Impact of Access to Glaucoma Progression Analysis Results on Interobserver Agreement of the Subjective Assessment of Visual Field Progression by Glaucoma Experts

Abstract

Purpose: : To determine if the assessment of glaucomatous progression based on review of sequential visual fields by expert readers was influenced by access to the results of Humphrey Glaucoma Progression Analysis.

Methods: : Five serial Humphrey 24-2 visual fields from 100 eyes were collected during clinical monitoring of patients with glaucoma. Determinations of progression were made independently by five glaucoma experts. The glaucoma experts rated each sequence of fields with respect to progression as none, questionable, probable, and definite. These were subsequently dichotomized as progressed (rated probable or definite) or stable (rated none or questionable). The strength of interobserver agreement between expert readers was assessed with kappa (<0.4=poor; 0.4-0.75=fair to good; >0.75=excellent). In addition each eye was rated as either progressed or stable by (1) consensus (majority) of the five graders’ dichotomous choices and (2) the HFA II Humphrey field analyzer GPA software. Three months later the glaucoma experts re-rated the visual field sets, after they were assigned new subject identifiers and shuffled, this time with access to the GPA results. Kappa was calculated and expert consensus established for these second readings.

Results: : The first reading interobserver agreement kappa was 0.45. Kappa was similar, 0.44, upon masked re-reading of the visual field sets with reference to the GPA printout (P=0.90). On reading 1, expert consensus agreed with GPA on 78 eyes. On reading 2, in which the readers had access to the GPA printout at the time of their readings, expert consensus agreed with the GPA on 83 eyes. This net increase in agreement with GPA of 5 eyes was not statistically significant (p=0.27, McNemar's test).

Conclusions: : Reference to GPA determinations did not improve the level of agreement among the readers; nor did the agreement of expert consensus with GPA increase significantly.

Keywords: visual fields