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New tools for surgery

Howard Larkin

Posted: Wednesday, April 8, 2020

Ken K Nischal MD, FAAP, FRCOphth

Paediatric cataract surgery presents special challenges that can be addressed with the right technology, Ken K Nischal MD, FAAP, FRCOphth, told the AAO 2019 Paediatric Ophthalmology Subspecialty Day in San Francisco, USA.
Posterior capsule opacification after cataract surgery is a particular risk in children because their lens epithelial cells proliferate much more aggressively than in adults. The bag-in-lens (BIL) intraocular lens designed by Marie-José Tassignon MD, PhD, effectively prevents this problem, said Dr Nischal, who is chief of paediatric ophthalmology at the University of Pittsburgh Medical Center, Children’s Hospital, Pittsburgh, USA.
Available for about 15 years, the BIL features a groove around the lens periphery into which the edges of openings in both the anterior and posterior capsule are inserted.
“What this does is it sequesters the lens epithelial cells and you really get no visual axis opacification at all,” said Dr Nischal.
He cited studies by Prof Tassignon and colleagues showing that BILs implanted in children under the age of six have remained completely clear for up to seven years’ follow-up and counting. (Tassignon MJ et al. Acad Geneeskd Belg 2005;67(4):277-88. Tassignon MJ et al. J Cataract Refract Surg 2007;33(4): p. 611-7. Tassignon MJ et al. J Cataract Refract Surg 2011;37(12):2120-9.)
While the BIL is not difficult to implant, there is a learning curve, Dr Nischal noted. It requires precisely sized and positioned capsulotomies, both anteriorly and posteriorly. Foldable rings that Dr Tassignon developed to guide the anterior capsulotomy work well in children even though their capsules are more flexible, and the anterior opening serves as a template for the posterior, Dr Nischal said.
Snapping the capsule edges into the lens groove, which has short oval haptics protruding from the posterior and anterior surfaces at right angles to facilitate capture, requires practice, but can be done quickly with experience, he said.

Precision pulse capsulotomy
Due to the greater elasticity and tear resistance of the capsule, capsulotomy can be more challenging in paediatric patients than in adults. A precision pulse capsulotomy (PPC) device (Zepto, Mynosys, Fremont, California, USA) may help, Dr Nischal said.
The PPC device consists of a small foldable suction cup with a nitinol loop that is opened inside the anterior chamber and attached to the anterior capsule with the loop held against the capsule. Electronic pulses through the nitinol loop cut a precise round opening, though the opening may stretch slightly in young eyes.
Dr Nischal cited a paper finding successful use of PPC capsulotomies in 21 paediatric patients with margins overlapping the optic edges in 19 eyes, even though the opening was slightly larger than expected. (Chougule P et al. BMJ Open Ophthalmol 2018;4(1)).
“This technology may become useful if we can make it a little bit smaller for children, but it is available,” Dr Nischal said.

Intraoperative OCT
Intraoperative OCT is useful in paediatric cases for visualising common cataract complications such as posterior ruptures, fibrosis and intumescent cataracts in real time. This allows surgeons to see precisely where they need to cut to separate entangled tissues and avoid complications, Dr Nischal said.
For example, in cases of posterior rupture, OCT displayed alongside the direct image in the microscope viewfinder allows direct visualisation of vitreous. Dr Nischal said that contrary to adult cataracts, in paediatric patients he commonly removes the soft lens peripheral tissue first, leaving the nucleus in place. This simplifies management of any rupture behind the nucleus, allowing it to be controlled with viscoelastic tamponade, and conversion of the tear into a posterior capsulotomy before anterior vitrectomy. No air or staining are required.
Live OCT is particularly useful in traumatic cases because it allows precise identification of lens matter and vitreous, Dr Nischal said. OCT helps locate lakes of fluid in intumescent cataracts, which then can be opened in a controlled manner by applying aspiration directly as they are lanced, preventing large tears.
“They’re not just toys for boys or pearls for girls. Groovy gadgets can be used to improve outcomes,” Dr Nischal said.

Ken Nischal: kkn@btinternet.com