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CAPSULE RUPTURE

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While posterior capsule rupture remains one of the most common significant intraoperative complications during cataract surgery, the risk can be reduced if a proper strategy is put in place, especially in ophthalmology training settings, according to Oliver Findl MD.
“Posterior capsule rupture is associated with the need for additional surgical procedures, a greater number of follow-up visits, and especially increased frequency of postoperative complications. It is widely regarded as the benchmark complication to judge the quality of cataract surgery,” Dr Findl told delegates attending a joint ESCRS-EURETINA symposium during the XXXII Congress of the ESCRS in London. 
The reported rates of posterior capsule rupture are usually around 1.9 per cent in the larger clinical trials, with several studies showing greatly increased rates for ophthalmology residents, noted Dr Findl.
“We know that the risk factors for posterior capsule rupture include older age, presence of pseudoexfoliation, smaller pupil, brunescent cataract and surgical experience. With this in mind, a risk stratification strategy is useful in daily routine and particularly useful in training settings where patients at risk can be treated by more experienced surgeons,” he said.
While the primary function of the vitreous is to act as a support function for the retina and maintain the form and shape of the eye, it also serves as a diffusion barrier between anterior and posterior segment, and also has a metabolic buffer function, said Dr Findl.
With ageing, the vitreous undergoes molecular changes, with the formation of new covalent crosslinks between peptide chains allied to the cumulative effect of light exposure and non-enzymatic glycosylation. 
“This then causes structural changes with collagen fibres that aggregate and are no longer separated by hyaluronic acid. These fibres then thicken and associate with pockets of liquid called lacunae. 
“As the vitreous liquefaction increases, the resultant lacunae coalesce to form larger cavities followed by shrinkage of the vitreous body from the retina and eventually leading to posterior vitreous detachment (PVD),” he said.
The consequences of a broken vitreolenticular barrier during cataract surgery are multiple, said Dr Findl.
“On the one hand we experience a volume shift which may induce a PVD exposing vitreoretinal adhesions, as well as chemical transfer of solubles from the anterior to the posterior segment, and in particular inflammatory substances that may lead to an increased risk of cystoid macular oedema (CME),” he said.

VISUAL ACUITY
Other serious complications are also associated with posterior capsule rupture and vitreous loss, said Dr Findl. “At the end of the day if you have capsular rupture and associated vitreous loss, there is a 15-fold increased risk of retinal detachment, a 10-fold increased risk of CME, and similar increased rates for endophthalmitis. Visual acuity outcomes three to five years after surgery are also worse after posterior capsule rupture,” he said.
The signs of capsular rupture to watch for during cataract surgery include a slight, sudden deepening of the anterior chamber, momentary pupillary constriction, and the nucleus falling back onto the vitreous face and not coming towards the phaco tip, said Dr Findl. A reduction of aspiration may also be apparent due to vitreous obstruction of the tip, he added.
The data for surgical technique associated with posterior capsule rupture risk is also interesting, said Dr Findl. 
“One study showed that third-year residents in the United States had a 3.1 per cent to 14.7 per cent incidence of capsule rupture, while it was 4.4 per cent for registrars in the United Kingdom. The incidence decreases with an increasing number of cases performed. The incidence is also higher in developing countries where there is a higher frequency of white cataracts,” he said.
Dr Findl said one approach might be to develop a scoring system for preoperative risk stratification, with points added for different risk factors. A study by Tsinopoulos et al in 2013 showed that complication rates decreased significantly when high-risk patients were treated by an experienced surgeon, concluded Dr Findl.

Oliver Findl: oliver@findl.at

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