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

CarrLW@nsuok.edu

Thermal Laser Trabeculoplasty

• Indications: OPEN ANGLE Glaucomas• Must be able to “see” the angle

Trabeculoplasty is appropriate for:

• Primary Open-angle glaucoma• Pigmentary Glaucoma• Pseudoexfoliative Glaucoma• Normal Tension Glaucoma• Angle-recession Glaucoma

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

NSU-OCO Study

• Apply SLT to 360-degrees following Angle Recession---prior to development of ANGLE CLOSURE GLAUCOMA ?????

Trabeculoplasty is NOT appropriate for:

• Primary Closed-angle Glaucomas• Secondary Closed-angle

Glaucomas• Inflammatory Glaucomas• Neovascular Glaucomas

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.

Mechanism(s) of action

• Mechanical Effects• Photobiostimulatory Effects

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

A.L.T.’s impact on meshwork

S.L.T.’s impact on meshwork

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.”

A.L.T.

Performing Argon Laser Trabeculoplasy

Perform Gonioscopy

• Obtain Informed Consent• Instill 1 gt. Iopidine or 1 gt.

Alphagan-P• (rarely) Instill 1 gt. 1-2%

Pilocarpine

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

• Obtain “blanching” to whitening of tissue (adjust Power setting to obtain it)– Avoid “charcoaling”– Avoid “bubbling”– Avoid “blistering”

Or……Just make it easy!

• Set power at 1000 mWatts

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

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

Be Patient…….

• Need to wait for 4-6 weeks to assess efficacy of A.L.T.

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

S.L.T.Selective (wavelength) Laser Trabculoplasty

For Open Angle Forms of Glaucoma

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

Laser Trabeculoplasties;SPOT SIZES

• ARGON procedures:50 microns• DIODE procedures: 60 microns• S.L.T. procedures : 400

microns

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

“Enhanced Housekeeping”

Stimulate macrophagesRelease cytokines

Remove metalloproteases

S.L.T.

Performing Selective Wavelength Laser Trabeculoplasy

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.”

Perform Gonioscopy

• Obtain Informed Consent• Instill 1 gt. Iopidine or 1 gt.

Alphagan-P• (rarely) Instill 1 gt. 1-2%

Pilocarpine

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

Laser Lens

• Goldman 3-Mirror• A.L.T. Trabeculoplasty Lens• Better to NOT use a Diode

Trabeculoplasty Lens

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)

Or……Just make it easy!

• Set energy at 1.0mJ

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

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

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

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

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

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?

Medicare Exclusion:

• 10 Days• And you really want to wait for at least 6 weeks prior to a retreatment, anyway!

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

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

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