Laser therapy for Open Angle Glaucoma Flashcards
(23 cards)
What are patient candidates for laser therapy for open angle glaucoma (OAG)?
Patients who are on max meds and progressing
* Compliance issues
* Poor drop instillation
* Cost, convenience, quality of life
* Side effects of drops
* Doctor preference
These factors influence the decision to proceed with laser therapy.
What is trabeculoplasty?
ALT/SLT
A procedure that involves burning the trabecular meshwork with laser light to increase aqueous outflow
This technique is used to treat open angle glaucoma.
What are the main types of laser trabeculoplasty?
Argon Laser Trabeculoplasty (ALT) and Selective Laser Trabeculoplasty (SLT)
ALT was more common in the 1990s, while SLT is now more frequently used.
What does the research support regarding ALT/SLT?
Research supports the use of ALT/SLT as first line treatment for open angle glaucoma
The American Academy of Ophthalmology prefers laser trabeculoplasty as initial therapy.
What are the indications for laser trabeculoplasty?
- Primary Open Angle Glaucoma (POAG)
- Normal Tension Glaucoma (NTG)
- Pigmentary Dispersion Glaucoma
- Pseudoexfoliative Glaucoma
- Ocular Hypertension
These conditions can benefit from laser treatment.
What are absolute contraindications for laser trabeculoplasty?
- Narrow Angle Glaucoma
- Angle Closure
- Inflammatory Glaucoma
- Angle Recession Glaucoma
- Neovascular Glaucoma
These conditions require immediate intervention and disqualify patients from laser therapy.
What are relative contraindications for ALT/ SLT?
Advanced POAG, Prior LTP that failed; <40 years of age; Hazy media, uncooperative patient/ unable to sit behind laser
What is Argon Laser Trabeculoplasty (ALT)?
Traditional form of laser therapy for glaucoma; used as a next step before filtering surgery
ALT involves mechanical and biological mechanisms to improve aqueous outflow.
What are the laser settings for ALT?
Power: 600 mW
Spot size: 50 um (fixed)
Duration: 0.1s (fixed)
Pulses: 1
Offset: none
These settings are crucial for effective treatment.
Where is the gonio mirror placed for ALT?
9 o’clock
allows for tx of inferior 180 degrees as mirror is rotated clockwise; inferior is most pigmented
What are the post-operative care steps after ALT?
- Remove laser lens and rinse eye if needed
- Instill 1 drop Alphagan (Brimonidine) or Iopidine
- Check IOP 30-60 minutes after the procedure
- Continue all glaucoma meds if applicable
- Prescribe Pred Forte qid x1 week
Monitoring IOP is essential after the procedure.
What are tissue endpoints for ALT?
pigment blanching, small bubble formation
How many burns for ALT?
45-60 burns per 180 degrees
placed ~2 spot sizes apart
~12-25 burns per gonio mirror
What are the complications/risks associated with ALT?
- IOP spike or elevation
- Inflammation
- Keratopathy
- Peripheral Anterior Synechiae (PAS)
- Corneal Burns
- Hemorrhage/Hyphema
Understanding these risks is important for patient management.
Why isn’t retreatment often done for ALT?
success rates much lower with higher risk of complications
50% require filtering procedure within 6 months to lower IOP
What is Selective Laser Trabeculoplasty (SLT)?
A newer, more gentle form of laser therapy for patients with glaucoma
SLT is used as a next step before filtering surgery and has a different mechanism compared to ALT.
What are the expected outcomes for SLT?
Expected IOP reduction: 20-30%
Long term outcome: 80% effective at 1 year; 50% effective at 5 years; 30% effective at 10 years
SLT tends to be most effective for 12-36 months.
What is the thermal relaxation time in the context of SLT?
The time required by melanin granules to convert electromagnetic energy into thermal energy
Melanin thermal relaxation time = 1 microsecond; SLT pulse duration = 3 nanoseconds. Explains why there is no thermal damage/ photocoagulation effect in SLT
What are the pre-operative settings for SLT?
- 1 gtt Alphagan (brimonidine) or Iopidine 15-30 minutes prior
- 1 drop pilocarpine 1% (optional)
- Energy: 0.6-1.2 mJ (depends on TM pigment)
- Spot size: 400 um (fixed)
- Duration: 3 ns (fixed)
- Pulses: 1
- Offset: none
These settings ensure optimal performance during the SLT procedure.
What are the post-operative care steps after SLT?
- Remove laser lens and rinse eye if needed
- Instill 1 drop Alphagan (Brimonidine) or Iopidine
- Check IOP 30-60 minutes after the procedure
- Continue all glaucoma meds if applicable
- Post-op anti-inflammatory drops: doctor preference
Topical NSAID prn x2 days; Ketorolac qid x5 days; Pred forte qid x5 days
How many shots for SLT?
45-60 per 180 degrees
~12-15 per mirror; can be 180 or 360 and in one or both eyes
What is the IOP reduction for Normal Tension Glaucoma after SLT?
14-16%
What is a potential complication of SLT in Pigment Dispersion?
Severe IOP spikes following the procedure (requires urgent trabeculectomy)
Can perform “test dose” of 10 shots at 0.3 mJ and recheck IOP; monitor IOP after each quadrant
