What surgical and laser options are available for primary open‑angle glaucoma when medical therapy fails?

Surgical and Laser Options for Primary Open-Angle Glaucoma After Medical Therapy Failure

When medical therapy fails to control primary open-angle glaucoma, trabeculectomy is the most effective surgical option, with laser trabeculoplasty serving as an intermediate step for patients who can tolerate additional intervention before incisional surgery. 1

Laser Trabeculoplasty Options

Selective Laser Trabeculoplasty (SLT)

• SLT is the preferred laser option due to less thermal damage to the trabecular meshwork compared to argon laser trabeculoplasty, with comparable IOP-lowering efficacy 1
• Achieves clinically significant IOP reduction in more than 75% of previously unoperated eyes 1
• Can be repeated with similar success rates to initial treatment, unlike argon laser trabeculoplasty which has nearly 90% failure by 2 years after repeat treatment 1
• Uses a 532 nm Q-switched frequency-doubled Nd:YAG laser that selectively targets pigmented trabecular meshwork cells 1
• IOP spikes occur in 4.5% to 27% of cases, with heavily pigmented trabecular meshwork at higher risk 1

Argon Laser Trabeculoplasty (ALT)

• Provides 30% IOP reduction initially but requires additional surgical treatment in 30-50% of eyes within 5 years 1
• Less favorable than SLT for repeat treatments due to increased thermal damage and higher complication rates 1
• Can be performed to 180 or 360 degrees, with 180-degree treatment reducing postoperative IOP elevation risk 1

Perioperative Laser Management

• Mandatory IOP check within 30 minutes to 2 hours post-laser to detect pressure spikes 1
• Prophylactic brimonidine or apraclonidine prevents immediate IOP elevation 1
• Follow-up examination required within 6 weeks, or sooner if severe optic nerve damage exists 1

Incisional Surgery

Trabeculectomy

• Trabeculectomy is the definitive surgical option when medications and laser therapy fail to control disease 1
• Provides the greatest IOP reduction (48-60% in clinical trials) compared to medical therapy (49%) or laser trabeculoplasty (30-38%) 1
• Can be considered as initial therapy in selected cases, though typically reserved for medical/laser failure 1
• The Advanced Glaucoma Intervention Study demonstrated that maintaining IOP reduction of 47% after surgical intervention protects against visual field deterioration in advanced glaucoma 1

Postoperative Trabeculectomy Protocol

• First examination must occur within 12-36 hours to evaluate visual acuity, IOP, and anterior segment status 2
• At least one additional visit during the first 1-2 weeks postoperatively 2
• Additional visits throughout a 3-month period for uncomplicated cases 2
• Most patients recover preoperative visual acuity within 1-2 months, with complete stabilization at 3 months 2
• Topical corticosteroids prescribed postoperatively and tapered appropriately, with monitoring for steroid-induced IOP elevation 2

Complications Requiring More Frequent Follow-up

• Flat or shallow anterior chamber 2
• Early bleb failure 2
• Increased inflammation 2
• Tenon's cyst or encapsulated bleb formation 2

Treatment Algorithm

Step 1: Optimize Medical Therapy

• Ensure maximum tolerated medical therapy has truly failed before proceeding 1
• Target IOP should be 25% or more below pretreatment levels 1

Step 2: Laser Trabeculoplasty

• SLT is preferred over ALT for initial laser intervention due to repeatability and lower complication profile 1
• Consider laser as bridge therapy before incisional surgery, particularly in patients with higher baseline IOP who achieve greater reduction 3
• Phakic patients achieve significantly greater IOP reduction (-4.55 mmHg) compared to pseudophakic patients (+2.75 mmHg) 3

Step 3: Trabeculectomy

• Proceed to trabeculectomy when laser therapy fails or is insufficient 1
• Mitomycin-enhanced trabeculectomy is the most favored intervention when progression continues despite normal IOP on maximum medical therapy 4
• Surgical outcome varies by race: patients with African ancestry may benefit from laser trabeculoplasty first, while Caucasian patients achieve better long-term results with trabeculectomy first 1

Critical Pitfalls to Avoid

• Do not perform repeat ALT after initial 360-degree treatment - success rate drops to less than 10% by 2 years with increased complication risk 1
• Do not delay trabeculectomy in rapidly progressing disease - the Advanced Glaucoma Intervention Study showed that maintaining lowest IOP group (47% reduction) protects against visual field deterioration 1
• Do not skip IOP checks within 2 hours post-laser - pressure spikes can cause additional optic nerve damage in already compromised eyes 1
• Ensure adequate trabecular meshwork visibility before attempting laser trabeculoplasty - insufficient open angle reduces effectiveness 1