Perceptions and Practice Patterns of Holmium Laser Goggles in Endourological Procedures: An Unnecessary Evil?

Introduction

The Ho:YAG fiber is widely utilized in a variety of urological procedures. While first used for lithotripsy, its application has broadened to tissue incision, resection, and ablation of urothelial and prostate tissue. ¹ The holmium laser is a contemporary 2150 nm wavelength fiber valued for its small diameter offerings, improved maneuverability and focal absorption in tissue. In a typical endourological procedure, depending on the pulse and energy settings, the depth of tissue penetration is approximately half a millimeter. ²

Laser safety eyewear is recommended for intraoperative personnel for the holmium laser by all manufacturers, laser governing bodies, and the European Association of Urology. ^3,4 In the United States and Canada, these fall under the Occupational Health and Safety Act under ANSI Z136 which is a series of laser safety standards. ¹ These recommendations stem from the holmium laser being classified by the International Electrotechnical Commission as a class 4 laser, meaning it can cause skin and eye injury from direct but not necessarily diffuse or reflected energy. ³ Many institutions have dedicated laser safety staff, committees, and training programs to implement safety standards, such as the mandatory use of laser safety goggles, for all intraoperative personnel. ³ Importantly, the holmium laser is considerably safer than its predecessors. A large American safety database study found that despite ocular adverse events occurring in older generation laser fibers (Nd:YAG, KTP, and diode), there have been no eye injuries ever reported with the holmium laser. ⁵ Furthermore, in a recent study, Villa et al. examined the effects of the holmium laser at various energy settings and exposure times on ex vivo pig eyes and determined that damage could only take place within 5 cm of the fiber tip. ⁶ Additionally, regular eye glasses were found to be equally as protective as laser goggles. ⁶

With the above context, the continued implementation of hospital laser policies requiring mandatory use of laser goggles for all intraoperative personnel does not match the inherent risk associated with the holmium laser. Our goal was to further characterize the real-world perceptions and practice patterns of laser safety goggles in endourological procedures among high-volume specialists.

Materials and Methods

A 24-question survey was created by a small committee of high-volume endourologists using Survey Monkey^© and distributed through e-mail to all members of the Endourological Society listserv. Responses were voluntary and all data were collected anonymously. Descriptive data were processed categorically.

Results

Discussion

The holmium laser has become a mainstay technology for a variety of endourological procedures. ⁷ Among our cohort, 97% of surgeons were routinely using this laser fiber. The properties and safety profile of the holmium laser have been well characterized. ¹ Factors known to influence the risk of injury from the laser include the distance to the terminal laser source (the laser fiber tip) and power of the laser, including pulse energy. ³ While occupational safety for surgeons and surrounding personnel remains of paramount importance, blanket laser safety policies should be challenged if they are not congruent with current evidence-based research.

Significant adverse events from the holmium laser are exceedingly rare. Within our cohort, 19% of surgeons had witnessed some form of adverse event; however, all were described as superficial skin burns, mostly to the hands and arms. More importantly, no eye injuries were reported among our respondents, despite many not wearing any form of eye protection. Most adverse events associated with endourological lasers have resulted from generator failure or fiber tip breakage. ⁵ While eye injuries from mild corneal abrasions to total vision loss have been reported with the use of historical laser fibers (Nd:YAG, KTP, and diode lasers), there have never been any eye injuries reported with the use of holmium laser. ⁵

A study examining the effect of the holmium laser on thermal paper, laser goggles, and ex vivo pig eyes found that it can theoretically cause damage when set to high energy, but only to the cornea, from close distances (0–5 cm) and in the absence of eye protection. ⁶ The degree of damage was dose dependent with the energy settings and regular eyeglasses were found to be equally effective for preventing laser damage as laser safety eyewear. ⁶ While the optimal settings for most endourological cases remains a balance between maximal fragmentation, fragment size, and retropulsion, ⁸ most procedures would not routinely be using the higher energy settings (2J, 10 Hz) seen to cause the most damage in this study.

Laser safety policies mandating all intraoperative personnel wear goggles are not necessarily without competing risk as 70% of our cohort felt that laser goggles may impair their vision. While difficult to quantify, the value added from improvements in scope quality and optics may be negated by laser goggles at the expense of patient safety. The risk to patients may extend beyond the surgeon operating, as certain laser goggles have also demonstrated color distortion, which has been identified as a possible source of drug label and administration error for anesthesia. ⁹ However, this color distortion was not found specifically with newer generation holmium laser goggles. ¹⁰ Lastly, the operational cost of sterilizing, repairing, and replacing an institution's fleet of laser goggles is not insignificant.

Alternative options for laser protection should be at the discretion of the user but may include regular eye glasses or radiation-protective leaded glasses. The latter may be of particular value in young or high-volume endourologists who are at higher theoretical risk of cataract formation. ¹¹ Regular eye glasses have been shown to be equally as effective, are less clunky, and actually correct for vision, whereas most current hospital mandatory laser goggle policies require them to be worn under goggles. Protective eyewear withstanding, there appears to be a large margin of safety for those users who choose to use none of the above options.

Our study has some expected weaknesses. Survey data inherently relies on response rates and recall which creates an element of bias. Furthermore, the questions we used were not formally validated before distribution. Generalizability of the data may be limited by the fact that only 15% of respondents worked purely in a community milieu. This likely demonstrates an overrepresentation of academic urologists and subsequent policies that are more likely to be found at larger centers with more resources.

Conclusions

Endourologists globally are routinely using the holmium laser for a variety of minimally invasive procedures. The breadth of laser safety training, policies, and protective equipment used varies significantly. Two thirds of urologists felt that laser goggles interfered with their vision. Given recent studies examining the minimal potential for optical damage and equivalent protective function offered by regular eyewear, operators should have a choice of protective or regular eyewear when using the holmium laser. Furthermore, based on the damage range only extending to five centimeters, no other intraoperative personnel should be required to wear protective glasses. Hospital laser policies should be updated accordingly to reflect this.