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

62 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

ESTABLISHING PATTERN DEVIATION PROBABILITY PLOT FROM TDNP

TOTAL DEVIATION NUMERICAL PLOT

STAT PAC eliminates or diminishes the general depression of the measured field and thus the focal loss remains clearly visible or enhanced and plots as

PATTERN DEVIATION NUMERICAL PLOT

These threshold deviation values will be analyzed and its probability of the abnormality in normal population will be plotted as

PATTERN DEVIATION PROBABILITY PLOT

A symbol (in the probability plots) is assigned to each deviation value indicating the probability of finding such deviation value in the normal population. The darker the symbol the greater the probability of abnormality as indicated by P value.

ESTABLISHING GLOBAL INDICES FROM TDNP

TOTAL DEVIATION NUMERICAL PLOT

GLOBAL INDICES

1.Mean deviation index in dB value and with its P value.

2.Pattern standard deviation (PSD) in dB value and with its P value,

3.Corrected pattern standard deviation (CPSD) in dB value and with its P value.

4.Short term fluctuation (SF) in dB value.

GLAUCOMA HEMIFIELD TEST (G.H.T) FROM PATTERN DEVIATION NUMERICAL PLOT

a.GHT out side normal limits

b.GHT border line

c.GHT abnormally low sensitive

d.Abnormally high sensitivity

e.Within normal limits.

64 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

SINGLE FIELD ANALYSIS PRINTOUT WITH

FULL THRESHOLD STRATEGY

66 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

FEATURES OF SITA STANDARD AND

SITA FAST TESTING STRATEGIES

The Humphrey system has developed two separate strategies with two separate goals.

1.SITA-Standard: The goal was to design a perimetric thresholding method which collects twice as much information per unit time as Humphrey Full Threshold standard algorithm. SITA Standard cuts the test time in half without compromising test reproducibility relative to the current international standard.

2.SITA-Fast: The goal was to design a thresholding method which collects twice as much information per unit time as FASTPAC. SITA-Fast cuts the test time in half relative to FASTPAC, without compromising test reproducibility.

Both SITA-Standard and SITA-Fast are designed to run with these threshold tests: Central 10-2

Central 24-2

Central 30-2 Peripheral 60-4

All SITA tests must use a White, Size III stimulus. Any time a SITA strategy is used, these two parameters will be automatically set by your HFA II.

Please note that macular program test pattern, nasal step and any test conducted with stimulus size V cannot be tested by SITA.

The single field ananlysis printout with SITAStandard strategy and SITAFast strategy, we have common following features:

1.Reliability indices expressed in percentages except in case of fixation losses which is expressed in fractions.

Reliability indices.

Fixation losses (1/20)

False positive response rate (1%) False negative response rate (0%)

2.Does not calculate short-term fluctuations. (SF)

3.Does not calculate corrected pattern standard deviations. (CPSD)

Glaucoma hemifield test (GHT) is present with both SITA strategies.

Please note that these testing strategies are threshold testing strategies and hence they are used in threshold tests. Testing strategies used in screening tests are different. They are supra threshold testing strategies and they are discussed in Chapter 8.

68 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

SINGLE FIELD ANALYSIS PRINTOUT WITH

SITA FAST STRATEGY

.

FIGURE 3.30

1.Reliability indices expressed in percentage.

2.Do es not calculate short-term fluctuation. (SF)

3.Does not calculate corrected pattern standard deviation. (CPSD)

4.G.H.T. analysis present.

70 A VISUAL FIELD EVALUATION WITH AUTOMATED DEVICES

HUMPHREY VISUAL FIELD TEST PRINTOUTS

WITHOUT STATPAC ANALYSIS

When there is no normative data available, for comparing the measured retinal sensitivity the STATPAC cannot analyse the measured retinal sensitivity. The normative data is not available for the following tests.

1.Any test that is done with test pattern macular test, nasal test, peripheral test

2.Any test that is done with stimulus size V

3.Any test that is done with custom tests

So the format of above test parameters will not contain total deviation plots, pattern deviation plots, global indices and G.H.T analysis.

If we select the threshold test parameters that do not meet the criteria for STATPAC analysis their results will be printed in different formats as shown below.

1.Three-in-one printout

2.Two-in-one printout—Nasal step threshold test

3.Three-in-one printout—Macula threshold test

4.Peripheral tests

The STATPAC (The Humphrey Field Analyser’s statistical package) will analyse tests that fall within the parameters listed below.

The most important point to be remembered is that there are no normal values available to STATPAC for the tests conducted with size V stimulus, for custom tests and any test done with point patterns - nasal tests, macular tests, or peripheral tests. So the field analyzer determines the central reference value which helps to calculate the expected threshold value. The central reference value is a hypothetical threshold sensitivity at the centre of the field ignoring the foveal peak. It may be a value projected on the basis of normal slope of hill of vision and emperically determine threshold at four or five locations or assigned value (by age or as a minimal value). It is used to determine the expected threshold values to calculate defect depth.