G-30-1529-en
OPMI® VISU 160 on S8, S81 & S88 Suspension Systems
Issue 5.0
Printed on 09. 10. 2006
Safety
29
This is the reason why Carl Zeiss uses fiber optic illumination in its sur-
gical microscope systems.
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 to the phakic
eye (L
B
)”
5)
.
L
B
is the spectral radiance L(
λ
) integrated over the spectral range from
380 nm to 700 nm and weighted using B(
λ
):
where B(
λ
) is the spectral weighting function for the photochemical
hazard of the retina in the phakic eye.
The quantity L
B
= 500 mW/cm² sr is the reference value and is defined as
1.0 on the intensity scale of the suspension system
5)
. At this reference
value, photoretinitis might be expected to occur as a result of the micro-
scope illumination after a retinal exposure time totaling 10 minutes. This
applies to the exposure of a specific point on the retina with an uninter-
rupted illumination beam. In cataract surgery, instruments such as the
phacoemulsification handpiece, the use of fluids in the eye, manipulation
in and movements of the eye ensure that the illumination beam path is in-
terrupted. These are factors which considerably increase the period after
which photoretinitis might be expected to occur.
700
L
B
=
∑
L(
λ
) B(
λ
)
∆λ
380
