Ординатура / Офтальмология / Английские материалы / A Visual Field Evaluation with Automated Devices 2nd edition_Reddy_2006

Screening8 Tests

Till now we talked about central threshold tests with different test strategies to detect glaucoma field defects. Now I will deal in brief with the screening tests used in glaucoma survey projects.

Like the threshold tests (for example, 24-2 SITA-Standard, 24-2 is point pattern component and SITAStandard is test strategy component), the screening tests also have two components, the point pattern component and test strategy component.

The point pattern component of screening tests are divided into 4 major groups. Group I —Glaucoma test point pattern

Group II —Central test point pattern Group III —Full field test point pattern

Group IV —Peripheral field test point pattern.

Again each group has different test point patterns as shown in the following table:

Test Point Patterns of Screening tests

Out of the above 11 test point pattern screening tests, we will talk about glaucoma screening tests. The glaucoma screening tests emphasize points surrounding the horizontal meridian with the largest concentration of points on the nasal side.

172 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

GLAUCOMA SCREENING TEST POINT PATTERNS

ARMALY CENTRAL SCREENING TEST POINT

PATTERN RIGHT EYE

SCREENING TESTS 173

ARMALY FULL FIELD SCREENING TEST POINT

PATTERN RIGHT EYE

NASAL STEP SCREENING TEST POINT PATTERN RIGHT EYE

174 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

SCREENING TEST STRATEGIES

The screening test strategies are suprathreshold strategies. Till now we talked about threshold strategies (Full Threshold, FASTPAC, SITA-Standard and SITA-Fast). For screening tests, suprathreshold tests are used instead of threshold test strategies.

The Humphery field analyzer has four screening test strategies as shown below:

1.Two-zone strategy (threshold-related strategy).

2.Three-zone strategy.

3.Quantify defects screening strategy.

4.Single intensity strategy.

TWO-ZONE STRATEGY

Two zone strategy is the first phase for both the three-zone strategy and quantify defects screening strategy.

1st step of two-zone strategy:

Determination of the patient’s threshold of four paracentral points in each quandrant. It uses these values to calculate a ‘central reference level’.

2nd step of two-zone strategy:

In the screening phase of the test, each point in the selected test pattern is exposed to a stimulus 6 dB brighter than the expected threshold for that point. Points not seen in the first stimulus are retested for second time with the same stimulus intensity. That completes the second phase of the test. If the tested point is seen, it is labeled as open circle ‘O’. If the tested point is not seen even for the second stimulus, it is labeled as black square.

176 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

QUANTIFY DEFECTS SCREENING TEST STRATEGY

It is also a continuation of the two-zone test. The points that are failed to respond upon two presentations of the suprathreshold are now subjected to threshold determination strategies. Each point threshold value is determined and the defect depth will be labeled at each test point. The defect depth is the difference between the expected threshold value based on the constructed patient profile and the measured threshold value.

178 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

SCREENING TEST STRATEGIES

TWO-ZONE

SCREENING STRATEGY

Determination of patient’s threshold of four paracentral points in each quadrant

The selected points are tested twice with the suprathreshold stimulus (6 dB brighter than expected threshold)

 The black square point

(The point not responded even to the 2nd stimulus during the two-zone strategy)

180 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

SCREENING TEST AND THRESHOLD TEST—LEFT EYE

Almost 2/3 of the points are not seen almost, all nasal points are totally involved. Biarcuate pattern field loss is seen.

Advised central threshold test

Selection of the test

Central 24-2 threshold test

Test strategy—Full `hreshold

Reliability good

Probability plots are showing biarcuate scotoma corresponding to the screening test printout results.