Visualization of Scleral Flap Patency in Glaucoma Filtering Blebs Using OCT

Purpose

To investigate the use of anterior-segment OCT (AS-OCT) to visualize the aqueous outflow pathway and patency of the scleral flap in glaucoma filtration surgery blebs.

Design

Cross-sectional study.

Subjects

Two hundred five filtering blebs of 112 patients with glaucoma who had undergone trabeculectomy (Trab, n = 97) or deep sclerectomy (DS, n = 108) surgery with/without mitomycin-C (MMC).

Methods

Swept-source AS-OCT raster slices were used to image the Trab and DS blebs in sagittal and coronal planes using a standardized protocol. Bleb appearances were classified into 4 categories based on the scleral flap and sclerostomy/trabeculo-descemet window (TDW) appearance: A—sclerostomy/TDW not visible; B—sclerostomy/TDW visible but scleral flap indiscriminate from sclera; C—scleral flap distinct but edges adherent to surrounding sclera; D—scleral flap edges non adherent to surrounding sclera.

Main Outcome Measures

Surgical outcomes were classified into complete success (CS) (intraocular pressure [IOP] ≤18 mmHg with no medications), qualified success (QS) (IOP ≤18 with medications), and failure (F) (IOP >18 mmHg).

Results

The proportions of CS, QS, and F in the Trab and DS cohorts were 45.0% and 29.6%, 33.0% and 31.5%, 22.0% and 38.9% respectively, with a median postoperative follow-up of 8.4 years (standard deviation 7.9; interquartile range 3.2–9.0). In QS and failed blebs, category C (Trab, 53.7%; DS, 52.5%) accounted for the majority of scleral flap appearances, followed by categories A and B. Category D (86.0%; 71.9%) accounted for the majority of appearances in Trab and DS blebs with CS. There was a significantly greater proportion of MMC use in categories C and D compared with categories A and B in both Trab (P < 0.0001) and DS (P = 0.02) cohorts, demonstrating the association of intraoperative MMC use with increased patency of the scleral flap.

Conclusions

Swept-source AS-OCT may be used to visualize the position and patency of the sclerostomy/TDW and scleral flap in relation to surrounding structures in both sagittal and coronal planes. Although free scleral flap edges are primarily correlated with MMC use, it may also correlate with surgical success. Anterior-segment OCT may be used to complement subjective bleb grading at the slit lamp in the assessment of filtering blebs.

Financial Disclosure(s)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.