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Effect of Lateral Decubitus Position on Intraocular Pressure in Glaucoma Patients with Asymmetric Visual Field Loss
Effect of Lateral Decubitus Position on Intraocular Pressure in Glaucoma Patients with Asymmetric Visual Field Loss Kyoung Nam Kim, MD,1 Jin Wook Jeoung, MD,1,2 Ki Ho Park, MD, PhD,1,2 Dae Seung Lee, MD,1,2 Dong Myung Kim, MD, PhD1,2 Purpose: To investigate the effect of the lateral decubitus position (LDP) on intraocular pressure (IOP) in glaucoma patients with asymmetric visual field loss. Design: Prospective, cross-sectional study. Participants: Ninety-eight eyes of 49 consecutive bilateral glaucoma patients with asymmetric visual field loss, divided into better eye and worse eye groups for calculation of mean deviation. Methods: Intraocular pressure was measured using a Goldmann applanation tonometer and rebound tonometer (Icare PRO; Icare Finland Oy, Helsinki, Finland) in each of the following positions: sitting, supine, right LDP, and left LDP. Visual field was examined using the Humphrey Field Analyzer (HFA II; Carl Zeiss Meditec, Dublin, CA). A questionnaire on the preferred lying position during sleep was administered to each of the patients. Main Outcome Measures: The IOPs measured by rebound tonometer for the better and worse eyes in each position were compared using paired t tests. Agreement between the Goldmann applanation tonometry and rebound tonometry results was assessed by a Bland-Altman plot. Results: The IOPs of the better and worse eyes in the sitting position showed no significant difference (P⬍0.476). The IOP of the worse eye was significantly higher than that of the better eye in the supine position (16.8⫾3.0 mmHg vs. 15.1⫾1.8 mmHg; P⬍0.001). The IOPs of the worse and better eyes in their dependent LDP were 19.1⫾3.0 mmHg and 17.6⫾2.3 mmHg, respectively (change in IOP, 1.6⫾2.4 mmHg; P⬍0.001). Of the enrolled patients, 75.5% preferred the LDP, and 75.7% of these LDP-preferring patients preferred the worse eye dependent-LDP. The Bland-Altman plot comparing the Goldmann applanation tonometry and rebound tonometry readings showed reasonable agreement between the 2 methods (r2⬍0.001; P ⫽ 0.972). Conclusions: This study showed that IOP-elevation asymmetry in LDP is associated with asymmetric visual field loss in glaucoma patients. The LDP, habitually preferred by glaucoma patients, also may be associated with asymmetric visual field damage. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. Ophthalmology 2013;120:731–735 © 2013 by the American Academy of Ophthalmology.
Previous studies have shown that intraocular pressure (IOP) reduction can decrease the progression of visual field damage in glaucoma patients.1 However, in some patients, despite well-controlled IOP,1 glaucoma continues to progress. It is well known that IOP is higher in the supine position than when sitting.2–5 Moreover, the extent of IOP increase from the sitting to the supine position is greater in patients with primary open-angle glaucoma, ocular hypertension, and normal-tension glaucoma (NTG) than in normal subjects.5–7 Therefore, the increase of IOP in the supine position may play a role in the progression of glaucoma.3,8,9 Recently, with regard to the effect of lateral decubitus position (LDP) on IOP, Malihi and Sit10 and Lee et al11 conducted prospective studies of healthy volunteers. In their findings, IOP in the LDP was consistently higher in the dependent eye (the lower-positioned eye, e.g., the right eye in the right LDP) than in the nondependent eye (the upperpositioned eye, e.g., the left eye in the right LDP); furthermore, the IOP of the dependent eye in the LDP was consistently higher than that in the sitting or supine position. © 2013 by the American Academy of Ophthalmology Published by Elsevier Inc.
Generally, a person spends between one quarter and one third of his lifetime sleeping in a lying position. During sleep, one rests in the supine position, the prone position, or the LDP. People also spend a considerable amount of time in the LDP while watching television or reading. Thus, in glaucoma, the effect of the LDP on IOP may be as important as the sitting or supine positions on IOP. No previous studies have investigated the relationship between LDP IOP and visual field defect in glaucoma patients. This study compared the bilateral eyes of glaucoma patients with their asymmetric visual field loss to assess the association between IOP change in a lying position (including LDP) and the degree of visual field damage.
Patients and Methods This was a prospective, observational study. It was approved by the Institutional Review Board of Seoul National University Hospital and was conducted in accordance with the tenets of the Declaration of Helsinki. Patients with NTG who had asymmetric ISSN 0161-6420/13/$–see front matter http://dx.doi.org/10.1016/j.ophtha.2012.09.021
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visual field loss in both eyes were enrolled consecutively when they visited from the Glaucoma Clinic of Seoul National University Hospital from May through June 2012. Written informed consent was obtained from each subject before his or her participation in the study. To meet the criteria for a diagnosis of NTG, patients had to have an untreated baseline IOP of 21 mmHg or less, a glaucomatous optic disc change, a reproducible glaucomatous visual field defect on the Swedish interactive threshold algorithm of 30-2 perimetry (Humphrey Field Analyzer II; Carl Zeiss Meditec, Dublin, CA), and open angles on gonioscopy. The IOP was checked at least at 3 visits, and the measurements were obtained at different times during the daylight hours. Patients were excluded if the IOP was more than 21 mmHg for any of the measurements. Glaucomatous optic disc changes were characterized as focal or diffuse neuroretinal rim thinning, localized notching, or nerve fiber layer defects with correlating visual field changes. Glaucomatous visual field defects were defined by 2 of the following 3 criteria: the presence of a cluster of 3 points on a pattern deviation probability plot with P⬍0.05, one of which had P⬍0.01; a pattern standard deviation with P⬍0.05; or glaucoma hemifield test results outside normal limits. A difference in mean deviation (MD) of at least 2 dB between the eyes was considered to constitute asymmetric visual field loss.12,13 Both eyes of each of the NTG patients were treated with the same antiglaucoma agent. Patients with high-tension glaucoma were excluded because in ocular hypertension treatment, study even a 1-mmHg increase in asymmetric IOP between fellow eyes was associated with an increase in risk for a glaucomatous visual field defect, unlike in NTG.14,15 Eyes having poor reliability on visual field analysis (⬎20% fixation loss and ⬎15% false-positive or false-negative answers), 20/40 or worse best-corrected visual acuity, a history of intraocular surgery, high myopia (⬎6.0 diopters), or diseases that could secondarily influence IOP or the visual field also were excluded. Goldmann applanation tonometry (AT900; Haag-Streit, Köniz, Switzerland) IOP measurements with the subject in the sitting position were performed by a single observer (D.S.L.) who was blinded to that subject’s visual field result. For each eye, 3 measurements were obtained and averaged. A questionnaire on the preferred lying position then was administered to each of the subjects. The following questions were asked: (1) Do you have a preferred lying position when you are sleeping or resting? (yes or no); and (2) If your answer to Question 1 was yes, which body position do you prefer: the right LDP, the left LDP, the supine position, or the prone position? Rebound tonometry (Icare PRO; Icare Finland Oy, Helsinki, Finland) IOP measurements were obtained by another single observer (K.N.K.) who was blinded to the IOPs measured by Goldmann applanation tonometry, the subject’s preferred lying position, and the visual field result. Icare PRO is a new rebound tonometer that uses a built-in inclination sensor to measure the supine position IOP. The IOP was measured in each position in the following order: sitting, supine, right LDP, and left LDP. The right eye always was examined first. Each position was maintained for at least 10 minutes before measuring the IOP. In the supine position and both LDPs, a latex pillow was placed under the head and neck to maintain the horizontal position. In the LDP, care was taken not to compress the dependent eye against the latex pillow. For accurate measurement of IOP by rebound tonometer, the tip of the probe was maintained at a distance of 3 to 7 mm from the corneal center and was oriented perpendicular to the corneal plane. After the 6 consecutive measurements were completed, the mean IOP was displayed. If the variation between the measurements was within normal limits, the mean IOP was displayed with a green background. If the variation was slightly high, the mean IOP was shown in yellow, and a high variation was shown in red. For each
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Table 1. Patient Demographics (n ⫽ 49) Variable Mean age (yrs) Sex (female:male) IOP (mmHg)† Spherical equivalent (D) Axial length (mm) Degree of exophthalmos (mm) HVF MD (dB) PSD (dB) VFI (%) No. of medications No. of patients using: ␣2-Agonist -Blocker Carbonic anhydrase inhibitor Prostaglandin analog
Better Eye (MeanⴞSD)
13.5⫾2.2 ⫺2.1⫾3.4 24.2⫾1.5 10.4⫾3.5 ⫺2.4⫾3.1 3.8⫾2.9 94.6⫾7.6
Worse Eye (MeanⴞSD) 58.6⫾10.8 23:26 13.4⫾1.9 ⫺2.2⫾3.3 24.3⫾1.5 10.4⫾3.2 ⫺11.0⫾6.4 11.5⫾3.5 68.1⫾21.1 1.7⫾0.9
P Value*
0.870 0.145 0.273 0.804 ⬍0.001 ⬍0.001 ⬍0.001
13 17 9 43
D ⫽ diopters; HVF ⫽ Humphrey visual field; IOP ⫽ intraocular pressure; MD ⫽ mean deviation; PSD ⫽ pattern standard deviation; SD ⫽ standard deviation; VFI ⫽ visual field index. *Paired t test. † Measured by Goldmann applanation tonometer.
eye and each position, 3 mean IOP measurements displayed with a green background were obtained and averaged. For all patients, the better eye and the worse eye were defined based on the MD value determined in the Humphrey visual field analysis. All of the statistical analyses were performed using SPSS software version 18.0 (SPSS, Inc., Chicago, IL). The demographics of the subjects were compared according to the IOP measured by Goldmann applanation tonometry, the spherical equivalent, the axial length, the degree of exophthalmos, the number of glaucoma medications, and the IOP measured by rebound tonometer for the better and worse eyes in each position using paired t tests. Paired t tests also were used to compare the change of IOP in each position. A Bland-Altman plot was drawn to assess the agreement between rebound tonometry and Goldmann applanation tonometry. A value of P⬍0.05 was considered to represent a significant difference.
Results Forty-nine subjects were enrolled consecutively in this study. The subjects’ demographics are summarized in Table 1. There were 23 women and 26 men (mean age, 58.6⫾10.8 years; range, 31–78 years). Thirty-one patients had the worse visual field in the left eye, and 18 patients had the worse visual field in the right eye (P⬍0.001). There was a significant difference in MD between the better and worse eyes (⫺2.4⫾3.1 dB and ⫺11.0⫾6.4 dB, respectively; P⬍0.001). There was no significant difference between the Goldmann applanation tonometer-measured IOP of the better and worse eyes in the sitting position (13.5⫾2.2 mmHg and 13.4⫾1.9 mmHg, respectively; P ⫽ 0.870). On average, 1.7 antiglaucoma agents were used by each subject. A fixed-combination drug was counted as 2 different agents. A Bland-Altman scatterplot comparing the Goldmann applanation tonometry and rebound tonometry readings (Fig 1) showed reasonable agreement between the 2 methods. The IOP differences
Kim et al 䡠 Effect of Lateral Decubitus Position on IOP in Glaucoma Table 3. Difference in Intraocular Pressure between 2 Lateral Decubitus Positions IOP (MeanⴞStandard Deviation), mmHg*
Better eye-dependent LDP Worse eye-dependent LDP Change in IOP P value†
Better Eye
Worse Eye
17.6⫾2.3 16.4⫾2.4 1.1⫾1.8 ⬍0.001
16.4⫾2.4 19.1⫾3.0 2.7⫾3.0 ⬍0.001
IOP ⫽ intraocular pressure; LDP ⫽ lateral decubitus position. *Measured by rebound tonometer. † Paired t test.
Figure 1. Bland-Altman analysis results showing distribution of intraocular pressure differences (Icare rebound tonometry [IRT] value minus Goldmann applanation tonometry [GAT] value, mmHg; y-axis) and mean intraocular pressure values of 2 tonometers (x-axis) for each eye (98 eyes of 49 patients) measured (r2⬍0.001; P ⫽ 0.972). As is apparent, there was a reasonable agreement between the 2 tonometry methods. SD ⫽ standard deviation.
had a mean of 0.29 mmHg, a standard deviation of 1.28 mmHg, and a 95% confidence interval of ⫺2.21 to 2.79 mmHg. These differences, as indicated in Figure 1, were constant over the entire IOP measurement range. The IOPs of the better and worse eyes in the sitting position were 13.8⫾2.2 mmHg and 13.7⫾2.0 mmHg, respectively, with no significant difference (P⬍0.476; Table 2). By contrast, in the supine position, the IOP of the worse eye was significantly higher than that of the better eye (16.8⫾3.0 mmHg and 15.1⫾1.8 mmHg, respectively; P⬍0.001). In both the better eye-dependent LDP and the worse eye-dependent LDP, the IOP of the dependent eye was significantly higher than that of the contralateral nondependent eye (P⬍0.001 in both LDPs). The IOPs of the worse and better eyes in their dependent LDP were 19.1⫾3.0 mmHg and 17.6⫾2.3 mmHg, respectively, and the difference (1.6⫾2.4 mmHg) was statistically significant (P⬍0.001). The IOP differences between the 2 LDPs are shown in Table 3. As is indicated, the IOP differences in the better and worse eyes were 1.1⫾1.8 mmHg and 2.7⫾3.0 mmHg, respectively (P⬍0.001 in both LDPs).
Table 2. Intraocular Pressure in Different Body Positions IOP (MeanⴞStandard Deviation), mmHg* Position
Better Eye
Worse Eye
P Value†
Sitting IOP Supine IOP Better eye-dependent LDP Worse eye-dependent LDP
13.8⫾2.2 15.1⫾1.8 17.6⫾2.3 16.4⫾2.4
13.7⫾2.0 16.8⫾3.0 16.4⫾2.4 19.1⫾3.0
0.476 ⬍0.001 ⬍0.001 ⬍0.001
IOP ⫽ intraocular pressure; LDP ⫽ lateral decubitus position. *Measured by rebound tonometer. † Paired t test.
Table 4 summarizes the statistical IOP comparisons among the different positions. The IOP in the supine position was higher than that in the sitting position in both eyes. Regardless of laterality, dependent position, or nondependent position, the IOP of both eyes in the LDP was higher than that in the sitting position (P⬍0.001). The IOP of the dependent eye in the LDP was higher than that in the supine position (P⬍0.001). The questionnaire on habitual lying positions showed that 28 (57.1%) patients preferred the worse eye-dependent LDP and that 9 patients (18.3%) preferred the better eye-dependent LDP. Another 12 patients (24.5%) had no preferred lying position or preferred the supine or prone positions. That is, 75.5% (n ⫽ 37) of the enrolled patients preferred the LDP, and 75.7% (n ⫽ 28) of these LDP-preferring patients preferred the worse eye-dependent LDP.
Discussion Previous studies have made 2 important findings: IOP is higher in the supine position than in the sitting position, and the extent of IOP elevation is higher in glaucoma patients than in normal subjects.2–7 Tsukahara and Sasaki5 reported that such IOP elevation was more remarkable in NTG patients than in normal subjects or in cases of primary open-angle glaucoma. Liu et al3,16,17 found that for both glaucoma patients and normal subjects, nocturnal IOP measured in the supine position was significantly higher than in the conventional sitting position. In this study, the postural change from the sitting to the supine position elevated the IOP by 2.2 mmHg, which is comparable with previous studies in which the postural IOP change ranged between 1.6 and 8.6 mmHg in glaucomatous eyes and eyes with ocular hypertension.2–7 Two recent studies also compared IOP changes from the sitting to the supine position in glaucoma patients. For primary open-angle glaucoma subjects, Hirooka and Shiraga18 reported that the magnitude of IOP elevation by postural change was significantly greater in eyes with more advanced visual field defects. These IOP changes were 4.4 mmHg in the worse eye (MD, ⫺13.2 dB) and 3.6 mmHg in the better eye (MD, ⫺7.6 dB). For NTG subjects, Kiuchi et al4 found that visual field damage was significantly more advanced in eyes with IOP elevation induced by greater postural change. These IOP changes were 4.5 mmHg in the
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Table 4. Change in Intraocular Pressure According to Postural Change
Postural Change
Change in Intraocular Pressure in the Better Eye (MeanⴞStandard Deviation) mmHg*
Supine vs. sitting Better eye-dependent LDP vs. sitting Worse eye-dependent LDP vs. sitting Better eye-dependent LDP vs. supine Worse eye-dependent LDP vs. supine
1.2⫾2.1 3.7⫾2.4 2.6⫾2.5 2.5⫾2.4 1.3⫾2.1
P Value
Change in Intraocular Pressure in the Worse Eye (MeanⴞStandard Deviation) mmHg*
P Value†
⬍0.001 ⬍0.001 ⬍0.001 ⬍0.001 ⬍0.001
3.3⫾3.0 2.7⫾2.2 5.4⫾3.1 ⫺0.4⫾3.0 2.3⫾3.4
⬍0.001 ⬍0.001 ⬍0.001 0.301 ⬍0.001
†
LDP ⫽ lateral decubitus position. *Measured by rebound tonometer. † Paired t test.
worse eye (MD, ⫺8.9 dB) and 3.2 mmHg in the better eye (MD, ⫺5.9 dB; P ⫽ 0.001). In this study, the extent of IOP elevation by postural change also was significantly higher in the worse eye (MD, ⫺11.3 dB) than in the better eye (MD, ⫺2.4 dB): 3.2 mmHg and 1.2 mmHg, respectively (P⬍0.001). Kiuchi et al19 discovered that the progression of visual field damage (the MD slope) in NTG patients correlated with the magnitude of IOP elevation induced by postural changes (correlation coefficient, r ⫽ ⫺0.682; P⬍0.001). These results suggest that glaucoma can progress when patients are in a lying position, such as during sleep. Similar to the reports of Malihi and Sit10 and Lee et al,11 in this study the IOP in the LDP were consistently higher in the dependent eye than in the contralateral nondependent eye, and the dependent-eye IOP in the LDP was consistently higher than in the sitting or supine position. One spends approximately one quarter to one third of life sleeping. Previous studies of sleep positions have shown that as age advances, the preferences for the LDP and its duration increase.20,21 People also spend a considerable amount of time in the LDP when resting (e.g., when watching television or reading). In the simple survey from this study, 75.5% of enrolled patients preferred the LDP, and 75.7% of these LDP-preferring patients preferred the worse eye-dependent LDP, compared with only 24.3% who preferred the better eye-dependent LDP. Thus, the effect of the LDP on IOP is equally or more important to the clinical management of glaucoma than the effect of the supine position. As far as we are aware, this study is the first to assess the effect of the LDP on IOP in patients with glaucoma, especially those with asymmetric visual field loss. These results may explain partially why some glaucoma patients progress despite well-controlled sitting IOP readings. Of course, there was a limitation in this study: the result of the preferred sleeping position was based only on the questionnaire. To acquire the exact preferred position, a study using a video recording system during sleep is warranted.21 Several assumptions have been made with respect to the mechanisms of IOP responses to postural change. The most likely mechanism is the rise of episcleral venous pressure in the supine position.22–24 Krieglstein et al24 suggested that IOP rise is correlated with changes in episcleral venous pressure and ophthalmic arterial pressure. Another explanation is alterations in the rate of
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uveoscleral outflow resulting from increased choroidal blood volume.25 Recently, Malihi and Sit10 pointed out that most of the previous studies of postural IOP change had obtained measurements in a fixed sequence, having obtained the first measurements in either the sitting or supine position. This fixed order of IOP measurement in fact may have worked as a confounding factor, specifically, by the effects of ocular squeezing at initial or prior measurement and aqueous fluid shift after repeated measurement.26,27 By randomizing the measurement sequence, Malihi and Sit were able to control the possible effects of the measurement sequence and repeated IOP measurement. Alternatively, in the current study, postural IOP was measured by a rebound tonometer, not an applanation tonometer. It is expected, therefore, that neither repeated measurements nor the measurement sequence had much effect on the IOP values.28 –30 In rebound tonometry, IOP is determined by measuring the force produced by a tiny plastic probe as it rebounds from the cornea. This small probe, allowing for comfortable IOP measurement, makes it possible to measure IOP without topical anesthetics and with little ocular squeezing. Moreover, rebound tonometry does not increase aqueous outflow or fluid shift sometimes caused by applanation of the cornea.26 In fact, rebound tonometry has been shown to have an accuracy similar to the Tono-Pen (Mentor O & O Inc., Santa Barbara, CA [incorporating Bio-Rad]) and is comparable with Goldmann applanation tonometry for IOPs over a reasonable range in adults.28,31 Indeed, in this study, IOP measured by rebound tonometry was comparable with that measured by Goldmann applanation tonometry (13.8⫾2.1 and 13.5⫾2.1 mmHg, respectively; P ⫽ 0.028). In summary, this study showed that in glaucoma patients, IOP-elevation asymmetry in the LDP is associated with asymmetric visual field loss. Intraocular pressure elevation in the dependent eye while in the LDP is a possible contributor to the development or progression of glaucoma. The LDP, habitually preferred by glaucoma patients, also may be associated with asymmetric visual field damage. To confirm this speculation, a longitudinal study of a larger patient population is necessary.
Kim et al 䡠 Effect of Lateral Decubitus Position on IOP in Glaucoma
References 1. Collaborative Normal-Tension Glaucoma Study Group. The effectiveness of intraocular pressure reduction in the treatment of normaltension glaucoma. Am J Ophthalmol 1998;126:498–505. 2. Prata TS, De Moraes CG, Kanadani FN, et al. Postureinduced intraocular pressure changes: considerations regarding body position in glaucoma patients. Surv Ophthalmol 2010;55:445–53. 3. Liu JH, Zhang X, Kripke DF, Weinreb RN. Twenty-four-hour intraocular pressure pattern associated with early glaucomatous changes. Invest Ophthalmol Vis Sci 2003;44:1586 –90. 4. Kiuchi T, Motoyama Y, Oshika T. Postural response of intraocular pressure and visual field damage in patients with untreated normal-tension glaucoma. J Glaucoma 2010;19:191–3. 5. Tsukahara S, Sasaki T. Postural change of IOP in normal persons and in patients with primary wide open-angle glaucoma and lowtension glaucoma. Br J Ophthalmol 1984;68:389–92. 6. Krieglstein G, Langham ME. Influence of body position on the intraocular pressure of normal and glaucomatous eyes. Ophthalmologica 1975;171:132– 45. 7. Jain MR, Marmion VJ. Rapid pneumatic and Mackey-Marg applanation tonometry to evaluate the postural effect on intraocular pressure. Br J Ophthalmol 1976;60:687–93. 8. 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 – 42. 9. Noël C, Kabo AM, Romanet JP, et al. Twenty-four-hour time course of intraocular pressure in healthy and glaucomatous Africans: relation to sleep patterns. Ophthalmology 2001;108:139–44. 10. Malihi M, Sit AJ. Effect of head and body position on intraocular pressure. Ophthalmology 2012;119:987–91. 11. Lee JY, Yoo C, Jung JH, et al. The effect of lateral decubitus position on intraocular pressure in healthy young subjects. Acta Ophthalmol 2012;90:e68 –72. 12. Feuer WJ, Anderson DR. Static threshold asymmetry in early glaucomatous visual field loss. Ophthalmology 1989;96:1285–97. 13. Poinoosawmy D, Fontana L, Wu JX, et al. Frequency of asymmetric visual field defects in normal-tension and hightension glaucoma. Ophthalmology 1998;105:988 –91. 14. Levine RA, Demirel S, Fan J, et al, Ocular Hypertension Treatment Study Group. Asymmetries and visual field summaries as predictors of glaucoma in the Ocular Hypertension Treatment Study. Invest Ophthalmol Vis Sci 2006;47:3896 –903. 15. Greenfield DS, Liebmann JM, Ritch R, Krupin T, LowPressure Glaucoma Study Group. Visual field and intraocular pressure asymmetry in the low-pressure glaucoma treatment study. Ophthalmology 2007;114:460 –5.
16. Liu JH, Kripke DF, Hoffman RE, et al. Elevation of human intraocular pressure at night under moderate illumination. Invest Ophthalmol Vis Sci 1999;40:2439 – 42. 17. Liu JH, Kripke DF, Twa MD, et al. Twenty-four-hour pattern of intraocular pressure in the aging population. Invest Ophthalmol Vis Sci 1999;40:2912–7. 18. Hirooka K, Shiraga F. Relationship between postural change of the intraocular pressure and visual field loss in primary open-angle glaucoma. J Glaucoma 2003;12:379 – 82. 19. 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;113:2150 –5. 20. De Koninck J, Lorrain D, Gagnon P. Sleep positions and position shifts in five age groups: an ontogenetic picture. Sleep 1992;15:143–9. 21. Dzvonik ML, Kripke DF, Klauber M, Ancoli-Israel S. Body position changes and periodic movements in sleep. Sleep 1986;9:484 –91. 22. Friberg TR, Sanborn G, Weinreb RN. Intraocular and episcleral venous pressure increase during inverted posture. Am J Ophthalmol 1987;103:523– 6. 23. Sultan M, Blondeau P. Episcleral venous pressure in younger and older subjects in the sitting and supine positions. J Glaucoma 2003;12:370 –3. 24. 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;206:99–106. 25. Longo A, Geiser MH, Riva CE. Posture changes and subfoveal choroidal blood flow. Invest Ophthalmol Vis Sci 2004; 45:546 –51. 26. Pekmezci M, Chang ST, Wilson BS, et al. Effect of measurement order between right and left eyes on intraocular pressure measurement. Arch Ophthalmol 2011;129:276 – 81. 27. Gaton DD, Ehrenberg M, Lusky M, et al. Effect of repeated applanation tonometry on the accuracy of intraocular pressure measurements. Curr Eye Res 2010;3:475–9. 28. Iliev ME, Goldblum D, Katsoulis K, et al. Comparison of rebound tonometry with Goldmann applanation tonometry and correlation with central corneal thickness. Br J Ophthalmol 2006;90:833–5. 29. Kontiola A. A new electromechanical method for measuring intraocular pressure. Doc Ophthalmol 1996 –1997;93:265–76. 30. Kontiola AI. A new induction-based impact method for measuring intraocular pressure. Acta Ophthalmol Scand 2000;78:142–5. 31. Cook JA, Botello AP, Elders A, et al, Surveillance of Ocular Hypertension Study Group. Systematic review of the agreement of tonometers with Goldmann applanation tonometry. Ophthalmology 2012;119:1552–7.
Footnotes and Financial Disclosures Originally received: July 6, 2012. Final revision: August 22, 2012. Accepted: September 12, 2012. Available online: December 20, 2012.
Manuscript no. 2012-1009.
1
Department of Ophthalmology, Seoul National University Hospital, Seoul, Korea.
2
Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea.
Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. Supported in part by the National Research Foundation of Korea funded by the Korean government, Seoul, Korea (grant no.: 2012-0006066). Correspondence: Ki Ho Park, MD, PhD, Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul 110-744, Korea. E-mail: [email protected].
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Previous studies have shown that intraocular pressure (IOP) reduction can decrease the progression of visual field damage in glaucoma patients.1 However, in some patients, despite well-controlled IOP,1 glaucoma continues to progress. It is well known that IOP is higher in the supine position than when sitting.2–5 Moreover, the extent of IOP increase from the sitting to the supine position is greater in patients with primary open-angle glaucoma, ocular hypertension, and normal-tension glaucoma (NTG) than in normal subjects.5–7 Therefore, the increase of IOP in the supine position may play a role in the progression of glaucoma.3,8,9 Recently, with regard to the effect of lateral decubitus position (LDP) on IOP, Malihi and Sit10 and Lee et al11 conducted prospective studies of healthy volunteers. In their findings, IOP in the LDP was consistently higher in the dependent eye (the lower-positioned eye, e.g., the right eye in the right LDP) than in the nondependent eye (the upperpositioned eye, e.g., the left eye in the right LDP); furthermore, the IOP of the dependent eye in the LDP was consistently higher than that in the sitting or supine position. © 2013 by the American Academy of Ophthalmology Published by Elsevier Inc.
Generally, a person spends between one quarter and one third of his lifetime sleeping in a lying position. During sleep, one rests in the supine position, the prone position, or the LDP. People also spend a considerable amount of time in the LDP while watching television or reading. Thus, in glaucoma, the effect of the LDP on IOP may be as important as the sitting or supine positions on IOP. No previous studies have investigated the relationship between LDP IOP and visual field defect in glaucoma patients. This study compared the bilateral eyes of glaucoma patients with their asymmetric visual field loss to assess the association between IOP change in a lying position (including LDP) and the degree of visual field damage.
Patients and Methods This was a prospective, observational study. It was approved by the Institutional Review Board of Seoul National University Hospital and was conducted in accordance with the tenets of the Declaration of Helsinki. Patients with NTG who had asymmetric ISSN 0161-6420/13/$–see front matter http://dx.doi.org/10.1016/j.ophtha.2012.09.021
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visual field loss in both eyes were enrolled consecutively when they visited from the Glaucoma Clinic of Seoul National University Hospital from May through June 2012. Written informed consent was obtained from each subject before his or her participation in the study. To meet the criteria for a diagnosis of NTG, patients had to have an untreated baseline IOP of 21 mmHg or less, a glaucomatous optic disc change, a reproducible glaucomatous visual field defect on the Swedish interactive threshold algorithm of 30-2 perimetry (Humphrey Field Analyzer II; Carl Zeiss Meditec, Dublin, CA), and open angles on gonioscopy. The IOP was checked at least at 3 visits, and the measurements were obtained at different times during the daylight hours. Patients were excluded if the IOP was more than 21 mmHg for any of the measurements. Glaucomatous optic disc changes were characterized as focal or diffuse neuroretinal rim thinning, localized notching, or nerve fiber layer defects with correlating visual field changes. Glaucomatous visual field defects were defined by 2 of the following 3 criteria: the presence of a cluster of 3 points on a pattern deviation probability plot with P⬍0.05, one of which had P⬍0.01; a pattern standard deviation with P⬍0.05; or glaucoma hemifield test results outside normal limits. A difference in mean deviation (MD) of at least 2 dB between the eyes was considered to constitute asymmetric visual field loss.12,13 Both eyes of each of the NTG patients were treated with the same antiglaucoma agent. Patients with high-tension glaucoma were excluded because in ocular hypertension treatment, study even a 1-mmHg increase in asymmetric IOP between fellow eyes was associated with an increase in risk for a glaucomatous visual field defect, unlike in NTG.14,15 Eyes having poor reliability on visual field analysis (⬎20% fixation loss and ⬎15% false-positive or false-negative answers), 20/40 or worse best-corrected visual acuity, a history of intraocular surgery, high myopia (⬎6.0 diopters), or diseases that could secondarily influence IOP or the visual field also were excluded. Goldmann applanation tonometry (AT900; Haag-Streit, Köniz, Switzerland) IOP measurements with the subject in the sitting position were performed by a single observer (D.S.L.) who was blinded to that subject’s visual field result. For each eye, 3 measurements were obtained and averaged. A questionnaire on the preferred lying position then was administered to each of the subjects. The following questions were asked: (1) Do you have a preferred lying position when you are sleeping or resting? (yes or no); and (2) If your answer to Question 1 was yes, which body position do you prefer: the right LDP, the left LDP, the supine position, or the prone position? Rebound tonometry (Icare PRO; Icare Finland Oy, Helsinki, Finland) IOP measurements were obtained by another single observer (K.N.K.) who was blinded to the IOPs measured by Goldmann applanation tonometry, the subject’s preferred lying position, and the visual field result. Icare PRO is a new rebound tonometer that uses a built-in inclination sensor to measure the supine position IOP. The IOP was measured in each position in the following order: sitting, supine, right LDP, and left LDP. The right eye always was examined first. Each position was maintained for at least 10 minutes before measuring the IOP. In the supine position and both LDPs, a latex pillow was placed under the head and neck to maintain the horizontal position. In the LDP, care was taken not to compress the dependent eye against the latex pillow. For accurate measurement of IOP by rebound tonometer, the tip of the probe was maintained at a distance of 3 to 7 mm from the corneal center and was oriented perpendicular to the corneal plane. After the 6 consecutive measurements were completed, the mean IOP was displayed. If the variation between the measurements was within normal limits, the mean IOP was displayed with a green background. If the variation was slightly high, the mean IOP was shown in yellow, and a high variation was shown in red. For each
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Table 1. Patient Demographics (n ⫽ 49) Variable Mean age (yrs) Sex (female:male) IOP (mmHg)† Spherical equivalent (D) Axial length (mm) Degree of exophthalmos (mm) HVF MD (dB) PSD (dB) VFI (%) No. of medications No. of patients using: ␣2-Agonist -Blocker Carbonic anhydrase inhibitor Prostaglandin analog
Better Eye (MeanⴞSD)
13.5⫾2.2 ⫺2.1⫾3.4 24.2⫾1.5 10.4⫾3.5 ⫺2.4⫾3.1 3.8⫾2.9 94.6⫾7.6
Worse Eye (MeanⴞSD) 58.6⫾10.8 23:26 13.4⫾1.9 ⫺2.2⫾3.3 24.3⫾1.5 10.4⫾3.2 ⫺11.0⫾6.4 11.5⫾3.5 68.1⫾21.1 1.7⫾0.9
P Value*
0.870 0.145 0.273 0.804 ⬍0.001 ⬍0.001 ⬍0.001
13 17 9 43
D ⫽ diopters; HVF ⫽ Humphrey visual field; IOP ⫽ intraocular pressure; MD ⫽ mean deviation; PSD ⫽ pattern standard deviation; SD ⫽ standard deviation; VFI ⫽ visual field index. *Paired t test. † Measured by Goldmann applanation tonometer.
eye and each position, 3 mean IOP measurements displayed with a green background were obtained and averaged. For all patients, the better eye and the worse eye were defined based on the MD value determined in the Humphrey visual field analysis. All of the statistical analyses were performed using SPSS software version 18.0 (SPSS, Inc., Chicago, IL). The demographics of the subjects were compared according to the IOP measured by Goldmann applanation tonometry, the spherical equivalent, the axial length, the degree of exophthalmos, the number of glaucoma medications, and the IOP measured by rebound tonometer for the better and worse eyes in each position using paired t tests. Paired t tests also were used to compare the change of IOP in each position. A Bland-Altman plot was drawn to assess the agreement between rebound tonometry and Goldmann applanation tonometry. A value of P⬍0.05 was considered to represent a significant difference.
Results Forty-nine subjects were enrolled consecutively in this study. The subjects’ demographics are summarized in Table 1. There were 23 women and 26 men (mean age, 58.6⫾10.8 years; range, 31–78 years). Thirty-one patients had the worse visual field in the left eye, and 18 patients had the worse visual field in the right eye (P⬍0.001). There was a significant difference in MD between the better and worse eyes (⫺2.4⫾3.1 dB and ⫺11.0⫾6.4 dB, respectively; P⬍0.001). There was no significant difference between the Goldmann applanation tonometer-measured IOP of the better and worse eyes in the sitting position (13.5⫾2.2 mmHg and 13.4⫾1.9 mmHg, respectively; P ⫽ 0.870). On average, 1.7 antiglaucoma agents were used by each subject. A fixed-combination drug was counted as 2 different agents. A Bland-Altman scatterplot comparing the Goldmann applanation tonometry and rebound tonometry readings (Fig 1) showed reasonable agreement between the 2 methods. The IOP differences
Kim et al 䡠 Effect of Lateral Decubitus Position on IOP in Glaucoma Table 3. Difference in Intraocular Pressure between 2 Lateral Decubitus Positions IOP (MeanⴞStandard Deviation), mmHg*
Better eye-dependent LDP Worse eye-dependent LDP Change in IOP P value†
Better Eye
Worse Eye
17.6⫾2.3 16.4⫾2.4 1.1⫾1.8 ⬍0.001
16.4⫾2.4 19.1⫾3.0 2.7⫾3.0 ⬍0.001
IOP ⫽ intraocular pressure; LDP ⫽ lateral decubitus position. *Measured by rebound tonometer. † Paired t test.
Figure 1. Bland-Altman analysis results showing distribution of intraocular pressure differences (Icare rebound tonometry [IRT] value minus Goldmann applanation tonometry [GAT] value, mmHg; y-axis) and mean intraocular pressure values of 2 tonometers (x-axis) for each eye (98 eyes of 49 patients) measured (r2⬍0.001; P ⫽ 0.972). As is apparent, there was a reasonable agreement between the 2 tonometry methods. SD ⫽ standard deviation.
had a mean of 0.29 mmHg, a standard deviation of 1.28 mmHg, and a 95% confidence interval of ⫺2.21 to 2.79 mmHg. These differences, as indicated in Figure 1, were constant over the entire IOP measurement range. The IOPs of the better and worse eyes in the sitting position were 13.8⫾2.2 mmHg and 13.7⫾2.0 mmHg, respectively, with no significant difference (P⬍0.476; Table 2). By contrast, in the supine position, the IOP of the worse eye was significantly higher than that of the better eye (16.8⫾3.0 mmHg and 15.1⫾1.8 mmHg, respectively; P⬍0.001). In both the better eye-dependent LDP and the worse eye-dependent LDP, the IOP of the dependent eye was significantly higher than that of the contralateral nondependent eye (P⬍0.001 in both LDPs). The IOPs of the worse and better eyes in their dependent LDP were 19.1⫾3.0 mmHg and 17.6⫾2.3 mmHg, respectively, and the difference (1.6⫾2.4 mmHg) was statistically significant (P⬍0.001). The IOP differences between the 2 LDPs are shown in Table 3. As is indicated, the IOP differences in the better and worse eyes were 1.1⫾1.8 mmHg and 2.7⫾3.0 mmHg, respectively (P⬍0.001 in both LDPs).
Table 2. Intraocular Pressure in Different Body Positions IOP (MeanⴞStandard Deviation), mmHg* Position
Better Eye
Worse Eye
P Value†
Sitting IOP Supine IOP Better eye-dependent LDP Worse eye-dependent LDP
13.8⫾2.2 15.1⫾1.8 17.6⫾2.3 16.4⫾2.4
13.7⫾2.0 16.8⫾3.0 16.4⫾2.4 19.1⫾3.0
0.476 ⬍0.001 ⬍0.001 ⬍0.001
IOP ⫽ intraocular pressure; LDP ⫽ lateral decubitus position. *Measured by rebound tonometer. † Paired t test.
Table 4 summarizes the statistical IOP comparisons among the different positions. The IOP in the supine position was higher than that in the sitting position in both eyes. Regardless of laterality, dependent position, or nondependent position, the IOP of both eyes in the LDP was higher than that in the sitting position (P⬍0.001). The IOP of the dependent eye in the LDP was higher than that in the supine position (P⬍0.001). The questionnaire on habitual lying positions showed that 28 (57.1%) patients preferred the worse eye-dependent LDP and that 9 patients (18.3%) preferred the better eye-dependent LDP. Another 12 patients (24.5%) had no preferred lying position or preferred the supine or prone positions. That is, 75.5% (n ⫽ 37) of the enrolled patients preferred the LDP, and 75.7% (n ⫽ 28) of these LDP-preferring patients preferred the worse eye-dependent LDP.
Discussion Previous studies have made 2 important findings: IOP is higher in the supine position than in the sitting position, and the extent of IOP elevation is higher in glaucoma patients than in normal subjects.2–7 Tsukahara and Sasaki5 reported that such IOP elevation was more remarkable in NTG patients than in normal subjects or in cases of primary open-angle glaucoma. Liu et al3,16,17 found that for both glaucoma patients and normal subjects, nocturnal IOP measured in the supine position was significantly higher than in the conventional sitting position. In this study, the postural change from the sitting to the supine position elevated the IOP by 2.2 mmHg, which is comparable with previous studies in which the postural IOP change ranged between 1.6 and 8.6 mmHg in glaucomatous eyes and eyes with ocular hypertension.2–7 Two recent studies also compared IOP changes from the sitting to the supine position in glaucoma patients. For primary open-angle glaucoma subjects, Hirooka and Shiraga18 reported that the magnitude of IOP elevation by postural change was significantly greater in eyes with more advanced visual field defects. These IOP changes were 4.4 mmHg in the worse eye (MD, ⫺13.2 dB) and 3.6 mmHg in the better eye (MD, ⫺7.6 dB). For NTG subjects, Kiuchi et al4 found that visual field damage was significantly more advanced in eyes with IOP elevation induced by greater postural change. These IOP changes were 4.5 mmHg in the
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Table 4. Change in Intraocular Pressure According to Postural Change
Postural Change
Change in Intraocular Pressure in the Better Eye (MeanⴞStandard Deviation) mmHg*
Supine vs. sitting Better eye-dependent LDP vs. sitting Worse eye-dependent LDP vs. sitting Better eye-dependent LDP vs. supine Worse eye-dependent LDP vs. supine
1.2⫾2.1 3.7⫾2.4 2.6⫾2.5 2.5⫾2.4 1.3⫾2.1
P Value
Change in Intraocular Pressure in the Worse Eye (MeanⴞStandard Deviation) mmHg*
P Value†
⬍0.001 ⬍0.001 ⬍0.001 ⬍0.001 ⬍0.001
3.3⫾3.0 2.7⫾2.2 5.4⫾3.1 ⫺0.4⫾3.0 2.3⫾3.4
⬍0.001 ⬍0.001 ⬍0.001 0.301 ⬍0.001
†
LDP ⫽ lateral decubitus position. *Measured by rebound tonometer. † Paired t test.
worse eye (MD, ⫺8.9 dB) and 3.2 mmHg in the better eye (MD, ⫺5.9 dB; P ⫽ 0.001). In this study, the extent of IOP elevation by postural change also was significantly higher in the worse eye (MD, ⫺11.3 dB) than in the better eye (MD, ⫺2.4 dB): 3.2 mmHg and 1.2 mmHg, respectively (P⬍0.001). Kiuchi et al19 discovered that the progression of visual field damage (the MD slope) in NTG patients correlated with the magnitude of IOP elevation induced by postural changes (correlation coefficient, r ⫽ ⫺0.682; P⬍0.001). These results suggest that glaucoma can progress when patients are in a lying position, such as during sleep. Similar to the reports of Malihi and Sit10 and Lee et al,11 in this study the IOP in the LDP were consistently higher in the dependent eye than in the contralateral nondependent eye, and the dependent-eye IOP in the LDP was consistently higher than in the sitting or supine position. One spends approximately one quarter to one third of life sleeping. Previous studies of sleep positions have shown that as age advances, the preferences for the LDP and its duration increase.20,21 People also spend a considerable amount of time in the LDP when resting (e.g., when watching television or reading). In the simple survey from this study, 75.5% of enrolled patients preferred the LDP, and 75.7% of these LDP-preferring patients preferred the worse eye-dependent LDP, compared with only 24.3% who preferred the better eye-dependent LDP. Thus, the effect of the LDP on IOP is equally or more important to the clinical management of glaucoma than the effect of the supine position. As far as we are aware, this study is the first to assess the effect of the LDP on IOP in patients with glaucoma, especially those with asymmetric visual field loss. These results may explain partially why some glaucoma patients progress despite well-controlled sitting IOP readings. Of course, there was a limitation in this study: the result of the preferred sleeping position was based only on the questionnaire. To acquire the exact preferred position, a study using a video recording system during sleep is warranted.21 Several assumptions have been made with respect to the mechanisms of IOP responses to postural change. The most likely mechanism is the rise of episcleral venous pressure in the supine position.22–24 Krieglstein et al24 suggested that IOP rise is correlated with changes in episcleral venous pressure and ophthalmic arterial pressure. Another explanation is alterations in the rate of
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uveoscleral outflow resulting from increased choroidal blood volume.25 Recently, Malihi and Sit10 pointed out that most of the previous studies of postural IOP change had obtained measurements in a fixed sequence, having obtained the first measurements in either the sitting or supine position. This fixed order of IOP measurement in fact may have worked as a confounding factor, specifically, by the effects of ocular squeezing at initial or prior measurement and aqueous fluid shift after repeated measurement.26,27 By randomizing the measurement sequence, Malihi and Sit were able to control the possible effects of the measurement sequence and repeated IOP measurement. Alternatively, in the current study, postural IOP was measured by a rebound tonometer, not an applanation tonometer. It is expected, therefore, that neither repeated measurements nor the measurement sequence had much effect on the IOP values.28 –30 In rebound tonometry, IOP is determined by measuring the force produced by a tiny plastic probe as it rebounds from the cornea. This small probe, allowing for comfortable IOP measurement, makes it possible to measure IOP without topical anesthetics and with little ocular squeezing. Moreover, rebound tonometry does not increase aqueous outflow or fluid shift sometimes caused by applanation of the cornea.26 In fact, rebound tonometry has been shown to have an accuracy similar to the Tono-Pen (Mentor O & O Inc., Santa Barbara, CA [incorporating Bio-Rad]) and is comparable with Goldmann applanation tonometry for IOPs over a reasonable range in adults.28,31 Indeed, in this study, IOP measured by rebound tonometry was comparable with that measured by Goldmann applanation tonometry (13.8⫾2.1 and 13.5⫾2.1 mmHg, respectively; P ⫽ 0.028). In summary, this study showed that in glaucoma patients, IOP-elevation asymmetry in the LDP is associated with asymmetric visual field loss. Intraocular pressure elevation in the dependent eye while in the LDP is a possible contributor to the development or progression of glaucoma. The LDP, habitually preferred by glaucoma patients, also may be associated with asymmetric visual field damage. To confirm this speculation, a longitudinal study of a larger patient population is necessary.
Kim et al 䡠 Effect of Lateral Decubitus Position on IOP in Glaucoma
References 1. Collaborative Normal-Tension Glaucoma Study Group. The effectiveness of intraocular pressure reduction in the treatment of normaltension glaucoma. Am J Ophthalmol 1998;126:498–505. 2. Prata TS, De Moraes CG, Kanadani FN, et al. Postureinduced intraocular pressure changes: considerations regarding body position in glaucoma patients. Surv Ophthalmol 2010;55:445–53. 3. Liu JH, Zhang X, Kripke DF, Weinreb RN. Twenty-four-hour intraocular pressure pattern associated with early glaucomatous changes. Invest Ophthalmol Vis Sci 2003;44:1586 –90. 4. Kiuchi T, Motoyama Y, Oshika T. Postural response of intraocular pressure and visual field damage in patients with untreated normal-tension glaucoma. J Glaucoma 2010;19:191–3. 5. Tsukahara S, Sasaki T. Postural change of IOP in normal persons and in patients with primary wide open-angle glaucoma and lowtension glaucoma. Br J Ophthalmol 1984;68:389–92. 6. Krieglstein G, Langham ME. Influence of body position on the intraocular pressure of normal and glaucomatous eyes. Ophthalmologica 1975;171:132– 45. 7. Jain MR, Marmion VJ. Rapid pneumatic and Mackey-Marg applanation tonometry to evaluate the postural effect on intraocular pressure. Br J Ophthalmol 1976;60:687–93. 8. 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 – 42. 9. Noël C, Kabo AM, Romanet JP, et al. Twenty-four-hour time course of intraocular pressure in healthy and glaucomatous Africans: relation to sleep patterns. Ophthalmology 2001;108:139–44. 10. Malihi M, Sit AJ. Effect of head and body position on intraocular pressure. Ophthalmology 2012;119:987–91. 11. Lee JY, Yoo C, Jung JH, et al. The effect of lateral decubitus position on intraocular pressure in healthy young subjects. Acta Ophthalmol 2012;90:e68 –72. 12. Feuer WJ, Anderson DR. Static threshold asymmetry in early glaucomatous visual field loss. Ophthalmology 1989;96:1285–97. 13. Poinoosawmy D, Fontana L, Wu JX, et al. Frequency of asymmetric visual field defects in normal-tension and hightension glaucoma. Ophthalmology 1998;105:988 –91. 14. Levine RA, Demirel S, Fan J, et al, Ocular Hypertension Treatment Study Group. Asymmetries and visual field summaries as predictors of glaucoma in the Ocular Hypertension Treatment Study. Invest Ophthalmol Vis Sci 2006;47:3896 –903. 15. Greenfield DS, Liebmann JM, Ritch R, Krupin T, LowPressure Glaucoma Study Group. Visual field and intraocular pressure asymmetry in the low-pressure glaucoma treatment study. Ophthalmology 2007;114:460 –5.
16. Liu JH, Kripke DF, Hoffman RE, et al. Elevation of human intraocular pressure at night under moderate illumination. Invest Ophthalmol Vis Sci 1999;40:2439 – 42. 17. Liu JH, Kripke DF, Twa MD, et al. Twenty-four-hour pattern of intraocular pressure in the aging population. Invest Ophthalmol Vis Sci 1999;40:2912–7. 18. Hirooka K, Shiraga F. Relationship between postural change of the intraocular pressure and visual field loss in primary open-angle glaucoma. J Glaucoma 2003;12:379 – 82. 19. 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;113:2150 –5. 20. De Koninck J, Lorrain D, Gagnon P. Sleep positions and position shifts in five age groups: an ontogenetic picture. Sleep 1992;15:143–9. 21. Dzvonik ML, Kripke DF, Klauber M, Ancoli-Israel S. Body position changes and periodic movements in sleep. Sleep 1986;9:484 –91. 22. Friberg TR, Sanborn G, Weinreb RN. Intraocular and episcleral venous pressure increase during inverted posture. Am J Ophthalmol 1987;103:523– 6. 23. Sultan M, Blondeau P. Episcleral venous pressure in younger and older subjects in the sitting and supine positions. J Glaucoma 2003;12:370 –3. 24. 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;206:99–106. 25. Longo A, Geiser MH, Riva CE. Posture changes and subfoveal choroidal blood flow. Invest Ophthalmol Vis Sci 2004; 45:546 –51. 26. Pekmezci M, Chang ST, Wilson BS, et al. Effect of measurement order between right and left eyes on intraocular pressure measurement. Arch Ophthalmol 2011;129:276 – 81. 27. Gaton DD, Ehrenberg M, Lusky M, et al. Effect of repeated applanation tonometry on the accuracy of intraocular pressure measurements. Curr Eye Res 2010;3:475–9. 28. Iliev ME, Goldblum D, Katsoulis K, et al. Comparison of rebound tonometry with Goldmann applanation tonometry and correlation with central corneal thickness. Br J Ophthalmol 2006;90:833–5. 29. Kontiola A. A new electromechanical method for measuring intraocular pressure. Doc Ophthalmol 1996 –1997;93:265–76. 30. Kontiola AI. A new induction-based impact method for measuring intraocular pressure. Acta Ophthalmol Scand 2000;78:142–5. 31. Cook JA, Botello AP, Elders A, et al, Surveillance of Ocular Hypertension Study Group. Systematic review of the agreement of tonometers with Goldmann applanation tonometry. Ophthalmology 2012;119:1552–7.
Footnotes and Financial Disclosures Originally received: July 6, 2012. Final revision: August 22, 2012. Accepted: September 12, 2012. Available online: December 20, 2012.
Manuscript no. 2012-1009.
1
Department of Ophthalmology, Seoul National University Hospital, Seoul, Korea.
2
Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea.
Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. Supported in part by the National Research Foundation of Korea funded by the Korean government, Seoul, Korea (grant no.: 2012-0006066). Correspondence: Ki Ho Park, MD, PhD, Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul 110-744, Korea. E-mail: [email protected].
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