Diagnostic accuracy of intraocular pressure measurement for the detection of raised intracranial pressure: meta-analysis: a systematic review

High myopia at high altitudes

Background: Optic nerve sheath diameter (ONSD) increases significantly at high altitudes, and is associated with the presence and severity of acute mountain sickness (AMS). Exposure to hypobaria, hypoxia, and coldness when hiking also impacts intraocular pressure (IOP). To date, little is known about ocular physiological responses in trekkers with myopia at high altitudes. This study aimed to determine changes in the ONSD and IOP between participants with and without high myopia (HM) during hiking and to test whether these changes could predict symptoms of AMS. Methods: Nine participants with HM and 18 without HM participated in a 3-day trek of Xue Mountain. The ONSD, IOP, and questionnaires were examined before and during the trek of Xue Mountain. Results: The ONSD values increased significantly in both HM (p = 0.005) and non-HM trekkers (p = 0.018) at an altitude of 1,700 m. In the HM group, IOP levels were greater than those in the non-HM group (p = 0.034) on the first day of trekking (altitude: 3,150 m). No statistically significant difference was observed between the two groups for the values of ONSD. Fractional changes in ONSD at an altitude of 1,700 m were related to the development of AMS (r pb = 0.448, p = 0.019) and the presence of headache symptoms (r pb = 0.542, p = 0.004). The area under the ROC curve for the diagnostic performance of ONSD fractional changes at an altitude of 1,700 m was 0.859 for predicting the development of AMS and 0.803 for predicting the presence of headache symptoms. Conclusion: Analysis of changes in ONSD at moderate altitude could predict AMS symptoms before an ascent to high altitude. Myopia may impact physiological accommodation at high altitudes, and HM trekkers potentially demonstrate suboptimal regulation of aqueous humor in such environments.

The Effect of Esophagogastroduodenoscopy on Intraocular Pressure

BACKGROUND

Esophagogastroduodenoscopy (EGD) is an endoscopic examination of the upper gastrointestinal tract that requires insufflation with gas, leading to intra-abdominal hypertension (IAH). There is evidence suggesting that IAH positively correlates with intracranial pressure (ICP) and possibly with intraocular pressure (IOP). The aim of this study was to examine the effect of a routine screening EGD on the IOP.

METHODS

In this observational study, 25 patients were recruited; 15 males with a mean age of 50 ± 18 years and 10 females with a mean age of 45 ± 14 years. EGD was conducted under sedation in 21 subjects. Both eyes' IOP measurements were performed using Tonopen Avia in the sitting and left lateral decubitus positions before sedation and the start of EGD, and subsequently in the left lateral decubitus position when the endoscope reached the duodenum (D2) and at the end of the procedure. The final measurement was performed in the sitting position 10 min after the end of the procedure.

RESULTS

The mean IOP in the sitting position was 15.16 ± 2.27 mmHg, and in the left lateral decubitus position, 15.68 ± 2.82 mmHg. When the gastroscope entered the D2, it was 21.84 ± 6.55 mmHg, at the end of the procedure, 15.80 ± 3.25 mmHg, and 10 min later, 13.12 ± 3.63 mmHg. There was a statistically significant IOP increase when the gastroscope entered the duodenum (p < 0.01). At the end of the gastroscopy, the IOP significantly decreased compared to the one registered when the gastroscope entered the D2 (p < 0.001) and it became similar to the values measured before the EGD, in the same left lateral decubitus position (p > 0.05).

CONCLUSION

Significant changes in IOP were observed during the EGD. IOP fluctuations during EGD should be taken into account, especially in patients that need repeated EGDs during their life or in patients with glaucoma. Further studies are needed to better understand the short-effect and long-effect influence of an IOP increase in these patients.

Assessment of Optic Nerve Sheath Diameter in Patients Undergoing Endoscopic Retrograde Cholangiopancreatography: A Prospective, Randomized, Controlled Double-Blinded Comparison of Propofol and Ketofol Anesthesia

BACKGROUND

ERCP is an endoscopic procedure for the diagnosis and treatment of biliopancreatic system diseases. An increase in intra-abdominal pressure due to the insufflation of air to the intestinal lumen may be transmitted to ICP through the course of ERCP. In this prospective, randomized, controlled double-blinded study, we aimed to assess the ICP change using ultrasonography measurement of ONSD in patients undergoing ERCP comparing the effects of propofol and ketofol anesthesia.

MATERIAL/METHODS

One hundred and nine patients undergoing ERCP under propofol or ketofol anesthesia were enrolled in the study. Ultrasonography measurement of ONSD was performed before (T0) and immediately after induction of anesthesia (T1), during sphincterotomy (T2), at the end of procedure (T3), and after the patient is fully awake (T4).

RESULTS

Comparison of ONSD values and ONSD alteration between groups showed no statistically significant difference (P > 0.05). Both groups showed significantly greater changes from T0 to T2 compared with values from T0 to T1, T3, and T4, respectively (P = 0,000). T0 to T3 alteration was also significantly greater than T0 to T1 and T4 change in both groups (P = 0,000).

CONCLUSIONS

ERCP procedure increases intracranial pressure most prominently during sphincterotomy both under propofol or ketofol anesthesia. Further studies are needed to investigate the impact of this phenomenon on adverse clinical outcomes.

Reference values for trans-laminar cribrosa pressure difference and its association with systemic biometric factors

OBJECTIVES

To provide reference values of trans-laminar cribrosa pressure difference (TLCPD) and reveal the association of TLCPD with systemic biometric factors.

METHODS

In this cross-sectional study, 526 quasi-healthy subjects (including 776 eyes) who required lumbar puncture for medical reasons were selected from 4915 neurology inpatients from 2019 to 2022. Patients with any diseases affecting intraocular pressure (IOP) or intracranial pressure (ICP) were excluded. The ICPs of all subjects were obtained by lumbar puncture in the left lateral decubitus position. IOP was measured in the seated position by a handheld iCare tonometer prior to lumbar puncture. TLCPD was calculated by subtracting ICP from IOP. Systemic biometric factors were assessed within 1 h prior to TLCPD measurement.

RESULTS

The TLCPD (mean ± standard deviation) was 4.4 ± 3.6 mmHg, and the 95% reference interval (defined as the 2.5th-97.5th percentiles) of TLCPD was -2.27 to 11.94 mmHg. The 95% reference intervals for IOP and ICP were 10-21 and 6.25-15.44 mmHg, respectively. IOP was correlated with ICP (r = 0.126, p < 0.001). TLCPD was significantly negatively correlated with body mass index (r = -0.086, p = 0.049), whereas it was not associated with age, gender, height, weight, blood pressure, pulse, or waist and hip circumference.

CONCLUSIONS

This study provides reference values of TLCPD and establishes clinically applicable reference intervals for normal TLCPD. Based on association analysis, TLCPD is higher in people with lower BMI.

Association of intraocular pressure and postoperative nausea and vomiting after microvascular decompression - a prospective cohort study

BACKGROUND

Postoperative nausea and vomiting is common in patients receiving microvascular decompression. In the current study, we examined whether postoperative nausea and vomiting is associated with reduced intraocular pressure (IOP) after microvascular decompression, a measure that reflects intracranial pressure.

METHODS

This is a prospective cohort study. Adult patients scheduled for microvascular decompression surgery for hemifacial spasm between January 2020 and August 2020 were eligible. IOP was measured immediately before anesthesia induction and 30 min after patients regained complete consciousness using non-contact tonometry. IOP reduction was defined by at least 1 mmHg decrease vs. preoperative baseline. The primary outcome was vomiting on postoperative day 1.

RESULTS

A total of 103 subjects were enrolled. IOP was reduced in 56 (54.4%) subjects. A significantly greater proportion of patients with IOP reduction had vomiting on postoperative day 1 (51.8% (29/56) vs. 23.4% (11/47) in those without IOP reduction; p = 0.003). In the multivariate regression analysis, vomiting on postoperative day 1 was associated with female sex [odds ratio = 7.87, 95% CI: 2.35-26.32, p = 0.001] and IOP reduction [odds ratio = 2.93, 95% CI: 1.13-7.58, p = 0.027].

CONCLUSIONS

In patients undergoing microvascular decompression surgery, postoperative IOP reduction is associated with postoperative vomiting.

TRIAL REGISTRATION

Chinese Clinical Trial Registry: ChiCTR2000029083 . Registered 13 January 2020.

Intracranial pressure changes after mild traumatic brain injury: a systematic review

OBJECTIVE

Intracranial pressure (ICP) after mild traumatic brain injury (mTBI) is poorly studied due to lack of sensitive non-invasive methods. The purpose of this review was to summarize the existing knowledge of changes in ICP after mTBI. Literature selection: PubMed, Embase, CINAHL, and Scopus were searched by three reviewers independently up to December 2016.

INCLUSION CRITERIA

animal and human studies measuring ICP and brain oedema after an mTBI.

EXCLUSION CRITERIA

moderate and severe forms of traumatic brain injury, repeat samples, and studies that measured ICP at the time of impact but not after. Study quality was assessed using Downs and Black criteria.

RESULTS

Of 1067 papers, 9 studies were included. In human studies, one provided direct evidence on increased, one provided indirect evidence of increased, and two provided indirect evidence of decreased ICP. In animal studies, three studies provided direct evidence of increased, one provided indirect evidence of increased, and one provided indirect evidence of no change in ICP.

CONCLUSION

The existing research suggests that there may be increased ICP after mTBI and animal studies suggest an elevation for days which returns to baseline, which corresponds with functional and symptomatic recovery. Future human studies using sensitive indirect methods to measure ICP longitudinally after mTBI are needed.

Spaceflight-Induced Intracranial Hypertension and Visual Impairment: Pathophysiology and Countermeasures

Visual impairment intracranial pressure (VIIP) syndrome is considered an unexplained major risk for future long-duration spaceflight. NASA recently redefined this syndrome as Spaceflight-Associated Neuro-ocular Syndrome (SANS). Evidence thus reviewed supports that chronic, mildly elevated intracranial pressure (ICP) in space (as opposed to more variable ICP with posture and activity on Earth) is largely accounted for by loss of hydrostatic pressures and altered hemodynamics in the intracranial circulation and the cerebrospinal fluid system. In space, an elevated pressure gradient across the lamina cribrosa, caused by a chronic but mildly elevated ICP, likely elicits adaptations of multiple structures and fluid systems in the eye which manifest themselves as the VIIP syndrome. A chronic mismatch between ICP and intraocular pressure (IOP) in space may acclimate the optic nerve head, lamina cribrosa, and optic nerve subarachnoid space to a condition that is maladaptive to Earth, all contributing to the pathogenesis of space VIIP syndrome. Relevant findings help to evaluate whether artificial gravity is an appropriate countermeasure to prevent this seemingly adverse effect of long-duration spaceflight.

Translating the Low Translaminar Cribrosa Pressure Gradient Hypothesis into the Clinical Care of Glaucoma

Glaucoma is an optic neuropathy with multiple known risk factors, including age, race, family history, and intraocular pressure. Unfortunately, the only currently modifiable risk factor in treating the disease is intraocular pressure (IOP). Recent studies have investigated intracranial pressure (ICP) and the translaminar cribrosa pressure gradient as a potential explanation for glaucomatous optic nerve vulnerability across a range of IOP values. The difference between these two pressures across the lamina cribrosa may have an effect on the optic nerve, which could provide another modifiable parameter in the battle against glaucoma. In order for modification of the translaminar pressure gradient to be considered in the treatment of glaucoma, noninvasive methods to accurately measure ICP need to be developed. The translaminar pressure gradient could be therapeutically adjusted by either further lowering the IOP or raising the ICP when it is pathologically low, if possible.

Non-invasive intracranial pressure assessment

Assessing intracranial pressure (ICP) remains a cornerstone in neurosurgical care. Invasive techniques for monitoring ICP remain the gold standard. The need for a reliable, safe and reproducible technique to non-invasively assess ICP in the context of early screening and in the neurocritical care environment is obvious. Numerous techniques have been described with several novel advances. While none of the currently available techniques appear independently accurate enough to quantify raised ICP, there is some promising work being undertaken.

Intracranial pressure and glaucoma

Our understanding of the potential role intracranial pressure (ICP) may play in the pathophysiology of glaucoma is evolving. ICP can have a profound effect on the optic nerve; edema of the optic disc is an accepted consequence of elevation in ICP, and optic disc blood flow is known to be affected by ICP. Deformation of the orbit also is a known consequence of aberrations in ICP. Therefore, it is plausible that local alterations in optic nerve structure, blood supply, or axonal transport could result from changes in ICP. This article will summarize the relationship between ICP and the eye, specifically focusing on hypothesized relationships between ICP and glaucoma and the current evidence supporting or refuting ICP as a risk factor for glaucoma.

The increase of intra-abdominal pressure can affect intraocular pressure

Objective. This study aims to explore the usage of intraocular pressure measurements as the early indicator of the increase in intra-abdominal pressure. Methods. In this prospective study, 40 patients undergoing elective surgery were included. Patients were divided into four groups of 10 patients. The control group (Group C) was not subjected to laparoscopic intervention. Laparoscopic surgery was, respectively, performed with an intra-abdominal pressure of 9, 12, and 15 mmHg in Groups L (low), M (medium), and H (high pressure). Intraocular pressure was measured binocularly in each patient at three different times (before, during, and end of surgery) using a contact tonometer. Results. Patients' gender, age, body mass index (BMI), American Society of Anesthesiology (ASA) class, and operative times were not different among the groups. No complications occurred with either the surgery or measurement of intraocular pressure. Intubation was associated with a severe rise in IOP (P < 0.05). An increase in intraocular pressure was seen in groups M and H (P < 0.05). Conclusion. Intraocular pressure was increased in the groups with an intra-abdominal pressure of 12 mmHg or more. Measuring the intraocular pressure might be a useful method to estimate the intra-abdominal pressure. This trial is registered with NCT02319213.