Page 3 - BPR

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

usually set as 10% of the power or energy density that has a 50% probability of causing damage
under worst-case conditions[5].
The Nominal Hazard Zone (NHZ) relates to the space within which the level of direct,
reflected or scattered laser radiation exceeds the MPE[5]. Exposure levels beyond the boundary
of the NHZ are below the applicable MPE, and therefore no safety measures are needed. The
Nominal Ocular Hazard Distance (NOHD), is the distance along the axis of the unobstructed
beam from the laser to the human eye beyond which radiant exposure is not expected to exceed
the appropriate MPE[4]. Avoiding direct eye exposure to a laser’s beam closer than the NOHD
through the wearing of eye protection is recommended as the beam’s power density (irradiance)
from the source to the NOHD exceeds the MPE limit. Once beyond the NOHD however, the
beam is considered completely eye safe since the irradiance falls below the MPE limit. It is
important to note, that eye exposure even within the NOHD will not automatically cause an eye
injury or is even likely to cause an injury. The NOHD is a “nominal” hazard distance, not an
actual hazard distance. Given the characteristics of the Ho:YAG laser wavelength in that it can
be partially absorbed through water, injuries to the cornea and the lens are possible, but not to the
retina[6].

Methodology
A panel of content experts who are members of the Canadian Endourology Group, was convened
to develop the scope and content of this best practice report based on the guidance of the CUA
Guidelines Committee. A systematic literature review was conducted in search of published
reports of eye damage associated with clinical use of the Ho:YAG laser. The search was
performed of the English-speaking literature using the Pubmed, Medline and Cochrane Library
databases and search items included: eye, cornea, endoscopy, urology, holmium and laser.
References obtained from this process were then reviewed and the articles examined for
relevance and inclusion. Following the systemic literature review, an international twitter poll
was conducted as well as direct contact with 7 Canadian academic and 23 US academic
institutions. Additionally, the various urological association websites were examined to
determine if any guidelines were available regarding Ho:YAG laser eye safety. Finally,
consultation was undertaken with a physicist in order to determine if our findings
/recommendations were consistent with the laser’s known properties. Herein we present the
results of the systematic review and survey findings and provide recommendations based on the
current evidence and contemporary practice.

Results
A total of 4 studies (1 review article, 3 original manuscripts) were identified and included[7-10].
A study by Althunayan et al reviewed The Manufacturer and User Facility Device Experience
(MAUDE) and the Rockwell Laser Industries Laser Accident Database from 1992-2012[9]. Both
databases are voluntary but mandatory reporting systems of adverse events (AE). The MAUDE
database, developed by the United States Food and Drug Administration, includes all medical