Zeiss VISULAS YAG III, User Manual

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Operation of the device
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Using the aiming beam system with the
VISULAS YAG III/VISULAS YAG III Combi/
VISULAS Trion Combi
The VISULAS YAG III uses a four-point aiming beam system.
If the image is free from distortion, the following aiming beam spot patterns
can be seen, depending on the position of the focus:
Fig. 47 Focusing the aiming beam
When working with energies of up to 1.5 mJ, you can focus directly on the
target plane. The four spots then merge into a single spot. When working
with higher energies, you must use anterior or posterior defocusing,
depending on the individual situation (see Focus shift and defocusing , page
88).
Where there is astigmatic distortion, the aiming beam spot pattern will take
on a different appearance, usually exhibiting rhombic distortion.
In this case, it is not always possible to merge the four aiming beam spots
when focusing on the target plane. From this it should be clear, that in some
circumstances it may no longer be possible to achieve the desired effect at
low energy levels, as the therapy beam will be similarly distorted. It may be
necessary to use a higher energy level in order to achieve the desired effect.
Return to a normal energy level when a square aiming beam pattern is seen
and it is possible to merge the four aiming beam spots.
Fig. 48 Distorted aiming beam