Ophthalmologic manifestations of carotid occlusive disease

A rare presentation of a common carotid artery occlusion

Background

A common carotid artery occlusion (CCAO) is very rare and the clinical features of CCAO have rarely been described. Since the blood supply of the eye and orbit is derived from the internal carotid artery, a CCAO may present with various ophthalmological symptoms, ranging from incidental findings to complete visual loss but also other neuro-ophthalmological abnormalities.

Case report

A 61-year-old woman presented with acute monocular vision loss and an elevation deficit of the right eye. Fluorescein angiography showed delayed filling of both the retinal and choroidal vasculature, without occlusion/embolisms of the retinal arteries. Vascular imaging showed a right CCAO.

Conclusion

CCAO has a variable presentation. In patients with acute unilateral visual loss a CCAO should be considered, especially when ocular motility deficits are present. Fluorescein angiography examination can aid in the localization and diagnosis of the vascular insult. Urgent referral for a systemic work-up is essential.

Ocular signs of carotid stenosis in ipsi- and contralateral eyes before and after carotid endarterectomy: a prospective study

PURPOSE

We describe hypoperfusion-related and embolic ocular signs of carotid stenosis (CS) before and six months after carotid endarterectomy (CEA) in a CS population.

METHODS

We enrolled prospectively 70 CEA patients (81% male, mean age 69) and 41 non-medicated control subjects (76%, 68), from March 2015 to December 2018, assessing intraocular pressure (IOP), best-corrected visual acuity (BCVA) in logMAR units and performing a bio-microscopy examination.

RESULTS

Main index symptoms included amaurosis fugax (Afx) (29, 41%) and hemispheric TIA (17, 24%), and 17 (24%) were asymptomatic. Of the 70, 17 patients (24%, 95% CI 16-36) showed ocular signs of CS. Of four embolic (Hollenhorst plaques) findings, one small macular plaque disappeared postoperatively. Four had hypoperfusion, that is ocular ischaemic syndrome (OIS), requiring panretinal photocoagulation: one for multiple mid-peripheral haemorrhages, two for iris neovascularization and one for neovascular glaucoma (NVG); only the NVG proved irreversible. Nine (de novo in three) showed mild OIS, that is only few mid-peripheral haemorrhages, ranging pre- /postoperatively in ipsilateral eyes from one to eleven (median two)/ one to two (median one), and in contralateral eyes from three to nine (median five)/ one to six (median three). Pre- and postoperative median BCVA was 0 or better, and mean IOP was normal, except in the NVG patient. Temporary visual impairment from 0 to 0.3 occurred in one eye soon after CEA due to ocular hyperperfusion causing macular oedema.

CONCLUSIONS

Ocular signs of CS are common in CEA patients, ranging from few mid-peripheral haemorrhages to irreversible NVG. Clinicians should be aware of these signs in detecting CS.

Carotid endarterectomy restores decreased vision due to chronic ocular ischemia

BACKGROUND

The therapeutic effect of carotid endarterectomy (CEA) on visual disturbance caused by chronic ocular ischemia due to carotid artery stenosis has not been validated. This prospective observational study aims to investigate whether CEA is associated with an increase in ocular blood flow (OBF) and postoperative visual improvement.

METHODS

In total, 41 patients with carotid artery stenosis treated by CEA between March 2015 and September 2018 were enrolled in this study. OBF was evaluated by laser speckle flowgraphy, which can measure the mean blur ratio (MBR) which is well correlated to the absolute retinal blood flow. Visual acuity was assessed before and after CEA by subjective improvement and objective visual assessment using CSV-1000, an instrument used to test contrast sensitivity.

RESULTS

OBF increased after CEA on the operated side (mean MBR 33.5 vs 38.2, p < 0.001) but not on the non-operated side (mean MBR 37.8 vs 37.5, p = 0.50). After CEA, 23 patients (56.1%) reported subjective visual improvement on the operated side. The mean CSV-1000 score among the patients with increased OBF after CEA (5.44 vs 5.88, p = 0.04) but not among those without increased OBF (5.48 vs 5.95, p = 0.09). The mean CSV-1000 scores increased significantly after CEA in 18 patients with decreased vision and decreased OBF (4.51 vs 5.37, p < 0.001), but not in the 23 patients without those (6.19 vs 6.31, p = 0.6).

CONCLUSION

CEA may successfully reverse visual dysfunction caused by chronic ocular ischemia due to carotid artery stenosis by increasing OBF.

Evaluation of Peripapillary and Subfoveal Choroid Thickness in Asymptomatic Carotid Artery Stenosis

Objective

In this study, it aims to investigate the effect of asymptomatic carotid artery stenosis on peripapillary and subfoveal choroid thickness using enhanced depth imaging optical coherence tomography.

Patients and Methods

While investigating for coronary artery disease, 76 patients with asymptomatic carotid artery stenosis and 35 patients with normal carotid artery (total = 111) were evaluated. Patients according to the degree of stenosis were divided into four categories as non-stenosis (n = 35), mild (n = 26), moderate (n = 27) and severe stenosis (n = 23). Subfoveal and peripapillary choroid thickness, ocular perfusion and intraocular pressures of all patients were measured using a Fourier-domain optical coherence tomography after general ophthalmological examination. In addition, hypertension, hyperlipidemia, and whether there is a relationship between smoking status and choroid thickness was compared.

Results

As the degree of carotid artery stenosis increased, subfoveal and peripapillary choroidal thickness decreased significantly. However, no changes were detected in ocular perfusion and intraocular pressure values (p=0.935, p=0.519). Decrease in peripapillary and subfoveal choroid thickness values was found to be particularly between the group with severe stenosis and the group with control and mild stenosis (p = 0.003, p = 0.001). In addition, as the degree of carotid stenosis increased in patients with hypertension and smoking, peripapillary choroid thickness was found to be thinner (p=0.003).

Conclusion

We believe that the possibility of carotid artery stenosis should be considered in cases with decreased choroid thickness. In addition, we think that even if it is asymptomatic, in cases with severe carotid stenosis, in the presence of choroidal thinning, a chance of surgical intervention should be given to the stenosis.

Window to the circulatory system: Ocular manifestations of cardiovascular diseases

The changes in the cardiovascular system are associated with ocular manifestations, often as a consequence of pathological alteration in the ocular vasculature. The ease of visualization of these retinal changes makes the eye a window to the cardiovascular system. Certain congenital cardiac defects lead to changes in the retinal vascularity due to increased tortuosity and dilatation. In adults, the arterial dissection of internal carotid and vertebral arteries present as amaurosis fugax with or without oculo-sympathetic palsy. The patients with untreated infective endocarditis present with Roth spots, retinitis, embolic retinopathy, or sub-retinal abscesses. Hypoperfusive, hypertensive, or "mixed" retinopathy is a hallmark sign in patients of untreated infective endocarditis. Giant cell arteritis can present with ischemic ocular symptoms that may precipitate in irreversible vision loss. Systemic vascular manifestations such as coronary artery disease may manifest in a wide range of symptoms from amaurosis fugax to vision loss depending upon the size and location of retinal emboli. Rare cardio-oncological pathologies such as myxomas result in vision loss secondary to central retinal artery occlusion. A high clinical suspicion in patients with history of cardiovascular diseases can help in early diagnosis and management of impending, adverse cardiovascular and cerebrovascular events. In this review, we comprehensively discuss the spectrum of cardiac and vascular diseases with ocular manifestations as well as highlight the typical ocular presentations associated with these pathologies.

Changes in Iris Perfusion Following Scleral Buckle Surgery for Rhegmatogenous Retinal Detachment: An Anterior Segment Optical Coherence Tomography Angiography (AS-OCTA) Study

Purpose: To investigate iris vasculature changes following scleral buckling (SB) surgery in eyes with rhegmatogenous retinal detachment (RRD) with anterior-segment (AS) optical coherence tomography angiography (OCTA). Methods: In this prospective study, enrolled subjects were imaged with an SS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc., Dublin, CA, USA). Image acquisition of the iris was obtained using an AS lens and a manual focusing adjustment in the iris using the retina imaging software. The quantitative analysis was performed in eight different iris regions: (i) superior, (ii) supero-temporal, (iii) supero-nasal, (iv) nasal, (v) temporal, (vi) inferior, (vii) infero-temporal, (viii) infero nasal which, were defined as squares with area of 1.5 mm². Results: Fifteen eyes of 15 patients (six females; nine males) were included. Anterior segment optical coherence tomography angiography (AS-OCTA) parameters of the iris were statistically compared at baseline (preoperatively), 1 week, 1 month and 6 months after SB. At post-operative 1 week, perfusion density (PD) showed a significant decrease from 66.8 ± 13.2% to 58.55 ± 12.0% in the iris supero-nasal region (p = 0.016). However, at the 1-month follow-up visit, iris PD was significantly lower in all the analyzed iris regions, apart from the superior one. Conclusions: This study is the first description of AS-OCTA in patients undergoing SB. Our results showed a uniform reduction of the iris vessel network at 1 month after surgery, supporting the clinical use of AS-OCTA to identify early iris perfusion changes as potential predictive biomarkers of vascular disorders.

Significant changes of the choroid in patients with ocular ischemic syndrome and symptomatic carotid artery stenosis

Purpose

To evaluated the changes in choroidal vasculature in patients with ocular ischemic syndrome (OIS) and in the ipsilateral eyes of patients with symptomatic carotid artery stenosis (CAS)

Method

A total of 50 patients (15 patients with OIS, 10 patients with symptomatic CAS, 25 patients of age-and sex-matched control group) were included, and the medical records were retrospectively reviewed. The mean subfoveal choroidal thickness (SFCT) of each eye was measured, and binary images of the choroid were evaluated to compare the mean choroidal area and the luminal area.

Results

The mean SFCT was 170.5±75.3 μm in the eyes with OIS, 154.8±62.9 μm in the ipsilateral eyes with symptomatic CAS, and 277.5±73.2 μm in the right eyes of the control group patients (P<0.001). The mean choroidal area was 494,478.6±181,846.2 μm2 in the eyes with OIS, 453,750.0±196,725.8 μm2 in the ipsilateral eyes with symptomatic CAS, and 720,520±281,319.5 μm2 in the control group eyes (P = 0.036). The mean luminal area was 333,185.7±112,665.9 μm2 in the eyes with OIS, 313,983.3±132,032.1 μm2 in the ipsilateral eyes with symptomatic CAS, and 480,325.0±185,112.6 μm2 in the control group eyes (P = 0.046). The mean SFCT, mean choroidal area, and mean luminal area were significantly smaller in the eyes with OIS (P = 0.017, P = 0.005, and P = 0.004, respectively), and those with symptomatic CAS (P = 0.020, P = 0.016, and P = 0.021, respectively) than in the unaffected contralateral eyes. There were no significant differences between the eyes in the control group (P = 0.984, P = 284, and P = 0.413, respectively).

Conclusion

The mean SFCT, mean choroidal area, and mean luminal area were significantly thinner in the eyes with OIS and the ipsilateral eyes with symptomatic CAS, compared with the control group eyes. The eyes with OIS and those with symptomatic CAS had significantly thinner SFCT, and smaller choroidal area and luminal area than the unaffected contralateral eyes. Choroid may reflect the vascular status of the carotid artery, indicated by choroidal thinning and decreasing choroidal area, especially luminal area.

Functional and morphologic study of retinal hypoperfusion injury induced by bilateral common carotid artery occlusion in rats

Retinal hypoperfusion injury is the pathophysiologic basis of ocular ischemic syndrome (OIS) which often leads to severe visual loss. In this study, we aimed to establish a rat model of retinal chronic hypoperfusion by bilateral common carotid artery occlusion (BCCAO) and observe changes in the retinal function and morphology. We found that model rats showed retinal arteriosclerosis, slight dilated retinal vein, small hemangiomas, hemorrhages, vascular segmental filling, and nonperfused areas after 2 weeks of BCCAO. In the model rats, the retinal circulation time was significantly prolonged by fluorescein fundus angiography (FFA), the latency of a and b waves was delayed and the amplitude was decreased significantly at each time point by electroretinogram (ERG), and the perfusion of the eyes continued to reduced. Morphologic and ultrastructural changes covered that the retinal ganglion cells (RGCs) presented obvious apoptosis and the thickness in the retinal layers were significantly thinner. Collectively, these findings suggested that BCCAO induced retinal hypoperfusion injury in the model rats, thus providing an ideal animal model for the study of OIS.

Subfoveal choroidal thickness and volume in severe internal carotid artery stenosis patients

AIM

To demonstrate the differences of retinal and choroidal structure changes in internal carotid artery (ICA) patients of China by enhanced-depth imaging optical coherence tomography (EDI-OCT).

METHODS

A retrospective review was conducted of 46 patients with a diagnosis of ICA stenosis greater than 65% on only one side (the opposite ICA Stenosis had less than 40% stenosis) from June 2015 through June 2016. All of the patients were combined with amaurosis fugax, but without any abnormality with other ocular examination. Thickness and volume of choroid and retina were manually measured by EDI-OCT. Differences were compared between ICA stenosis eyes and fellow eyes.

RESULTS

There were no significant differences in the retinal thickness, macular retinal nerve fiber layer (mRNFL) thickness, inner thickness, or outer retinal thickness between the ICA Stenosis group and the control group (P=0.834, 0.187, 0.552, and 0.903, respectively). The mean central choroidal thickness of the ICA Stenosis group was significantly lower than that of the control group (239.70±23.76 µm vs 257.46±22.13 µm, P<0.001). The percentage of ICA stenosis was significantly associated with the central choroidal thickness, central retinal thickness, foveal center choroidal volume, and foveal center retinal volume (r=0.854, 0.678, 0.729, and 0.785, respectively; P<0.001). There were no significant differences in the retinal and choroidal volume values in the 4 inner and 4 outer sectors between the two groups.

CONCLUSION

The choroidal thickness in severe ICA stenosis eyes is lower than in fellow eyes. The choroidal thinning may occur before the retinal changes in patients with ocular ischemic syndrome. Evaluations of choroidal thickness may be useful to choose the optimal therapeutic schedule for ICA patients.

Application of Arterial Spin Labelling in Detecting Retinal Ischemia

Purpose

Here, we have tried to quantify the chorioretinal blood perfusion in patients who are clinically identified to be suffering from retinal ischemia using arterial spin labelling (ASL) MRI.

Method

Four participants, diagnosed with retinal ischemia based on their structural OCT and angiography test, were then scanned using anatomical MRI as well as ASL. We optimized MR parameters to maximize resolution and target fixation, blinking, and breathing ques to minimize motion artifacts.

Results

Participants had a maximum of ∼50 mL/100 mL/min of blood perfusion, which is below the normal values of ∼200 mL/100 mL/min. It also appeared that thinning of the choroid contributes more to the measured decreased chorioretinal perfusion, compared to slowed arterial filling time.

Conclusion

Decreased chorioretinal perfusion is a multifactorial event and has been implicated in several posterior eye pathologies. Based on our current results, it seems that ischemia of the eye could be due to anatomy (tissue volume) and/or functionality (arterial flow).

Association between Asymptomatic Unilateral Internal Carotid Artery Stenosis and Electrophysiological Function of the Retina and Optic Nerve

Purpose. This study was designed to assess retinal and optic nerve bioelectrical function in patients with unilateral asymptomatic but hemodynamically significant internal carotid artery stenosis (ICAS). Methods. Forty-two subjects with a diagnosis of unilateral ICAS and 34 controls were analyzed. Full-field electroretinogram (ERG), pattern electroretinogram (PERG), and pattern visual-evoked potentials, as well as optical coherence tomography and ophthalmological examination, were performed. Data analysis included eyes ipsilateral to ICAS (EIS) and eyes contralateral to ICAS (ECS). Results. Intraocular pressure was significantly decreased in EIS and ECS compared to that in the controls. In the macula, both the cube average thickness and cube volume values were significantly reduced both in EIS and ECS compared to those in the controls. Similarly, PERG P50 and N95 wave amplitudes were significantly smaller in EIS and ECS compared to those in the controls. The ERG rod b-wave and rod-cone a-wave amplitudes were decreased, and implicit times were significantly prolonged, whereas the OP wave index was reduced in EIS compared to that in the controls. No differences in IOP, OCT, or ERG and PERG parameters were identified between EIS and ECS. Conclusions. Our study demonstrated that retinal bioelectrical function is negatively affected by ICAS despite the absence of objective clinical signs and symptoms of ocular ischemia.

Peripheral Reticular Pigmentary Degeneration and Choroidal Vascular Insufficiency, Studied by Ultra Wide-Field Fluorescein Angiography

Purpose

To explore the pathogenesis of peripheral reticular pigmentary degeneration (PRPD) and its clinical significance.

Methods

This cross-sectional, observational study (conducted between January 2010 and May 2015) enrolled 441 eyes of 229 subjects, including 35 eyes with PRPD and 406 eyes without PRPD, which was identified by ultra-wide-field fluorescein angiography (UWFA). The distribution and angiographic circulation time of PRPD were assessed by UWFA. The frequencies of systemic and ophthalmologic comorbidities were compared between groups. Univariate and multivariate generalized estimation equation methods were used to determine the risk factors for PRPD.

Results

The patients with PRPD had a mean age of 75.7 ± 8.5 years (range, 59–93 years), whereas the patients without PRPD had a mean age of 60.1 ± 14.9 years (range, 9–92 years). All eyes with PRPD manifested the lesion in the superior nasal periphery with or without circumferential extension. Among those, only 16 eyes (45.7%) in the PRPD group showed distinctive features in the same location on fundus photographs. There was significant choroidal filling delay in the PRPD group when compared with the control group (1.42±1.22 vs. -0.02±1.05 seconds, P < 0.001). Multivariate regression analysis revealed that older age (P < 0.001), stroke (P = 0.018), ischemic optic neuropathy (P < 0.001), and age-related macular degeneration (P = 0.022) were significantly associated with PRPD.

Conclusions

UWFA may enhance the diagnostic sensitivity of PRPD. Choroidal vascular insufficiency with compromised systemic circulation in the elderly was related to the manifestation of PRPD. These results help to better understand the pathophysiology of PRPD. Co-existence of systemic and ophthalmic circulatory disorders should be considered in patients with PRPD.

Bilateral Common Carotid Artery Occlusion in Spontaneously Hypertensive Rats: A Feasible Animal Model for Ocular Ischemic Syndrome

The purpose of this study was to investigate the feasibility of inducing ocular ischemic syndrome in spontaneously hypertensive rats. Hypertensive and normotensive Wistar-Kyoto rats had bilateral occlusion or sham surgery. They were divided into 4 groups: (1) hypertensive-ischemia, (2) hypertensive-sham, (3) normotensive-ischemia, and (4) normotensive-sham. Four months after the operation, the global changes of the eye and pupillary light reflex were assessed. Then each rat was perfused, and randomly one of the bulbuses oculi was prepared as retinal flat mounts for investigation of vascular changes. The opposite eyeball was prepared as a paraffin section for observation of the linear density of retinal ganglion cells and for thickness measurement. One hypertensive-ischemia rat had a cataract in one eye and another rat in the same group had bulbus oculi collapse in one eye. The light reflex disappeared in 13.33% of hypertensive-ischemia rats, and the rest of the hypertensive-ischemia rats and normotensive-ischemia rats had slow reflex. Compared with the respective controls, the peripheral retinal vascular network in hypertensive-ischemia and normotensive-ischemia rats was sparse; linear density of the retinal ganglion cells was significantly reduced; and the retinal thickness was reduced. Compared with normotensive-ischemia rats, the hypertensive-ischemia rats demonstrated more severe changes. After bilateral common carotic artery occlusion, the eyes of hypertensive rats developed various pathological changes similar to those of ocular ischemic syndrome. In conclusion, an animal model for ocular ischemic syndrome can be created by bilateral common carotid artery occlusion in spontaneously hypertensive rats. Anat Rec, 299:806-814, 2016. © 2016 Wiley Periodicals, Inc.

Evaluation of Subfoveal Choroidal Thickness in Internal Carotid Artery Stenosis

Purpose. To evaluate the relationship between internal carotid artery (ICA) stenosis and subfoveal choroidal thickness (SFCT) in the elderly population. Methods. A total of 42 eyes of 21 patients with more than 70% ICA stenosis (Group 1) on one side and less than 70% stenosis (Group 2) on the other side were recruited for this study. ICA stenosis was diagnosed using both the B-mode and Doppler ultrasound. The two groups were compared in terms of the percentage of stenosis, SFCT measurements, intraocular pressure, ocular perfusion pressure, refractive error, and peak systolic velocity. Eyes were examined with the RTVue-100 OCT device by the EDI-OCT technique. Results. The mean age of the patients was 71.9 ± 10.8 years. The mean percentage of ICA stenosis was 74 ± 4.9% in Group 1 and 47.5 ± 7.7% in Group 2. The mean SFCT was 231.9 ± 44.6 μm in Group 1 and 216.2 ± 46.8 μm in Group 2, which was significantly lower (P = 0.028). A statistically significant positive correlation was found between the percentage of internal carotid artery stenosis and SFCT (r = 0896, P = 0.001). Conclusions. Compensatory SFCT increase can be seen in ipsilateral internal carotid artery stenosis greater than 70%.

Ocular ischemic syndrome - a systematic review

Ocular ischemic syndrome is a rare condition, which is caused by ocular hypoperfusion due to stenosis or occlusion of the common or internal carotid arteries. Atherosclerosis is the major cause of changes in the carotid arteries. Ocular ischemic syndrome is manifested as visual loss, orbital pain and, frequently, changes of the visual field, and various anterior and posterior segment signs. Anterior segment signs include iris neovascularization and secondary neovascular glaucoma, iridocyclitis, asymmetric cataract, iris atrophy and sluggish reaction to light. Posterior eye segment changes are the most characteristic, such as narrowed retinal arteries, perifoveal telangiectasias, dilated retinal veins, mid-peripheral retinal hemorrhages, microaneurysms, neovascularization at the optic disk and in the retina, a cherry-red spot, cotton-wool spots, vitreous hemorrhage and normal-tension glaucoma. Differential diagnosis of ocular ischemic syndrome includes diabetic retinopathy and moderate central retinal vein occlusion. Carotid artery imaging and fundus fluorescein angiography help to establish the diagnosis of ocular ischemic syndrome. The treatment can be local, for example, ocular (conservative, laser and surgical) or systemic (conservative and surgical treatment of the carotid artery). Since the condition does not affect the eyes alone, patients with ocular ischemic syndrome should be referred for consultation to the neurologist, vascular surgeon and cardiologist.

Retinal Circulation After Carotid Artery Revascularization

Doubts still exist concerning the mechanisms involved in ocular ischemic syndrome (OIS) and its dependence on carotid disease. We report findings from 14 surgical patients undergoing carotid artery reconstruction for symptomatic cerebrovascular disease. All of them had fluorescein angiography (FA) of the eye ipsilateral to the carotid operation before surgery and 3 months after to provide information regarding retinal circulation time. Before the surgical procedure, the mean circulation time was 29.4 ± 9.4 seconds (CI 95%: 24.5-34.3). After 3 months, a significant (P < .001) decrease in the circulation time was observed: 18.9 ± 8.4 seconds (CI 95%: 14.5-23.4). The present series demonstrates that carotid revascularization surgery improved retinal flow in approximately 80% of the patients.

[Ocular ischemic syndrome]

Ocular ischemic syndrome (OIS) is a group of ocular diseases caused by chronic artery occlusion usually involving the internal carotid artery. Patients suffer from visual loss and pain. OIS is a rare disease which can be confounded with diabetic retinopathy or an older central retinal vein occlusion. The only therapy is to treat the neovascular complications. Due to the high mortality of OIS patients, medical and neurological examinations are mandatory. We discuss the clinical findings and diagnostic and therapeutic options of OIS patients in this paper.

Retinal tissue oxygen tension imaging in the rat

PURPOSE

To report an imaging technique for measurement of oxygen tension (PO2) in retinal tissue and establish its feasibility for measuring retinal PO2 variations in rat eyes by adjusting the fraction of inspired oxygen (FiO2).

METHODS

A narrow laser line was projected at an angle on the retina, and phosphorescence emission was imaged after intravitreal injection of an oxygen-sensitive molecular probe. A frequency-domain approach was used for phosphorescence lifetime measurements. Retinal PO2 maps were computed from phosphorescence lifetime images, and oxygen profiles through the retinal depth were derived in rats in conditions of 10%, 21%, and 50% FiO2.

RESULTS

Retinal PO2 measurements were repeatable, and variations in outer and inner retina PO2 at different locations along the image were not significant (P>or=0.3). Maximum outer retinal PO2 obtained in 10%, 21%, and 50% FiO2 were significantly different (P<0.0001). Maximum outer retinal PO2 correlated with systemic arterial PO2 (R=0.70; P<0.0001). The slope of the outer retina PO2 profile correlated with maximum outer retinal PO2 (R=0.84; P<0.0001). Mean inner retina PO2 correlated with maximum outer retinal PO2 (R=0.88; P<0.0001).

CONCLUSIONS

A technique has been developed for quantitative mapping of retinal tissue oxygen tension with the potential to enable sequential monitoring of retinal oxygenation in health and disease.

Protection against chronic hypoperfusion-induced retinal neurodegeneration by PARP inhibition via activation of PI-3-kinase Akt pathway and suppression of JNK and p38 MAP kinases

Poly(ADP-ribose) polymerase (PARP) activation is considered as a major regulator of cell death in various pathophysiological conditions, however, no direct information is available about its role in chronic hypoperfusion-induced neuronal death. Here, we provide evidence for the protective effect of PARP inhibition on degenerative retinal damage induced by bilateral common carotid artery occlusion (BCCAO), an adequate chronic hypoperfusion murine model. We found that BCCAO in adult male Wistar rats led to severe degeneration of all retinal layers that was attenuated by a carboxaminobenzimidazol-derivative PARP inhibitor (HO3089) administered unilaterally into the vitreous body immediately following carotid occlusion and then 4 times in a 2-week-period. Normal morphological structure of the retina was preserved and the thickness of the retinal layers was increased in HO3089-treated eyes compared to the BCCAO eyes. For Western blot studies, HO3089 was administered immediately after BCCAO and retinas were removed 4 h later. According to Western blot analysis utilizing phosphorylation-specific primary antibodies, besides activating poly-ADP-ribose (PAR) synthesis, BCCAO induced phosphorylation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). HO3089 inhibited PAR synthesis, and decreased the phosphorylation of these proapoptotic MAPKs. In addition, HO3089 treatment induced phosphorylation, that is activation, of the protective Akt/glycogen synthase kinase (GSK)-3beta and extracellular signal-regulated kinase (ERK1/2) signaling pathways. These data indicate that PARP activation has a major role in mediating chronic hypoperfusion-induced neuronal death, and inhibition of the enzyme prevents the pathological changes both in the morphology and the kinase signaling cascades involved. These results identify PARP inhibition as a possible molecular target in the clinical management of chronic hypoperfusion-induced neurodegenerative diseases including ocular ischemic syndrome.

The cognitive and histopathological effects of chronic 4-vessel occlusion in rats depend on the set of vessels occluded and the age of the animals

Continuing previous efforts to develop the 4-vessel occlusion (4-VO) model of chronic cerebral hypoperfusion (CCH), here we evaluated whether permanent, stepwise 4-VO causes both learning deficits, hippocampal neurodegeneration and retinal lesion in young, middle-aged or aged rats. Chronic 4-VO was induced by ligation of different sets of vessels, i.e., the vertebral arteries (VA) plus common carotid arteries (CCA) (4-VO/CCA model) or the VA plus internal carotid arteries (ICA) (4-VO/ICA model) with a 1-week interstage interval. Forty days after the 4-VO, the rats were tested for spatial learning impairment, and then examined for hypoxic/ischemic damage. Young, 4-VO/CCA rats exhibited cognitive impairment, hippocampal neurodegeneration and retinal lesion (p<0.0001-0.05). After 4-VO/ICA, neither young nor middle-aged rats exhibited any learning deficits, hippocampal or retinal damage. In aged rats, chronic 4-VO/ICA caused a mild learning deficit (p<0.05). A significant effect of training was observed for the old, sham-operated rats (p<0.0001-0.001), but not for the aged 4-VO/ICA rats (p>0.05). On average, hippocampal cell density did not change after 4-VO/ICA in aged rats, but 3 of 10 subjects exhibited reduced pyramidal cell counts in all hippocampal subfields. Retinal morphology appeared to be unaffected in the 4-VO/ICA aged rats. These data suggest that the 4-VO/ICA model, but not the 4-VO/CCA model, is a suitable paradigm to study the behavioral outcome of CCH given the preservation of the retina after 4-VO/ICA. Moreover, the age at which 4-VO/ICA occurs seems to be an important factor for determining the behavioral and neuropathological changes.

A method for chorioretinal oxygen tension measurement

PURPOSE

To report an optical imaging system that was developed to measure oxygen tension (pO2) in the chorioretinal vasculatures. The feasibility of the system for the measurement of changes in pO2 separately in the retinal and choroidal vasculatures was established in rat eyes by varying the fraction of inspired oxygen and inhibiting nitric oxide activity.

METHODS

Our optical section phosphorescence imaging system was modified to provide quantitative measurements of pO2 separately in the retinal and choroidal vasculatures. A narrow laser line was projected at an angle on the retina after intravenous injection of an oxygen-sensitive probe (Pd-porphyrin), and phosphorescence emission was imaged. A frequency-domain approach allowed measurements of the phosphorescence lifetime by varying the phase relationship between the modulated excitation laser light and sensitivity of the imaging camera. Chorioretinal pO2 was measured while varying the fraction of inspired oxygen and during intravenous infusion of Nomega-nitro-L-arginine (Nomega-NLA), a nonselective nitric oxide synthase inhibitor.

RESULTS

The systemic arterial pO2 varied according to the fraction of inspired oxygen. The pO2 in the retinal and choroidal vasculatures increased as the fraction of inspired oxygen was increased. Compared with baseline, choroidal pO2 decreased during infusion of Nomega-NLA, whereas the pO2 in the retinal vasculatures remained relatively unchanged. The choroidal pO2 decreased markedly with each incremental increase in Nomega-NLA infusion rate, in the range 1-6 mg/min, and there was no additional change in the choroidal pO2 at Nomega-NLA infusion rates above 6 mg/min.

CONCLUSIONS

An optical method combining pO2 phosphorescence imaging with chorioretinal optical sectioning was established that can potentially be applied for better understanding of retinal and choroidal oxygen dynamics in physiologic and pathologic states.

Chronic bilateral common carotid artery occlusion: a model for ocular ischemic syndrome in the rat

BACKGROUND

Ocular ischemic syndrome is a devastating eye disease caused by severe carotid artery stenosis. The reduction of blood flow produced by bilateral common carotid artery occlusion (BCCAO) of rats for 7 days induces events related to gliosis with no evident histological damage. However, retinal degeneration and cellular death occur after 90 days of BCCAO. Our purpose has been to investigate the effects of BCCAO for 30 days in the retina of adult rats.

METHODS

Adult Wistar rats were submitted to BCCAO or sham surgery. Both direct and consensual pupillary light reflexes were investigated before and after surgery, everyday for the first week and weekly for 30 days. After 1 month, eyes were enucleated and embedded in paraffin. The retinal ganglion cell (RGC) density and thickness of the internal plexiform (IPL), internal nuclear, outer plexiform, and outer nuclear layers were estimated.

RESULTS

Four rats of the BCCAO group (50%) lost the direct pupillary reflex in both eyes, three rats (37%) lost this reflex in one eye, and only one (13%) maintained it in both eyes. RGC density (cells/mm) was diminished in the BCCAO group, and a significant decrease was found in the total retina and IPL thickness; however, no changes were evident in the other layers. BCCAO pupillary-reflex-negative rats presented with a significant decrease in total retinal thickness and retinal ganglion cell density compared with the sham group. Both BCCAO pupillary-reflex-positive) and -negative rats showed a decrease in IPL compared with the sham group.

CONCLUSION

This study demonstrates that BCCAO for 30 days induces functional and morphological damage to the retina with loss of the pupillary reflex and a decrease in IPL thickness and RGC number. We suggest that this protocol might be used as a model for ocular ischemic syndrome in the rat.

Permanent, 3-stage, 4-vessel occlusion as a model of chronic and progressive brain hypoperfusion in rats: a neurohistological and behavioral analysis

Permanent, 3-stage, 4-vessel occlusion (4-VO) was evaluated as a practicable model of progressive, cerebral hypoperfusion in rats, resulting in quantifiable, reproducible, neuronal damage within a time interval shorter than that described in the 2-VO model. The effect of permanent and graded 4-VO on cognition was also evaluated using the newly developed, aversive radial maze. The vertebral arteries (VA) plus the common carotid arteries (CCA) or internal carotid arteries (ICA) were progressively and permanently occluded, following different experimental sequences (CCA--> VA; VA-->CCA-->CCA or VA-->ICA-->ICA) with inter-stage intervals ranging from 1 to 4 weeks. Only two of four groups subjected to 2-stage 4-VO (CCA-->VA) showed modest reduction in the number of normal-appearing CA1 pyramidal cells, despite the significant treatment effect (p < 0.001-0.01 versus sham). A high rate of mortality (63.8%) was associated with 2-stage 4-VO. More pronounced and consistent neuronal damage occurred 8 weeks after 3-stage 4-VO, following the sequence VA --> CCA --> CCA (p < 0.001). One month after this schedule, profound, persistent cognitive impairment was demonstrated in the aversive radial maze (p < 0.01-0.0001). This behavioral effect was not manifested when the ICA, rather than the CCA, were occluded, despite the presence of significant, although less severe, hippocampal lesioning. The mortality rate was significantly reduced when 3-stage 4-VO was used (p < 0.0001). These consistent, histological and behavioral effects, combined with a low mortality rate, suggest that permanent, 3-stage 4-VO may represent a reliable animal model of chronic, progressive, cerebral hypoperfusion.

Perioperative risk factors for posterior ischemic optic neuropathy

BACKGROUND

Infarction of the optic nerve posterior to the lamina cribrosa, called posterior ischemic optic neuropathy (PION), is a condition that can result in profound bilateral blindness. Cases of PION treated at this institution and those described in the literature were analyzed to identify clinical features that profile those individuals at risk of PION in an attempt to identify major contributing factors that could be addressed prophylactically to enable effective prevention.

STUDY DESIGN

Salient clinical features in seven cases of PION diagnosed at the Doheny Eye Institute between 1989 and 1998 are compared with 46 cases of PION reported in the literature.

RESULTS

In the Doheny series there were six men and one woman aged 12 to 66 years (mean, 47 years). Five patients were status-post spine surgery, one was status-post knee surgery, and one had a bleeding stomach ulcer. Vision loss was simultaneously bilateral in six of seven patients (85.7%) and was apparent immediately after surgery. There were no abnormal retinal or choroidal findings including diabetic retinopathy, in any of the patients. Notable contributing factors were blood loss in all seven patients, ranging from 2,000 to 16,000 mL, with a drop in hematocrit of 9.5% to 19% (mean, 14%), and intraoperative systemic hypotension in all patients. Facial edema was a factor in three of six spine surgery patients (50%). Patients reported in the literature had a mean age of 50 years and were also predominantly men (34 of 46, 74%) who underwent spine surgery (30 of 46, 65.2%).

CONCLUSIONS

Middle-aged men undergoing spine surgery with prolonged intraoperative hypotension and postoperative anemia and facial swelling are at risk of developing PION from hypovolemic hypotension. Avoiding or immediately correcting these contributory factors can reduce the incidence of PION.

Retinal and optic nerve degeneration after chronic carotid ligation: time course and role of light exposure

BACKGROUND AND PURPOSE

Carotid artery disease can cause chronic retinal ischemia, resulting in transient or permanent blindness, pupillary reflex dysfunction, and retinal degeneration. This experiment investigated the effects of chronic retinal ischemia in an animal model involving permanent carotid occlusion. The time course of retinal pathology and the role of light in this pathology were examined.

METHODS

Sprague-Dawley rats underwent permanent bilateral occlusion of the common carotid arteries or sham surgery. Half of the animals were postsurgically housed in darkness, and half were housed in a 12-hour light/dark cycle. Animals were killed at 3, 15, and 90 days after surgery. Stereological techniques were used to count the cells of the retinal ganglion cell layer. Thy-1 immunoreactivity was assessed to specifically quantify loss of retinal ganglion cells. The thicknesses of the remaining retinal sublayers were measured. Optic nerve degeneration was quantified with the Gallyas silver staining technique.

RESULTS

Permanent bilateral occlusion of the common carotid arteries resulted in loss of the pupillary reflex to light in 58% of rats. Eyes that lost the reflex showed (1) optic nerve degeneration at 3, 15, and 90 days after surgery; (2) a reduction of retinal ganglion cell layer neurons and Thy-1 immunoreactivity by 15 and 90 days; and (3) a severe loss of photoreceptors by 90 days when postsurgically housed in the light condition only.

CONCLUSIONS

Ischemic damage to the optic nerve caused loss of pupillary reflex and death of retinal ganglion cells in a subset of rats. Subsequently, light toxicity induced death of the photoreceptors.

Ocular ischaemic syndrome

Ocular ischaemic syndrome is a rare condition. It often results in blindness and is linked to serious systemic morbidity. Its presentation is usually subtle and it can be misdiagnosed due to its diverse signs and symptoms. A case of ocular ischaemic syndrome is presented and current diagnostic procedures and treatment described. Recognition by the clinician is important because of the severe ocular and potential systemic sequelae.

Chronic cerebral hypoperfusion: loss of pupillary reflex, visual impairment and retinal neurodegeneration

Adult rats underwent permanent bilateral occlusion of the common carotid arteries (2VO) to determine the effect of chronic cerebral ischemia on vision and retina. They were monitored post-surgically for the presence of the pupillary reflex to light. Some rats were tested for 6 months post-surgically on a radial arm maze task and then tested in another water-escape task which explicitly tested visual function. Another group of rats were tested post-surgically for 3 months on a task which simultaneously assessed visual and tactile discrimination ability. The thicknesses of the retinal sub-layers were then measured for some rats. Fourteen of the 25 rats that underwent 2VO lost the pupillary reflex. This seemed to occur within 5 days. Rats that lost the pupillary reflex but not rats whose reflex was intact, were impaired on all visually guided mazes. Tactile discrimination ability was unaffected. Only rats that lost the pupillary reflex showed reduced thickness of the retinal outer nuclear and plexiform layers, reduced cell density in the retinal ganglion cell layer and astrocytosis and degeneration of the optic tract. We conclude that 2VO can eliminate the pupillary reflex. Photoreceptors and retinal ganglion cells degenerate, but it is unclear if these are the cause(s) or result(s) of the loss of the pupillary reflex. These effects are accompanied by impairment of visually guided behavior. The possibility that visual system damage may also occur in acute ischemia merits further investigation.

Microemboli are not a prerequisite in retinal artery occlusive diseases

PURPOSE

Retinal artery occlusion (RAO) is caused by arterio-arterial or cardiovascular emboli in about 50% of all cases, but the role of non-embolic causes remains unclear.

SUBJECTS AND METHODS

We studied 27 patients with amaurosis fugax (AFX), branch retinal artery occlusion (BRAO), central retinal artery occlusion (CRAO) and anterior ischaemic optic neuropathy (AION). Patients underwent an evaluation of cerebrovascular and cardiovascular risk factors, measurement of haemorheological parameters, and Doppler/duplex sonography including ultrasound detection of cerebral microembolic signals and echocardiography.

RESULTS

Forty-one per cent of the patients had internal carotid atherosclerosis but only one patient had microembolic signals, probably due to a cardiac thrombus. Vascular risk factors, especially hypertension, were present in 82% of the patients correlating with abnormal haemorheological parameters such as increased thrombocyte reactivity.

CONCLUSIONS

Our results indicate that altered haemorheological parameters, especially increased thrombocyte reactivity and vascular risk factors such as arterial hypertension, are non-embolic causes of vascular disease in a significant number of patients with RAO. This should guide diagnostic and therapeutic considerations concerning RAO in cases without proven embolic sources.

The effects of carotid endarterectomy on ocular haemodynamics

PURPOSE

To determine the profile of blood flow velocities and resistive indices in the ocular vessels of patients with atherosclerotic carotid disease and characterise the effect of endarterectomy on these parameters.

METHODS

Following a preliminary study on healthy volunteers, ophthalmic colour Doppler ultrasound examinations were performed on 27 male and 11 female patients with carotid disease. These measurements were compared with central retinal artery perfusion pressures and intraoperative internal carotid artery stump pressures.

RESULTS

Significant changes were seen on the endarterectomised side. The peak systolic velocity in the ophthalmic artery, and resistive indices in the ophthalmic artery, central retinal artery and nasal posterior ciliary artery, rose from pre-operative values. No correlation between colour Doppler ultrasound measurements and intraoperative internal carotid artery stump pressures was present. When compared with ophthalmodynamometry readings, a relationship was noted with maximum velocities in the central retinal vein.

CONCLUSION

Carotid endarterectomy alters the haemodynamics in selected vessels of the ocular circulation as measured by colour Doppler ultrasound, but more work is required to determine the clinical utility of this investigative modality.

The b-wave of the electroretinogram as an index of retinal ischemia

1. The b-wave of the electroretinogram (ERG) is a particularly sensitive index of retinal ischemia. The present paper summarizes the changes in the b-wave observed in five in vivo models of retinal ischemia. 2. Although the amount of reduction in b-wave amplitude during ischemia corresponds to the severity of the insult, the degree of recovery of the b-wave during reperfusion depends on the duration of ischemia. 3. A massive release of glutamate, intracellular overload with calcium and enhanced production of free radicals are suggested to be three major pathophysiological processes that contribute to retinal ischemic damage. The b-wave of the ERG represents a functional measure for potential therapeutic efficacy of drugs interacting with these pathophysiological processes. 4. Several glutamate antagonists, such as MK-801, memantine, flupirtine or GYKI 52466, along with the free radical scavengers vitamin E, lipoate, superoxide dismutase and catalase, all reduce the depression of the b-wave during ischemia or accelerate the recovery of the b-wave during reperfusion or both. The calcium channel antagonists nimodipine and levemopamil exert only a slight beneficial effect on the recovery of the amplitude of the b-wave during reperfusion, provided that the blood pressure is not potently reduced.

Anterior segment ischaemia following segmental scleral buckling

Images

Retinal ischemia induced by occlusion of both common carotid arteries in rats as demonstrated by electroretinography

In 2 models of reduced cerebral blood flow-permanent occlusion of the vertebral arteries plus transient occlusion of the common carotid arteries (4VO) and transient clamping of the common carotid arteries (BCCA)-the acute effects on the electrical function of the retina were monitored by recording the photopic electroretinogram. During both 4VO and BCCA the amplitude of the b-wave was reduced. Within 30 min of reperfusion after 4VO and after BCCA the b-wave had fully recovered. In contrast, the a-wave was not affected by either treatment. The data suggest that occlusion of common carotid arteries leads to retinal ischemia and might represent a useful model of amaurosis fugax.