Studies have shown that 1 out of 3 posterior polar cataract surgeries result in a ruptured posterior capsule. Here’s the technique that I use to avoid that complication. My personal rate of posterior capsule rupture in cases of posterior polar cataract is about 1 in 100.
Posterior polar cataracts are congenital opacities at the posterior pole of the crystalline lens. Multiple factors may play a role in their formation, with recent evidence pointing to a recurrent mutation in the PITX3 gene. The posterior polar opacities can be associated with other ocular developmental defects, particularly of the iris or other structures of the anterior segment. These types of posterior lens opacities can progress over the years and become more visually significant, leading to a decline in visual acuity and necessitating cataract surgery.
Phacoemulsification of a posterior polar cataract is particularly challenging because the posterior capsule can be weak, fragile or even absent at the site of the opacity. This leads to a higher risk of posterior capsule rupture, vitreous loss and other complications. Initial studies have demonstrated that this risk is as high as one in three patients, although recent reports peg the risk a bit lower. The size of the posterior polar opacity may also influence the risk of capsular rupture, with larger opacities associated with greater risk.
Multiple surgical techniques and approaches have been described, but the one common goal is to avoid manipulation of the posterior capsule at the site of the posterior polar opacity. The technique that I prefer is hydrodelineation to remove the central lens endonucleus, followed by viscodissection of the remaining lens epinucleus and cortex.
Creating a well-centered 5-mm round capsulorrhexis is particularly important in an eye with a posterior polar cataract because there is a significant chance that the IOL will need to be placed in the ciliary sulcus with optic capture through the anterior capsular opening.
It is important to avoid performing hydrodissection near the posterior lens opacity because the fluid wave can cause the posterior capsule to rupture and the nucleus to fall into the vitreous. While some surgeons advocate a small amount of hydrodissection, stopping just shy of the posterior pole, my advice is to avoid this step altogether.
Hydrodelineation using a small quantity of balanced salt solution in a syringe with a 27-gauge cannula can be performed because this will separate the endonucleus from the remaining epinucleus and cortex. The endonucleus can then be removed from the eye using the phaco probe.
At this point, all that remains in the capsular bag is the softer lens epinucleus and the cortex. With the use of a dispersive viscoelastic, which has a more liquid and syrup-like texture than the cohesive viscoelastics, the remaining lens material can be carefully dissected from the capsule. Using a viscodissection technique in all quadrants of the lens allows for a complete cleaving of all residual lens material from the capsule. This method has several benefits: The viscoelastic is slow and controlled, it pressurizes the anterior segment, it can tamponade any existing break in the capsule, and it creates a barrier between the lens material, which is brought forward, and the capsule and vitreous, which are pushed backward.
The irrigation and aspiration probe can be placed in the eye and kept centrally in the anterior segment while the lens material is aspirated. The risk of a capsular rupture is highest during attempted manipulation or cleaning of the posterior polar opacity. While the posterior polar opacity can often be removed from the capsular surface, care should be taken to avoid polishing or cleaning. It is far easier and less risky to perform a YAG laser capsulotomy to clear the visual axis in the postoperative period.
When the lens material has been removed, it is critical to not let the anterior chamber collapse. This means keeping the I&A probe in the eye in foot pedal position 1 to maintain the infusion pressure and then using the non-dominant hand to inject viscoelastic via the paracentesis incision to fully inflate the capsular bag. At this point, the I&A probe can be removed from the eye and the new IOL can be inserted.
A three-piece IOL is preferred if there is doubt about the posterior capsule integrity because it offers more options for placement. The entire IOL can be placed in the capsular bag if the posterior capsule is intact. If a defect of the posterior capsule develops during IOL insertion, the haptics can be placed in the sulcus with the optic captured via the buttonhole technique through the capsulorrhexis. This provides excellent stability of the lens and creates a barrier to prevent vitreous prolapse.
The postoperative course for these patients tends to be straightforward, particularly if the posterior capsule remains intact. After contraction of the capsular bag has created a strong fixation for the IOL, a YAG laser capsulotomy can be performed for any residual posterior capsule opacity. Using the technique of viscodissection, posterior polar cataracts can be effectively treated while minimizing the risks.