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Pars plicata vitrectomy for posterior capsule rent
This method offers an alternative approach for anterior segment surgeons.
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Posterior capsule rupture that occurs before the nucleus is emulsified is a precipitous and intimidating complication that puts the surgeon on a high “adrenaline rush.” This complication is often further precipitated by the constriction of the pupil and inability to do a proper vitrectomy.
A limbal incision vitrectomy (Figure 1), which is a preferred site by many anterior segment surgeons, often leads to the collapse of the anterior chamber and improper access to the lenticular matter trapped in the pupillary plane. Potential limitations of this approach include the fixed directionality of the instruments and cannulas, which may lead to corneal distortion and poor visualization, and the fulcrum effect of the cannula, which may restrict the instrument movement, as well. Pars plana has always been a favored choice of sclerotomy site for vitrectomy (Figure 2) and retinal surgeries, for various reasons.
Anatomic considerations
The ciliary body comprises two parts: pars plicata and pars plana. About 1.5 mm from the limbus, the pars plicata extends about 2 mm and the pars plana extends about 4 mm up to the ora serrata. The ciliary plexus lies at the root of the iris, and the chance of hitting these blood vessels is high with pars plicata sclerotomy. On the other hand, the vitreous base is located in the lower 2 mm of pars plana, and improper sclerotomy done at this site can induce peripheral retinal tear, dialysis or sometimes a retinal detachment, if the fluid is kept on during the introduction of the infusion cannula.
Invariably, pars plicata/pars plana vitrectomy is an underused option for performing an anterior vitrectomy by anterior segment surgeons. The inhibition creeps in from the idea of damaging the retina and disturbing the vitreous, which can then inadvertently affect the final visual output. A major advantage of performing vitrectomy behind the pupillary plane is to provide a better fluidic seal and better access to the retropupillary area and to the plane of the capsulorrhexis. An IOL implantation technique can then be chosen, taking various factors into account.
Figure 1. Limbal incision vitrectomy. Note the scleral incision through which vitrectomy is being done.
Images: Agarwal A
Figure 2. Pars plana vitrectomy.
Figure 3. Pars plicata vitrectomy. (a) Operative image. (b) Illustrative image.
Figure 4. Pars plicata vitrectomy for glued IOL surgery in a subluxated IOL case. Note the glued IOL forceps (Epsilon) holding the haptic of the IOL to prevent it from falling down.
As early as 1990, pars plicata sclerotomy (Figure 3) was reported to help in repositioning a posteriorly dislocated IOL. The pars plicata approach also has many advantages over the translimbal approach. The pars plicata is in the direct axis of the lens, allowing for more complete removal of lenticular material. Unlike in the limbal approach, the cornea is not manipulated during surgery. In our series of glued IOL surgery, sclerotomy is made at the level of pars plicata — approximately 1.5 mm away from the limbus, just beneath the scleral flaps. The haptics of the IOL are externalized from these sclerotomy sites with a 23-gauge to 25-gauge glued IOL forceps (Figure 4). In the review of complications profile of 486 eyes with rigid IOLs and 191 eyes with foldable IOLs, posterior segment complications included macular edema (1.4%), retinal detachment (1%) and chronic vitritis (0.4%). These results suggest that a thorough vitrectomy can be done at the pars plicata site without fear of damaging either the retina or the vitreous base.
Technique
A small, partial-thickness scleral flap, approximately 2.5 mm by 2.5 mm from the limbus, can be fashioned (or a triangular flap, as in anti-glaucoma surgery), followed by a sclerotomy with a microvitreoretinal blade approximately 1.5 mm from the limbus. The needle should be directed toward the mid-vitreous cavity. A 23-gauge vitrectomy cutter attached to a routine phacoemulsification machine can be introduced through this sclerotomy site, and a thorough vitrectomy can be done with better access and management of the vitreous and lenticular fragments. Following this, the vitrectomy cutter can also be used to cut all the vitreous strands protruding from the sclerotomy site, so as not to induce any traction on vitreous at the incision site.
The flaps can be sealed with tissue fibrin glue or sutured to the base. The site of the scleral flap can be chosen depending upon the primary incision for the cataract surgery and also on the location and extent of PCR and the retained nuclear fragments. Alternatively, a self-sealing sclerotomy incision can be sculpted and the site can be used for performing vitrectomy.
Precautions
A forceful entry at the pars plicata should be avoided during sclerotomy. If resistance is encountered, the chances are that the surgeon is at the level of the root of iris. A forceful entry at this juncture can lead to iridodialysis and hyphema. The 20-gauge needle or a microvitreoretinal blade, which is used to create a sclerotomy, should be withdrawn and a fresh entry should be attempted slightly posterior to the site of previous entry.
Surgical complications related to the insertion and removal of instruments through the pars plana incisions during vitrectomy have been well described. Retinal breaks and dialyses posterior to the sclerotomies are known to occur intraoperatively, owing to mechanical traction on the anterior vitreous.
The pars plicata approach has been used successfully in children with retinopathy of prematurity. An incision made in the pars plana of young children may increase the risk of retinal detachment. Because the pars plicata is further anterior from the vitreous base and ora serrata, the risk of retinal detachment is lessened.
Apart from this, in our series of pars plicata vitrectomy for all age groups, we did not come across any major complications and had a gratifying and a favorable outcome. An extensive vitrectomy also prevents pupillary block glaucoma resulting from the vitreous prolapsed into the anterior chamber. Lastly, the vitreous is removed without trauma to the iris, which has been a suspected cause of cystoid macular edema. For anterior segment surgeons who are reluctant to make a pars plana incision following a PCR, this site can be an option.