Laser Treatments for Glaucoma
The primary laser treatments for glaucoma are laser trabeculoplasty (including argon laser trabeculoplasty [ALT] and selective laser trabeculoplasty [SLT]), laser peripheral iridotomy, and cyclophotocoagulation procedures. 1
Main Laser Procedures
Laser Trabeculoplasty
Laser trabeculoplasty works by increasing aqueous humor outflow through the trabecular meshwork and is positioned as a second-line treatment after medication therapy in the standard treatment algorithm. 1, 2
Types of Trabeculoplasty:
Argon Laser Trabeculoplasty (ALT): The original laser trabeculoplasty technique that demonstrated IOP reduction of 9 mmHg in the Glaucoma Laser Trial, superior to topical timolol (7 mmHg) over 2 years 1
Selective Laser Trabeculoplasty (SLT): A newer technique that is non-inferior to ALT in IOP reduction and achieving treatment success, with the advantage of being repeatable unlike ALT 1, 3
SLT has a better safety profile than ALT, causing less postoperative pain and inflammation, with mild anterior chamber inflammation being the most common side effect 1
360-degree treatment with SLT is necessary to achieve comparable efficacy to prostaglandin analog therapy, as studies show 90 and 180-degree treatments have inferior IOP-lowering effects 1, 4
Cyclophotocoagulation Procedures
Cyclodestructive procedures reduce aqueous production by targeting the ciliary body and are traditionally reserved for refractory glaucomas. 1
Types of Cyclophotocoagulation:
Transscleral cyclophotocoagulation: Applied externally through the sclera, good for eyes with limited visual potential or poor candidates for incisional surgery 1
Endoscopic cyclophotocoagulation (ECP): Uses an 810-nm diode laser with direct visualization of ciliary processes, allowing better titration of treatment with IOP reduction of 34-57% 1
Micropulse transscleral cyclophotocoagulation: Delivers repetitive short bursts of diode laser energy with intervening rest periods, representing an alternative to traditional continuous-wave laser 1
Laser cyclophotocoagulation causes less postoperative pain and inflammation compared to cyclocryotherapy, which is now rarely used. 1
Other Laser Procedures
Laser peripheral iridotomy: Used primarily for angle-closure glaucoma, though long-term effectiveness for prevention of primary angle closure glaucoma remains undetermined 1
Laser iridoplasty: Adjunctive procedure for angle-closure situations 1
Treatment Algorithm Position
According to the American Academy of Ophthalmology, laser trabeculoplasty is indicated only after first-line and second-line medications have failed to control IOP. 2
Topical medications (prostaglandin analogs or beta-blockers) should be the initial treatment, with demonstrated IOP reduction of 25-49% in clinical trials 2
Laser trabeculoplasty is positioned as second-line treatment after medication failure or when patients cannot tolerate or adhere to medication regimens 2
Common Complications and Caveats
IOP spikes occur in 4.5-27% of eyes after SLT, similar to rates with ALT, with more heavily pigmented trabecular meshwork being more prone to pressure spikes 1
Cyclodestructive procedures carry risks including:
- Postoperative inflammation and pain 1
- Hypotony and cystoid macular edema 1
- Vision loss and rarely sympathetic ophthalmia 1
- Frequent need for repeat treatment weeks or months later 1
Perioperative management for laser trabeculoplasty requires:
- IOP check within 30 minutes to 2 hours after surgery 1
- Follow-up examination within 6 weeks or sooner if concern about IOP-related optic nerve damage 1
- Medications like brimonidine or apraclonidine may be used perioperatively to prevent temporary IOP elevations 1
Critical Evidence Considerations
The Glaucoma Laser Trial demonstrated that initial laser trabeculoplasty was at least as effective as topical timolol in preserving visual field and optic disc status over 5.5-9 years of follow-up. 1
A multicenter randomized trial showed similar IOP reduction with SLT and medication groups after 1 year, though the study may have had insufficient statistical power to detect differences 1
Documentation of medication trials and failures is essential before proceeding to laser procedures to establish medical necessity and avoid unnecessary interventions 2