Head Position and Intraocular Pressure in the Lateral Decubitus Position

Effect of neck extension on intraocular pressure in paediatric patients undergoing palatoplasty

BACKGROUND

Intraocular pressure (IOP) can increase with postural changes, which can cause ocular complications. Neck extension is commonly used during palatoplasty to improve surgical angulation. This study evaluates whether neck extension affects IOP during palatoplasty.

METHODS

In this prospective observational study, IOP was measured using a rebound tonometer at four specific time points: T1, 10 min after anaesthesia while in the supine position; T2, 5 min after neck extension; T3, at completion of palatoplasty with neck extended; and T4, 5 min after returning to the supine position. The primary outcome was the IOP at T2, and the secondary outcomes were the IOPs at T3 and T4. Haemodynamic and respiratory variables were also measured at each time point.

RESULTS

Thirty-seven patients were included. IOP at T2 was significantly higher than at T1 (15.8 ± 3.4 mmHg vs 10.5 ± 2.8 mmHg, P < 0.001), and IOPs at T3 and T4 were also significantly higher than at T1 (T3 vs T1: 18.9 ± 3.6 mmHg vs 10.5 ± 2.8 mmHg, P < 0.001; T4 vs T1: 13.3 ± 3.7 mmHg vs 10.5 ± 2.8 mmHg, P < 0.001). However, no significant differences were observed for the haemodynamic and respiratory variables at any time point.

CONCLUSION

Our findings indicate that the intraoperative neck extension position during palatoplasty significantly increases IOP in paediatric cleft palate patients undergoing a palatoplasty.

Posture-induced Changes in Intraocular Pressure After Trabeculectomy in Patients With Primary Open-angle Glaucoma

PRCIS

Trabeculectomy can effectively reduce posture-induced changes in intraocular pressure (IOP) in patients with primary open-angle glaucoma (POAG).

PURPOSE

The purpose of this study was to investigate posture-induced changes in IOP after trabeculectomy in patients with medically uncontrolled POAG.

DESIGN

This was a prospective, consecutive study.

METHODS

Thirty-seven eyes of 37 patients with POAG were included. IOP was measured before trabeculectomy and 1, 2, 3, and 6 months postoperatively with patients in the sitting position, supine position, and lateral decubitus position (LDP) sequentially using iCare IC200 rebound tonometry. In the LDP, the eye scheduled for trabeculectomy was in the dependent position, the contralateral unoperated eye was a control eye. The central corneal thickness, axial length, and anterior chamber depth were measured using partial coherence interferometry.

RESULTS

In the sitting, supine, and LDP, the IOP was significantly reduced at every time point during the follow-up. Although the posture-induced changes in IOP persisted during the follow-up, the range of IOP changes in the sitting and supine positions, sitting and LDP, and the supine and LDP were significantly reduced after than before trabeculectomy. The central corneal thickness did not change significantly after trabeculectomy.

CONCLUSION

Trabeculectomy can effectively reduce posture-induced changes in IOP in patients with POAG.

Effect of Body Position on Intraocular Pressure (IOP), Intracranial Pressure (ICP), and Translaminar Pressure (TLP) Via Continuous Wireless Telemetry in Nonhuman Primates (NHPs)

Purpose

Recent retrospective clinical studies and animal experiments have suggested that cerebrospinal fluid pressure (CSFP) is important in glaucoma, acting through the translaminar pressure (TLP = IOP − CSFP), which directly affects the optic nerve head. In this study, IOP and intracranial pressure (ICP; a surrogate of CSFP) were measured at various body positions to quantify the determinants of TLP.

Methods

We have developed an implantable wireless pressure telemetry system based on a small piezoelectric sensor with low temporal drift. Telemetry transducers were placed in the anterior chamber to measure IOP and in the brain parenchyma at eye height to measure ICP. IOP was calibrated against anterior cannulation manometry, and ICP/CSFP was calibrated against an intraparenchymal Codman ICP Express microsensor. We measured IOP, ICP, and TLP = IOP − ICP continuously at 200 Hz in three male nonhuman primates (NHPs) in three trials; pressures were then averaged for 30 seconds per body position. Relative change of IOP, ICP, and TLP from the supine (baseline) position to the seated, standing, and inverted positions were quantified.

Results

TLP changed significantly and instantaneously from the supine to seated (+14 mm Hg), supine to standing (+13 mm Hg) and supine to inverted (−12 mm Hg) positions (P < 0.05). There was no significant TLP change for supine to prone. ICP showed greater relative change than IOP.

Conclusions

TLP change due to body position change is driven more by ICP/CSFP than IOP. IOP, ICP, and TLP variability, coupled with telemetry, should allow us to test the hypotheses that IOP, ICP, or TLP fluctuations contribute independently to glaucoma onset or progression.

A PRELIMINARY STUDY OF INTRINSIC AND EXTRINSIC FACTORS INFLUENCING INTRAOCULAR PRESSURE IN BROOK TROUT (SALVELINUS FONTINALIS)

Reference intervals of intraocular pressure (IOP) are poorly described in piscine species as the factors that may influence it. Rebound tonometry was used to measure IOP in 28 adult brook trout (Salvelinus fontinalis) anesthetized in a buffered solution of 60 mg/L tricaine methanesulfonate (n = 16) or restrained with electronarcosis (n = 12) at 16 mA. There was no significant effect of the eye side, sex, fish origin, and body weight, but IOP values were significantly higher with electronarcosis (mean ± SD: 16.4 ± 5.0 mm Hg) than with immersion anesthesia (10.8 ± 3.3 mm Hg; P = 0.0017). The same restraint method should be used for comparison with previously published IOP values or when evaluating individual variations over time.

Effects of Ab Interno XEN Gel Implantation on Postural Intraocular Pressure Elevations

Purpose: The aim of this study was to analyze the postural intraocular pressure (IOP) changes in open-angle glaucoma after ab interno XEN gel implant surgery and to compare them with the changes observed with trabeculectomy and medical treatment.Patients and Methods: The study sample included 18 patients with XEN gel implants, 30 patients who had trabeculectomy, and 30 medically managed glaucoma patients. All patients in XEN gel implant and trabeculectomy groups had at least 11 months of follow-up and had successful surgeries that resulted in medication-free control of IOP. A rebound tonometer (Icare, Finland Oy, Helsinki, Finland) was used to measure the IOP levels at the sitting, supine, and dependent lateral decubitus (DLDP) positions after a 5-minute rest at each position.Results: In all the groups, the mean IOP values in the DLDP and supine positions were significantly higher than the sitting position. The IOP elevation after moving from sitting to supine position was significantly reduced in XEN gel implant and trabeculectomy groups compared to medical treatment group (p = .001 and p = .002, respectively). The IOP elevation after a moving from sitting to DLDP was also significantly reduced in XEN gel implant and trabeculectomy groups compared to the medical treatment group (p = .003 and p = .01, respectively). However, there was no significant difference in IOP change after moving from sitting to supine or DLDP positions between XEN gel implant and trabeculectomy groups (p = .74 and p = .98, respectively).Conclusion: This study demonstrated that XEN gel implant could reduce postural elevations in IOP to the same degree as trabeculectomy and provide significantly better postural IOP control than medical treatment. This surgery can be an effective minimally invasive alternative for patients with significant positional IOP elevations.

Posture-Related Changes of Intraocular Pressure in Patients With Acute Primary Angle Closure

Purpose

To evaluate the posture-related change in intraocular pressure (IOP) of eyes with angle-closure disease and the associated factors.

Methods

Eyes were prospectively enrolled and divided into three groups: eyes with acute primary angle-closure (APAC), fellow eyes of acute primary angle-closure (FAPAC), and eyes with nonacute primary angle-closure disease (PACD). All of them had been treated with laser peripheral iridotomy. IOP was measured in the sitting, supine, and lateral decubitus positions (LDP) five minutes after posture change. Anterior chamber angle parameters and angle-closure mechanism were evaluated by anterior segment optical coherence tomography.

Results

Forty-four eyes were enrolled into each group. APAC eyes showed more LDP-Sitting IOP increase than fellow eyes (5.7 ± 2.7 vs. 2.2 ± 1.4 mm Hg, P < 0.001) and nonacute PACD eyes (3.6 ± 2.0 mm Hg, P < 0.001). LDP-sitting IOP change was higher in eyes with exaggerated lens vault (having shallow anterior chamber and volcano-like iris-lens configuration) than in those without it (APAC: 6.3 ± 2.6 vs. 3.9 ± 2.1 mm Hg, P = 0.011). Linear regression revealed that LDP-sitting IOP change in the APAC group was negatively associated with angle opening distance (AOD), trabecular iris space area, scleral spur angle, and anterior chamber depth (ACD1000). With multivariable stepwise regression analysis, AOD750 remained statistically significant (beta-coefficient = −8.36, P = 0.014).

Conclusions

APAC eyes had significant posture-related IOP changes, associated with narrower angle structures and exaggerated lens vault.

Change in Intraocular Pressure and Ocular Perfusion Pressure Due to Trendelenburg Positioning

SIGNIFICANCE

This study increases foundational knowledge about the dynamic relationships between intraocular pressure (IOP), blood pressure (BP), and mean ocular perfusion pressure (MOPP) in the setting of steep Trendelenburg positioning and may inform medical decision making for patients in which this positioning is planned.

PURPOSE

The purpose of this study was to explore the demographic and clinical factors related to IOP, MOPP, and BP change during Trendelenburg positioning in a large sample of subjects.

METHODS

A single-cohort interventional study was conducted at the American Academy of Optometry 2017 annual meeting. Baseline demographic data were collected by a secure survey tool. IOP and BP were then measured while seated and again after 1 and 2 minutes in a steep Trendelenburg position. Raw and percentage differences for each variable were compared between time points, and regression analyses demonstrated factors related to change in IOP, BP, and MOPP during steep Trendelenburg positioning.

RESULTS

Median IOP increased from 16.3 mmHg (13.3 to 18.3 mmHg) at baseline to 25.0 mmHg (21.7 to 28.7 mmHg) at 1 minute after assuming the Trendelenburg position. More than 95% of individual eyes exhibited an IOP increase of at least 10%, and 45% had an IOP increase of 10 mmHg or greater. Correspondingly, MOPP fell from 50.3 mmHg (43.4 to 55.4 mmHg) at baseline to 36.3 mmHg (31.9 to 43.3 mmHg). Mean ocular perfusion pressure decreased by at least 10 in 90% of eyes. In multivariate regression analysis, factors independently related to percentage IOP increase were increasing weight, less myopic refractive error, lower baseline pulse, and lower baseline IOP (total r = 0.31, P < .001). Conversely, weight was the only variable independently related to percent MOPP change, and this relationship was weak (r = 0.05, P = .008).

CONCLUSIONS

Our results confirm that steep Trendelenburg positioning causes an increase in IOP and a decrease in MOPP in almost all eyes. Considering the identified causative factors will inform clinical education and provide foundational knowledge for future investigations.

Twenty-four-Hour Intraocular Pressure-Related Patterns from Contact Lens Sensors in Normal-Tension Glaucoma and Healthy Eyes: The Exploring Nyctohemeral Intraocular pressure related pattern for Glaucoma Management (ENIGMA) Study

PURPOSE

To investigate 24-hour nyctohemeral intraocular pressure (IOP)-related patterns with contact lens sensors (CLSs) in eyes with primary open-angle glaucoma (POAG) with normal baseline IOP (i.e., normal-tension glaucoma [NTG]) and healthy controls.

DESIGN

Prospective, case-control study.

PARTICIPANTS

Thirty eyes of 30 patients with NTG, who had had a wash-out period for their IOP-lowering treatment, and 20 eyes of 20 healthy volunteer subjects.

METHODS

Patients and subjects were hospitalized for the purposes of 24-hour CLS (SENSIMED Triggerfish; Sensimed AG, Lausanne, Switzerland) measurement. The IOP-related patterns during wake and sleep times over the course of the 24 hours were compared between the 2 groups. The 24-hour ambulatory blood pressure and posture were monitored simultaneously. A generalized linear model was used to find the factors associated with NTG.

MAIN OUTCOME MEASURES

The IOP-related patterns, including mean and standard deviation (SD) of measurements, amplitude of cosine-fit curve, acrophase (signal peak), and bathyphase (signal trough) values (millivolt equivalents [mVEq]).

RESULTS

The SDs of the 24-hour CLS measurements were significantly greater in NTG eyes than in healthy controls (112.51±26.90 vs. 85.18±29.61 mVEq, P = 0.002). The amplitudes of cosine-fit curve (141.88±39.96 vs. 106.08±41.49 mVEq, P = 0.004) and acrophase values (277.74±129.80 vs. 190.58±127.88 mVEq, P = 0.024), mostly measured during nocturnal period, were significantly greater in NTG eyes than in healthy controls. The NTG subjects slept longer in the lateral decubitus posture than the healthy controls (199.1±137.8 vs. 113.2±86.2 minutes, P = 0.009). In the multivariable generalized linear model, the greater amplitude of cosine-fit curve (β = 0.218, P = 0.012) and greater time of decubitus posture during sleep (β = 0.180, P = 0.004) were found to be significantly associated with NTG.

CONCLUSIONS

Continuous monitoring of 24-hour IOP-related values with CLS can be useful for assessment of glaucoma risk, especially for patients with NTG whose IOP appears to be in the normal range. Fluctuation of 24-hour IOP-related values and posture during sleep time might be associated with NTG.

Acute effects of posture on intraocular pressure

Many experiments have documented the response of intraocular pressure (IOP) to postural change. External forces caused by gravitational orientation change produce a dynamic response that is encountered every day during normal activities. Tilting the body at a small downward angle is also relevant to studying the effects of hypogravity (spaceflight), including ocular changes. We examined data from 36 independent datasets from 30 articles on IOP response to postural change, representing a total population of 821 subjects (≥1173 eyes) with widely varying initial and final postures. We confirmed that IOP was well predicted by a simple quantity, namely the hydrostatic pressure at the level of the eye, although the dependence was complex (nonlinear). Our results show that posturally induced IOP change can be explained by hydrostatic forcing plus an autoregulatory contribution that is dependent on hydrostatic effects. This study represents data from thousands of IOP measurements and provides insight for future studies that consider postural change in relation to ocular physiology, intraocular pressure, ocular blood flow and aqueous humor dynamics.

Relationship between sleep position and glaucoma progression

PURPOSE OF REVIEW

As humans spend a considerable portion of life in the horizontal position, it is vital to better understand the effect of sleep position on glaucoma.

RECENT FINDINGS

The mean positional increase from the supine position to the lateral decubitus position (LDP) in recent literature is less than 2 mmHg for each eye in its dependent position and less than 1 mmHg in the nondependent position. The right LDP is most commonly favored sleeping position. Some evidence suggests that the positional increases persist and so could lead to worse glaucomatous progression in the dependent eye. However, multiple studies failed to find a strong association. Ideally future research will identify risk factors for higher positional increases to identify patients who may benefit from a change in sleep position. To date, medications and argon laser trabeculoplasty have been ineffective in blunting the positional increase, although glaucoma surgery does reduce it. Raising the head of the bed has been linked with blunting the increase as well.

SUMMARY

Certain sleeping positions appear to be associated with higher intraocular pressure, although the association between sleep position and glaucoma progression is not as clear.

Error in measurement of intraocular pressure with the Icare and IcarePRO

PURPOSE

We sought to determine whether changes in the measurement angle of the Icare TA01i and IcarePRO tonometers led to errors in the measurement of intraocular pressure (IOP).

METHODS

In this prospective, single-facility study, we analyzed 77 patients from November 2017 to September 2019. We measured IOP with the Icare TA01i and IcarePRO while changing the angle of the device with the cornea center and analyzed the associated changes in the measurement.

RESULTS

IOP measured with the Icare tilted - 30°, - 15° vertically was significantly higher than that measured with the Icare tilted horizontally (p < 0.0001, p < 0.0001). The IOP measured with a + 10° vertical tilt was significantly lower than that measured horizontally (p < 0.0001). When the IcarePRO was tilted + 90° vertically, the IOP was significantly lower with the patient in the supine position than in the lateral position (p = 0.00058).

CONCLUSIONS

IOP measured with the Icare and IcarePRO is affected by the measurement angle. The study results will direct the clinicians to exercise extra precautions in determining the measurement angle while measuring IOP.

Positional Intraocular Pressure of Vitrectomized and Normal Fellow Eyes

Purpose

To compare posture-induced intraocular pressure (IOP) changes in vitrectomized eyes and normal eyes of patients who had vitrectomy in one eye.

Methods

A total of 31 patients older than 20 years of age who underwent vitrectomy were enrolled in the study. At least six months after vitrectomy, we measured IOP in both eyes using a rebound tonometer 10 minutes after the patient assumed sitting, supine, right lateral decubitus, and left lateral decubitus positions. Patients with a history of ocular surgery (not including vitrectomy) or recent medication use associated with IOP were excluded. IOP and ocular parameters of vitrectomized and normal fellow eyes were compared. For the decubitus position, IOP values of dependent and nondependent eyes were compared.

Results

No significant difference was observed in IOP between vitrectomized and normal eyes in the sitting and supine positions. The IOP for dependent eyes (on the lower side in the lateral decubitus position) was significantly higher than the IOP for nondependent eyes in both right lateral decubitus (right vitrectomized eye 19.31 ± 4.20 vs. 16.71 ± 4.02 mmHg, p < 0.001; left vitrectomized eye 18.35 ± 1.75 vs. 16.04 ± 3.02 mmHg, p = 0.003) and left lateral decubitus (right vitrectomized eye 17.32 ± 4.63 vs. 19.15 ± 3.83 mmHg, p = 0.004; left vitrectomized eye 16.19 ± 1.81 vs. 18.12 ± 2.29 mmHg, p < 0.001) positions.

Conclusions

IOP was higher in the dependent than the nondependent eye in the lateral decubitus position, for both vitrectomized and nonoperated eyes.

The Magnitude and Time Course of IOP Change in Response to Body Position Change in Nonhuman Primates Measured Using Continuous IOP Telemetry

Purpose

To study the effect and time course of body position changes on IOP in nonhuman primates.

Methods

We recorded continuous bilateral IOP measurements with a wireless telemetry implant in three rhesus macaques in seven different body positions. IOP measurements were acquired in the seated-upright, standing, prone, supine, right and left lateral decubitus positions (LDPs), and head-down inverted positions. Continuous IOP was recorded for 90 seconds in each position before returning to a supine reference position until IOP stabilized; measurements were averaged after IOP stabilized at each position.

Results

Head-down inversion increased IOP an average of 8.9 mm Hg, compared to the supine reference. In the LDP, IOP decreased an average of 0.5 mm Hg in the nondependent eye (i.e., the higher eye), while the fellow dependent (i.e., lower) eye increased an average of 0.5 mm Hg, compared to supine reference. Standing and seated positions decreased IOP 1.5 and 2.2 mm Hg, respectively, compared with supine reference. IOP changes occurred within 4 to 15 seconds of a body position change, and timing was affected by the speed at which body position was changed. Compared to the IOP in the supine position, the IOP in the inverted, prone, and seated positions was significantly different (P = 0.0313 for all). The IOP in the standing position was not statistically different from the IOP in the supine position (P = 0.094). In addition, the IOP was significantly different between the nondependent eye and the dependent eye in the LDPs compared to the supine position (P = 0.0313).

Conclusions

Body position has a significant effect on IOP and those changes persist over time.

Effect of Lateral Decubitus Body Posture on Anterior Chamber Angle in Healthy Subjects: An Anterior Segment Optical Coherence Tomography Study

PURPOSE

To investigate the effect of the lateral decubitus (LD) position on the anterior chamber (AC) angle in healthy subjects.

MATERIALS AND METHODS

Twenty-three healthy young subjects were included in this prospective observational study. We measured AC angle parameters in the sitting and the left LD positions using anterior segment optical coherence tomography (Visante OCT): trabecular-iris angle (TIA), angle opening distance (AOD500), trabecular-iris space area (TISA500), anterior chamber width, lens vault, and anterior chamber depth. The Wilcoxon signed-rank test was used to compare the parameters between different body positions. Interobserver reproducibility of AC angle measurements was assessed by intraclass correlation coefficients.

RESULTS

Postural alterations from sitting to the left LD position significantly reduced the AC angle on the temporal side in right eyes (TIA: 39.53±2.38 to 38.31±3.47 degrees; AOD500: 0.72±0.13 to 0.65±0.08; TISA500: 0.25±0.06 to 0.22±0.04; all P<0.05), whereas no significant changes were noted on the nasal side. Contrastingly, a significant decrease in the AC angle on the nasal side was noted for left eyes (TIA: 39.49±2.24 to 38.17±2.76 degrees; AOD500: 0.68±0.09 to 0.64±0.10; TISA500: 0.23±0.04 to 0.21±0.03; all P<0.05). Anterior chamber width and anterior chamber depth were unaffected by postural alterations, but lens vault significantly was reduced following a shift to the left LD position.

CONCLUSIONS

The AC angle parameters on the nondependent side of the eye in the LD position were significantly reduced compared with those in the sitting position. Therefore, postural shift from sitting to the LD position may induce alterations in the AC angle.

Effect of Different Head Positions in Lateral Decubitus Posture on Intraocular Pressure in Treated Patients With Open-Angle Glaucoma

PURPOSE

To investigate the effects of different head positions in the lateral decubitus posture on intraocular pressure (IOP) in medically treated patients with open-angle glaucoma (OAG).

DESIGN

Prospective observational study.

METHODS

setting: Institutional.

PARTICIPANTS

Twenty patients with bilateral OAG who received only latanoprost as treatment.

OBSERVATION PROCEDURES

IOP was measured using an ICare Pro tonometer in the sitting, supine, right, and left lateral decubitus posture. In lateral decubitus posture, IOP measurements were taken with 3 different head positions (30 degrees higher than, 30 degrees lower than, and parallel to the center of the thoracic vertebra) in a randomized sequence.

MAIN OUTCOME MEASURES

Comparison of the IOPs between the dependent (lower-sided) and nondependent eyes in the lateral decubitus postures with different head positions. We also analyzed the differences in IOPs between the better and worse eyes.

RESULTS

IOP was higher in the dependent eyes than in the nondependent eyes in lateral decubitus posture, regardless of the head position (all P < .05). Lower head position increased the IOP of dependent eyes, compared with the neutral or higher head position. However, the amounts of IOP elevation seen during the changes of body posture or head position were not significantly different between the better and worse eyes.

CONCLUSIONS

Low head position elevates IOP of the dependent eyes of medically treated OAG patients compared with neutral head position in the lateral decubitus posture. Adjustment of the height of a pillow may help mitigate IOP elevations resulting from lying on the side with a low or no pillow in glaucoma patients.