Elsevier

Ophthalmology

Volume 113, Issue 1, January 2006, Pages 77-83
Ophthalmology

Original Article
Comparison of Two Clinical Bleb Grading Systems

https://doi.org/10.1016/j.ophtha.2005.06.037Get rights and content

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.

Section snippets

Patients and Blebs

Sequential patients with filtering blebs were recruited from the glaucoma service outpatient department at the glaucoma clinic, Wellington Hospital. Local Ethics Committee approval was granted and all patients gave informed consent for clinical grading at the slit lamp of their bleb appearances.

A prospective interobserver and intermethod agreement study of 24 blebs of 17 consecutive patients that had previous glaucoma surgery was conducted, with grading at the slit lamp conducted independently

Bleb Characteristics

Twenty-four blebs of 17 consecutive patients were graded, with a bleb age range of 1 week to 12 years after surgery. Seventeen blebs were treated with adjunctive mitomycin C at the time of surgery, 3 blebs had 5-fluorouracil, 2 blebs had no antimetabolite, and the remaining 2 blebs did not have details of adjunctive treatment available.

Although the study group was a representative group of consecutive patients from a glaucoma clinic, a reasonably wide variety of bleb types and range of

Discussion

Both of the bleb grading systems performed adequately. The IBAGS was easier to use and performed very well for variability, but had relatively few steps (3- to 4-point scale for most parameters) and may have reduced fidelity as a result. The MBGS was more complex and generally had more steps in the grading scale. Variability was comparable, despite the increased scale of possible values in the MBGS. All graders were inclined to grade avascularity as a score of 0, as in the IBAGS. There was some

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    Manuscript no. 2005-390.

    Supported by a grant from the Capital Vision Research Trust, Wellington, New Zealand.

    The authors have no financial interests in the article.

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