CAPSULAR RUPTURE

Many cases of capsular rupture could probably be avoided by taking appropriate precautions, said Graham D Barrett MD, of Australia, in a presentation during the Combined Symposium of Cataract & Refractive Societies at the XXXII Congress of the ESCRS in London.

“Posterior polar cataract is associated with a very high incidence of posterior capsular rupture (PCR) during cataract surgery. The posterior capsules in eyes with posterior polar cataract are known to have an abnormal adhesion to the polar opacity or a pre-existing weakness of the capsule that predisposes the eye to PCR. It is this, rather than a pre-existing capsular defect, which implies that we can avoid capsular rupture if we take the correct precautions,” he said.

Posterior polar cataract is a round discoid opacity of degenerative lens fibres associated with autosomal dominant mutation of the PITX3 gene. This is a transcription factor responsible for a protein involved in lens formation during eye development.

“What can we do to decrease the chances of rupture?” asked Dr Barrett.

Published rates of PCR in cases of posterior polar cataract range from six per cent to 36 per cent, which represent significant rates even at the low end of this spectrum.

“First of all, one should not begin with an initial hydrodissection. This forces fluid into a closed space, which builds up pressure inside the capsule and risks PCR. Instead, a deep hydrodelineation should be performed first, which places far less pressure on the posterior capsule. After hydrodelineation, one can proceed to a gentle, multicentric hydrodissection,” he explained.

Inside-out delineation, a technique first described by Dr Abhay R Vasavada in 2004 for the treatment of posterior polar cataract, involves fluid injection from the inside of the nucleus to the outside, allowing precise, controlled hydrodelineation and minimal risk to the posterior capsule.

Multicentric hydrodissection involves injecting fluid into the capsule at various locations, so as to avoid one single high-pressure flow. He referred to a study by IH Fine et al, published in the JCRS in 2003, which describes this technique.

Regarding nucleus fragmentation techniques, Dr Barrett prefers a vertical chop, even with a very soft lens. This allows the surgeon to stay away from the posterior capsule during this step.

“In most cases, you’ll see that the posterior polar opacity will be removed during the removal of the cortex,” he said. However, if this is not the case, he added: “I don’t recommend aggressive scrubbing of the opacity. This is too risky.”

Another point Dr Barrett strongly emphasised was the maintenance of a very stable anterior chamber throughout the procedure. This can be achieved by injecting a viscoelastic device when removing instruments from the eye, in order to prevent the posterior capsule from bulging forward.

Graham Barrett: graham.barrett@uwa.edu.au