EYEBANK INNOVATION

Pre-stripped membrane procedure for DMEK surgery. A: Descemet incisions by the calibrated punch; B: cleavage of the peripheral membrane; C: stripping procedure by sectors; D: stromal rim marking to identify the position of the peripheral membrane hinge; E: a pre-stripped membrane ready to be delivered. Courtesy of Veneto Eye Bank Foundation

A new technique developed by Italian eye bank researchers provides a means of preparing posterior lenticules, pre-cut and pre-loaded in a glide for use in endothelial keratoplasty procedures.

“A few years ago surgeons asked us if we could provide them with just the posterior lenticules to help them in the surgical theatre. We tried to figure out if it was possible and the answer was, yes, it is possible,” said Alessandro Ruzza, Eye Bank Specialist, Veneto Eye Bank Foundation, Venice, Italy, at the 19th ESCRS Winter Meeting in Istanbul, Turkey.

The new technique, born from the partnership between the Eye Bank and Dr Massimo Busin, involves the use of a modified (Busin-type) glide with a lid that contains the trephined posterior lenticule. The device is placed in a container of tissue culture medium and is delivered from the eye bank to the surgeon, ready for use in endothelial keratoplasty procedures.

Preparing the lenticule in this way overcomes the portability issues that had previously made the use of pre-cut posterior lenticules less feasible on a wider scale. In addition, the use of the device reduces the number of steps necessary for graft preparation in the surgical theatre, making the endothelial keratoplasty procedure much easier to perform and potentially safer too.

Mr Ruzza noted that in their laboratory evaluation of the technique, using a 3D printed prototype, there was an endothelial cell loss of only four per cent in 17 pre-cut and pre-loaded lenticules after storage for seven days. In a clinical validation study, surgeons from Italy and different parts of Europe implanted a total of 16 pre-cut and pre-loaded lenticules for DSAEK and ultra-thin DSAEK. They reported that there was no significant difference between the clinical outcomes achieved with the pre-loaded lenticules and those they achieved with the more conventional pre-cut tissues. However, the surgeons also reported that the pre-loaded lenticules greatly simplified and sped up the procedures by an average of around 20 minutes.

Mr Ruzza said that in the course of their experiments they found that the very thin lenticules were very difficult to handle. They therefore developed two different scaffolding approaches, one involves the use of the anterior lenticule and the other used a contact lens. In both approaches, the scaffolding is detached from the lenticule and removed from the glide just prior to surgery.

He noted that when using the anterior lenticule scaffolding approach, the posterior graft tissues increased in thickness by a mean of only 20 per cent, but were somewhat adherent to their anterior lenticule scaffolding. The lenticules were much less adherent to the contact lens, but they increased in thickness by a mean of 40 per cent when using that approach.

FROM EYE BANK TO THEATRE

Mr Ruzza explained that the preparation of the lenticule involves separating a standard pre-cut posterior lenticule from the anterior lenticule and placing it on the contact lens, then performing a punch trephination to the desired diameter (from 8 to 9mm). The still mutually adherent lenticule and contact lens are then placed in the new glide device, the lid is locked and the device is placed in a container of tissue culture medium for storage and delivery.

Preparation of the graft in the surgical theatre involves lifting the device from its container using its special handle and then draining the liquid out of it, to better distinguish between the lenticule and the contact lens. The surgeon then engages the lenticule with a 23-gauge forceps and separates it from the contact lens, which is then removed from the glide and the endothelial keratoplasty procedure is performed in the same manner as with a Busin glide.

“Right now we are in the production phase and very soon we’re going to final validation study,” added Mr Ruzza.

​PRE-STRIPPED DMEK

Mr Ruzza noted that he and his associates are also working on a means of providing pre-stripped and pre-loaded Descemet’s membrane lenticules for DMEK procedures.

He added that they currently use a stripping technique rather than pneumatic technique to cleave Descemet’s membrane from the stroma. To simplify the incision into Descemet’s membrane, they use a special pre-calibrated punch with a maximum cut depth of 150µm. Deeper cuts make the cleavage plane between the membrane and the stroma harder to see. They then strip the membrane by sectors but leave it attached to the corneal button by a small hinge, and mark the scleral rim with a skin marker. They then place it in a container of tissue culture medium for storage and delivery.

Alessandro Ruzza:
alessandro.ruzza@fbov.it