Seminars in Ophthalmology, 2015; 30(4): 289–296 ! Informa Healthcare USA, Inc. ISSN: 0882-0538 print / 1744-5205 online DOI: 10.3109/08820538.2013.859279
ORIGINAL ARTICLE
Psychomotor Vigilance and Visual Field Test Performance Inci I. Dersu1, Tayyeba K. Ali1, Horace J. Spencer2, Sarah M. Covey1, Megan S. Evans1, and Richard A. Harper1 1
Department of Ophthalmology, Jones Eye Institute, Little Rock, Arkansas, USA and 2Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
ABSTRACT Introduction: Visual field test is an invaluable tool to evaluate the detection and progression of glaucoma. On the other hand, as a subjective test, reliable results depend on patients’ optimum performance including vigilance during the test. The purpose of this study was to understand patient’s attitude and preferences about the visual field test taking, and in addition to assess the relationship between the reliability indices of visual field testing (VFT) and the Walter Reed Psychomotor Vigilance Test (PVT). Material and methods: In this cross-sectional, non-interventional study, VFT reliability indices were recorded for all 140 patients. In the 46 patients who completed the PVT, average reaction time and minimum reaction times were recorded. All 140 patients completed a survey about their VFT experience. Results: Based on the survey results, most subjects found VFT to be difficult. Subjects who rated their VFT performance excellent/good had similar VFT reliability rates compared to the ones with fair/poor self-assessments. The average reaction time (RT) was 0.6 seconds (0.3–1.9 seconds). Higher average RT was associated with increased age and less formal education (p50.001 and 0.03, respectively). There was a marginally significant correlation between average RT and the VFT ‘‘reliability’’ status (p = 0.045). Conclusions: While VFT is the least favorable part of the work-up for glaucoma patients, their self-assessment about VFT performance did not correlate with current VF reliability indicators. Although reliability of the VFT was not strongly affected by slower reaction times when tested by the PVT, the effect of psychomotor reaction time on other aspects of test outcomes is unknown and warrants further investigation. Keywords: Reliability, Self-Assesment of performance, survey, visual field test, Walter Reed Palm-Held Psychomotor Vigilance Test
INTRODUCTION
glaucoma. One of the first recorded accounts of peripheral visual field evaluation was from Hippocrates around the fifth century B.C., when he described s patient with a hemianopsia.4 Since then, many advances have been made, including the introduction of automated visual field testing (VFT) around the 1970s, which paved the way for Franz Fankhauser to develop the Octopus, and later for Anders Heijl to work on the Humphrey Visual Field.5,6 Smarter strategies, such as the Swedish Threshold Interactive Algorithm (SITA) for the Humphrey Visual Field Test machines, have
Glaucoma affects more than 60 million people worldwide and is a significant public health issue: it directly impacts an individual’s independence, and poses a substantial economic burden.1,2 Open-angle glaucoma alone affects more than two million individuals in the United States and this number will increase to more than three million by 2020, due to the rapidly aging population.3 Visual field evaluation is a subjective yet imperative tool in the diagnosis and management of
Received 31 May 2013; revised 22 August 2013; accepted 9 October 2013; published online 27 December 2013 Correspondence: Inci Irak Dersu, M.D., Department of Ophthalmology, Jones Eye Institute/UAMS, 4301 W. Markham Street, Slot # 523, Little Rock, AR 72205, USA. E-mail: [email protected]
289
290 I.I. Dersu et al. significantly reduced testing times in comparison to full threshold testing.7 Yet, according to published survey results, VFT remains one of the least favorite tests among glaucoma patients.8 While it has not been previously studied, it is possible that this ‘‘dislike’’ may lead to less-than-optimum performance and increased variability of test results. Good understanding of technical instructions, optimal vision, and alertness, among other factors, contribute to a reliable VFT. Although advanced age is viewed as an obstacle to reliable testing due to decreased mental alertness and physical performance, the extent of vigilance or alertness has not been widely studied.9 Furthermore, it is not known whether subjective factors, such as how the patient values and rates her test performance and the comfort level during the test, weigh on outcome and reliability. This study was undertaken to determine the specific factors that may help predict performance and reliability outcomes as well as to better understand patient preferences and opinions about VFT. We aimed to objectively test psychomotor vigilance in glaucoma patients and to investigate the correlation between psychomotor vigilance and reliability indices of VFT, using the Walter Reed Psychomotor Vigilance Test (PVT), a validated tool to measure sustained wakefulness.10–12
METHODS This was a cross-sectional, observational, one-center study conducted at the University of Arkansas for Medical Sciences. A total of 140 subjects with a primary diagnosis of glaucoma were included in the study. Inclusion criteria were patients who were: (1) 40–85 years of age; (2) undertaking static automated white-on-white threshold perimetry; and (3) with vision 20/60 or better in the tested eye. The study was approved and monitored by the Institutional Review Board and complied with the guidelines of the Declaration of Helsinki. Informed written consent was obtained from all subjects, after their regularly scheduled VFT but before the survey was completed in order to minimize the Hawthorne effect on the technician and subject during the VFT.
Survey Upon completion of VFT, a questionnaire was given to those subjects who consented to participate in the study. It consisted of 21 multiple-choice questions (as listed in Appendix 1) that addressed multiple factors, ranging from test performance to room comfort. The subject was asked about the comfort of his testing chair, chin rest, eye patch, room temperature, and eye pain during the test; ‘‘if the patient answered ‘‘yes’’ to all these question’’, subject was deemed ‘‘comfortable’’.
Walter Reed Palm-Held Psychomotor Vigilance Test The Walter Reed Palm-Held Psychomotor Vigilance Test (PVT) was added during the late enrollment phase to objectively measure vigilance and alertness. This hand-held device measures reaction time to a black-and-white bull’s eye on a screen and has been validated to measure fatigue and sleep deprivation.10–12 A five-minute version of the Palm PVT was used. Subjects tap on the screen when the stimulus is seen and the test continues until a fixed number of valid answers are given or at the end of five minutes, whichever comes first. Test output reflects minimum, maximum, median, and average Reaction Times (RT) and test duration.
Statistical Analysis Demographic and ophthalmologic characteristics were summarized using counts and percentages for categorical data, while means and standard deviations (or medians and inter-quartile ranges, when appropriate) were used to summarize continuous data. Chi-square tests were used to evaluate the association between two categorical variables; e.g. evaluating test comfort versus reliability. Student’s two-sample t-tests or Wilcoxon rank-sum tests were used to compare two groups with respect to a continuous variable. Finally, Spearman’s correlation coefficients were used to describe the association between two continuous or ordinal variables. P values less than 5% were considered to be statistically significant.
Visual Field Test RESULTS A single experienced technician read a standardized script that introduced the visual field test, SITA Standard 24-2 (Humphrey Field Analyzer II; Carl Zeiss Meditec, Dublin, CA), to all subjects. VFT was deemed ‘‘reliable’’ if all three reliability indicators (fixation loss, false positive and false negative rates) were lower than 20%.
A total of 140 patients participated in this study. Of these patients, 46 participated in the PVT arm. The characteristics of subjects are shown in Table 1. The average age was 66.3 10.2 years. More females participated than males. The average Mean Defect was 4.4 þ 5.5 dB. Seminars in Ophthalmology
Psychomotor Vigilance and Visual Field Performance 291 Age and education strongly correlated with average RT. Association was weaker between reliability of the VFT and average RT (Table 2). Subjects were asked about their comfort during the VFT. No association was found between comfort level and RT or VFT reliability, as shown in Table 3. Subjects were also asked how they felt about their VFT performance. Those who rated their VFT performance ‘‘excellent or good’’ did not differ from the group who rated their test performance ‘‘fair or poor’’ in terms of
TABLE 1. Characteristics of patients. N (%) Sex Female Male Education High School or Less More than High School Race White African American Unknown Diagnosis POAG Glaucoma Suspect Narrow Angle Pigmentary Traumatic ICE syndrome
92 (65.7) 48 (34.3) 50 (35.7) 90 (64.3) 85 (60.7) 54 (38.6) 1 (0.7) 68 42 23 4 2 1
(48.5) (30.0) (16.4) (2.8) (1.4) (0.7)
greater alertness and producing a more reliable VFT (Figure 1, Table 3). Survey results showed that while 80% of patients thought checking IOP is a good way to monitor glaucoma, only 61% felt that VFT is a good method. Thirty-six percent of patients noted that the VFT was the hardest part of the work-up and exam, while 23% noted dilation, 19% the bright lights, and 14% IOP measurement as the hardest part. Only 36% noted that the test gets easier with time and 72% felt that testing only one eye at a time would make no difference in improving ease or comfort of VFT. Finally, when asking about the best time of day to undergo testing, 44% preferred early morning, 32% preferred early afternoon, and 22% preferred late morning. The average RT measured by PVT was 0.6 seconds (range 0.3–1.9 sec.), and the average minimum RT was 0.3 0.1 seconds (range 0.2–0.6 sec.). Increased age and less than a high school education were associated with a significantly increased average RT on PVT (p50.001 and 0.03, respectively), as shown in Figure 2. Increased age was also associated with an increased minimum RT on PVT (p = 0.002). Although ‘‘reliability of the test’’ as referred each indicator’s (i.e. fixation loss, false positive or false negative rates) being 520% decreased with increasing average RT (p = 0.045), there was no association with the each indicator alone and RT (Table 2).
DISCUSSION TABLE 2. Association of variables with average Reaction Time (RT). Spearman’s correlation coefficients were used to measure the strength of the monotonic associations. Unadjusted Analysis Correlation Age Education Number of Drops Reliability Loss to Fixation Duration False Positive False Negative
0.4743 0.3282 0.0061 0.2675 0.1824 0.2808 0.0554 0.1162
Adjusted Analysisy
p Value Correlation p Value 50.001 0.026 0.968 0.075 0.225 0.059 0.715 0.442
– – 0.1486 0.3070 0.2103 0.1558 0.0625 0.1084
– – 0.348 0.045 0.171 0.313 0.687 0.484
@
Spearman’s correlation adjusted for Age and Education.
Despite the major advances in optic nerve and nerve fiber layer imaging technology, the visual field test remains an invaluable tool to test patients’ visual function. Using a subjective test is an advantage, particularly in the moderate and advanced stages of glaucoma, to examine how this disease interferes with patients’ daily activities and quality of life. In this study, more than one-third of the patients rated visual field test as the hardest part of the glaucoma office visit. Our results are consistent with a previous study in which participants rated VFT as their least favorite test while they rated the intraocular pressure measurement (IOP) as the most favorable.8 Similarly, our study found that the IOP measurement was rated
TABLE 3. Participant’s rating of VFT performance and test comfort. Participant Rating of VFT Performance Visual Field Reliabilityy % (n) Fixation Loss % (SD) Duration min (SD)
Test Comfort
Excellent/Good (n = 83)
Fair/Poor (n = 57)
p Value
No (n = 46)
Yes (n = 89)
p Value
46.8 (36) 17.4 (18.2) 6.1 (1.3)
41.4 (24) 21.4 (19.1) 6.3 (1.3)
0.534 0.211 0.397
47.8 (22) 18.0 (17.4) 6.2 (1.3)
42.7 (38) 19.6(19.4) 6.1 (1.4)
0.573 0.640 0.931
y 2-tests were used to analyze reliability. Percentages and counts are presented.
!
2015 Informa Healthcare USA, Inc.
292 I.I. Dersu et al.
1.5 Average RT
Wilcoxon Rank-Sum Test p-value: 0.112 1.0
Reaction Time
0.5
0.6
Wilcoxon Rank-Sum Test p-value: 0.150
0.5
Minimum RT
0.4
0.3
0.2 Excellent/ Good
Fair/ Poor
VFT Performance Rating FIGURE 1. Association between VFT performance rating and average (RT).
as a more favorable part of the work-up and exam, following visual acuity assessment and refraction. Patients in our study did not find that VFT became easier over time. This may not be evidence for an absence of learning effect over time. However, it is consistent with the literature that after the second VFT or after longer intervals between tests (more than 6–12 months), and for shorter SITA strategies, the learning effect may not be so obvious.13–15 Because the average visual field loss was mild in our subjects, the results may have been different once the disease has progressed further and tests are taken more often. One aspect of our study was to investigate whether or not subjects who thought they performed well on the VFT had better VFT reliability indices. Results showed that this was not the case. Subjects who rated their VFT performance excellent or good had similar VFT reliability rates compared to the ones with fair or poor self-assessments. This is consistent with clinical collective experience that complainers about their test performance may not
necessarily be the ones who give the unreliable results and vice versa. To our knowledge, this is the first study to measure attention level as measured by RT by using the Walter Reed Psychomotor Vigilance Test (PVT) among glaucoma and glaucoma suspect patients undergoing VFT. Aging was the strongest variable to affect the reaction time, in addition to educational status. Our hypothesis was that higher levels of attentiveness would be associated with lower false-negative, falsepositive, or fixation loss. This assumption was only valid when strict criteria of all three aforementioned reliability indices less than 20% were applied after adjusting for age and education. The lack of strong relationship between alertness and reliability may be explained by the fact that SITA already takes into account speed of response, and adjusts the interval between stimuli according to the subject’s earlier response. Subject alertness and visual field test performance was explored in the Collaborative Initial Glaucoma Treatment Study: a 10-item alertness behavior scale as a subscale of the Sickness Impact Seminars in Ophthalmology
Psychomotor Vigilance and Visual Field Performance 293
1.5
Spearman’s ρ: 0.474 p-value:
ORIGINAL ARTICLE
Psychomotor Vigilance and Visual Field Test Performance Inci I. Dersu1, Tayyeba K. Ali1, Horace J. Spencer2, Sarah M. Covey1, Megan S. Evans1, and Richard A. Harper1 1
Department of Ophthalmology, Jones Eye Institute, Little Rock, Arkansas, USA and 2Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
ABSTRACT Introduction: Visual field test is an invaluable tool to evaluate the detection and progression of glaucoma. On the other hand, as a subjective test, reliable results depend on patients’ optimum performance including vigilance during the test. The purpose of this study was to understand patient’s attitude and preferences about the visual field test taking, and in addition to assess the relationship between the reliability indices of visual field testing (VFT) and the Walter Reed Psychomotor Vigilance Test (PVT). Material and methods: In this cross-sectional, non-interventional study, VFT reliability indices were recorded for all 140 patients. In the 46 patients who completed the PVT, average reaction time and minimum reaction times were recorded. All 140 patients completed a survey about their VFT experience. Results: Based on the survey results, most subjects found VFT to be difficult. Subjects who rated their VFT performance excellent/good had similar VFT reliability rates compared to the ones with fair/poor self-assessments. The average reaction time (RT) was 0.6 seconds (0.3–1.9 seconds). Higher average RT was associated with increased age and less formal education (p50.001 and 0.03, respectively). There was a marginally significant correlation between average RT and the VFT ‘‘reliability’’ status (p = 0.045). Conclusions: While VFT is the least favorable part of the work-up for glaucoma patients, their self-assessment about VFT performance did not correlate with current VF reliability indicators. Although reliability of the VFT was not strongly affected by slower reaction times when tested by the PVT, the effect of psychomotor reaction time on other aspects of test outcomes is unknown and warrants further investigation. Keywords: Reliability, Self-Assesment of performance, survey, visual field test, Walter Reed Palm-Held Psychomotor Vigilance Test
INTRODUCTION
glaucoma. One of the first recorded accounts of peripheral visual field evaluation was from Hippocrates around the fifth century B.C., when he described s patient with a hemianopsia.4 Since then, many advances have been made, including the introduction of automated visual field testing (VFT) around the 1970s, which paved the way for Franz Fankhauser to develop the Octopus, and later for Anders Heijl to work on the Humphrey Visual Field.5,6 Smarter strategies, such as the Swedish Threshold Interactive Algorithm (SITA) for the Humphrey Visual Field Test machines, have
Glaucoma affects more than 60 million people worldwide and is a significant public health issue: it directly impacts an individual’s independence, and poses a substantial economic burden.1,2 Open-angle glaucoma alone affects more than two million individuals in the United States and this number will increase to more than three million by 2020, due to the rapidly aging population.3 Visual field evaluation is a subjective yet imperative tool in the diagnosis and management of
Received 31 May 2013; revised 22 August 2013; accepted 9 October 2013; published online 27 December 2013 Correspondence: Inci Irak Dersu, M.D., Department of Ophthalmology, Jones Eye Institute/UAMS, 4301 W. Markham Street, Slot # 523, Little Rock, AR 72205, USA. E-mail: [email protected]
289
290 I.I. Dersu et al. significantly reduced testing times in comparison to full threshold testing.7 Yet, according to published survey results, VFT remains one of the least favorite tests among glaucoma patients.8 While it has not been previously studied, it is possible that this ‘‘dislike’’ may lead to less-than-optimum performance and increased variability of test results. Good understanding of technical instructions, optimal vision, and alertness, among other factors, contribute to a reliable VFT. Although advanced age is viewed as an obstacle to reliable testing due to decreased mental alertness and physical performance, the extent of vigilance or alertness has not been widely studied.9 Furthermore, it is not known whether subjective factors, such as how the patient values and rates her test performance and the comfort level during the test, weigh on outcome and reliability. This study was undertaken to determine the specific factors that may help predict performance and reliability outcomes as well as to better understand patient preferences and opinions about VFT. We aimed to objectively test psychomotor vigilance in glaucoma patients and to investigate the correlation between psychomotor vigilance and reliability indices of VFT, using the Walter Reed Psychomotor Vigilance Test (PVT), a validated tool to measure sustained wakefulness.10–12
METHODS This was a cross-sectional, observational, one-center study conducted at the University of Arkansas for Medical Sciences. A total of 140 subjects with a primary diagnosis of glaucoma were included in the study. Inclusion criteria were patients who were: (1) 40–85 years of age; (2) undertaking static automated white-on-white threshold perimetry; and (3) with vision 20/60 or better in the tested eye. The study was approved and monitored by the Institutional Review Board and complied with the guidelines of the Declaration of Helsinki. Informed written consent was obtained from all subjects, after their regularly scheduled VFT but before the survey was completed in order to minimize the Hawthorne effect on the technician and subject during the VFT.
Survey Upon completion of VFT, a questionnaire was given to those subjects who consented to participate in the study. It consisted of 21 multiple-choice questions (as listed in Appendix 1) that addressed multiple factors, ranging from test performance to room comfort. The subject was asked about the comfort of his testing chair, chin rest, eye patch, room temperature, and eye pain during the test; ‘‘if the patient answered ‘‘yes’’ to all these question’’, subject was deemed ‘‘comfortable’’.
Walter Reed Palm-Held Psychomotor Vigilance Test The Walter Reed Palm-Held Psychomotor Vigilance Test (PVT) was added during the late enrollment phase to objectively measure vigilance and alertness. This hand-held device measures reaction time to a black-and-white bull’s eye on a screen and has been validated to measure fatigue and sleep deprivation.10–12 A five-minute version of the Palm PVT was used. Subjects tap on the screen when the stimulus is seen and the test continues until a fixed number of valid answers are given or at the end of five minutes, whichever comes first. Test output reflects minimum, maximum, median, and average Reaction Times (RT) and test duration.
Statistical Analysis Demographic and ophthalmologic characteristics were summarized using counts and percentages for categorical data, while means and standard deviations (or medians and inter-quartile ranges, when appropriate) were used to summarize continuous data. Chi-square tests were used to evaluate the association between two categorical variables; e.g. evaluating test comfort versus reliability. Student’s two-sample t-tests or Wilcoxon rank-sum tests were used to compare two groups with respect to a continuous variable. Finally, Spearman’s correlation coefficients were used to describe the association between two continuous or ordinal variables. P values less than 5% were considered to be statistically significant.
Visual Field Test RESULTS A single experienced technician read a standardized script that introduced the visual field test, SITA Standard 24-2 (Humphrey Field Analyzer II; Carl Zeiss Meditec, Dublin, CA), to all subjects. VFT was deemed ‘‘reliable’’ if all three reliability indicators (fixation loss, false positive and false negative rates) were lower than 20%.
A total of 140 patients participated in this study. Of these patients, 46 participated in the PVT arm. The characteristics of subjects are shown in Table 1. The average age was 66.3 10.2 years. More females participated than males. The average Mean Defect was 4.4 þ 5.5 dB. Seminars in Ophthalmology
Psychomotor Vigilance and Visual Field Performance 291 Age and education strongly correlated with average RT. Association was weaker between reliability of the VFT and average RT (Table 2). Subjects were asked about their comfort during the VFT. No association was found between comfort level and RT or VFT reliability, as shown in Table 3. Subjects were also asked how they felt about their VFT performance. Those who rated their VFT performance ‘‘excellent or good’’ did not differ from the group who rated their test performance ‘‘fair or poor’’ in terms of
TABLE 1. Characteristics of patients. N (%) Sex Female Male Education High School or Less More than High School Race White African American Unknown Diagnosis POAG Glaucoma Suspect Narrow Angle Pigmentary Traumatic ICE syndrome
92 (65.7) 48 (34.3) 50 (35.7) 90 (64.3) 85 (60.7) 54 (38.6) 1 (0.7) 68 42 23 4 2 1
(48.5) (30.0) (16.4) (2.8) (1.4) (0.7)
greater alertness and producing a more reliable VFT (Figure 1, Table 3). Survey results showed that while 80% of patients thought checking IOP is a good way to monitor glaucoma, only 61% felt that VFT is a good method. Thirty-six percent of patients noted that the VFT was the hardest part of the work-up and exam, while 23% noted dilation, 19% the bright lights, and 14% IOP measurement as the hardest part. Only 36% noted that the test gets easier with time and 72% felt that testing only one eye at a time would make no difference in improving ease or comfort of VFT. Finally, when asking about the best time of day to undergo testing, 44% preferred early morning, 32% preferred early afternoon, and 22% preferred late morning. The average RT measured by PVT was 0.6 seconds (range 0.3–1.9 sec.), and the average minimum RT was 0.3 0.1 seconds (range 0.2–0.6 sec.). Increased age and less than a high school education were associated with a significantly increased average RT on PVT (p50.001 and 0.03, respectively), as shown in Figure 2. Increased age was also associated with an increased minimum RT on PVT (p = 0.002). Although ‘‘reliability of the test’’ as referred each indicator’s (i.e. fixation loss, false positive or false negative rates) being 520% decreased with increasing average RT (p = 0.045), there was no association with the each indicator alone and RT (Table 2).
DISCUSSION TABLE 2. Association of variables with average Reaction Time (RT). Spearman’s correlation coefficients were used to measure the strength of the monotonic associations. Unadjusted Analysis Correlation Age Education Number of Drops Reliability Loss to Fixation Duration False Positive False Negative
0.4743 0.3282 0.0061 0.2675 0.1824 0.2808 0.0554 0.1162
Adjusted Analysisy
p Value Correlation p Value 50.001 0.026 0.968 0.075 0.225 0.059 0.715 0.442
– – 0.1486 0.3070 0.2103 0.1558 0.0625 0.1084
– – 0.348 0.045 0.171 0.313 0.687 0.484
@
Spearman’s correlation adjusted for Age and Education.
Despite the major advances in optic nerve and nerve fiber layer imaging technology, the visual field test remains an invaluable tool to test patients’ visual function. Using a subjective test is an advantage, particularly in the moderate and advanced stages of glaucoma, to examine how this disease interferes with patients’ daily activities and quality of life. In this study, more than one-third of the patients rated visual field test as the hardest part of the glaucoma office visit. Our results are consistent with a previous study in which participants rated VFT as their least favorite test while they rated the intraocular pressure measurement (IOP) as the most favorable.8 Similarly, our study found that the IOP measurement was rated
TABLE 3. Participant’s rating of VFT performance and test comfort. Participant Rating of VFT Performance Visual Field Reliabilityy % (n) Fixation Loss % (SD) Duration min (SD)
Test Comfort
Excellent/Good (n = 83)
Fair/Poor (n = 57)
p Value
No (n = 46)
Yes (n = 89)
p Value
46.8 (36) 17.4 (18.2) 6.1 (1.3)
41.4 (24) 21.4 (19.1) 6.3 (1.3)
0.534 0.211 0.397
47.8 (22) 18.0 (17.4) 6.2 (1.3)
42.7 (38) 19.6(19.4) 6.1 (1.4)
0.573 0.640 0.931
y 2-tests were used to analyze reliability. Percentages and counts are presented.
!
2015 Informa Healthcare USA, Inc.
292 I.I. Dersu et al.
1.5 Average RT
Wilcoxon Rank-Sum Test p-value: 0.112 1.0
Reaction Time
0.5
0.6
Wilcoxon Rank-Sum Test p-value: 0.150
0.5
Minimum RT
0.4
0.3
0.2 Excellent/ Good
Fair/ Poor
VFT Performance Rating FIGURE 1. Association between VFT performance rating and average (RT).
as a more favorable part of the work-up and exam, following visual acuity assessment and refraction. Patients in our study did not find that VFT became easier over time. This may not be evidence for an absence of learning effect over time. However, it is consistent with the literature that after the second VFT or after longer intervals between tests (more than 6–12 months), and for shorter SITA strategies, the learning effect may not be so obvious.13–15 Because the average visual field loss was mild in our subjects, the results may have been different once the disease has progressed further and tests are taken more often. One aspect of our study was to investigate whether or not subjects who thought they performed well on the VFT had better VFT reliability indices. Results showed that this was not the case. Subjects who rated their VFT performance excellent or good had similar VFT reliability rates compared to the ones with fair or poor self-assessments. This is consistent with clinical collective experience that complainers about their test performance may not
necessarily be the ones who give the unreliable results and vice versa. To our knowledge, this is the first study to measure attention level as measured by RT by using the Walter Reed Psychomotor Vigilance Test (PVT) among glaucoma and glaucoma suspect patients undergoing VFT. Aging was the strongest variable to affect the reaction time, in addition to educational status. Our hypothesis was that higher levels of attentiveness would be associated with lower false-negative, falsepositive, or fixation loss. This assumption was only valid when strict criteria of all three aforementioned reliability indices less than 20% were applied after adjusting for age and education. The lack of strong relationship between alertness and reliability may be explained by the fact that SITA already takes into account speed of response, and adjusts the interval between stimuli according to the subject’s earlier response. Subject alertness and visual field test performance was explored in the Collaborative Initial Glaucoma Treatment Study: a 10-item alertness behavior scale as a subscale of the Sickness Impact Seminars in Ophthalmology
Psychomotor Vigilance and Visual Field Performance 293
1.5
Spearman’s ρ: 0.474 p-value:
