A "throttle" mechanism in the central retinal vein in the region of the lamina cribrosa

Hypertension, hyperlipidaemia and thrombophilia as the most common risk factors for retinal vein occlusion in patients under 50 years

BACKGROUND AND AIMS

Cardiovascular (CV) diseases are the most common risk factors (RFs) for retinal vein occlusion (RVO) development in general. The aim of this study was to identify the most frequent causes of RVO in patients under 50.

METHODS

We retrospectively evaluated a group of patients with RVO under 50 years. The parameters of interest included age and sex, RVO type, presence of arterial hypertension (HT), hyperlipidaemia (HLD), diabetes mellitus (DM), congenital thrombophilic disorder (TD), obstructive sleep apnoea syndrome (OSAS), thyroid eye disease (TED), use of hormone contraception (HC) or hormone replacement therapy (HRT), glaucoma and other potential RFs. Patients with central RVO (CRVO), hemi-central RVO (HRVO), branch RVO (BRVO), impending CRVO and combined arterial-venous (AV) occlusion were included.

RESULTS

The group consisted of 110 eyes of 103 patients. CV disease was the most common systemic abnormality. 55.3% patients had HT, 17.5% had HLD. TD was the third most frequent RF (12.6%). The cohort also included patients with DM (6.8%), glaucoma (6.8%) and women using HC/HRT (26.2% of female patients). There were isolated cases of RVO due to retinal vasculitis, intense exercise, antiphospholipid syndrome and COVID-19 pneumonia. None of the patients had OSAS, TED or a haemato-oncological disease. The etiology remained unexplained in 20.4% patients. No difference was observed in RF occurrence between patients with CRVO and HRVO and those with BRVO.

CONCLUSION

The most common systemic abnormality in our cohort was CV disease, especially HT and HLD. The risk factors for central, hemi-central and branch RVOs were similar.

Red Blood Cells: A Newly Described Partner in Central Retinal Vein Occlusion Pathophysiology?

Central retinal vein occlusion (CRVO) is a frequent retinal disorder inducing blindness due to the occlusion of the central vein of the retina. The primary cause of the occlusion remains to be identified leading to the lack of treatment. To date, current treatments mainly target the complications of the disease and do not target the primary dysfunctions. CRVO pathophysiology seems to be a multifactorial disorder; several studies did attempt to decipher the cellular and molecular mechanisms underlying the vessel obstruction, but no consensual mechanism has been found. The aim of the current review is to give an overview of CRVO pathophysiology and more precisely the role of the erythroid lineage. The review presents emerging data on red blood cell (RBC) functions besides their role as an oxygen transporter and how disturbance of RBC function could impact the whole vascular system. We also aim to gather new evidence of RBC involvement in CRVO occurrence.

THICKNESSES OF SCLERA AND LAMINA CRIBROSA IN PATIENTS WITH CENTRAL RETINAL VEIN OCCLUSION

PURPOSE

To evaluate thicknesses of sclera and lamina cribrosa (LC) in central retinal vein occlusion (CRVO).

METHOD

Thirty-two patients with CRVO (mean age 62.2 ± 11.6 years, women/men 18/14) and 35 age- and sex-matched healthy volunteers were included into the study. Scleral thickness was measured at scleral spur and at 1 to 3 mm from scleral spur in four quadrants (temporal, nasal, super, and inferior) using anterior segment optical coherence tomography. Lamina cribrosa was measured using optic disk enhanced depth imaging optical coherence tomography.

RESULTS

The sclera was thicker in affected eyes of the CRVO group than healthy subjects at scleral spur in four quadrants (738.7 ± 30.9 µm vs. 702 ± 30.8 µm in temporal, 700.4 ± 19.7 µm vs. 673 ± 13.7 µm in superior, 693 ± 19.3 µm vs. 665.3 ± 24.2 µm in nasal, 810.7 ± 28.9 µm vs. 784.5 ± 23.7 µm in inferior quadrants, respectively; P < 0.05 for all). Lamina cribrosa thickness in affected eyes of the CRVO group was significantly higher than that of healthy subjects (285.2 ± 12.7 µm vs. 266.4 ± 10.7 µm, respectively; P < 0.01). The correlation between scleral thickness and LC thickness was moderate at scleral spur of temporal and superior quadrants of affected eyes (r = 0.510 and r = 0.420, respectively).

CONCLUSION

Thicknesses of sclera and LC are increased in the CRVO, which may play a role in the pathogenesis of the disease.

Retinal vascular occlusions

Acute retinal vascular occlusions are common causes of visual impairment. Although both retinal artery occlusions and retinal vein occlusions are associated with increased age and cardiovascular risk factors, their pathophysiology, systemic implications, and management differ substantially. Acute management of retinal artery occlusions involves a multidisciplinary approach including neurologists with stroke expertise, whereas treatment of retinal vein occlusions is provided by ophthalmologists. Optimisation of systemic risk factors by patients' primary care providers is an important component of the management of these two disorders.

Sustained suppression of VEGF for treatment of retinal/choroidal vascular diseases

Neovascular age-related macular degeneration (NVAMD) is the most prevalent choroidal vascular disease, and diabetic retinopathy (DR) and retinal vein occlusion (RVO) are the most prevalent retinal vascular diseases. In each of these, hypoxia plays a central role by stabilizing hypoxia-inducible factor-1 which increases production of vascular endothelial growth factor (VEGF) and other hypoxia-regulated gene products. High VEGF causes excessive vascular permeability, neovascularization, and in DR and RVO, promotes closure of retinal vessels exacerbating hypoxia and creating a positive feedback loop. Hence once VEGF expression is elevated it tends to remain elevated and drives disease progression. While other hypoxia-regulated gene products also contribute to pathology in these disease processes, it is remarkable how much pathology is reversed by selective inhibition of VEGF. Clinical trials have demonstrated outstanding visual outcomes in patients with NVAMD, DR, or RVO from frequent intraocular injections of VEGF-neutralizing proteins, but for a variety of reasons injection frequency has been substantially less in clinical practice and visual outcomes are disappointing. Herein we discuss the rationale, preclinical, and early clinical results of new approaches that provide sustained suppression of VEGF. These approaches will revolutionize the management of these prevalent retinal/choroidal vascular diseases.

Chorioretinal Anastomosis for Central Retinal Vein Occlusion: A Review of Its Development, Technique, Complications, and Role in Management

Treatments for central retinal vein occlusion (CRVO) have improved dramatically with the advent of intravitreal agents aimed at blocking the effects of the dominant hypoxia-induced upreglulated cytokine, which is vascular endothelial growth factor (VEGF). This cytokine breaks down the capillary endothelial barriers and is a major component of the macular edema in this condition. These treatments although impressive only address some of the sequelae of CRVO and have no effect on the underlying cause which is an obstruction to venous outflow leading to retinal blood flow stagnation and an elevation of the retinal central venous pressure (CVP). The creation of a laser-induced chorioretinal anastomosis (L-CRA) between the obstructed high pressure retinal venous circulation and the unobstructed low pressure choroidal venous circulation is a means addressing the causal pathology. The L-CRA will help lower the elevated CVP, which has been up until now an unaddressed component of the macular edema in this condition.This article reviews the preclinical and clinical development of the L-CRA and the results of the studies into its effect on the natural history of CRVO. It now can be used in combination with existing anti-VEGF treatments with the intravitreal agents addressing the component of the CRVO-induced macular edema due to the cytokine dysregulation, and the L-CRA addressing the component due to the elevated CVP and retinal venous stagnation. Improvements in laser technology have led to higher success rates in L-CRA creation and potential complications are now minimized and better controlled. The combination of L-CRA with intravitreal anti-VEGF agents offers the potential of a permanent cure with a significant reduction in the burden of therapy and improved visual outcomes in this condition.

The short-term effects of intravitreal aflibercept injections and dexamethasone implant on ocular hemodynamics in retinal vein occlusions

Purpose

To determine the early effects of intravitreal anti-VEGF and dexamethasone application on blood flow velocities in patients with retinal vein occlusions.

Methods

The ophthalmic (OA) and the central retinal arteries (CRAs) of the affected and unaffected eyes of 21 patients with central retinal vein occlusion (CRVO), and 26 patients with branch retinal vein occlusion (BRVO) were investigated by Color Doppler imaging (CDI). Peak systolic volume (PSV), end diastolic volume (EDV), and average blood velocity (Vmean) of the CRA and OA were measured and resistive indexes (RI) were calculated at pre-injection and the 1st week and 1st month post-injection.

Results

There was no statistically significant difference between the OA values for affected and unaffected eyes in the CRVO group before treatment. The CRA, EDV, and Vmean values were significantly lower in affected eyes. Blood flow velocities of both CRA and OA were not significantly different than in the fellow unaffected eyes in the BRVO group. The differences between PSV, EDV, and Vmean measurements of OA and CRA at different times pre- and post-injection in response to anti-VEGF and dexamethasone treatment in the CRVO group were significant; but there was no difference in RI value. OA blood flow velocity measurements were not statistically different post-injection in the BRVO group; however, the values of PSV and EDV of CRA decreased post-injection.

Conclusion

Intravitreal anti-VEGF and dexamethasone implant may induce retinal arteriolar vasoconstriction in patients with retinal vein occlusion.

Evaluation of lamina cribrosa thickness in patients diagnosed with central retinal vein occlusion

PURPOSE

To evaluate the thickness of lamina cribrosa (LC) in both eyes of patients with unilateral central retinal vein occlusion (CRVO) and to compare with eyes of age-matched healthy control subjects.

METHODS

This prospective case-control study included a total of 38 patients with unilateral CRVO and 42 healthy control subjects. The LC thickness was measured at the center of the optic disc using an enhanced depth imaging with the spectral domain optical coherence tomography in both eyes of patients with unilateral CRVO and eyes of healthy control subjects. The LC thickness of CRVO patients was evaluated one month after dexamethasone intravitreal implant (Ozurdex) injection.

RESULTS

The mean LC thickness in affected eyes of patients with CRVO was significantly thinner than that of the healthy eyes (204.4 ± 8.8 and 228.0 ± 7.1 μm, p < 0.001, respectively). Also, the unaffected fellow eyes had significantly thinner LC compared with eyes of healthy subjects (205.3 ± 9.3 and 228.0 ± 7.1 μm, p < 0.001, respectively). There was no statistically significant difference in the thickness of LC between the affected and unaffected fellow eyes (p = 0.669).

CONCLUSIONS

The LC thickness in both eyes of CRVO patients was thinner than that of the healthy eyes. This finding suggests that thin LC may contribute to the development of CRVO as an ocular risk factor in addition to systemic factors.

Venous thrombosis in unusual sites: A practical review for the hematologist

Thrombosis of unusual venous sites encompasses a large part of consultative hematology and is encountered routinely by practicing hematologists. Contrary to the more commonly encountered lower extremity venous thrombosis and common cardiovascular disorders, the various thromboses outlined in this review have unique presentations, pathophysiology, workup, and treatments that all hematologists should be aware of. This review attempts to outline the most up to date literature on cerebral, retinal, upper extremity, hepatic, portal, splenic, mesenteric, and renal vein thrombosis, focusing on the incidence, pathophysiology, provoking factors, and current recommended treatments for each type of unusual thrombosis to provide a useful and practical review for the hematologist.

Shifts in renin-angiotensin system components, angiogenesis, and oxidative stress-related protein expression in the lamina cribrosa region of streptozotocin-induced diabetic mice

PURPOSE

This study aimed to analyse shifts in renin-angiotensin system (RAS) components, angiogenesis, and oxidative stress-related protein expression in the lamina cribrosa (LC) region in streptozotocin (STZ)-induced diabetic mice.

METHODS

Six months after diabetes induction, the retinal vessels of male C57BL/6 J mice were observed by colour photography, fundus fluorescein angiography (FFA), and immunofluorescent staining following incubation with CD31. Immunofluorescence for glial fibrillary acidic protein (GFAP), alpha-smooth muscle actin (α-SMA),and NG2 was also performed. Angiotensin-converting enzyme 1 (ACE1), angiotensin II type I receptor (AT1R), renin, hypoxia-inducible factor 1-alpha (HIF-1α), vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor 2 (VEGFR2), and haeme oxygenase 1 (HO-1) expression levels were confirmed by immunohistochemical and western blotting analyses.

RESULTS

Compared with control mice, diabetic mice had significantly higher blood glucose concentrations (p < 0.001) and significantly lower body weights (p < 0.001). Colour photography and FFA did not reveal any vessel abnormalities in the diabetic mice; however, immunostaining of whole-mount retinas revealed an increased number of retinal vessels. Furthermore, histopathological staining showed significant reduction in the whole retinal thickness. GFAP expression was slightly higher, whereas fewer NG2⁺ pericytes were observed in diabetic mice than in control mice. ACE1, AT1R, renin, HIF-1α, VEGF, VEGFR2, and HO-1 expression were up-regulated in the LC of the STZ-induced diabetic mice.

CONCLUSIONS

Collectively, ACE 1, AT1R, HIF-1α, VEGF, VEGFR2, and HO-1 activation in the LC region in diabetic mice may be involved in diabetes via the RAS and induction of angiogenesis and oxidative stress.

Optic nerve head in central retinal vein occlusion by spectral-domain OCT

PURPOSE

To evaluate the morphology of optic nerve head by spectral-domain optical coherence tomography (SD-OCT) in patients with unilateral central retinal vein occlusion (CRVO).

METHODS

In 39 consecutive patients with unilateral CRVO and 39 healthy controls, morphologic parameters of optic nerve head were assessed in both eyes by Spectralis SD-OCT using a custom radial B-scan pattern. The length of Bruch membrane opening (BMO) was measured in OCT scans, and optic disc diameters (DD) were assessed in infrared fundus photographs. Axial length was determined by IOLMaster.

RESULTS

The BMO length was measured in all eyes with CRVO, while DD was not assessed in 9 eyes (27.3%) that had undefined disc margins. Compared to healthy controls (mean BMO length 1,511 ± 79 μm, mean disc diameter 1,521 ± 77 μm), in eyes with CRVO with defined disc margins (n = 28 [71.8%]), no significant difference was found in BMO length and DD (1,473 ± 118 μm and 1,516 ± 104 μm, respectively). Eyes with CRVO with undefined disc margins had lower BMO length (1,289 ± 61 μm [-14.7%], p = 0.001); also, in fellow eyes, these patients had lower BMO length and DD. In all groups, no significant difference was seen between BMO and DD. A correlation was found between axial length and BMO length and disc diameter (both p<0.001).

CONCLUSIONS

Most of the eyes with CRVO had normal optic disc diameter, but about 25% of patients with CRVO have reduced optic disc dimensions.

Central retinal vein occlusion in a young adult Case report

PURPOSE

To report the case of a 48-year-old man with unilateral central retinal vein occlusion.

METHODS

The clinical, hematologic and hypercoagulability evaluations of the patient were thoroughly and specifically carried out.

RESULTS

The central retinal vein occlusion was of nonischemic type and was associated with polyglobulia, hyperleukocytosis, hypercholesterolemia, multiple dental foci, and pulmonary sequelae of tuberculosis.

CONCLUSIONS

When a patient less than 50 years of age experiences central retinal vein occlusion, other mechanisms, such as the hyperviscosity syndrome or the inflammatory condition (inflammation of the central retinal vein) should be specifically considered and accounted for.

Seeing through thick and through thin: Retinal manifestations of thrombophilic and hyperviscosity syndromes

The presence of retinal vasculopathy in the absence of typical predisposing factors should suggest a possible underlying hematologic abnormality. In such cases, a systemic investigation may reveal a potentially fatal hypercoagulability or hyperviscosity syndrome. Retinal vein occlusion is the most commonly encountered ophthalmic finding in such syndromes; however, abnormalities of the arterial system, the choroid, and the macula are also possible. Visual symptoms may be the only manifestation of the underlying process, making timely diagnosis by the ophthalmologist critical for both treatment and thrombotic prophylaxis. Moreover, as newer ophthalmic diagnostic technologies arise, there is an increasingly important role for eye physicians in the management of such syndromes.

Intense exercise causing central retinal vein occlusion in a young patient: case report and review of the literature

We report a 19-year-old patient who developed a central retinal vein occlusion (CRVO) with significant macular edema and visual impairment following intense exercise and dehydration. The patient was treated with 3 intravitreal bevacizumab injections with complete resolution. A review of the literature on the cause and treatment for CRVO in young patients was performed, focusing on the role of intense exercise and dehydration as a rare pathogenesis mechanism of CRVO.

Higher optic nerve sheath diameters are associated with lower ocular blood flow velocities in glaucoma patients

PURPOSE

To investigate the relationship between optic nerve sheath diameter (ONSD) and retrobulbar blood flow velocities, as measured by color Doppler imaging (CDI) in glaucoma patients.

METHODS

We performed a prospective, randomized, observer-masked study involving a total of 197 subjects. Once enrolled, they were divided by three groups: healthy controls (n = 51), normal-tension glaucoma patients (NTG, n = 58), and primary, open-angle glaucoma patients (POAG, n = 88). All subjects underwent a general ophthalmological examination, an ultrasound-based assessment of the ONSD, and a hemodynamic study of the retrobulbar vascularization using CDI. Non-parametric tests, chi-square contingency tables, and the Deming correlations were used to explore differences and correlations between variables in the diagnostic groups.

RESULTS

ONSD was not different between experimental groups (p = 0.28). ONSD correlated positively with the pulsatility index of the ophthalmic artery in healthy individuals (p = 0.007), but not in glaucoma patients (NTG: p = 0.41; POAG: p = 0.22). In NTG patients, higher ONSD values were associated with lower end-diastolic and mean flow velocities in the short ciliary arteries (p = 0.005 in both correlations). No such correlation was found in healthy nor POAG groups (p range between 0.15 to 0.96). ONSD was not associated with any CDI-related variable of the central retinal artery in any cohort. Venous outflow velocities were not associated with ONSD in any of the three groups.

CONCLUSIONS

ONSD is negatively correlated with retrobulbar blood flow velocities in glaucoma patients, but not in healthy controls.

Measurement of PO2 during vitrectomy for central retinal vein occlusion, a pilot study

INTRODUCTION

In this pilot study the effects of vitrectomy on PO(2) in the vitreous cavity in CRVO were investigated.

STUDY DESIGN

Prospective, controlled, interventional study.

METHOD

Six patients with ischaemic CRVO in one eye (undergoing vitrectomy for radial optic neurotomy, RON) and six with either macula hole or membrane were included. An oxygen probe was inserted before removal of the vitreous (pre-vitrectomy) and after removal of the vitreous (post-vitrectomy). In the patients with CRVO, measurements were taken before RON was performed. Oxygenation recordings (PO(2)) were taken in the mid-vitreous cavity and the preretinal vitreous.

RESULTS

Mean age was 65 years. In controls, pre-vitrectomy, the mean PO(2) adjacent to the retina (15.0 mmHg S.D.5.7) was significantly less than mid-cavity (33.7 mmHg S.D.12.8). Similarly in CRVO, the pre-vitrectomy pre-retinal PO(2) (8.1 mmHg S.D. 3.5), was significantly less than mid-cavity (19.8 mmHg S.D.7.3). The mean PO(2) was significantly less in the eyes with CRVO than in control eyes. Post-vitrectomy, the PO(2) was significantly greater than pre-vitrectomy at both recording sites in the controls mid-cavity (61.5 mmHg S.D.13.9) and pre-retinal (75.8 mmHg S.D. 9.1), and CRVO eyes mid-cavity (53.7 mmHg S.D. 17.9) and pre-retinal (59.8 mmHg S.D. 15.8).

CONCLUSION

PO(2) is reduced in the vitreous cavity in CRVO. Vitrectomy may be a method of increasing oxygen availability to the retina.