Vitrectomy pars plana

The pars plana vitrectomy is a microsurgical operation whose purpose is to remove the vitreous for better access to the damaged retina. Most often it is carried out through three separate holes in the pars plana.

Vitrectomy Objectives

• The excision of the posterior hyaloid membrane to the posterior boundary of the vitreous base in the eyes with retinal detachment is the most important task. The so-called "basic" vitrectomy, in which BMS and associated retinal membranes remain intact, is justified only in cases with endophthalmitis.
• Weakening of vitreoretinal traction by dissection of the auretinal membrane and / or retinotomy.
• Manipulation with the retina and adherence.
• Creation of space inside the vitreous cavity for the subsequent internal tamponade.
• A variety of purposes (depending on the case): removal of the vitreous vitreous body, cataracts, dislocated fragments of the lens or intraocular foreign bodies.

Indications for vitrectomy

Regmatogenic retinal detachment

Uncomplicated retinal detachment. Although scleral indentation is usually effective, primary vitrectomy is used more often because it has the following advantages:

• Fewer manipulations, as sometimes there is no need to perform scleral indentation.
• Cryo- or laser coagulation can be done after the retina is attached, which reduces the impact of destructive energy.
• Tamponade by one agent or another provides postoperative blocking of the retinal rupture from the inside.

Complicated retinal detachments, in which retinal ruptures can not be closed by the usual scleral indentation due to large size, with localization in the posterior pole and in combination with PVR.

Traction retinal detachment

With proliferative diabetic retinopathy, vitrectomy is indicated if the retinal detachment seizes the macula or threatens it; can be combined with internal panretinal laser coagulation. Combined tract-regmatogenic retinal detachment should be immediately operated, even if the macula is not involved, since it is possible for a very rapid leakage of subretinal fluid to the macula.

In case of penetrating injuries, vitrectomy is aimed at rehabilitation of vision and reduction of traction, predisposing to detachment of the retina.

Preparation

• the infusion cannula is placed in the lower sciatic anus at a distance of 3.5 mm from the limb;
• produce 2 additional sclerotomous orifices according to the meridians 10 and 2 hours, through which vitreotom and a fiber-optic tip are inserted;
• remove the posterior hyaline membrane and the vitreous in the center.

The dissection of membranes of the local folds of the retina is as follows:

• the end of the vertically cutting scissors is inserted into the membrane between two adjacent retinal folds, and the membrane is stretched toward the "dentate" line until it detaches from the retina surface;
• internal fluid-air exchange followed by retinopexy of retinal ruptures;
• the base of the vitreous is supported by a wide scleral seal;

Auxiliary retinotomy may be required after dissecting the membranes, if the retinal mobility is considered insufficient for adherence.

The excision of subretinal membranes may be required in certain cases.

Instruments

The tools are presented in the kit; in addition to vitreotom requires a number of other tools. The diameter of the axis of most instruments is the same size, which makes it possible to interchange them and enter through the sclerotomous hole,

• Vitreotom has an internal blade-guillotine, which vibrates at a speed of 800 times / min.
• Intraocular lighting is provided by a fiber optic tip.
• Infusion cannula.
• Additional tools are presented with scissors and tweezers, an outflow needle, an endolaser and an indirect ophthalmoscope.

Substances for tamponade

The ideal substance must have a high surface tension, be optically transparent and biologically inert. In the absence of such an ideal substance, the following substances are currently used.

Air is used most often, in uncomplicated cases it is usually quite adequate. It is more accessible, but must be filtered to remove microorganisms. The main disadvantage is its rapid resorption: for example, 2 ml of the vesicle dissolves within 3 days, whereas the chorioretinal fusion caused by laser or cryocoagulation occurs about 10 days.

Expanding gases are preferred in complicated cases requiring a prolonged intraocular tamponade. The duration of the preservation of the vesicle in the eye depends on the concentration of the gas and the volume introduced. For example:

• Stabilization of the posterior parts of the retina during dissection of epiretinal membranes in the eyes with PVR.
• Giant retinal rupture.
• Shift posterior to the dislocated fragments of the lens or IOL.

Silicone oil has low gravity and can float. It allows for more controlled surgical manipulations and can be used for prolonged postoperative intraocular tamponade.

Equipment

Proliferative vitreoretinopathy. The purpose of the operation is to remove transvitreal tract vitrectomy, surface traction - by dissecting the membranes, which will cause retinal mobility and further closure of the ruptures,

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Postoperative complications of vitrectomy

The increase in intraocular pressure may be due to the following reasons.

• Excess volume of injected gas
• Early glaucoma, induced by the accumulation of silicone oil in the anterior chamber.
• Late glaucoma, induced by a possible block of the trabecular apparatus due to silicone oil in the anterior chamber. This can be avoided if the silicone oil is removed in time, either through the pars plana in the phakic eyes, or through the limb and eyes with afakmei.
• Cells are "shadows" or steroid glaucoma.

Cataract can be caused by:

• The use of gas. Usually transient and controlled by the use of low concentrations and small volumes of gas,
• Using silicone oil. It develops in almost all cases. It shows the removal of silicone oil in combination with the extraction of cataracts.
• Late compaction of the nucleus, which develops sometimes within 5-10 years.

Relapse of retinal detachment often occurs after gas resorption (3-6 weeks after surgery) or after removal of silicone oil. The main reasons are:

• The recurrence of the old rupture as a result of inadequate surgical dissection in the eyes with PVP or repeated proliferation of epiretinal membranes is most often found in PDR.
• New or missed tears, especially near the sclerotomous holes for vitrectomy pars plana,

Early removal of silicone oil is associated with a 25% risk of re-detachment of the retina in the eyes with PVP and giant gaps and with a 11% risk in the eyes with PDD.