Central Retinal Artery: A Human Fetal Cadaveric Study with Histological Correlation.

The optic nerve is the second cranial nerve. It is supplied by the central retinal artery. It is said that this artery starts getting incorporated within the optic nerve at around the sixth week of gestation, and by the ninth week it is entirely inside the optic nerve. However, the point of incorporation lies in the intraorbital course of the optic nerve. The present study aimed at identifying the location of the central retinal artery inside the optic nerve, i.e. the peripheral or central position. Human fetuses of second and third trimester were dissected to expose the optic nerve. Morphometric measurements were taken and sectioned in 3 regions. These transverse sections were subjected to histological procedures. The results showed that the central retinal artery, at its entry into the optic nerve, was peripheral and inferior in 3 of 25 optic nerves and peripheral and lateral in the remaining optic nerves. However, the arteries were all centrally placed, close to the posterior pole of the eyeball. These findings are important for the ophthalmologist in identifying certain congenital anomalies of the eyeball in neonates.

Assessment of optic nerve vascularity in healthy eyes using superb microvascular imaging: a preliminary study.

BACKGROUND: Changes in optic nerve vascularity are observed in many diseases. Superb microvascular imaging (SMI) has the potential to become the method of choice for detecting microvasculature in the optic nerves. PURPOSE: To evaluate optic nerve vascularity in healthy individuals through power Doppler sonography (PDUS) and SMI. MATERIAL AND METHODS: Twenty-seven healthy patients with 54 eyes were prospectively evaluated. The duration of the examination for optic nerve vascularity lasted until the posterior ciliary artery blood supply was observed in PDUS and SMI. The visibility of vascularity, as well as the ratio of the vascular structures to the optic nerves (vascular index [VI]), was evaluated. RESULTS: Fifty-four eyes were evaluated from a total of 27 patients (mean age = 49.0 ± 19.42 years). The VI value for the right optic nerve was 29.58 ± 4.00 while for the left optic nerve, it was 31.21 ± 3.52. Vascularity was clearly observed in both eyes (n = 54) in all 27 cases in the evaluation performed with the SMI technique. However, with the power Doppler examination, vascular flow was not observed in 14 right eyes and in 10 left eyes within the specified timeframe. CONCLUSION: The results indicate that imaging of vascular structures can be done faster and better with SMI than PDUS examination. The normal VI values may provide important information about the blood supply of the optic nerve, which is of relevance in orbital pathologies and many systemic conditions.

Microanatomic Study of the Optic Canal.

BACKGROUND: The continuous development of microsurgical techniques to treat lesions in and around the optic canal (OC) emphasizes the need for an accurate understanding of the microanatomy of the region. METHODS: Forty anatomic specimens were studied, with emphasis on the OC. The sphenoid bone and related structures were decalcified, added to animal gelatin, cut into 1-mm thick slices, and observed through a surgical microscope. The OC was considered the course that contained exclusively the optic nerve (ON) and ophthalmic artery. RESULTS: The mean distance between the medial walls of the OC was 12.2 mm, and the OC had an average length of 12.06 mm. The OC has a horizontal oval shape in the proximal (internal) segment; a round shape in the middle segment; and a vertical oval shape in the distal (external) segment at the orbital cavity. In the middle segment of the OC, the thickest wall of the OC was the lateral (average: 0.68 mm), while the medial, inferior, and superior wall measures had averages of 0.75, 0.40, and 0.39 mm, respectively. The lateral wall of the sphenoid sinus is located under the OC, and the inferior wall of the OC separates both structures. The ophthalmic artery inside the OC was always located under the ON, between the dural sheaths, and had an average diameter of 1.03 mm. CONCLUSIONS: The neurovascular structures within the OC vary in size and shape. The anatomic knowledge of the OC and its variations allows better surgical results and minimizes the surgical morbidity.

A Unique Radiologic Case of Optic Nerve Infarction in a Patient With Mucormycosis.

ABSTRACT: This is a rare presentation of a unilateral optic nerve infarction of the left eye caused by mucormycosis in a 51-year-old man with poorly controlled Type 2 diabetes. Diffusion-weighted MRI of the orbit demonstrated extensive infarction of the left optic nerve with ipsilateral cavernous sinus thrombosis and periorbital adnexal inflammation. Left orbital exenteration and sinus debridement were performed, and mucormycosis involving the optic nerve sheath was confirmed on histopathology.

A neurosurgical assessment of the blood supply in the optochiasmatic system: a cadaveric-anatomic study.

The chiasmal and subchiasmal surfaces are of critical importance in connection with the performance of surgical procedures owing to the critical blood supply to these areas. Recently, the perforating arteries providing the blood to the optic nerves and chiasm have gained attention as they significantly affect the morbidity from surgical approaches. Intraoperative preservation of these perforating arteries is considered critical to prevent further visual loss. Thirty autopsy specimens, including the optic apparatus, were examined for their perforating arteries feeding the optic chiasm and optic nerves. The optic nerves and chiasmal surfaces were divided into four zones based on the presence and numbers of perforating arteries as anterior superior-posterior superior surfaces and anterior inferior-posterior inferior surfaces. The superior surface of the optic chiasm was supplied by the A1 segments of the bilateral anterior cerebral arteries and by the perforating arteries originating from the anterior communicating artery. On the other hand, the inferior surface of the optic chiasm was fed by the bilateral posterior communicating arteries and by the supraclinoidal segments of the bilateral carotid arteries. We demonstrated the anatomical involvement of a large number of nourishing arteries in feeding the optic apparatus related to the perforating arteries by classifying them into zones based on the surgical approaches, which has been rarely reported in the literature.

The entry point of the central retinal artery into the outer meningeal sheath of the optic nerve.

INTRODUCTION: The entry point of the central retinal artery (CRA) into the outer meningeal sheath of the optic nerve posterior to the globe has been studied and debated for more than one hundred years. The authors have supervised an orbital anatomy course for more than two decades. This article summarizes previous studies of the CRA and presents the results of dissections of 67 orbits. MATERIALS AND METHODS: Heads were hemisected prior to dissection at the Vagelos College of Physicians and Surgeons of Columbia University. The authors measured the entry point of the CRA with a caliper and noted the meridional orientation of the CRA. RESULTS: The mean entry point was 10.65 mm posterior to the globe, with a range of 5 to 18 mm. Most commonly, the CRA entered the sheath in the inferior meridian, but some entered slightly inferomedially or inferolaterally. CONCLUSIONS: The entry point of the CRA into the sheath of the optic nerve is variable, and without detailed angiography the clinician cannot know the course of the CRA prior to performing invasive intraorbital procedures. Knowledge of common variations in CRA entry into the outer meningeal sheath of the optic nerve should help to minimize injury during surgery.

Progression in Open-Angle Glaucoma with Myopic Disc and Blood Flow in the Optic Nerve Head and Peripapillary Chorioretinal Atrophy Zone.

PURPOSE: To investigate the effect of blood flow in the temporal optic nerve head (ONH) and peripapillary chorioretinal atrophy (PPA) zone on central visual field (VF) defects and progression in eyes with open-angle glaucoma (OAG) and myopic disc. DESIGN: Retrospective longitudinal medical chart review. PARTICIPANTS: This study comprised 366 eyes of 245 OAG patients with myopic disc, followed for at least 2 years with at least 5 reliable VF tests. OCT and laser speckle flowgraphy (LSFG) were performed at baseline. METHODS: We analyzed the relationship between temporal ONH-tissue mean blur rate (MBR), temporal PPA-tissue MBR, total deviation (TD)-central, and TD-central slope with a linear mixed-effects model. Additionally, we investigated background factors influencing temporal PPA-tissue MBR. Main outcome measures were basic ophthalmic and systemic variables, baseline ONH-tissue MBR, baseline PPA-tissue MBR, baseline TD, and TD slope. RESULTS: Lower temporal ONH-tissue MBR was associated with both worse TD-central and faster TD-central slope (ß = 0.30, P < 0.001; ß = 0.18, P = 0.001, respectively). However, lower temporal PPA-tissue MBR was only associated with faster TD-central slope (ß = 0.15, P = 0.005). Lower ONH-tissue MBR and lower PPA-tissue MBR were significant independent contributors to worse TD-central slope, after adjusting for potential confounding factors (ß = 0.12 to 0.15, P < 0.05). The multivariate analysis showed that lower pulse rate, larger temporal PPA area, and lower circumpapillary retinal nerve fiber layer thickness were associated with lower PPA-tissue MBR (P < 0.05). CONCLUSIONS: Measurement of systemic variables and LSFG analysis might help clinicians to predict central VF defect severity and progression in OAG eyes with myopic disc.

Correlation between blood flow on optic nerve head and structural and functional changes in eyes with glaucoma.

The purpose of this study was to determine the significance of the correlations between blood flow on the optic nerve head (ONH) using the mean blur rate (MBR) determined by laser speckle flowgraphy and the visual field loss determined by perimetry and the structural alterations by optical coherence tomography in eyes solely with open-angle glaucoma. There were significant differences in the circumpapillary retinal nerve fiber layer thickness (cpRNFLT), and the MBR-tissue, at the different stages of glaucoma (ANOVA, P < 0.001). Univariate linear regression analyses indicated that the mean deviations (MD) were significantly correlated with both the MBR-tissue (r = 0.661, P < 0.001) and the cpRNFLT (r = 0.279, P = 0.005). Logistic regression analyses showed that the MD was significantly correlated with the MBR-tissue (P < 0.001) and the cpRNFLT (P < 0.001). The MBR-tissue was found to be the factor that can best predict the MD based on the Akaike information criteria (P < 0.001). Stepwise multiple logistic regression analyses showed that the MBR-tissue and the cpRNFLT were both risk factors that were significantly associated with the MD (Odds ratio;1.25 and 1.07, P < 0.001 and P < 0.001, respectively). These results indicate that the MBR-tissue was as important as the structural values in diagnosing and determining the prognosis of glaucoma.

The Superior Hypophyseal Arteries: Anatomical Study with an Endoscopic Endonasal Perspective.

BACKGROUND: The use of high-definition endoscopes in extended transsphenoidal approaches to the suprasellar area has significantly improved visualization of its vascularization. OBJECTIVE: To systematically examine the superior hypophyseal arteries (SHAs) anatomy from an endonasal endoscopic perspective. METHODS: The endoscopic endonasal transsphenoidal trans-tuberculum approach was performed in 19 adult, fresh and latex injected specimens. Dissections recordings were reviewed to analyze SHAs type, number, and branches, as well as internal carotid arteries (ICA) branches that vascularized optic nerves and chiasm. RESULTS: Identification of SHAs was possible in all specimens (37/38 sides). The number of SHAs varied from 1 to 3 per side (mean: 1.7). The anterior superior hypophyseal artery was visible in almost all cases (35/37 sides) and originated at the level of the carotid cave in 18/35 specimens; number of branches ranged from 1 to 6 (mean: 3.5), directed to the optic nerve (86%), chiasm (57%), infundibulum (86%), and/or parallel to the pituitary stalk (74%). The 4 main branches and patterns, originally described by McConnell in 1953, were confirmed. The posterior superior hypophyseal artery was evident in 28/37 sides with number of branches ranging from 0 to 4 (mean: 2.1), directed to the optic chiasm (50%), optic tract (32%), infundibulum (79%), and/or pituitary stalk (36%). The surgical implications of this study, together with anatomical and clinical videos, are also briefly discussed. CONCLUSION: SHAs constitute a complex of anterior and posterior branches that stem from the medial ICA with different patterns, vascularizing the optic apparatus and pituitary stalk.

Peripapillary and parafoveal vascular network assessment by optical coherence tomography angiography in aquaporin-4 antibody-positive neuromyelitis optica spectrum disorders.

BACKGROUND/AIMS: Current understanding of the alterations in the retinal vascular network in neuromyelitis optica spectrum disorders (NMOSDs) is limited. We aim to assess the peripapillary and parafoveal vessel density in aquaporin-4 antibody-positive NMOSD patients by optical coherence tomography (OCT) angiography. METHODS: A total of 55 aquaporin-4 antibody-positive NMOSD patients with or without a history of optic neuritis (ON) and 33 healthy controls underwent spectral domain OCT and OCT angiography. Clinical histories, Expanded Disability Status Scale score, visual functional system score (VFSS) and disease duration were collected. RESULTS: Peripapillary and parafoveal vessel density was significantly decreased in NMOSD eyes with or without a history of ON. The decrease in retinal vessel density could occur before ON and retinal nerve fibre layer (RNFL) atrophy. Peripapillary vessel density correlated well with the spectral domain OCT measurements and VFSS in NMOSD eyes with a history of ON. CONCLUSION: Subclinical primary retinal vasculopathy may occur in NMOSD prior to ON and RNFL atrophy. Peripapillary vessel density might be a sensitive predictor of visual outcomes in NMOSD patients with ON.

Evaluation of Ocular Perfusion in Alzheimer's Disease Using Optical Coherence Tomography Angiography.

BACKGROUND: There is increasing evidence for the involvement of cerebrovascular factors in Alzheimer's disease (AD). OBJECTIVE: To evaluate retinal and optic nerve head perfusion in patients with AD using optical coherence tomography angiography (OCTA), and to analyze the correlations of quantitative OCTA metrics with AD pathology and vascular cerebral lesions in AD patients. METHODS: 36 eyes of 36 patients with AD (study group) and 38 eyes of 38 healthy subjects (control group) were prospectively included in this study. OCTA was performed using RTVue XR Avanti with AngioVue. In addition, patients underwent a detailed ophthalmological and neurological examination including Mini-Mental State Examination, cerebral magnetic resonance imaging, and amyloid-ß (Aß) and tau levels in the cerebrospinal fluid (CSF). RESULTS: The flow density in the superficial retinal OCT angiogram of the macula in the study group was significantly lower compared to the control group (p = 0.001). There was a significant correlation between the flow density in the superficial retinal OCT angiogram of the macula, as measured using OCTA, and the Fazekas scale (Spearman's correlation coefficient = -0.520; p = 0.003). There was no significant correlation between the Aß or tau levels in the CSF and the flow density data. CONCLUSION: Patients with AD showed a reduced flow density in the radial peripapillary capillaries layer and in the superficial retinal OCT angiogram when compared with healthy controls. The reduced retinal flow density measured using OCTA is not specifically associated with AD pathology but is associated with the vascular cerebral lesions in AD.

Evaluation of flicker induced hyperemia in the retina and optic nerve head measured by Laser Speckle Flowgraphy.

PURPOSE: The coupling between neural activity and blood flow is a physiological key principle of ocular blood flow regulation. The current study was performed to investigate whether Laser speckle flowgraphy (LSFG), a commercially available technique for measuring blood flow, is capable to assess flicker-induced haemodynamic changes in the retinal and optic nerve head (ONH) circulation. METHODS: Twenty healthy subjects were included in this cross sectional study. A commercial LSFG instrument was used to measure blood flow at the ONH as well as in retinal vessels before and during stimulation with flickering light. Mean blur rate (MBR), a measure of relative blood flow velocity, was obtained for the ONH and relative flow volume (RFV) a measure of relative blood flow of the respective retinal vessels. RESULTS: Stimulation with flicker light increased ONH MBR by +17.5%±6.6% (p<0.01). In retinal arteries, flicker stimulation led an increase of +23.8±10.0% (p<0.05) in total RFV. For retinal veins, an increase of +23.1%±11.0 (p<0.05) in total RFV was observed during stimulation. A higher response was observed in nasal RFV compared to temporal RFV in retinal arteries (nasal: +28.9%±20.0%; temporal: +20.4%±17.6%, p<0.05) and veins (nasal: +28.3%±19.6%; temporal +17.8%±18.9%, p<0.05). CONCLUSION: As shown previously with other techniques, flicker stimulation leads to an increase in retinal and optic nerve head blood flow. Our results indicate that LSFG is an appropriate method for the quantification of retinal and ONH blood flow during visual stimulation and may be used as a non-invasive, easy to use tool to assess neuro-vascular coupling in humans.

Cilioretinal artery occlusion and anterior ischemic optic neuropathy as the initial presentation in a child female carrier of Fabry disease.

PURPOSE: To report the youngest female carrier of Fabry disease, complicated by cilioretinal artery occlusion and anterior ischemic optic neuropathy (AION). METHODS: Case report. RESULTS: An 11-year-old girl was referred to our clinic with painless, acute loss of vision in her right eye. Posterior segment examination and fluorescein angiography revealed cilioretinal artery occlusion and AION. Systemic evaluations were unremarkable, except for a low blood α-galactosidase A enzyme level of 242.27 pmol/spot*20 h (reference range: 450-2000 pmol/spot*20 h). The patient was diagnosed with female carrier of Fabry disease. CONCLUSION: Retinal vascular occlusions are rare in childhood, and Fabry disease may present with retinal vascular occlusion. Ophthalmological examinations may be contributing for early detection of the disease. To the best of our knowledge, this is the first report of a child female carrier of Fabry disease, complicated by cilioretinal artery occlusion and AION.

Possible role of miR-204 in optic nerve injury through the regulation of GAP-43.

Optic nerve injury is a common disease. The present study aimed to examine the possible role of microRNA­204 (miR­204) in optic nerve injury through the regulation of growth­associated protein-43 (GAP­43). Initially, optic nerve injury models were established in Sprague­Dawley (SD) rats, and the function of miR­204 was either enhanced or inhibited through injection of miR­204 mimic and inhibitor, respectively. Subsequently, the mRNA and protein levels of miR­204, GAP­43, toll­like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88) and nuclear factor­κB (NF­κB) were examined in retinal tissues using reverse transcription­quantitative polymerase chain reaction and western blot analyses. The apoptosis of retinal tissue cells was also detected using a terminal deoxynucleotidyl transferase mediated dUTP nick end labeling assay. There was a significant increase in the level of miR­204 in retinal blood vessels of the model SD rats, compared with that in the normal SD rats (P<0.05), and the expression of GAP­43 was significantly decreased (P<0.05). The results confirmed that the expression of GAP­43 was significantly reduced, compared with that in the normal control group when the rats were treated with miR­204 mimic (P<0.05), which was similar to the result in the model group. By contrast, its expression of GAP­43 was significantly increased when treated with the miR­204 inhibitor (P<0.05). Compared with the normal control group, the expression levels of TLR4, MyD88 and NF­κB were significantly increased in the miR­204 mimic group and model group (P<0.05), whereas the same three factors in the miR­204 inhibitor group were effectively inhibited, compared with those in the model group, and showed similar results to the normal control group. The apoptotic rates of retinal cells in the miR­204 mimic group and model group were significantly increased, compared with that in the normal control group (P<0.05), whereas miR­204 inhibitor effectively reversed the effects on apoptotic rate observed in the model group, showing similar results to those in the normal control group. Taken together, miR­204 promoted the apoptosis of retinal cells through inhibiting GAP­43, providing theoretical guidance for the function of GAP­43 in retinal injury.

Impairment of autoregulation of optic nerve head blood flow during vitreous surgery in patients with hypertension and hyperlipidemia.

PURPOSE: To examine whether hypertension (HTN) and hyperlipidemia (HL) affect autoregulation of optic nerve head (ONH) blood flow during vitrectomy. DESIGN: Cohort study. METHODS: Seventeen eyes from 17 subjects with HTN and HL and 19 eyes from 19 control subjects without systemic disorders underwent vitrectomy for the treatment of epiretinal membrane or macular hole. Following standard 25-gauge microincision vitrectomy, the mean blur rate (MBR), which is an index of relative ONH blood flow, in the vascular area (vascular MBR) and MBR in the tissue area (tissue MBR) were measured using laser speckle flowgraphy. Measurements were conducted before and 5 and 10 min after an approximately 15-mmHg rise in intraocular pressure (IOP). Both parameters represent relative values of ONH blood flow (%, compared to baseline). The recovery rate of blood flow to the ONH was calculated using the following equation: (MBR at 10 min - MBR at 5 min)/(MBR at baseline - MBR at 5 min). RESULTS: Ocular perfusion pressure in all subjects was reduced both 5 and 10 min after the increase in IOP. Vascular MBR in subjects with HTN and HL (75.5 ± 14.8) was significantly lower than that in control subjects (86.7 ± 12.1) 10 min after IOP elevation (P = 0.019). The recovery rate of vascular blood flow was significantly lower in the HTN and HL groups than in the control group (P = 0.002). CONCLUSIONS: Our results suggest that HTN and HL impair autoregulation in the vascular component of ONH blood flow during vitrectomy.