specifics of anterior segment laser procedures a.l.t. & s.l.t. alone and in combination leland...
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Specifics of Anterior Segment LASER PROCEDURES
A.L.T. & S.L.T.ALONE AND IN COMBINATION
Leland Carr, O.D.Oklahoma College of OptometryNortheastern State University
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Thermal Laser Trabeculoplasty
• Indications: OPEN ANGLE Glaucomas• Must be able to “see” the angle
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Trabeculoplasty is appropriate for:
• Primary Open-angle glaucoma• Pigmentary Glaucoma• Pseudoexfoliative Glaucoma• Normal Tension Glaucoma• Angle-recession Glaucoma
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Trabeculoplasty may be appropriate for ANGLE RECESSION GLAUCOMA
• A.L.T.– Apply treatment to NON-recessed
angle
• S.L.T.– Apply treatment to NON-recessed
angle
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NSU-OCO Study
• Apply SLT to 360-degrees following Angle Recession---prior to development of ANGLE CLOSURE GLAUCOMA ?????
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Trabeculoplasty is NOT appropriate for:
• Primary Closed-angle Glaucomas• Secondary Closed-angle
Glaucomas• Inflammatory Glaucomas• Neovascular Glaucomas
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S.L.T. may be appropriate in the management of Primary Angle Closure Glaucoma
• Southeast Asian Study (6 centers)• 50 patients• Chronic Angle Closure Glaucoma
(“combined mechanism glaucoma”)• Dual Laser Therapy
– Peripheral Iridotomy– S.L.T.
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Mechanism(s) of action
• Mechanical Effects• Photobiostimulatory Effects
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Laser//Tissue Interaction• A.L.T.
– “thermal process”– MECHANICAL EFFECT– Laser energy converted to heat following absorption
by melanin– Significant peripheral heat-spread
• S.L.T.– “non thermal”– BIOSTIMULATORY EFFECT– Energy delivery is small and brief
• Only 1% the effective energy associated with A.L.T.– Energy absorbed very locally by melanin containing
cells– No heat build-up to thermal relaxation time of melanin
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A.L.T.’s impact on meshwork
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S.L.T.’s impact on meshwork
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Anecdotal Reports:
• “A.L.T. doesn’t work as well on pseudophakes as it does on phakic patients.”
• “S.L.T. seems to work equally well on phakic, aphakic, and pseudophakic patients.”
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A.L.T.
Performing Argon Laser Trabeculoplasy
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Perform Gonioscopy
• Obtain Informed Consent• Instill 1 gt. Iopidine or 1 gt.
Alphagan-P• (rarely) Instill 1 gt. 1-2%
Pilocarpine
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Performance of A.L.T.
• Treat 180 or 360 degrees?• 50 – micron spot (argon)• Approximately 60 burns per 180 degrees• Apply to anterior ½ of meshwork
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• Obtain “blanching” to whitening of tissue (adjust Power setting to obtain it)– Avoid “charcoaling”– Avoid “bubbling”– Avoid “blistering”
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Or……Just make it easy!
• Set power at 1000 mWatts
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Post-op
• Instill 1 gt Iopidine or 1 gt Alphagan-P
• Rx: PredForte 1 gt. q.i.d.• Rx: Continue all pretreatment
glaucoma medications– Including Prostamides!– If not currently using Mx, go with
Alphagan-P 1 gt t.i.d.
Recheck patient at 1 week
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Most often do LOWER angle first
• Most often do NOT retreat upon previously-treated meshwork!– 60% will benefit in terms of new IOP
lowering– 40% will NOT benefit, and will often
respond with a rise in IOP
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Be Patient…….
• Need to wait for 4-6 weeks to assess efficacy of A.L.T.
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Followup
• Continue ALL pre – treatment glaucoma medications, but consider tapering if ALT results warrant• Use Pred – forte to control iritis, only as needed• Avoid judging the effects for 4 – 6 weeks• Recheck adequacy of control each 3 months
– Especially likely to “drift” first two years
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S.L.T.Selective (wavelength) Laser Trabculoplasty
For Open Angle Forms of Glaucoma
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S.L.T. Basics
• Q-switched, Frequency-doubled Nd:YAG Laser System– Outputs 532 nm emission– Brief 3 nsec pulse– “Low Power” (Energy) burns
• Targets Pigmented Trabecular Meshwork Cells
• Minimal “peripheral damage” to non-pigmented cells and/or collagen
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Laser Trabeculoplasties;SPOT SIZES
• ARGON procedures:50 microns• DIODE procedures: 60 microns• S.L.T. procedures : 400
microns
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How is it working?
• “Gentle mechanical effect” (minor)– Reshaping meshwork anatomy and
mechanics– Less dramatic than the A.L.T. effect
• “Biostimulatory effect” (major)– Increased cellular metabolism– Increased cellular mitosis
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“Enhanced Housekeeping”
Stimulate macrophagesRelease cytokines
Remove metalloproteases
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S.L.T.
Performing Selective Wavelength Laser Trabeculoplasy
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Discontinue all glaucoma medications 1-2 weeks prior to S.L.T. (?????)
• Ellex SLT website • Mrs. Madhu Nagar• “I prefer to discontinue all
glaucoma medications prior to SLT, rather than post SLT. The higher the baseline IOP, the greater the IOP reduction.”
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Perform Gonioscopy
• Obtain Informed Consent• Instill 1 gt. Iopidine or 1 gt.
Alphagan-P• (rarely) Instill 1 gt. 1-2%
Pilocarpine
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S.L.T. Treatment Parameters• Wavelength: 532 nm• Pulse: 3 nsec• Spot: 400 microns• Energy per pulse: .6 to 1.2
mJoules• Shots: 45-55 “adjacent”• Location: inferior or nasal
180-degrees
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Laser Lens
• Goldman 3-Mirror• A.L.T. Trabeculoplasty Lens• Better to NOT use a Diode
Trabeculoplasty Lens
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Titrate the Energy Setting
• Start with around .6 mJoules• Gradually increase setting to
produce a visible “steam” of micro-bubbles upon firing the laser (viewed through the slit-lamp and laser lens)
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Or……Just make it easy!
• Set energy at 1.0mJ
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Best to Avoid the11:00 – 1:00 Zone?• Better to leave the meshwork
“virgin” in the area where a filtering procedure might need to enter the angle?
• Also Consider: The Advanced Glaucoma Intervention Study indicated that African-American patients have better surgical outcomes when A.L.T. is done prior to a filtering procedure
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Treat 180 or Treat 360 Degrees
• 180 advocates– Less risk of a laser-induced IOP spike– (Perhaps) advisable for Pigmentary
and Pseudoexfoliative Glaucoma patients
• 360 advocates– (Perhaps) greater IOP reduction– (Perhaps) longer duration of efficacy
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Post-Procedure
• Don’t use steroids unless an intense iritis occurs– Expect to see pigment immediately post-op
• Use Topical and Systemic Non-Steroidals– Acular, Nevanac, Voltaren (1 drop 4-5 times
daily)– Ibuprofen (two 200mg tables 4 x daily)– Treat for 3-4 days
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Don’t try to judge the efficacy for at least a month, and 6-8 weeks is really a better time for assessment of treatment success
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OUTCOMES• Expect all patients will require at
LEAST two separate treatments to produce a maximal effect!
• Best to wait at least 6 weeks before doing the second (and subsequent) treatments
• Works on over 70% of treated eyes• Expect a 22% to 28% reduction
from pre-treatment IOP
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When to retreat/repeat SLT?
• As soon as pressure starts rising again.
• No harm done by waiting until IOP surpasses target IOP…..but why wait?
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Medicare Exclusion:
• 10 Days• And you really want to wait for at least 6 weeks prior to a retreatment, anyway!
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Outcomes• Most often effects last a least one
year• Average SLT “usefulness” is 3 years• Do expect some loss of efficacy over
time• S.L.T. is repeatable• S.L.T. can be safely performed on
patients who have previously had Argon or Diode trabeculoplasties
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COMBINATION ALT/SLT
• Perform standard A.L.T.• As “drift” becomes apparent,
re-treat the meshwork using S.L.T.• Some experts consider that A.L.T.
pressure-lowering can be enhanced using immediate S.L.T.follow-up treatments– Maximal mechanical impact– Maximal biostimulatory impact
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S.L.T. can be tried on “failed” A.L.T. cases
• Studies have shown that up to 80% of “A.L.T. failures” can be successfully treated with S.L.T.
• Typical IOP reduction is approximately 22% from pre-S.L.T. baseline