Zeiss VISU 200, Инструкция по эксплуатации, Страница: 16 / 80

16
Safety
G-30-1439-en OPMI® VISU 200 BrightFlex™ Surgical Microscope Issue 3.0
Printed on 21. 11. 2002
This is the reason why fiber optic illumination is used in surgical micro-
scopes from Carl Zeiss.
Exposure time to light
According to some publications, the phakic or aphakic eye should not be
exposed to the light source longer than a few minutes. In every operation
the exposure of the retina to light is dependent on the type and duration
of surgery and on any complications which occur. It is therefore recom-
mended in ophthalmic surgery to keep the light intensity as low as pos-
sible, or to use a device which prevents the light from entering through the
patient's pupil. Also, the surrounding light sources should not cause addi-
tional strain to the patient's eye.
Carl Zeiss has provided an answer to this problem in the form of a swing-
in retinal protection device for insertion into the beam path of the surgical
microscope. This device ensures total eclipsing of the pupil, preventing
light from entering into the patient's eye. It can be swung out when a red
reflex is required.
Intensity scale
The intensity scale of our suspension system is calibrated in units of the
”Spectrally weighted radiance for the photochemical hazard of the phakic
eye (L
B
)”
L
B
is the spectral radiance integrated over the spectral range from 380 nm
to 700 nm and weighted with B(
λ
):
in which B(
λ
) is the spectral weighting function for the photochemical ha-
zard of the retina of the phakic eye.
The value L
B
= 500mW/cm² sr is the reference value and is defined as
1.0 on the intensity scale of the suspension system as recommended in
the ISO 10936-2 standard draft for surgical microscopes used in oph-
thalmic applications. At this reference value, photoretinitis might be ex-
pected to occur from the surgical microscope light source in a total retinal
exposure time of 10 minutes. This applies to the exposure of a specific
point on the retina with an uninterrupted illumination beam. In a cataract
procedure, instruments such as the phacoemulsification handpiece, the
700
L
B
=
∑
L(
λ
) B(
λ
)
∆λ
380