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Relationship Between Preferred Sleeping Position and Asymmetric Visual Field Loss in Open-Angle Glaucoma Patients
Relationship Between Preferred Sleeping Position and Asymmetric Visual Field Loss in Open-Angle Glaucoma Patients KYOUNG NAM KIM, JIN WOOK JEOUNG, KI HO PARK, DONG MYUNG KIM, AND ROBERT RITCH PURPOSE:
To investigate the relationship between preferred sleeping position and asymmetric visual field (VF) loss in open-angle glaucoma (OAG) patients. DESIGN: Retrospective, cross-sectional study. METHODS: Six hundred and ninety-two (692) patients with bilateral normal-tension glaucoma (NTG) or hightension glaucoma were consecutively enrolled. A questionnaire to determine the preferred sleeping position was administered to each patient. Asymmetric VF loss was defined as a difference in mean deviation between the 2 eyes of at least 2 dB. According to these values, the better eye and worse eye were defined. Among the patients with asymmetric VF loss, the numbers preferring the worse eye–dependent lateral decubitus position and the better eye–dependent lateral decubitus position were compared. RESULTS: Among the enrolled patients, 309 (60.6%) with NTG and 121 (66.5%) with high-tension glaucoma had asymmetric VF between the 2 eyes. Among the 309 NTG patients, 100 (32.4%) preferred the lateral decubitus position. Of these, 66 (66.0%) preferred the worse eye–dependent lateral decubitus position (P [ .001). Among the 121 high-tension glaucoma patients, 32 (26.4%) preferred the lateral decubitus position, and of these, 23 (71.9%) preferred the worse eye–dependent lateral decubitus position (P [ .013). CONCLUSION: Our results suggest that the sleep position habitually preferred by glaucoma patients may be associated with greater VF loss. (Am J Ophthalmol 2014;157:739–745. Ó 2014 by Elsevier Inc. All rights reserved.)
Accepted for publication Dec 10, 2013. From the Department of Ophthalmology, Chungnam National University Hospital, Daejeon, South Korea (K.N.K.); Department of Ophthalmology, Seoul National University Hospital, Seoul, South Korea (J.W.J., K.H.P., D.M.K.); Department of Ophthalmology, Seoul National University College of Medicine, Seoul, South Korea (K.H.P., D.M.K.); Einhorn Clinical Research Center, New York Eye and Ear Infirmary, New York, New York (R.R.); and Department of Ophthalmology, New York Medical College, Valhalla, New York (R.R.). Inquiries to Ki Ho Park, Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul 110-744, South Korea; e-mail: kihopark@ snu.ac.kr 0002-9394/$36.00 http://dx.doi.org/10.1016/j.ajo.2013.12.016
Ó
2014 BY
I
NTRAOCULAR PRESSURE (IOP) REDUCTION CAN SLOW
the progression of visual field (VF) damage in glaucoma patients; however, despite apparently effective IOP control, some patients continue to progress.1 It is well known that IOP is higher in the supine position than when sitting.2–6 Moreover, the extent of IOP elevation from the sitting to the supine position is greater in primary open-angle glaucoma (OAG), ocular hypertension, and normal-tension glaucoma (NTG) than in normal subjects.6–8 In prospective studies of the effect of the lateral decubitus position on IOP in healthy volunteers, IOP in the lateral decubitus position was consistently higher in the dependent eye (the lower-positioned eye; eg, the right eye in the right lateral decubitus position) than in the nondependent eye (the upper-positioned eye; eg, the left eye in the right lateral decubitus position).9–11 Further, IOP in the dependent eye in the lateral decubitus position was consistently higher than that in the sitting or supine position.9–12 In 2 recent studies on OAG patients, IOP in the lateral decubitus position was consistently higher in the dependent eye than in the fellow eye, and dependent-eye IOP was consistently higher in the lateral decubitus position than in the sitting or supine position.13,14 People generally spend between one-quarter and onethird of their lives sleeping. During sleep, body position varies between the supine position and the lateral decubitus position, often more on 1 side than the other. Thus IOP elevation related to the lateral decubitus position might play a role in glaucoma progression.13,15,16 On the basis of questionnaire data, we previously suggested that the lateral decubitus position habitually preferred by glaucoma patients might be associated with asymmetric VF damage; however, the number of respondents was relatively small.13 In the present study, examining a large subject group, we verified our hypothesis on the association between the preferred sleeping position and asymmetric VF loss between eyes.
METHODS THIS
RETROSPECTIVE
CROSS-SECTIONAL
STUDY
WAS
approved by the Institutional Review Board of Seoul National
ELSEVIER INC. ALL
RIGHTS RESERVED.
739
University Hospital and was conducted in accordance with the relevant Declaration of Helsinki specifications. Patients with treated bilateral OAG and IOPs in the teens during office hours were consecutively enrolled from the Glaucoma Clinic of Seoul National University Hospital from September 1, 2012 to December 31, 2012. The criteria for a diagnosis of OAG were typical glaucomatous optic disc change, reproducible glaucomatous VF defect, and open angles on gonioscopy. Glaucomatous optic disc changes were characterized as focal or diffuse neuroretinal rim thinning or as localized notching with correlating VF changes. Glaucomatous VF defects were confirmed if 2 of the following 3 criteria were met: the presence of a cluster of 3 points on a pattern deviation probability plot with P < 5%, 1 of which had P < 1%; a pattern standard deviation (PSD) with P < 5%; or a glaucoma hemifield test result outside normal limits. The patients were divided into 2 subgroups according to the baseline IOP without medication. Some patients treated when referred to us were removed from all ocular hypotensive therapy. Required washout periods prior to measurement of the baseline IOP were 5 days for carbonic anhydrase inhibitors, 2 weeks for adrenergic agonists, and 4 weeks for beta-adrenergic receptor antagonists and prostaglandin analogues. On the other hand, other referred patients, because of uncontrolled IOP despite maximally tolerable medical therapy with or without oral hypotensive agents, were not removed from hypotensive therapy but were excluded from this study. Untreated baseline IOP was measured by Goldmann applanation tonometry at different times during daylight hours on at least 3 visits: _21 mm NTG was diagnosed if all of the readings were < Hg, and high-tension glaucoma was diagnosed in cases where any of the readings were >21 mm Hg. The exclusion criteria were as follows: eyes having poor reliability on VF analysis (>20% fixation loss; >15% false-positive or falsenegative answers); any media opacities or diseases that could influence the digital optic disc photograph and redfree photograph; 20/40 or worse best-corrected visual acuity; high myopia (>6.0 diopters); or any diseases that might secondarily influence IOP or the VF. A questionnaire on the preferred sleeping position was administered to each of the subjects and their answers recorded by a single observer masked to the ophthalmic examination results. The following questions were asked: (1) Do you have a preferred lying position when you are sleeping? a) YES, b) NO; (2) If your answer to ‘‘Question 1’’ is a) YES, which body position do you prefer? a) right lateral decubitus position (lying on your right side), b) left lateral decubitus position (lying on your left side), c) supine position (lying on your back), d) prone position (lying on your stomach), e) both lateral decubitus positions (lying on your right and left side, alternately). Because we could not know which lateral decubitus position was the dominant lateral decubitus side, the answer ‘‘e) both lateral decubitus positions’’ to ‘‘Question 2’’ was regarded as ‘‘no preference.’’ 740
The electronic medical records, VF test results, and digital optic disc photographs of the enrolled patients were retrospectively reviewed. All patients were examined regularly at intervals of 3-6 months. IOP was assessed by Goldmann applanation tonometry. Digital optic disc photography (TRCSS2; Topcon, Inc, Tokyo, Japan) and VF analysis using the Swedish interactive thresholding algorithm (SITA) of 30-2 perimetry (Humphrey Field Analyzer II; Carl Zeiss Meditec, Dublin, California, USA) were evaluated also at 3- to 6-month intervals. The association between the preferred sleeping position and asymmetric VF loss in the OAG patients, NTG and high-tension glaucoma, was analyzed. Asymmetric VF loss was defined as a difference in mean deviation (MD) of at least 2 dB between the eyes.17,18 For all patients with asymmetric VF loss, the better eye and worse eye were defined based on the MD value determined in the VF test performed within 6 months of the enrollment of each patient. All statistical analyses were performed using SPSS version 18.0 (SPSS Inc, Chicago, Illinois, USA). The subjects’ demographics were compared according to the baseline IOP, mean IOP, spherical equivalent, axial length, central corneal thickness, and result of VF testing using paired t tests and independent t tests. x2 t tests and 1sample x2 tests were used to analyze the results of the preferred sleeping position questionnaire. A P < .05 value was considered to represent a significant difference.
RESULTS A TOTAL OF 692 SUBJECTS WITH OAG (367 MEN, 325 WOMEN;
mean age: 60.6 6 13.5 years; range: 19-91 years) met the criteria for inclusion in this study. There were 510 NTG and 182 high-tension glaucoma patients. Table 1 provides a demographic summary. As is apparent, there was a significant mean IOP difference between the right and left eyes of the high-tension glaucoma patients (15.3 6 3.2 mm Hg and 14.7 6 3.0 mm Hg, respectively; P ¼ .009). The VF test results showed no such difference. Table 2 summarizes the demographics of the OAG patients with asymmetric VF loss. Of the enrolled 692 patients, 430 (62.1%) had asymmetric VF loss.The baseline IOP of the worse eye was 16.7 6 5.4 mm Hg and that of the better eye was 16.0 6 4.4 mm Hg (P < .001). There was a significant difference in MD value between the worse eye and better eye (11.3 6 7.4 dB and 4.8 6 5.7 dB, respectively; P < .001). Table 3 summarizes the demographics of the NTG and high-tension glaucoma patients with asymmetric VF loss. The numbers of patients with asymmetric VF defect were 309 (of 510) NTG patients (60.6%) and 121 (of 182) high-tension glaucoma patients (66.5%) (P ¼ .159; x2 test). The number of NTG patients having the worse VF in the left eye was 175, and in the right eye, 134 (P ¼ .020;
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TABLE 1. Demographics of the Open-Angle Glaucoma Patients Normal-Tension Glaucoma (n ¼ 510)
High-Tension Glaucoma (n ¼ 182)
P Value
60.3 6 12.9 251 (49.2%)
61.6 6 14.8 116 (63.7%)
.001a .001b
Age, y Sex (male), n (%)
Mean IOP (mm Hg) SE (diopter) Axial length (mm) CCT (mm) Humphrey visual field MD (dB) PSD (dB) VFI (%)
Right Eye
Left Eye
P Valuec
Right Eye
Left Eye
P Valuec
13.0 6 2.3 1.3 6 3.2 24.6 6 1.7 529.8 6 35.8
12.9 6 2.3 1.2 6 3.0 24.6 6 1.7 530.6 6 34.8
.275 .616 .374 .332
15.3 6 3.2 1.0 6 2.8 25.0 6 1.8 539.4 6 41.8
14.7 6 3.0 0.9 6 2.8 25.0 6 1.8 539.4 6 40.4
.009 .194 .210 .996
5.3 6 6.5 6.3 6 4.7 85.5 6 19.3
5.8 6 6.5 6.3 6 4.6 85.2 6 19.0
.051 .864 .751
10.2 6 9.0 7.6 6 4.8 73.3 6 28.4
10.0 6 9.2 7.4 6 6.7 73.3 6 30.0
.764 .814 .990
CCT ¼ central corneal thickness; IOP ¼ intraocular pressure; MD ¼ mean deviation; PSD ¼ pattern standard deviation; SE ¼ spherical equivalent; VFI ¼ visual field index. Data are mean 6 SD unless indicated. a Independent t test. b 2 x test. c Paired t test; comparison between right eye and left eye in normal-tension glaucoma patients and high-tension glaucoma patients, respectively.
TABLE 2. Demographics of the Open-Angle Glaucoma Patients With Asymmetric Visual Field Loss Open-Angle Glaucoma (n ¼ 430)
60.6 6 13.6 229 (53.3%) 194 (45.1%)
Age, y Sex (male), n (%) Right laterality of worse eye, n (%)
Baseline IOP (mm Hg) Mean IOP (mm Hg) Spherical equivalent (diopter) Axial length (mm) Central corneal thickness (mm) Humphrey visual field MD (dB) PSD (dB) VFI (%)
Worse Eye
Better Eye
P Valuea
16.7 6 5.4 13.4 6 2.8 1.4 6 3.1 24.8 6 1.7 530.9 6 35.8
16.0 6 4.4 13.5 6 2.6 1.3 6 2.8 24.7 6 1.7 533.1 6 35.8
<.001 .341 .061 .051 .057
11.3 6 7.4 10.2 6 5.1 68.9 6 24.4
4.8 6 5.7 5.4 6 4.4 88.4 6 16.6
<.001 <.001 <.001
IOP ¼ intraocular pressure; MD ¼ mean deviation; PSD ¼ pattern standard deviation; VFI ¼ visual field index. Data are mean 6 SD unless indicated. Asymmetric visual field loss was defined as a difference in mean deviation of at least 2 dB between the eyes. Worse eye and better eye were defined based on the mean deviation value determined in the Humphrey visual field test. a Paired t test.
1-sample x2 test). In contrast, the number of high-tension glaucoma patients having the worse VF in the left eye was 61, and in the right eye, 60, with no significant difference (P ¼ .928; 1-sample x2 test). The baseline IOPs of the worse eye and better eye among the NTG patients were 14.9 6 2.9 mm Hg and 14.8 6 2.8 mm Hg, respectively VOL. 157, NO. 3
(P ¼ .230); but among the high-tension glaucoma patients, the baseline IOP of the worse eye was significantly higher than that of the better eye (24.8 6 6.2 mm Hg and 22.1 6 4.8 mm Hg, respectively; P ¼ .003). Table 4 lists the questionnaire data on the preferred sleeping position. Of the 510 NTG and 182 high-tension
PREFERRED SLEEPING POSITION AND ASYMMETRIC VISUAL FIELD LOSS
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TABLE 3. Demographics of the Normal-Tension Glaucoma Patients or High-Tension Glaucoma Patients With Asymmetric Visual Field Loss Normal-Tension Glaucoma (n ¼ 309)
High-Tension Glaucoma (n ¼ 121)
P Value
59.9 6 13.11 153 (49.5%) 134 (43.4%)
62.6 6 14.6 76 (62.8%) 60 (49.6%)
.067a .013b .244b
Age (y) Sex (male), n (%) Right laterality of worse eye, n (%)
Baseline IOP (mm Hg) Mean IOP (mm Hg) Spherical equivalent (diopter) Axial length (mm) CCT (mm) Humphrey visual field MD (dB) PSD (dB) VFI (%)
Worse Eye
Better Eye
14.9 6 2.9 12.9 6 2.2 1.5 6 3.1 24.7 6 1.7 531.3 6 33.8
14.8 6 2.8 13.0 6 2.2 1.4 6 2.8 24.7 6 1.6 532.7 6 35.2
9.8 6 6.4 10.0 6 4.1 73.2 6 20.8
3.8 6 4.9 4.9 6 4.2 90.9 6 13.7
P Valuec
P Valuec
Worse Eye
Better Eye
.230 .417 .074 .510 .310
24.8 6 6.2 14.8 6 3.5 1.0 6 3.0 25.0 6 1.9 530.5 6 45.4
22.1 6 4.8 14.9 6 3.0 0.9 6 2.7 24.9 6 1.8 533.9 6 38.7
.003 .739 .060 .501 .180
<.001 <.001 <.001
17.0 6 8.5 10.6 6 7.1 52.6 6 29.2
7.2 6 6.6 6.8 6 4.7 82.2 6 20.8
<.001 <.001 <.001
CCT ¼ central corneal thickness; IOP ¼ intraocular pressure; MD ¼ mean deviation; PSD ¼ pattern standard deviation; VFI ¼ visual field index. Data are mean 6 SD unless indicated. Asymmetric visual field loss was defined as a difference in mean deviation of at least 2 dB between the eyes. Worse eye and better eye were defined based on the mean deviation value determined in the Humphrey visual field test. a Independent t test. b 2 x test. c Paired t test, comparison between right eye and left eye in normal-tension glaucoma patients and high-tension glaucoma patients, respectively.
glaucoma patients, 149 (29.2%) and 45 (24.7%) preferred the right or left lateral decubitus position, respectively. Among the entire open-angle glaucoma patient group or between the NTG and high-tension glaucoma subgroups, the number of patients preferring the worse eye–dependent lateral decubitus position was 89 (45.9%), 66 (44.3%), and 23 (51.1%), respectively (P < .001, P ¼ .006, and P ¼ .031, respectively; 1-sample x2 test). Table 5 shows the questionnaire results on the preferred sleeping position for patients with asymmetric VF defect. For the 430 OAG subjects, 132 (30.7%) preferred the lateral decubitus position, among whom 89 (67.4%) preferred the worse eye–dependent lateral decubitus position. In the subgroup analysis results, 100 of the 309 NTG patients (32.4%) preferred the lateral decubitus position, 66 of whom (66.0%) preferred the worse eye–dependent lateral decubitus position, and 32 (26.4%) of the 121 high-tension glaucoma patients preferred the lateral decubitus position, 23 (71.9%) of whom preferred the worse eye–dependent lateral decubitus position. In all 3 groups, the number of patients preferring the worse eye–dependent lateral decubitus position was significantly larger than those preferring the better eye–dependent lateral decubitus position (P < .001, P ¼ .001, P ¼ .013, respectively; 1-sample x2 test). There was no significant difference between the NTG and high-tension glaucoma patients with asymmetric VF loss in the preferred sleeping position (P ¼ .537). 742
DISCUSSION IN OUR PREVIOUS STUDY,13 WE FOUND THAT 75.5% OF
enrolled patients preferred the lateral decubitus position, of whom 75.7% preferred the worse eye–dependent lateral decubitus position, compared with only 24.3% who preferred the better eye–dependent lateral decubitus position (P ¼ .002; 1-sample x2 test). We hypothesized that asymmetric glaucoma in patients who had wellcontrolled IOP in the sitting position could be associated with the preferred lying position during sleep. Previous studies on positional IOP have made 2 important findings: (1) IOP is higher in the supine position than in the sitting position; and (2) the magnitude of IOP elevation is greater in glaucoma patients than in normal subjects.2–8 Tsukahara and associates5 reported that such IOP elevation was more remarkable in patients with NTG than in those with primary open-angle glaucoma or normal subjects. Liu and associates17,18 and Buys and associates19 found that for both glaucoma patients and normal subjects, nocturnal IOP measured in the supine position was significantly higher than in the sitting position. Kiuchi and associates20 found that the MD slope in NTG patients correlated with IOP elevation caused by the postural change (correlation coefficient: r ¼ 0.682; P < .001), but that there was no significant correlation between MD slope and sitting IOP (correlation coefficient:
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TABLE 4. Results of the Survey on Preferred Sleeping Position of the Open-Angle Glaucoma Patients
Preferred Lying Position
Open-Angle Glaucoma, n (%) (N ¼ 692)
Normal-Tension Glaucoma, n (%) (N ¼ 510)
High-Tension Glaucoma, n (%) (N ¼ 182)
No preferred lying position Right LDP Left LDP Supine Prone Both LDP
184 (26.6) 95 (13.7) 99 (14.3) 174 (25.1) 19 (2.7) 121 (17.5)
136 (26.7) 68 (13.3) 81 (15.9) 128 (25.1) 12 (2.3) 85 (16.7)
48 (26.4) 27 (14.8) 18 (9.9) 46 (25.3) 7 (3.8) 36 (19.8)
Asymmetric visual field Worse eye–dependent LDPa Better eye–dependent LDPa Symmetric visual field Right LDP or Left LDP P valueb
Open-Angle Glaucoma,
Normal-Tension Glaucoma,
High-Tension Glaucoma,
n (%) (N ¼ 194)
n (%) (N ¼ 149)
n (%) (N ¼ 45)
89 (45.9)
66 (44.3)
23 (51.1)
43 (22.2) 62 (32.0) <.001
34 (22.8) 49 (32.9) .006
9 (20.0) 13 (28.9) .031
LDP ¼ lateral decubitus position. Preferred lying position ¼ answer the below questionnaire on the preferred lying position during sleep, Asymmetric visual field loss was defined as a difference in mean deviation of at least 2 dB between the eyes. Worse eye and better eye were defined based on the mean deviation value determined in the Humphrey visual field test. a According to the result of the Humphrey visual field test, right LDP and left LDP were converted into worse eye–dependent LDP or better eye–dependent LDP. b One sample x2 test.
r ¼ 0.172; P ¼ .188). These results suggest that glaucoma can progress when patients are in a lying position during sleep. Several assumptions have been made with respect to the mechanisms of IOP response to postural change. The most likely mechanism is the rise of episcleral venous pressure in the supine position.21–23 Krieglstein and associates23 suggested that IOP rise is correlated with changes in episcleral venous pressure and ophthalmic arterial pressure. Another possible mechanism involves alterations in the rate of uveoscleral outflow owing to increased choroidal blood volume.24 There should be a possibility that a reduced perfusion of the optic nerve could be a related mechanism. However, it may be mainly through the elevated intraocular pressure, because the mean ophthalmic arterial pressure may increase as well in the dependent eye in the lateral decubitus position because the level of the eyeball is lower than in the supine position with reference to the level of the heart.19 Previous studies on sleep positions have shown that with advancing age, the preference for the lateral decubitus position and its duration increases.25 In the present, large-cohort study, 67.1% of the NTG patients who preferred the lateral decubitus position (right or left) had asymmetric VF loss (Table 4). Of these patients, the number having the worse VF in the dependent eye, in their preferred lateral decubitus position, was 66.0%, and in the nondependent eye, only 34.0% (P ¼ .001, Table 5). Thus, we suspect that the preferred sleeping position, especially the lateral decubitus position, has effects on the VOL. 157, NO. 3
asymmetry of glaucomatous VF progression in NTG patients. On the other hand, there is a possibility that the contribution of the lateral decubitus position in hightension glaucoma may differ from that in NTG. In patients participating in the Ocular Hypertension Treatment Study, even a 1 mm Hg difference in IOP between fellow eyes was associated with an increase in the risk of developing a glaucomatous VF defect,26 unlike NTG patients examined in the Low-pressure Glaucoma Treatment Study.27 In the present investigation, although the number of high-tension glaucoma patients preferring the worse eye–dependent lateral decubitus position was significantly greater than those preferring the better eye–dependent lateral decubitus position (71.9% vs 28.1%, P ¼ .013), the baseline IOP of the worse eye was higher than that of the better eye (24.8 6 6.2 mm Hg vs 22.1 6 4.8 mm Hg, P ¼ .003). Even though the differences in the mean values of the axial length and central corneal thickness showed borderline significance between the worse and better eyes in OAG patients with asymmetric VF loss (Table 2), these differences were very small (axial length, 24.8 mm vs 24.7 mm, respectively; and central corneal thickness, 530.9 mm vs 533.1 mm, respectively). Neither were the differences significant in NTG or hightension glaucoma patients (Table 3). It is well recognized that IOP exists on a continuum, and that dividing OAG into NTG and high-tension glaucoma by using baseline IOPs of 21 and 22 mm Hg is arbitrary. However, we have used the terms NTG and high-tension glaucoma
PREFERRED SLEEPING POSITION AND ASYMMETRIC VISUAL FIELD LOSS
743
TABLE 5. Results of the Survey on Preferred Sleeping Position of the Open-Angle Glaucoma Patients With Asymmetric Visual Field Loss
Preferred Lying Position
Open-Angle Glaucoma, n (%) (N ¼ 430)
Normal-Tension Glaucoma, n (%) (N ¼ 309)
High-Tension Glaucoma, n (%) (N ¼ 121)
No preferred lying position Worse eye–dependent LDP Better eye–dependent LDP Supine Prone Both LDP
120 (28.0) 89 (20.7) 43 (10.0) 73 (17.0) 12 (2.8) 93 (21.6)
92 (29.8) 66 (21.4) 34 (11.0) 63 (20.4) 6 (1.9) 48 (15.5)
28 (23.1) 23 (19.0) 9 (7.4) 30 (24.8) 6 (5.0) 25 (20.7)
Open-Angle Glaucoma, n (%) (N ¼ 132)
Normal-Tension Glaucoma, n (%) (N ¼ 100)
High-Tension Glaucoma, n (%) (N ¼ 32)
89 (67.4) 43 (32.6) <.001
66 (66.0) 34 (34.0) .001
23 (71.9) 9 (28.1) .013
Worse eye–dependent LDP Better eye–dependent LDP P valueb
P Valuea
.537
LDP ¼ lateral decubitus position. Preferred lying position ¼ answer the below questionnaire on the preferred lying position during sleep, According to the result of the Humphrey visual field test, right LDP and left LDP were converted into worse eye-dependent LDP or better eye-dependent LDP. Asymmetric visual field loss was defined as a difference in mean deviation of at least 2 dB between the eyes. Worse eye and better eye were defined based on the mean deviation value determined in the Humphrey visual field test. a 2 x test, comparison between normal-tension glaucoma patients and high-tension glaucoma patients. b One-sample x2 test.
merely for the purpose of grouping patients in order to look for differences. The limitation of this study is that the preferred sleeping position results were based on a questionnaire; collection of more exact and reliable data using video recording during sleep is warranted. Another limitation is the retrospective and cross-sectional nature of our study; a further study with
a prospective design is required to overcome this limitation. In conclusion, results of the present study strongly suggest that the sleep position habitually preferred by OAG patients may be associated with greater VF loss. In order to confirm our speculation, a prospective, long-term follow-up study will be necessary.
ALL AUTHORS HAVE COMPLETED AND SUBMITTED THE ICMJE FORM FOR DISCLOSURE OF POTENTIAL CONFLICTS OF INTEREST and none were reported. Robert Ritch is supported in part by the Joseph and Geraldine LaMotta Research Fund of the New York Glaucoma Research Institute, New York. None of the other authors have any funding/support to disclose. Contributions of authors: design of study (K.N.K., K.H.P.); data collection (K.N.K., J.W.J.); analysis and interpretation of data (K.N.K., K.H.P., D.M.K., R.R.); writing of article (K.N.K.); critical revision of article (K.N.K., K.H.P., R.R., J.W.J., D.M.K.); and final approval of article (K.N.K., J.W.J., K.H.P., D.M.K., R.R.).
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9. Malihi M, Sit AJ. Effect of head and body position on intraocular pressure. Ophthalmology 2012;119(5):987–991. 10. Lee JY, Yoo C, Jung JH, Hwang YH, Kim YY. The effect of lateral decubitus position on intraocular pressure in healthy young subjects. Acta Ophthalmol 2012;90(1):e68–e72. 11. Lee TE, Yoo C, Kim YY. Effects of different sleeping postures on intraocular pressure and ocular perfusion pressure in healthy young subjects. Ophthalmology 2013;120(8):1565–1570. 12. Wong MH, Lai AH, Singh M, Chew PT. Sleeping posture and intraocular pressure. Singapore Med J 2013;54(3):146–148. 13. Kim KN, Jeoung JW, Park KH, Lee DS, Kim DM. Effect of lateral decubitus position on intraocular pressure in glaucoma patients with asymmetric visual field loss. Ophthalmology 2013;120(4):731–735. 14. Lee JY, Yoo C, Kim YY. The effect of lateral decubitus position on intraocular pressure in patients with untreated openangle glaucoma. Am J Ophthalmol 2013;155(2):329–335. 15. Liu JH, Bouligny RP, Kripke DF, Weinreb RN. Nocturnal elevation of intraocular pressure is detectable in the sitting position. Invest Ophthalmol Vis Sci 2003;44:4439–4442. 16. Noe¨l C, Kabo AM, Romanet JP, Montmayeur A, Buguet A. Twenty-four-hour time course of intraocular pressure in healthy and glaucomatous Africans: relation to sleep patterns. Ophthalmology 2001;108(1):139–144. 17. Liu JH, Kripke DF, Hoffman RE, et al. Elevation of human intraocular pressure at night under moderate illumination. Invest Ophthalmol Vis Sci 1999;40(10):2439–2442. 18. Liu JH, Kripke DF, Twa MD, et al. Twenty-four-hour pattern of intraocular pressure in the aging population. Invest Ophthalmol Vis Sci 1999;40:2912–2917.
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19. Buys YM, Alasbali T, Jin YP, et al. Effect of sleeping in a head-up position on intraocular pressure in patients with glaucoma. Ophthalmology 2010;117(7):1348–1351. 20. Kiuchi T, Motoyama Y, Oshika T. Relationship of progression of visual field damage to postural changes in intraocular pressure in patients with normal-tension glaucoma. Ophthalmology 2006;113(12):2150–2155. 21. Friberg TR, Sanborn G, Weinreb RN. Intraocular and episcleral venous pressure increase during inverted posture. Am J Ophthalmol 1987;103(4):523–526. 22. Sultan M, Blondeau P. Episcleral venous pressure in younger and older subjects in the sitting and supine positions. J Glaucoma 2003;12(4):370–373. 23. Krieglstein GK, Waller WK, Leydhecker W. The vascular basis of the positional influence of the intraocular pressure. Albrecht Von Graefes Arch Klin Exp Ophthalmol 1978;206(2): 99–106. 24. Longo A, Geiser MH, Riva CE. Posture changes and subfoveal choroidal blood flow. Invest Ophthalmol Vis Sci 2004; 45(2):546–551. 25. De Koninck J, Lorrain D, Gagnon P. Sleep positions and position shifts in five age groups: an ontogenetic picture. Sleep 1992;15(2):143–149. 26. Levine RA, Demirel S, Fan J, et al. Asymmetries and visual field summaries as predictors of glaucoma in the ocular hypertension treatment study. Invest Ophthalmol Vis Sci 2006;47(9): 3896–3903. 27. Greenfield DS, Liebmann JM, Ritch R, et al. Visual field and intraocular pressure asymmetry in the low-pressure glaucoma treatment study. Ophthalmology 2007;114(3):460–465.
PREFERRED SLEEPING POSITION AND ASYMMETRIC VISUAL FIELD LOSS
745
To investigate the relationship between preferred sleeping position and asymmetric visual field (VF) loss in open-angle glaucoma (OAG) patients. DESIGN: Retrospective, cross-sectional study. METHODS: Six hundred and ninety-two (692) patients with bilateral normal-tension glaucoma (NTG) or hightension glaucoma were consecutively enrolled. A questionnaire to determine the preferred sleeping position was administered to each patient. Asymmetric VF loss was defined as a difference in mean deviation between the 2 eyes of at least 2 dB. According to these values, the better eye and worse eye were defined. Among the patients with asymmetric VF loss, the numbers preferring the worse eye–dependent lateral decubitus position and the better eye–dependent lateral decubitus position were compared. RESULTS: Among the enrolled patients, 309 (60.6%) with NTG and 121 (66.5%) with high-tension glaucoma had asymmetric VF between the 2 eyes. Among the 309 NTG patients, 100 (32.4%) preferred the lateral decubitus position. Of these, 66 (66.0%) preferred the worse eye–dependent lateral decubitus position (P [ .001). Among the 121 high-tension glaucoma patients, 32 (26.4%) preferred the lateral decubitus position, and of these, 23 (71.9%) preferred the worse eye–dependent lateral decubitus position (P [ .013). CONCLUSION: Our results suggest that the sleep position habitually preferred by glaucoma patients may be associated with greater VF loss. (Am J Ophthalmol 2014;157:739–745. Ó 2014 by Elsevier Inc. All rights reserved.)
Accepted for publication Dec 10, 2013. From the Department of Ophthalmology, Chungnam National University Hospital, Daejeon, South Korea (K.N.K.); Department of Ophthalmology, Seoul National University Hospital, Seoul, South Korea (J.W.J., K.H.P., D.M.K.); Department of Ophthalmology, Seoul National University College of Medicine, Seoul, South Korea (K.H.P., D.M.K.); Einhorn Clinical Research Center, New York Eye and Ear Infirmary, New York, New York (R.R.); and Department of Ophthalmology, New York Medical College, Valhalla, New York (R.R.). Inquiries to Ki Ho Park, Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul 110-744, South Korea; e-mail: kihopark@ snu.ac.kr 0002-9394/$36.00 http://dx.doi.org/10.1016/j.ajo.2013.12.016
Ó
2014 BY
I
NTRAOCULAR PRESSURE (IOP) REDUCTION CAN SLOW
the progression of visual field (VF) damage in glaucoma patients; however, despite apparently effective IOP control, some patients continue to progress.1 It is well known that IOP is higher in the supine position than when sitting.2–6 Moreover, the extent of IOP elevation from the sitting to the supine position is greater in primary open-angle glaucoma (OAG), ocular hypertension, and normal-tension glaucoma (NTG) than in normal subjects.6–8 In prospective studies of the effect of the lateral decubitus position on IOP in healthy volunteers, IOP in the lateral decubitus position was consistently higher in the dependent eye (the lower-positioned eye; eg, the right eye in the right lateral decubitus position) than in the nondependent eye (the upper-positioned eye; eg, the left eye in the right lateral decubitus position).9–11 Further, IOP in the dependent eye in the lateral decubitus position was consistently higher than that in the sitting or supine position.9–12 In 2 recent studies on OAG patients, IOP in the lateral decubitus position was consistently higher in the dependent eye than in the fellow eye, and dependent-eye IOP was consistently higher in the lateral decubitus position than in the sitting or supine position.13,14 People generally spend between one-quarter and onethird of their lives sleeping. During sleep, body position varies between the supine position and the lateral decubitus position, often more on 1 side than the other. Thus IOP elevation related to the lateral decubitus position might play a role in glaucoma progression.13,15,16 On the basis of questionnaire data, we previously suggested that the lateral decubitus position habitually preferred by glaucoma patients might be associated with asymmetric VF damage; however, the number of respondents was relatively small.13 In the present study, examining a large subject group, we verified our hypothesis on the association between the preferred sleeping position and asymmetric VF loss between eyes.
METHODS THIS
RETROSPECTIVE
CROSS-SECTIONAL
STUDY
WAS
approved by the Institutional Review Board of Seoul National
ELSEVIER INC. ALL
RIGHTS RESERVED.
739
University Hospital and was conducted in accordance with the relevant Declaration of Helsinki specifications. Patients with treated bilateral OAG and IOPs in the teens during office hours were consecutively enrolled from the Glaucoma Clinic of Seoul National University Hospital from September 1, 2012 to December 31, 2012. The criteria for a diagnosis of OAG were typical glaucomatous optic disc change, reproducible glaucomatous VF defect, and open angles on gonioscopy. Glaucomatous optic disc changes were characterized as focal or diffuse neuroretinal rim thinning or as localized notching with correlating VF changes. Glaucomatous VF defects were confirmed if 2 of the following 3 criteria were met: the presence of a cluster of 3 points on a pattern deviation probability plot with P < 5%, 1 of which had P < 1%; a pattern standard deviation (PSD) with P < 5%; or a glaucoma hemifield test result outside normal limits. The patients were divided into 2 subgroups according to the baseline IOP without medication. Some patients treated when referred to us were removed from all ocular hypotensive therapy. Required washout periods prior to measurement of the baseline IOP were 5 days for carbonic anhydrase inhibitors, 2 weeks for adrenergic agonists, and 4 weeks for beta-adrenergic receptor antagonists and prostaglandin analogues. On the other hand, other referred patients, because of uncontrolled IOP despite maximally tolerable medical therapy with or without oral hypotensive agents, were not removed from hypotensive therapy but were excluded from this study. Untreated baseline IOP was measured by Goldmann applanation tonometry at different times during daylight hours on at least 3 visits: _21 mm NTG was diagnosed if all of the readings were < Hg, and high-tension glaucoma was diagnosed in cases where any of the readings were >21 mm Hg. The exclusion criteria were as follows: eyes having poor reliability on VF analysis (>20% fixation loss; >15% false-positive or falsenegative answers); any media opacities or diseases that could influence the digital optic disc photograph and redfree photograph; 20/40 or worse best-corrected visual acuity; high myopia (>6.0 diopters); or any diseases that might secondarily influence IOP or the VF. A questionnaire on the preferred sleeping position was administered to each of the subjects and their answers recorded by a single observer masked to the ophthalmic examination results. The following questions were asked: (1) Do you have a preferred lying position when you are sleeping? a) YES, b) NO; (2) If your answer to ‘‘Question 1’’ is a) YES, which body position do you prefer? a) right lateral decubitus position (lying on your right side), b) left lateral decubitus position (lying on your left side), c) supine position (lying on your back), d) prone position (lying on your stomach), e) both lateral decubitus positions (lying on your right and left side, alternately). Because we could not know which lateral decubitus position was the dominant lateral decubitus side, the answer ‘‘e) both lateral decubitus positions’’ to ‘‘Question 2’’ was regarded as ‘‘no preference.’’ 740
The electronic medical records, VF test results, and digital optic disc photographs of the enrolled patients were retrospectively reviewed. All patients were examined regularly at intervals of 3-6 months. IOP was assessed by Goldmann applanation tonometry. Digital optic disc photography (TRCSS2; Topcon, Inc, Tokyo, Japan) and VF analysis using the Swedish interactive thresholding algorithm (SITA) of 30-2 perimetry (Humphrey Field Analyzer II; Carl Zeiss Meditec, Dublin, California, USA) were evaluated also at 3- to 6-month intervals. The association between the preferred sleeping position and asymmetric VF loss in the OAG patients, NTG and high-tension glaucoma, was analyzed. Asymmetric VF loss was defined as a difference in mean deviation (MD) of at least 2 dB between the eyes.17,18 For all patients with asymmetric VF loss, the better eye and worse eye were defined based on the MD value determined in the VF test performed within 6 months of the enrollment of each patient. All statistical analyses were performed using SPSS version 18.0 (SPSS Inc, Chicago, Illinois, USA). The subjects’ demographics were compared according to the baseline IOP, mean IOP, spherical equivalent, axial length, central corneal thickness, and result of VF testing using paired t tests and independent t tests. x2 t tests and 1sample x2 tests were used to analyze the results of the preferred sleeping position questionnaire. A P < .05 value was considered to represent a significant difference.
RESULTS A TOTAL OF 692 SUBJECTS WITH OAG (367 MEN, 325 WOMEN;
mean age: 60.6 6 13.5 years; range: 19-91 years) met the criteria for inclusion in this study. There were 510 NTG and 182 high-tension glaucoma patients. Table 1 provides a demographic summary. As is apparent, there was a significant mean IOP difference between the right and left eyes of the high-tension glaucoma patients (15.3 6 3.2 mm Hg and 14.7 6 3.0 mm Hg, respectively; P ¼ .009). The VF test results showed no such difference. Table 2 summarizes the demographics of the OAG patients with asymmetric VF loss. Of the enrolled 692 patients, 430 (62.1%) had asymmetric VF loss.The baseline IOP of the worse eye was 16.7 6 5.4 mm Hg and that of the better eye was 16.0 6 4.4 mm Hg (P < .001). There was a significant difference in MD value between the worse eye and better eye (11.3 6 7.4 dB and 4.8 6 5.7 dB, respectively; P < .001). Table 3 summarizes the demographics of the NTG and high-tension glaucoma patients with asymmetric VF loss. The numbers of patients with asymmetric VF defect were 309 (of 510) NTG patients (60.6%) and 121 (of 182) high-tension glaucoma patients (66.5%) (P ¼ .159; x2 test). The number of NTG patients having the worse VF in the left eye was 175, and in the right eye, 134 (P ¼ .020;
AMERICAN JOURNAL OF OPHTHALMOLOGY
MARCH 2014
TABLE 1. Demographics of the Open-Angle Glaucoma Patients Normal-Tension Glaucoma (n ¼ 510)
High-Tension Glaucoma (n ¼ 182)
P Value
60.3 6 12.9 251 (49.2%)
61.6 6 14.8 116 (63.7%)
.001a .001b
Age, y Sex (male), n (%)
Mean IOP (mm Hg) SE (diopter) Axial length (mm) CCT (mm) Humphrey visual field MD (dB) PSD (dB) VFI (%)
Right Eye
Left Eye
P Valuec
Right Eye
Left Eye
P Valuec
13.0 6 2.3 1.3 6 3.2 24.6 6 1.7 529.8 6 35.8
12.9 6 2.3 1.2 6 3.0 24.6 6 1.7 530.6 6 34.8
.275 .616 .374 .332
15.3 6 3.2 1.0 6 2.8 25.0 6 1.8 539.4 6 41.8
14.7 6 3.0 0.9 6 2.8 25.0 6 1.8 539.4 6 40.4
.009 .194 .210 .996
5.3 6 6.5 6.3 6 4.7 85.5 6 19.3
5.8 6 6.5 6.3 6 4.6 85.2 6 19.0
.051 .864 .751
10.2 6 9.0 7.6 6 4.8 73.3 6 28.4
10.0 6 9.2 7.4 6 6.7 73.3 6 30.0
.764 .814 .990
CCT ¼ central corneal thickness; IOP ¼ intraocular pressure; MD ¼ mean deviation; PSD ¼ pattern standard deviation; SE ¼ spherical equivalent; VFI ¼ visual field index. Data are mean 6 SD unless indicated. a Independent t test. b 2 x test. c Paired t test; comparison between right eye and left eye in normal-tension glaucoma patients and high-tension glaucoma patients, respectively.
TABLE 2. Demographics of the Open-Angle Glaucoma Patients With Asymmetric Visual Field Loss Open-Angle Glaucoma (n ¼ 430)
60.6 6 13.6 229 (53.3%) 194 (45.1%)
Age, y Sex (male), n (%) Right laterality of worse eye, n (%)
Baseline IOP (mm Hg) Mean IOP (mm Hg) Spherical equivalent (diopter) Axial length (mm) Central corneal thickness (mm) Humphrey visual field MD (dB) PSD (dB) VFI (%)
Worse Eye
Better Eye
P Valuea
16.7 6 5.4 13.4 6 2.8 1.4 6 3.1 24.8 6 1.7 530.9 6 35.8
16.0 6 4.4 13.5 6 2.6 1.3 6 2.8 24.7 6 1.7 533.1 6 35.8
<.001 .341 .061 .051 .057
11.3 6 7.4 10.2 6 5.1 68.9 6 24.4
4.8 6 5.7 5.4 6 4.4 88.4 6 16.6
<.001 <.001 <.001
IOP ¼ intraocular pressure; MD ¼ mean deviation; PSD ¼ pattern standard deviation; VFI ¼ visual field index. Data are mean 6 SD unless indicated. Asymmetric visual field loss was defined as a difference in mean deviation of at least 2 dB between the eyes. Worse eye and better eye were defined based on the mean deviation value determined in the Humphrey visual field test. a Paired t test.
1-sample x2 test). In contrast, the number of high-tension glaucoma patients having the worse VF in the left eye was 61, and in the right eye, 60, with no significant difference (P ¼ .928; 1-sample x2 test). The baseline IOPs of the worse eye and better eye among the NTG patients were 14.9 6 2.9 mm Hg and 14.8 6 2.8 mm Hg, respectively VOL. 157, NO. 3
(P ¼ .230); but among the high-tension glaucoma patients, the baseline IOP of the worse eye was significantly higher than that of the better eye (24.8 6 6.2 mm Hg and 22.1 6 4.8 mm Hg, respectively; P ¼ .003). Table 4 lists the questionnaire data on the preferred sleeping position. Of the 510 NTG and 182 high-tension
PREFERRED SLEEPING POSITION AND ASYMMETRIC VISUAL FIELD LOSS
741
TABLE 3. Demographics of the Normal-Tension Glaucoma Patients or High-Tension Glaucoma Patients With Asymmetric Visual Field Loss Normal-Tension Glaucoma (n ¼ 309)
High-Tension Glaucoma (n ¼ 121)
P Value
59.9 6 13.11 153 (49.5%) 134 (43.4%)
62.6 6 14.6 76 (62.8%) 60 (49.6%)
.067a .013b .244b
Age (y) Sex (male), n (%) Right laterality of worse eye, n (%)
Baseline IOP (mm Hg) Mean IOP (mm Hg) Spherical equivalent (diopter) Axial length (mm) CCT (mm) Humphrey visual field MD (dB) PSD (dB) VFI (%)
Worse Eye
Better Eye
14.9 6 2.9 12.9 6 2.2 1.5 6 3.1 24.7 6 1.7 531.3 6 33.8
14.8 6 2.8 13.0 6 2.2 1.4 6 2.8 24.7 6 1.6 532.7 6 35.2
9.8 6 6.4 10.0 6 4.1 73.2 6 20.8
3.8 6 4.9 4.9 6 4.2 90.9 6 13.7
P Valuec
P Valuec
Worse Eye
Better Eye
.230 .417 .074 .510 .310
24.8 6 6.2 14.8 6 3.5 1.0 6 3.0 25.0 6 1.9 530.5 6 45.4
22.1 6 4.8 14.9 6 3.0 0.9 6 2.7 24.9 6 1.8 533.9 6 38.7
.003 .739 .060 .501 .180
<.001 <.001 <.001
17.0 6 8.5 10.6 6 7.1 52.6 6 29.2
7.2 6 6.6 6.8 6 4.7 82.2 6 20.8
<.001 <.001 <.001
CCT ¼ central corneal thickness; IOP ¼ intraocular pressure; MD ¼ mean deviation; PSD ¼ pattern standard deviation; VFI ¼ visual field index. Data are mean 6 SD unless indicated. Asymmetric visual field loss was defined as a difference in mean deviation of at least 2 dB between the eyes. Worse eye and better eye were defined based on the mean deviation value determined in the Humphrey visual field test. a Independent t test. b 2 x test. c Paired t test, comparison between right eye and left eye in normal-tension glaucoma patients and high-tension glaucoma patients, respectively.
glaucoma patients, 149 (29.2%) and 45 (24.7%) preferred the right or left lateral decubitus position, respectively. Among the entire open-angle glaucoma patient group or between the NTG and high-tension glaucoma subgroups, the number of patients preferring the worse eye–dependent lateral decubitus position was 89 (45.9%), 66 (44.3%), and 23 (51.1%), respectively (P < .001, P ¼ .006, and P ¼ .031, respectively; 1-sample x2 test). Table 5 shows the questionnaire results on the preferred sleeping position for patients with asymmetric VF defect. For the 430 OAG subjects, 132 (30.7%) preferred the lateral decubitus position, among whom 89 (67.4%) preferred the worse eye–dependent lateral decubitus position. In the subgroup analysis results, 100 of the 309 NTG patients (32.4%) preferred the lateral decubitus position, 66 of whom (66.0%) preferred the worse eye–dependent lateral decubitus position, and 32 (26.4%) of the 121 high-tension glaucoma patients preferred the lateral decubitus position, 23 (71.9%) of whom preferred the worse eye–dependent lateral decubitus position. In all 3 groups, the number of patients preferring the worse eye–dependent lateral decubitus position was significantly larger than those preferring the better eye–dependent lateral decubitus position (P < .001, P ¼ .001, P ¼ .013, respectively; 1-sample x2 test). There was no significant difference between the NTG and high-tension glaucoma patients with asymmetric VF loss in the preferred sleeping position (P ¼ .537). 742
DISCUSSION IN OUR PREVIOUS STUDY,13 WE FOUND THAT 75.5% OF
enrolled patients preferred the lateral decubitus position, of whom 75.7% preferred the worse eye–dependent lateral decubitus position, compared with only 24.3% who preferred the better eye–dependent lateral decubitus position (P ¼ .002; 1-sample x2 test). We hypothesized that asymmetric glaucoma in patients who had wellcontrolled IOP in the sitting position could be associated with the preferred lying position during sleep. Previous studies on positional IOP have made 2 important findings: (1) IOP is higher in the supine position than in the sitting position; and (2) the magnitude of IOP elevation is greater in glaucoma patients than in normal subjects.2–8 Tsukahara and associates5 reported that such IOP elevation was more remarkable in patients with NTG than in those with primary open-angle glaucoma or normal subjects. Liu and associates17,18 and Buys and associates19 found that for both glaucoma patients and normal subjects, nocturnal IOP measured in the supine position was significantly higher than in the sitting position. Kiuchi and associates20 found that the MD slope in NTG patients correlated with IOP elevation caused by the postural change (correlation coefficient: r ¼ 0.682; P < .001), but that there was no significant correlation between MD slope and sitting IOP (correlation coefficient:
AMERICAN JOURNAL OF OPHTHALMOLOGY
MARCH 2014
TABLE 4. Results of the Survey on Preferred Sleeping Position of the Open-Angle Glaucoma Patients
Preferred Lying Position
Open-Angle Glaucoma, n (%) (N ¼ 692)
Normal-Tension Glaucoma, n (%) (N ¼ 510)
High-Tension Glaucoma, n (%) (N ¼ 182)
No preferred lying position Right LDP Left LDP Supine Prone Both LDP
184 (26.6) 95 (13.7) 99 (14.3) 174 (25.1) 19 (2.7) 121 (17.5)
136 (26.7) 68 (13.3) 81 (15.9) 128 (25.1) 12 (2.3) 85 (16.7)
48 (26.4) 27 (14.8) 18 (9.9) 46 (25.3) 7 (3.8) 36 (19.8)
Asymmetric visual field Worse eye–dependent LDPa Better eye–dependent LDPa Symmetric visual field Right LDP or Left LDP P valueb
Open-Angle Glaucoma,
Normal-Tension Glaucoma,
High-Tension Glaucoma,
n (%) (N ¼ 194)
n (%) (N ¼ 149)
n (%) (N ¼ 45)
89 (45.9)
66 (44.3)
23 (51.1)
43 (22.2) 62 (32.0) <.001
34 (22.8) 49 (32.9) .006
9 (20.0) 13 (28.9) .031
LDP ¼ lateral decubitus position. Preferred lying position ¼ answer the below questionnaire on the preferred lying position during sleep, Asymmetric visual field loss was defined as a difference in mean deviation of at least 2 dB between the eyes. Worse eye and better eye were defined based on the mean deviation value determined in the Humphrey visual field test. a According to the result of the Humphrey visual field test, right LDP and left LDP were converted into worse eye–dependent LDP or better eye–dependent LDP. b One sample x2 test.
r ¼ 0.172; P ¼ .188). These results suggest that glaucoma can progress when patients are in a lying position during sleep. Several assumptions have been made with respect to the mechanisms of IOP response to postural change. The most likely mechanism is the rise of episcleral venous pressure in the supine position.21–23 Krieglstein and associates23 suggested that IOP rise is correlated with changes in episcleral venous pressure and ophthalmic arterial pressure. Another possible mechanism involves alterations in the rate of uveoscleral outflow owing to increased choroidal blood volume.24 There should be a possibility that a reduced perfusion of the optic nerve could be a related mechanism. However, it may be mainly through the elevated intraocular pressure, because the mean ophthalmic arterial pressure may increase as well in the dependent eye in the lateral decubitus position because the level of the eyeball is lower than in the supine position with reference to the level of the heart.19 Previous studies on sleep positions have shown that with advancing age, the preference for the lateral decubitus position and its duration increases.25 In the present, large-cohort study, 67.1% of the NTG patients who preferred the lateral decubitus position (right or left) had asymmetric VF loss (Table 4). Of these patients, the number having the worse VF in the dependent eye, in their preferred lateral decubitus position, was 66.0%, and in the nondependent eye, only 34.0% (P ¼ .001, Table 5). Thus, we suspect that the preferred sleeping position, especially the lateral decubitus position, has effects on the VOL. 157, NO. 3
asymmetry of glaucomatous VF progression in NTG patients. On the other hand, there is a possibility that the contribution of the lateral decubitus position in hightension glaucoma may differ from that in NTG. In patients participating in the Ocular Hypertension Treatment Study, even a 1 mm Hg difference in IOP between fellow eyes was associated with an increase in the risk of developing a glaucomatous VF defect,26 unlike NTG patients examined in the Low-pressure Glaucoma Treatment Study.27 In the present investigation, although the number of high-tension glaucoma patients preferring the worse eye–dependent lateral decubitus position was significantly greater than those preferring the better eye–dependent lateral decubitus position (71.9% vs 28.1%, P ¼ .013), the baseline IOP of the worse eye was higher than that of the better eye (24.8 6 6.2 mm Hg vs 22.1 6 4.8 mm Hg, P ¼ .003). Even though the differences in the mean values of the axial length and central corneal thickness showed borderline significance between the worse and better eyes in OAG patients with asymmetric VF loss (Table 2), these differences were very small (axial length, 24.8 mm vs 24.7 mm, respectively; and central corneal thickness, 530.9 mm vs 533.1 mm, respectively). Neither were the differences significant in NTG or hightension glaucoma patients (Table 3). It is well recognized that IOP exists on a continuum, and that dividing OAG into NTG and high-tension glaucoma by using baseline IOPs of 21 and 22 mm Hg is arbitrary. However, we have used the terms NTG and high-tension glaucoma
PREFERRED SLEEPING POSITION AND ASYMMETRIC VISUAL FIELD LOSS
743
TABLE 5. Results of the Survey on Preferred Sleeping Position of the Open-Angle Glaucoma Patients With Asymmetric Visual Field Loss
Preferred Lying Position
Open-Angle Glaucoma, n (%) (N ¼ 430)
Normal-Tension Glaucoma, n (%) (N ¼ 309)
High-Tension Glaucoma, n (%) (N ¼ 121)
No preferred lying position Worse eye–dependent LDP Better eye–dependent LDP Supine Prone Both LDP
120 (28.0) 89 (20.7) 43 (10.0) 73 (17.0) 12 (2.8) 93 (21.6)
92 (29.8) 66 (21.4) 34 (11.0) 63 (20.4) 6 (1.9) 48 (15.5)
28 (23.1) 23 (19.0) 9 (7.4) 30 (24.8) 6 (5.0) 25 (20.7)
Open-Angle Glaucoma, n (%) (N ¼ 132)
Normal-Tension Glaucoma, n (%) (N ¼ 100)
High-Tension Glaucoma, n (%) (N ¼ 32)
89 (67.4) 43 (32.6) <.001
66 (66.0) 34 (34.0) .001
23 (71.9) 9 (28.1) .013
Worse eye–dependent LDP Better eye–dependent LDP P valueb
P Valuea
.537
LDP ¼ lateral decubitus position. Preferred lying position ¼ answer the below questionnaire on the preferred lying position during sleep, According to the result of the Humphrey visual field test, right LDP and left LDP were converted into worse eye-dependent LDP or better eye-dependent LDP. Asymmetric visual field loss was defined as a difference in mean deviation of at least 2 dB between the eyes. Worse eye and better eye were defined based on the mean deviation value determined in the Humphrey visual field test. a 2 x test, comparison between normal-tension glaucoma patients and high-tension glaucoma patients. b One-sample x2 test.
merely for the purpose of grouping patients in order to look for differences. The limitation of this study is that the preferred sleeping position results were based on a questionnaire; collection of more exact and reliable data using video recording during sleep is warranted. Another limitation is the retrospective and cross-sectional nature of our study; a further study with
a prospective design is required to overcome this limitation. In conclusion, results of the present study strongly suggest that the sleep position habitually preferred by OAG patients may be associated with greater VF loss. In order to confirm our speculation, a prospective, long-term follow-up study will be necessary.
ALL AUTHORS HAVE COMPLETED AND SUBMITTED THE ICMJE FORM FOR DISCLOSURE OF POTENTIAL CONFLICTS OF INTEREST and none were reported. Robert Ritch is supported in part by the Joseph and Geraldine LaMotta Research Fund of the New York Glaucoma Research Institute, New York. None of the other authors have any funding/support to disclose. Contributions of authors: design of study (K.N.K., K.H.P.); data collection (K.N.K., J.W.J.); analysis and interpretation of data (K.N.K., K.H.P., D.M.K., R.R.); writing of article (K.N.K.); critical revision of article (K.N.K., K.H.P., R.R., J.W.J., D.M.K.); and final approval of article (K.N.K., J.W.J., K.H.P., D.M.K., R.R.).
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