Translamina Cribrosa Pressure Difference as Potential Element in the Pathogenesis of Glaucomatous Optic Neuropathy

Intraocular pressure and its determinants in a very old population. The ural very old study

Purpose

To explore intraocular pressure (IOP) and its associated parameters in an aged population.

Methods

The epidemiologic Ural Very Old Study (UVOS) conducted in Bashkortostan/Russia included 1526 participants with an age of ≥85 years. Besides a whole series of ocular and systemic examinations, IOP was determined applying non-contact tonometry. Body mass index, diastolic blood pressure and age were the factors used to estimate the cerebrospinal fluid pressure (CSFP).

Results

The study consisted of 904 participants (age: 88.6 ± 2.7 years) with available IOP readings and without anti-glaucomatous therapy. Mean IOP was 14.5 ± 5.1 mmHg (median: 14 mm Hg; Q1:11; Q3:16; 95%CI:8,25) and 14.8 ± 4.6 mmHg (median: 14 mm Hg; Q1:12; Q3:17; 95%CI:8,28) in the right and left eyes, respectively. Higher IOP correlated (multivariable analysis; correlation coefficient r2:0.32) with female sex (P < 0.001), more sedentary lifestyle (P = 0.006), higher estimated CSFP (P < 0.001), higher total protein serum concentration (P < 0.001), stronger hand grip force (P = 0.01), thicker central cornea (P < 0.001), longer axial length (P = 0.01), absence of previous cataract surgery (P = 0.001), higher degree of pseudoexfoliation (P = 0.02, and thinner peripapillary retinal nerve fiber layer thickness (P = 0.004). Using this that model, IOP reading enlarged by 0.22 mmHg (95% CI: 0.09, 0.35) for each increase in estimated CSFP by 1 mm Hg, by 0.03 mm Hg (95% CI: 0.02,0.05) for each thickening in central corneal thickness by 1 μm, by 0.56 mm Hg (95%CI: 0.13,1.00) for each axial elongation by 1 mm, and by 0.40 mmHg (95% CI: 0.06,0.74) for each increase in the degree of pseudoexfoliation, and it decreased by 0.40 mmHg (95% CI: 0.06,0.74) by cataract surgery.

Conclusions

In this study population aged 85+years, IOP readings showed similar relationships as in younger study populations, including positive associations with higher estimated CSFP and longer axial length and a negative association with cataract surgery.

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.

Cerebrospinal Fluid Pressure Reduction Induces Glia-Mediated Retinal Inflammation and Leads to Retinal Ganglion Cell Injury in Rats

Low intracranial pressure (LICP)-induced translaminar cribrosa pressure difference (TLCPD) elevation has been proven as a risk factor in glaucomatous neurodegeneration, whereas the underlying retinal immune features of LICP-induced retinal ganglion cells (RGC) injury remain elusive. Here, we identified the retinal immune characteristics of LICP rats, and minocycline (Mino) treatment was utilized to analyze its inhibitory role in glia-mediated retinal inflammation of LICP rats. The results showed that retrograde axonal transport was decreased in LICP rats without significant RGC loss, indicating the RGC injury was at an early stage before the morphological loss. The activation of retinal microglia and astrocytes with morphologic and M1 or A1-marker alternations was detected in TLCPD elevation rats, the activation level is more dramatic in HIOP rats than in the LICP rats (P<0.05). Besides, we detected reduced retinal tight junction protein expressions, accompanied by specific imbalance patterns of T lymphocytes in the retina of both LICP and HIOP rats (P<0.05). Further Mino treatment showed an effective inhibitory role in glia-driven inflammatory responses in LICP rats, including improving retrograde axonal transport, inhibiting retinal glial activation and proinflammatory subtype polarization, and alleviating the blood-retina barrier compromise. This study identified the glia-mediated retinal inflammation features triggered by LICP stimulus, and Mino application exhibited an effective role in the inhibition of retinal glia-mediated inflammation in LICP-induced TLCPD elevation rats.

IMI-Nonpathological Human Ocular Tissue Changes With Axial Myopia

Purpose

To describe nonpathological myopia-related characteristics of the human eye.

Methods

Based on histomorphometric and clinical studies, qualitative and quantitative findings associated with myopic axial elongation are presented.

Results

In axial myopia, the eye changes from a spherical shape to a prolate ellipsoid, photoreceptor, and retinal pigment epithelium cell density and total retinal thickness decrease, most marked in the retroequatorial region, followed by the equator. The choroid and sclera are thin, most markedly at the posterior pole and least markedly at the ora serrata. The sclera undergoes alterations in fibroblast activity, changes in extracellular matrix content, and remodeling. Bruch's membrane (BM) thickness is unrelated to axial length, although the BM volume increases. In moderate myopia, the BM opening shifts, usually toward the fovea, leading to the BM overhanging into the nasal intrapapillary compartment. Subsequently, the BM is absent in the temporal region (such as parapapillary gamma zone), the optic disc takes on a vertically oval shape, the fovea-optic disc distance elongates without macular BM elongation, the angle kappa reduces, and the papillomacular retinal vessels and nerve fibers straighten and stretch. In high myopia, the BM opening and the optic disc enlarge, the lamina cribrosa, the peripapillary scleral flange (such as parapapillary delta zone) and the peripapillary choroidal border tissue lengthen and thin, and a circular gamma and delta zone develop.

Conclusions

A thorough characterization of ocular changes in nonpathological myopia are of importance to better understand the mechanisms of myopic axial elongation, pathological structural changes, and psychophysical sequelae of myopia on visual function.

Wedge Defects on Optical Coherence Tomography Angiography of the Peripapillary Retina in Glaucoma: Prevalence and Associated Clinical Factors

PRCIS

Among subjects with glaucoma, wedge-shaped defects on optical coherence tomography angiography (OCTA) were associated with disc hemorrhages (DH), paracentral visual field (VF) defects, increased cup-to-disc ratio (CDR), and thinner retinal nerve fiber layer (RNFL).

PURPOSE

To examine determinants of wedge defects on peripapillary OCTA in glaucoma.

MATERIALS AND METHODS

A total of 278 eyes of 186 subjects with mild to severe primary open-angle glaucoma underwent 6×6 spectral-domain OCTA imaging of the superficial peripapillary retina from 2016 to 2020 at an academic practice. Wedge defects were defined as focal microvasculature loss that extends outward from the optic nerve in an arcuate, wedge shape. Logistic regression models controlling for intereye correlation identified variables significantly associated with wedge defects. Eyes with profound microvasculature loss in both hemispheres were excluded. Candidate variables included: age, sex, race or ethnicity, diabetes, hypertension, follow-up duration, baseline untreated intraocular pressure, intraocular pressure at time of imaging, DH history, paracentral VF defects, CDR, central corneal thickness, spherical equivalent, VF mean deviation, RNFL thickness, and glaucoma stage.

RESULTS

Of 278 eyes, 126 (45.3%) had wedge defects in at least 1 hemisphere. In our multivariable logistic regression model, wedge defects were associated with DH history [odds ratio (OR): 3.19, 95% confidence interval (CI): 1.05-9.69, P=0.041], paracentral VF defects [OR: 4.38 (95% CI: 2.11-9.11), P<0.0001], larger CDR [OR: 1.27 (95% CI: 1.03-1.56), P=0.024, per 0.1 increase], and thinner RNFL [OR: 1.71 (95% CI: 1.25-2.34), P=0.0009, per 10 μm decrease].

CONCLUSION

DH history and paracentral VF defects were independently associated with wedge defects on OCTA, which was present in 45.3% of primary open-angle glaucoma patients. These findings may provide insight into glaucoma pathogenesis.

Special Cerebral and Cerebrospinal Features in Primary Open Angle Glaucoma and Normal Tension Glaucoma

In addition to aqueous humour and blood, cerebrospinal fluid also plays an important part in the pathophysiology of primary open-angle glaucoma (POAG) and, in particular, normal-tension glaucoma (NTG). Apart from the important role of CSF pressure in papillary congestion, the composition of the CSF and its flow rate are relevant. CSF is in contact with the brain, the spinal canal and the optic nerve. In neurodegenerative disease, one potential pathophysiological factor, apart from an altered composition of the CSF, is a decrease in flow rate. Changes in CSF composition and flow rate have also been described in the perioptic subarachnoid space of the optic nerve in patients with normal tension glaucoma. Such findings indicate that primary open angle glaucoma and normal tension glaucoma especially, might be due to a neurodegenerative process.

Comparison of Superior and Inferior Visual Field Asymmetry Between Normal-tension and High-tension Glaucoma

PRECIS

Increased severity of glaucoma heightened the hemispherical asymmetry in normal-tension and high-tension glaucoma (NTG/HTG), especially NTG. NTG showed localized superior defects in the central and paracentral areas whereas HTG showed mild asymmetry with diffuse defects.

PURPOSE

The purpose of this study was to compare the patterns of visual field (VF) defects according to glaucoma severity in NTG and HTG.

MATERIALS AND METHODS

A total of 1458 eyes with NTG (936) and HTG (522) were classified by mean deviation values into mild, moderate, and severe. The mean total deviation (mTD) values for each nasal, central, paracentral, arcuate 1, and arcuate 2 region of the Glaucoma Hemifield Test (GHT) were calculated. The differences in mTD between the superior and inferior hemifields of NTG and HTG were compared, and the degree of hemifield asymmetry was plotted.

RESULTS

In NTG and HTG, the mTDs of the 5 regions of the superior GHT were significantly worse than those of the corresponding regions of the inferior GHT at all severity levels except for mild HTG. However, NTG showed significantly greater asymmetry than HTG in 2 regions at mild, 3 at moderate, and all 5 at severe. Moderate and severe NTG showed severe asymmetry with localized superior field defects concentrated at the central and paracentral areas with >8 dB asymmetry. However, in all HTG groups showed mild asymmetry with diffuse defects.

CONCLUSIONS

The superior hemifield was more severely affected than the inferior hemifield in NTG and HTG. As the severity of glaucoma increased, so did the asymmetry in both groups, with NTG showing more profound asymmetric VF defects in the central and paracentral areas whereas HTG did not. Different VF patterns suggest differing pathologic mechanisms and possible need for different therapeutic strategies in NTG and HTG.

Lipocalin-type Prostaglandin D Synthase Concentration Gradients in the Cerebrospinal Fluid in Normal-tension Glaucoma Patients with Optic Nerve Sheath Compartmentation

Objective

To report on the lipocalin-type prostaglandin D synthase (L-PGDS) concentrations in the cerebrospinal fluid (CSF) of the perioptic and lumbar subarachnoid space (SAS) in patients with radiologically proven optic nerve (ON) sheath compartmentation presenting as normal-tension glaucoma (NTG).

Methods

Retrospective biochemical analysis of CSF in thirteen patients with ON sheath compartmentation presenting as NTG (four females, mean age 70±8 years). CSF was sampled from the SAS of the ON during ON sheath fenestration for ON sheath compartmentation and from the lumbar SAS at the time of lumbar puncture. Nephelometry was used for the quantification of L-PGDS and albumin concentration. Albumin was measured in order to assess the amount of contamination with serum in the CSF samples taken from the ON SAS. Main outcome measures were L-PGDS concentrations in the CSF of the perioptic and lumbar SAS.

Results

Mean L-PGDS concentration was 24±8 mg/L in the lumbar SAS compared to 33±27 mg/L without correction of serum contamination and 45±39 mg/L after correction of serum contamination in the perioptic SAS. The difference between the lumbar and the perioptic SAS was statistically significant (P=0.0047 without correction of serum contamination, P=0.0002 with correction of serum contamination; Mann-Witney U-test).

Conclusion

This study demonstrates a concentration gradient of L-PGDS levels within the CSF with a statistically significant higher concentration in the compartmentalized perioptic SAS compared to that in the lumbar SAS. Biochemical changes in the perioptic SAS might be involved in the pathophysiology in NTG patients with ON sheath compartmentation.

Is stagnant cerebrospinal fluid involved in the pathophysiology of normal tension glaucoma

Current concepts of the pathophysiology of normal tension glaucoma (NTG) include intraocular pressure, vascular dysregulation and the concept of a translaminar pressure gradient. Studies on NTG performed with cisternography demonstrated an impaired cerebrospinal fluid (CSF) dynamics in the subarachnoid space of the optic nerve sheath, most pronounced behind the lamina cribrosa. Stagnant CSF might be another risk factor for NTG.

Estimating three-dimensional outflow and pressure gradients within the human eye

In this paper we set the previously reported pressure-dependent, ordinary differential equation outflow model by Smith and Gardiner for the human eye, into a new three-dimensional (3D) porous media outflow model of the eye, and calibrate model parameters using data reported in the literature. Assuming normal outflow through anterior pathways, we test the ability of 3D flow model to predict the pressure elevation with a silicone oil tamponade. Then assuming outflow across the retinal pigment epithelium is normal, we test the ability of the 3D model to predict the pressure elevation in Schwartz-Matsuo syndrome. For the first time we find the flow model can successfully model both conditions, which helps to build confidence in the validity and accuracy of the 3D pressure-dependent outflow model proposed here. We employ this flow model to estimate the translaminar pressure gradient within the optic nerve head of a normal eye in both the upright and supine postures, and during the day and at night. Based on a ratio of estimated and measured pressure gradients, we define a factor of safety against acute interruption of axonal transport at the laminar cribrosa. Using a completely independent method, based on the behaviour of dynein molecular motors, we compute the factor of safety against stalling the dynein molecule motors, and so compromising retrograde axonal transport. We show these two independent methods for estimating factors of safety agree reasonably well and appear to be consistent. Taken together, the new 3D pressure-dependent outflow model proves itself to capable of providing a useful modeling platform for analyzing eye behaviour in a variety of physiological and clinically useful contexts, including IOP elevation in Schwartz-Matsuo syndrome and with silicone oil tamponade, and potentially for risk assessment for optic glaucomatous neuropathy.

Normal-tension glaucoma: Pathogenesis and genetics

Normal-tension glaucoma (NTG) is a multifactorial optic neuropathy which, similar to open-angle glaucomas, is characterized by progressive retinal ganglion cell death and glaucomatous visual field loss. The major distinction of NTG from open-angle glaucomas is that the intraocular pressure (IOP) does not exceed the normal range. Missing the major risk factor and target of therapy, the elevated IOP, NTG poses a clinical challenge. Several insightful reviews have been published on the pathophysiology of NTG describing the possible underlying mechanisms. The current literature available also suggests that a significant percentage of patients with NTG (as high as 21%) have a family history of glaucoma, indicating a genetic predisposition to the disease. These facts strengthen the indication that NTG remains an enigmatic process. The aim of this review was to summarize the vascular, mechanical and genetic components considered to be responsible for NTG development and to discuss the mechanisms through which they are involved in the pathogenesis of NTG.

Impaired cerebrospinal fluid dynamics along the entire optic nerve in normal-tension glaucoma

PURPOSE

To investigate the cerebrospinal fluid (CSF) dynamics along the entire optic nerve (ON) in patients with normal-tension glaucoma (NTG).

METHODS

Retrospective analysis of computed tomographic (CT) cisternographies in Caucasian patients with NTG. Fifty-six patients (99 of 112 eyes) fulfilled the diagnostic criteria of NTG and underwent CT-cisternography. Twelve subjects without NTG (24 eyes) served as controls. Contrast-loaded cerebrospinal fluid (CLCSF) density measurements in Hounsfield units (HU) were performed at four defined regions along the ON and in the basal cistern.

RESULTS

In NTG patients, the mean density CLCSF in the bulbar segment measured 76 ± 49 HU right and 88 ± 74 HU left, in the mid-orbital segment 117 ± 92 HU right and 119 ± 73 HU left, in the intracanalicular ON portion 209 ± 88 HU right and 216 ± 101 HU left, in the intracranial ON portion 290 ± 106 HU right and 286 ± 118 HU left and in the basal cistern 517 ± 213 HU. The distribution of CLCSF along the ON showed a statistically significant reduction in the intraorbital ON segments in NTG patients compared to controls without NTG with the far largest difference within the retrobulbar segment (-150 HU right and -117 HU left; right: p < 0.001, left: p < 0.001).

CONCLUSION

This study demonstrates a gradual reduction in CLCSF towards the retrobulbar segment in NTG, while in controls without NTG, no reduction in CLCSF was measured within the orbital segments. Impaired CSF dynamics along the ON may contribute to the pathophysiology of NTG.

Normal tension glaucoma: review of current understanding and mechanisms of the pathogenesis

Normal tension glaucoma (NTG) is an exception in the "glaucoma family" where the major risk factor, increased intraocular pressure, is missing. If not increased intraocular pressure, then what other causes can then lead to glaucomatous optic disc change and visual field loss in NTG? Several possibilities will be discussed. Among them a higher sensitivity to normal pressure, vascular dysregulation, an abnormally high translaminar pressure gradient and a neurodegenerative process due to impaired cerebrospinal fluid dynamics in the optic nerve sheath compartment. There are many excellent review papers published on normal tension glaucoma (NTG). The aim of this paper is therefore not to add another extensive review on NTG but rather to focus on and to discuss some possible mechanisms that are thought to be involved in the pathophysiology of NTG and to discuss the stronger and weaker aspects of each concept. The fact that several concepts exist suggests that NTG is still not very well understood and that no single mechanism on its own might adequately explain NTG.

Translaminar pressure in Caucasian normal tension glaucoma patients

PURPOSE

The aim of this study was to examine the translaminar pressure difference (TLP) in Caucasian patients with normal tension glaucoma (NTG) and its possible impact onto the pathogenesis of NTG.

METHODS

Retrospective analysis of medical records of patients with open-angle glaucoma (OAG) in the period from 2005 to 2015 from the Ophthalmology Department, Cantonal Hospital Aarau, Switzerland. A total of 67 eyes of 38 patients (mean age 68.6 ± 11.3 years, 21 women and 17 men) fulfilled the diagnostic criteria of progressive NTG and underwent lumbar puncture (LP) during computer-assisted cisternography (CT - cisternography). The intraocular pressure (IOP) and lumbar cerebrospinal fluid pressure (CSF-p) were analysed and the TLP calculated. The TLP was compared with the mean defect (MD) of visual fields. Statistical analysis was performed with the one and two-tailed paired and unpaired t-test and the non-parametric Spearman correlation test.

RESULTS

The mean lumbar opening CSF-p measured 11.6 ± 3.7 mmHg. The mean IOP in the right eye measured 14.7 ± 2.4 mmHg, in the left eye 14.7 ± 2.5 mmHg. The calculated mean TLP was 3.0 ± 4.2 mmHg in the right and 3.3 ± 4.3 mmHg in the left eye. There was no significant correlation between TLP and the MD of visual fields in both eyes.

CONCLUSIONS

This study did not confirm either a lower lumbar CSF-p or increased TLP compared to previous retrospective and prospective studies. As cerebrospinal fluid (CSF) flow is not homogenous throughout all CSF spaces and CSF-p and IOP fluctuate, the current view on TLP needs modifications to improve its validity.

Glaucoma in high myopia and parapapillary delta zone

Purpose

To examine the prevalence of glaucomatous optic neuropathy (GON) in a medium myopic to highly myopic group of patients and its association with parapapillary gamma zone and parapapillary delta zone.

Methods

The retrospective observational hospital-based study included patients who had attended the Tokyo High Myopia Clinics within January 2012 and December 2012 and for whom fundus photographs were available. GON was defined based on the appearance of the optic nerve head on the fundus photographs.

Results

The study included 519 eyes (262 individuals) with a mean age of 62.0±14.3 years (range:13–89 years) and mean axial length of 29.5±2.2 mm (range:23.2–35.3mm). GON was present in 141 (27.2%; 95% confidence intervals (CI): 23.3, 31.0%) eyes. Prevalence of GON increased from 12.2% (1.7, 22.7) in eyes with an axial length of <26.5mm to 28.5% (24.4, 32.5) in eyes with an axial length of ≥26.5mm, to 32.6% (27.9, 37.2) in eyes with an axial length of ≥28mm, to 36.0% (30.5, 41.4) in eyes with an axial length of ≥29mm, and GON prevalence increased to 42.1% (35.5, 48.8) in eyes with an axial length of ≥30mm. In multivariate analysis, higher GON prevalence was associated (Nagelkerke r²: 0.28) with larger parapapillary delta zone diameter (P<0.001; odds ratio (OR):1.86;95%CI:1.33,2.61), longer axial length (P<0.001;OR:1.45;95%CI:1.26,1.67) and older age (P = 0.01;OR:1.03;95%CI:1.01,1.05). If parapapillary delta zone width was replaced by the vertical disc diameter, higher GON prevalence was associated (r²:0.24) with larger vertical optic disc diameter (P = 0.04;OR:1.70;95%CI:1.03,2.81), after adjusting for longer axial length (P<0.001;OR:1.44;95%CI:1.26,1.64) and older age (P<0.001;OR:1.04;95%CI:1.02,1.06).

Conclusions

Axial elongation associated increase in GON prevalence (mean: 28.1% in a medium to highly myopic study population) was associated with parapapillary delta zone as surrogate for an elongated peripapillary scleral flange and with larger optic disc size.

Retinal vascular and structural changes are associated with amyloid burden in the elderly: ophthalmic biomarkers of preclinical Alzheimer's disease

BACKGROUND

Retinal imaging may serve as an alternative approach to monitor brain pathology in Alzheimer's disease (AD). In this study, we investigated the association between retinal vascular and structural changes and cerebral amyloid-β (Aβ) plaque load in an elderly cohort.

METHODS

We studied a total of 101 participants, including 73 elderly subjects (79 ± 5 years, 22 male) with no clinical diagnosis of AD but reporting some subjective memory change and an additional 28 subjects (70 ± 9 years, 16 male) with clinically established AD. Following a complete dilated ocular examination, the amplitude of retinal vascular pulsations and dynamic response, retinal nerve fibre layer thickness and retinal ganglion cell layer (RGCL) thickness were determined in all patients. Systemic blood pressure and carotid-to-femoral pulse wave velocity were measured. The elderly cohort also underwent magnetic resonance imaging and ¹⁸F-florbetaben (FBB)-positron emission tomographic amyloid imaging to measure neocortical Aβ standardised uptake value ratio (SUVR), and this was used to characterise a 'preclinical' group (SUVR >1.4).

RESULTS

The mean FBB neocortical SUVR was 1.35 ± 0.3. The amplitude of retinal venous pulsations correlated negatively with the neocortical Aβ scores (p < 0.001), whereas the amplitude of retinal arterial pulsations correlated positively with neocortical Aβ scores (p < 0.01). RGCL thickness was significantly lower in the clinical AD group (p < 0.05).

CONCLUSIONS

The correlation between retinal vascular changes and Aβ plaque load supports the possibility of a vascular component to AD. Dynamic retinal vascular parameters may provide an additional inexpensive tool to aid in the preclinical assessment of AD.