2
IRIDEX IQ 577
®
/IQ 532
®
Laser Systems Operator Manual
15510-EN Rev G
MicroPulse (Optional)
MicroPulse (
μ
P) is a laser delivery consisting of a group of microsecond bursts.
Duty Cycle% =
μP Duration
× 100
μP
Duration
+
μP
Interval
MicroPulse is typically used to administer subvisible threshold laser treatments to macular
and perimacular targets. When used here, the terms “subvisible”, “subvisible threshold”
or “subthreshold” denote that the desired endpoint is one in which treated tissue offers no
ophthalmoscopically observable laser effects. Nevertheless, 577 nm and 810 nm studies have
confirmed that subvisible laser treatment strategies can be clinically effective while inducing no
changes discernible by slit lamp observation, fluorescein angiography (FA), fundus autofluorescence
(FAF), or at any time postoperatively.
1,2
Tissues receiving subvisible MicroPulse laser treatment show no such changes because:
• MicroPulse laser delivery is being used instead of CW, and
• The total laser energy of such doses is only a percentage (often chosen by clinicians to be 20-70%)
of that energy needed to produce a visible endpoint.
Energy (J) is equal to [Laser Power (W)]
×
[Exposure Duration(s)]
×
[Duty Factor (%/100)]. Duty Factor
is often 5% to 15% when using MicroPulse mode, and is 100% when using CW mode. Clinicians have
reported various strategies to adjust these parameters relative to suprathreshold burns in order to
achieve clinically effective subvisible endpoints.
1-4
Additional parameters to consider in any laser treatment protocol, and particularly during
MicroPulse, is spacing between laser treatment spots, and the total number of treatment spots
administered. Due to the limited thermal spread of MicroPulse exposures, subvisible treatments often
call for the administration of a greater number of treatment spots with denser spacing than that used
for threshold laser grid treatments.
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MicroPulse
μP
Interval
μP
Duration
Pulse Envelope
Duration
Pulse Envelope
Interval
Time (ms)
Power (W)
