Re: Evaluation of Novel Ball-Tip Holmium Laser Fiber: Impact on Ureteroscope Performance and Fragmentation Efficiency (From: Shin RH,Lautz JM,Cabrera FJ,et al. J Endourol 2016;30:189–194)

Dear Editor:

We have read with interest the article recently published in the Journal of Endourology by Shin et al. regarding a new “ball-tip” (BT) laser fiber, evaluating performance characteristics and insertion force in an ex vivo model. The study compared the new BT fiber with a standard fiber (SF) from the same company and showed that the BT fiber needed significantly less force to pass through a deflected ureteroscope than the SF.

A consideration although omitted in the discussion must be made. The authors compared only the BT fiber with an uncleaved and stripped fiber, thus omitting the role of cleaved fibers. Cleaving the fiber end from the beginning of the surgery has many advantages: First, coated fibers are easier to see during the procedure. In addition, they remain attached most of the time, even if they accidentally break at any point during the surgery. Second, cleaving the fiber tip must be constantly performed during surgery to conserve its efficacy, and cleaved laser fibers have been shown to be more efficient than uncleaved fibers. ¹ We regularly cut the fiber tip as a standard procedure.

This principle also concerns BT fibers; it has been shown that after 1 minute of use, a BT fiber becomes indistinguishable from an SF ² and that an estimated 3.13 kJ is needed to completely destroy the BT fiber. ³ This allows the BT fiber only one or few entries as such, losing its capability of use. Thus, the manufacturer also acknowledges that subsequent passages will be more difficult.

Laser fiber insertion force has been previously evaluated only with uncleaved and stripped fibers. In our experience, cleaving the transparent end of laser fibers also allows an easy passage through fully deflected ureteroscopes, especially small 275 μm fibers (with the exception of the Olympus URF-P5 ureteroscope because of its S-shaped tip configuration caused by the position of the retraction components for deflection). In this scenario, the fiber will remain surrounded just by the polymer jacket; we also believe that this polymer jacket works as a protective sheath, avoiding working channel damage. Also, the deflection is minimally affected with these small fibers.

The recommendation still remains to reposition stones out of the lower calix and to avoid passing a laser fiber through a deflected ureteroscope to prevent all odds of damage. In the unlikely event of having a fully deflected ureteroscope where the surgeon is forced to pass a fiber keeping his position, a reasonable approach would be to pass a BT fiber without forgetting that cleaved small fibers may pass as well if the other is unavailable or if the BT fiber has been destroyed during treatment.