LightLas 532 – Operator's Manual Rev. No 01 Page 27 of 115
heat energy which raises the temperature of the tissue being treated producing
thermal coagulation of the protein. The green laser beam is readily transmitted
through the cornea, lens, and vitreous regions of the eye. If the patient’s eye does
not allow for good transmission or introduces some dispersion of the beam then the
patient is not suitable for this type of laser treatment. Increasing the laser power and
pulse duration will generate more heat and therefore the coagulative effect will be
greater.
If the power or duration of exposure is too high then the surrounding tissue may
sustain some damage. Therefore, a careful selection of the power and pulse
duration is essential to a successful treatment.
Different Types of LDU
For the Slitlamp Delivery Units and LIO, the laser beam is delivered into the patient’s
eye as a focused spot that can be positioned accurately by the doctor to the
treatment site. When using the LIO the laser beam is delivered through a Contact
Lens that is held by the doctor and assists in positioning the laser beam on the site
and setting the desired spot size. For the Slitlamp delivery unit the spot size at the
treatment site is adjustable and set by the doctor according to the type of treatment
to be used. The spot size selector is located on the delivery unit attached to the
Slitlamp and can be set from 50µm to 1000µm in a continuous adjustment for the
Integrated SL980 design. As for Attachment LDU, it can be selected from 50m to
500m.
When using the Endoprobes, the doctor will use an Operating Microscope to view
the patient’s eye. These probes are inserted into the eye and used in very close
proximity to the treatment site (almost in contact). The Endoprobes are sterile
devices intended for direct patient contact and are a purchased item with a sterility
guarantee.
For each LDU, a “Delivery Key” is used by the laser console as a means of
determining which type of LDU is connected. The Delivery Key is required because
each type of LDU has a different amount of loss through the optical elements and
therefore the output power factor calibration will be different for each. The
Endoprobes have the least loss of all the LDU’s because the only losses are through
the fiber itself and in the coupling of the laser beam into the fiber. The LIO has more
loss than the Endoprobes as it has a collimating system, mirror, and focusing lens for
the laser beam to be transmitted through and all of these have some contributing
losses. The least efficient of the LDU’s is the Slitlamp delivery unit. There are many
optics in this unit due to the spot size adjustment zoom system so the losses are the
greatest. Also when the small spot sizes are selected there may be some aperture of
the beam that contributes to the losses.
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