LEARNING CURVE

Appropriate preparation and forward thinking can help surgeons avoid the most common pitfalls of introducing a femtosecond laser for cataract surgery into their ophthalmic practices, according to Michael C Knorz MD.

“Like every new technology there is a learning curve to be negotiated in introducing a femtosecond laser for cataract surgery. However, with a bit of forward planning the transition can be negotiated smoothly and without too many difficulties,” Prof Knorz told delegates attending the XXXI Congress of the ESCRS in Amsterdam.

Based on his own experience in Mannheim, Germany since introducing the LenSx (Alcon) laser in 2011, Prof Knorz said that there are three key steps to obtaining optimal outcomes with femtosecond-assisted cataract procedures: docking, capsulorhexis and hydrodissection.

“My advice would be to practise docking as much as possible before doing the first procedure because it is absolutely essential to the success of the surgery. Secondly, confirm that the capsulorhexis is complete. It is very rare that it won’t be, especially with the modern lasers we use today, but it is still safer to inject viscoelastic and confirm that it is fully complete to maintain the significant advantage of the perfect capsulorhexis created by the laser. Finally, I would advise using a modified hydrodissection technique to ensure that there is no excessive build-up of pressure inside the capsular bag that might cause capsular blow-out problems,” he said.

In terms of workflow, Prof Knorz said that he opted to place the femtosecond laser inside the main operating room along with the surgical microscope and the Alcon EX 500 excimer laser. All three machines are connected by a moving bed, which has three programmable stops.

“I prefer to have all the machines in the one operating room as I think this enhances patient comfort. There are also other advantages. Since the eye has been draped in a sterile environment the surgery can start with an intraocular procedure – for example, pupil expansion rings in small pupil cases before moving the patient under the laser. The laser may also be used again in a later part of the surgery, for a posterior capsulorhexis for example,” he said.

The first key step to be mastered is the docking of the eye to the laser, said Prof Knorz. While in the case of the LenSx platform this is achieved by lowering the SoftFit suction piece on the eye directly, other laser systems use a liquid interface to achieve the same effect.

“The idea behind both approaches is basically the same – to avoid excessive pressure and corneal folds so the laser action is uninhibited, enabling the laser to deliver more precise cuts and hopefully better outcomes. In all these systems, good central docking is essential and surgeons should practise docking on several patients before they start their first procedure. The eye should not be tilted too much, because excessive tilt may cause decentration in the laser pulses and cause decentration of the capsulorhexis,” he said.

The next important step in the transition to femto-cataract is to ensure the integrity of the capsulorhexis.

“With modern laser systems, 99.9 per cent of the time we achieve a free-floating capsulorhexis but it is important to verify that the capsulorhexis is complete. If it is not complete, capsular tags may cause anterior capsule rupture, which in turn may lead to posterior capsule rupture,” he said.

In order to check the integrity of the capsulorhexis, Prof Knorz said that a blunt spatula can be used to open the side-port incision first, followed by injection of viscoelastic to avoid shallowing of the anterior chamber.

“I simply use the phaco tip to check the integrity of the capsulorhexis and should any tags be present, I remove the phaco tip and use a capsulorhexis forceps to complete the capsulorhexis manually,” he said.

The third important step is to adopt a modified hydrodissection technique, said Prof Knorz.

“The laser creates air bubbles in the capsular bag, which may increase the pressure in the bag, especially if a small capsulorhexis is used. Hydrodissection should therefore be slow and with low volume to avoid a capsular blow-out syndrome by a sudden increase in pressure,” he said.

The preferred option is to perform the gas release followed by hydrodissection, said Prof Knorz.

“I use the hydrodissection cannula to split the nucleus open because it has been fragmented already. The nucleus may also be split with a chopper, splitter or hook to let the trapped air escape prior to hydrodissection,” he said.

Once these three key steps have been managed, the remaining part of the surgery is not different from standard phacoemulsification, concluded Prof Knorz.

Michael C Knorz: knorz@eyes.de