Laser Trabeculoplasty: A New Role in the Management of Open Angle Glaucoma?

L. Jay Katz, MD

ALT

Ambivalence

Advantages

• Relatively safe
• Technically easy
• Vision unaffected

Disadvantages

• Modest effect at best
• Ineffective in many
• Delayed response
  
  

ALT – IOP Spike

Rate markedly reduced by

Lower power
Better location
Fewer shots
Alpha agonists

Treatment Sequence

Max meds -> ALT -> filter
Well tolerated meds -> ALT -> filter
ALT -> meds -> filter (GLT)
Meds -> filter -> ALT (AGIS)
Filter -> ALT -> meds (CIGTS)

 

 

Glaucoma Laser Trial

Purpose
To assess the efficacy of ALT as an alternative to treatment with topical medication for controlling IOP in patients with newly diagnosed previously untreated POAG

Ophthalmology 97:1403,1990

 

• 271 patients
• newly Dx POAG
• Randomized to:

LF = ALT first eye
MF = timolol first eye

Resluts GLT

• IOP controlled ( 2 years)
  LF: 44% ALT

  70% ALT + timolol
  89% ALT + meds

  MF: 30% timolol

  66% meds
  

Glaucoma Laser Trial Follow-up Study (GLTFS)AJO 1995;120:718

• 203/271 patients
• Mean F/U: 7 years (max 9 years)
• 20% ALT alone (15% timolol alone)

Repeat ALT(Percent Failure at 1 Year)

Richter 67%

Ophthalmology 94:1085,1987

Feldman 79%

Ophthalmology 98:1061,1991

 

ALT Limitations

• Waning effect with longer follow-up
• Lack of repeatability (probably due to thermal damage to outflow system)

Development of SLT (Latina)

• Requirements of selective photothermolysis
• Target intracellular chromophore = melanin
• Absorption: target > surrounding tissue
• Short laser pulse confines heat to target
  

Comparison of the Morphological Changes after SLT and ALT in Human Eye Bank Eyes

• Kramer, Noecker Ophthalmol 2001;108:773
• SLT unlike ALT caused no coagulative damage

Mechanism of IOP ReductionProposed Models

• Mechanical stretching of trabecular beams
• Stimulation of endothelial cell replication
• Release of chemical mediators
  
  
  

Selective Laser Trabeculoplasty Vs Argon Laser Trabeculoplasty: A Prospective Randomized Clinical Trial

 

Damji et at, BJO June, 1999

 

SLT Wills Series

• 41 eyes of 38 patients
• 17 male/ 21 female
• Mean age = 76.7 years
• 34 white/ 3 Hispanic/ 1 AA
• 26 POAG/ 7 PXF/ 5 NTG

SLT Success Determined by% IOP Reduction

MONTH 3

 

SUCCESS

>15% 56.1%
>20% 43.9%
>25% 39.1%

Compassionate Protocols

 

20% or greater drop in IOP

latanoprost 43 % @ 3 mo
brimonidine 43% @ 6 mo
unoprostone 30% @ 2+mo

 

Reasons for Primary SLT?

• Glaucoma Medications
  - Side effects
  - Compliance
  - Tachyphylaxis
  - Cost
• Filtering Surgery
  - Complications
  - Lengthy rehabilitation
  
  

SLT Clinical Studies:Primary Treatment

Howes IGS 2001
26-31% reduction

Larsson IGS 2001
c/w ALT: 24% (vs 22%) at 6 mo

Melamed IGS 2003
primary Tx = >30%

 

 

SLT as Primary Treatment for Open-Angle Glaucoma:A Prospective, Nonrandomized Pilot Study

Melamed Arch Ophthalmol 2003;121:957-960

• 45 eyes (31 patients)
• Mean IOP drop = 7.7 mmHg (30%)
• 40 eyes > 5 mmHg drop (initial IOP 25.5)
  

New US Clinical Study

SLT/MED is a Prospective Randomized Controlled Clinical Trial comparing Selective Laser Trabeculoplasty Vs. Topical Medical Therapy as initial monotherapy

SLT/ Meds Primary Therapy

• Prospective, multicenter trial
• Randomized patients (not eyes)
• SLT 360/ SLT 180/ SLT 180
• Meds: current practice
  

Conclusions for SLT

• Comparable results to ALT and medication
• IOP reduction may be more dramatic in eyes without meds
• Repeatability needs to be clinically validated
• Unclear where SLT fits (primary therapy or as adjunct to failed medical therapy?)