Henson 7000: Technical profile

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Henson 7000: Technical profile

Henson 7000 glacuoma screenerFast, accurate, portable glaucoma screening

Designed to suit the constraints of the small consulting room or the mobile nature of domiciliary practice, the portable, durable Henson 7000 brings complete flexibility to glaucoma screening.

Henson 7000 glaucoma screening test patterns can be extended from 26 to 68 points, missed locations can be re-tested and new locations can be manually added in-test. Operators can efficiently rule out those who don’t have any visual field loss, confidently rule in those who do and accurately map the extent of any defect. Further details.

Technical specification | 7000 vs 9000FAQs

Henson screening tests

 

The Henson 7000 offers single and multiple stimulus screening tests defined by their sensitivity, specificity and speed. Whilst the 7000 offers both 26 and 68 point tests, the Henson 9000 also offers a 136 point test option, along with a binocular Esterman visual field test.

The Henson 7000 is perfectly suited to central visual field screening (whilst the Henson 9000 is additionally equipped with threshold testing capability).

For more information on how the machines differ see our comparison technical specification for the two machines here.

Glaucoma screening in context

Historically, two important criteria have defined a good glaucoma test:

  • Sensitivity: the percentage of glaucomatous subjects successfully detected
  • Specificity: the percentage of non-glaucomatous subjects that pass the test

100% sensitivity and 100% specificity will never be achieved – there will always be a few ‘false negatives’ (patients with glaucoma who pass the test) and a few ‘false positives’ who fail it.

But what of speed?

Speed is another criterion for successful glaucoma screening whose importance is often overlooked. Speed is of benefit to busy professionals and of comfort to patients, too, so a good screening test should be fast and easy to apply.

Previously sensitivity, specificity and speed have been mutually exclusive – if a faster test was required, sensitivity or specificity were sacrificed.

Good design can make a big difference and that is where the Henson range scores over its competitors – it is built to deliver fast screening without compromising performance.

Sensitivity with the Henson 7000

High sensitivity       

The types of visual field defects peculiar to glaucoma are more likely to occur in certain visual field locations than in others.

This topic has been researched by Professor David Henson who established where the locations for an early visual field defect are most likely to be. Henson’s research demonstrates that you do not need a large number of stimuli to develop a highly sensitive glaucoma screening test. The graph below shows the relationship between sensitivity and the number of test stimuli.

The graph below illustrates that with just 26 optimally placed stimuli very high sensitivity (almost 100%) to early visual field loss can be achieved.

Figure 1: The sensitivity and specificity of the optimized test patterns with increasing numbers of test locations. The solid line represents a logarithmic relationship between the sensitivity and increased test locations and the dashed line represents a linear relationship between the specificity and increased test locations. From Wang Y, Henson DB. ‘Diagnostic Performance of Visual Field Test Using Subsets of the 24-2 Test Pattern for Early Glaucomatous Field Loss’ in Investigative Ophthalmology & Vision Sciences. 2013;54:756-761.

Specificity with the Henson 7000

High specificity     

The Henson 9000 glaucoma screening test ensures specificity of over 95% by:

  1. Repeating measures at locations where a stimulus has been missed.
    In the Henson a stimulus has to be missed twice at any given test location before it is recorded as a miss. This alone reduces false positives.
  2. The extension of the test to additional locations.
    Extensions take the number of test stimuli within the central 26 degree field to 68 and then 136 positions. This allows the clinician to differentiate between random misses and glaucomatous ones.
  3. The ability to manually re-test a missed location.
    A unique characteristic of the Henson screening tests. It is not unusual for a patient who has never had a visual field test before to miss some stimuli. To get high specificity the perimetrist must be able to confirm misses are a true defect and not just a false positive. The best way to do this is to allow the re-testing of certain locations as many times as is considered appropriate.
  4. Testing around any missed locations with additional stimuli.
    The stimuli on the Henson perimeters are arranged on a 3 degree square matrix within the central 30 degrees. This allows detailed verification and mapping of any central field defect and further aids differentiation between false positive responses and glaucomatous defects.

Speed with the Henson 7000

High speed  

The 26 point screening program can be conducted in less than 1 minute per eye.

In ~80% of cases a ‘normal’ will see all of the stimuli and the test will end. In ~20% of cases some additional testing will be needed to establish whether missing one or more stimuli was a false positive (a normal but unreliable patient) or a true positive (a case of glaucoma). The time taken for the additional testing will vary. For a false positive it might take another minute for a case of glaucoma it could take longer.

To make things even faster, the Henson perimeters have an option that allows the presentation of multiple stimuli, rather than single stimulus – an option unique to the Henson range.

With multiple stimulus presentations, a pattern of 2, 3 or 4 stimuli is presented at the same time and the patient reports the number that they see. Besides speeding up the test it is also more patient friendly, preventing patients from getting flustered and leading to more accurate results with less false positives.

In summary

Screening features
Benefits
Multiple and single stimulus presentation options Choice, but multiple is faster and more patient friendly with fewer false positives
Manual re-test of any stimulus at any stage of examination) Reduces false positives and increases identification of glaucomatous defects
Manual addition of test locations at any stage of examination Allows further examination of areas around any missed stimuli to confirm defects and establish extent of loss
Extendable screening program (26> 68 points) Gives the option of enhanced, in-test specificity and reduces false positives
Optimised test pattern Enables faster test times without loss of sensitivity

Technical specification

Download in PDF

Test specifications
Visual field test range (degrees) 30
Stimulus duration (ms) 200
Stimulus size Goldmann III
Visual field testing distance (cm) 17
Stimulus intensity (maximum) 317 ASB
Background illumination 10 ASB
Test methods Standard Automated Perimetry (SAP), white-on-white
Screening tests/patterns
Suprathreshold – single stimulus 2 levels (26, 68 points)
Suprathreshold – multiple stimulus 2 levels (26, 68 points)
Esterman (Driving) No (Henson 9000 only)
Customised tests Test locations can be manually added to all suprathreshold tests
Average testing times
Suprathreshold – single stimulus ~90 seconds per eye
Suprathreshold – multiple stimulus <60 seconds per eye
Fixation control  
Fixation target Single or 4-point LED diamond pattern
Video eye monitor No (Henson 9000 only)
Software features
Patient management database MS Windows compatible; networkable
Practice management integration EMR compatibility (parameter passing and text file)
Languages ENG, CHI, key European languages
Connectivity
DICOM Yes (images)
Ethernet Yes, via connected computer
Database backup Removable, network or cloud storage
Dimensions
Weight (kg) 5
Measures (W x D x H / mm) 270-350 x 230 x 300-350 (height adjustable)
Classification
Mains operated Yes
Medical device Class 1
Applied part Type B
Regulatory approvals
CE Yes
FDA Yes
Control device External PC / laptop / tablet running MS Windows® Professional, v. 7, and above
Patient unit inputs/outputs C13 mains input; Patient Response Button; USB Type B connector
Electrical requirements 85 – 263Vac, 50/60Hz, 60VA
Optional printer Any compatible with controlling computer

© Elektron Technology UK Ltd. All rights reserved.
Microsoft® and Windows® are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries.

Which Henson is right for you?

The Henson 7000 is a dedicated glaucoma screener that supports the quick and reliable identification of those who do/don’t have visual field defects. Its flexible and customisable 26 and 68 point screening tests are perfectly suited to delivering high specificity and ruling out false positives with confidence.

The Henson 9000 performs the same function as the 7000, but extends to a 136 point screening test for enhanced specificity, whilst also offering threshold testing in support of the ongoing monitoring and management of patients with established visual field loss.

Whilst the Henson 7000 might be most suitable in a primary care setting, the Henson 9000 has application across primary, secondary and tertiary care environments.

A technical comparison of the two machines is available in the table below.

Comparison: Henson 7000 vs. 9000

Henson 7000 glacuoma screener

Henson 7000

Henson 9000 glaucoma monitoring

Henson 9000

Test specifications
Visual field test range 30° 60° (monocular)
160° (binocular)
Visual field testing distance 17 cm 25 cm
Stimulus intensity (maximum) 317 ASB 10,000 ASB
Background illumination 10 ASB 31.5 ASB
Stimulus duration 200 ms
Stimulus size Goldmann III
Test methods  Standard Automated Perimetry (SAP), white-on-white
Screening tests/patterns
Suprathreshold – single stimulus 2 levels (26, 68 points) 3 levels (26, 68, 136 points)
Suprathreshold – multiple stimulus 2 levels (26, 68 points) 3 levels (26, 68, 136 points)
Esterman (Driving) No Groups 1 and 2 (EU standard)
Customised tests Test locations can be manually added to all suprathreshold tests
Threshold tests/patterns
Zata Standard threshold central No 10-2; 30/24-2 (extendable in-test)
Zata Fast threshold central No 10-2; 30/24-2 (extendable in-test)
Average testing times
Suprathreshold – single stimulus ~90 seconds per eye
Suprathreshold – multiple stimulus <60 seconds per eye
ZATA N/A ~4 minutes per eye
Fixation control
Fixation target Single or 4-point LED diamond pattern
Heijl-Krakau N/A Yes
Video eye monitor No Yes
Software features
Patient management database MS Windows compatible; networkable
Practice management integration EMR compatibility (parameter passing and text file)
Languages ENG, CHI, key European languages
Hemifield Analysis N/A Yes
Progression Analysis N/A Yes
HFA data import N/A Yes
Connectivity
DICOM Yes (images)
Ethernet Yes, via connected computer
Database backup Removable, network or cloud storage
Dimensions
Weight (kg) 5 13.5
Measures (mm) 270-350 x 230 x 300-350 440 x 400 x 452
Classification
Mains operated Yes
Medical device Class 1
Applied part Type B
Regulatory approvals
CE Yes
FDA Yes
Control device External PC / laptop / tablet running MS Windows® Professional, v. 7, and above
Patient unit inputs/outputs C13 mains input; Patient Response Button; 1 x USB Type B connector C13 mains input; Patient Response Button; 2 x USB Type B connector
Electrical requirements 85 – 263V AC, 50/60Hz, 60VA
Optional printer Any compatible with controlling computer

© Elektron Technology UK Ltd. All rights reserved.
Microsoft® and Windows® are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries.

Henson 7000 video library

Screening with Henson perimeters

Professor David Henson explains how screening works on Henson perimeters.

Video length: 11:25

Henson screening test patterns

Professor Henson explains the two test patterns available on the Henson 7000. (Please note, the Henson 8000 to which he refers has now been superseded by the 9000.)

Video length: 0:54 secs

Multiple stimulus tests and their benefits

Professor David Henson explains the rationale for the faster, more precise and “patient-friendly” multiple stimuli test and how this differs from single stimulus testing.

Video length: 5:40

The Hensons and practice management integration

Professor David Henson explains that the Henson software has a patient database that can be easily incorporated in practice management systems.

Video length: 3:33

Frequently asked questions

Which is more important sensitivity of specificity?

  • 100% sensitivity = every screening test would capture those with a visual field defect, i.e. result = fail
  • 100% specificity = every screening test would not fail those with a healthy visual field, i.e. result = pass

Ideally, a screening test would be 100% sensitive and 100% specific, but in reality there will always be anomalies – i.e. ‘false negatives’ (those with the condition who pass the test) and ‘false positives’ (those without the condition who fail the test).

The sensitivity/specificity of a visual field screening test can be altered by changing the fail criteria, e.g. if the fail criteria of a supra-threshold visual field test were to be changed from a single missed point to a cluster of three missed points, then the sensitivity would go down and the specificity would go up.

So, which is the more important? To answer this question you have to answer another. What are the relative costs of a false positive and false negative? When screening for glaucoma in an unselected population, where the prevalence of the disease is low (<2%), it is generally accepted that the specificity should be ≥95%. If it falls much below this figure then we end up failing a relatively large number of people that do not have the disease. If the study population is a high risk one (higher percentage of true cases) then the sensitivity should be increased at the cost of lowered specificity.

Is the Henson 7000 purely a screening unit?

Yes.

The 7000 is a small, portable and durable screener for practice and domiciliary use. Specifically designed to aid quick and easy screening of patients, it will enable screening programmes to confidently identify those who do have visual field defects and efficiently rule out those who don’t.

For the detailed screening and ongoing management of patients with established visual field loss, the Henson 9000 with its ZATA threshold algorithm would be more appropriate.

What test patterns does the Henson 7000 have?

Two.

The supra-threshold tests have a 26 point central field test, extendable to 68 points.

Test extension can be done at any time during the test or set in the options to automatically extend, should the patient miss any of the points presented. The second option is better for patients as they will perceive no interruption during the test.

How does the Henson 7000 differ from the Henson 9000?

Essentially, it comes down to screening vs. enhanced screening and monitoring.

The Henson 7000 is a dedicated glaucoma screener that supports the quick and reliable identification of those who do/don’t have visual field defects. Its 26 and 68 point screening tests are perfectly suited to this purpose.

The Henson 9000 performs the same function as the 7000, but extends to a 136 point screening test for enhanced sensitivity, and also offers threshold testing in support of the ongoing monitoring and management of patients with established visual field loss.

A technical comparison of the two machines is available in the table below.

Henson 7000/9000 Technical Specification

PDF

Henson 7000 glacuoma screener

Henson 7000

Henson 9000 glaucoma monitoring

Henson 9000

Test specifications
Visual field test range 30° 60° (monocular)
160° (binocular)
Visual field testing distance 17 cm 25 cm
Stimulus intensity (maximum) 317 ASB 10,000 ASB
Background illumination 10 ASB 31.5 ASB
Stimulus duration 200 ms
Stimulus size Goldmann III
Test methods  Standard Automated Perimetry (SAP), white-on-white
Screening tests/patterns
Suprathreshold – single stimulus 2 levels (26, 68 points) 3 levels (26, 68, 136 points)
Suprathreshold – multiple stimulus 2 levels (26, 68 points) 3 levels (26, 68, 136 points)
Esterman (Driving) No Groups 1 and 2 (EU standard)
Customised tests Test locations can be manually added to all suprathreshold tests
Threshold tests/patterns
Zata Standard threshold central No 10-2; 30/24-2 (extendable in-test)
Zata Fast threshold central No 10-2; 30/24-2 (extendable in-test)
Average testing times
Suprathreshold – single stimulus ~90 seconds per eye
Suprathreshold – multiple stimulus <60 seconds per eye
ZATA N/A ~4 minutes per eye
Fixation control
Fixation target Single or 4-point LED diamond pattern
Heijl-Krakau N/A Yes
Video eye monitor No Yes
Software features
Patient management database MS Windows compatible; networkable
Practice management integration EMR compatibility (parameter passing and text file)
Languages ENG, CHI, key European languages
Hemifield Analysis N/A Yes
Progression Analysis N/A Yes
HFA data import N/A Yes
Connectivity
DICOM Yes (images)
Ethernet Yes, via connected computer
Database backup Removable, network or cloud storage
Dimensions
Weight (kg) 5 13.5
Measures (mm) 270-350 x 230 x 300-350 440 x 400 x 452
Classification
Mains operated Yes
Medical device Class 1
Applied part Type B
Regulatory approvals
CE Yes
FDA Yes
Control device External PC / laptop / tablet running MS Windows® Professional, v. 7, and above
Patient unit inputs/outputs C13 mains input; Patient Response Button; 1 x USB Type B connector C13 mains input; Patient Response Button; 2 x USB Type B connector
Electrical requirements 85 – 263V AC, 50/60Hz, 60VA
Optional printer Any compatible with controlling computer

Can the Henson 7000 be operated from any laptop/PC?

Yes, it can be operated from any PC running the MS Windows™ Professional operating system (version 7, or above).

The control device must also have one spare USB port for interfacing with the Henson 7000.

Is the software easy to install?

Yes. The software is supplied on a USB memory stick and is a single file installer. Simply click on it and it will install all parts of the software.

Both Henson machines are supplied with a quick start guide that takes you through the whole process step-by-step.

Can I use any printer with the Henson software?

Yes.

The Henson software prints the test result to the default installed printer on the laptop/computer being used as the control device. Printing is done via the default installed PDF viewer (Adobe Reader in the case of Henson 8000). Essentially, as long as the installed printer is Windows-compatible it will work without a problem.