A perimetry test (also called visual field test, peripheral vision test, or visual field assessment) is a non-invasive subjective test to systematically map the central and/or peripheral vision to assess visual function. It measures light sensitivity in different regions of the visual field to identify either localized or generalized visual dysfunction. Mapping the visual field is essential for diagnosing and monitoring ocular or neurological conditions such as glaucoma, stroke, and tumours. 

During the test, the patient is required to maintain fixation on a central target. They will be asked to respond when they detect the presence of test stimuli of varying intensity on a uniform background. The minimum intensity that can be seen defines the sensitivity to light. 

In static perimetry, short flashes of light of varying intensity are presented in a predetermined pattern of test locations. Static perimetry is currently the most commonly used type of perimetry and can detect small changes in sensitivity, making it well suited for glaucoma care and testing the central visual field.

In kinetic perimetry, test stimuli of varying intensity and size move from non-seeing to seeing regions. The stimulus’s trajectory is defined by the examiner and can be adapted as the testing progresses. The patient responds when they detect the stimulus and neighbouring responses to one stimulus type are connected to form an isopter, which represents the boundary of equal sensitivity. Kinetic testing is ideal for rapid testing of the peripheral field and is a highly dynamic test.

The test will be performed in a dimmed room. Clear instructions will be provided on what to expect during testing. Testing will be performed either with unaided or distance spectacles on, or with a trial lens. The non testing eye will be patched if the monocular visual field is being tested. The test duration will depend on the test type and whether repeating is required. A typical static glaucoma test takes between two to four minutes per eye. Blinking during testing is recommended and take a rest if you feel fatigue.

Perimetry can identify ocular and/or neurological conditions such as glaucoma, stroke, and tumours. Visual field testing is interpreted alongside the results of other diagnostic tests. Visual field loss occurring in a location corresponding to the area of structural damage may confirm a diagnosis.

The Visual Field Digest to perimetry is available to view here.

Haag-Streit Academy offers bespoke product training, delivered at your place of work and tailored to fit your specific needs. Click here for more information. 

Haag-Streit Academy also offers a free perimetry e-learning course which is accessible via the Haag-Streit Academy elearning portal. To access the course, visit https://hs-uk.co/LearningPortal.

No, we can easily transfer Humphrey data and conduct follow up examinations. Contact us for further information at octopus@haag-streit-uk.com.

There are many similarities between the Manual Goldmann and the Octopus perimeter. Professor Fiona Rowe has done studies which show a comparison of the accuracy, which are available at https://pubmed.ncbi.nlm.nih.gov/24587983/.

The Octopus perimeter has a comprehensive range of tests available. It is programmable for static and kinetic testing over 180°, within 0.1°, using threshold or supra-threshold techniques.

Testing should be performed in a distraction-free environment that is dimly-lit. The Octopus cupola should be kept clean and free of dust. The Octopus 900 needs to be calibrated every time it is turned on. Calibration should take place in the same lighting conditions as those used during testing.

Enter the patient details into EyeSuite ensuring the date of birth is entered correctly. The patient’s distance refraction and age are used to calculate the required trial lens. Full aperture trial lens should be used and be put into the trial lens holder prior to seating the patient. The sphere power lens(es) should be placed closer to the patient’s eye, and the cylinder lens should be oriented in the correct axis if used.

Instruct the patient carefully. This includes why the test is done, what the patient is expected to do, the importance of maintaining fixation, that not all stimuli will be visible and that the test can be paused if they experience fatigue. Ensure the patient is comfortably seated with a straight-upright posture to reduce strain. The non-tested eye needs to be patched if monocular testing is being performed.

Correctly position the patient on the device so the eye being tested is centred. The eye should be close to the trial lens but not too close that it prevents normal blinking or causes smudges on the lens. Select the appropriate fixation target: the standard cross mark, central point of ring target. Adjust the level of fixation control depending on the patient’s ability to maintain steady fixation to make testing possible.

During the test, ensure you monitor the test and offer encouragements. Excessive false positives and false negatives may identify ‘trigger-happy’ patients or inattentive patients respectively. If the results seem compromised, it is recommended to start a new test and discard the compromised one. It is important to note, however, that patients with impaired vision often do not respond due to their condition and not because they answer unreliably. Note down any difficulties conducting the test that may impact the reliability of results.

The Octopus offers several visual field representations and indices to aid the interpretation of the static visual field results.  

Values representations present the raw data of sensitivities. Grayscale of Values displays the raw data in a colour map where dark shading represents lower sensitivity. These representations do not take into account that sensitivities vary with age and eccentricity of test location therefore have limited diagnostic value.

Comparisons representation shows the relative loss in sensitivity at each point compared to the age normative values. Deviations from normal are shown for each test location. Plus symbols represent points where sensitivity is within normal ranges. A shaded square represents sensitivity thresholds of 0 dB.

Corrected comparisons remove the effect of any diffuse defect present within the comparisons representation to highlight areas of local sensitivity loss.

Probability representations can be used to distinguish between normal and abnormal visual field locations. They show the probability that a given sensitivity threshold would be obtained at the respective location for a person of the same age as the patient with a normal visual field. The darker the shading, the smaller the probability that a person with a normal visual field would show this level of sensitivity loss.

Polar and cluster analysis further aid the interpretation of visual field loss in glaucoma. A full description of visual field representations and interpretation can be found in the Chapters 7 and 8 of the Visual Field Digest.

For each stimulus size and intensity, Octopus kinetic perimetry automatically provides the age-matched normal isopter location as a reference. The inner dark central band represents 25–75% of age-matched normals, and the outer light band denotes 5–95% of age-matched healthy normals. These normative bands support quick identification of the deviations from normal.

Assess the shape of the isopters to identify whether there are quadrants of vision loss. Placing static points within the isopter may further identify local scotoma within the seeing area. Assess the size and shape of the blind spot corresponding to the optic nerve head to determine whether there is enlargement of the blind spot.

Assess the reliability of kinetic testing by placing short vectors within the isopter to test for false negatives and beyond the isopter to test for false positives.

The Octopus 900 boasts a 180° hemispheric bowl. Test patterns can be produced with a 0.1° across the field.

EyeSuite can produce several visual field printout options including HFA-style print-outs. These include; Single field, 4-in-1, 7-in-1 and series and trend analysis.

The Octopus 900 can be coded to create a comprehensive range of strategies & patterns, which can be bespoke for the individual user’s needs.

Perimetry charts are available on the Haag-Streit UK e-shop.

Yes, the Octopus 900 is an ideal device for any perimetry-related clinical research, due to the unsurpassed range of testing available.

Yes. The Octopus 900 can produce static binocular Esterman and Goldmann kinetic visual fields to meet the requirements of UK driving standard testing.

The HS-UK Service Division is an authorised service agent for Haag-Streit Octopus perimeters, so can deal with any servicing or maintenance issues. At HS-UK, we only use genuine Haag-Streit approved parts, which ensures your Octopus device complies with Haag-Streit specifications. 

An experienced and fully-trained Field Service Engineer from the HS-UK Service Division will visit your premises to carry out service procedures, such as checking the EyeSuite version and that the system operates without errors, cleaning all optics and mirrors, ensuring the chinrest operates freely and the holder moves in and out of position and ensuring the patient answering switch is operating correctly. Visit our HS-UK Service Division pages to find out more about taking out a service contract.