6. Argon Laser Trabeculoplasty & Selective Laser Trabeculoplasty

What is the ultimate goal of Laser Trabeculoplasty

to increase outflow facility - thus reduce IOP

List the 4 various modalities of LPT

• Argon laser trabeculoplsty (ALT)

• Selective laser trabeculoplasty (SLT)

• Micropulse diode laser trabeculoplasty (MLT)

• Direct selective laser trabeculoplasty (DSLT)

list 4 indicationds for LPT

- OAG not adequately controlled on max tolerated medical therapy

- OAG in which compliance with medical therapy is less than optimal

- OAG in pt not willing to receive medical tx as initial therapy

- initial treatment in management of glaucoma & ocular hypertension for pt who medical therapy is not the best option for

LTP expected to lower IOP by ___% to ____%

20% to 25%

LTP IOP lower effects are equvalent to the lower effects of which class of anti-glaucoma meds

PGAs

(T/F) ALT, SLT and MLT all provide a different level of IOP lowering effect

FALSE

ALT; SLT; and MLT all have similar IOP lowering effects

the main difference between the procedures is the damage left behind

LTP is effective in ~ ___% of eyes... 5yrs after LTP is performed, ___% of those are still effective, and 10yrs after that ___-____% of those are still effective

75%

75%

80-90%

List 4 types of glaucoma that LTP effectively reduces the IOP in

- Primary open angle glaucoma

- Pigmentary glaucoma

- Pseudoexfoliation glaucoma

- Steroid -induced glaucoma

(T/F) Aphakic or pseudophakic pt are contraindicated for LTP

FALSE

not contraindicated - just less effect

(T/F) IOP control is likely to be diminished by cataract extraction post LPT

FALSE

IOP control remains post cataract surgery

An uncooperative pt is a (absolute/relative) contraindication to LTP

absolute

Inability to visualize the angle is a (absolute/relative) contraindication to LTP

absolute

(need to see what youre zapping!)

Uveitic glaucoma is a (absolute/relative) contraindication to LTP

absolute

(the procedure causes an inflammatory event - don't want to worsen the already present inflammatory condition)

NVG is a (absolute/relative) contraindication to LTP

absolute

(don't want to hit vessels)

Angle dysgenesis is a (absolute/relative) contraindication to LTP

absolute

(congenital, juvenile glc, ICE)

Prior 360 ALT procedure is a (absolute/relative) contraindication to LTP

absolute

(if you wanted to do ALT again)

not contraindicated

(if you were doing SLT of the previous ALT)

High pre-op IOP of >30mmHg with advanced ONH damage is a (absolute/relative) contraindication to LTP

relative

Low tension IOP is a (absolute/relative) contraindication to LTP

relative

(remote chance of inducing hypotony and then the procedure cannot be undone)

Previous LTP failure in the same or fellow eye is a (absolute/relative) contraindication to LTP

relative

Angle recession glaucoma is a (absolute/relative) contraindication to LTP

relative

(variable results... the IOP is high because the TM is physically damaged so it may not response how we would expect it to normally)

Pseudophakia or aphakia is a (absolute/relative) contraindication to LTP

relative

(just be aware there is a potentially higher failure rate)

Little or no trabecular pigments is a (absolute/relative) contraindication to LTP

relative

(get the best effect out of the procedure when there is more pigment)

Pt of a young age,

relative

(just be aware there is a potentially higher failure rate)

In LTP of all types, the chromophore target is ________

melanin

What is the color range and wavelength of the laser used in ALT lasers

green / blue-green

488 / 514 / 532 nm

What is the color range and wavelength of the laser used in SLT lasers

green

532 nm

What is the color range and wavelength of the laser used in MLT lasers

red

810 nm

(532/577?)

The MLT laser is (shorter/longer) than the others and is (less/more) absorbed by the melanin in the angle, causing it to penetrate the tissue (less/more) deeply

longer

less absorbed

more deeply

In ALT - the pulse duration is usually how long

0.1 seconds

In SLT - the pulse duration is usually how long

3 nanoseconds

In MLT - the pulse duration is usually how long

0.2 seconds divided into 100 microsecond pulses

(ALT/SLT/MLT) mechanism:

Thermally effects

- not destroys pigmented TM cells

MLT

(ALT/SLT/MLT) mechanism:

Selective destruction of pigmented TM cells without thermal or collateral damage

SLT

(ALT/SLT/MLT) mechanism:

Shrinkage of TM with adjacent stretching due to thermal damage with subsequent coagulative necrosis

ALT

(T/F) MLT is a repeatable procedure

TRUE

(T/F) SLT is a repeatable procedure

TRUE

(T/F) ALT is a repeatable procedure

FALSE

What is the end point of tx for MLT

no visible tissure

What is the end point of tx for SLT

small bubbles

What is the end point of tx for ALT

blanching (mild) to bubbles (intense)

(T/F) There is post op inflammation with MLT

FALSE

(T/F) There is post op inflammation with SLT

TRUE

(T/F) There is post op inflammation with ALT

TRUE

What is the spot size used for MLT

300um

What is the spot size used for SLT

400um

What is the spot size used for ALT

50um

(T/F) Each laser used for trabeculoplasty, uses a common pathway of events to reduce the IOP

TRUE

regardless of the differences in the physics

Describe the common mechanism that is shared among all LTP procedures

immediate release of cytokines followed by monocytic recruitment that facilitates greater permeability

(T/F) The clinically observable IOP-lowering effect is comparable among the various techniques of laser trabeculoplasy in the short term whether or not that technique causes structural damage

TRUE

What was established by the "Glaucoma Laser Treatment Trial"

established the efficacy and safety of laser trabeculoplasty

compared ALT to Timolol

concluded:

ALT may be better first line

What was established by the "SLT / Med Study"

established SLT as a safe/effective initial therapy in POAG or OHT

compared SLT to PGAs

List the 5 comparisons made between the LTP procedures that left them ordered as:

ALT < SLT < MLT

❑post-op complications decrease

❑dependence on topical medications decreases post-op

❑laser induced iatrogenic tissue damage decreases

❑earlier ability to use in glaucoma management algorithm

❑Effectiveness of repeat treatment increases

How do you differentiate between tissue images of ALT vs SLT vs MLT

ALT:

there is visible damage from where the tissue was exposure to the laser

SLT & MLT:

TM architecture remains intect w.y the signs of coagulation damage as seen in ALT

*images slide 16 and 17*

List the 5 reasons why ALT is generally not the preferred tx

1. current theory for chemical mechanism of action of all LTPs (no true need for the physical damage)

2. The Equivalent IOP control for each LTP mode

3. The similarity in the type of complications and their frequency

4. ALT is non-repeatable and has temporary efficacy

5. comparable IOP lower among all types of LTP in the short term, whether or not that technique causes structural damage.

(T/F) ALT may have a negative outcome on the effectiveness and efficiency of future TM surgery such as MIGs

TRUE

if the TM is damaged enough, decreases the efficacy of future surgeries like MIGs if the pt chooses to that down the road

List the 2 potential theories proposed regarding the mechanism of action of the "Mechanical Theory" of ALT

- ALT reverses the collapse of the TM thatMAY occur during the glaucomatous process

- The scarring process that follows the tx serves to tighten the collagenous ring which comprises the aqueous outflow pathway

ALT may be performed in pt with (1°/2°) (open/closed) angle glaucoma

1° or 2°

open angle

(must be able to see the angle)

Which 2 specific types of glaucoma does ALT procedure work best for, why

• Pigment Dispersion Glaucoma (PDG)

• Pseudoexfoliation Glaucoma (PXG)

because the laser targets pigment and both of these conditions present with a lot of TM pigment

Patients with IOP greater than ____mmHg do not do well with ALT

35mmHg

Patients under ___ years old do not do well with ALT

40yo

Pt with Pigment Dispersion Glaucoma do (well/not well) with ALT

well

Pt with Psuedoexfoliation Glaucoma do (well/not well) with ALT

well

Pt with Uveitic Glaucoma do (well/not well) with ALT

not well

Pt with angle recession do (well/not well) with ALT

not well

Pt with increased episcleral venous pressure do (well/not well) with ALT

not well

The location of the burns in ALT should be where

at the junction of the non-pigmented and pigmented TM

*image slide 22* & 25

With ALT, we generally tx _____° at one time, why

180°

gives option to treat second 180 at another time - because ALT cannot be performed twice in the same location

When doing ALT often treat the (superior/inferior) ____° first, why

inferior 180°

due to denser pigmentation

Prior to the LAT procedure, the pt is treated with which 2 drugs, what is the reason for each

Aproclonidine or Iopodine

- to decrease the severity of the IOP spike that followed the procedure

Pilocarpine

- to induce constriction and pull the iris as far out of the angle as possible

ALT is performed using a _______________ lens

Trabeculoplasty lens

Visible vapour bubbles during the ALT procedure are a sing of what

1. if mild... a sign that the therapy is working

2. if excessive... a sign that you are suing too much energy

ALT typically involves ___ laser spots per quadrant

25 laser spots

____% of pt who received ALT have IOP lowering at 1 year

90%

____% of pt who received ALT have IOP lowering at 5 years

50%

____% of pt who received ALT have IOP lowering at 10 years

30%

When does the maximum IOP fall occur post ALT

6-8 weeks

ist the 6 factors that contribute to the level of success of a pt receiving ALT tx

- pre-tx IOP

- phakic status/ocular surgery

- degree of TM pigment

- age

- ethnicity (AA)

- type of glc (PDG/PXG)

List the 7 complications seen with ALT

• Elevated IOP (up to 50 % if untreated)

• Rapid & progressive visual field loss

• PAS

• Anterior uveitis

• Hemorrhage

• Corneal edema

• Endothelial burns

What is the definition of SLT

a large spot procedure using single 3ns, 532nm-laser pulse to selectively destroy pigmented TM cells in accordance with principle of selective photothermolysis

Whrn is SLT indicated

for any primary or secondary open angle glaucoma pt

OR

in eyes that have failed previous ALT tx

SLT is (effective/ineffective) in eyes with steroid induced elevation in IOP

effective

(T/F) There is evidence showing a strong correlation between SLT procedure IOP reduction and TM pigmentation

TRUE

pt with increased TM pigment (or PDG/PXD) demonstrated a more favorable response to SLT

SLT can be repeated, so what is the reason that a doctor would choose to only tx 180° at a given time and not the full 360°

because still gets enough effect and decreases the amount of energy you are sending into the eye

(SLT/Meds) do a better job at flattening the IOP diurnal curve

SLT

(much less of a morning IOP spike)

(SLT/Latanoprost) does a better job at lowering IOP

equal IOP lower effects

(T/F) SLT has significantly better IOP lowering effects than ALT

FALSE

it has similar IOP lowering effects to ALT

ALT lowers the IOP in approx. ____% of the eyes

80%

ALT IOP lowering effect is not realized for up how long post/op

1 month

ALT on average reduces IOP by __-__ mmHg

6-9 mmHg

(T/F) Pt generally do not need any more tx after an ALT procedure

FALSE

after a few years additional treatment is generally neededto lower the IOP

(important to educate your pt on this)

SLT success is dependent on:

how much of the TM is treated

180° SLT tx lower the IOP in ___% of eyes on average ___mmHg

65% of eyes

4mmHg

360° SLT tx lower the IOP in ___% of eyes on average ___mmHg

almost 100%

11mmHg (or 40%)

After 360° of angle is treated by ALT, no further ALT is recommended... success rates of further ALT vary from ____ to ____%

21% to 73%

After 360° of angle is treated by SLT another 360° SLT treatment.... successful for at least ___ months-average decrease ___ mmHg after first SLT / ____ mmHg after 2nd

6 months

5mmHg after 1st

2.9mmHg after 2nd

SLT performed in eyes with previous ALT.... reduced IOP by ___ mmHg or more in ___% of eyes

5mmHg

57%

(ALT/SLT) shown to decrease diurnal IOP peak to trough

BOTH

and had fluctuation of similar amounts

(T/F) Both ALT and SLT shown to decrease IOP equal to drops

TRUE

Explain the general procedure of DSLT

- laser energy is delivered directly to the TM through the peripheral cornea and the limbus instead of via a gonioscopic lens across the anterior chamber to the TM

- delivers 120 pulses of 1.8 mJ, 532um in an automated circular and consecutive pattern

- 100 shots simultaneously to the TM through the limbus in 1.2 seconds

(T/F) Laser trabeculoplasty is a reasonable initial tx option

TRUE