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Twinfield® 2

Perimeter

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Twinfield® 2

The OCULUS Twinfield® 2 provides you with the very best of our more than 50 years of experience in the perimetry area. This device measures the full field of vision using both automatic, static perimetry and automatic or manual kinetic examinations. The Twinfield® 2 received the express recommendation of the German Ophthalmology Society (DOG) for expert assessment perimetry.

OCULUS Twinfield® 2 - Vollfeld-Projektionsperimeter

Functions

The Examination Programs

The pre-defined test programs of the Twinfield® 2 perimeter have been set up in such a way that you can easily perform the examinations that you require most often. Whether glaucoma, age-related macular degeneration, neurological diseases – appropriate examinations are available for them all. Furthermore, the modular setup of these programs enable you to create custom test processes, as all available test point grids can be conveniently combined with all OCULUS test strategies. You can thus extend the comprehensive standard program series to meet your own particular requirements.

The OCULUS Test Strategies

To gain as much information in the shortest possible time – this principle has always been heeded in the development of all OCULUS test strategies. The SPARK Strategy incorporates data from more than 90 000 diagnoses in a matter of minutes to give precise and stable measurements, especially in Glaucoma detection, diagnosis and progression analysis. The OCULUS Fast Threshold achieves a similar performance with clever improvements to the classic 4-2 step method. And since exact numeric values of the perception threshold do not, in many cases, show any priority, the multiple suprathreshold strategies available in the Twinfield® 2 perimeters offers a faster and more comfortable alternative.

The OCULUS Test Point Grid

Optimally selected examination areas significantly contribute to meaningful visual field findings. The Twinfield® 2 perimeter provides comprehensive, pre-defined test point grids, which cover all areas ranging from the macula area to the entire field of vision. Grids with a higher density of test points in the center, which take account of the physiology of the retina, are the trademark of the Twinfield® 2. Grids with uniform, orthogonally distributed test points along with other grids, such as the Esterman grid, complete the list of available examination areas.

Results Printout

The measuring results of the Twinfield® 2 perimeter are summarized in the standardized results printout. For threshold-determining examinations, all clinically relevant data are recorded and are shown in various different depictions whereas for suprathreshold tests, only a single informational overview is printed.

Static Perimetry

The Twinfield® 2 performs fast and versatile automatic static examinations to measure the central field of vision with a high degree of accuracy. In the macular area, the precision is increased even more by a considerable densification of the test points, and the periphery can be tested using a suitable test grid. The modular setup of the examination programs guarantees that the Twinfield® 2 perimeter can be adapted to meet all clinical research and daily practice requirements.

Improved Diagnostic Reliability

Additional processes improve the diagnostic reliability of perimetric examinations conducted with the Twinfield® 2 perimeter. Re-examination of areas of concern independent of the test point grid and remote observation of the patient’s eye increase the reliability of the findings; the expert system Glaucoma Staging Program (GSP) provides valuable support in the analysis of the findings.

Kinetic Perimetry

Exact adherence to the Goldmann Standard allows the Twinfield® 2 to be used for assessment perimetry purposes. Automation of the kinetic examinations increases the reproducibility of the test. Fast and comprehensive testing of the entire field of vision testing is achieved by linking the fully automatic kinetic tests with static testing methods.

Perimetry-Software

SPARK threshold strategy
Glaucoma Staging Program (GSP)
Threshold Noiseless Trend (TNT) Progression Analysis
The SPARK examination strategy was primarily developed for glaucoma patients and is available for all OCULUS perimeters. It is based on data from more than 90 000 perimetric findings and allows a very fast, yet very precise measurement of thresholds in the central visual field. The modular structure of the method makes it suitable for a variety of applications:

  • SPARK Precision (optional software) is the full version of SPARK. The complete visual field examination of glaucoma patients takes only 3 minutes per eye. The greater stability of the results allows for more sensitive progression analysis.
  • SPARK Quick is used for follow-up or screening examinations. The test takes just 90 seconds per eye.
  • SPARK Training is ideal for patient training. The 40 second measurement can also be used as a screening examination.

The Glaucoma Staging Program (GSP) is based on pattern recognition and is dedicated to early detection of glaucoma.

The GSP software places examination findings into visual field classes (normal, glaucomatous, artifactual and neuro) based solely on their appearance. In addition, risk classes (normal, suspect, pre-perimetric, early stage, moderate and severe) are also assigned to findings that are classified as normal or glaucomatous. The evaluation results are presented in intuitive green-yellow-red color coding.

The striking novelty of the GSP is its ability to detect subtle changes in the visual field associated with early stage glaucoma. Findings of suspect and pre-perimetric risk classes may contain reductions in the visual field that cannot be readily seen by the examiner. They usually remain undetected also by standard perimetric indices.

The Glaucoma Likelihood Index (GLI) summarizes the results of the GSP classification into a single parameter presenting a value between 0 (normal) and 5 (severe glaucoma).

The Glaucoma Staging Program (GSP) is available for OCULUS Twinfield® 2, Centerfield® 2 and Easyfield® perimeters. This upgrade is available for the existing units.

TNT provides a quantitative, statistical analysis of the visual field examinations conducted over time. For follow-up purposes the software uses all visual field results taken over the entire observation period and takes the patient's threshold values into account obtained on the 30-2, 30x24 or 24-2 patterns. TNT uses a specific filter to reduce the fluctuation range of the threshold values and to perform a consistent trend analysis. In conjunction with the fast SPARK strategy, the sensitivity of detecting progression in early stage glaucoma is greatly improved.

  • TNT creates a concise progression analysis report containing the most important parameters (MD increase, p-values, etc.).
  • TNT can differentiate between diffuse and focal progression based on the focality index (FI) value.
  • TNT applies multiple statistical criteria to establish possible progression.
  • TNT displays the prognosis of the expected visual field for a patient age-group selected by the examiner.

Device
SPARK threshold strategy Glaucoma Staging Program (GSP) Threshold Noiseless Trend (TNT) Progression Analysis

Title

Description

FAQ

There are four models in the OCULUS perimeter range. All four models can perform screening (supra-threshold) and threshold perimetry. Apart from being various sizes they differ as follows:

Model Easyfield® Smartfield Centerfield® Twinfield®
Maximum Eccentricity 30° 30°/25°
With fixation shift: 60°/50°		 36°
With fixation shift: 70°		 90°
Goldmann stimulus size III III III I, III & V
Static/Kinetic Static Static Static/Kinetic Static/Kinetic
Color perimetry White-white White-white White-white
Blue-yellow		 White-white
Blue-yellow
Red-white
Stimulus presentation Light emitting diodes (LED) LCD display Back surface projection Back surface projection

All commercially available perimeters make use of the same basic testing principles. What makes one perimeter different to another is the way it performs fast thresholding test. Various fast threshold strategies are included in the OCULUS perimeters, one of which is the SPARK strategy – currently the fastest OCULUS strategy for glaucoma patients. It is the product of many years of research dedicated to obtaining reliable averaged results within the shortest possible time.

Furthermore all the perimeters include a unique glaucoma staging display called the Glaucoma Staging Program (GSP).

Lastly glaucoma progression is monitored by the Threshold Noiseless Trend (TNT) analysis method. The method can distinguish between diffuse or focal progression, and unlike methods based on event analysis, trend analyses make full use of the data pool of earlier examinations.

Yes, it may differ somewhat in appearance, but all the essential data known from other perimeters is available on the OCULUS perimeter printouts.

  • Full Threshold (4-2 dB Staircase) Strategy – the algorithm of this strategy can easily be implemented in any instrument and therefore it is available on most commercial perimeters. Results obtained with this strategy can be compared to results from any other perimeter using the same strategy.
  • OCULUS Fast Threshold Strategy – this strategy aims to reduce test time of the 4-2 dB Staircase strategy. The idea of the OCULUS Fast Threshold Strategy is to achieve a compensating gain in information by starting the measurement at each test point with a luminance value equal to the expected sensitivity value at that point. This expected value is calculated on the basis of measurement results already obtained at neighbouring test points.
  • CLIP (Continuous Light Increment Perimetry) Strategy – locations are tested individually by increasing the luminance of the stimulus continuously until the patient responds.
  • SPARK – the examination is performed in four phases. Each of these phases supplies a possible estimation of the functioning of the entire visual field, and the final result is obtained by averaging of the values obtained during each phase.

Yes. SPARK Precision is performed in four phases over a time period of three minutes. Each of the 66 points in the test pattern will be tested at least once during the three minutes.

Shorter examination time and better repeatability are the main benefits of SPARK. Testing time for this strategy will not exceed three minutes and this holds true even for patients with severely impaired visual field function. Compared to other known strategies, SPARK results have a much lower variability.

Various quick screening methods are available. Normally supra-threshold tests are used, however SPARK Quick has been designed specifically with screening in mind. The duration of the test is 1.5 minutes (90 seconds) on all patients and threshold values are generated after the examination.

Most perimeters only have Heijl-Krakau method to monitor patient fixation. This method uses the blind spot as reference. Glaucoma can cause absolute defects in the vicinity of the blind spot, which may increase as the disease progresses. Using the Heijl-Krakau method for these patients may be problematic. Central fixation control – only available in the OCULUS perimeters – uses the central luminance threshold as reference. This is a helpful method to control fixation for glaucoma patients.

All OCULUS perimeters allow for manual set-up of programs. When comparing current results from an OCULUS perimeter with previous results from other perimeters it is important to adapt the parameters of the current examination as closely as possible to those of the earlier examinations. This needs to be done in order to achieve the highest degree of comparability.

Examinations on the Easyfield®, Smartfield or Centerfield® can be performed in a normally lit room, provided the lighting is diffuse and there are no powerful light sources in the patient’s back. The Twinfield® requires a darkroom, as its perimetric hemisphere must be free of shadows.

GSP uses pattern recognition algorithms in order to assess the visual field results of the patient. For “Normal” and “Glaucomatous” visual fields a risk class can be determined by comparing the detected patterns to the visual field patterns stored in the database of the GSP. If the “Pre-perimetric” risk class dominates the bar chart, it means that the pattern of the measured visual field is similar predominantly to the patterns of patients with pre-perimetric glaucoma from the database. Pre-perimetric glaucoma is defined through glaucomatous changes to the optic nerve head and/or the retinal nerve fibre layer without detectable visual field losses. A “Pre-perimetric” result should be followed by a closer monitoring of the patient.

The software automatically chooses exams done with the same test pattern and the same strategy making comparison fast and easy to detect progression. Exams showing obvious learning effects are excluded by the software. The operator can also manually exclude exams if needed.

Technical Data

Static Perimetry

Programs Pre-defined glaucoma, macula, neurological and screening tests;
Static-kinetic screening; user-defined tests
Strategies Threshold strategies: OCULUS Fast Threshold, Full Threshold, CLIP
Optional: SPARK strategy
Age-adapted supra-threshold screening
(2-zone, 3-zone, quantify defect, OCULUS Class strategy)
Test patterns Rectangular patterns (30-2, 30-2 bs, 24-2, 24-2 bs, 10-2),
Physiological patterns (Area 1-8), Quick Screening, Esterman, customized patterns
Stimulus sizes Goldmann I, III, V
Stimulus color White / Blue / Red
Stimulus luminance range / steps 0 – 318 cd/m² (0 – 1 000 asb) / 0.1 log units
Background luminance 10 cd/m² (31.4 asb)
Background color White / Yellow
Stimulus duration 200 ms / User-defined
Examination speed Adaptive / Slow / Normal / Fast / User-defined
Maximum eccentricity 90° (full field)
Fixation control Video camera image, through central threshold, Heijl-Krakau (using the blind spot)
Patient positioning Motorised double chinrest, height- and depth-adjustable headrest, ergonomic armrest
Reports Glaucoma Staging Program (GSP)
Threshold Noiseless Trend (TNT) progression report
Kinetic Perimetry

Strategies Automatic isopters measured along meridians with freely selectable density
Manual: stimulus freely movable with the computer mouse
Semi-automatic: including scotoma boundary mapping
Stimulus speed 2°/s (Goldmann), user-defined
Features

Bowl radius r = 11.8 in
Dimensions (W x D x H) 31.1 x 28.5 x 33.5 in
Weight 88.1 lbs – without table
Voltage 90 – 264 V AC
Frequency 50 – 60 Hz
Minimal computer requirements Operating system: Windows® XP or higher
Interface USB

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