Evaluation of Heidelberg Retina Tomography (HRT 3) in Healthy Eyes

Abstract

 

Purpose:

 

Heidelberg Retina Tomograph HRT 3 software includes a larger normative database as compared to HRT II. A stereometric analysis that does not require the delineation of the disc margin and accordingly calculates a glaucoma probability score (GPS) is also included in the software. The purpose of this study was to test the performance of the HRT 3 normative database and GPS analysis in a group of healthy subjects and determine its agreement with HRT II.

 

Methods:

 

93 normal eyes (54 subjects) were scanned with HRT II and analyzed with both HRT II and HRT 3 software. The output stereometric parameters (linear cup/disc ratio, cup shape measure, rim area and volume, height variation contour and mean RNFL thickness) were compared to the normative database and classified as within normal limits (WNL), borderline (BL) or outside normal limits (ONL). The agreement (kappa) between the Moorfields regression analysis (MRA) of HRT II and HRT 3 and GPS classification was calculated.

 

Results:

 

Height variation contour had the highest specificity among the stereometric parameters with 100% of the eyes classified as WNL. Rim area had the lowest specificity (91%). Percentage distribution of diagnostic outcomes among the 3 different classifiers is shown in table. The agreement in the MRA classification between HRT II and HRT 3 was kappa=0.50, HRT II MRA and GPS kappa=0.25 and HRT 3 MRA and GPS kappa=0.22.  

 

Conclusions:

 

HRT 3 MRA and GPS had lower specificity than HRT II MRA with moderate to poor agreement between the classification methods.

 

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • optic disc • nerve fiber layer