Dynamic Early Changes in Trabeculectomy Blebs Assessed Using Ultrasound Biomicroscopy, 3-Dimensional-Optical Coherence Tomography (OCT) and Anterior Segment-OCT

Abstract

Purpose: : To demonstrate early changes in the internal structures of filtering blebs by using ultrasound biomicroscopy (UBM), 3-dimensional optical coherence tomography (OCT), and anterior segment OCT, and to determine the relationship of the early structures with different types of matured blebs and the final intraocular pressure (IOP).

Methods: : Thirty-two eyes of 28 patients who had undergone trabeculectomy with mitomycin C were examined using UBM (TOMEY), 3D OCT-1000 (TOPCON), and Visante (Carl Zeiss Meditec). The follow-up period was 3–8 months.

Results: : In 26 blebs (81%), the conjunctival vessels over scleral flaps had regressed, and the blebs became avascular within 1 month postsurgery (the regression phase); 22 (85%) of these had revascularized during 1–3 months postsurgery (the maturation phase), while 4 (15%) had remained avascular. During the regression phase, we found 3 types of bleb wall structures. The first type found in 15 eyes (47%) had the subconjunctival layer structure, probably representing loosely arranged connective tissue. On maturation, all these blebs had a uniformly low-reflective "spongy" wall and they subsequently revascularized. The final mean IOP of such blebs was the lowest (11.7 ± 3.3 mmHg). The second type of bleb wall found in 5 eyes (16%) had a uniform appearance with an episcleral fluid cavity. In this type, the reflectivity of the wall increased to varying extents during the maturation phase, and all these blebs subsequently revascularized. The final mean IOP was the highest in this type (19.6 ± 4.3 mmHg). The third type of bleb wall found in 12 eyes (38%) had varying sizes and numbers of cystoid spaces within the bleb walls. The final mean IOP in this type was 14.6 ± 5.1 mmHg. These blebs matured into 2 subtypes; 8 (67%) revascularized with a highly reflective bleb wall and 4 (33%) remained avascular with a subconjunctival clear space. The former exhibited the final mean IOP of 17.4 ± 2.0 mmHg; the latter, 9.0 ± 2.0 mmHg. The early postoperative bleb wall structure statistically correlated with the final IOP (P = 0.005, Kruskal-Wallis test).

Conclusions: : Our results suggest that the subconjunctival layer type of early postoperative bleb wall structure indicates the achievement of both a safe bleb wall (thick and vascularized) and good IOP control, whereas the other types suggest achievement of either of them. The early postoperative internal structures may be useful to predict types of filtering blebs and bleb function after maturation.

Keywords: imaging/image analysis: clinical • wound healing • conjunctiva