Architectural analysis of modified trabeculectomy blebs using spectral-domain optical coherence tomography in a tertiary care centre

Abstract

Purpose: Slit-lamp examination and intraocular pressure (IOP) monitoring have been used as substitute marker for assessment of bleb functionality for ages. With the advent of optical coherence tomography (OCT), a noninvasive, fast imaging techniques, it can now being used to look for the internal morphology to predict the long-term functional viability of the bleb. Materials and Methods: It is a single centric, observational study analyzing 30 eyes with trabeculectomy and combined procedure (postoperative 2 months to 1 year). Any patient with resurgery, previous conjunctival disease, or systemic antimetabolite therapy was excluded. After all baseline evaluation, imaging of all blebs was done by spectral-domain OCT (RTVue Inc., Fremont, CA). The architecture was described and functional correlation was evaluated. The bleb wall thickness, vertical subconjunctival fluid height, and qualitative assessment of wall reflectivity were recorded for analysis. All data were analyzed Epi-info 7 software. Pearson's correlation and scatter diagram were used to look for nature of correlation between two variables, P < 0.05 was considered significant. Results: Sample was age and sex matched. The mean IOP was 12.5 ± 2.502 mmHg in functional bleb. We found a significant inverse correlation between vertical subconjunctival depths and bleb width by scatter diagram (P < 0.0001). In subgroup analysis, we found functional blebs had lower bleb wall thickness (P = 0.007) and larger vertical subconjunctival fluid pockets (P = 0.003). Conclusions: In vivo architecture of filtering blebs can be objectively described using spectral OCT. Various quantitative and qualitative parameters can be analyzed to document functionality of bleb. Functional blebs had thinner bleb wall and larger subconjunctival fluid, whereas nonfunctional blebs had thick wall with high reflectivity.