G-30-1416-en
OPMI® 1FR XY Surgical Microscope on S7 Floor Stand
Issue 4.0
Printed on 14. 11. 2007
Safety
17
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 using B(
λ
):
where B(
λ
) is the spectral weighting function for the photochemical ha-
zard 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 as recommended in
the ISO 10936-2 draft on surgical microscopes used in ophthalmic appli-
cations. At this reference value, photoretinitis might be expected to occur
as a result of the microscope illumination after a retinal exposure time to-
taling 10 minutes. This applies to the exposure of a specific point on the
retina with an uninterrupted illumination beam. In cataract surgery, instru-
ments such as the phacoemulsification handpiece, the use of fluids in the
eye, manipulation in and movements of the eye ensure that the illumina-
tion beam path is interrupted. These are factors which considerably
increase the period after which photoretinitis might be expected to occur.
700
L
B
=
∑
L(
λ
) B(
λ
)
Δλ
380
