This is a retrospective cross-sectional study of bleb morphology evaluated by modified IBAGS and AS-OCT. Enrolled in this study were POAG patients who underwent TLE and were consecutively recruited when they came for routine follow-up visits at the Japanese Red Cross Medical Center from July 2007 to March 2008. Patients with secondary glaucoma due to pseudo-exfoliation, uveitis, or neovascular glaucoma and those within the 1-year follow-up period after TLE were excluded from this study. The methods of TLE were divided into the following two groups: limbal-based conjunctiva (group I) and fornix-based conjunctiva (group II). Except for the incision area (location), the method of TLE was the same in both groups. The size of the conjunctival flap and TLE were 4.0 × 4.0 mm and 1.5 × 3.0 mm, respectively. Mitomycin C with a concentration of 0.04% was topically applied under and over the flap and 5 to 7 mm away from the edge of the flap for 3 minutes in all cases. Written informed consent was obtained from all patients, and the study was approved by the institutional review board of the Japanese Red Cross Medical Center and conducted in accordance with tenets set forth in the Declaration of Helsinki. In an attempt to ascertain reproducibility of modified IBAGS, every patient was evaluated by two of the authors (TH, TO) independently using slit-lamp microscopy. If the results of those evaluations differed, a third author (SS) assessed them using the bleb photographs. The Seidel test was evaluated only by the first author. For bleb analysis, bleb height (Z1), bleb extent (Z2), vascularity (Z3), and Seidel (Z4) were evaluated by modified IBAGS. For the assessment of IBAGS bleb height (Z1), grading was dividing into one of the following five stages (H0–4): H0: no bleb, H1: less than the corneal thickness (CT), H2: 1 CT < H2 ≤ 2 CT, H3: 2 CT < H3 ≤ 3 CT, and H4: H4 > 3 CT. The bleb was then imaged on the same day using AS-OCT (ZEISS Visante OCT Model 1000; Carl Zeiss Meditec, Dublin, CA).
2 In a sitting position, the subject was asked to look down and the upper lid was gently retracted to expose the bleb as fully as possible in the superior bulbar conjunctiva. Taking care to avoid pressure on the globe and bleb, four directions of standard AS-OCT images were obtained for each bleb, as shown in
Figure 1A. Every scan was adjusted to the center of the scleral flap. Each AS-OCT scan image was obtained and printed at the size of 7.3 × 18.6 cm, and the following various parameters were obtained: inside area of the bleb in cut B∼D (X1∼3 = height in B∼D × extent, maximum: X
1∼3max), height of the bleb in cut B∼D (X4∼6, maximum: X
4∼6max), extent of the bleb in cut A (X7), bleb wall thickness in cut B∼D (X8∼10, minimum: X
8∼10min), existence of CCD in cut B∼D (X11), extent of LUSF in cut B∼D (X12∼14, maximum: X
12∼14max), the height of LUSF in cut B∼D (X15∼17, maximum: X
15∼17max), and the area of LUSF (X18 = X12∼14 × X15∼17, maximum: X
18max = X
12∼14max × X
15∼17max). Bleb wall thickness was defined as the distance between the first reflective signals of the conjunctiva to the top of the subconjunctival fluid space. If subconjunctival space was not observed, the bleb wall was regarded as unmeasurable. Height of the bleb was defined as the distance between the first reflective signals of the conjunctiva to perpendicular to the sclera at the highest of the images (
Fig. 1B). Height of the bleb was measured at the maximum area. Extent of the bleb (
Fig. 1C) (X7) was measured at the length of the bulging part of the bleb in cut A in
Figure 1A. All of the measurement values except height and extent in AS-OCT were expressed as actual size on the printed images. Height in AS-OCT was classified into one of the five stages (H0–4) by comparing CT at the limbus. Extent in AS-OCT was expressed by the same four stages with IBAGS (E0: 0 < 1 Clock Hours, E1: 1–2 Clock Hours, E2: 2 < Clock Hours < 4, and E3: Clock Hours ≥ 4). We defined LUSF as the fluid space (lake) under the scleral flap. The existence of CCD was defined as positive if ciliary body and/or choroidal detachment were observed. For the purpose of analysis, the status of postoperative IOP was classified into the following three criteria: “excellent” (postoperative IOP ≤ 20 mm Hg and ≥30% reduction of preoperative IOP), “good” (postoperative IOP ≤ 20 mm Hg and ≥20% reduction of preoperative IOP), and “fail” (postoperative IOP ≥ 21 mm Hg or ≤20% reduction of preoperative IOP). Success in IOP control was defined as the eyes that showed excellent and good IOP control.