Abstract
Purpose: :
To consider interim study results of the relative diagnostic precision and test duration of the screening strategies of three perimetry devices to discriminate between healthy and ‘glaucomatous’ eyes, defined by neuroretinal rim loss and intraocular pressure (IOP) level.
Methods: :
One-hundred and forty-two from a planned 320 participants have been recruited and tested in a four centre study of perimetry instruments (mean age=59, range [18, 83] years). Selection criteria for patients 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, a reference standard for ‘glaucoma’ was defined independent of visual fields. Each subject (one eye) underwent Humphrey Standard Automated Perimetry (SAP; Central 64-point screening), Frequency Doubling Technology perimetry (FDT1; C20 strategy) and Moorfields Motion Displacement Test (MDT; Rapid ESTA strategy). Sample sensitivity was calculated for each device at a fixed specificity of 95%.
Results: :
So far 83 ‘glaucoma’ and 59 healthy subjects have been recruited. At 95% specificity (95% CI 85.6 to 98.9% with the current sample size), the sensitivity was: SAP 38% (95% confidence interval [CI]: 29 to 47%); FDT1 36% (95% CI: 27 to 44%); MDT 37% (95% CI: 28 to 46%). The average test duration of MDT (mean: 98, range 73 to175, seconds) was significantly quicker than SAP (mean: 164, range 122 to 284, seconds) (P<0.001). The average test duration of FDP1 (mean: 55 range, 31 to 143, seconds) was quicker than the screening protocols of the other instruments.
Conclusions: :
This interim analysis suggests that the relative diagnostic precision of the screening strategies for SAP (64-point screening), FDT1 (C20), MDT (ESTA) in the clinic-based population of early glaucoma patients are equivalent. FDT1 (17 test points) and MDT (32 test points) are quicker to perform than the SAP screening strategy.Acknowledgement of collaborators: L.Tanga, M.Michelessi, F.Oddone (Bietti Foundation, Rome, Italy), G.Sharpe, P.Artes (Dalhousie University, Halifax, NS, Canada), C. Balian, J. Flanagan (University of Waterloo, Toronto, ON, Canada)