Bleb analysis using anterior segment optical coherence tomography after trabeculectomy with amniotic membrane transplantation

Abstract

Introduction: Little has been known about the intrableb structures associated with bleb function after trabeculectomy with amniotic membrane transplantation (AMT). The aim of this study is to analyze the characteristics of intrableb structures using anterior segment optical coherence tomography (AS-OCT) after trabeculectomy with AMT.

Methods: A total of 68 eyes of 68 patients with primary open-angle glaucoma who underwent trabeculectomy with AMT were included. Surgical success was defined as intraocular pressure (IOP) ≤ 18 mmHg and IOP reduction of ≥ 20% without medication on AS-OCT examination. Intrableb parameters, including bleb height, bleb wall thickness, striping layer thickness, bleb wall reflectivity, fluid-filled space score, fluid-filled space height, and microcyst formation were evaluated using AS-OCT. Logistic regression analysis was performed to determine factors associated with IOP control.

Results: Of the 68 eyes, 56 eyes were assigned to the success group and 12 eyes to the failure group. In the success group, bleb height (P = 0.009), bleb wall thickness (P = 0.001), striping layer thickness (P = 0.001), fluid-filled space score (P = 0.001), and frequency of microcyst formation (P = 0.001) were greater than those in the failure group. Bleb wall reflectivity was higher in the failure group than in the success group (P < 0.001). In the univariate logistic regression analysis, previous cataract surgery was significantly associated with surgical failure (odds ratio = 5.769, P = 0.032).

Conclusion: A posteriorly extending fluid-filled space, tall bleb with low reflectivity, and thick striping layer were characteristics of successful filtering blebs after trabeculectomy with AMT.

Fig 1. Surgical procedure of trabeculectomy with amniotic membrane transplantation.

(A) Amniotic membrane was peeled from the nitrocellulose membrane. (B) Amniotic membrane was placed over the scleral flap with the stromal side facing up. The limbal side of the amniotic membrane was secured to both sides of the scleral flap margin with two 10–0 nylon sutures. (C) Amniotic membrane was placed between the Tenon’s capsule and scleral flap. (D) The conjunctiva and Tenon’s capsule were closed with interrupted 10–0 nylon sutures.

Fig 2. Intrableb structure measurements.

(A) Vertical anterior segment optical coherence tomography (AS-OCT) scan of the bleb (B) Horizontal AS-OCT scan of the bleb. The white continuous and dotted two-way arrows indicate the bleb wall thickness and fluid-filled space height, respectively. The white arrow indicates the microcyst, and the asterisk indicates the fluid-filled space. The white arrow heads indicate the visible amniotic membrane beneath the bleb wall. The yellow two-way arrow indicates the hyporeflective layers with striping phenomenon.

Fig 3. Representative anterior segment optical coherence tomographic images of the fluid-filled space score (FFSS).

(A) FFSS 2. Fluid-filled space is diffuse and extends posteriorly beyond the field of the image view. (B) FFSS 1. Fluid-filled space is limited. (C) FFSS 0. No fluid-filled space is observed. Asterisks indicate fluid-filled spaces.

Fig 4. Boxplot of the intrableb parameters assessed with anterior segment optical coherence tomography after trabeculectomy with amniotic membrane transplantation for the comparison of the success and failure groups.

(A) Bleb was higher in the success group than that in the failure group. (B) Bleb wall was thicker in the success group than that in the failure group. (C) Stripping layer was thicker in the success groups than that in the failure group. (D) Bleb wall reflectivity was lower in the success group than that in the failure group. (E) Fluid-filled space score was greater than that in the failure group. (F) There was no significant difference in the fluid-filled space height between the two groups. (G) Microcyst formation was more frequently noted in the success group than in the failure group.

Fig 5. Representative images of AS-OCT.

Fig A-C represent a successful case and Fig D-F represent a failed case. (A) Slit-lamp photo of the bleb at 19 months after trabeculectomy with AMT. The IOP preoperatively was 21 mmHg and at the time of the AS-OCT examination was 7 mmHg. (B) Vertical AS-OCT scan of the bleb. The AS-OCT showed a tall bleb with a hyporeflective striping layer (yellow two-way arrows). Fluid-filled space (asterisk) extended posteriorly beyond the view of the image field. Amniotic membrane was noted even >19 months after surgery (white arrow head). (C) Horizontal AS-OCT scan of the bleb. The AS-OCT showed a diffuse fluid-filled space with the amniotic membrane (white arrow head). (D) Slit-lamp photo of the bleb at 6 months after trabeculectomy with AMT. The IOP preoperatively was 23 mmHg and at the time of the AS-OCT examination was 19 mmHg. (E) Vertical and (F) Horizontal AS-OCT scans of the bleb. The white arrow indicates the scleral flap. The bleb height was low, with limited fluid-filled space (asterisk) and no striping layer. AS-OCT, anterior segment optical coherence tomography; AMT, amniotic membrane transplantation; IOP, intraocular pressure.