Keywords
glaucoma - surgery - tube shunt - Ahmed - Baerveldt - fellows - surgical education
Surgical education in ophthalmology is imperative for ensuring patient safety and
preparing future physicians for independent surgical practice. In the subspecialty
of glaucoma, fellows commit 1 year following ophthalmology residency to gain additional
surgical experience in complex aqueous filtering surgeries, including tube shunt placement
and trabeculectomy. While the importance of surgical education in glaucoma fellowship
is widely acknowledged, there is limited literature reporting the quantitative impact
of a dedicated fellowship program on surgical efficiency. Additionally, the logistical
implications of surgical scheduling in ophthalmology fellowship programs at various
points in the academic year have not been explored in detail.
Several studies have sought to characterize trainee surgical outcomes in ophthalmic
surgical training programs.[1]
[2]
[3]
[4]
[5]
[6]
[7] For residents, surgical experience is one of the primary drivers of improvements
in operative case times for cataract surgery over the course of training, with more
cases yielding shorter case times, particularly early in training.[8]
[9]
[10] While trainees may need a considerable number of cases as primary surgeon to gain
surgical mastery, there is a clear opportunity cost of trainee surgical involvement.
A recent cost-analysis paper found that in California (fiscal year 2014), 1 minute
of operating room time was worth $36 to $37.[11] In strabismus surgery, the cost of resident involvement was reported to be $3141.95
per year due to increased operative times.[12] For orthopaedic surgery residents in 1996 to 1997, operating room costs were increased
by $661.85 on average for trainee cases due to increased operative time.[13] In plastic surgery, 2011 costs were estimated to be $275 per trainee involved in
a given case, and over $440 per case for craniofacial surgical fellows.[14] As such, understanding potential improvements in surgical case times over the course
of glaucoma fellowship could help us better measure surgical training and could galvanize
efforts to improve surgical education for fellows.
The landscape of glaucoma filtering surgery has changed dramatically in the last two
decades. Studies have shown an increase in tube shunt placement with a concomitant
decrease in trabeculectomy surgery among national Medicare claims[15] as well as resident and fellow case logs[16]
[17]; this may be due to several factors, including the feared complications of bleb
filtering surgery (bleb-related endophthalmitis, hypotonous maculopathy) as well as
improvements in tube shunt devices. In the wake of the Tube versus Trabeculectomy
study[18] and the Primary Tube Versus Trabeculectomy study,[19] which have provided invaluable comparisons between tube shunt and trabeculectomy
surgeries, it is likely that rates of tube shunt administration will continue to increase.
Education in tube shunt placement will be a core component of glaucoma surgical training
for the foreseeable future; however, the current state of glaucoma fellows' case times
for tube shunt placement has not been reported. As such, we sought to report operative
case times for glaucoma fellows at the Duke University Eye Center and the University
of North Carolina (UNC) over a 5-year period (2014–2019), to determine whether fellows
attain greater surgical efficiency over the course of the academic year.
Materials and Methods
Prior approval for this retrospective study was obtained from the Duke University
Health System and University of North Carolina Institutional Review Boards, and the
requirement for informed consent was waived. This study complied with the Health Insurance
Portability and Accountability Act of 1996 and followed the tenets of the Declaration
of Helsinki.
Retrospective clinical data regarding tube shunt placement cases was abstracted using
the electronic health record at UNC and Duke (Epic, Verona, WI). We reviewed all procedures
coded using Current Procedural Terminology 66180 for aqueous shunt placement performed
from July 2014 to June 2019. All cases that were primarily performed by the fellow
were identified and included by attending faculty attestation and/or documentation.
The cases included constitute a representative sample of each fellow's surgical cases
with select faculty at each institution and are not intended to represent the holistic
surgical curriculum offered by each respective program. Tube shunt procedures performed
in combination with a secondary procedure (i.e., cataract surgery, trabeculectomy,
vitrectomy) were excluded from analysis to eliminate the confounding effect of a second
procedure on operative time.
Patient demographic data (age and sex), procedure date, fellow involved, attending/supervising
surgeon, and type of tube shunt placed (Ahmed glaucoma valve, New World Medical Inc,
Rancho Cucamonga, CA; Baerveldt glaucoma implant, Abbott Laboratories Inc, Abbott
Park, IL) were recorded. For the purposes of statistical analysis, procedure dates
were characterized as occurring during the first or second half of the academic year
(July–June); as such, first-half cases were performed between July 1 and December
31 of a given year, and second-half cases were performed between January 1 and June
31 of a given year.
Statistical analysis was performed using Stata, software version 16.1 (StataCorp,
College Station, TX). Operative case times were compared between groups using an independent-sample,
two-tailed t-test, with the level of significance defined as <0.05.
Results
Five hundred and seventy-three tube shunt placement surgeries performed by 28 glaucoma
fellows at Duke University Medical Center and UNC Health System over a 5-year period
(2014–2019) were analyzed. Of the 28 fellows, 22 (79%) were trained at Duke and six
trained at UNC (21%). Seventeen (61%) fellows were female, and 11 (39%) were male.
Of the 573 surgeries performed, all operations involved the fellow as primary operator
under supervision of an attending surgeon, and no surgeries included a combined procedure
(i.e., cataract surgery, trabeculectomy, vitrectomy, etc.). Demographic data pertinent
to the surgeries performed is detailed in [Table 1]. Of 573 tube shunt placements, 385 (67%) were Ahmed glaucoma valves and 188 (33%)
were Baerveldt glaucoma drainage devices. The mean patient age was 66.3 (standard
deviation 14.1) years. Two hundred seventy-nine (51%) patients were female, and 328
(57%) of the surgeries were performed at Duke.
Table 1
Demographic data for surgical cases
|
Characteristic
|
Value
|
|
Tube shunt surgeries
|
|
|
Ahmed
|
67% (385/573)
|
|
Baerveldt
|
33% (188/573)
|
|
Patient age in years (mean ± SD)
|
66.3 ± 14.1
|
|
Patient gender
|
51% female (279/573)
|
|
Fellow gender
|
61% female (17/28)
|
|
Institution
|
|
|
Duke Eye Center
|
57% (328/573)
|
|
UNC
|
43% (245/573)
|
Abbreviations: SD, standard deviation; UNC, University of North Carolina.
Surgical case times by half of the academic year (i.e., first half, July–December,
second half January–June) are reported in [Table 2]. When pooling data from all fellows, second half cases were significantly shorter
than first half cases, by an average of 6 minutes per case (55.3 ± 17.1 minutes vs.
61.0 ± 17.4 minutes, p <0.001). Female fellows trended toward shorter first and second half case times than
male fellows; however, both female (53.5 ± 17.3 minutes vs. 59.3 ± 16.4 minutes, p = 0.003) and male (57.3 ± 16.8 minutes vs. 63.2 ± 18.6 minutes, p = 0.008) fellows had significantly shorter second half case times when compared with
first half case times. Duke (55.5 ± 14.4 minutes vs. 59.2 ± 15.9 minutes, p = 0.026) and UNC (55.0 ± 20.2 minutes vs. 63.3 ± 19.2 minutes, p = 0.001) fellows both had significantly shorter case times in the second half of
the academic year. Baerveldt case times were significantly longer than Ahmed case
in the first half (64.2 ± 20.0 minutes vs. 59.3 ± 15.8 minutes, p = 0.028) but only trended toward being longer than Ahmed cases in the second half
(57.8 ± 18.9 minutes vs. 54.1 ± 16.2 minutes, p = 0.070).
Table 2
Surgical case times for tube shunt placements by glaucoma fellows at Duke University
Eye Center and University of North Carolina over a 5-year period (2014–2019)
|
First half[a] case times in minutes, mean ± SD (N)
|
Second half case times in minutes, mean ± SD (N)
|
p-Value[b]
|
|
All fellows
|
61.0 ± 17.4 (264)
|
55.3 ± 17.1 (309)
|
<0.001
|
|
Male fellows
|
63.2 ± 18.6 (111)
|
57.3 ± 16.8 (145)
|
0.008
|
|
Female fellows
|
59.3 ± 16.4 (153)
|
53.5 ± 17.3 (164)
|
0.003
|
|
UNC fellows
|
63.3 ± 19.2 (112)
|
55.0 ± 20.2 (133)
|
0.001
|
|
Duke fellows
|
59.2 ± 15.9 (152)
|
55.5 ± 14.4 (176)
|
0.026
|
|
Ahmed cases
|
59.3 ± 15.8 (175)
|
54.1 ± 16.2 (210)
|
0.002
|
|
Baerveldt cases
|
64.2 ± 20.0 (89)
|
57.8 ± 18.9 (99)
|
0.025
|
Abbreviations: SD, standard deviation; UNC, University of North Carolina.
a Date used were from the academic calendar year. First half dates fell between July
and December in a given year; second half dates fell between January and June.
b
p-Value from two-tailed t-test, p-value less than 0.05 was considered significant.
Discussion
In this retrospective study of surgical case times among glaucoma fellows at two tertiary
academic medical centers, we found that surgical case times were significantly shorter
in the second half of the academic year for all fellows, suggesting an improvement
in surgical efficiency with increasing surgical volume and supervised surgical education.
We also report that surgical case times in the first half of fellowship (which may,
in part, reflect baseline surgical experience prior to fellowship) did not significantly
differ between male and female fellows, although female fellows tended to have shorter
case times in the first and second halves of the academic year. Additionally, after
1 year of glaucoma fellowship, fellows at Duke and UNC had nearly identical average
case times (UNC 55.0 ± 20.2 minutes, Duke 55.5 ± 14.4 minutes). While Baerveldt cases
were longer than Ahmed cases in the first half of the academic year, this difference
only trended toward significance in the second half, and significant improvements
in both Ahmed and Baerveldt case times were observed when comparing first to second
half cases. These findings, taken together, suggest that fellows become significantly
more efficient surgeons during the academic year, which may have implications for
surgical scheduling at academic medical centers and emphasizes the value of surgical
experience in glaucoma training.
In an analysis of resident-performed and attending-performed tube shunt placements
in a United States ophthalmology residency program, clinical outcomes were found to
be similar; however, resident-performed cases were significantly longer than the attending
cases (55 minutes vs. 50 minutes, p = 0.02).[7] While our study did not seek to explicitly compare fellow-performed cases with attending-performed
cases, these results are consistent with our study, which showed longer case times
at the beginning of fellowship (just following residency) when compared with the end
of fellowship (at the point of transition to attending surgeon). Understanding fellow-performed
surgical case times is important for assessing the true cost of glaucoma fellow education,
as case times significantly influence the cost and efficiency of providing surgical
care.[11]
[12] While our study only characterizes surgical case times among fellows at two academic
centers over 5 years, we are able to provide an estimate of expected, average case
times for glaucoma fellows during the first and second half of academic training,
which may be used by perioperative administration to forecast operating room availability
and minimize unnecessary costs associated with under-prediction of operative case
times, particularly in the beginning of the academic year. A prior study showed that
first cataract surgery cases in a given day are longer than subsequent cases; further
analyses may reveal unique trends in glaucoma surgery performed by fellows throughout
the day, which could further inform planned case times.[20]
Our preliminary analysis suggests that fellow gender and training institution did
not significantly impact operative case times at the end of the academic year. In
this study of 28 fellows, a variety of ophthalmology residency programs were represented;
however, we did not specifically assess variation in first half surgical case times
with varying levels of glaucoma surgical experience during residency. This would likely
be difficult to assess without residual confounding, as most training programs have
exceedingly few primary glaucoma surgeries performed by residents, and resident wet
laboratory/simulation experience may also influence surgical comfort/efficiency in
early fellowship. It is possible that further study across multiple institutions may
reveal disparities in surgical experience prior to glaucoma fellowship between various
fellowship programs. The relationship between fellow gender and surgical case times
may be noncontributory; however, it is notable that female surgeons trended toward
shorter cases in both halves of the academic year.
This study is limited by several factors inherent to its retrospective nature. As
we are collecting historical case times using the electronic health record retrospectively,
we cannot independently confirm that recorded case times are reflective of actual
intraoperative time. Additionally, while case times were generally consistent between
Duke and UNC, we cannot rule out that minor differences in operating room workflow
and recording of procedure start and end times between institutions could have influenced
our results. We also only included cases in which we could definitively state that
the fellow was the primary operator in all cases. Thus, each fellow performed significantly
more cases in a given academic year that were not included in this study. As such,
our study is not reflective of the holistic surgical experiences at either fellowship
program and should not be taken as an objective assessment of fellow surgical volume
and/or experience at the program. Additionally, while we excluded combination surgeries
due to case-to-case variability, we cannot fully control other factors contributing
to case time variability, including prior ocular surgeries, intraoperative complications,
or extenuating circumstances leading to outliers in operative case times. We have
attempted to control for these potential confounders by including a large number of
primary tube shunt placements (intentionally excluding tube shunt revision/replacement)
which are likely very homogenous inpatient presentation and case difficulty. We analyzed
Ahmed and Baerveldt tubes separately and compared with one another given the potential
for differences due to procedural considerations. Overall, we feel that our cohort
is representative of routine, uncomplicated primary tube shunt placements by glaucoma
fellows at tertiary academic medical centers. The inclusion of other centers in future
studies would improve the generalizability of our results. Finally, one cannot presume
that shorter case times are equivalent to “better” surgical care, as one can perform
a surgery quickly and carelessly. However, it is exceedingly unlikely that 28 fellows
under close and direct supervision by attending faculty became more reckless over
the course of the academic year. To definitively state this, visual outcomes would
need to be included, which would require a carefully designed prospective study with
strict exclusion criteria for alternative sources of complications including comorbid
ocular conditions and unrelated surgery or trauma, for example.
This study provides a foundation for further research into glaucoma fellow education
and surgical performance throughout the academic year. This study can also be applied
to other surgical fields and could serve as a basis for more efficient operative room
scheduling with regards to trainees. Future directions for research include assessing
clinical outcomes (i.e., intraocular pressure control, visual acuity) in fellow-performed
cases throughout the academic year, characterizing operative case times for other
common surgical procedures (i.e., trabeculectomy, phacoemulsification), characterizing
fellows' subjective perceptions of improvement throughout the academic year prospectively,
and inclusion of fellow-performed cases at other tertiary academic medical centers.
In this study, we show that surgical efficiency, as assessed using the surrogate of
operative case times, improves over the course of the academic year among glaucoma
fellows.
