Is transcanalicular laser dacryocystorhinostomy using low energy 810 nm diode laser better than 980 nm diode laser?

Sir,

Various laser systems have been utilized successfully in endoscopic dacryocystorhinostomy (DCR). Based on the current data, it is not clear as to which one of these is the best for DCR surgery.[1] The tissue response to laser is influenced by the laser wavelength, application method (contact versus noncontact), application mode (continuous versus pulsed) and tissue properties.[2]

Diode laser (800–900 nm) has been preferred by some due to its delivery through a thin 0.6 mm fiber, facilitating its passage through the narrow lacrimal canaliculus and energy being released from the contact tip, thereby preventing the iatrogenic trauma to the surrounding tissues.[3]

The two wavelengths of diode used in DCR surgery are 810 nm and 980 nm. In the article by Gupta et al., the authors have beautifully cited an additional use of 810 nm diode laser in DCR surgery, which may already preexist in the clinic.[4] We also agree with authors that the lowest possible power should be used to prevent collateral damage as a higher power results in faster cutting but leads to a larger zone of necrosis. However, we tend to differ on some issues. The diode laser 980 nm is usually preferred for DCR surgery as it provides a better ablation and narrower tissue area involvement versus 810 nm that creates better coagulation than the vaporization. The variation in their effect is due to the difference in the tissue elements, which absorb or react to the specific wavelength. The 810 nm resembles Argon green laser and is better absorbed by hemoglobin whereas the 980 nm being closer to Nd: YAG laser is better absorbed by water that leads to translation of energy and change of liquid water in tissue to steam that blows the cell apart resulting in ablation.

The authors recommend a maximum power of three Watts with 810 nm diode laser, but in another study, the laser power of three watts is considered too weak to incise the bone.[5] So, a power as low as this may be useful in failed DCR with membranous blocks, where bone cutting is not required but in primary cases, it may not be always effective. A graded approach to start with three watts and to increase the energy as per requirement would be more appropriate.

In the procedure described, creation of osteotomy is followed by its visualization through the nose. However, it is pertinent to confirm the correct placement of the laser probe by visualizing a well-focused aiming beam through the nasal endoscope before commencement of firing. This will prevent soft tissue damage which can lead to subsequent failure due to the formation of adhesions. Once the lacrimal sac is located, the ostium needs to be enlarged inferiorly to prevent the sump syndrome. The article does not talk about the size of the osteotomy that plays an important role in the long-term success of the procedure!

To conclude, the concept is good but further documentation is required to state that 810 nm diode laser at three W is the ideal laser for DCR surgery.