Does Intraocular Pressure Increase During Laparoscopic Surgeries? It Depends on Anesthetic Drugs and the Surgical Position

The Effects of Lateral 45° Head-Down Position and Carbon Dioxide Pneumoperitoneum on the Optic Nerve Sheath Diameter in Patients Undergoing Laparoscopic Transperitoneal Nephrectomies: A Prospective Observational Study

Background: The aim of this study is to assess the extent of the increased intracranial pressure resulting from lateral decubitus and 45° downward positioning using sonographic optic nerve sheath diameter (ONSD) in patients undergoing laparoscopic transperitoneal nephrectomy. In addition, we evaluated the effect of the carbon dioxide pneumoperitoneum (CO₂PP) on ONSD. Materials and Methods: Twenty-four adults were enrolled in this prospective observational study. Longitudinal and transverse ONSDs were measured for each eye by ocular ultrasonography. The values were noted in supine position (T0), 20 minutes after induction of anesthesia (T1), after insufflation of the abdomen in lateral 45° head-down position (T2), at 30-minute intervals during surgery (T3-T4-T5), during lateral 45° head-down position after CO₂ exsufflation (T6), before awakening while supine (T7), and at postoperative 24th hour (T8). Hemodynamic and respiratory parameters were investigated at the measurement time points. Results: Average ONSD values for the lower eye was T0 = 4.27 ± 0.4 mm, T1 = 4.56 ± 0.6 mm, T2 = 4.84 ± 0.6 mm, T3 = 4.91 ± 0.4 mm, T4 = 4.99 ± 0.5 mm, T5 = 4.97 ± 0.5 mm T6 = 4.96 ± 0.5 mm, T7 = 4.76 ± 0.4 mm, T8 = 4.36 ± 0.5 mm and for the upper eye was T0 = 4.24 ± 0.4 mm, T1 = 4.39 ± 0.5 mm, T2 = 4.54 ± 0.5 mm, T3 = 4.60 ± 0.4 mm, T4 = 4.66 ± 0.4 mm, T5 = 4.72 ± 0.7 mm, T6 = 4.68 ± 0.4 mm, T7 = 4.52 ± 0.4 mm, T8 = 4.30 ± 0.4 mm (P < .001). Conclusion: In our study, we observed a significant increase in ONSD within minutes after the patient was placed in a head-down position. We also observed that the difference increased more with CO₂PP and was proportional to the length of the surgery. We found that it regressed to initial levels at the postoperative 24th hour. Clinicaltrials.gov: NCT05185908.

Effects of Positive End-Expiratory Pressure on Intraocular Pressure during One-Lung Ventilation in the Lateral Decubitus Position-A Prospective Randomized Trial

Background and Objectives: The effect of positive end-expiratory pressure (PEEP) on intraocular pressure (IOP) is debatable. There have been no studies investigating the effects of PEEP on IOP during one-lung ventilation (OLV). We aimed to investigate the effects of PEEP on IOP in patients undergoing OLV for video-assisted thoracoscopic surgery (VATs). Materials and Methods: Fifty-two patients undergoing VATs were divided into a zero-PEEP (ZEEP) and a 6 cmH₂O of PEEP (PEEP) groups. IOP, ocular perfusion pressure (OPP), and respiratory and hemodynamic parameters were measured before induction (T1), immediately following endotracheal intubation (T2), 30 min (T3) and 60 min (T4) after a position change to the lateral decubitus position (LDP) and OLV, and 10 min following two-lung ventilation near the end of the surgery (T5). Results: There was no significant difference in IOP and OPP between the two groups. The IOP of the dependent eye was significantly higher than that of the non-dependent eye during LDP in both groups. Peak inspiratory pressure was significantly higher in the PEEP group than in the ZEEP group at T3-T5. Dynamic compliance was significantly higher in the PEEP group than in the ZEEP group at T2-T5. The ratio of arterial oxygen partial pressure to fractional inspired oxygen was significantly higher in the PEEP group than in the ZEEP group at T4. Conclusions: Applying 6 cmH₂O of PEEP did not increase IOP but enhanced dynamic compliance and oxygenation during OLV. These results suggest that 6 cmH₂O of PEEP can be safely applied during OLV in LDP.

Laparoscopic gynaecological surgery in the context of maintaining normal intracranial pressure

A nulliparous patient in her early 20s was referred to a fertility specialist for fertility preservation, before commencing chemo-radiation therapy for a recently diagnosed malignant brain tumour. Two weeks prior, she had presented with seizures and undergone emergency craniotomy and tumour resection. Taking into consideration of the tight time frame and her comorbidities, several measures were undertaken to minimise the potential increase in intracranial pressure that may lead to cerebral oedema during laparoscopy. Preoperatively, the anaesthetist administered 8 mg dexamethasone as prophylaxis. Intraoperatively, the degree of head-down tilt was minimised to 10, which was just adequate to displace bowel cranially for visualisation of pelvic structures. Finally, a shorter operative time was achieved by ensuring the most senior surgeon performed the operation, and the procedure itself was altered from the standard approach of ovarian harvesting to unilateral oophorectomy. The patient made a quick recovery and was discharged home day 1 postoperatively.

Comparison of intraocular pressure during laparoscopic totally extraperitoneal (TEP) versus transabdominal preperitoneal (TAPP) inguinal hernia repair

BACKGROUND

Laparoscopic totally extraperitoneal (TEP) repair and transabdominal preperitoneal (TAPP) repair are standard laparoscopic procedures for inguinal hernia repair. Some evidence has shown that pneumoperitoneum can cause an increase in intraocular pressure (IOP) during surgery. This study aimed to compare intraoperative IOP following extraperitoneal CO₂ insufflation with the TEP approach and intraperitoneal CO₂ insufflation with the TAPP approach.

METHODS

This study is a prospective cohort study. Patients who had inguinal hernias suitable for laparoscopic inguinal hernia repair were assigned to undergo the TEP or TAPP approach. We measured preoperative, intraoperative, and postoperative IOP. The IOP of the TEP and TAPP groups was evaluated using a t test. The relations between peak inspiratory pressure (PIP), mean arterial pressure (MAP), and end-tidal CO₂ (EtCO₂) were estimated using ANOVA. Univariate and multivariate analyses were performed to determine the factors associated with IOP.

RESULTS

There were 50 patients in this study (TEP group n = 25, TAPP group n = 25). The change in intraoperative IOP from the preoperative measurement to the measurement after CO₂ insufflation was not statistically significant in either the TEP or TAPP group (p value = 0.357). There was no significant difference in intraoperative IOP change between the TEP and TAPP groups. Intraoperative MAP and PIP were related to IOP, but intraoperative EtCO2 was not.

CONCLUSIONS

There was no significant intraoperative IOP change during laparoscopic inguinal hernia repair. Both the TEP and TAPP techniques can be performed safely without increasing intraoperative IOP.

Attenuation of the increase in intraocular pressure with dexmedetomidine: Systematic review with meta-analysis and trial sequential analysis

STUDY OBJECTIVE

Whether dexmedetomidine effectively attenuates the increase in intraocular pressure (IOP) remains inconclusive. We aim to evaluate the effects of dexmedetomidine on IOP in adult patients undergoing surgery which requires general anesthesia and endotracheal intubation.

DESIGN

Systematic review and meta-analysis.

INTERVENTIONS

Intravenous administration of dexmedetomidine during surgery.

MEASUREMENTS

Intraocular pressure.

METHODS

We searched PubMed, Embase, Scopus, Web of Science, Cochrane Library, Google Scholar, Wanfang Data, and China National Knowledge Infrastructure from the inception through April 14, 2020. Randomized control trials which involved adult patients undergoing surgery that required general anesthesia and endotracheal intubation, which compared intravenous administration of dexmedetomidine with placebo regarding the IOP levels, which also provided sufficient information for meta-analysis were considered eligible.

MAIN RESULTS

Twenty-nine randomized control trials were included. The IOP levels are significantly lower in patients receiving dexmedetomidine after the administration of dexmedetomidine [mean difference (MD), -2.04 mmHg; 95% confidence interval (CI), -2.40 mmHg to -1.67 mmHg], after the injection of succinylcholine (MD, -3.84 mmHg; 95% CI, -4.80 mmHg to -2.88 mmHg), after endotracheal intubation (MD, -3.64 mmHg; 95% CI, -4.46 mmHg to -2.82 mmHg), after pneumoperitoneum (MD, -3.12 mmHg; 95% CI, -3.93 mmHg to -2.30 mmHg), and after the patients being placed in a steep Trendelenburg position (MD, -4.12 mmHg; 95% CI, -5.39 mmHg to -2.85 mmHg). Trial sequential analyses for these outcomes are conclusive.

CONCLUSIONS

Dexmedetomidine effectively attenuates the increase in IOP levels, and should be considered especially for at-risk patients.

Clinical Anatomy of the Extradural Neural Axis Compartment: A Literature Review

OBJECTIVE

The extradural neural axis compartment (EDNAC) is an adipovenous zone located between the meningeal and endosteal layers of the dura and has been minimally investigated. It runs along the neuraxis from the orbits down to the coccyx and contains fat, valveless veins, arteries, and nerves. In the present review, we have outlined the current knowledge regarding the structural and functional significance of the EDNAC.

METHODS

We performed a narrative review of the reported EDNAC data.

RESULTS

The EDNAC can be organized into 4 regional enlargements along its length: the orbital, lateral sellar, clival, and spinal segments, with a lateral sellar orbital junction linking the orbital and lateral sellar segments. The orbital EDNAC facilitates the movement of the eyeball and elsewhere allows limited motility for the meningeal dura. The major nerves and vessels are cushioned and supported by the EDNAC. Increased intra-abdominal pressure will also be conveyed along the spinal EDNAC, causing increased venous pressure in the spine and cranium. From a pathological perspective, the EDNAC functions as a low-resistance, extradural passageway that might facilitate tumor encroachment and expansion.

CONCLUSIONS

Clinicians should be aware of the extent and significance of the EDNAC, which could affect skull base and spine surgery, and have an understanding of the tumor spread pathways and growth patterns. Comparatively little research has focused on the EDNAC since its initial description. Therefore, future investigations are required to provide more information on this underappreciated component of neuraxial anatomy.

Intraoperative intraocular pressure changes during robot-assisted radical prostatectomy: associations with perioperative and clinicopathological factors

BACKGROUND

Steep Trendelenburg position (ST) during robot-assisted radical prostatectomy (RARP) poses a risk of increase in intraocular pressure (IOP) in men receiving robot-assisted radical prostatectomy (RARP). The aim of the study was to identify clinicopathological factors associated with increased IOP during RARP.

METHODS

We prospectively studied 59 consecutive prostate cancer patients without glaucoma. IOP was measured at 6 predefined time points before, during and after the operation (T1 to T6).

RESULTS

Compared with T1, IOP decreased after beginning of anesthesia(T2) (by - 6.5 mmHg, p < 0.05), and increased 1 h after induction of pneumoperitoneum in the steep Trendelenburg position (ST) (T3) (+ 7.3 mmHg, p < 0.05). IOP continued to increase until the end of ST (T4) (+ 10.2 mmHg, p < 0.05), and declined when the patient was returned to supine position under general anesthesia (T5) (T1: 20.0 and T5: 20.1 mmHg, p above 0.05). The console time affected the elevation of IOP in ST; IOP elevation during ST was more prominent in men with a console time of ≥4 h (n = 39) than in those with a console time of < 4 h (n = 19) (19.8 ± 6.3 and 15.4 ± 5.8 mmHg, respectively, p < 0.05). Of the 59 patients, 29 had a high baseline IOP (20.0 mmHg or higher), and their IOP elevated during ST was also reduced at T5 (T1: 22.6 and T5: 21.7 mmHg, p above 0.05). There were no postoperative ocular complications.

CONCLUSIONS

Console time of < 4 h is important to prevent extreme elevation of IOP during RARP. Without long console time, RARP may be safely performed in those with relatively high baseline IOP.

Attenuation of increased intraocular pressure with propofol anesthesia: A systematic review with meta-analysis and trial sequential analysis

Attenuation of an increase in intraocular pressure (IOP) is crucial to preventing devastating postoperative visual loss following surgery. IOP is affected by several factors, including the physiologic alteration due to pneumoperitoneum and patient positioning and differences in anesthetic regimens. This study aimed to investigate the effects of propofol-based total intravenous anesthesia (TIVA) and volatile anesthesia on IOP. We searched multiple databases for relevant studies published before October 2019. Randomized controlled trials comparing the effects of propofol-based TIVA and volatile anesthesia on IOP during surgery were considered eligible for inclusion. Twenty studies comprising 980 patients were included. The mean IOP was significantly lower in the propofol-based TIVA group after intubation, pneumoperitoneum, Trendelenburg positioning, and lateral decubitus positioning. Moreover, mean arterial pressure and peak inspiratory pressure were also lower after intubation in the propofol-based TIVA group. Trial sequential analyses for these outcomes were conclusive. Propofol-based TIVA is more effective than volatile anesthesia during surgery at attenuating the elevation of IOP and should be considered, especially in at-risk patients.

Changes of intraocular pressure and ocular perfusion pressure during controlled hypotension in patients undergoing arthroscopic shoulder surgery: A prospective, randomized, controlled study comparing propofol, and desflurane anesthesia

PURPOSE

The aim of the present study is to evaluate the effects of deliberate hypotensive anesthesia on intraocular pressure (IOP) and ocular perfusion pressure (OPP) and compare the effects of propofol total intravenous anesthesia (TIVA) and desflurane anesthesia on IOP and OPP.

METHODS

A total of 50 patients undergoing arthroscopic shoulder surgery in the lateral decubitus position were randomized to receive desflurane or propofol anesthesia. Mean arterial pressure (MAP) was maintained in the range of 60-75 mm Hg during hypotensive anesthesia. IOP was measured using a handheld tonometer at 7 time points: before induction (T1, baseline); immediately after endotracheal intubation (T2); 10 minutes after position change to lateral decubitus (T3); 10, 30, and 50 minutes after the start of hypotensive anesthesia (T4-T6); and at the end of surgery (T7).

RESULTS

MAP decreased about 35% to 38% during hypotensive anesthesia. Compared to baseline values, the IOP at T6 in dependent and non-dependent eyes decreased by 0.43 and 2.74 mm Hg, respectively in desflurane group; 3.61 and 6.05 mm Hg, respectively in the propofol group. IOP of both eyes in the propofol group was significantly lower than in the desflurane group from T2 to T7. OPP of both eyes in both groups was significantly lower than at baseline, except at T2 in the desflurane group. OPP of both eyes in the propofol group was significantly higher than that in the desflurane group at T5 and T6.

CONCLUSIONS

Hypotensive anesthesia reduced IOP and OPP, but propofol TIVA maintained higher OPP than desflurane anesthesia. These findings suggest that propofol TIVA can help mitigate the decrease of OPP during hypotensive anesthesia.

Variation in intraocular pressure caused by repetitive positional changes during laparoscopic colorectal surgery: a prospective, randomized, controlled study comparing propofol and desflurane anesthesia

Laparoscopic surgery is often prolonged and requires positional changes to facilitate surgical access. Previous studies reported intraocular pressure (IOP) changes in one fixed position. This study investigated the effect of desflurane and propofol anesthesia on IOP during repeated positional changes. A total of 46 patients undergoing laparoscopic colorectal surgery were randomized into desflurane or propofol groups. IOP was measured using a handheld tonometer at seven time points: before induction (baseline), after endotracheal intubation, after pneumoperitoneum, after the first Trendelenburg and right tilt position, after reverse Trendelenburg and right tilt position, after the second Trendelenburg and right tilt position and before endotracheal extubation. Trendelenburg positioning raised IOP in both groups. In the desflurane group, IOP at the first Trendelenburg position was 6.27 and 8.48 mmHg higher than baseline IOP in left and right eye, respectively; IOP at the second Trendelenburg position was 7 and 9.44 mmHg higher than baseline in left and right eye, respectively. In the propofol group, IOP at the first Trendelenburg position was 2.04 and 4.04 mmHg higher than baseline in left and right eyes, respectively. It was 3.04 and 4.87 mmHg higher than baseline in left and right eye, respectively, at the second Trendelenburg position. In the desflurane group, 56.52% patients exhibited high IOP (≥ 25 mmHg) compared with 13.04% in the propofol group at the second Trendelenburg position in the right eyes (P = 0.005). There was a positive correlation between IOP and peak inspiratory pressure (P < 0.001). Propofol anesthesia mitigated wide variations in IOP caused by repetitive positional changes during laparoscopic colorectal surgery.

Total intravenous anaesthesia versus inhalational anaesthesia for adults undergoing transabdominal robotic assisted laparoscopic surgery

BACKGROUND

Rapid implementation of robotic transabdominal surgery has resulted in the need for re-evaluation of the most suitable form of anaesthesia. The overall objective of anaesthesia is to minimize perioperative risk and discomfort for patients both during and after surgery. Anaesthesia for patients undergoing robotic assisted surgery is different from anaesthesia for patients undergoing open or laparoscopic surgery; new anaesthetic concerns accompany robotic assisted surgery.

OBJECTIVES

To assess outcomes related to the choice of total intravenous anaesthesia (TIVA) or inhalational anaesthesia for adults undergoing transabdominal robotic assisted laparoscopic gynaecological, urological or gastroenterological surgery.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2016 Issue 5), Ovid MEDLINE (1946 to May 2016), Embase via OvidSP (1982 to May 2016), the Cumulative Index to Nursing and Allied Health Literature (CINAHL) via EBSCOhost (1982 to May 2016) and the Institute for Scientific Information (ISI) Web of Science (1956 to May 2016). We also searched the International Standard Randomized Controlled Trial Number (ISRCTN) Registry and Clinical trials gov for ongoing trials (May 2016).

SELECTION CRITERIA

We searched for randomized controlled trials (RCTs) including adults, aged 18 years and older, of both genders, treated with transabdominal robotic assisted laparoscopic gynaecological, urological or gastroenterological surgery and focusing on outcomes of TIVA or inhalational anaesthesia.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures of Cochrane. Study findings were not suitable for meta-analysis.

MAIN RESULTS

We included three single-centre, two-arm RCTs involving 170 participants. We found one ongoing trial. All included participants were male and were undergoing radical robotic assisted laparoscopic radical prostatectomy (RALRP). The men were between 50 and 75 years of age and met criteria for American Society of Anesthesiologists physical classification scores (ASA) I, ll and III.We found evidence showing no clinically meaningful differences in postoperative pain between the two types of anaesthetics (mean difference (MD) in visual analogue scale (VAS) scores at one to six hours was -2.20 (95% confidence interval (CI) -10.62 to 6.22; P = 0.61) in a sample of 62 participants from one study. Low-quality evidence suggests that propofol reduces postoperative nausea and vomiting (PONV) over the short term (one to six hours after surgery) after RALRP compared with inhalational anaesthesia (sevoflurane, desflurane) (MD -1.70, 95% CI -2.59 to -0.81; P = 0.0002).We found low-quality evidence suggesting that propofol may prevent an increase in intraocular pressure (IOP) after pneumoperitoneum and steep Trendelenburg positioning compared with sevoflurane (MD -3.90, 95% CI -6.34 to -1.46; P = 0.002) with increased IOP from baseline to 30 minutes in steep Trendelenburg. However, it is unclear whether this surrogate outcome translates directly to clinical avoidance of ocular complications during surgery. No studies addressed the secondary outcomes of adverse effects, all-cause mortality, respiratory or circulatory complications, cognitive dysfunction, length of stay or costs. Overall the quality of evidence was low to very low, as all studies were small, single-centre trials providing unclear descriptions of methods.

AUTHORS' CONCLUSIONS

It is unclear which anaesthetic technique is superior - TIVA or inhalational - for transabdominal robotic assisted surgery in urology, gynaecology and gastroenterology, as existing evidence is scarce, is of low quality and has been generated from exclusively male patients undergoing robotic radical prostatectomy.An ongoing trial, which includes participants of both genders with a focus on quality of recovery, might have an impact on future evidence related to this topic.

What is the evidence for the use of low-pressure pneumoperitoneum? A systematic review

Background

Laparoscopic surgery has several advantages when compared to open surgery, including faster postoperative recovery and lower pain scores. However, for laparoscopy, a pneumoperitoneum is required to create workspace between the abdominal wall and intraabdominal organs. Increased intraabdominal pressure may also have negative implications on cardiovascular, pulmonary, and intraabdominal organ functionings. To overcome these negative consequences, several trials have been performed comparing low- versus standard-pressure pneumoperitoneum.

Methods

A systematic review of all randomized controlled clinical trials and observational studies comparing low- versus standard-pressure pneumoperitoneum.

Results and conclusions

Quality assessment showed that the overall quality of evidence was moderate to low. Postoperative pain scores were reduced by the use of low-pressure pneumoperitoneum. With appropriate perioperative measures, the use of low-pressure pneumoperitoneum does not seem to have clinical advantages as compared to standard pressure on cardiac and pulmonary function. Although there are indications that low-pressure pneumoperitoneum is associated with less liver and kidney injury when compared to standard-pressure pneumoperitoneum, this does not seem to have clinical implications for healthy individuals. The influence of low-pressure pneumoperitoneum on adhesion formation, anastomosis healing, tumor metastasis, intraocular and intracerebral pressure, and thromboembolic complications remains uncertain, as no human clinical trials have been performed. The influence of pressure on surgical conditions and safety has not been established to date. In conclusion, the most important benefit of low-pressure pneumoperitoneum is lower postoperative pain scores, supported by a moderate quality of evidence. However, the quality of surgical conditions and safety of the use of low-pressure pneumoperitoneum need to be established, as are the values and preferences of physicians and patients regarding the potential benefits and risks. Therefore, the recommendation to use low-pressure pneumoperitoneum during laparoscopy is weak, and more studies are required.

Ocular Complications in Laparoscopic Surgery: Review of Existing Literature and Possible Prevention and Treatment

During laparoscopic surgery, ocular complications are possible, sometimes leading to devastating visual losses, hardly susceptible to recovery, although rare. Principal ocular adverse events are represented by corneal abrasions and the perioperative visual loss (POVL). POVL onset is related to intraocular pressure elevations (particularly after patient positioning in Trendelenburg or prone decubitus, depending on the surgical procedure), anesthesiologic factors and patients' characteristics. In the light of evidence from the existing literature, the authors suggest surgical and anesthesiologic measures to prevent and manage ocular complications in laparoscopic surgery. Apart from general recommendations, this article indicates practical guidelines specific for robot-assisted laparoscopic interventions and spinal surgery, as well as laparoscopic colorectal resection, radical prostatectomy, and gynecologic surgery. In conclusion, in order to better manage these complications, it is advisable to develop an interdisciplinary collaboration between surgeons, anesthesiologists, and ophthalmologists, on a procedural and medico-legal level, with the intent of mutual training.

The effect of the modified Z trendelenburg position on intraocular pressure during robotic assisted laparoscopic radical prostatectomy: a randomized, controlled study

PURPOSE

The Trendelenburg position has a dramatic effect on circulation, consequently increasing cerebral and intraocular pressure. We evaluated whether modifying the Trendelenburg position would minimize the increase in intraocular pressure.

MATERIALS AND METHODS

In this prospective, randomized, controlled study we compared intraocular pressure in patients undergoing robot-assisted laparoscopic radical prostatectomy while in the Trendelenburg position or the modified Z Trendelenburg position. In group 1 intraocular pressure, blood pressure and endotracheal CO2 were measured in the patient at anesthesia induction (time 1), before positioning (time 2), and while in the Trendelenburg position (time 3) and in the modified Z Trendelenburg position (time 4). They were also measured after pneumoperitoneum (time 5), every 30 minutes (times 6 to 16), while supine at the end of pneumoperitoneum (time 17) and before awakening (time 18). We modified the Trendelenburg position by placing the head and shoulders horizontally.

RESULTS

Group 1 included 29 patients in the modified Z Trendelenburg position. Group 2 included 21 patients in the Trendelenburg position. No difference was found in patient demographics or surgical outcomes. Median intraocular pressure was in the low normal range at times 1 and 2, and increased in time 3 in each group. From time 4 intraocular pressure decreased and at all time points it was significantly lower in group 1 by a mean of 4.61 mm Hg (95% CI -6.90-2.30, p <0.001). At time 17 mean intraocular pressure decreased to normal (19.6 mm Hg) in group 1 but remained in the hypertensive range (24.9 mm Hg) in group 2. At time 18 mean intraocular pressure was 17 mm Hg in each group. Blood pressure was significantly lower in group 1 with a mean reduction in systolic and diastolic pressure of 6.3 and 4.3 mm Hg, respectively.

CONCLUSIONS

Our results suggest that modifying the Trendelenburg position during robot-assisted laparoscopic radical prostatectomy has a significant positive effect on patient neuro-ocular safety by lowering intraocular pressure and accelerating its recovery to the normal range without affecting the operation.