What is sunken flap syndrome in a patient with a history of glaucoma who has undergone trabeculectomy surgery?

What is Sunken Flap Syndrome?

Sunken flap syndrome is not a recognized complication of trabeculectomy surgery in glaucoma patients based on the available evidence. The provided guidelines and research do not describe or reference this condition.

Recognized Post-Trabeculectomy Complications

The American Academy of Ophthalmology identifies several well-established complications following trabeculectomy that may be confused with "sunken flap syndrome":

Hypotony and Hypotony Maculopathy

• Hypotony occurs when intraocular pressure becomes excessively low, particularly when antifibrotic agents like mitomycin-C are used during surgery 1
• Hypotony maculopathy represents vision-threatening macular changes secondary to persistently low IOP 1
• This complication can cause visual acuity to decrease to 20/200 or worse 2
• Resuturing the scleral flap can reverse hypotony and restore visual acuity to 20/25 or better by limiting excessive filtration 2

Bleb-Related Complications

• Late-onset bleb leak occurs as a recognized complication of antifibrotic use, requiring intervention to prevent infection 1, 3
• Encysted or elevated blebs can develop in approximately 10% of patients within the first 2 months post-operatively, causing elevated IOP rather than hypotony 4
• Bleb dysesthesia may require surgical revision 5

Management Algorithm for Post-Trabeculectomy Hypotony

If you are referring to a flat or "sunken" anterior chamber with hypotony:

1. Initial assessment: Determine if hypotony is present (IOP typically <6 mmHg) and whether bleb leak exists 1

2. Conservative management first:

   • Medical therapy with IOP-lowering medication adjustments 4
   • Continued corticosteroid drops 4
   • For thin avascular blebs without leak, consider doxycycline to improve conjunctival vascularity 3

3. Surgical intervention if conservative measures fail after 6-24 weeks:

   • Resuture the scleral flap to limit excessive filtration 2
   • For bleb leaks: conjunctival advancement or free conjunctival autograft 3, 5
   • Surgical revision achieves 63% overall success rate with 80% cumulative success at 1 year 5

Critical Pitfall

Do not confuse early postoperative hypotony with surgical failure requiring immediate revision—many cases respond to medical management alone, and premature surgical intervention may compromise long-term IOP control 4.