Page 2 - BPR

CUAJ – CUA Best Practice Report Bhojani et al
BPR: Laser eye safety

Objectives
Since the introduction of the Holmium:yttrium-aluminum-garnet (Ho:YAG) laser over 2 decades
ago, it has become an indispensable tool in the urologist’s armamentarium. More specifically, in
the subspecialty of endourology, the Ho:YAG laser has revolutionized the approach to kidney,
ureteral and bladder stones, endoluminal tumours, strictures and benign prostatic hyperplasia
(BPH)[1]. Since its widespread adoption, and as with other laser wavelengths there have been
concerns regarding its safety. In particular, the potential risks of eye injury to patients and
operating room personnel have led laser manufacturers and governing bodies (including the
Canadian Standards Association (CSA)) to require/mandate that all intraoperative personnel
wear laser safety goggles. Despite this recommendation, the actual risk of eye damage associated
with the Ho:YAG laser during endourological procedures has not been clearly defined. The
objectives of this best practice report are to review the current literature regarding the risks of
eye injuries and to provide practical and evidence-based recommendations on eye safety with the
use of the Ho:YAG laser. This best practice report was developed in conjunction with members
of the Canadian Endourology Group.

Background
The Ho:YAG laser is a pulsed laser with a wave length of 2100 nm, with a total energy emission
that can vary between 0.2- 6 joules and a frequency of 6- 50 Hz. The depth of penetration is
limited to 0.4 mm, and with a wavelength in the mid-infrared spectrum it is avidly absorbed by
water. Since human tissue is composed mainly of water, the majority of the Ho:YAG laser
energy is absorbed superficially and allows for precise superficial cutting or tissue ablation, with
minimal collateral tissue injury.
The first reported use of the Ho:YAG laser was in 1992 in a canine model and was
followed by the first human application in 1994 for the treatment of a superficial bladder
tumor[2, 3]. Without question this laser has evolved to become an essential tool in the
contemporary management of numerous urological conditions including urinary stone disease,
urethral and ureteral strictures, urothelial tumors and benign prostatic hyperplasia (BPH). While
data is difficult to obtain, most hospitals in Canada with a urological service are likely to have a
Ho:YAG laser that is used multiple times a week for various indications.
As with most laser devices used for medical indications and according to the American
National Standards Institute (ANSI) standards, the Ho:YAG laser is considered a class 4 laser,
meaning it may cause immediate injury to eye and skin through direct or reflected exposure to
the beam[4].
When considering the risks associated with laser usage and the need for personal
protection, several definitions are important to understand. The Maximum Permissible Exposure
(MPE) is the maximum level of laser radiation to which a person may be exposed without
hazardous effects or biological changes in the eye or skin[5]. The MPE is determined by the
specific wavelength of laser, the energy involved, and the duration of the exposure. MPE is