Clinical investigations Graefe's Archive [Or Clinical and Expefimenlal

Ophthalmology © Springer-Verlag 1991

Graefe's Arch Clin Exp Ophthaimol (1991) 229:501-504

The learning and fatigue effect in automated perimetry Gianni Marra and Josef Flammer

University Eye Clinic Basel, Mittlere Strasse 91, CH-4056 Basel, Switzerland

Received November 5, 1990 / Accepted March 1, 1991

Abstract. A visual field test was performed on 100 volun- teers to study learning or fatigue effects during one ses- sion. The test was carried out with the help of the Octo- pus p rogram J l , which measures the threshold 12 times at 3 test locations. In the majori ty of cases the sensitivity was quite stable during the session. We noted no differ- ence between trained and untrained subjects or between normal and pathological eyes. However, patients with refractive errors, especially myopes, revealed a larger learning effect than did emmetropes.

Introduction

Perimetry is a psychophysical test procedure in which patients must be able to cooperate by exercising a high degree of concentration. In manual perimetry the experi- ence of the perimetrist has a major influence on the outcome of the examination. Whereas it has been possi- ble to minimize this influence through automation, this psychophysical test continues to rely on the cooperat ion

Offprint requests to: J. Flammer

of the patients. Although the latter may be perfectly willing to cooperate, they may not understand the test properly or may not be able to concentrate for an ex- tended period; some patients get tired during the test.

Even when subjects understand the test properly and try to cooperate optimally, the outcome of a second test is often better than that of the initial one. Such a " learning effect" can often be observed clinically. Al- though the term learning effect is widely used in the literature, we do not know whether the patient really learns or exactly what he is learning. Is a physiological phenomenon of the visual system involved or does a psychological feature of the patients influence their de- cision as to which answer to give, seen or not seen? Although it is well known that the second examination can yield better results than the first one, we again turned our attention to this learning effect. We wanted to know whether a time trend can be observed during a perimetric session lasting a few minutes. Furthermore, we tested the question as to whether factors such as age, among others, have an influence on this trend.

The literature on this topic is not entirely conclusive, being to some extent contradictory (Table 1). Some au- thors, such as Greve [5] and Parrish et al. [11], have

Table 1. Summary of the findings in the literature concerning the learning effect in manual and automated perimetry

Authors Learning effect Perimeter used Subjects

Greve [5] Yes Goldman Glaucomatous Parrish et al. [11] Yes Perimetron Normal Rabineau et al. [12] Yes Octopus Normal Heijl et al. [7] Yes Humphrey Normal Lehmann and Faggioni [9] Yes Octopus Glaucomatous Wild et al. [14] Yes Humphrey Glaucoma suspects Katz and Sommer [8] No Humphrey Healthy Gloor et al. [3] No Octopus Glaucomatous Werner et al. [13] Only for SF Octopus Glaucomatous Gramer et al. [4] Only for SF Octopus Glaucomatous Aulhorn and Harms [1] Only in some cases Tfibinger Normal Marra et al. [10] Only in some cases Perikon Normal Gloor et al. [2] Only in some cases Octopus Glaucomatous

502

found a learning effect. Rabineau et al. [12] achieved better test per formance using patients who had previous- ly been familiarized with au tomated perimetry. Leh- m a n n and Faggiori [9] and Heijl [6] have found a higher mean sensitivity in the second test as compared with the first one, whereas Gramer and co-workers [4] and Werner et al. [13] have noted an influence on only the shor t - term fluctuation. Katz and Sommer [8] and Gloor and colleagues [3] did no t find learning effects. The sub- jects tested by Katz and Sommer had previously under- gone manua l perimetry.

It has also been pointed out that a possible learning effect may differ f rom one pat ient to another . Such an individual difference was observed by Aulhorn and Harms [1] dur ing manua l perimetry on healthy subjects, by Mar ra et al. [10] using au tomated kinetic per imetry in heal thy subjects and by G loo r and co-workers [2] using au tomated static per imetry in g laucomatous pa- tients. The authors claim that attentive subjects who con- centrate very hard on the test m ay present opt imal re- sults f rom the beginning, whereas others improve their differential light sensitivity f rom one session to another . Wild et al. [14] and Heijl and colleagues [7] found an eccentricity dependency, whereby the effect was more p ronounced in the periphery.

The purpose o f the present s tudy was to investigate the quest ion as to whether time trends occur during one session and, if so, to try to determine which factors influ- ence these effects.

Subjects and methods

A total of 100 volunteers between the ages of 13 and 86 years were selected from the outpatient department of the University Eye Clinic, Basel (Table 2). One eye of each subject was chosen at random. All subjects underwent a thorough eye examination, including refraction, visual acuity, applanation tonometry, slit- lamp examination and ophthalmoscopy. The patients were asked

Table 2. Description of the subjects tested

Total number of subjects 100

Diagnosis: Healthy eyes 70 Pathological eyes 30

Sex : Men 47 Women 53

Refraction: Emmetropic 33 Myopic 40 Hyperopic 27

Visual acuity : > 1 69 <1 31

Perimetrie experience : Previous experience 32 No previous experience 68

dB

32

30

28

26

24

22 0

I I I I I I I

2 4 6 8 10 12 14 Phase

Fig. 1. Average light sensitivity at each test location in the different phases. Test location A (El) is paracentral; B ( .) and C (ll) lie in the mid-periphery

whether they had had previous experience with automated or man- ual perimetry.

In all, 70 eyes were normal, 16 had early stages of glaucoma and 14 had cataracts. A total of 69 eyes showed a visual acuity of 20/20 or better and that of the remaining 31 eyes was better than 20/60. Overall 40 eyes were myopic (< - 7 D spherical equiva- lent) and 27 were hyperopic (< + 4 D spherical equivalent). In all 32 subjects had previously undergone automated or manual peri- metry, whereas 68 had not.

The study was carried out with the help of the Octopus 201 automated perimeter system using the J1 program. This program, which was especially designed for research purposes, measures the differential light threshold 12 times at 3 test locations in J2 consecu- tive phases; the 3 test locations can be chosen arbitrarily and are hereafter referred to as A, B and C. For our study we selected the following locations: A = ( - 2 / + 2 ) , B=(+9/+15) and C= ( - 2 0 / - 2 0 ) for the right eye, and A=(+2 /+2 ) , B = ( - 9 / + 1 5 ) and C = ( + 2 0 / - 2 0 ) for the left eye. In each phase, program J1 measured the threshold at the three test locations in a random sequence. The normal Octopus bracketing procedure was applied, and the measuring time was between 5 and 10 rain.

For each phase, the mean sensitivity averaged over the total population was calculated for each test location (Fig. 1). For esti- mations of the time trend of sensitivity during the session, a,regres- sion analysis of the sensitivity with time was calculated'for each eye at each test location. To test the possible influence of various factors, the resulting regression coefficients (Rc) were compared between trained and untrained subjects, men and women and nor- mal and pathological eyes using unpaired t-tests. Correlations be- tween Rc and age, visual acuity, optical correction, short-term fluc- tuation, pupil size and numbers of stimuli were calculated.

Results

The mean sensitivity at three test locations correlated, as expected, with age, visual acuity and pupil size (Table 3), indicating lower sensitivity in elderly persons, in sub- jects showing lower visual acuity and in cases with nar- row pupils. Age, visual acuity and pupil size, however, are no t mutual ly independent. The basic quest ion in- volved the degree o f stability o f the light sensitivity dur- ing the same session, which included 12 threshold deter- minat ions at each test location. Averaged over the total popu la t ion tested, the sensitivity at the three test loca- tions was, much to our surprise, quite stable (Fig. 1). There was only a slight and statistically non-signif icant

Table 3. Correlation between the mean sensitivities at the tested locations with age, visual acuity and pupil size

Mean sensitivity Age Visual Pupil at test location acuity size

A r = -0 .48** r=0 .69"* r = 0 . 2 5 '

B r = -0 .44** r = 0 . 5 3 ' * r = 0 . 2 7 '

C r = - 0 . 5 1 * * r=0 .61"* R = 0 . 3 5 '

* P<0 .01 , ** P<0.0001

increase in sensitivity from the first to the second phase, especially in the mid-periphery.

The time trend was obviously different from one pa- tient to another. We therefore calculated a separate re- gression for each eye and for each test location. The slope of this regression served as a parameter for the time trend during the session. A positive slope indicated improvement, whereas a negative slope implied deterio- ration during the test. Figure 2 illustrates the distribu- tion of the individual slopes. It is evident that the majori- ty of eyes showed no major trend towards either im- provement (learning effect) or deterioration (fatigue ef- fect). This was especially true for test location A, which was chosen close to fixation. There was a slightly greater interindividual variation in test locations B and C, indi- cating a dependency on eccentricity [7, 14].

We then tested the question as to whether the time trends (slopes) for the three test locations correlated with each other. As expected, this correlation was significant. The time trend in test location A correlated with that in location B (r=0.63) as well as with that in location C (r=0.50). Trends in location B also correlated with those in location C (r=0.71). All of these relationships were statistically significant ( P = 0.0001). This means that a patient showing a time trend at one test location is somewhat likely to display a similar trend at another test location as well.

In the next step, the slopes of different groups of patients were compared. We found no difference be- tween men and women or between healthy and diseased eyes. Much to our surprise, patients who had had pre- vious experience with perimetry exhibited on average the same slope shown by inexperienced patients!

We then correlated the time trend (slopes) with age, visual acuity, refractive error, short-term fluctuation and the number of stimulus presentations needed (Table 4).

100

80

80

60

40

20

60"

40

20-

- 2 . 5 - 2 - 1 . 5 - 1 - 0 . 5 0 0.5 1

- 2 . 5 - 2 - 1 . 5 - 1 - 0 . 5 0 0.5 1

503

Testlocation A

1.5 2 2.5 3

Testlocation B

1.5 2 2.5 3

60 " Testlocation C

50

40

30

20- _ ~

10- ~

0- - 2 . 5 - 2 - 1 . 5 - 1 - 0 . 5 0 0.5 1 1.5 2 2.5 3

Fig. 2. Frequency distribution of the time trend (slope of the regres- sion line) at test locations A (V]), B (I~,) and C ( I t )

There was a weak correlation with short-term fluctua- tion at test location A. We found no correlation with the number of stimuli. However, there was a significant relationship with refractive errors: patients with larger refractive errors showed a greater learning or a smaller

Table 4. Relationship between 1earning or fatigue effects with short-term fluctuation, Rc at the number of stimuli presented and re- test fractive errors location

SF Number of Refraction Myope, Hyperope, stimuli error, n = 67 n = 40 n = 27

(absolute)

A r = 0 . 2 7 " r=0 .09 (NS) r=0 .48"* r = -0 .5 9 * * r=0 .27 (NS)

B r=0 .15 (NS) r=0.11 (NS) r = 0 . 4 4 " r = --0.47** r = 0 . 3 9 "

C r=0 .06 (NS) r=0 .04 (NS) r = 0 . 4 7 " * r = --0.56** r = 0 . 4 3 "

Rc, Regression coefficient; SF, short-term fluctuation; NS, not significant * P<0 .05 , ** P<0 .01

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fatigue effect than did emmetropic patients; this was especially true for myopic eyes.

Discussion

Although improvement in the visual field f rom the first to the second session is a routine clinical experience, scientific studies dealing with learning effects are contra- dictory. The present study deals with the learning and fatigue effects occurring during the same session. Our study revealed on the average very little time trend oc- curing during the same perimetric session. Only a few patients showed a relevant improvement or deterioration (Fig. 2). We would like to emphasize that in our study, we simply tested the threshold repeatedly at three test locations. It is possible that learning or fatigue effects may be observed more frequently under different test conditions.

The time trends observed at the different test loca- tions were significantly correlated with each other. This expected correlation was not very high, which indicates that apar t f rom features of the individual subject, other factors such as the location in the visual field may also play a role. Surprisingly, previous experience of the pa- tients with perimetry had very little and, statistically seen, no significant influence on this time trend. Sex, age and diagnosis also failed to influence the time trend. Refractive errors, however, had a significant influence: patients exhibiting refractive errors showed a significant- ly higher learning effect, especially the myopes as op- posed to the emmetropes. A learning effect may there- fore especially be expected in patients with higher refrac- tive errors.

The present results suggest that a major time trend should not be expected during a perimetric session of 5-8 min. The trends are small and may be neglected in routine clinical examinations. In clinical studies it may be worthwhile to exclude patients showing larger refrac- tive errors. The often observed learning effect therefore seems to take place not during the session but rather between sessions [5, 6, 9, 11, 12].

References

1. Aulhorn E, Harms H (1972) Visual perimetry. In: Jameson D, Hurvich LM (eds). Springer, Berlin Heidelberg New York, pp 102-145

2. Gloor BP, Schmied U, Fassler A (1981) Changes of glaucoma- tous field detects : analysis of Octopus fields with program Del- ta. Doc Ophthalmol Proc Ser 26:11-15

3. Gloor BP, Dimitriakos SA, Rabineau PA (1987) Long-term follow-up of glaucomatous fields by computerized (Octopus) perimetry. In : Krieglstein GH (ed) Glaucoma update III. Sprin- ger, Berlin Heidelberg New York, pp 123-138

4. Gramer E, De Natale R, Leydhecker W (1986) Training effect and fluctuations in long term follow up of glaucomatous visual field defects calculated with program Delta of the Octopus- perimeter 201. New Trends Ophthalmol 1:219-228

5. Greve EL (1973) Single and multiple stimulus static perimetry in glaucoma; the two phases of perimetry (thesis). Doc Oph- thalmol 36:140-141 Heijl A (1987) The implications of the results of computerized perimetry in normals for the statistical evaluation of glaucoma- tous fields. In: Krieglstein GK (ed) Glaucoma update III. Sprin- ger, Berlin Heidelberg New York, pp 115-122 Heijl A, Lindgren E, Olsson J (1989) The effect of perimetric experience in normal subjects. Arch Ophthalmol 107:81-86 Katz J, Sommer A (1987) A longitudinal study of the age- adjusted variability of automated visual fields. Arch Ophthal- mol 105:1083-1086 Lehmann FA, Faggioni R (1988) The effect of training on the visual field indices of the Octopus program C1 (abstract). Pro- ceedings, 3rd Congress of the European Glaucoma Society, Es- toril, 23 26 May, 1988 Marra G, Branzaglia P, Vanzulli G (1988) L'influenza dell'ad- destramento del paziente in perimetria cinetica automatizzata. Boll Ocul 67 : 107-111 Parrish SH, Shiffman J, Anderson DR (1984) Static and kinetic visual field testing. Arch Ophthalmol 102:1497-1502 Rabineau PA, Gloor BP, Tobler HJ (1985) Fluctuations in threshold and effect of fatigue in automated static perimetry. Doc Ophthalmol Proc Ser 30:25-33 Werner EB, Adelson A, Krupin T (1988) Effect of patient expe- rience on the results of automated perimetry in clinically stable glaucoma patients. Ophthalmology 95:76z~767 Wild JM, Dengler-Harles M, SearIe AET, O'Neill EC, Crews SJ (1989) The influence of the learning effect on automated perimetry in patients with suspected glaucoma. Acta Opthalmol 67 : 537-545

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