Facts and myths of cerebrospinal fluid pressure for the physiology of the eye

Distinctive Imaging Characteristics of Retinal and Cerebral Vessels between Central and Branch Retinal Vein Occlusion by MRI and AI-Based Image Analyzer

Retinal vessels have been good predictive and prognostic imaging biomarkers for systemic or eye diseases. Numerous studies have shown that the two retinal vein occlusion entities may correlate with cardiovascular and cerebrovascular events or primary open-angle glaucoma. This study aims to investigate if there is a disparity in the correlations between branch RVO (BRVO) and central RVO (CRVO) with systemic disorders or POAG, thus explaining the pathogenic difference between BRVO and CRVO. This retrospective case-control study enrolled 59 RVO subjects (118 eyes), including 25 CRVO and 34 BRVO subjects, who received routine eye and brain MRI examinations. The geometric characteristics of the caliber of the retinal and cerebral blood vessels and the optic nerve subarachnoid space width (ONSASW) were measured. Multivariable logistic regression analysis showed that ONSASW at 3 mm behind the globe (p = 0.044) and the relative retinal venular calibers (p = 0.031) were independent risk factors for the CRVO-affected eyes group in comparison with the BRVO-affected eyes group after adjusting for age, duration of hypertension, BMI, and IOP. In the CRVO-affected eyes, narrower relative retinal arteriolar calibers (p = 0.041) and wider relative venular calibers (p = 0.011) were independent risk factors compared with the CRVO-contralateral normal eyes when adjusting for IOP. We concluded that BRVO may be more associated with cerebrovascular diseases, and CRVO may be correlated with primary angle glaucoma. The geometric characteristics difference between the retinal and cerebrovascular may explain the pathological difference between CRVO and BRVO.

Evaluation of lamina cribrosa and peripapillary vascular density in thyroid orbitopathy and effect of intravenous methylprednisolone therapy

OBJECTIVE

To evaluate optic nerve head changes in patients with thyroid orbitopathy (TO) and investigate the effects of intravenous methylprednisolone (IV MTP) on these changes.

METHODS

Eighty-two eyes of 41 patients with TO with and without dysthyroid optic neuropathy (DON) and 40 eyes of 40 healthy control subjects were included in the study. Lamina cribrosa thickness (LCT) and depth (LCD) measurements, peripapillary retinal nerve fibre layer thickness (RNFLT), and radial peripapillary capillary vascular density were measured using optical coherence tomography and optical coherence tomography angiography. Visual field examination and proptosis were evaluated. Patients with DON and active non-DON received IV MTP for 12 weeks, and the effect of this treatment was evaluated.

RESULTS

Peripapillary vascular density decreased in patients with DON compared with the other groups (p < 0.001 for all); there was no difference in the total, superior hemi-sector, and inferior hemi-sector of the RNFLT between the groups. LCT was decreased in the TO group (p < 0.001). After IV MTP treatment, the LCT and best-corrected visual acuity were increased. Thyroid-stimulating hormone receptor antibody levels, intraocular pressure, the superior hemi-sector of the RNFLT, and proptosis were decreased compared with the control subjects (p = 0.012, p = 0.008, p = 0.043, and p < 0.001, respectively).

CONCLUSIONS

The RNFLT may not always increase in DON. Lamina cribrosa morphology may change in patients with TO. IV MTP therapy has a positive effect on the LCT but not on radial peripapillary capillary vascular density or LCD.

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.

Evaluation of effect of covıd-19 pandemic on anatomical and functional changes and vision-related quality of life in patients with glaucoma

BACKGROUND

To evaluate anatomical and functional changes and vision-related quality of life in patients whose glaucoma follow-up was disrupted by the COVID-19 restrictions.

METHODS

This retrospective observational study included 100 patients who were followed up at the glaucoma unit. For the patients whose follow-up evaluations were postponed due to COVID-19 restrictions, visual acuity (VA), intraocular pressure (IOP), retinal nerve fiber layer (RNFL) thickness, visual field parameters [mean deviation (MD), pattern standard deviation (PSD), and visual field index (VFI)], and the National Institute of Ophthalmology Visual Function Scale-25 (NEI-VFQ-25) score were evaluated based on the measurements performed at the last visit before COVID-19 (V1) and at the first visit after the removal of COVID-19 restrictions (V2).

RESULTS

The mean age of the patients was 61.1 ± 13.4 years, the mean follow-up time was 11.4 ± 4.2 months, and the mean interval between the last two visits was 7.2 ± 2.7 months. In the evaluation of the last two visits, VA was lower and IOP was higher at V2, and there was progression in the MD, PSD, and VFI values (p<0.05, for all). RNFL thickness progression was seen in 13-23% of the patients. According to the NEI-VFQ-25 evaluation, except for peripheral vision and near vision, all the remaining subscale scores and the total score were lower at V2 (p<0.05, for all).

CONCLUSIONS

This study demonstrates the devastating impact of the COVID-19 pandemic on the anatomical and functional changes and vision-related quality of life together in patients with glaucoma.

Enhancement of optic nerve sheath on MRI in idiopathic intracranial hypertension(IIH)

OBJECTIVE

Optic nerve sheath(ONS) enhancement in idiopathic intracranial hypertension (IIH) patients has been reported in recent years. In this retrospective observation, we analyzed the clinical characteristics of IIH patients with enhancement of ONS.

METHODS

Eighty-two patients with clinically diagnosed IIH from January 2017 to December 2019 were under observation. Then, based on the presence of contrast-enhancement (CE) in ONS on orbital magnetic resonance image (MRI), the IIH patients were divided into CE-ONS group and no-CE(NCE)-ONS group. Six months follow-up information was also included in the observation study. By comparing clinical data of the two groups of IIH patients, we tried to evaluate whether there is clinical heterogeneity in CE-ONS patients.

RESULT

12 patients were included in CE-ONS group, 10 females and 2 males. 70 patients were included in NCE-ONS group, 56 women and 14 men. We found that patients with CE-ONS had a longer course of disease (median disease duration before diagnosis, 5 months vs. 3months, P<0.01) and more likely had the sign of distension of the perioptic subarachnoid space (DPSS) (58.33 % vs. 24.29 %, P = 0.034). But no significant differences were found in demographic characteristics, clinical symptoms, degree of visual impairment, papilledema, opening pressure(OP) on lumbar puncture and clinical outcomes.

CONCLUSION

As a rare sign on MRI, ONS enhancement can occur in patients with IIH. IIH patients with CE-ONS may have a longer course of disease and more prone to DPSS, but there is no significant difference in clinical manifestations, OP, and clinical outcomes compared with IIH patients without CE-ONS.

Role of Optic Nerve Head Characteristics in Predicting Intraocular Pressure Spikes after Cataract Surgery in Highly Myopic Eyes

INTRODUCTION

To evaluate the characteristics of optic nerve head (ONH) in highly myopic eyes and its role in predicting intraocular pressure (IOP) spikes after cataract surgery.

METHODS

Patients who are highly myopic and were scheduled for cataract surgery were enrolled in this prospective case series study. IOP was measured preoperatively and at 1 day and 3 days postoperatively. ONH characteristics including area, tilt ratio, lamina cribrosa (LC) thickness, and depth, and the presence of LC defects were evaluated with enhanced depth imaging optical coherence tomography. Factors influencing LC defects and early IOP spike were investigated using multivariate stepwise logistic regression.

RESULTS

In total, 200 highly myopic eyes of 200 patients were analyzed: 35.00% had small ONH, 53.00% had ONH tilt, and 14.00% had LC defects. Multivariate analysis demonstrated female patients with larger ONH area and deeper LC tended to have LC defects (all P < 0.05). As to postoperative IOP, IOP change, and incidence of IOP spikes, eyes with small ONH, ONH tilt, and LC defects had similar (all P > 0.05), higher (all P < 0.05), and lower (all P < 0.05) outcomes compared with those without the corresponding characteristic, respectively. Multivariate analysis showed that presence of LC defects and thicker LC were protective factors for early IOP spikes, and axial length > 28 mm was a risk factor (all P < 0.05).

CONCLUSION

Female patients with larger ONH area and deeper LC tend to have LC defects, which, together with thicker LC, was correlated with less IOP spikes in highly myopic eyes.

TRIAL REGISTRATION

This study was conducted as part of a larger project, the Shanghai High Myopia Study, registered at www.

CLINICALTRIALS

gov (accession number NCT03062085).

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Retinal microvasculature is a potential biomarker for acute mountain sickness

Increased cerebral blood flow resulting from altered capillary level autoregulation at high altitudes leads to capillary overperfusion and then vasogenic cerebral edema, which is the leading hypothesis of acute mountain sickness (AMS). However, studies on cerebral blood flow in AMS have been mostly restricted to gross cerebrovascular endpoints as opposed to the microvasculature. This study aimed to investigate ocular microcirculation alterations, the only visualized capillaries in the central neural system (CNS), during early-stage AMS using a hypobaric chamber. This study found that after high altitude simulation, the optic nerve showed retinal nerve fiber layer thickening (P=0.004-0.018) in some locations, and the area of the optic nerve subarachnoid space (P=0.004) enlarged. Optical coherence tomography angiography (OCTA) showed increased retinal radial peripapillary capillary (RPC) flow density (P=0.003-0.046), particularly on the nasal side of the nerve. The AMS-positive group had the largest increases in RPC flow density in the nasal sector (AMS-positive, Δ3.21±2.37; AMS-negative, Δ0.01±2.16, P=0.004). Among multiple ocular changes, OCTA increase in RPC flow density was associated with simulated early-stage AMS symptoms (beta=0.222, 95%CI, 0.009-0.435, P=0.042). The area under the receiver operating characteristics curve (AUC) for the changes in RPC flow density to predict early-stage AMS outcomes was 0.882 (95%CI, 0.746-0.998). The results further confirmed that overperfusion of microvascular beds is the key pathophysiologic change in early-stage AMS. RPC OCTA endpoints may serve as a rapid, noninvasive potential biomarker for CNS microvascular changes and AMS development during risk assessment of individuals at high altitudes.

Choroidal vascularity profile in diabetic eyes using wide field optical coherence tomography

PURPOSE

To report the wide-field choroidal vascularity up to the mid-equator area in diabetic retinopathy (DR) subjects using wide-field optical coherence tomography (WF-OCT).

DESIGN

Prospective, Cross-sectional study.

PARTICIPANTS

Forty-seven eyes of 25 DR subjects.

METHODS

WF-OCT images (55 degrees) were obtained using Spectralis HRA + OCT (Heidelberg Engineering, Germany) in extremes of gazes in all quadrants and manual montages were created to obtain wide field images up to mid equator. A previously reported semi-automated algorithm was used to calculate choroidal vascularity profile (CVI). Regression analysis was performed to identify the factors influencing CVI.

RESULTS

Forty-seven eyes from 25 patients were enrolled in the study. The mean age was 68.4 ± 10.6 years. The refractive error (spherical equivalent) ranged from -2.25 to +3.75 diopters. Most common DR grade among study subjects was moderate NPDR (29.41%) and 74.5% eyes had diabetic macular edema (DME). The mean CVI in the macular area (58.29 ± 3.63) was significantly lower than in any of the other fundus areas (all p ˂ 0.01). The maximum CVI was seen in the nasal region (66.60 ± 5.61), followed by temporal (65.69 ± 3.81), superior (65.01 ± 4.87), and inferior (63.80 ± 5.42). The vertical macular area had the least coefficient of variation (CV) of CVI (0.06) while the inferior quadrant had the highest CV (0.08).

CONCLUSION

The current study describes the CVI profile on WF-OCT in DR eyes up to mid-equator. The significant increase of the CVI compared to healthy subjects and its significant regional variations introduce this novel quantitative parameter as a reliable biomarker of the diabetes-induced choroidal microangiopathy.

Relative Contributions of Intraocular and Cerebrospinal Fluid Pressures to the Biomechanics of the Lamina Cribrosa and Laminar Neural Tissues

Purpose

The laminar region of the optic nerve head (ONH), thought to be the site of damage to the retinal ganglion cell axons in glaucoma, is continuously loaded on its anterior and posterior surfaces by dynamic intraocular pressure (IOP) and orbital cerebrospinal fluid pressure (CSFP), respectively. Thus, translaminar pressure (TLP; TLP = IOP-CSFP) has been proposed as a glaucoma risk factor.

Methods

Three eye-specific finite element models of the posterior human eye were constructed, including full 3D microstructures of the load-bearing lamina cribrosa (LC) with interspersed laminar neural tissues (NTs), and heterogeneous, anisotropic, hyperelastic material formulations for the surrounding peripapillary sclera and adjacent pia. ONH biomechanical responses were simulated using three combinations of IOP and CSFP loadings consistent with posture change from sitting to supine.

Results

Results show that tensile, compressive, and shear stresses and strains in the ONH were higher in the supine position compared to the sitting position (P < 0.05). In addition, LC beams bear three to five times more TLP-driven stress than interspersed laminar NT, whereas laminar NT exhibit three to five times greater strain than supporting LC (P < 0.05). Compared with CSFP, IOP drove approximately four times greater stress and strain in the LC, NT, and peripapillary sclera, normalized per mm Hg pressure change. In addition, IOP drove approximately three-fold greater scleral canal expansion and anterior-posterior laminar deformation than CSFP per mm Hg (P < 0.05).

Conclusions

Whereas TLP has been hypothesized to play a prominent role in ONH biomechanics, the IOP and CSFP effects are not equivalent, as IOP-driven stress, strain, and deformation play a more dominant role than CSFP effects.

Association of serum retinol concentration with normal-tension glaucoma

OBJECTIVES

To evaluate the association between serum retinol concentration and normal-tension glaucoma (NTG).

METHODS

A total of 345 study subjects were recruited in a prospective cross-sectional study: 101 patients with NTG, 106 patients with high-pressure primary open-angle glaucoma (POAG) and 138 healthy control subjects. Serum retinol concentration in fasting blood samples was determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). All study subjects were given complete ophthalmic examinations and diagnosed by two glaucoma sub-specialists.

RESULTS

Serum retinol concentrations in NTG, POAG, and controls were 338.90 ± 103.23 ng/mL, 405.22 ± 114.12 ng/mL, and 408.84 ± 122.36 ng/mL respectively. NTG patients had lower serum retinol concentrations than POAG (p < 0.001) or healthy controls (p < 0.001). There was no statistical difference between the POAG and healthy controls (p = 0.780). Higher proportion of NTG patients (37.6%) than POAG (17.9%) or controls (21.7%) had serum retinol concentrations lower than 300 ng/mL. Serum retinol was positively correlated with optic nerve sheath diameter (ONSD) (r = 0.349, p = 0.001) in glaucoma patients and not associated with any other demographic features or ophthalmic biometric parameters in the NTG patients. Multivariate logistic regression showed that serum retinol (OR = 0.898, 95CI%: 0.851-0.947) was associated with incident NTG.

CONCLUSIONS

NTG patients had lower serum retinol concentrations. Serum retinol uniquely associated with NTG makes it a new potential option for the diagnosis and treatment of the disease.

Linear interactions between intraocular, intracranial pressure, and retinal vascular pulse amplitude in the fourier domain

Purpose

To compare the retinal vascular pulsatile characteristics in subjects with normal (ICP_n) and high (ICP_h) intracranial pressure and quantify the interactions between intraocular pressure, intracranial pressure, and retinal vascular pulse amplitude in the Fourier domain.

Materials and methods

Twenty-one subjects were examined using modified photoplethysmography with simultaneous ophthalmodynamometry. A harmonic regression model was fitted to each pixel in the time-series, and used to quantify the retinal vascular pulse wave parameters including the harmonic regression wave amplitude (HRW_a). The pulse wave attenuation was measured under different ranges of induced intraocular pressure (IOP_i), as a function of distance along the vessel (V_Dist). Intracranial pressure (ICP) was measured using lumbar puncture. A linear mixed-effects model was used to estimate the correlations between the Yeo-Johnson transformed harmonic regression wave amplitude (HRW_a-YJt) with the predictors (IOP_i, V_Dist and ICP). A comparison of the model coefficients was done by calculating the weighted Beta (β_x) coefficients.

Results

The median HRW_a in the ICP_n group was higher in the retinal veins (4.563, interquartile range (IQR) = 3.656) compared to the retinal arteries (3.475, IQR = 2.458), p<0.0001. In contrast, the ICP_h group demonstrated a reduction in the median venous HRW_a (3.655, IQR = 3.223) and an elevation in the median arterial HRW_a (3.616, IQR = 2.715), p<0.0001. Interactions of the pulsation amplitude with ICP showed a significant disordinal interaction and the loss of a main effect of the Fourier sine coefficient (b_n1) in the ICP_h group, suggesting that this coefficient reflects the retinal vascular response to ICP wave. The linear mixed-effects model (LME) showed the decay in the venous (HRW_a-YJt) was almost twice that in the retinal arteries (−0.067±0.002 compared to −0.028±0.0021 respectively, p<0.00001). The overall interaction models had a total explanatory power of (conditional R²) 38.7%, and 42% of which the fixed effects explained 8.8%, and 5.8% of the variance (marginal R²) for the venous and arterial models respectively. A comparison of the damping effect of V_Dist and ICP showed that ICP had less influence on pulse decay than distance in the retinal arteries (β_ICP = -0.21, se = ±0.017 compared to βVDist=-0.26, se = ±0.019), whereas the mean value was equal for the retinal veins (venous βVDist=-0.42, se = ±0.015, β_ICP = -0.42, se = ±0.019).

Conclusion

The retinal vascular pulsation characteristics in the ICP_h group showed high retinal arterial and low venous pulsation amplitudes. Interactions between retinal vascular pulsation amplitude and ICP suggest that the Fourier sine coefficient b_n1 reflects the retinal vascular response to the ICP wave. Although a matrix of regression lines showed high linear characteristics, the low model explanatory power precludes its use as a predictor of ICP. These results may guide future predictive modelling in non-invasive estimation of ICP using modified photoplethysmography.

Cerebrospinal fluid and ophthalmic disease

PURPOSE OF REVIEW

The purpose of this review is to discuss the contemporary body of literature examining the relationship between cerebrospinal fluid (CSF) and ophthalmic disease. This review focuses on diseases that have a pathogenesis related to the translaminar pressure difference, defined as the pressure difference between the orbital subarachnoid space (OSAS) and the intraocular pressure. The diseases discussed include glaucoma, idiopathic intracranial hypertension, and spaceflight associated neuro-ocular syndrome.

RECENT FINDINGS

The relationship between cerebrospinal and ophthalmic disease has been investigated for over 100 years. Recent research provides insight into the mechanisms that dictate CSF circulation in the OSAS and how alterations in these mechanism lead to disease. This review discusses these recent findings and their relationship to major ophthalmic diseases.

SUMMARY

The recent findings provide insight into diseases that have pathogenic mechanisms that are not fully understood. This information will help physicians gain a clearer understanding of the relationship between CSF and ophthalmic disease and guide future research.

The Association between Myopia and Primary Open-Angle Glaucoma: A Systematic Review and Meta-Analysis

BACKGROUND

Previous studies identified myopia as a risk factor for primary open-angle glaucoma (POAG). However, recent studies have shown different results, the definitive relationship between myopia and POAG remains controversial.

OBJECTIVES

To investigate the relationship between myopia and POAG.

METHODS

Published articles were searched from PubMed, Embase, and Scopus databases between 1970 and 2020. A pooled analysis of the ORs was performed using a random-effects model.

RESULTS

Data on the association between myopia and POAG, were obtained from 16 cross sectional studies, and the pooled OR was 2.26 (95% confidence interval [CI], 1.77 - 2.89, P < 0.001) in random effects model (I2 = 86%; P < 0.01). For the relationship of myopia and POAG progression, data from seven longitudinal cohort studies were included and the pooled OR was 0.85 (95% CI, 0.73 - 0.99, P = 0.042) in the random-effects model (I2 = 88%; P < 0.01).

CONCLUSION

Our findings demonstrated that myopia may be a risk factor associated with POAG and a possible protective factor for POAG progression. It may due to myopia with the presence of a lamina cribrosa defect slow down the visual field loss also POAG progression, further research for underlying mechanisms is still needed.

The association of cerebrospinal fluid pressure with optic nerve head and macular vessel density

The present study aims to investigate the effect of temporary cerebrospinal fluid pressure (CSFP) reduction on optic nerve head (ONH) and macular vessel density (VD) using optical coherence tomography angiography. Forty-four eyes of 44 adults with diagnostic lumbar puncture and CSFP reduction were recruited. Thirty-two eyes of 32 healthy volunteers were controls. ONH and macular VD images were evaluated differences between baseline and after CSFP reduction. The results showed that the mean CSFP decreased from (11.6±2.1) mmHg to (8.2±3.4) mmHg (P<0.001). VD in the macular regions decreased significantly after CSFP reduction in the study group (all P<0.05). The control group showed no significant changes in macular VD (all P>0.05). In the study group, decreased VD in the macular parainferior region was associated with CSFP reduction (R²=0.192, P=0.003), the reduction of macular VD in parafoveal (R²=0.098, P=0.018), parainferior (R²=0.104, P=0.021), parasuperior (R²=0.059, P=0.058), paranasal (R²=0.057, P=0.042), paratemporal (R²=0.079, P=0.026) was associated with mean ocular perfusion pressure decrease following CSFP reduction. ONH vessel density did not differ after CSFP reduction (all P>0.05). In conclusion, macular vessel density decreased in association with CSFP reduction. Retinal vessel density in the macular region is more sensitive than that in peripapillary region after CSFP reduction.

Ophthalmic Artery and Superior Ophthalmic Vein Blood Flow Dynamics in Glaucoma Investigated by Phase Contrast Magnetic Resonance Imaging

PRECIS

Ophthalmic artery (OA) and superior ophthalmic vein (SOV) blood flow were quantified by phase contrast magnetic resonance imaging (PC MRI) and seemed lower in glaucoma. Venous flow dynamics was different in glaucoma patients with a significantly decreased pulsatility.

INTRODUCTION

Studies using color Doppler imaging and optical coherence tomography flowmetry strongly suggested that vascular changes are involved in the pathophysiology of glaucoma, but the venous outflow has been little studied beyond the episcleral veins. This study measured the OA and the SOV flow by PC MRI in glaucoma patients compared with controls.

METHODS

Eleven primary open-angle glaucoma patients, with a mean±SD visual field deficit of -2.3±2.7 dB and retinal nerve fiber layer thickness of 92±13 µ, and 10 controls of similar age, were examined by PC MRI. The mean, maximal and minimal flow over cardiac cycle were measured. The variation of flow (ΔQ) was calculated.

RESULTS

The OA mean±SD mean flow was 13.21±6.79 in patients and 15.09±7.62 mL/min in controls (P=0.35) and the OA maximal flow was 25.70±12.08 mL/min in patients, and 28.45±10.64 mL/min in controls (P=0.22). In the SOV the mean±SD mean flow was 6.46±5.50 mL/min in patients and 7.21±6.04 mL/min in controls (P=0.81) and the maximal flow was 9.06±6.67 in patients versus 11.96±9.29 mL/min in controls (P=0.47). The ΔQ in the SOV was significantly lower in patients (5.45±2.54 mL/min) than in controls (9.09±5.74 mL/min) (P=0.04).

DISCUSSION

Although no significant difference was found, the mean and maximal flow in the OA and SOV seemed lower in glaucoma patients than in controls. The SOV flow waveform might be affected in glaucoma, corroborating the hypothesis of an impairment of venous outflow in those patients.

The Association of Acute Cerebrospinal Fluid Pressure Reduction with Choroidal Thickness

PURPOSE

To investigate the changes in choroidal thickness (CT) after acute cerebrospinal fluid pressure (CSFP) reduction in human subjects.

METHODS

Before and 15 minutes after diagnostic lumbar puncture (LP), 44 patients underwent measurement of CT by swept-source optical coherence tomography. Thirty-two healthy volunteers imitated the body posture of LP procedure and underwent the same measurement before and 15 minutes after body posture change.

RESULTS

After CSFP reduction from 10.9 ± 2.1 mmHg at baseline to 8.1 ± 1.5 mmHg (p < 0.001), CT decreased in subfoveal region (p = 0.005), small to medium vessel layer (SMVL, p < 0.001), peripapillary regions in temporal (p = 0.001), nasal (p < 0.001), superior (p < 0.001) and inferior (p < 0.001), respectively. However, no significant change in CT in the control group after body posture change (all p > 0.05). A significant association between CSFP and the ratio of small to medium vessel layer to total choroidal thickness was found (p = 0.009). The CSFP reduction rate was associated with the change rate of SMVL to total CT portion, for each percent decrease in CSFP was associated with a decrease by 0.22% in the rate of SMVL to total CT portion (R² = 0.125, p = 0.018).

CONCLUSIONS

A significant decrease in subfoveal CT, small to medium vessel layer and peripapillary region were observed following acute CSFP reduction. The CSFP reduction rate was associated with the change rate of small to medium vessel layer to total CT portion.

Optic nerve head anatomy in myopia and glaucoma, including parapapillary zones alpha, beta, gamma and delta: Histology and clinical features

The optic nerve head can morphologically be differentiated into the optic disc with the lamina cribrosa as its basis, and the parapapillary region with zones alpha (irregular pigmentation due to irregularities of the retinal pigment epithelium (RPE) and peripheral location), beta zone (complete RPE loss while Bruch's membrane (BM) is present), gamma zone (absence of BM), and delta zone (elongated and thinned peripapillary scleral flange) within gamma zone and located at the peripapillary ring. Alpha zone is present in almost all eyes. Beta zone is associated with glaucoma and may develop due to a IOP rise-dependent parapapillary up-piling of RPE. Gamma zone may develop due to a shift of the non-enlarged BM opening (BMO) in moderate myopia, while in highly myopic eyes, the BMO enlarges and a circular gamma zone and delta zone develop. The ophthalmoscopic shape and size of the optic disc is markedly influenced by a myopic shift of BMO, usually into the temporal direction, leading to a BM overhanging into the intrapapillary compartment at the nasal disc border, a secondary lack of BM in the temporal parapapillary region (leading to gamma zone in non-highly myopic eyes), and an ocular optic nerve canal running obliquely from centrally posteriorly to nasally anteriorly. In highly myopic eyes (cut-off for high myopia at approximately -8 diopters or an axial length of 26.5 mm), the optic disc area enlarges, the lamina cribrosa thus enlarges in area and decreases in thickness, and the BMO increases, leading to a circular gamma zone and delta zone in highly myopic eyes.

Intereye Comparison of Focal Lamina Cribrosa Defect in Normal-Tension Glaucoma Patients with Asymmetric Visual Field Loss

INTRODUCTION

To evaluate the association of focal lamina cribrosa (LC) defect with asymmetric visual field (VF) loss in normal-tension glaucoma (NTG) through intereye comparisons.

METHODS

Paired eyes were divided into better and worse eyes according to the mean deviation (MD), and ocular parameters were compared between them. Furthermore, patients in the asymmetric group were classified as subgroup A (one eye with LC defect and the fellow one without), subgroup B (both eyes without LC defect), and subgroup C (both eyes with LC defect). Generalized estimation equation approach was used to evaluate the association between ocular parameters and asymmetric VF.

RESULTS

A total of 140 eyes of 70 NTG patients were included in the asymmetric group. LC defects were more common in better eyes than that in worse eyes (27/70 [38.57%] vs. 10/70 [14.29%], p = 0.001), and all eyes with LC defect had myopia. Multivariate analysis revealed that the presence of LC defect was significantly associated with better eyes in the asymmetric group (odds ratio, 0.27; p = 0.001). For subgroup A, eyes with LC defects exhibited lower peak IOP (p = 0.011) and lower mean IOP (p = 0.018) than the fellow eyes without. In addition, longer AL (p = 0.025) and larger tilt ratio (p = 0.032) were found in eyes with LC defects. For subgroup B without LC defects, larger tilt ratio was shown to be a risk factor for VF loss (odds ratio, 6.13; p = 0.001). There was no significant difference of binocular parameters except for MD (p < 0.001) in subgroup C.

CONCLUSIONS

LC defects in myopia were suggested to be associated with better eyes in NTG with asymmetric VF loss. However, in patients without LC defect, larger tilt ratio was a risk factor for VF defect. There might be different pathological mechanisms in asymmetric VF loss for different NTG subtypes.

[Modern view on normal-tension glaucoma]

Glaucoma is a chronic progressive optic neuropathy that causes irreversible loss of visual functions. From the clinical point of view, normal-tension glaucoma (NTG) is regarded in Russian taxonomy as a clinical form of standard primary open-angle glaucoma in which the IOP values stay within the normal range, but the typical progressive visual functions loss is still present. The results of the latest studies put in question the traditional views of NTG pathophysiology that are based solely on intraocular pressure values. New capabilities of diagnostic visualization of central nervous system have considerably broadened our knowledge of the NTG development mechanisms. This article reviews current understanding of the pathogenesis of NTG and its connection to vascular and immune factors, translaminar pressure difference etc. The review also considers the relationship between glaucoma and cognitive defects associated with Alzheimer's and Parkinson's diseases.

Correlation between ocular perfusion pressure and translaminar pressure difference in glaucoma: Evidence for a three-pressure disease?

AIM

To evaluate the correlation between the translaminar pressure difference (TLPD) and the ocular perfusion pressure (OPP) in glaucoma patients.

METHODS

This was a cross-sectional study. Primary open-angle glaucoma (POAG) patients and normal individuals underwent an ophthalmic evaluation as well as blood pressure, height, and weight measurements. Intracranial pressure (ICP) and OPP were calculated using proxy mathematical formulas to attain indirect surrogate parameter values. The TLPD was calculated as intraocular pressure minus ICP. The association between the variables was evaluated using linear and non-linear regression analysis and the correlation estimated with Pearson's correlation coefficient.

RESULTS

The sample included 50 POAG patients and 25 normal subjects. The mean OPP for all 75 subjects (75 eyes) was 53.1 ± 9.3 mmHg and the calculated TLPG was 3.1 ± 4.2 mmHg. TLPG showed a negative correlation with OPP (r = -0.580; 95% CI, -0.690 to -0.366; p < 0.0001).

CONCLUSION

The negative correlation between OPP and TLPD observed in the study substantiates the concept of glaucoma as a three-pressure disease.

[Dependency of intraocular pressure on body posture in glaucoma patients : New approaches to pathogenesis and treatment]

BACKROUND

Human intraocular pressure (IOP) depends on the position of the head in relation to the body in space. Physiologically, the IOP increases in a lying position compared to an upright posture. Microgravity in space also appears to cause an increase in intraocular pressure, accompanied by other ophthalmological changes, which are summarized under the term spaceflight associated neuro-ocular syndrome (SANS). Bed rest studies are being carried out to investigate the effects of weightlessness on the human body. So here there is an intersection between research into SANS and glaucoma. Increased intraocular pressure remains the most important risk factor for glaucoma development and progression that can be influenced by treatment. The influence of position-dependent IOP fluctuations on glaucoma is still not sufficiently understood.

MATERIALS AND METHODS

A literature search was carried in PubMed on the subject of IOP fluctuations related to posture. Analysis and evaluation of the published study results and a summary of available clinical data.

RESULTS

The increase in IOP when changing from a seated to a lying body position is greater in glaucoma patients with an increase of up to 8.6 mm Hg compared to healthy subjects with an increase up to 5 mm Hg. In small pilot studies the increase in lying IOP in some glaucoma patients and healthy volunteers could be attenuated by elevation of the head by 30%. A lower compartmental pressure in the subarachnoid space has been associated with glaucoma and may represent a risk factor for glaucoma development. Not only the level of IOP but also IOP fluctuations were associated with an increased risk of disease progression.

CONCLUSION

The clinical significance of IOP peaks during sleep on glaucoma is still not sufficiently understood. New methods for continuous IOP measurement offer promising opportunities for further research into the importance of IOP fluctuations related to changes of body and head posture.

The Diagnosis and Treatment of Glaucoma

BACKGROUND

Glaucoma is a group of chronically progressive disorders of the optic nerve. In this article, we present the epidemiology of and risk factors for glaucoma, as well as the diagnostic work-up and treatment options.

METHODS

This review is based on pertinent publications retrieved by a selective search in Medline and the Cochrane Library, supplemented by further articles chosen by the authors.

RESULTS

In Europe, the prevalence of glaucoma is 2.93% among persons aged 40 to 80 years. The prevalence rises with age, reaching 10% in persons over 90 years old. The available diagnostic methods include ophthalmoscopy, tonometry, perimetry, and imaging techniques. The treatment of glaucoma is focused on lowering the intraocular pressure with topical drugs, laser therapy, and glaucoma surgery. In patients with manifest glaucoma, lowering the intraocular pressure prevents the progression of visual field defects, with a number needed to treat of 7.

CONCLUSION

The diagnostic evaluation of glaucoma rests on multiple pillars, all of which must be considered for establishing the diagnosis and defining the desired target pressure: these are, among others, the intraocular pressure and ocular function and morphology. Individually tailored pressure-lowering treatment should be evaluated in regularly scheduled follow-up visits for assessment of function and morphology and adjusted as necessary to minimize the risk of progression.

Effect of Changing Heart Rate on the Ocular Pulse and Dynamic Biomechanical Behavior of the Optic Nerve Head

Purpose

To study the effect of changing heart rate on the ocular pulse and the dynamic biomechanical behavior of the optic nerve head (ONH) using a comprehensive mathematical model.

Methods

In a finite element model of a healthy eye, a biphasic choroid consisted of a solid phase with connective tissues and a fluid phase with blood, and the lamina cribrosa (LC) was viscoelastic as characterized by a stress-relaxation test. We applied arterial pressures at 18 ocular entry sites (posterior ciliary arteries), and venous pressures at four exit sites (vortex veins). In the model, the heart rate was varied from 60 to 120 bpm (increment: 20 bpm). We assessed the ocular pulse amplitude (OPA), pulse volume, ONH deformations, and the dynamic modulus of the LC at different heart rates.

Results

With an increasing heart rate, the OPA decreased by 0.04 mm Hg for every 10 bpm increase in heart rate. The ocular pulse volume decreased linearly by 0.13 µL for every 10 bpm increase in heart rate. The storage modulus and the loss modulus of the LC increased by 0.014 and 0.04 MPa, respectively, for every 10 bpm increase in heart rate.

Conclusions

In our model, the OPA, pulse volume, and ONH deformations decreased with an increasing heart rate, whereas the LC became stiffer. The effects of blood pressure/heart rate changes on ONH stiffening may be of interest for glaucoma pathology.

Biomechanical research into lamina cribrosa in glaucoma

Glaucoma, a leading cause of irreversible blindness, poses a considerable public health challenge and burden. Mechanical models of the lamina cribrosa under elevated intraocular pressure at different scales, contributing significantly to uncovering the glaucomatous pathogenesis, are discussed. Meanwhile, the open issues and avenues for further development are highlighted.

Unraveling the Enigma of Nonarteritic Anterior Ischemic Optic Neuropathy

Non-arteritic anterior ischemic optic neuropathy (NAON) is the second most common optic neuropathy in adults. Despite extensive study, the etiology of NAION is not definitively known. The best evidence suggests that NAION is caused by an infarction in the region of the optic nerve head (ONH), which is perfused by paraoptic short posterior ciliary arteries (sPCAs) and their branches. To examine the gaps in knowledge that defies our understanding of NAION, a historical review was performed both of anatomical investigations of the ONH and its relevant blood vessels and the evolution of clinical understanding of NAION. Notably, almost all of the in vitro vascular research was performed prior our current understanding of NAION, which has largely precluded a hypothesis-based laboratory approach to study the etiological conundrum of NAION. More recent investigative techniques, like fluorescein angiography, have provided valuable insight into vascular physiology, but such light-based techniques have not been able to image blood vessels located within or behind the dense connective tissue of the sclera and laminar cribrosa, sites that are likely culpable in NAION. The lingering gaps in knowledge clarify investigative paths that might be taken to uncover the pathogenesis of NAION and possibly glaucoma, the most common optic neuropathy for which evidence of a vascular pathology also exists.

8 hrs Safety Evaluation Of A Multi-Pressure Dial In Eyes With Glaucoma: Prospective, Open-Label, Randomized Study

Purpose

To investigate the safety and tolerability of the multi-pressure dial with a continuous 8-hr duration in subjects with open-angle glaucoma.

Design

Prospective, controlled open-label, randomized, single site study.

Subjects

Twenty eyes of 10 subjects with open-angle glaucoma were fitted with a multi-pressure dial and randomized to negative pressure application of −10 mmHg in one eye for 8 (continuous) hours and ambient atmospheric pressure in the contralateral eye.

Methods

Main safety outcome measures include best-corrected visual acuity (BCVA), intraocular pressure (IOP) changes from baseline after negative pressure application, slit lamp and dilated fundus exam findings, and rate of adverse events. Subjective assessments were administered both hourly during the 8-hr study period and immediately following the study period.

Results

There were no statistically significant changes in IOP, BCVA or TBUT immediately following the 8-hr study period or at the 1-week follow-up visit. Patient-reported tolerability was favorable with a mean response of 1.8 ± 0.4 (scale → 1=best, 10 = worst). Subjects also reported positive interest in the MPD as a glaucoma therapy with a mean response of 1.8 ± 0.5 (scale → 1=best, 10 = worst). One adverse event was reported (headache) and resolved at conclusion of the Day 0 visit.

Conclusion

The MPD demonstrated favorable safety with key parameters remaining stable after an 8-hr wear with negative pressure. Negative pressure application through the MPD was well tolerated by subjects enrolled in the study. The favorable findings demonstrate the safety of sustained delivery of negative pressure over a continuous, uninterrupted 8-hr duration.

Determinants of maximum cup depth in non-glaucoma and primary open-angle glaucoma subjects: a population-based study

Background/objectives

To study the associations of intraocular pressure (IOP) and retinal vessel diameters: central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) with the maximum cup depth (MCD) in subjects with and without POAG.

Subjects/methods

Eligible subjects from the Handan Eye Study. All participants underwent physical and comprehensive eye examinations. Univariable and multivariable linear regression models assessed the association between MCD and other parameters.

Results

Four thousand one hundred and ninety-four eligible nonglaucoma and 40 POAG subjects were analyzed. On univariable analysis, deeper MCD was significantly associated with younger age, male gender, lower systolic blood pressure (BP), higher IOP, higher estimated cerebro-spinal fluid pressure (ECSFP), lower estimated trans-laminal cribrosa pressure difference (ETLCPD), longer axial length, narrower CRAE, narrower CRVE, larger disc area (DA) and a lower prevalence of hypertension and diabetes. On multivariable analysis, significant independent determinants of MCD were larger DA (P < 0.001; beta: 0.042; B: 0.20; 95% CI: 0.19, 0.22), younger age (P < 0.001; beta: −0.09; B: −0.002; 95% CI: −0.003, −0.001), higher IOP (P < 0.01; beta: 0.040; B: 0.003; 95% CI: 0.001, 0.005), and narrower CRAE (P < 0.001; beta: −0.06; B: −0.001; 95% CI: −0.001, −0.0003). On adding ECSFP and ETLCPD to the model, MCD was associated with IOP but not with estimated CSFP and TLCPD. A 1 μm decrease in CRAE or 1 mmHg increase of IOP was associated with a 1 μm increase of MCD (P < 0.001) and 3 μm increase of MCD respectively (P = 0.009).

Conclusions

Narrow CRVE and higher IOP are associated with an increase in MCD.

Selective Early Glial Reactivity in the Visual Pathway Precedes Axonal Loss, Following Short-Term Cerebrospinal Fluid Pressure Reduction

Purpose

To examine the early glial reactivity and neuron damage in response to short-term cerebrospinal fluid pressure (CSFp) reduction, as compared with intraocular pressure (IOP) elevation.

Methods

The experiment included 54 male Sprague-Dawley rats with elevated translaminar cribrosa pressure difference (TLPD), defined as IOP minus CSFp. These rats underwent either continuous CSF drainage for 6 hours (n = 18), or unilateral IOP elevation to 40 mm Hg for 6 hours (n = 18). For control, 18 normal rats were anesthetized for 6 hours. Orthograde axonal transport was examined by intravitreal injection of 3% rhodamine-β-isothiocyanate. We also used transmission electron microscopy to display the ultrastructural features of retinal ganglion cell axons in the optic nerve head. Early glial reactivity in the retina, lateral geniculate nucleus (LGN), and superior colliculus (SC) was detected by immunostaining and Western blot for the glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS). We also observed the glial reactivity in the inferior colliculus and hippocampus to rule out possible influences of CSF dynamics and composition.

Results

Anterograde staining with 3% rhodamine-β-isothiocyanate revealed decreased fluorescence intensity of the SC and LGN projected from both lower CSFp and higher IOP eyes. Transmission electron microscopy showed loss of axons from the optic nerve head in the high-IOP group, but not in the low-CSFp group. Compared with the anesthesia control group, GFAP expression was significantly increased in the retina, LGN, and SC, whereas GS expression was only increased in the retina following CSFp reduction. However, their expressions were not significantly elevated in the inferior colliculus and hippocampus. In the high-IOP group, expressions of GFAP and GS were significantly increased in the retina, LGN, and SC.

Conclusions

Visual system neurons may be much more sensitive than other nervous tissues. Following short-term CSFp reduction, early glial reactivity may precede axonal loss. Changes of translaminar cribrosa pressure difference in both experimental low-CSFp and high-IOP groups induce selective early glial reactivity. The neuron damage from abnormally low CSFp may be pathogenetically similar to high IOP.

Investigating spontaneous retinal venous pulsation using Doppler optical coherence tomography

We demonstrate the advantages of optical coherence tomography (OCT) imaging for investigation of spontaneous retinal venous pulsation (SRVP). The pulsatile changes in venous vessel caliber are analyzed qualitatively and quantitatively using conventional intensity-based OCT as well as the functional extension Doppler OCT (DOCT). Single-channel and double-channel line scanning protocols of our multi-channel OCT prototype are employed to investigate venous pulsatile caliber oscillations as well as venous flow pulsatility in the eyes of healthy volunteers. A comparison to recordings of scanning laser ophthalmoscopy (SLO) – a standard en-face imaging modality for evaluation of SRVP – is provided, emphasizing the advantages of tomographic image acquisition. To the best of our knowledge, this is the first quantitative time-resolved investigation of SRVP and associated retinal perfusion characteristics using OCT.

Contrast-Enhanced 3D-FLAIR Imaging of the Optic Nerve and Optic Nerve Head: Novel Neuroimaging Findings of Idiopathic Intracranial Hypertension

BACKGROUND AND PURPOSE

The sensitivity of contrast-enhanced 3D-FLAIR has not been assessed in patients with idiopathic intracranial hypertension. The purpose of this study was to evaluate whether hyperintensity of the optic nerve/optic nerve head on contrast-enhanced 3D-FLAIR imaging is associated with papilledema in patients with idiopathic intracranial hypertension.

MATERIALS AND METHODS

A retrospective review was conducted from 2012 to 2015 of patients with clinically diagnosed idiopathic intracranial hypertension and age- and sex-matched controls who had MR imaging with contrast-enhanced 3D-FLAIR. Two neuroradiologists graded each optic nerve/optic nerve head on a scale of 0-3. This grade was then correlated with the Frisén Scale, an ophthalmologic scale used for grading papilledema from 0 (normal) to 5 (severe edema). To estimate the correlation between the MR imaging and Frisén scores, we calculated the Kendall τ coefficient.

RESULTS

Forty-six patients (3 men, 43 women) with idiopathic intracranial hypertension and 61 controls (5 men, 56 women) with normal findings on MR imaging were included in this study. For both eyes, there was moderate correlation between the 2 scales (right eye: τ = 0.47; 95% CI, 0.31-0.57; left eye: τ = 0.38; 95% CI, 0.24-0.49). Interreader reliability for MR imaging scores showed high interreader reliability (right eye: κ = 0.76; 95% CI, 0.55-0.88; left eye: κ = 0.87; 95% CI, 0.78-0.94). Contrast-enhanced 3D-FLAIR imaging correlates with the Frisén Scale for moderate-to-severe papilledema and less so for mild papilledema.

CONCLUSIONS

Hyperintensity of the optic nerve/optic nerve head on contrast-enhanced 3D-FLAIR is sensitive for the detection of papilledema in patients with idiopathic intracranial hypertension, which may be useful when prompt diagnosis is crucial.

Normal tension glaucoma: from the brain to the eye or the inverse?

Glaucoma is a chronic, progressive optic neuropathy characterized by the loss of peripheral vision first and then central vision. Clinically, normal tension glaucoma is considered a special subtype of glaucoma, in which the patient's intraocular pressure is within the normal range, but the patient experiences typical glaucomatous changes. However, increasing evidence has challenged the traditional pathophysiological view of normal tension glaucoma, which is based only on intraocular pressure, and breakthroughs in central nervous system imaging may now greatly increase our knowledge about the mechanisms underlying normal tension glaucoma. In this article, we review the latest progress in understanding the pathogenesis of normal tension glaucoma and in developing imaging techniques to detect it, to strengthen the appreciation for the connection between normal tension glaucoma and the brain.

All roads lead to glaucoma: Induced retinal injury cascades contribute to a common neurodegenerative outcome

Glaucoma describes a distinct optic neuropathy with complex etiology and a variety of associated risk factors, but with similar pathological endpoints. Risk factors such as age, increased intraocular pressure (IOP), low mean arterial pressure, and autoimmune disease, can all be associated with death of retinal ganglion cells (RGCs) and optic nerve head remodeling. Today, IOP management remains the standard of care, even though IOP elevation is not pathognomonic of glaucoma, and patients can continue to lose vision despite effective IOP control. A contemporary view of glaucoma as a complex, neurodegenerative disease has developed, along with the recognition of a need for new disease modifying retinal treatment strategies and improved outcomes. However, the distinction between risk factors triggering the disease process and retinal injury responses is not always clear. In this review, we attempt to distinguish between the various triggers, and their association with subsequent key RGC injury mechanisms. We propose that distinct glaucomatous risk factors result in similar retinal and optic nerve injury cascades, including oxidative and metabolic stress, glial reactivity, and altered inflammatory responses, which induce common molecular signals to induce RGC apoptosis. This organization forms a coherent disease framework and presents conserved targets for therapeutic intervention that are not limited to specific risk factors.

Citicoline and Retinal Ganglion Cells: Effects on Morphology and Function

BACKGROUND

Retinal ganglion cells (RGCs) are the nervous retinal elements which connect the visual receptors to the brain forming the nervous visual system. Functional and/or morphological involvement of RGCs occurs in several ocular and neurological disorders and therefore these cells are targeted in neuroprotective strategies. Cytidine 5-diphosphocholine or Citicoline is an endogenous compound that acts in the biosynthesis of phospholipids of cell membranes and increases neurotransmitters' levels in the Central Nervous System. Experimental studies suggested the neuromodulator effect and the protective role of Citicoline on RGCs. This review aims to present evidence of the effects of Citicoline in experimental models of RGCs degeneration and in human neurodegenerative disorders involving RGCs.

METHODS

All published papers containing experimental or clinical studies about the effects of Citicoline on RGCs morphology and function were reviewed.

RESULTS

In rodent retinal cultures and animal models, Citicoline induces antiapoptotic effects, increases the dopamine retinal level, and counteracts retinal nerve fibers layer thinning. Human studies in neurodegenerative visual pathologies such as glaucoma or non-arteritic ischemic neuropathy showed a reduction of the RGCs impairment after Citicoline administration. By reducing the RGCs' dysfunction, a better neural conduction along the post-retinal visual pathways with an improvement of the visual field defects was observed.

CONCLUSION

Citicoline, with a solid history of experimental and clinical studies, could be considered a very promising molecule for neuroprotective strategies in those pathologies (i.e. Glaucoma) in which morpho-functional changes of RGCc occurs.

Pioneer of Chinese Ophthalmology--130th Anniversary of Beijing Tongren Hospital

Much has been achieved in clinical and scientific research in the past 130 years by Beijing Tongren Hospital, which has evolved from an eye clinic to a comprehensive hospital with an ophthalmology department known as one of the best in China. This article presents the most historic moments and events in the development of a hospital with the largest eye care service volume. In addition, given the leading position of Tongren, the development of ophthalmology in Tongren is also the epitome of the development of modern ophthalmology in China. Beijing Institute of Ophthalmology (BIO) was established in 1959 as an affiliated institution under Tongren, aiming at carrying out applied science and basic science research, and directors of BIO have thus far served 4 terms as president of the Chinese Ophthalmological Society. In 2002, Beijing Tongren Eye Center (hereafter referred to as the Eye Center) was established to combine all the ophthalmic resources within Tongren. In 2017, the Eye Center alone had a surgical volume of 78,223, with surgeries for cataract, refractive errors, fundus, glaucoma, and corneal disease being the 5 most common, and 902,409 outpatient visits. Equipped with the leading experts and equipment, Tongren is dedicated to the battle against major eye diseases by carrying out large population-based epidemiological surveys and basic science research on pathogenesis and effective treatments, thereby making contributions to the development of the science of ophthalmology along with the delivery of eye care services in China and beyond.

In vivo optic nerve head mechanical response to intraocular and cerebrospinal fluid pressure: imaging protocol and quantification method

This study presents a quantification method for the assessment of the optic nerve head (ONH) deformations of the living human eye under acute intraocular pressure (IOP) elevation and change of cerebrospinal fluid pressure (CSFP) with body position. One eye from a brain-dead organ donor with open-angle glaucoma was imaged by optical coherence tomography angiography during an acute IOP and CSFP elevation test. Volumetric 3D strain was computed by digital volume correlation. With increase in IOP the shear strain consistently increased in both sitting and supine position (p < 0.001). When CSFP was increased at constant IOP by changing body position, a global reduction in the ONH strain was observed (−0.14% p = 0.0264). Strain in the vasculature was significantly higher than in the structural tissue (+0.90%, p = 0.0002). Retinal nerve fiber layer (RNFL) thickness strongly associated (ρ = −0.847, p = 0.008) with strain in the peripapillary sclera (ppScl) but not in the retina (p = 0.433) and lamina (p = 0.611). These initial results show that: CSFP independently to IOP modulates strain in the human ONH; ppScl strains are greater than strains in lamina and retina; strain in the retinal vasculature was higher than in the structural tissue; In this glaucoma eye, higher ppScl strain associated with lower RNFL thickness.

Intracranial and Intraocular Pressure at the Lamina Cribrosa: Gradient Effects

PURPOSE OF REVIEW

A pressure difference between the intraocular and intracranial compartments at the site of the lamina cribrosa has been hypothesized to have a pathophysiological role in several optic nerve head diseases. This paper reviews the current literature on the translamina cribrosa pressure difference (TLCPD), the associated pressure gradient, and its potential pathophysiological role, as well as the methodology to assess TLCPD.

RECENT FINDINGS

For normal-tension glaucoma (NTG), initial studies indicated low intracranial pressure (ICP) while recent findings indicate that a reduced ICP is not mandatory. Data from studies on the elevated TLCPD as a pathophysiological factor of NTG are equivocal. From the identification of potential postural effects on the cerebrospinal fluid (CSF) communication between the intracranial and retrolaminar space, we hypothesize that the missing link could be a dysfunction of an occlusion mechanism of the optic nerve sheath around the optic nerve. In upright posture, this could cause an elevated TLCPD even with normal ICP and we suggest that this should be investigated as a pathophysiological component in NTG patients.

Measurement and Associations of the Optic Nerve Subarachnoid Space in Normal Tension and Primary Open-Angle Glaucoma

PURPOSE

To measure the area of the optic nerve subarachnoid space (ONSASA) in patients with normal tension glaucoma (NTG), primary open-angle glaucoma (POAG), and controls and examine its association with relevant ocular and systemic parameters.

DESIGN

Cross-sectional study.

METHODS

The study included 40 patients with NTG, 42 with POAG, and 45 healthy controls. B-scan ultrasound was performed binocularly, using a 12.5-MHz linear array probe. The measurement of the optic nerve subarachnoid space (ONSAS) and calculation of the ONSASA using ImageJ 1.51e analysis software was done by 2 experienced observers in a masked manner.

RESULTS

The ONSASA between 3 and 7 mm behind the globe in NTG (5.15 ± 0.81 mm²) was significantly smaller than that in the POAG (6.24 ± 1.62 mm², P = .0008) or control (6.40 ± 2.20 mm²; P = .0007) groups. ONSASA in the POAG and control groups were not significantly different (P = .13). ONSASA was significantly associated with mean IOP (P = .0004) and highest IOP (P = .0007). The optic nerve sheath diameter in NTG compared to POAG was significantly different at 3 mm (4.46 ± 0.43 mm vs 4.79 ± 0.40 mm, P = .0007), 5 mm (4.40 ± 0.39 mm vs 4.65 ± 0.47 mm, P = .003), and 7 mm (4.36 ± 0.35 mm vs 4.61 ± 0.30 mm, P = .004) behind the globe.

CONCLUSIONS

The ONSASA is smaller in NTG as compared to normal control. This is compatible with a lower cerebrospinal fluid pressure in the optic nerve in NTG, implying that trans-lamina cribrosa pressure difference might be abnormally higher in the NTG group than in normal controls.