Keywords
diagnostic yield - imaging - cost - economic - emergency room
Diagnostic imaging has revolutionized the practice of ophthalmology. Computerized
tomographic (CT) and magnetic resonance imaging (MRI) have empowered ophthalmologists
to diagnose many ophthalmic orbital and neuro-ophthalmic conditions that previously
escaped immediate diagnosis. In an era fraught with medical malpractice and pressure
to practice cost-effective medicine, the goal of most physicians is to order studies
only when results (either positive or negative) will lead to the diagnosis or a change
in patient management.[1] Otherwise, inappropriate testing, excessive testing, or lack of needed testing may
incur a substantial cost to our healthcare system.[1] Overutilization of imaging has been a topic of particular concern in United States
emergency departments (ED),[2]
[3]
[4]
[5]
[6] where increasing utilization of diagnostic imaging leads to not only increased costs,[7] but also prolonged ED lengths of stay.[8]
Previous studies have evaluated the utilization and yield of radiologic imaging in
the outpatient work-up of neuro-ophthalmic[9]
[10]
[11]
[12]
[13]
[14]
[15] and orbital disease.[16]
[17] Others have assessed the yield of radiologic imaging in the setting of ocular trauma.[18]
[19]
[20] We sought to describe the diagnostic yield and cost of radiologic imaging for urgent
and emergent ocular conditions in a dedicated eye emergency room (ER).
Methods
The Wills Eye Hospital Institutional Review Board approved this study and the clinical
research complied with the Declaration of Helsinki. Informed consent was not obtained
in this retrospective, noninterventional, consecutive case series. Our study included
all patients evaluated in the Wills Eye Emergency Room over a 1-year period (April
1, 2017 to March 31, 2018) who underwent CT or MRI imaging of the head, orbits, face,
skull base, neck, and associated vasculature. When multiple imaging studies were performed
(i.e., MRI brain and orbits) each modality was recorded, but their results were analyzed
as a single imaging study. Patients were excluded if they were referred from an outside
institution with prior imaging.
Data collected included age, visual acuity (VA), patientreported chief complaint (CC),
principal examination finding, indication for imaging, the type and number of imaging
modalities performed, and the current procedural terminology (CPT) codes that were
billed for the imaging performed. Imaging findings were categorized into three groups
with binary outcomes: normal versus abnormal, significant versus nonsignificant, and
relevant versus nonrelevant. A finding was defined as significant if it prompted a
change in patient management. A finding was determined to be relevant if it accounted
for the patient's CC or principal examination finding.
Diagnostic yield was defined as the percentage of patients with a significant imaging
finding which prompted a change in patient care. Results were then organized into
1 of 6 outcome groups based upon their categorical binary outcomes for more granular
analysis: (1) abnormal, significant, relevant, (2) abnormal, significant, nonrelevant,
(3) abnormal, nonsignificant, relevant, (4) abnormal, nonsignificant, nonrelevant,
(5) normal, significant, nonrelevant, or (6) normal (nonsignificant, nonrelevant).
Exploratory subgroup analysis was performed based upon patient-reported CC, principal
examination finding, and indication for imaging. A full list of CC is reported in
[Table 1]. Visual disturbance was defined as those patients who complained of a subjective
change in visual perception but did not experience subjective decrease in VA or fit
into another category. The principal examination finding was defined as the examination
finding that prompted imaging. If a patient had more than one examination finding,
the examination finding that most strongly prompted imaging was selected. A full list
of principal examination findings is reported in [Table 2]. The principal examination finding of “decreased vision” was only utilized if the
patient had a VA worse than 20/20 and no other examination findings. Indication for
imaging is synonymous with the suspected diagnosis that the physician entered upon
ordering the imaging test, prior to imaging results ([Table 3]).
Table 1
The yield of imaging by chief complaint (n = 1,371)
|
|
Abnormal
|
Normal
|
|
Abnormal
|
Normal
|
|
+ Significant
|
− Significant
|
|
|
+ Relevant
|
− Relevant
|
|
− Relevant
|
+ Relevant
|
− Relevant
|
|
Chief complaint (n)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
|
Periocular swelling (93)
|
54
|
(58.1)
|
54
|
(58.1)
|
0
|
(0.0)
|
0
|
(0.0)
|
39
|
(41.9)
|
2
|
(2.2)
|
29
|
(31.2)
|
8
|
(8.6)
|
|
Bulging eye(s) (14)
|
8
|
(57.1)
|
8
|
(57.1)
|
0
|
(0.0)
|
0
|
(0.0)
|
6
|
(42.9)
|
1
|
(7.1)
|
2
|
(14.3)
|
3
|
(21.4)
|
|
Blurred vision (395)
|
204
|
(51.6)
|
182
|
(46.1)
|
12
|
(3.0)
|
10
|
(2.5)
|
191
|
(48.4)
|
44
|
(11.1)
|
43
|
(10.9)
|
104
|
(26.3)
|
|
Other (4)
|
2
|
(50.0)
|
2
|
(50.0)
|
0
|
(0.0)
|
0
|
(0.0)
|
2
|
(50.0)
|
0
|
(0.0)
|
0
|
(0.0)
|
2
|
(50.0)
|
|
Eye redness (7)
|
3
|
(42.9)
|
3
|
(42.9)
|
0
|
(0.0)
|
0
|
(0.0)
|
4
|
(57.1)
|
2
|
(28.6)
|
1
|
(14.3)
|
1
|
(14.3)
|
|
Transient vision loss (43)
|
18
|
(41.9)
|
14
|
(32.6)
|
4
|
(9.3)
|
0
|
(0.0)
|
25
|
(58.1)
|
5
|
(11.6)
|
0
|
(0.0)
|
20
|
(46.5)
|
|
Visual field loss (55)
|
22
|
(40.0)
|
22
|
(40.0)
|
0
|
(0.0)
|
0
|
(0.0)
|
33
|
(60.0)
|
5
|
(9.1)
|
2
|
(3.6)
|
26
|
(47.3)
|
|
Headache (36)
|
13
|
(36.1)
|
8
|
(22.2)
|
1
|
(2.8)
|
4
|
(11.1)
|
23
|
(63.9)
|
1
|
(2.8)
|
8
|
(22.2)
|
14
|
(38.9)
|
|
Double vision (214)
|
77
|
(36.0)
|
71
|
(33.2)
|
6
|
(2.8)
|
0
|
(0.0)
|
137
|
(64.0)
|
36
|
(16.8)
|
9
|
(4.2)
|
92
|
(43.0)
|
|
Eye pain (95)
|
32
|
(33.7)
|
29
|
(30.5)
|
2
|
(2.1)
|
1
|
(1.1)
|
63
|
(66.3)
|
9
|
(9.5)
|
20
|
(21.1)
|
34
|
(35.8)
|
|
Eyes cross/not moving (10)
|
3
|
(30.0)
|
2
|
(20.0)
|
1
|
(10.0)
|
0
|
(0.0)
|
7
|
(70.0)
|
1
|
(10.0)
|
0
|
(0.0)
|
6
|
(60.0)
|
|
Droopy eyelid (27)
|
8
|
(29.6)
|
7
|
(25.9)
|
1
|
(3.7)
|
0
|
(0.0)
|
19
|
(70.4)
|
6
|
(22.2)
|
2
|
(7.4)
|
11
|
(40.7)
|
|
Trauma (223)
|
50
|
(22.4)
|
47
|
(21.1)
|
3
|
(1.3)
|
0
|
(0.0)
|
173
|
(77.6)
|
24
|
(10.8)
|
99
|
(44.4)
|
50
|
(22.4)
|
|
Different size pupils (9)
|
2
|
(22.2)
|
2
|
(22.2)
|
0
|
(0.0)
|
0
|
(0.0)
|
7
|
(77.8)
|
1
|
(11.1)
|
0
|
(0.0)
|
6
|
(66.7)
|
|
Visual disturbance (127)
|
22
|
(17.3)
|
15
|
(11.8)
|
6
|
(4.7)
|
1
|
(0.8)
|
105
|
(82.7)
|
22
|
(17.3)
|
6
|
(4.7)
|
77
|
(60.6)
|
|
None (19)
|
3
|
(15.8)
|
3
|
(15.8)
|
0
|
(0.0)
|
0
|
(0.0)
|
16
|
(84.2)
|
4
|
(21.1)
|
7
|
(36.8)
|
5
|
(26.3)
|
Table 2
The yield of imaging by principal examination finding (n = 1,371)
|
|
Abnormal
|
Abnormal
|
Normal
|
|
Abnormal
|
Normal
|
|
+ Significant
|
+ Significant
|
+ Significant
|
+ Significant
|
- Significant
|
− Significant
|
|
|
+ Relevant
|
− Relevant
|
− Relevant
|
|
− Relevant
|
+ Relevant
|
− Relevant
|
|
Principal exam finding (n)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
|
Visual field defect (56)
|
37
|
(66.1)
|
37
|
(66.1)
|
0
|
(0.0)
|
0
|
(0.0)
|
19
|
(33.9)
|
5
|
(8.9)
|
5
|
(8.9)
|
9
|
(16.1)
|
|
Afferent pupillary defect (41)
|
26
|
(63.4)
|
24
|
(58.5)
|
2
|
(4.9)
|
0
|
(0.0)
|
15
|
(36.6)
|
8
|
(19.5)
|
1
|
(2.4)
|
6
|
(14.6)
|
|
Proptosis (29)
|
18
|
(62.1)
|
18
|
(62.1)
|
0
|
(0.0)
|
0
|
(0.0)
|
11
|
(37.9)
|
1
|
(3.4)
|
4
|
(13.8)
|
6
|
(20.7)
|
|
Other (11)
|
6
|
(54.5)
|
5
|
(45.5)
|
1
|
(9.1)
|
0
|
(0.0)
|
5
|
(45.5)
|
1
|
(9.1)
|
1
|
(9.1)
|
3
|
(27.3)
|
|
Optic nerve edema (293)
|
153
|
(52.2)
|
132
|
(45.1)
|
9
|
(3.1)
|
12
|
(4.1)
|
140
|
(47.8)
|
22
|
(7.5)
|
41
|
(14.0)
|
77
|
(26.3)
|
|
Color plate deficiency (14)
|
7
|
(50.0)
|
7
|
(50.0)
|
0
|
(0.0)
|
0
|
(0.0)
|
7
|
(50.0)
|
2
|
(14.3)
|
1
|
(7.1)
|
4
|
(28.6)
|
|
Periocular edema/erythema (88)
|
43
|
(48.9)
|
42
|
(47.7)
|
1
|
(1.1)
|
0
|
(0.0)
|
45
|
(51.1)
|
4
|
(4.5)
|
35
|
(39.8)
|
6
|
(6.8)
|
|
Optic nerve pallor (69)
|
32
|
(46.4)
|
29
|
(42.0)
|
0
|
(0.0)
|
3
|
(4.3)
|
37
|
(53.6)
|
12
|
(17.4)
|
13
|
(18.8)
|
12
|
(17.4)
|
|
Abnormal EOM (177)
|
77
|
(43.5)
|
73
|
(41.2)
|
4
|
(2.3)
|
0
|
(0.0)
|
100
|
(56.5)
|
24
|
(13.6)
|
14
|
(7.9)
|
62
|
(35.0)
|
|
Anisocoria (25)
|
10
|
(40.0)
|
9
|
(36.0)
|
1
|
(4.0)
|
0
|
(0.0)
|
15
|
(60.0)
|
3
|
(12.0)
|
0
|
(0.0)
|
12
|
(48.0)
|
|
Decreased visual acuity (48)
|
15
|
(31.3)
|
14
|
(29.2)
|
1
|
(2.1)
|
0
|
(0.0)
|
33
|
(68.8)
|
3
|
(6.3)
|
4
|
(8.3)
|
26
|
(54.2)
|
|
Periocular trauma (176)
|
52
|
(29.5)
|
49
|
(27.8)
|
3
|
(1.7)
|
0
|
(0.0)
|
124
|
(70.5)
|
15
|
(8.5)
|
62
|
(35.2)
|
47
|
(26.7)
|
|
Retinal artery occlusion (17)
|
4
|
(23.5)
|
2
|
(11.8)
|
2
|
(11.8)
|
0
|
(0.0)
|
13
|
(76.5)
|
7
|
(41.2)
|
0
|
(0.0)
|
6
|
(35.3)
|
|
Optic nerve cupping (5)
|
1
|
(20.0)
|
1
|
(20.0)
|
0
|
(0.0)
|
0
|
(0.0)
|
4
|
(80.0)
|
0
|
(0.0)
|
3
|
(60.0)
|
1
|
(20.0)
|
|
Conjunctival congestion (11)
|
2
|
(18.2)
|
1
|
(9.1)
|
1
|
(9.1)
|
0
|
(0.0)
|
9
|
(81.8)
|
4
|
(36.4)
|
0
|
(0.0)
|
5
|
(45.5)
|
|
None (165)
|
22
|
(13.3)
|
13
|
(7.9)
|
8
|
(4.8)
|
1
|
(0.6)
|
143
|
(86.7)
|
28
|
(17.0)
|
0
|
(0.0)
|
115
|
(69.7)
|
|
Ruptured globe (55)
|
7
|
(12.7)
|
7
|
(12.7)
|
0
|
(0.0)
|
0
|
(0.0)
|
48
|
(87.3)
|
4
|
(7.3)
|
33
|
(60.0)
|
11
|
(20.0)
|
|
New strabismus (70)
|
8
|
(11.4)
|
5
|
(7.1)
|
3
|
(4.3)
|
0
|
(0.0)
|
62
|
(88.6)
|
15
|
(21.4)
|
3
|
(4.3)
|
44
|
(62.9)
|
|
Intraocular/orbital FB (9)
|
1
|
(11.1)
|
1
|
(11.1)
|
0
|
(0.0)
|
0
|
(0.0)
|
8
|
(88.9)
|
0
|
(0.0)
|
7
|
(77.8)
|
1
|
(11.1)
|
|
Ptosis (10)
|
0
|
(0.0)
|
0
|
(0.0)
|
0
|
(0.0)
|
0
|
(0.0)
|
10
|
(100)
|
4
|
(40.0)
|
1
|
(10.0)
|
5
|
(50.0)
|
Table 3
The yield of imaging by indication (n = 1,371)
|
|
Abnormal
|
Normal
|
|
Abnormal
|
Abnormal
|
Normal
|
|
+ Significant
|
− Significant
|
− Significant
|
|
|
+ Relevant
|
− Relevant
|
|
− Relevant
|
+ Relevant
|
− Relevant
|
|
Indication for imaging (n)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
n
|
(%)
|
|
|
VF defect c/f CNS lesion (36)
|
23
|
(63.9)
|
22
|
(61.1)
|
1
|
(2.8)
|
0
|
(0.0)
|
13
|
(36.1)
|
4
|
(11.1)
|
4
|
(11.1)
|
5
|
(13.9)
|
|
|
Thyroid eye disease (27)
|
17
|
(63.0)
|
17
|
(63.0)
|
0
|
(0.0)
|
0
|
(0.0)
|
10
|
(37.0)
|
1
|
(3.7)
|
5
|
(18.5)
|
4
|
(14.8)
|
|
|
Orbital mass (36)
|
22
|
(61.1)
|
22
|
(61.1)
|
0
|
(0.0)
|
0
|
(0.0)
|
14
|
(38.9)
|
6
|
(16.7)
|
4
|
(11.1)
|
4
|
(11.1)
|
|
|
ON edema c/f inc ICP (148)
|
86
|
(58.1)
|
64
|
(43.2)
|
7
|
(4.7)
|
15
|
(10.1)
|
62
|
(41.9)
|
8
|
(5.4)
|
33
|
(22.3)
|
21
|
(14.2)
|
|
|
Optic neuritis (210)
|
117
|
(55.7)
|
113
|
(53.8)
|
3
|
(1.4)
|
1
|
(0.5)
|
93
|
(44.3)
|
16
|
(7.6)
|
14
|
(6.7)
|
63
|
(30.0)
|
|
|
Orbital inflammation/infection (114)
|
61
|
(53.5)
|
61
|
(53.5)
|
0
|
(0.0)
|
0
|
(0.0)
|
53
|
(46.5)
|
4
|
(3.5)
|
36
|
(31.6)
|
13
|
(11.4)
|
|
|
Other (10)
|
5
|
(50.0)
|
4
|
(40.0)
|
1
|
(10.0)
|
0
|
(0.0)
|
5
|
(50.0)
|
1
|
(10.0)
|
1
|
(10.0)
|
3
|
(30.0)
|
|
|
Cavernous carotid fistula (12)
|
5
|
(41.7)
|
4
|
(33.3)
|
1
|
(8.3)
|
0
|
(0.0)
|
7
|
(58.3)
|
2
|
(16.7)
|
1
|
(8.3)
|
4
|
(33.3)
|
|
|
Optic neuropathy (88)
|
33
|
(37.5)
|
30
|
(34.1)
|
3
|
(3.4)
|
0
|
(0.0)
|
55
|
(62.5)
|
17
|
(19.3)
|
11
|
(12.5)
|
27
|
(30.7)
|
|
|
Anisocoria (3)
|
1
|
(33.3)
|
1
|
(33.3)
|
0
|
(0.0)
|
0
|
(0.0)
|
2
|
(66.7)
|
0
|
(0.0)
|
0
|
(0.0)
|
2
|
(66.7)
|
|
|
Central EOM disorder (67)
|
22
|
(32.8)
|
21
|
(31.3)
|
1
|
(1.5)
|
0
|
(0.0)
|
45
|
(67.2)
|
6
|
(9.0)
|
2
|
(3.0)
|
37
|
(55.2)
|
|
|
CN palsy (154)
|
45
|
(29.2)
|
38
|
(24.7)
|
7
|
(4.5)
|
0
|
(0.0)
|
109
|
(70.8)
|
33
|
(21.4)
|
3
|
(1.9)
|
73
|
(47.4)
|
|
|
Orbital fracture (139)
|
38
|
(27.3)
|
37
|
(26.6)
|
1
|
(0.7)
|
0
|
(0.0)
|
101
|
(72.7)
|
19
|
(13.7)
|
50
|
(36.0)
|
32
|
(23.0)
|
|
|
Horner's syndrome (13)
|
3
|
(23.1)
|
3
|
(23.1)
|
0
|
(0.0)
|
0
|
(0.0)
|
10
|
(76.9)
|
1
|
(7.7)
|
0
|
(0.0)
|
9
|
(69.2)
|
|
|
Trauma r/o RG/IOFB (45)
|
9
|
(20.0)
|
7
|
(15.6)
|
2
|
(4.4)
|
0
|
(0.0)
|
36
|
(80.0)
|
2
|
(4.4)
|
17
|
(37.8)
|
17
|
(37.8)
|
|
|
RAO r/o stroke (22)
|
4
|
(18.2)
|
2
|
(9.1)
|
2
|
(9.1)
|
0
|
(0.0)
|
18
|
(81.8)
|
10
|
(45.5)
|
0
|
(0.0)
|
8
|
(36.4)
|
|
|
Transient vision loss (23)
|
4
|
(17.4)
|
2
|
(8.7)
|
2
|
(8.7)
|
0
|
(0.0)
|
19
|
(82.6)
|
5
|
(21.7)
|
1
|
(4.3)
|
13
|
(56.5)
|
|
|
Amaurosis (15)
|
2
|
(13.3)
|
2
|
(13.3)
|
0
|
(0.0)
|
0
|
(0.0)
|
13
|
(86.7)
|
4
|
(26.7)
|
0
|
(0.0)
|
9
|
(60.0)
|
|
|
Unexplained visual disturbance (127)
|
16
|
(12.6)
|
11
|
(8.7)
|
5
|
(3.9)
|
0
|
(0.0)
|
111
|
(87.4)
|
20
|
(15.7)
|
0
|
(0.0)
|
91
|
(71.7)
|
|
|
Ruptured globe r/o IOFB (71)
|
8
|
(11.3)
|
8
|
(11.3)
|
0
|
(0.0)
|
0
|
(0.0)
|
63
|
(88.7)
|
3
|
(4.2)
|
45
|
(63.4)
|
15
|
(21.1)
|
|
|
Headache (9)
|
0
|
(0.0)
|
0
|
(0.0)
|
0
|
(0.0)
|
0
|
(0.0)
|
9
|
(100)
|
0
|
(0.0)
|
1
|
(11.1)
|
8
|
(88.9)
|
|
Abbreviations: CN, central nerve; CNS, central nervous system; EOM, extraocular muscles;
ICP, intracranial pressure; IOFB, intraocular foreign body; RAO, retinal artery occlusion;
RG, ruptured globe; VF, visual field.
The cost of imaging was determined using the Physician Fee Schedule Search found at
the Centers of Medicare and Medicaid Services website and the 2018 conversion factor.[21] Although all CPT codes from each visit were collected, only the billed CPT codes
were analyzed. Thus, if an MRI brain and orbits were performed sequentially, only
the higher cost CPT code was analyzed in the cost analysis. The professional and technical
components were combined to obtain the total cost of the individual imaging studies
([Table 4]). No regional adjustments were performed.
Table 4
Cost of neuroimaging by study
|
Imaging study
|
Cost
|
|
CT head w/ contrast
|
$166.32
|
|
CT head w/o contrast
|
$118.08
|
|
CT head w/ and w/o contrast
|
$195.12
|
|
CT maxillofacial w/ contrast
|
$170.64
|
|
CT maxillofacial w/o contrast
|
$141.84
|
|
CT orbits w/ contrast
|
$280.80
|
|
CT orbits w/o contrast
|
$237.24
|
|
CT orbits w/ and w/o contrast
|
$306.00
|
|
CTA head w/ and w/o contrast
|
$298.44
|
|
CTA neck w/ and w/o contrast
|
$297.72
|
|
MRI brain w/o contrast
|
$235.80
|
|
MRI brain w/ and w/o contrast
|
$385.56
|
|
MRI orbit w/o contrast
|
$276.48
|
|
MRI orbit w/ and w/o contrast
|
$411.84
|
|
MRA head w/o contrast
|
$331.20
|
|
MRA head w/ contrast
|
$334.08
|
|
MRA head w/ and w/o contrast
|
$493.19
|
|
MRA neck w/o contrast
|
$366.84
|
|
MRA neck w/ contrast
|
$335.88
|
|
MRA neck w/ and w/o contrast
|
$512.63
|
Abbreviations: CT, computed tomography; CTA, computed tomography angiography; MRA,
magnetic resonance angiography; MRI, magnetic resonance imaging; w, with; w/o, without.
Note: The cost of imaging was determined using the Physician Fee Schedule Search found
at the Centers of Medicare and Medicaid Services Web site and includes both the professional
and technical components.
All statistical analyses were performedby Q.Z. and R.A.H. using SAS 9.4 (SAS Institute,
Inc, Cary, NC). The overall yield rate and its 95% confidence intervals (CIs) were
calculated. Exploratory subgroup analysis was performed as described above. The costs
of imaging per outcome group and per significant finding was calculated. Comparisons
between imaging outcome groups were tested with the Kruskal–Wallis test for continuous
variables and the Fisher's Exact test with Monte Carlo estimate for categorical variables.
Comparisons between significant outcome groups were evaluated with the chi-square
test or with Fisher's exact test when the expected cell count was <5 for categorical
variables with a Monte Carlo estimate, when appropriate. Continuous variables were
compared with the Rank Sum test. The Goodman method with Bonferroni adjustment was
used to compute simultaneous CI. A two-sided α level of 0.05 was used to determine significance.
Results
From April 1, 2017 to March 31, 2018, 14,961 patients presented to the Wills Emergency
Room for evaluation. Of those patients, 1,371 (9.2%) met inclusion criteria and underwent
imaging based upon their presentation and examination. A majority of patients had
MRI imaging studies performed (880, 64.2%). The average age was 47 years, ranging
from 5 to 97 years. In total, 2,703 imaging studies were obtained over the year. The
affected eye(s) was more often unilateral (36% right eye, 35% left eye), than bilateral
(29%).
Of the 1,371 patients who underwent imaging, 521 (38.0%) had significant findings
that resulted in a change in patient management ([Table 5]). Most of this group (469, 34.2%) had significant and relevant findings. Thirty-six
patients (2.6%) had incidental, significant, but not relevant findings on imaging.
An example from this outcome group was a patient with an incidentally discovered anterior
communicating artery aneurysm unrelated to their symptoms and examination, but requiring
neurosurgical evaluation. Finally, of the significant groups, 16 patients (1.2%) had
normal, significant, but nonrelevant exams. This group consisted solely of patients
diagnosed with idiopathic intracranial hypertension with normal scans that prompted
the physician to admit for lumbar puncture or begin empiric treatment with oral acetazolamide.
Table 5
The yield of imaging by significant and relevant findings (n = 1,371)
|
Abnormal
|
Normal
|
Abnormal
|
Normal
|
|
+ Significant
|
− Significant
|
|
+ Relevant
|
− Relevant
|
+ Relevant
|
− Relevant
|
|
Number of patients
|
469
|
36
|
16
|
163
|
228
|
459
|
|
(%)
|
(34.2%)
|
(2.6%)
|
(1.2%)
|
(11.9%)
|
(16.6%)
|
(33.5%)
|
|
95% Confidence interval
|
30.9–37.7%
|
1.7–4.0%
|
0.6–2.2%
|
9.8–14.4%
|
14.2–19.5%
|
30.2–36.9%
|
Eight hundred and fifty patients (62.0%) had scans performed that were nonsignificant.
Most of these patients' scans were normal (459, 33.5%), without significant or relevant
findings. Abnormal, nonsignificant, but relevant findings were found in 228 patients
(16.6%). An example from this outcome group included a patient with a clinically apparent
ruptured globe, confirmed on imaging without additional findings. Finally, there were
163 patients (11.9%) with abnormal findings that were nonsignificant and nonrelevant.
Examples in this outcome group include multiple patients with nonspecific white matter
changes of the brain or chronic orbital fractures not associated with their ER presentation.
Patients with significant imaging findings were more likely to be younger (44.7 vs.
48.4 years, p = 0.0006, Rank-sum) and have worse VA (VA 20/68 vs. 20/56, p = 0.015, Rank-sum). The odds of imaging resulting in a significant finding were higher
(OR 1.57, 95% CI 1.22–2.03, p = 0.001, Chi-square test) when MRI only imaging (n = 880) was performed, compared with cases where CT imaging was utilized (n = 491).
The results of the subgroup analysis by patient reported CC can be found in [Table 1]. Blurred vision (n = 395) was the most common symptom reported by patients who underwent imaging, followed
by ocular and orbital trauma (n = 223), and double vision (n = 214). The highest yield CCs were periocular swelling (58.0%), bulging eye(s) (57.1%),
and blurred vision (51.6%). The lowest yield CCs were isolated anisocoria (22.2%),
visual disturbance (17.3%), and patients who reported no complaint (15.8%).
The subgroup analysis by principal examination finding can be found in [Table 2]. The most common principal examination findings that underwent neuroimaging were
optic nerve edema (n = 293), abnormal extraocular motility (n = 177), and periocular trauma (n = 176). The highest yield principal examination findings were visual field defect
(66.1%), afferent pupillary defector AFD (63.4%), and proptosis (62.1%). The lowest
yield principal examination findings were ruptured globe (12.7%), new onset strabismus
(11.4%), intraocular or intraorbital foreign body (11.1%), and isolated ptosis (0.0%).
The results of the subgroup analysis by indication for imaging can be found in [Table 3]. The most common indications for imaging were optic neuritis (n = 210), cranial nerve palsy (n = 154), and optic nerve edema concerning for increased intracranial pressure (n = 148). The highest yield indications for imaging were visual field defect concerning
for a central nervous system (CNS) lesions (63.9%), thyroid eye disease (TED) (63.0%),
and orbital mass (61.1%). The lowest yield indications for imaging were amaurosis
(13.3%), unexplained visual disturbance (12.6%), rule out intraocular foreign body
(IOFB) after ruptured globe (11.3%), and headache (0.0%).
The cost of each imaging study can be found in [Table 4]. The total cost of imaging all 1,371 patients was $656,078.34. The average cost
of imaging per patient was $478.54. The average cost of imaging per significant finding
was $523.68, $72.81 more than the average cost per nonsignificant findings (p < 0.0001, rank sum). The average cost of imaging the abnormal, significant, and nonrelevant
group was $598.65, statistically more compared with the other outcome groups (p < 0.0001, Kruskal–Wallis; [Table 6]).
Table 6
The cost of imaging by significant and relevant findings
|
Abnormal
|
Normal
|
Abnormal
|
Normal
|
|
+ Significant
|
− Significant
|
|
+ Relevant
|
− Relevant
|
+ Relevant
|
− Relevant
|
|
Number of patients
|
469
|
36
|
16
|
163
|
228
|
459
|
|
Mean # of images/patient
|
2.07
|
2.39
|
2.44
|
2.04
|
1.54
|
2.01
|
|
Mean cost
|
$515.70
|
$598.65
|
$588.96
|
$462.69
|
$375.14
|
$484.30
|
|
(SD)
|
($269.75)
|
($304.73)
|
($280.78)
|
($248.06)
|
($223.89)
|
($247.39)
|
Abbreviation: SD, standard deviation.
Discussion
Diagnostic imaging is an invaluable tool necessary to evaluate many ophthalmic diseases,
both to establish a diagnosis and to eliminate the possibility of sight and life-threatening
diseases in patients with unclear clinical presentations. In our study, neuroimaging
was found to be significant, resulting in a change in management, in 38.0% of patients.
Neuroimaging resulted in a change in management and was related to the patient's CC
or examination findings in 34.2% of cases (significant and relevant). Our yield is
similar to two smaller studies (n = 157 and n = 168) which assessed the yield of imaging in outpatient neuroophthalmology offices.[10]
[11] Mehta et al reported significant findings in 31.3% of outpatient neuroimaging tests,
while significant and relevant findings were seen in 28.9%.[10] Pradhan et al reported significant findings in 36.1% of images, with both significant
and relevant findings seen in 32.4%.[11]
The overall cost of imaging all 1,371 patients was $656,078.34. The cost per clinically
significant finding in our study was $523.68. The cost per clinically significant
and relevant finding was $515.70, less than the $1,764.19 per finding reported by
Mehta et al who used the reimbursement rates from 2011.[10] The overall cost effectiveness in our study also compares favorably to other specialties.
Jordan et al reported the cost per significant finding in the work-up of chronic headache
to be $34,535, while Liu et al reported the cost per significant finding in the work-up
of vocal cord dysfunction to be $2,304.[22]
[23] Our decreased cost is likely multifactorial and related to the decreasing cost of
technology, increased number of imaging machines, and decreasing reimbursement.
Beyond the cost of performing the diagnostic imaging on our healthcare system, we
must consider the human and financial cost if a diagnosis is missed. The Institute
of Medicine has estimated that approximately 12 million people in the United States
experience some form of diagnostic error/delay in their medical evaluation, resulting
in 10% of patient deaths and 6 to 17% of hospital adverse events.[24] The Institute of Medicine goes on to estimate the national cost of inefficiently
delivered care due to diagnostic error, mistakes, and the subsequent preventable complications
to be $130 billion annually.[25] Importantly, we must remember that the more significant cost of misdiagnosis falls
upon the patients and their families in the form of lifelong care and lost income
due to permanent disabilities or death.
The choice of neuroimaging modality (MRI vs. CT) is specific to the patient's presentation,
suspected pathology, and comorbidities (e.g., presence of an MRI incompatible pacemaker).
We found the odds of a significant finding were 57% higher when MRI only imaging was
performed, compared with cases where CT imaging was utilized. We suspect that the
lower yield may be due to the physician's low threshold to utilize CT imaging as a
screening modality in the settings of orbital trauma, penetrating trauma to assess
for a ruptured globe, and to rule out IOFB in a ruptured globe.[19] Unlike MRI imaging, CT imaging is relatively less expensive ([Table 5]) and is shorter test in duration, making it a more practical screening instrument.
In our subgroup analysis by CC, the extraocular findings of periocular swelling and
bulging eye(s) had the highest diagnostic yield (58.1 and 57.1%, respectively). These
findings were in alignment with Mehta et al who found the orbital “complaint” of proptosis
was associated with the highest yield on imaging.[10] Patients who did not report a CC (i.e., “none”) and patients who described a visual
disturbance were the lowest yield CCs (15.8 and 17.3%, respectively). The patients
who reported no CC were all asymptomatic at the time of presentation and were referred
in by providers for concerning exam findings. The three patients who reported no CC
and had significant findings on imaging, all had a relevant exam finding of optic
nerve edema. Imaging was consistent with the diagnosis of optic neuritis in two patients
and idiopathic intracranial hypertension in the third. Although symptom driven evaluations
are at the core of the ophthalmologic assessment, we cannot be dismissive of patients
without complaints or with abstract complaints, especially if their history or exam
is suspicious for pathology.
Subgroup analysis by principal examination finding revealed a high diagnostic yield
in patients with a visual field defect on confrontation (66.1%), an APD(63.4%), and
proptosis (62.1%). This is in alignment with Mehta et al and reinforces the importance
of close ophthalmic examination, paying attention for these findings.[10] The lowest yield examination findings were isolated ptosis (0.0%), ruptured globe
with an IOFB (11.1%), strabismus (11.4%), and ruptured globe (12.7%). The examination
findings of isolated ptosis and strabismus were of similar low yield in the series
by Mehta et al (0.0 and 0.0% significant, respectively). This suggests that a finding
of isolated ptosis should seldomly warrant imaging unless there is strong suspicion
for a structural lesion on complete neurological examination and review of systems.
In contrast, it is always recommended to acquire CT imaging for the examination findings
of ruptured globe with or without a foreign body as missing an IOFB is clinically
devastating.[19] Of the 55 patients who underwent imaging for a ruptured globe an IOFB was found
in seven (12.7%) necessitating removal. Of the nine patients who had a clinically
apparent ruptured globe with an IOFB, one patient (11.1%) had a second, clinically
undetected, orbital foreign body. Our data also support the imaging of patients who
are not overtly clinically ruptured, but give a history of penetrating, explosive,
projectile, or blunt force trauma directly to the eye. In our study, 7 of 45 patients
(15.6%) with such history were found to have occult ruptured globes on imaging requiring
emergent operating room repair. Finally, a normal ophthalmic examination was associated
with significant findings in 13.3% of the patients. This result should be approached
with caution and should remind the ophthalmologist that a normal exam can conceal
significant pathology.
Subgroup analysis by indication revealed a high diagnostic yield for a visual field
defect concerning for a CNS lesion (63.9%), TED (63.0%), and orbital mass (61.1%).
Similarly, Mehta et al had a high diagnostic yield for TED (70.0%) and Pradhan et
al had a high diagnostic yield for extraocular orbital indications (68.7%).[10]
[11] The lowest yield indications with imaging in our series were amaurosis (13.3%),
unexplained visual disturbance (12.6%), rule out an IOFB in a known ruptured globe
(11.3%), and headache (0.0%). Headache was similarly the lowest yield indication in
the study by Mehta et al (0.0%). Jordan et al[26] andWeingarten et al[22] have both published large studies (n = 1,233 and n = 863, respectively) looking at the yield of MRI imaging in patients with isolated
headaches and found significant findings in only 0.0 to 1.5% of patients. This suggests
that a headache without any additional neurologic or ophthalmic findings rarely warrants
imaging. However, what if this headache represents an early symptom of an intracranial
mass or aneurysm? This misdiagnosis certainly carries a human and financial cost that
is more than the cost of the imaging. In a similar vein, the American Heart Association
and the American Stroke Association have advocated for urgent MRI imaging of all patients
who present with a transient ischemic attack (including amaurosis) as 10 to 15% of
patients will have a stroke within 3 months, with half of those occurring within the
first 48 hours.[27] Across multiple studies looking at MRI results in patients with transient ischemic
attacks, MRI has shown at least one area of acute diffusion restriction in 25 to 67%
of cases and at least onearea of infarct (acute or chronic) in 46 to 81% of the cases.[27] We strongly support the neurological work-up of patients who present with amaurosis,
including MRI of the brain. Regardless of the relatively low diagnostic yield for
some indications, a resounding theme is that missing a potential imaging finding in
patients with concerning history or examination findings may lead to devastating consequences
for both the patient and the physician.
In this study we sought to determine the diagnostic yield and cost of imaging for
ophthalmic conditions in an ER setting to help guide ophthalmologists in making cost-effective
imaging decisions. However, we acknowledge that there are limitations to this study.
This study was designed to be exploratory in nature, to help set the foundation for
larger, prospective, more detailed work. Although patients may present independently,
our dedicated eye ER serves as an urgent or emergent tertiary referral center and
our patient population is likely not representative of the general population. In
contrast, it is also possible that referring providers will not send their patients
for evaluation if they obtain imaging and make a diagnosis independently. Instead,
they may opt to refer the patients directly to an appropriate subspecialist, leading
to an underestimation of diagnostic yield. We also chose to include incidentally found
pathology and normal imaging results that changed management (i.e., idiopathic intracranial
hypertension) into our diagnostic yield. This decision was done to reflect a more
real-world yield of imaging. We have reported the significant and relevant findings
alongside the total significant findings for comparison. Finally, we calculated cost
of imaging using only the billed CPT codes. This may underestimate the total theoretical
cost to the hospital system but does give a better real-world representation of the
cost of imaging.
In conclusion, neuroimaging for urgent and emergent ocular conditions provides useful
diagnostic data that may change patient management at cost to the healthcare system.
It is important for the ophthalmologist to be aware of the specific CCs, examination
findings, and indications that are of particularly high and low yield. Finally, although
imaging produces expenditures to our healthcare systems, we must not forget the substantial
cost of misdiagnosis.
