What Is Pars Plana Vitrectomy?
Pars plana vitrectomy, or just vitrectomy, is a surgical procedure that allows entry into the vitreous cavity and the posterior component of the eye. The vitreous cavity contains vitreous humor gel, which is removed to gain a better approach to the retina. Vitrectomy helps bring back vision and enhances the quality of life in patients with vitreoretinal diseases. However, it is a highly skilled technique requiring sound technical knowledge, which may lead to certain complications. By following the correct surgical method, the incidence of complications is low, otherwise may result in critical morbidity and blindness.
In certain rare cases, such as eye trauma; surgeries of complex cataracts, cornea, or glaucoma; or due to lens issues, the vitreous humor leaks into the anterior chamber of the eye through the pupil. An anterior vitrectomy is performed to avoid and decrease the risks of other serious conditions and for visual recovery.
What Are the Indications for Pars Plana Vitrectomy?
The indications for pars plana vitrectomy include:
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Vitreous opacifying pathologies like non-clearing vitreous hemorrhage seen in proliferative diabetic retinopathy, posterior vitreous detachment, trauma, retinal detachment, intraocular tumors, and retinal vascular diseases.
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Rhegmatogenous RD (retinal detachment): It occurs when the vitreous fluid enters the subretinal space due to past retinal breaks or tears.
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Retinal tractional forces that cause vision deformity. The epiretinal membrane can form in conditions like retinal vascular disease, uveitis, laser therapy, retinal breaks, or due to idiopathic reasons.
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Macular holes, present as a break or tear in the macula. They are most commonly seen due to aging. Still, they can occur in diseases like diabetic retinopathy, trauma, and fibrovascular diseases causing retinal scarring. In advanced cases of fibrovascular diseases, tractional RD is accompanied by rhegmatogenous RD.
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Submacular hemorrhage, as in age-related macular degeneration.
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Notable ocular trauma resulting in vitreous hemorrhage, particularly due to an intraocular foreign body.
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Intraocular inflammation, as seen in post-traumatic endophthalmitis, bacterial or fungal endophthalmitis.
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Diagnostic procedure for persistent or idiopathic intraocular inflammation, done after required laboratory investigations.
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Implantation of intraocular drug agents like Ganciclovir or Fluocinolone implants.
Some rare indications of PPV are retrieval of retained lens fragments post phacoemulsification, endoresection of intraocular tumors, tumor biopsies, and the recently added gene therapy.
What Are the Contraindications of Pars Plana Vitrectomy?
Though there are no absolute contraindications to pars plana vitrectomy. However, it may not be favorable in patients with notable systemic comorbidities. The only relative contraindication is in cases of intraocular tumors for their diagnostic involvement, which varies from case to case.
What Are the Complications of Pars Plana Vitrectomy?
The complications of pars plana vitrectomy can be divided as follows:
During Surgery:
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Iatrogenic (caused by medical treatment procedures or blood vessel injuries).
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Iatrogenic retinal breaks or tears predisposing to retinal detachment.
Early Postoperative Period:
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An immediate increase in intraocular pressure.
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Corneal epithelial defects.
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A vitreous or choroidal hemorrhage.
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Central retinal artery occlusion.
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Cystoid macular edema.
Middle Postoperative Period:
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Endophthalmitis causing ocular pain, decreased vision, red-eye, and hypopyon. It is regarded as an ophthalmic emergency requiring urgent treatment.
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Iris neovascularization, neovascular glaucoma, and raised intraocular pressure, mainly due to diabetic retinopathy.
Late Postoperative Period:
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Cataracts.
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Anterior chamber narrowing and secondary glaucoma.
Infection and hemorrhage are other common complications of pars plana vitrectomy.
How Is Pars Plana Vitrectomy Done?
A vitreoretinal surgeon usually performs the surgery. However, in cases of complications and underlying causes like trauma, other healthcare professionals can be added. For trauma-related injuries, according to the repair needed, specific ophthalmic surgeons may be included. To settle an increased intraocular pressure, a glaucoma specialist is required. An oculoplastic surgeon or ocular oncologist may be necessary in intraocular tumor cases.
The surgery may come as an emergency or can be planned; accordingly, preparations are made. Generally, it is performed as an outpatient procedure and may require one to three hours. A complete ophthalmic examination is carried out with indirect ophthalmoscopy, disclosing the structures involved. Ultrasonography of the vitreous and the eye's retina is required if opacities hinder a clear retinal view to reveal vitreal and retinal detachments. These investigations help determine the procedure's urgency and the treatment method to be used.
As a preoperative measure, eye dilation is required. The surgery can be performed under general anesthesia or local anesthesia as a peribulbar block, retrobulbar block, and eyelid block. The surgeon begins by making several small incisions into the sclera (outer white layer of the eye) at the two o’clock, ten o’clock, and inferotemporal regions, approximately three to four millimeters from the corneal limbus. Trocar and cannulas are inserted through these cuts to get a better view, followed by an examination of the vitreous humor. In macular pathology cases, an additional contact lens is placed on the cornea for fundus visualization. The surgeon accesses the vitreous cavity through an area known as the pars plana. Hence, the procedure is named after it.
Depending on the cause of the vitrectomy, several intraoperative steps are followed. Initially, the core vitreous is removed. However, a posterior vitreous detachment (PVD) can be made, and steroids may be used to view the posterior pole. The peripheral vitreous can be removed easily, or the scleral indentation technique can be utilized. A thorough envisioning of the entire retina is done to look for any holes, tears, breaks, or detachments. The sclerotomy sites are also scrutinized to prevent retinal breaks of unknown causes that may later result in retinal detachment.
This completes the main procedure of vitrectomy. Other supplemental surgical interventions are performed according to the pathology involved. For neovascularization, pan-retinal photocoagulation or intravitreal anti-VEGF injections are administered. In retinal detachment cases, the surgical steps vary based on the detachment type. Rhegmatogenous retinal detachment surgery includes the removal of subretinal fluid, sealing detachments with laser or cryotherapy, and adding gas or silicone to keep the attachment intact. Tractional retinal detachments involve the elimination of fibrovascular or epiretinal membranes and treating the traction tissue by delamination or segmentation.
In endophthalmitis (infection inside the eyeball), vitreous biopsy and intravitreal injections of antibiotics or antifungals are preceded by vitrectomy. When handling penetrating ocular trauma, repair of additional defects like corneal perforations, lens dislocations, etc., removal of intraocular foreign body, and treatment of retinal trauma are also required. Vitrectomy in ocular tumor surgery is followed by the sampling of the tumor by fine-needle aspiration, except for non-adhering tumors.
As all the therapeutic interventions of the vitrectomy get over, the cannulas and instruments are taken off the eye, and incisions are closed with sutures.
Conclusion
Vitrectomy recovery takes around two to four weeks, and getting normal vision back takes a bit longer. However, the surgery ensues in temporary after-effects, so adequate precautions and post-operative instructions must be followed religiously to avoid complications, along with regular follow-up visits.
