Leaf User Manual
P/N: 97-4000, Revision 08, Release date: 2020-11-10 Page 56 of 85
Because prolonged intense light exposure can damage the retina, the use of the
device for ocular examination should not be unnecessarily prolonged and the
brightness setting should not exceed what is needed to provide clear visualization of
the target structures. This device should be used with filters that eliminate UV
radiation (<400 nm) and, whenever possible, short-wavelength blue light (<420 nm).
The retinal exposure dose for a photochemical hazard is a product of the radiance and
the exposure time. If the value of radiance were reduced in half, twice the time would
be needed to reach the maximum exposure limit.
While no acute optical radiation hazards have been identified for slit lamps, it is
recommended that the intensity of light directed into the patient’s eye be limited to the
minimum level that is necessary for diagnosis. Infants, aphakes and persons with
diseased eyes will be at greater risk. The risk may also increase if the person being
examined has had any exposure with the same instrument or any other ophthalmic
instrument using a visible light source during the previous 24 hours. This will apply
particularly if the eye has been exposed to retinal photography.
The red diode laser aiming beam has an average power varying from barely visible to 1
mW maximum. The safe (Class II) exposure duration limit at a maximum power level of
1 mW is 3.9 seconds. To protect the patient from possible retinal damage during
treatment, use the lowest practical aiming beam intensity and the minimal required time
duration.
Laser Safety Eyewear
Laser safety eyewear is routinely required with most lasers. When using Norlase Leaf,
the laser safety officer should determine the need for safety eyewear based on the
Maximum Permissible Exposure (MPE), Nominal Hazard Zone (NHZ) and the Nominal
Ocular Hazard Distance (NOHD) for each of the available laser wavelengths, as well
as the wavelength itself and the configuration of the treatment room (usually within the
controlled area).
ANSI Standard Z136.1-2007 defines MPE as “the level of radiation to which a person
may be exposed without hazardous effect or adverse biological changes in the eye or
skin”; the NHZ as “the space within which the level of direct, reflected or scattered
radiation during normal operation is not expected to exceed the applicable MPE”; and
the NOHD as “the distance along the axis of the unobstructed beam from the laser to
the human eye beyond which the irradiance or radiant exposure during operation is not
expected to exceed the appropriate MPE.”
The NOHD is measured from the slit lamp and delivery system laser aperture. ANSI
defines the controlled areas as “an area where the occupancy and activity of those
within is subject to control and supervision for the purpose of protection from laser
radiation hazards.”
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