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

FOLLOW-UP VISUAL FIELD EXAMINATION 161

GLAUCOMA CHANGE PROBABILITY—BASELINE PRINTOUT

The components of the glaucoma change probability analysis baseline printout:

iv.Test data:

GHT analysis outside normal limits

v.MD slope—not significant.

FOLLOW-UP VISUAL FIELD EXAMINATION 163

GLAUCOMA PROGRESSION ANALYSIS (G.P.A)

To analyze glaucoma progression, Humphrey introduced a new software—glaucoma progression analysis (GPA). It is introduced to overcome the drawback of glaucoma change probability analysis. The main drawback of glaucoma change probability analysis is that the comparisons are made between the raw data ( TDNP) of the baseline and the follow-up tests. As the raw data ( TDNP) is affected by both transient and progressive generalized changes (e.g. those caused by learning effects, long-term fluctuation or media changes), we do not know whether the changes are either due to disease progression or due to long-term fluctuation. The SITA strategies do not have glaucoma change probability analysis option. In order to avoid these drawbacks, the glaucoma progression analysis (GPA) is introduced by Humphrey. In GPA, the comparisons are made between the baseline pattern deviation numerical plot and the pattern deviation numerical plot of the follow-up test. The SITA strategies have the GPA option. GPA uses SITA and pattern deviation to identify glaucoma-specific progression.

Step 1 : ESTABLISHING THE BASELINE DATA (PATTERN DEVIATION NUMERICAL PLOT)

The first step in glaucoma progression analysis is the establishment of baseline data (pattern deviation numerical plot). If the patient undergoes the field test for three or more times, the field analyzer generates the baseline printout depending on the data of the first 2 tests.

Step 2: ESTABLISHING THE DECIBEL DEVIATION PLOT IN FOLLOW-UP TEST PRINTOUT

Now the follow-up test result (pattern deviation numerical plot) is compared to the baseline pattern deviation numerical plot and calculates the difference between the baseline and the follow-up test pattern deviation numerical plots and plots the difference as deviation from the baseline plot in the follow-up test printout.

Step 3: ESTABLISHING THE PROGRESSION ANALYSIS PLOT IN FOLLOW-UP TEST PRINTOUT

Now each deviation from the baseline is compared to inter-test variability typical of stable glaucoma patient and then shows point locations in progression analysis plot which have changed significantly. The progression analysis consists of four symbols.

Symbols:

Î= Progression at 95% significance level

Î= Progressing point repeated in 2 consecutive exams

•= Progressing point repeated in three consecutive exams X = Progressing point repeated in three consecutive exams.

The criteria for identifying progression in visual fields:

•Minimum of three tests required: 2 baseline and 1 follow-up exam

•Each follow-up compared to average thresholds of 2 baseline exams

•Additional follow-up compared both to baseline and 2 most recent follow-ups.

GPA alert TM: Three Î in one exam denotes “possible progression” and three • indicates likely progression.

FOLLOW-UP VISUAL FIELD EXAMINATION 165

GLAUCOMA PROGRESSION ANALYSIS FOLLOW-UP PRINTOUT

The components of the GPA follow-up printout:

ii.Selection of the test: 24-2 SITA-Standard.

iii.Gray scale, pattern deviation probability plot, deviation from baseline plot, progression analysis plot.

iv.Reliability indices - FL, FN, FP.

v.Mean deviation

vi.PSD

vii.GHT analysis

viii.Plain language interpretation of analysis “Possible Progression” or “Likely Progression”.

FOLLOW-UP VISUAL FIELD EXAMINATION 167

SINGLE FIELD ANALYSIS WITH GPA RESULTS

•The new look in the standard of care!

•Once GPA is set up for a patient, progression is automatically identified at each visit.

•Original single field analysis will be printed if GPA has not been set up.

Custom7Tests

The custom test is an important feature of many automated static field analyzers. This is one area which was neglected by many ophthalmologists. Many ophthalmologists are not using the custom test option given by standard field analyzers. The custom test allows the opthalmologists to focus in an area where the first test indicated defects. Especially for the follow-up tests, we can design a custom point pattern where we want to concentrate more. In 30-2 and 24-2, we know the distance between the point to point is 6°. During the follow-up tests the field defect has to progress for distance of 6° to affect the next point. Till then, it does not show any progression in field defect. We can design custom point pattern depending upon the first field. We can create points seperated by 1° in an area where we are expecting the progress of the disease; but unfortunately, many opthalmologists are not using custom tests. We can even create our own point pattern and we can save the point pattern and we can use the point pattern whenever we want and the results can be saved and can be printed. The printout format of the custom test will be without STATPAC analysis, because there is no normative data available to the custom tests. The SITA-Standard and SITA-Fast strategies are not available for custom tests. Only full threshold and FASTPAC are available for custom tests.

I created a custom threshold test pattern with the following features:

1.Central 30° area was selected.

2.Points were created on either side of horizantal and vertical meridian and distance between point and the meridian being 1°.

3.Within 5° around fixation points were created with 2° resolution (nearly 36 points within 5° area around fixation point)

4.In the area between 5° and 15° points were created with 4° resolution.

5.In the area between 15° and 30° points were created with 6° resolution.

6.This point pattern can be used to know the field status of glaucoma patient, irrespective of the stage of glaucomatous optic nerve damage.