Centerfield®2

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.

• 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.