Comparison of objective tests in glaucoma - multifocal objective perimetry and heidelberg retinal tomography

Purpose: To compare two objective methods for examining glaucomatous damage involving functional and structural assessment. Methods: Patients were tested with multifocal objective perimetry using the AccuMap system (ObjectiVision) and by topographical analysis using the Heidelberg Retinal Tomograph HRT II (Heidelberg Engineering). 90 patients with glaucoma (abnormal discs and reproducible field defects) and 90 glaucoma suspects (normal fields, abnormal discs and/or IOP≷22mmHg) were tested on both systems. Inclusion criteria VAc ≷ 6/12, pupils ≷ 2.5mm. Abnormality on the VEP was defined as a cluster of three abnormal zones with 2 zones p<0.02 and/or an elevated AccuMap severity index (ASI) ≷ 30. For HRT the Moorfields classification was used. Correlations were performed between VEP mean amplitude deviation and ASI, with various HRT structural parameters and discriminant functions. Results: In glaucoma patients the tests were generally in agreement (81%) in terms of diagnosing glaucoma, but there were several cases where diagnosis was only confirmed on one of the tests. In suspects the agreement was much less. The best correlations were seen with ASI and HRT cup shape measure r=0.30, vertical CD ratio r=0.35, FSM discriminant function r=-0.4, and RB discriminant function r=-0.41. Conclusion: Glaucomatous changes can be identified in both structure and function using these two objective tests. While these changes appear to be occurring simultaneously in the majority of subjects, individual parameters did not correlate closely.