Technical data

G-30-1682-en OPMI® Lumera® T Issue 4.0
Printed on 02. 02. 2009
Safety 27
Focus of the light source
Studies show that injuries are likely to occur if the filament of the light
source is imaged on the patient's retina. The peak intensity of a filament
is considerably higher than that of an even and extended light source
such as a light guide.
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 and aphakic eye should not
be exposed to the light source longer than a few minutes. In all surgical
cases, the retinal exposure time depends on the type and duration of the
procedure and possible case complications. It is therefore recommended
in ophthalmic surgery to keep the light intensity as low as possible, or to
use a device which prevents the light from entering through the patient's
pupil. It is also recommended to make sure that the patient's eye is not
additionally exposed to the light of surrounding light sources. This
problem has been solved by Carl Zeiss by the use of a retinal protection
device that can be swung into the microscope's illumination beam path
and a blue barrier filter (retina protection filter).
Brightness control
The brightness control scale of our systems has a linear structure with
values ranging from 0.5 to 10. The stipulations of standard ISO/FDIS
15004-2:2006(E) result in maximum radiation exposure times for the dif-
ferent illumination configurations as specified in the table "Maximum radi-
ation exposure times".
The microscope light source - like any bright light source - may present a
hazard to the patient's eye both in the form of immediately visible thermal
damage to the retina as well as phototoxic chemical reactions which may
lead to photoretinitis. The factors which play an important role in deter-
mining the phototoxic risk are:
– Lamp brightness.
– Spectral distribution of the light (UV and blue are more dangerous
than longer wavelengths).
– Duration of direct exposure.
– Pupil size.
– Clarity of ocular media (infants and young children, for example,
may be at a higher risk).