Autoregulation of human optic nerve head circulation in response to increased intraocular pressure

The retinal venous pressure at different levels of airway pressure measured with a new method

PURPOSE

This study is to investigate the increase in retinal venous pressure (RVP) induced by a stepwise increase in airway pressure (AirP) using the new IOPstim method, which is designed to artificially increase the intraocular pressure (IOP) and thus to stimulate vascular pulsation.

METHODS

Twenty-eight healthy subjects were examined in the left eye. The RVP was measured at baseline and at four different levels of AirP (10, 20, 30, and 40 mmHg) using the new IOPstim method: a half balloon of 8 mm diameter is inflated laterally to the cornea under observation of the central retinal vein. As soon as the vein pulsates at a certain AirP level, the IOP is measured with a commercially available tonometer, which then corresponds to the RVP.

RESULTS

Spontaneous venous pulsation was observed in all study participants. The mean RVP values at baseline and at the AirP levels of 10, 20, 30, and 40 mmHg were 17.6 ± 2.8 mmHg; 20.1 ± 3.0 mmHg; 22.1 ± 3.5 mmHg; 24.3 ± 3.7 mmHg, and 26.6 ± 4.2 mmHg, respectively. The mean RVP values of each AirP level were statistically significantly different from each other in pairwise comparison. In a linear mixed model, the effect of AirP on RVP was highly significant (p < 0.001). In the model, a 10-mmHg increase in AirP resulted in a linear increase in RVP of 2.2 mmHg.

CONCLUSION

An increase in AirP was accompanied by a linear increase in RVP. The influence of AirP on RVP, and thus on retinal perfusion pressure during the Valsalva maneuver, is less than was assumed based on previous studies in which contact lens dynamometry was used.

A prospective observation of influence of anti-VEGF on optic disc vasculature in nAMD patients

BACKGROUND

This study aims to investigate the short-term changes in relatively normal retinal vessels following anti-vascular endothelial growth factor (anti-VEGF) therapy in nAMD patients, an area that currently represents a research gap.

METHODS

In this prospective study, we enrolled patients newly diagnosed with neovascular age-related macular degeneration (nAMD) and received standardized monthly anti-VEGF therapy for three months. Follow-ups were conducted at baseline and 1-week, 1-month, 2-months and 3-months post first injection. Assessment indicators included radial peripapillary capillary vascular density (RPC-VD) and retinal nerve fiber layer (RNFL) thickness in different optic disk regions using optical coherence tomography angiography, as well as intraocular pressure (IOP).

RESULTS

68 nAMD patients (68 eyes) were included in this study. Significant reductions of RPC-VD and increases of RNFL thickness primarily in the nasal regions were observed 1-week post anti-VEGF (adjusted P < 0.05). Significant negative correlations were found between 1-week changes in RPC-VD and RNFL thickness in the nasal sectors (P < 0.05). From 1 to 3 months post-injection, RPC-VD and RNFL thickness essentially returned to baseline levels. Throughout the follow-up periods, IOP remained stable (P > 0.05).

CONCLUSION

Anti-VEGF treatments transiently influence the relatively normal retinal vessels, which might lead to nerve fiber edema, predominantly on the nasal side of the optic disk.

The effect of a brinzolamide/brimonidine fixed combination on optic nerve head blood flow in rabbits

PURPOSE

The purpose of this study was to investigate the effect of a 1% brinzolamide and 0.1% brimonidine fixed combination (BBFC) on ONH blood flow (BF) in rabbits.

METHODS

A crossover study was conducted on pigmented rabbits; a physiological saline solution, brinzolamide, or BBFC was administered for eight days. ONH BF, intraocular pressure (IOP) and systemic parameters were measured before the eighth day's first dose and at 6, 9, 12, and 14 hours after the dose. ONH BF was assessed using laser speckle flowgraphy, and mean blur rate (MBR) values were calculated. The percentage against baseline of each parameter was calculated, and intergroup comparisons were performed at each time point.

RESULTS

There were no significant differences in the percentage change in systemic parameters. At 6 hours after administration, the BBFC group showed a significantly higher percentage change in large vessel area-MBR (%MV) compared to the control group (98.6±16.8%MV vs. 81.3±7.9%MV, P = 0.03). On the other hand, the brinzolamide group did not show a significant difference. Both the brinzolamide and BBFC groups had significantly lower percentage change in IOP (%IOP) compared to the control group (90.6±5.0%IOP, 93.3±2.9%IOP, and 99.2±1.7%IOP, respectively, P < 0.01).

CONCLUSION

BBFC effectively reduces IOP and mitigates diurnal fluctuation-induced decreases in ONH BF.

Neurovascular dysfunction in glaucoma

Retinal ganglion cells, the neurons that die in glaucoma, are endowed with a high metabolism requiring optimal provision of oxygen and nutrients to sustain their activity. The timely regulation of blood flow is, therefore, essential to supply firing neurons in active areas with the oxygen and glucose they need for energy. Many glaucoma patients suffer from vascular deficits including reduced blood flow, impaired autoregulation, neurovascular coupling dysfunction, and blood-retina/brain-barrier breakdown. These processes are tightly regulated by a community of cells known as the neurovascular unit comprising neurons, endothelial cells, pericytes, Müller cells, astrocytes, and microglia. In this review, the neurovascular unit takes center stage as we examine the ability of its members to regulate neurovascular interactions and how their function might be altered during glaucomatous stress. Pericytes receive special attention based on recent data demonstrating their key role in the regulation of neurovascular coupling in physiological and pathological conditions. Of particular interest is the discovery and characterization of tunneling nanotubes, thin actin-based conduits that connect distal pericytes, which play essential roles in the complex spatial and temporal distribution of blood within the retinal capillary network. We discuss cellular and molecular mechanisms of neurovascular interactions and their pathophysiological implications, while highlighting opportunities to develop strategies for vascular protection and regeneration to improve functional outcomes in glaucoma.

Efficacy of selective laser trabeculoplasty on lowering intraocular pressure fluctuations and nocturnal peak intraocular pressure in treated primary open-angle glaucoma patients

Purpose

To investigate the efficacy of adjunctive selective laser trabeculoplasty (SLT) in reducing 24-h intraocular pressure (IOP) fluctuations and nocturnal IOP peaks.

Methods

In this prospective interventional case series, 157 medically treated eyes of 157 patients with primary open-angle glaucoma (POAG) who were assigned SLT to further reduce IOP were consecutively included. Each patient had a complete glaucoma work-up and 24-h IOP monitoring (6 measurements, including one in the supine position) taken before and on average 6 months after SLT. The main outcome measures were the reduction of 24-h IOP fluctuations and nocturnal peak IOP. Secondary outcome measures were success rates, factors influencing the reduction of high 24-h IOP fluctuations and nocturnal peak IOP, complications, and severe adverse events.

Results

Medicated mean 24-h IOP (mmHg) was statistically significantly reduced from 15.1 ± 2.6 to 13.8 ± 2.4 (P < 0.001) and IOP fluctuations from 6.5 ± 2.7 to 5.4 ± 2.6 (P < 0.001) 6 months after SLT. Ninety-four eyes (59.9%) initially had high IOP fluctuations (more than 5 mmHg). These were reduced from 8.1 ± 2.3 to 5.6 ± 2.7 at 6 months (P < 0.001). Fifty-two eyes (55.3%) had fluctuations below 5 mmHg post-SLT which was defined as success. Fifty-one patients (32.5%) had nocturnal IOP peaks. In these cases, nocturnal IOP was reduced by 19.2% from 20.1 ± 3.4 to 16.2 ± 3.3 mmHg at 6 months (P = 0.001).

Conclusions

The current study demonstrates that adjunctive SLT not only reduces mean 24-h IOP in treated POAG patients, but also has an additional benefit in reducing IOP fluctuations and nocturnal peak IOP.

Trial registration

Clinical trial registration: NCT02959242.

Perioperative Care of the Patient with Eye Pathologies Undergoing Nonocular Surgery

The authors reviewed perioperative ocular complications and implications of ocular diseases during nonocular surgeries. Exposure keratopathy, the most common perioperative eye injury, is preventable. Ischemic optic neuropathy, the leading cause of perioperative blindness, has well-defined risk factors. The incidence of ischemic optic neuropathy after spine fusion, but not cardiac surgery, has been decreasing. Central retinal artery occlusion during spine fusion surgery can be prevented by protecting eyes from compression. Perioperative acute angle closure glaucoma is a vision-threatening emergency that can be successfully treated by rapid reduction of elevated intraocular pressure. Differential diagnoses of visual dysfunction in the perioperative period and treatments are detailed. Although glaucoma is increasingly prevalent and often questions arise concerning perioperative anesthetic management, evidence-based recommendations to guide safe anesthesia care in patients with glaucoma are currently lacking. Patients with low vision present challenges to the anesthesia provider that are becoming more common as the population ages.

Evaluation of Macular and Peripapillary Blood Flow in Response to Intraocular Pressure Reduction in Patients With Posner-Schlossman Syndrome

Purpose: The study aimed to evaluate the effect of intraocular pressure (IOP) reduction on macular and peripapillary microcirculation in patients with Posner-Schlossman syndrome (PSS) by optical coherence tomography angiography (OCTA). Methods: A prospective comparative study was conducted. Patients diagnosed with PSS at the Eye Center of Xiangya Hospital, Central South University, from February 2020 to November 2021 were consecutively included. OCTA was used for the macular and peripapillary microcirculation measurements, and optical coherence tomography (OCT) was employed for the retinal nerve fiber layer (RNFL) and lamina cribrosa depth (LCD) measurements. The patients received OCT and OCTA examinations at baseline and 1 week post-treatment when the IOP was under control. Changes in macular and peripapillary microcirculation, RNFL, and LCD were calculated for all the analyzed areas. Results: Twenty-one eyes from 21 patients were included in the study. Pre-treatment and post-treatment IOP were 43.17 ± 10.36 mm Hg (range, 30-60 mm Hg) and 17.17 ± 2.85 mm Hg (range, 13-23 mm Hg), respectively. No statistically significant changes were detected in RNFL, LCD, or macular and peripapillary microcirculation after significant IOP reduction. Conclusion: The results suggested that a large IOP reduction may not result in a significant increase in peripapillary and macular capillary perfusion in patients with PSS.

Transient Visual Loss in Young Females with Crowded Optic Discs: A Proposed Aetiology

I present four cases of transient visual loss (TVL) in young females with crowded optic discs. One patient had asymmetrical cup-to-disc ratios and only experienced TVL in the eye with the more crowded disc. I review the evidence for blood flow autoregulatory dysfunction within crowded optic discs in combination with reduced ocular perfusion pressure to propose a possible aetiology for both unilateral and bilateral TVL in young females with crowded optic discs.

Diurnal Variation of Retinal Vessel Density in Healthy Human Eyes

PRECIS

A small increase in optic nerve head vessel density (VD), but not macular VD, in the evening compared with the morning is observed in healthy subjects.

PURPOSE

To evaluate the diurnal variation of the macular and optic nerve head (ONH) VD in healthy eyes as measured with optical coherence tomography angiography (OCT-A).

METHODS

In this prospective study of healthy individuals older than 18 years old, VD parameters, including macular whole image vessel density, parafoveal vessel density, ONH whole image vessel density, ONH whole image capillary density, circumpapillary vessel density (cpVD), and circumpapillary capillary density, were measured with OCT-A at 4 time points throughout the day (8 am, 12 pm, 4 pm, and 8 pm).

RESULTS

Twenty-nine healthy eyes were included from 15 subjects (mean age: 30.9 y). After adjustment for age and mean ocular perfusion pressure, a significant positive rate of change was found for cpVD (0.05%/h; P=0.027). In contrast, macular VD changes were not significantly different. When comparing morning (8 am and 12 pm) and evening (4 pm and 8 pm) measurements, there were small, but statistically significant, increases for all ONH measurements. The greatest increase was found for cpVD (0.58%; P=0.022). Significant but small increases in mean arterial pressure and mean ocular perfusion pressure were also observed.

CONCLUSIONS

There was a small increase in ONH VD, but not macular VD, in the evening compared with the morning in healthy human eyes. As the observed difference was within the measurement variability, our results suggest the timing of OCT-A examination does not affect retinal VD measurements.

Changes in pulse waveforms in response to intraocular pressure elevation determined by laser speckle flowgraphy in healthy subjects

Background

The influences of intraocular pressure (IOP) elevations on the pulse waveform in the optic nerve head (ONH) were evaluated using laser speckle flowgraphy (LSFG) in normal subjects.

Methods

This prospective cross-sectional study was conducted at the Nagoya University Hospital. An ophthalmodynamometer was pressed on the sclera to increase the IOP by 20 mmHg or 30 mmHg for 1 min (experiment 1, 16 subjects) and by 30 mmHg for 10 min (experiment 2, 10 subjects). The mean blur rate (MBR) and the eight pulse waveform parameters determined using LSFG were measured before, immediately after and during an IOP elevation, and after the IOP returned to the baseline pressure.

Results

A significant elevation in the IOP and a significant reduction in the ocular perfusion pressure (OPP) were found after applying the ophthalmodynamometer (both, P < 0.001). The blowout score (BOS) reduced significantly (P < 0.001), and the flow acceleration index (FAI; P < 0.01) and resistivity index (RI; P < 0.001) increased significantly immediately after increasing the IOP by 20 or 30 mmHg (experiment 1). The BOS reduced significantly (P < 0.001), and the FAI (P < 0.01) and RI (P < 0.001) increased significantly after the IOP elevation by 30 mmHg in both experiment 2 and 1. However, the BOS and RI recovered significantly at time 10 compared to that in time 0 (immediately after IOP elevation) during the 10-min IOP elevation (P < 0.001 and P = 0.008, respectively).

Conclusions

In conclusion, the BOS, FAI, and RI of the pulse waveforms changed significantly with an acute elevation in the IOP. The change should be related to the larger difference between the maximum and minimum MBRs during the IOP elevation.

Ocular Outcomes in Healthy Subjects Undergoing a Short-Term Head-Down Tilt Test

PURPOSE: This study aimed to examine the effect of head-down tilt (HDT) on vascular autoregulation in different age groups and determine its effects on intraocular pressure (IOP) and central corneal thickness (CCT).METHODS: Included were 43 eyes of 23 men. The optic nerve head and parafoveal vascular densities were measured by optical coherence tomography angiography before and after 20 min 10 HDT. Also, the study comprised an examination of the IOP and CCT in a subset of 8 participants (14 eyes) in the sitting position and during 15 min of 10 HDT.RESULTS: Grid-based inside disc all-vessel density (GBID) was statistically significantly lower after the HDT test in subjects under 30 yr (1.26). Whole image and peripapillary capillary vessel density (WICVD, PCVD), and whole image and peripapillary all-vessel density (WIAVD, PAVD) were significantly higher after the HDT test in subjects ages 30-39 yr (1.34, 2.16, 1.05, 1.72, respectively). Inside disc capillary, all-vessel density (IDCVD, IDAVD) and GBID were significantly higher after HDT in subjects over 40 yr (2.48, 2.15, 1.52, respectively). In a subset of eight participants, IOP was significantly higher (3.7 mmHg) and CCT was unchanged after 15 min of HDT.CONCLUSION: Our study showed that simulated microgravity induced optic nerve head vessel density at the inside disc area, especially in persons over 40 years. In addition, IOP was increased by HDT, although no change in CCT was observed.Özelbaykal B, Öğretmenoğlu G, Tunçez I.H. Ocular outcomes in healthy subjects undergoing a short-term head-down tilt test. Aerosp Med Hum Perform. 2021; 92(8):619-626.

[Vasculat treatment concepts in glaucoma patients]

BACKGROUND

Approximately 40% of all open-angle glaucomas do not show high intraocular pressure (IOP). Vascular risk factors play an important role in the pathogeneses of normal pressure glaucoma but high pressure glaucoma is also often accompanied by significant vascular components.

OBJECTIVE

What are the practice relevant possibilities of vascular glaucoma treatment?

MATERIAL AND METHODS

An evaluation of scientific articles from PubMed dealing with vascular glaucoma was carried out.

RESULTS

The treatment of vascular risk factors in glaucoma patients requires a thorough medical history regarding vascular symptoms (peripheral vasospasm, tinnitus, migraine etc.) and information on the presence of systemic diseases. Furthermore, a 24h blood pressure profile and the determination of the fat metabolism status represent important and simple examinations.

CONCLUSION

Besides optimizing systemic blood pressure, reducing an increased central retinal venous pressure, treatment with statins, calcium channel blockers, Ginkgo biloba extract, increased physical exercise and fluid replacement are options to ameliorate vascular conditions. An interdisciplinary cooperation with general practitioners and internists is an important component of holistic treatment.

Associating the biomarkers of ocular blood flow with lamina cribrosa parameters in normotensive glaucoma suspects. Comparison to glaucoma patients and healthy controls

Purpose

To evaluate association between ocular blood flow biomarkers and lamina cribrosa parameters in normotensive glaucoma suspects compared to glaucoma patients and healthy controls.

Methods

A total of 211 subjects (72 normotensive glaucoma suspects, 70 with primary open-angle glaucoma and 69 controls) were included. Ocular blood flow biomarkers in ophthalmic artery, central retinal artery, as well as in nasal and temporal short posterior ciliary arteries were measured using colour Doppler imaging. Lamina cribrosa position was assessed by measuring its depth, deflection depth, lamina cribrosa shape index and its horizontal equivalent (LCSI_H) on B-scan images obtained using optical coherence tomography.

Results

Ocular blood flow biomarkers in glaucoma patients were statistically significantly reduced when compared to healthy controls in peak systolic velocity (PSV) (P = 0.001 in ophthalmic artery and P<0.001 in central retinal artery) and mean flow velocity (V_m) (P = 0.008 in ophthalmic artery and P = 0.008 in central retinal artery), but not statistically significantly different to that of glaucoma suspects except for PSV in central retinal artery (P = 0.011). Statistically significant correlations corrected for age, central corneal thickness and intraocular pressure were found in glaucoma patients between LCSI_H and end diastolic velocity of central retinal artery (P = 0.011), and of nasal short posterior ciliary artery (P = 0.028), and between LCSI_H and V_m of central retinal artery (P = 0.011) and of nasal short posterior ciliary artery (P = 0.007). No significant correlations were observed between these parameters in glaucoma suspects and healthy controls.

Conclusions

Impaired ocular blood flow associated with the deformation of lamina cribrosa was found in glaucoma patients, whereas glaucoma suspects had similar lamina cribrosa shape to glaucoma patients but that deformation was not associated with ocular blood flow biomarkers.

Evaluating Retinal and Choroidal Perfusion Changes After Ocular Massage of Healthy Eyes Using Optical Coherence Tomography Angiography

Background and objectives: Ocular massage (OM) is used as a treatment option for acute retinal artery occlusion, under the assumption that it induces vessel dilatation and enhances perfusion. Since evidence of ocular perfusion alteration due to OM is lacking, we investigate the impact of OM on the hemodynamics of the posterior pole in healthy eyes in a noninvasive fashion by using optical coherence tomography angiography (OCTA). Materials and Methods: A prospective study was conducted on healthy volunteers, each of whom underwent measurements of intraocular pressure (IOP), central macular thickness (CMT), subfoveal choroidal thickness (SFCT), radial peripapillary capillary perfusion (RPCP), superficial capillary plexus perfusion (SCPP), deep capillary plexus perfusion (DCPP), choriocapillaris perfusion (CCP), Sattler’s layer perfusion (SLP) and Haller’s layer perfusion (HLP) before and after OM. OM was performed for 2 min, consisting of 10-s turns of compression and decompression of the globe. Results: A total of 21 eyes from 21 participants (median age 29) were included. After OM, IOP significantly declined (p < 0.001), while SFCT (p < 0.005), SCPP (p < 0.001), DCPP (p = 0.004) and CCP (p = 0.008) significantly increased. CMT, RPCP, SLP and HLP did not show any significant alteration due to OM. Changes in SCPP correlated positively with changes in CCP and vice versa. Conclusions: OCTA-based analysis in healthy adults following OM demonstrated a significant increase of retinal perfusion values, assumed to be due to failure of autoregulatory mechanisms. These findings may indicate a positive effect of OM as a treatment option for patients with acute retinal artery occlusion.

Changes in Retinal Blood Flow in Response to an Experimental Increase in IOP in Healthy Participants as Assessed With Doppler Optical Coherence Tomography

Purpose

Blood flow autoregulation is an intrinsic mechanism of the healthy retinal vasculature to keep blood flow constant when ocular perfusion pressure (OPP) is changed. In the present study, we set out to investigate retinal blood flow in response to an experimental decrease in OPP in healthy participants using Doppler optical coherence tomography.

Methods

Fifteen healthy participants aged between 22 and 31 years (mean, 27 ± 3 years) were included in the present open study. IOP was increased stepwise via the suction cup method to induce a decrease in OPP. Retinal blood flow in arteries and veins was assessed using a custom-built Doppler optical coherence tomography system and pressure–flow relationships were calculated to assess autoregulation.

Results

Suction cup application induced a pronounced increase in IOP with a maximum value of 50.5 ± 8.0 mm Hg at the highest level of suction. Pressure–flow relationships revealed that blood flow was autoregulated until the OPP was decreased by approximately 21 mm Hg and started to decrease significantly when the OPP was reduced by 30 mm Hg. Retinal blood flow at the last suction period decreased at a maximum of –57.0 ± 22.3% and 65.2 ± 15.4% in retinal arteries and retinal veins, respectively. These changes in retinal blood flow were less pronounced than the decrease in OPP (–75.2 ± 19.2%), indicating retinal autoregulation.

Conclusions

The results of the present study confirm that retinal blood flow is autoregulated in response to changes in the OPP. Doppler optical coherence tomography has the potential to become a clinical tool for the investigation of retinal blood flow autoregulation in the future, because of its ability to assess the blood velocities and diameter of the retinal vessels parallel and therefore also their blood flow in absolute values. (Clinicaltrials.gov number NCT03398616)

Systematic Review and Meta-Analysis of Prone Position on Intraocular Pressure in Adults Undergoing Surgery

BACKGROUND

Patients undergoing surgery in the prone position may be at risk for postoperative vision loss associated with increased intraocular pressure. The purpose of this systematic review and meta-analysis is to estimate the magnitude of the increase in intraocular pressure at specific perioperative time points in adult patients. The research question to be addressed is "What is the magnitude of the increase in intraocular pressure at specific perioperative time points in adults undergoing surgery in the prone position?"

METHODS

Comprehensive search strategies were used to identify nine eligible studies (N = 229). Standardized mean difference effect sizes were calculated for two intraoperative time points.Time points for meta-analysis were selected to achieve the greatest number of comparisons for analysis at each time point. Prediction intervals for each time point were also calculated to show the dispersion of true effect sizes around the mean.

RESULTS

Meta-analysis showed that intraocular pressure increased significantly between induction of anesthesia and up to 10 minutes of prone position (T1: standardized mean difference [d] = 2.55; P < .001) and continued to increase significantly until the end of the prone position (T2: d = 3.44; P = .002).

CONCLUSIONS

Intraocular pressure increases of this magnitude demonstrate the need for implementing interventions to reduce the risk for postoperative vision loss in patients undergoing surgery in the prone position.

CLINICAL RELEVANCE

Implementing preoperative ophthalmologic examinations for patients undergoing surgery in the prone position may help to reduce the risk for ocular injury. Intraoperative interventions that can be implemented to reduce or mitigate the increase in intraocular pressure include implementing a 5- to 10-degree reverse Trendelenburg prone position, reducing the amount of time the patient is in the prone position, considering staged procedures, monitoring intraocular pressure, providing periodic position changes or rest periods, preventing pressure on the eye, and administering specific medications or anesthetics.

Immediate Changes in Peripapillary Retinal Vasculature after Intraocular Pressure Elevation -an Optical Coherence Tomography Angiography Study

Purpose: To investigate changes in peripapillary retinal vessel density after acute intraocular pressure (IOP) elevation caused by laser peripheral iridotomy (LPI) in primary angle-closure suspects (PACS) by optical coherence tomography angiography (OCTA).Materials and Methods: Ninety-seven participants with PACS were included in this cross-sectional observational study. OCTA and IOP measurement were performed at baseline and 1 h after LPI. PACS eyes were further divided into three groups according to IOP increase 1 h after LPI (group 1 = IOP elevation <5 mmHg, 42eyes; group 2 = IOP elevation ≥5 mmHg and <10 mmHg, 34 eyes; group 3 = IOP elevation ≥10 mmHg, 21eyes). The changes of vessel density in radial peripapillary capillary (RPC) and entire retina were compared among groups.Results: When all eyes were included, the vessel density of RPC and entire retina 1 h after LPI were significantly decreased compared to the baseline (RPC: 64.5 ± 7.9 vs.67.8 ± 6.8, P < .001; retina: 86.3 ± 4.6 vs.88.3 ± 3.8, P < .001). There were significant differences among the three groups in the RPC and retinal vessel density at 1 h after LPI (RPC: 67.4 ± 7.3 vs. 63.2 ± 7.6 vs. 60.9 ± 7.5, P = .003; retinal: 87.7 ± 4.0 vs. 85.8 ± 4.5 vs. 84.3 ± 5.2, P = .015). In group 2 with an increased IOP from 5 mmHg to 10 mmHg, the reduction of vessel density in the RPC was more significant than that of the entire retina (RPC vs. retina: 7.1 ± 10.0% vs. 3.0 ± 4.4%, P = .006).Conclusions: LPI-induced IOP spikes resulted in a decrease in retina vessel density with PACS eyes by OCTA. The reduction of RPC vessel density was more significant than that of the entire retina in the subgroup of IOP increase from 5 to 10 mmHg. This suggests that vessel density in RPC was more sensitive to IOP increase than that of the entire retina in the peripapillary area.

Clinical Signs and Intraocular Pressure Changes in Patients with Orbitozygomatic Complex Fractures

Objectives

The study investigated the association between intraocular pressure changes and clinical ocular signs in 51 patients with orbitozygomatic complex fractures. Diplopia, chemosis, enophthalmos, subconjunctival haemorrhage, periorbital ecchymosis and extraocular muscles entrapment were assessed.

Study Design

Intraocular pressure was measured in mmHg at different time intervals with Perkins and Goldman tonometers; within first 3 days of injury (T1), 24 h post-elevation within 3-14 days of injury (T2), 1 month after initial treatment assessment (T3), 2 months after initial treatment assessment (T4), and 3 months after initial treatment assessment (T5). Intraocular pressure changes between T2/T1 and T3/T1 were analysed as change 1 and change 2, respectively, with paired t test. Significance was set at p < 0.05.

Results

Minimum intraocular pressure recorded in the affected eye was 5 mmHg at T1 and T2, while maximum intraocular pressure was 28 mmHg at T1. Mean intraocular pressure at T1 and T2 was 15.90 ± 4.73 mmHg and 16.80 ± 4.43 mmHg, respectively. All eye signs had completely resolved at T3 except enophthalmos, which persisted till T5. Statistical significant relationship exist between orbitozygomatic complex fracture and enophthalmos (T1: p = 0.04). subconjunctival haemorrhage (T2: p = 0.003), periorbital ecchymosis (T2: p = 0.005),and T3: p = 0.001).

Conclusion

Chemosis, diplopia, enophthalmos, periorbital ecchymosis and subconjunctival haemorrhage showed positive contributory effect to intraocular pressure elevation in orbitozygomatic complex fracture.

Regulation of Choroidal Blood Flow During Isometric Exercise at Different Levels of Intraocular Pressure

Purpose

There is evidence that choroidal blood flow (ChBF) is regulated in a complex way during changes in ocular perfusion pressure (OPP). We hypothesized that ChBF regulates better in response to changes in mean arterial pressure (MAP) than in intraocular pressure (IOP).

Methods

Eighteen volunteers (mean age, 26 years) were recruited for a randomized, three-way crossover design. MAP was varied via isometric exercise. IOP was either kept normal or elevated by 10 or 20 mm Hg by using a suction cup. Subfoveal ChBF was measured continuously for 8 minutes with laser Doppler flowmetry and OPP was calculated as 2/3*MAP-IOP. For data analysis, values from all subjects were pooled according to either IOP or MAP values, and correlation analyses were done.

Results

When data were grouped according to IOP, no correlation was observed between ChBF and MAP, but ChBF was lower the higher the IOP (P < 0.001). When data were grouped according to MAP, a significant correlation was found between ChBF and IOP (P < 0.001). When data were pooled according to IOP, the correlation between ChBF and OPP was weaker (P < 0.05). The OPP at which ChBF significantly increased from baseline was 61.3% ± 4.9% without suction cup, 65.2% ± 3.5% when IOP was increased by 10 mm Hg, and slightly lower when IOP was increased by 20 mm Hg (56.3% ± 4.8%, P = 0.07), but this effect did not reach the level of significance.

Conclusions

The present study provides further evidence that the regulation of ChBF during changes in OPP is controlled by complex mechanisms in humans and has less capacity to adapt to IOP elevation than to MAP increase.

Optic Nerve Head Perfusion Before and After Intravitreal Antivascular Growth Factor Injections Using Optical Coherence Tomography-based Microangiography

PURPOSE

To use optical coherence tomography angiography (OCTA) to evaluate the changes in optic nerve head perfusion following intravitreal antivascular endothelial growth factor injections.

METHODS

Preinjection and postinjection intraocular pressure (IOP) and OCTA images were taken of both the injected and uninjected fellow eyes.

RESULTS

Mean preinjection IOP was 16.6±4.7 mm Hg, which increased to a mean of 40.3±13.0 mm Hg (P<0.0001) during the first postinjection image and remained elevated at 36.1±11.5 mm Hg (P<0.0001) during the second postinjection image. Although no significant change was observed in flux, vessel area density, or normalized flux when comparing the OCTA preinjection and first postinjection images, a significant decrease at the second postinjection image was observed (P=0.03, 0.02, and 0.03, respectively). No significant change was observed in the uninjected fellow eye during the same time period (P=0.47, 0.37, and 0.38, respectively).

CONCLUSIONS

Following an antivascular endothelial growth factor injection, mean IOP increased significantly and OCTA imaging of the optic nerve demonstrated a mild but significant decrease in optic nerve head perfusion parameters. Clinicians performing these injections should be aware of these findings and monitor the status of the optic nerve in patients undergoing injections.

Optic nerve head blood flow regulation during changes in arterial blood pressure in patients with primary open-angle glaucoma

PURPOSE

Abnormal autoregulation of optic nerve head blood flow (ONHBF) has been postulated to play an important role in primary open-angle glaucoma (POAG). We used laser Doppler flowmetry (LDF) to estimate quantitatively the ONHBF and compared ONHBF autoregulation between glaucoma patients and healthy controls during isometric exercise.

METHODS

Forty patients with POAG and 40 healthy age- and sex-matched subjects underwent three periods of isometric exercise, each consisting of 2 min of handgripping. Optic nerve head blood flow (ONHBF) was measured continuously using LDF. Systemic blood pressure, intraocular pressure and ocular perfusion pressure were assessed in all participants.

RESULTS

Isometric exercise was associated with an increase in ocular perfusion pressure during all handgripping periods in both groups (p < 0.001). However, there was no change in ONHBF in either group. Three of the glaucoma patients and two of the healthy subjects showed a consistent 10% decrease in blood flow during isometric exercise, in spite of an increase in their blood pressure. This difference between groups was not significant (p = 0.61). Four other glaucoma subjects showed a consistent increase in blood flow of more than 10% during isometric exercise, whereas this was not seen in healthy subjects (p = 0.035).

CONCLUSION

This study suggests that abnormal ONHBF autoregulation is more often seen in patients with POAG than healthy control subjects. The relationship to the glaucoma disease process is currently unknown and requires further investigation.

Alert for Perioperative Visual Loss: An Unusual Presentation of an Orbital Haemangioma during Spinal Surgery

A 62-year-old man with a history of non-insulin-dependent diabetes mellitus, hypertension and obesity, presented for elective lumbar laminectomy for spinal canal stenosis. Twenty minutes after placement in the prone position, he developed left orbital proptosis. The surgery was deferred and a subsequent CT scan showed an orbital haemangioma. This case highlights the importance of meticulous attention to eye-care for patients in the prone position.

Canaloplasty in the Treatment of Open-Angle Glaucoma: A Review of Patient Selection and Outcomes

Canaloplasty is a relatively new non-penetrating surgery for the reduction of intraocular pressure in patients affected by glaucoma. The technique uses a microcatheter to perform a 360 º cannulation of Schlemm’s canal and leaves in place a tension suture providing an inward distension. It aims to restore the physiological outflow pathways of the aqueous humour and is independent of external wound healing. Several studies have shown that canaloplasty is effective in reducing intraocular pressure and has a low rate of complications, especially compared with trabeculectomy, the gold standard for glaucoma surgery. Currently, canaloplasty is indicated in patients with open-angle glaucoma, having a mild to moderate disease, and the combination with cataract phacoemulsification may provide further intraocular pressure reduction. This article reviews canaloplasty indications, results and complications and analyses its outcomes compared with traditional penetrating and non-penetrating techniques.

Evaluation of optic nerve head blood flow in response to increase of intraocular pressure

The time course of the changes in the optic nerve head (ONH) blood flow in response to changes in the ocular perfusion pressure (OPP) induced by an artificial elevation of the intraocular pressure (IOP) has not been determined. We measured the blood flow, represented by the mean blur rate (MBR), on the ONH determined by laser speckle flowgraphy. The MBR was determined before, during, and after the IOP was elevated by 20 or 30 mmHg by pressure applied on the eye by an ophthalmodynamometer in a total of 27 healthy eyes. For an IOP elevation of 20 mmHg, the percentage reduction in the MBR-vessel was −24.7%, and in the MBR-tissue was −16.0% (P < 0.001). For an IOP elevation of 30 mmHg, the percentage reduction of the MBR-vessel was −35.3% and the MBR-tissue was −24.7% (P < 0.001). During the 30 mmHg IOP elevation for 10 minutes, both the MBR-vessel and MBR-tissue began returning to the baseline level from 1 minute after the beginning of the IOP elevation (P < 0.01, P < 0.05, respectively) and continued returning during the 10 minutes IOP elevation (P < 0.001, P < 0.01, respectively). We conclude that the ONH can autoregulate its blood flow in response to experimental changes in OPP induced by IOP elevations.

Visual Loss Following Spine Surgery: What Have We Seen Within the Scoliosis Research Society Morbidity and Mortality Database?

STUDY DESIGN

A retrospective review of the Scoliosis Research Society (SRS) morbidity and mortality (M&M) database.

OBJECTIVE

The aim of this study was to investigate visual related complications in spinal deformity patients undergoing spine surgery.

SUMMARY OF BACKGROUND DATA

The SRS compiles surgeon-reported complications into an M&M database, tracking postoperative complications including visual loss, neurological deficits, infections, and death. Limited literature exists on postoperative visual complications, a rare but devastating complication following spine surgery.

METHODS

We utilized the SRS M&M database to determine demographics, perioperative risk factors, and prognosis for visual related complications in spinal deformity patients undergoing corrective spine surgery from 2009 to 2012.

RESULTS

A total of 167,972 spinal deformity patients from 2009 to 2012 were identified with a visual acuity complication (VAC) rate of 0.01%, or 12.5 per 100,000 patients. VAC rates for patients with kyphosis were significantly higher than patients with scoliosis (0.049% vs. 0.010%, P = 0.002) and spondylolisthesis (0.049% vs. 0.005%, P = 0.001). Postoperative visual loss rates significantly decreased from 2010 to 2012 (0.022% vs. 0.004%, P = 0.029). Twenty-one patients identified with VACs had a mean age of 34.8 ± 24.3 years. Two (9.5%) patients had preoperative vision changes, two (9.5%) were diabetic, two (9.5%) had vascular disease, one (4.8%) had a history of thromboembolic disease, and five (23.8%) had hypertension. Extent of VAC was bilateral-partial in four (19.0%), bilateral-total in five (23.8%), unilateral-partial in eight (38.1%), and unilateral-total in three (14.3%) patients. Four (19.0%) patients developed anterior ischemic optic neuropathy, four (19.0%) had posterior ischemic optic neuropathy (PION), five (23.8%) had central retinal artery occlusion, and five (23.8%) developed cortical blindness (CB). Greater than 50% of the VACs occurred on, or before, the first postoperative day. Ten (47.6%) patients recovered complete vision and four (19.0%) improved. All patients with CB and 50% with posterior ischemic optic neuropathy experienced complete resolution.

CONCLUSION

VACs occur in approximately 12.5 per 100,000 deformity patients, with a rate five times higher in patients with kyphosis. More than 50% of these complications occur within 24 hours postoperatively. Nearly half of these complications resolve completely, and another 19% improve postoperatively.

LEVEL OF EVIDENCE

4.

Update on Perioperative Ischemic Optic Neuropathy Associated With Non-ophthalmic Surgery

Perioperative visual loss (POVL) is a rare, serious complication of non-ophthalmic surgeries. Ischemic optic neuropathy (ION), and retinal arterial occlusion (RAO) are the main causes (1, 2). Less frequent are cortical blindness (3), acute glaucoma (4), and choroidal and vitreous hemorrhage (5). ION is the most common cause for which the neurologist or neuro-ophthalmologist is consulted as it is associated either with a normal ophthalmic exam (posterior ION, PION), or less often, with optic nerve (ON) head swelling (anterior ION, AION). The presumed cause is impaired blood supply to the optic nerve (Figure 1). The most common surgical procedures complicated by ION are cardiac surgery and spinal fusion. Retrospective studies, surveys, and case reports are the basis of most knowledge regarding peri-operative ION (poION), with cohort and case-control studies helping to identify candidate risk factors (6, 7). Animal models have provided insight regarding mechanisms (8). This mini-review is an update on the latest advancements regarding poION in non-ophthalmic surgeries in epidemiological, clinical, and animal studies.

Extraocular Pressure Measurements to Avoid Orbital Compartment Syndrome in Aneurysm Surgery

BACKGROUND

Orbital compartment syndrome (OCS) is a rare but devastating complication following pterional craniotomy. Although the causes of OCS are unclear, external compression of the orbit by a myocutaneous flap is commonly mentioned as a major factor. We evaluated the ocular influence of external compression using an extraocular pressure monitor.

METHODS

We measured extraocular pressure in 86 patients who underwent surgery for cerebral aneurysm via a pterional approach. Clinical information and radiologic parameters, including the area of the medial rectus muscle (MRM) and the craniotomy height from the bottom of the anterior skull base, were collected. As a control group, 117 patients who underwent surgery without pressure monitoring were also evaluated.

RESULTS

Extraocular pressure reached a maximum during craniotomy (mean, 22.0 mm Hg; range, 18.4-51.0 mm Hg) and decreased after myocutaneous flap adjustment (mean, 7.9 mm Hg; range, 5.4-17.5 mm Hg). Pressure before myocutaneous flap manipulation differed between patients with anterior communicating artery (Acomm) aneurysms and other patients (mean, 16.5 mm Hg vs. 9.4 mm Hg; P = 0.003). Among Acomm aneurysm cases, the monitored group showed a significantly lower MRM swelling ratio (postoperative MRM area/preoperative MRM area) compared with the control group (1.03 ± 0.10 vs. 1.17 ± 0.15; P = 0.036).

CONCLUSIONS

Myocutaneous flaps can produce unnoticed overpressure on the orbit, resulting in OCS-related blindness during aneurysm clipping surgery, especially in cases involving mandatory lower craniotomy. The continuous extraocular compressive pressure monitoring technique is a simple and effective approach to prevent such a serious complication.

Ocular Blood Flow Endpoints

Impaired blood supply or reduced ocular blood flow may cause optic nerve damage in glaucoma patients. It is therefore beneficial to study the ocular hemodynamics of glaucoma patients. This article discusses various techniques used in examining orbital and intraocular vessels and ocular blood flow. Color Doppler Imaging (CDI), Laser Doppler Flowmetry (LDF), the Heidelberg Retina Flowmeter (HRF), angiography, ocular pulse amplitudes, and pulsatile ocular blood flow are reviewed. Although there are many techniques available for measuring ocular hemodynamics, the most promising approach may be the direct measurement of capillary blood flow by laser Doppler techniques.

Optical Coherence Tomography Angiography Vessel Density Changes after Acute Intraocular Pressure Elevation

To investigate changes in retinal vessel density in optic nerve head (ONH) and macula after acute intraocular pressure (IOP) elevation, we conducted a prospective observational study. Eyes with IOP rise ≥5 mmHg after 2-hour dark room prone provocative test (DRPPT) were included. Vasculature of ONH and macula was examined by optical coherence tomography angiography (OCTA) at baseline and after DRPPT. Among the 65 eyes of 42 individuals, 40 eyes with qualified images were enrolled. Mean IOP rise was 9.6 ± 4.2 mmHg (5.0-23.3 mmHg) after DRPPT. Retinal vessel density did not differ after IOP rise for either the papillary region (optic nerve head and radial peripapillary capillary layer) or the macula region (superficial, deep and outer retinal layer) (P > 0.05). Vessel density in each subregion did not change either. If only enrolled eyes with IOP rise ≥10 mmHg, similar results were obtained in condition of IOP increase by 15.0 ± 3.6 mmHg. To conclude, eyes with an acute IOP elevation by 10 or 15 mmHg for two hours, while the blood pressure remained constant, the vessel density in both ONH and macula region examined by OCTA did not show significant changes. The observations fit with an IOP-related autoregulation in retinal blood flow for a moderate elevation of IOP.

Regulation of Optic Nerve Head Blood flow in Normal Tension Glaucoma Patients

Purpose

To investigate the regulation of the optic nerve blood flow (Fonh) in response to an increase of the perfusion pressure (PPm) in normal tension glaucoma (NTG) patients and in age-matched normal volunteers.

METHODS

Measurements were performed in 16 eyes of NTG patients and in 10 eyes of age-matched controls. Laser Doppler flowmetry (LDF) was applied to calculate the relative flux of red blood cells at the temporal rim of the optic nerve head (ONH) in response to increases in PPm. PPm was raised through an increase in systemic blood pressure induced by isometric exercise. Before being tested, all patients had 3 weeks of washout of any local medication.

Results

In the NTG group, mean ophthalmic arterial blood pressure increased during isometric exercise from 73 to 89 mmHg (22%), resulting in a 29% increase of the PPm. This increase did not induce any significant change in mean Fonh. For the control group, the 28% increase of PPm also did not significantly affect Fonh. There was a trend for a greater increase in vascular resistance during isometric exercise in the NTG than in the normal control group (47% versus 25%).

CONCLUSIONS

The LDF parameters, measured in the ONH, did not indicate an abnormal Fonh regulation in response to an increase of the PPm in either normal subjects or NTG patients. The maintenance of constant blood flow is achieved by an increase in local vascular resistance. Our data show a greater percent increase in vascular resistance in the NTG patients compared to the normal subjects for a similar percent increase in PPm in both groups during squatting. This suggests some alteration of the vessel tone regulatory mechanisms in NTG patients.

Robot-assisted radical cystectomy: patient selection and special considerations

Robot-assisted (RA) procedures are increasingly being performed as minimally invasive surgical approaches. Less insensible losses due to a closed abdomen, smaller incisions with less retractor strain, decreased analgesic requirements, and earlier postoperative ambulation are suggested advantages of robot-assisted radical cystectomy (RARC). Patients who undergo open radical cystectomy are also candidates for RARC procedure. However, the steep Trendelenburg position and pneumoperitoneum develop a non-physiological condition. Intra-abdominal adhesions preventing the placement of the ports and patients who cannot tolerate the pneumoperitoneum and/or steep Trendelenburg position are special contraindications of RARC. Besides, body mass index >30 kg/m2, presence of extravesical disease, bulky lymphadenopathy, previous vascular surgery, previous distal colorectal surgery, previous pelvic radiation, previous pelvic trauma, and/or preexisting cardiovascular/pulmonary disease that is compromised with positioning are not certainly contraindicated but unwanted conditions in which the RARC may be performed successfully as the surgeons gain experience.

Optic nerve head and retinal blood flow regulation during isometric exercise as assessed with laser speckle flowgraphy

The aim of the present study was to investigate regulation of blood flow (BF) in the optic nerve head (ONH) and a peripapillary region (PPR) during an isometric exercise-induced increase in ocular perfusion pressure (OPP) using laser speckle flowgraphy (LSFG) in healthy subjects. For this purpose, a total of 27 subjects was included in this study. Mean blur rate in tissue (MT) was measured in the ONH and in a PPR as well as relative flow volume (RFV) in retinal arteries (ART) and veins (VEIN) using LSFG. All participants performed isometric exercise for 6 minutes during which MT and mean arterial pressure were measured every minute. From these data OPP and pressure/flow curves were calculated. Isometric exercise increased OPP, MT_ONH and MT_PRR. The relative increase in OPP (78.5 ± 19.8%) was more pronounced than the increase in BF parameters (MT_ONH: 18.1 ± 7.7%, MT_PRR: 21.1 ± 8.3%, RFV_ART: 16.5 ±12.0%, RFV_VEIN: 17.7 ± 12.4%) indicating for an autoregulatory response of the vasculature. The pressure/flow curves show that MT_ONH, MT_PRR, RFV_ART, RFV_VEIN started to increase at OPP levels of 51.2 ± 2.0%, 58.1 ± 2.4%, 45.6 ± 1.9% and 45.6 ± 1.9% above baseline. These data indicate that ONHBF starts to increase at levels of approx. 50% increase in OPP: This is slightly lower than the values we previously reported from LDF data. Signals from the PPR may have input from both, the retina and the choroid, but the relative contribution is unknown. In addition, retinal BF appears to increase at slightly lower OPP values of approximately 45%. LSFG may be used to study ONH autoregulation in diseases such as glaucoma.

Trial Registration: ClinicalTrials.gov NCT02102880

Vulnerability study of myelinated and unmyelinated nerve fibers in acute ocular hypertension in rabbit

In the current study, it was aimed to evaluate the changes in myelinated and unmyelinated nerve fibers in retinal ischemia-reperfusion injuries caused by acute ocular hypertension and to determine the sequence of these changes. Adult healthy New Zealand white rabbits were randomized to the hemodynamic group [n=12; used to determine the optimal intraocular pressure (IOP) for the subsequent experiments] and the hypertension group (n=6; 70-mmHg hypertension induced in one eye). IOP was adjusted using a cannula and saline. Doppler ultrasound was used to measure the velocity of the optic artery under different intraocular pressures. Immunohistochemistry for myelin basic protein (MBP) was performed. Apoptosis of retinal cells was detected by terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) assay. Electron microscopy was used to investigate the changes in myelinated and unmyelinated nerve fibers. IOP of the hypertension eyes was maintained at 70.2±1.0 mmHg, while IOP of control eyes was 7–14 mmHg. Doppler ultrasound demonstrated an obvious decline of peak systolic velocity and an increase of resistance index of retinal bloodstream under a 70-mmHg IOP. MBP immunohistochemistry and electron microscopy demonstrated obvious injuries to the myelin fibers. TUNEL indicated a significantly higher apoptosis rate in the hypertension eyes compared with control eyes. The apoptosis rate of retinal ganglion cells and bipolar cells in unmyelinated regions was higher than in myelinated regions. In conclusion, an IOP of 70 mmHg led to incomplete retinal ischemia but was the threshold for retinal ischemia, leading to obvious injuries to the myelin fibers.

Impaired Autoregulation of Blood Flow at the Optic Nerve Head During Vitrectomy in Patients With Type 2 Diabetes

PURPOSE

To determine whether type 2 diabetes mellitus (T2DM) influences autoregulation of optic nerve head (ONH) blood flow during vitrectomy.

DESIGN

Cohort study.

METHODS

Thirteen eyes of 13 subjects with T2DM and 30 eyes of 30 controls without T2DM undergoing vitrectomy for epiretinal membrane or macular hole were included. Following 25 gauge vitrectomy, we measured the mean blur rate (MBR), an index of ONH blood flow, in the vascular area (vascular MBR) and in the tissue area (tissue MBR) using laser speckle flowgraphy. We performed measurements before and 5 and 10 minutes after intraocular pressure (IOP) elevation of approximately 15 mm Hg; both parameters represent relative values (%, compared with baseline). We calculated the vascular MBR recovery rate as (vascular MBR at 10 min-vascular MBR at 5 min)/(vascular MBR at baseline-vascular MBR at 5 min).

RESULTS

Vascular MBR in T2DM subjects was significantly lower than that in controls at 5 and 10 minutes after IOP elevation (P = .0328 and P < .0001, respectively). Tissue MBR was also significantly lower in T2DM subjects than in controls at both time points (P = .0253 and P = .0004, respectively). Vascular MBR recovery rate was significantly lower in the T2DM than in the control group (P = .0090). Furthermore, the vascular MBR recovery rate was significantly negatively correlated with hemoglobin A1c and fasting plasma glucose levels (P = .0284 and P = .0381, respectively).

CONCLUSIONS

T2DM is associated with impaired ONH blood flow autoregulation in both vascular and tissue areas when subjected to change in IOP during vitrectomy.

Effect of selective laser trabeculoplasty on ocular haemodynamics in primary open-angle glaucoma

PURPOSE

Selective laser trabeculoplasty (SLT) is known to reduce intraocular pressure (IOP) effectively. The aim of this study, however, was to evaluate the effect of SLT on ocular haemodynamics.

METHODS

A total of 69 eyes of 69 patients (age 67.8 ± 9.9 years) with already treated primary open-angle glaucoma who were assigned for SLT for further IOP reduction were consecutively enrolled in this prospective interventional case series. Intraocular pressure, the ocular pulse amplitude (OPA), ocular pulse volume (OPV) and pulsatile ocular blood flow (pOBF) were assessed with the Ocular Blood Flow Analyzer prior to and 3 months after SLT.

RESULTS

Intraocular pressure was statistically significantly reduced from 16.0 ± 5.4 mmHg to 12.8 ± 4.0 mmHg (p = 0.001). The OPA did not change (p = 0.783) after IOP reduction following SLT. OPV and pOBF increased statistically significantly. OPV increased from 7.33 ± 3.05 to 8.59 ± 3.35 μl (17.2%; p = 0.001) and pOBF from 17.11 ± 5.42 to 19.74 ± 6.59 μl/s (15.4%; p = 0.002).

CONCLUSION

Selective laser trabeculoplasty probably does not induce any pharmacological changes effecting systemic blood pressure or ocular blood flow as topical IOP-lowering medication might do, nor does it change biomechanical properties of the eye as surgery could. Therefore, an increase in ocular blood flow following SLT can only be explained by the reduction in IOP and might be a sign of dysfunctional autoregulation in glaucoma patients.

Does steep Trendelenburg positioning effect the ocular hemodynamics and intraocular pressure in patients undergoing robotic cystectomy and robotic prostatectomy?

PURPOSE

To examine the effect of steep Trendelenburg position (ST) on intraocular pressure (IOP), resistive index of the central retinal artery, and venous impedance index of the central retinal vein during robotic prostatectomy and cystectomy.

METHODS

A total of fifty-three male patients were included into the study (prostatectomy: 43, cystectomy: 10). During robotic surgery, the effect of the ST on IOP, resistive index of the central retinal artery (CRA-RI), and venous impedance index of the central retinal vein (CRV-VI) was prospectively examined. The measurement times of IOP are as follows: T1: before anesthesia while supine and awake; T2: anesthetized and supine; T3: anesthetized and ST; T4: anesthetized, ST, and intraperitoneal insufflation; T5: anesthetized in ST at the end of the procedure with CO₂; T6: anesthetized in ST after desufflation; and T7: anesthetized supine before awakening.

RESULTS

There was no difference between the IOP values of the right and left eyes in both groups. The highest IOP values were reached at T4 and T5. CRA-RI values were different, while CRV-VI values were similar at T1 and T4.

CONCLUSIONS

Despite staying in the ST for a long time provided that the ophthalmologic examination was normal, ocular complication risk is low in robotic prostatectomy and cystectomy.

Autoregulation of Optic Nerve Head Blood Flow Induced by Elevated Intraocular Pressure during Vitreous Surgery

PURPOSE

To investigate optic nerve head (ONH) blood flow changes resulting from intraocular pressure (IOP) elevation in subjects without systemic disorders.

MATERIALS AND METHODS

Eighteen eyes of 18 patients who underwent vitrectomy to treat an epiretinal membrane or macular hole at Toho University Sakura Medical Center were included. Following standard 25-gauge microincision vitreous surgery, mean blur rate (MBR) in tissue (MT), an index of ONH blood flow, was measured using laser speckle flowgraphy. Measurements were taken before and 5 and 10 minutes after a 15 mmHg IOP elevation.

RESULTS

The ONH blood flow was initially lower than baseline (P = 0.001) after elevating IOP from 14.8 ± 2.8 mmHg to approximately 30 mmHg. Between 5 and 10 minutes after elevating IOP, ONH blood flow partially recovered (P = 0.004), even though ocular perfusion pressure was 20.2% lower than at baseline.

CONCLUSIONS

The ONH blood flow in subjects without systemic disorders was initially lower, but began to recover 5-10 minutes after a 15 mmHg elevation in IOP. These results indicate that autoregulatory mechanisms of ONH blood flow may help to minimize the effects of IOP elevations and fluctuations during vitreous surgery.

Perioperative Vision Loss in Spine Surgery and Other Orthopaedic Procedures

Perioperative vision loss is a rare complication of orthopaedic surgery and has been documented after spine, knee, hip, and shoulder procedures. It is associated with several ophthalmologic diagnoses, most commonly ischemic optic neuropathy. Although the pathophysiology remains unclear, current evidence suggests that systemic hemodynamic compromise and altered balance of intraocular perfusion contribute to the development of ischemic optic neuropathy. Although vision recovery has been reported, the prognosis of perioperative vision loss is poor, and no proven effective treatment is available. Perioperative vision loss is unpredictable and can occur in healthy patients. Associated risk factors include pediatric or elderly age, male sex, obesity, anemia, hypotension or hypertension, perioperative blood loss, prolonged surgical time, and prone positioning. Preventive strategies include avoiding direct pressure to the eye, elevating the head, optimizing perioperative hemodynamic status, and minimizing surgical time with staged surgical procedures as appropriate.

Short-term changes of intraocular pressure and ocular perfusion pressure after intravitreal injection of bevacizumab or ranibizumab

Background

The aim of this study was to investigate the effect of intravitreal anti-vascular endothothelial growth factor (VEGF) injection on intraocular pressure (IOP) and mean ocular perfusion pressure (MOPP).

Methods

MOPP results were obtained by measuring mean arterial pressure (MAP) and IOP just before the injection, immediately after the injection, at 30 min, 1 day, and 1 week after injection from 65 eyes of 42 patients.

Results

Pre-injection mean IOP was 16.66 ± 3.50 mmHg, and mean IOP was 43.81 ± 9.69 mmHg immediately after the injection, 17.57 ± 4.44 mmHg at 30 min, 15.00 ± 4.21 mmHg at 1 day, and 15.90 ± 3.63 mmHg at 1 week after the injection. Pre-injection mean MOPP was 46.39 ± 5.78 mmHg, and mean MOPP was 25.14 ± 8.79 mmHg immediately after the injection, 45.87 ± 6.31 mmHg at 30 min, 46.93 ± 6.25 mmHg at 1 day, and 46.50 ± 4.94 mmHg at 1 week after the injection.

Conclusion

The instant increase in IOP by intravitreal anti-VEGF injection led to a transient decrease in MOPP. Based on this finding, the instant increase in IOP after intravitreal anti-VEGF injection does not significantly impair retinal blood flow.

Orbital apex disorders: a case series

Orbital apex syndrome is an uncommon disorder characterized by ophthalmoplegia, proptosis, ptosis, hypoesthesia of the forehead, and vision loss. It may be classified as part of a group of orbital apex disorders that includes superior orbital fissure syndrome and cavernous sinus syndrome. Superior orbital fissure syndrome presents similarly to orbital apex syndrome without optic nerve impairment. Cavernous sinus syndrome includes hypoesthesia of the cheek and lower eyelid in addition to the signs seen in orbital apex syndrome. While historically described separately, these three disorders share similar causes, diagnostic course, and management strategies. The purpose of this study was to report three cases of orbital apex disorders treated recently and to review the literature related to these conditions. Inflammatory and vascular disorders, neoplasm, infection, and trauma are potential causes of orbital apex disorders. Management is directed at the causative process. The cases described represent a rare but important group of conditions seen by the maxillofacial surgeon. A review of the clinical presentation, etiology, and management of these conditions may prompt timely recognition and treatment.

Nocturnal blood pressure in primary open-angle glaucoma

PURPOSE

To evaluate the nocturnal blood pressure (BP) dipping-pattern in patients with manifest primary open-angle glaucoma (POAG) and to find possible associations with the severity of visual field damage.

METHODS

A number of 314 patients suffering from POAG were consecutively enrolled in this cross-sectional hospital-based study. Each patient had diurnal intraocular pressure (IOP) measurements, 24-hr BP monitoring and computerized perimetry with the Humphrey 30-2 sita Standard program. Inclusion criteria were a mean IOP of less than 15 mmHg with fluctuations of less than 5 mmHg and a visual acuity of at least 20/40. One eye was randomly selected. Based on the night-day BP ratio, a mean arterial nocturnal BP drop of less than 10% was considered as non-dipping, between 10% and 20% as physiological dipping and of more than 20% as over-dipping.

RESULTS

Glaucoma patients with daytime systemic normotension on the average had more visual field loss in the over-dipper group (MD = - 16.6 dB, IQR = -18.9 to -2.7 dB) than glaucoma patients with daytime systemic hypertension, who had less visual field defects in the over-dipper group (MD = -3.9 dB, IQR = -6.2 to -1.9 dB) (p = 0.004). This result was also found taking age, glaucoma duration, visual acuity, gender, systemic and topical medication as covariates into account.

CONCLUSIONS

To judge the nocturnal BP situation of an individual patient, it is important to do this in relation to the daytime BP level. Twenty-four-hour BP evaluation might be important for all patients with POAG, as nocturnal BP could be a modifiable risk factor for glaucoma severity and progression.

Scheimpflug camera in the quantitative assessment of reproducibility of high-speed corneal deformation during intraocular pressure measurement

The paper presents an original analysis method of corneal deformation images from the ultra-high-speed Scheimpflug camera (Corvis ST tonometer). Particular attention was paid to deformation frequencies exceeding 100 Hz and their reproducibility in healthy subjects examined repeatedly. A total of 4200 images with a resolution of 200 × 576 pixels were recorded. The data derived from 3 consecutive measurements from 10 volunteers with normal corneas. A new image analysis algorithm, written in Matlab with the use of the Image Processing package, adaptive image filtering, morphological analysis methods and fast Fourier transform, was proposed. The following results were obtained: (1) reproducibility of the eyeball reaction in healthy subjects with precision of 10%, (2) corneal vibrations with a frequency of 369 ± 65 Hz (3) and amplitude of 7.86 ± 1.28 µm, (4) the phase shift within two parts of the cornea of the same subject of about 150°. The result of image sequence analysis for one subject and deformations with a corneal frequency response above 100 Hz.