Article Date: 4/1/2006

instrumental strategies
Tracking Glaucoma
New confocal scanning laser ophthalmoscope simplifies interpretation.
LEO SEMES, O.D.

Heidelberg Engineering has launched a new version of the Heidelberg Retinal Tomograph (HRT), the HRT3. This confocal scanning laser ophthalmoscope offers many features that improve its clinical utility. Hardware modifications, including a carrying case for the scan head and the ability to use a laptop computer to run the software, make the HRT3 truly portable. But probably the greatest achievement is the ability to apply the new software to existing HRT data, allowing current users to take advantage of these improvements.

The HRT3 features race-specific databases.

Improved analyses

The new HRT software uses an automated analysis for glaucoma damage called the Glaucoma Probability Score (GPS). It's based on a three-dimensional model of the entire HRT topographical image, including the optic disc and surrounding peripapillary retinal nerve fiber layer (RNFL). The 3-D modeling looks at the width, depth and rim slope of the optic disc as well as the RNFL profile. A neural network-like analysis calculates the probability that a patient's eye has structural characteristics consistent with glaucoma. The patient's scan is then classified as normal, borderline, or outside normal limits.

The HRT3 also has improved progression analysis. It displays the magnitude of the change as a color gradient, providing quantitative data on how much change has occurred in the significant areas. This is useful for comparing physical observations of the optic disc.  

You can also select the entire cluster of change and the device will automatically outline an area of contiguous damage. You can track the volume, as well as the area of change, over time. A progression printout provides change probability maps over time as well as the trend analysis of the area.

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The HRT 3

FOOTPRINT: Scan head: 12.5" x 14.5"; table: 36" x 23"
COST: $34,990 to $61,990
SOFTWARE FEATURES:
Glaucoma Probability Score, improved progression analysis.
IMAGE RESOLUTION:
384 x 384 pixels over a 15° x 15° field of view.
CAPTURES AN IMAGE:
In approximately three seconds; total time per patient is approximate-ly one to two minutes per eye.
 

New printouts are available with the HRT3 software for GPS analysis and progression results. The GPS printout provides the probability values for damage consistent with glaucoma, along with the resulting classification for both eyes together. The new standard OU printout also presents the results for both eyes, but displays the results based on the required contour line. This printout presents information on the integrity of the neuro-retinal rim and RNFL by comparing the patient's results with large and ethnic-specific databases.

A new African-American data-base is available for analysis of that particularly vulnerable population. There's also a database of Caucasian and Southeast Indian eyes.

New safeguards improve image quality. Real-time feedback on variables including focusing, camera alignment, illumination and optic disc centering, are provided before the image is taken.

The new HRT3 and its software developments offer powerful analyzes and printouts that simplify not only operation, but also clinical interpretation.

DR. SEMES IS ASSOCIATE PROFESSOR AND DIRECTOR OF CONTINUING EDUCATION AT UNIVERSITY OF ALABAMA BIRMINGHAM SCHOOL OF OPTOMETRY.



Optometric Management, Issue: April 2006