Introduction
Colorectal cancer (CRC) ranks 3 rd in cancer-related mortality for men and women,
with an estimated 149,500 new cases and 52,980 deaths in the United States in 2021
[1]. From 1969 to 2017, colorectal cancer mortality has decreased by more than 50 %,[1] with a particularly steep decline of 3 % per year in the early 2000 s [2]. The incidence and mortality of colorectal cancer is declining, which is associated
with improvements in colon cancer screening rates and quality of colonoscopy. These
improvements include technological advances, improved bowel preparation, and the application
of quality parameters, such as adenoma detection rate (ADR). Data from the Nurses’
Health Study and the Health Professionals Follow-up cohort demonstrate colonoscopy
is associated with a reduced incidence of both distal and proximal CRC [3].
CRC screening programs are cost-effective, but require significant resources [4], and efforts to improve the performance of colonoscopy as a screening tool have
been the focus of a substantial and growing body of research. Payers are shifting
towards value-based reimbursement, and hospital systems as well as physicians are
looking at ways to provide high-value care. Colonoscopy-related quality measures have
been identified to establish standards in the performance of colonoscopies, with ADR
standing out as the most important quality metric [5]. An increase in adenoma detection is associated with a lower risk of colorectal
cancer mortality [6]. Identifying factors that increase ADR are currently being investigated with the
aim of optimizing colonoscopy effectiveness. Two elements suspected of influencing
ADR include endoscopist fatigue [7]
[8]
[9], procedure time, and the number of consecutive hours that colonoscopy is performed
[10]
[11]
[12]
[13]. Almadi et al found ADR decreases if colonoscopy is performed ≤ 3 hours compared
to > 3 hours after the start of each endoscopy session [7]. Performing procedures in half-day blocks appears to improve ADR, especially for
afternoon procedures [14]. While some studies have not shown procedure time to impact ADR [15]
[16], this may be partially due to a variable effect of timing of day and fatigue on
individual physicians [9]. The role of eye fatigue, also known as “computer vision syndrome”, has received
attention in radiology literature [17]
[18], but has heretofore not been addressed as it relates to the performance of colonoscopy.
The term “computer vision syndrome,” also known as digital eye strain, describes eye
symptoms in persons exposed to computer screens and video display units (VDU) with
flat-panel displays. In 2016, Porcar et al. evaluated the presence of eye symptoms
in amongst one hundred sixteen non-presbyopic VDU users with flat-panel displays [19]. Seventy-two percent of participants reported eye symptoms related to VDU use [19]. Eye symptoms increased with duration of VDU use, and markedly increased with more
than six hours of screen use (P = 0.01). Computer use has increased in healthcare with the growing use of electronic
medical records; healthcare workers may experience a high prevalence of computer vision
syndrome, with symptoms corresponding to increased screen time [20].
The relationship between eye strain and ambient light has been explored in the field
of radiology, and several studies have investigated optimal lighting conditions for
the interpretation of dental imaging [21]
[22]
[23]
[24]
[25]. Evidence suggests that eye strain symptoms are prevalent amongst radiologists [26], and excessively bright lighting may negatively affect diagnostic accuracy [27]. Krupinski et al. found that radiologists experience more symptoms of eye strain
at the end of a work day, and diagnostic accuracy is worse at the end of the work
day [18]. Differences in adaptation between a bright screen and a room with low lighting
may contribute to eye strain [28]. Typical radiology reading rooms have ambient light of 1 to 60 lux. For most liquid
crystal display (LCD) monitors with standard settings, ambient light may be increased
to 75 to 150 lux, which may improve symptoms of eye strain [28].
The above studies have found that the number of hours a physician performs procedures
consecutively affects ADR, and that the more hours spent using a VDU, the more eye
symptoms people experienced. There are limited data available regarding eye symptoms
related to flat-panel displays. Adaptation between a bright screen and a room with
low lighting and its contribution to eye strain as a day progresses is yet to be explored
in the field of gastroenterology.
The aims of this study were to determine if use of ambient lighting vs low lighting
during screening colonoscopy affects adenoma detection rates, to determine if ambient
lighting is associated with fewer symptoms of strain in colonoscopists, and to explore
physician preferences regarding lighting conditions.
Methods
We conducted a single-center study at an independent community-based teaching hospital
comparing ADR in screening colonoscopies performed in low lighting with those performed
with ambient lighting. Low lighting was defined as < 75 lux, whereas ambient lighting
was defined as 75 to 150 lux. All cases included in the study involved adult patients
undergoing screening colonoscopy with a participating gastroenterologist. Diagnostic
colonoscopies, history of colon resection, colorectal cancer, and cases performed
in children, pregnant women, and prisoners were excluded from analysis. Cases involving
gastroenterology fellows were also excluded.
Eight male gastroenterologists and one female gastroenterologist participated in the
study. A tenth gastroenterologist expressed intent to participate, but left their
practice, and was thus removed from the study. The average age of participating gastroenterologists
was 48 years. Each physician served as their own control. Seven of the nine participating
physicians required corrective lenses. Physicians requiring visual correction used
updated corrective lenses during all procedures. For the retrospective data collection
portion of the study, participating gastroenterologists performed their entire day
of procedures with low lighting, including diagnostic procedures. Use of narrow-band
imaging was to the discretion of the physician. All procedures were performed with
high-definition Olympus colonoscopes (EVIS EXERA III PCF-H190 L and EVIS EXERA III
CF-HQ190 L). All monitors used for endoscopy were 42-inch high-definition screens;
the same monitors were used in both the retrospective and prospective arms.
Retrospective data were collected over a 6-month period on screening colonoscopies
performed in procedure rooms with low lighting from January 2017 to June 2017. Low
lighting was defined as lux < 75. Data included any adenoma detection during screening
colonoscopy. Adenoma detection rates were calculated, and defined by the percentage
of screening colonoscopies where at least one adenomatous polyp was found. Withdrawal
time was measured, which was defined by cecum time to completion of colonoscopy. Overhead
lights were turned off for these procedures, leaving only minimal light from equipment
in the room (low light). At the start of the study, measurements with a lux meter
confirmed low lighting in the range of 0 to 75 lux.
Prospective data were then collected on colonoscopies performed with ambient lighting
during the same 6 calendar months the following year, from January 2018 to June 2018. Clinical
engineering adjusted room lighting to 75 to 150 lux for the prospective cases. Measurements
with a lux meter confirmed ambient lighting in the range of 75 to 150 lux.
The first case of the day was defined as the first screening colonoscopy performed
during the day of procedures. If only one screening colonoscopy was performed, then
this was categorized as a “first case” if performed during the first half of the day
of procedures or as the “last case” if performed during the latter half of the day
of procedures.
A validated eye fatigue survey was completed by all gastroenterologists before and
after the use of ambient lighting ([Table 1]), with the extent of symptoms rated on a scale of 0 to 6 (adapted from Hayes, et
al) [29]. An eye strain score was calculated as the sum of the numerical responses to each
question for each participant. The lowest possible eye strain score was 0, and the
highest possible score was 60. Eye strain scores were compared before and after the
use of ambient light. Satisfaction surveys were completed by gastroenterologists,
anesthesiologists, nurses, and technicians ([Table 2] and [Table 3]).
Table 1
Symptom assessment survey.
|
None
|
Slight
|
Mild
|
Moderate
|
Somewhat bad
|
Bad
|
Severe
|
|
Blurred vision at near distances, e. g. book or newspaper (with your usual glasses or contact lenses).
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
|
Blurred vision at intermediate distances, e. g. computer screen (with your usual glasses or contact lenses)
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
|
Blurred vision at far distances, e. g. computer screen (with your usual glasses or contact lenses)
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
|
Difficulty or slowness in refocusing my eyes from one distance to another
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
|
Irritated or burning eyes
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
|
Dry eyes
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
|
Eyestrain
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
|
Headache
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
|
Tired eyes
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
|
Sensitivity to bright lights
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
Table 2
Ambient Light Satisfaction Survey results from staff (nurses, technicians and anesthesiologists).
|
Strongly disagree
|
Disagree
|
Neutral
|
Agree
|
Strongly agree
|
|
I prefer working with the lights on
|
13.6 %
|
22.7 %
|
27.3 %
|
22.7 %
|
13.6 %
|
|
Completing my work is easier
|
0 %
|
31.8 %
|
36.4 %
|
18.2 %
|
13.6 %
|
|
It is easier to detect changes in patient’s clinical status
|
4.5 %
|
18.1 %
|
31.8 %
|
31.8 %
|
13.6 %
|
|
Communication between members of the healthcare team improve with the lights on
|
4.5 %
|
27.3 %
|
45.4 %
|
13.6 %
|
9.1 %
|
|
I experience fewer symptoms of eye strain with the lights on
|
18.1 %
|
4.5 %
|
40.9 %
|
22.7 %
|
13.6 %
|
Table 3
Ambient Light Satisfaction Survey results from gastroenterologists.
|
Strongly disagree
|
Disagree
|
Neutral
|
Agree
|
Strongly agree
|
|
I prefer working with the lights on
|
0 %
|
33 %
|
22 %
|
11 %
|
33 %
|
|
Completing my work is easier
|
0 %
|
22 %
|
33 %
|
22 %
|
22 %
|
|
It is easier to detect changes in patient’s clinical status
|
0 %
|
11 %
|
11 %
|
44 %
|
33 %
|
|
Communication between members of the healthcare team improve with the lights on
|
0 %
|
11 %
|
44 %
|
22 %
|
33 %
|
|
I experience fewer symptoms of eye strain with the lights on
|
0 %
|
0 %
|
44 %
|
22 %
|
33 %
|
A power calculation was performed using GraphPad StatMate 2 software (GraphPad Software
Inc, San Diego CA). With an expected ADR of 35 % and 80 % power, 400 subjects in each
group were necessary to detect a 10 % improvement in ADR. Summary statistics were
calculated for self-report symptom assessment and satisfaction surveys ([Table 2], [Fig. 1]). Overall ADR was calculated for each physician separately by lighting conditions
(i. e. low lighting vs. ambient lights) and averaged for overall ADR by lighting conditions
([Table 4]). Pearson Chi-square tests were performed to compare differences in ADR, including
change from first to last cases between lighting conditions ([Table 5]). Comparison of eye strain score in low light and ambient light was performed using
Wilcoxon matched-pairs signed-ranks test. Analyses were performed using SAS, version
9.4 (SAS Institute, Cary North Carolina, United States) and InStat (GraphPad Software,
San Diego, California, United States). This study was approved by the Advocate Institutional
Review Board (IRB # 6665). This study was registered with clinicaltrials.gov (NCT04441242).
Fig. 1 Eye strain scores reported by physicians (numbered 1–8) before ambient light (first
bar columns, shown in blue) and after ambient light (second bar column, shown in green).
Physicians 1 and 8 reported no symptoms after ambient light. Data is shown for all
physicians with complete eye strain survey data (one physician in the study had incomplete
eye strain data). The average eye strain scores are indicated by the final columns,
with an average eye strain score of 8.12 after low light and 5.63 after ambient light.
Table 4
Screening colonoscopy ADR for participating physicians with low lighting and ambient
lighting.
|
All cases screened with low lighting
|
All cases screened with ambient lighting
|
|
Participant
|
Total screening colonoscopies
|
Overall ADR
|
Total screening colonoscopies
|
Overall ADR
|
|
Physician 1
|
4
|
50.0 %
|
14
|
50.0 %
|
|
Physician 2
|
103
|
29.1 %
|
125
|
22.4 %
|
|
Physician 3
|
54
|
48.1 %
|
38
|
50.0 %
|
|
Physician 4
|
75
|
30.7 %
|
142
|
43.7 %
|
|
Physician 5
|
65
|
33.8 %
|
85
|
40.0 %
|
|
Physician 6
|
18
|
44.4 %
|
5
|
20.0 %
|
|
Physician 7
|
4
|
50.0 %
|
1
|
0.0 %
|
|
Physician 8
|
61
|
47.5 %
|
68
|
51.5 %
|
|
Physician 9
|
114
|
26.3 %
|
133
|
25.6 %
|
|
Overall
|
498
|
34.5 %
|
611
|
36.0 %
|
The overall difference in ADR (1.5 %) was not statistically significant (P = 0.611).
Table 5
Change in ADR from first to last case with ambient lighting and low light conditions.
|
|
Colonoscopies
|
ADR
|
% difference
|
P value
|
|
Low lighting (N = 498)
|
First case
|
200
|
37.5 %
|
–5.60 %
|
0.0104
|
|
Last case
|
166
|
31.9 %
|
|
Ambient lighting (N = 611)
|
First case
|
232
|
34.1 %
|
+2.80 %
|
|
Last case
|
187
|
36.9 %
|
Results
We compared 498 retrospectively collected control cases performed with low lighting
with 611 prospectively collected intervention cases performed with ambient lighting
by the same nine gastroenterologists. Of the 498 low light cases, 172 adenomas were
detected, with an ADR of 34.5 %. Of the 611 ambient light cases, 220 adenomas were
detected, with an ADR of 36.0 % (P = 0.6109). Of the cases screened with low lighting, the ADR was 37.5 % among the
first cases of the day and 31.9 % among last cases of the day, demonstrating a 5.6 %
decrease in ADR (P = 0.2658). Of the cases screened with ambient lighting, the ADR was 34.1 % among
first cases of the day and 36.9 % among last cases of the day, representing a 2.80 %
increase (P = 0.5445). The difference in the overall difference in ADR between first and last
cases when screened with ambient lighting (+ 2.80 %) versus low lighting (–5.60 %),
was statistically significant (8.40 % total unit change, P = 0.01, [Table 3] and [Table 4]). Average withdrawal times were 11.8 minutes in the retrospective group and 11.8
minutes in the prospective group. In the retrospective arm, 51.0 % of individuals
undergoing screening colonoscopy were male and 49.0 % were female, with an average
age of 58.9 years. In the prospective arm, 42.7 % were male and 57.3 % were female,
with an average age of 58.9 years. A logistical regression analysis was performed.
After controlling for sex, age and procedure time, the effect of ambient lighting
on adenoma detection increased, approaching statistical significance (OR = 1.281 [0.981,
1.674]; P = 0.0689).
Results of eye strain scores before and after ambient light are shown in [Fig. 1], listed by physician. The average eye strain score prior to ambient light was 8.12,
compared with 5.63 after ambient light (P = 0.3341). Two physicians who previously described symptoms did not experience any
symptoms after using ambient light. Eye Strain Score with Low Light vs Ambient Light.
Results of satisfaction surveys for all staff are shown in [Table 2] (gastroenterologists, nurses, technicians, anesthesiology). Of the respondents,
64.6 % agreed, strongly agreed or were neutral regarding preference working with ambient
light. Some 19.4 % strongly agreed they preferred working with ambient light, compared
with 9.7 % who strongly disagreed. Of the respondents, 71 % agreed, strongly agreed
or were neutral that working with ambient lighting made completion of their work easier.
Of the respondents, 54 % felt ambient light made it easier to detect changes in a
patientʼs status. Of the respondents, 16.1 % strongly agreed that communication between
members of the healthcare team improved with ambient light, compared with 3.2 % who
strongly disagreed. Of respondents, 80.7 % agreed, strongly agreed or were neutral
that they experienced fewer symptoms of eye strain working with ambient light.
Results of satisfaction surveys of gastroenterologists are shown in [Table 3]. The majority of gastroenterologists agreed or strongly agreed that it was easier
to detect changes in patient’s clinical status (77 %) and communication between members
of the healthcare team was improved with the use of ambient light (55 %). The majority
of gastroenterologists (55 %) agreed or strongly agreed that they experienced fewer
symptoms of eye strain with ambient light. The majority of gastroenterologists agreed,
strongly agreed, or were neutral that they preferred working with ambient light (66 %)
and completing their work was easier (77 %).
Discussion
This study is the first to examine optimal lighting settings in the endoscopy suite.
Screening colonoscopies are often performed with low light. Low light conditions during
the performance of endoscopy could plausibly exacerbate the symptoms of eye strain.
Eye strain tends to worsen as the day progresses, with the use of display monitors
in rooms with low lighting. Although the 1.5 % difference in overall ADR between all
cases conducted with ambient lighting compared with low lighting was not statistically
significant, this is an expected finding and is likely due to the minimal effect of
eye strain on adenoma detection for cases performed early in the day. From the first
case to the last case of the day, ADR increased by 2.8 % in the ambient light group
and decreased 5.6 % in the low light group. The difference between these changes was
statistically significant (P = 0.01). Our data suggest that performing screening colonoscopies with ambient light
may improve the change in ADR from the beginning of the day to the end of the work
day, as compared with low lighting, where ours and other studies have demonstrated
that ADR decreases during a day of procedures [7].
Improvement in ADR between the first and last colonoscopy (as opposed to the expected
decrease in ADR) may be related to improved symptoms of eye strain, even though the
measured decrease in the average eye strain score (8.12 vs 5.63) did not reach statistical
significance (P = 0.3341). This discrepancy may be due to inadequate sampling, as symptoms were assessed
at only two points in time in a small group of endoscopists. Symptom recall may also
have been affected by survey timing. For example, physicians completing the eye strain
survey at the start of the day or work week may recall fewer symptoms when compared
with physicians completing surveys at the end of the day. Of note, the overall burden
of eye strain symptoms within this group of physicians was relatively low, so the
detection of significant changes in eye strain in our group may not have been feasible.
It is possible that ambient lighting could improve symptoms in populations with greater
burden of eye strain. Female physicians may experience more symptoms of eye strain
[17]. The distribution of gender within this study is similar to that observed with gastroenterologists
nationwide;[30] as such, it is difficult to determine if there are gender differences in eye strain
symptoms. Future studies could explore eye strain symptoms in the endoscopy suite
with optimization of survey timing and frequency with additional focus on gender differences
and groups with a higher prevalence of symptoms.
Additional means of objectively measuring eye strain include critical flicker–fusion
(CCF) frequency and monitoring of blinking and squinting [31]. There is evidence supporting the use of CFF as a metric representing eye fatigue,
with declining values correlating with symptoms of eye strain. Reduced blinking rate
and incomplete blinking may also correspond to eye strain symptoms. These objective
measures are used in conjunction with subjective measures of eye strain symptoms [31]. In our pilot study, we chose to focus directly on the symptoms of eye strain, as
we believe this outcome has the most relevance to practicing physicians. Future studies
may be considered to evaluate objective measures of eye strain, and their potential
role in explaining differences in eye strain and variation in adenoma detection rate.
This study has a few limitations. First, by definition, this study is not randomized.
The durability of lighting settings’ effect on eye strain symptoms is not known. As
such, we chose to evaluate eye strain after prolonged periods of time with consistent
light settings. We chose to conduct the study during the same part of the year to
avoid seasonal variation in environmental light exposure. The retrospective nature
of the low light group precludes observer bias, whereas physician participants in
the prospective group were aware of their involvement in a research study. In addition,
the brightness of the light in endoscopy rooms cannot be directly measured in the
retrospective group. However, the conditions, lighting settings, and equipment in
the room were unchanged and post-hoc measurements of light intensity indicate the
lighting retrospective group was within the low light range (< 75 lux).
Our sample consisted of a small group of physicians, and the groups were independent
in their exposure. Including the same physicians in both the low light and ambient
light groups served to neutralize many confounding factors, such as years of experience,
skill, education, etc.; while this limits generalizability, it improves the quality
of such an analysis. The prospective group contained fewer males and more females
than the retrospective group, which may lead to a lower prevalence of adenomas in
the prospective population. This could mask the effect of ambient lighting on ADR.
After controlling for gender, age and procedure time in a logistical analysis, the
effect of ambient light on overall ADR approached significance. Some gastroenterologists
in the study performed relatively few colonoscopies, and ADR varied by physician.
We chose to include all participating physicians, because the impact of ambient light
on different gastroenterologists may vary, and including data from more physicians
may provide a more accurate understanding of the overall effect of lighting conditions
on screening colonoscopy. We planned to look for correlates related to ADR in the
future. However, our data consist of too small of a group of individuals for this
type of analysis.
Finally, the use of narrow band imaging was allowed at the discretion of the physician
performing colonoscopy. A meta-analysis published in 2019 suggests that the use of
second-generation narrow band imaging during screening colonoscopy is associated with
a higher ADR than high-definition white light endoscopy. We believe these limitations
have minimal impacts on the results; however, randomized prospective trials would
be useful in confirming our findings.
Satisfaction survey responses by physicians, nurses, and technicians appeared generally
favorable for the use of ambient lighting, though this study was not designed to evaluate
staff satisfaction. More respondents felt they experienced fewer symptoms of eye strain
with ambient light (41 % vs 19 %), and most respondents felt ambient lighting made
it easier to detect changes in patient status (54 %). While it is plausible that ambient
lighting may lead to more timely recognition of changes in patient status, this study
does not provide data to answer that question. Since completion of the study, three
of the nine participating gastroenterologists have changed their practice and now
routinely use ambient lighting during endoscopic procedures. Adjusting light settings
to ambient light in the endoscopy suite may have a positive impact on satisfaction
among physicians and staff.
Conclusions
In summary, screening colonoscopy with ambient lighting (75–150 lux) may improve the
differential change in ADR that occurs from the beginning to the end of the day. The
use of ambient lighting was associated with a trend towards improved overall ADR after
controlling for age, gender, and procedure time, which did not reach statistical significance.
Improvement in ADR in later cases of the day may be due to improved symptoms of eye
fatigue experienced by physicians performing endoscopy, although the present study
does not prove that eye strain is the mechanism for this improved performance. Satisfaction
by physicians and staff working in conditions of ambient lighting in our study was
generally favorable, and resulted in a third of participating gastroenterologists
choosing to adopt the routine use of ambient light. Future studies on optimal lighting
settings for gastrointestinal endoscopy are warranted.
