Comparison of two clinical Bleb grading systems

Abstract

Purpose: To evaluate 2 recently described grading systems for clinical grading of filtering surgery blebs: the Moorfields Bleb Grading System (MBGS) and the Indiana Bleb Appearance Grading Scale (IBAGS).

Design: Observational comparative study.

Participants: Twenty-four glaucoma filtering blebs in 24 eyes of 17 patients.

Methods: Three observers in a prospective agreement study compared MBGS with IBAGS during slit-lamp examination.

Main outcome measures: Comparison analyses were performed, including agreement, repeatability, and intraclass correlation coefficient (ICC).

Results: A wide range of bleb characteristics was represented in the cohort. Acceptable levels of intrasystem agreement were found in both systems: for IBAGS, overall agreement at the 0.5- and 1.0-unit levels were 80.6% and 97.6%, respectively, and for MBGS, these were 78.4% and 97.4% for morphologic and vascularity indices. Repeatability coefficients ranged from 0.5 to 1.4 for MBGS and 0.8 to 1.2 for IBAGS. The ICC values in the MBGS ranged from 0.18 to 0.72 for single measures and 0.39 to 0.88 for average measures. For IBAGS, the single-measure ICC values were between 0.06 and 0.53, and the average-measure ICC values were between 0.16 and 0.77. The MBGS ICC values for bleb size were higher than for IBAGS.

Conclusions: Both methods are reproducible clinically and had generally high levels of interobserver agreement. Both have minor deficiencies that should be amenable to improvement. The MBGS performed similarly to the IBAGS for reproducibility, had higher ICC values for morphologic features, and captured extra vascularity data with probable clinical implications.