous hemorrhage and tractional retinal detachment need Pars Plana Vitrectomy.
Pars Plana Vitrectomy:
Pars plana vitrectomy (PPV) involves the removal of vitreous gel from the eye by introducing instruments via three ports. One port is used for an infusion line that maintains the eye pressure during the procedure while the two others are used to introduce the illuminating light pipe and the vitrector. Nowadays, it can be performed through small 27 Gauge (0.4mm) incisions that do not need suturing (Figure 3 and 4). Introduction of certain drugs, laser photocoagulation and temponading agents can be installed through the procedure. If there are retinal tears, temponading agents as Gas or Silicone oil can be used. If gas is used, the patient should avoid going to high altitudes as this increases the chance of raising the intraocular pressure and damaging the optic nerve. If Silicone Oil is injected, another surgical procedure should be performed to remove it after several months.
Indications for Pars Plana Vitrectomy:
1. Vitreous Hemorrhage:
The non perfused retina secrets Vascular Endothelial Growth Factor (VEGF) that induce growth of new vessels (neovessels) (Figure 5). These are fragile and grow towards the vitreous cavity. Any abnormal movement in the vitreous cavity or increase in HbA1C, blood pressure, sneezing, vomiting or coughing can lead to vitreous hemorrhage and loss of vision. Patient will start to see floaters that can enlarge gradually and cause total loss in vision. Vitrectomy is done for non resolving hemorrhage with fibrovascular traction and for faster visual recovery (Figure 6).
2. Tractional Retinal Detachment:
Fibrovascularmembranes that form the scaffold for the neovessels can contract and pull over the retina and detach it. The more time the fovea (center of vision) is detached, the poorer the visual prognosis. Through small gauge surgical technique, we are able to use the vitrector to cut, aspirate and dissect the tractional membranes (Figure 7).
3. Diabetic Macular Edema:
Diabetic maculopathy that is not responding to intravitreal injections or has a tractional element can improve with Pars Plana Vitrectomy (Figure 8 and 9). These patients usually have tight vitreous adherence to the retina. Removing the vitreous can improve oxygen delivery to the nonperfused retina. Macular edema will improve gradually with time. Sometimes vision can continue to improve over several months.
Complications of Pars Plana Vitrectomy:
Most patients who undergo vitrectomy may develop cataract over a period of months to years after. There is also a risk of developing retinal tears that will be treated during the operation. There is minimal risk –less than 0.5%– of endophthalmitis, or eye infection.