Perimetry Instrument Comparison Study: Comparing the Diagnostic Performance of Four Threshold Perimetry Tests to Discriminate Between Healthy and ‘Glaucomatous’ Eyes (Interim Analysis)

Abstract

Purpose: : To consider interim results of the relative diagnostic performance of four threshold tests to discriminate between healthy and ‘glaucomatous’ eyes, defined by neuroretinal rim loss and intraocular pressure (IOP) level.

Methods: : One hundred and thirty-six from a planned 320 participants have been recruited and tested in a four centre study of perimetry instruments (mean age=58, range 18 to 83 years). Patient selection criteria were: (i) Heidelberg Retina Tomograph (HRT) Moorfields Regression Analysis (MRA) ‘Outside Normal Limits’; rim area >0.5mm² and (ii) IOP >21mmHg at referral; <26mmHg at time of testing. Healthy subjects had HRT MRA ‘Within Normal Limits’ and IOP ≤21mmHg. Thus, the reference standard for ‘glaucoma’ was independent of perimetry. One eye of each subject was tested on Standard Automated Perimetry (SAP, 24-2 SITA standard), Frequency Doubling Technology Perimetry (FDT, 24-2 ZEST), Heidelberg Edge Perimetry (HEP, 24-2 ASTA standard) and the Moorfields Motion Displacement Test (MDT, WEBS); order randomized and unreliable tests (false positive rate >15%) were repeated once. Sensitivity and specificity for different numbers of significantly depressed points (P <5%) were recorded. The areas under the receiver operating characteristic curves (AUC) were computed.

Results: : At approximately 95% specificity, the sensitivities were: SAP 32% (95% confidence interval [CI]: 23 to 43%); HEP 38% (95% CI: 28 to 49%); FDT 46% (95% CI: 35 to 56%); MDT 32% (95% CI: 23 to 43%). The AUCs were: SAP 73% (95% CI: 68 to 78%); HEP 79% (95% CI: 74 to 84%); FDT 77% (95% CI: 72 to 82%); MDT 72% (95% CI: 66 to 77%).

Conclusions: : The diagnostic performance of each of the four tests was similar in this group with very early glaucoma.Acknowledgement of collaborators: L.Tanga, M.Michelessi, F.Oddone (Bietti Foundation, Rome, Italy), G.Sharpe, P.Artes (Dalhousie University, Halifax, NS, Canada).

Keywords: visual fields