Microvascular study of the retrolaminar optic nerve in man: the possible significance in anterior ischaemic optic neuropathy

The Relationship Between Artificial Intelligence-Assisted OCT Angiography-Derived Foveal Avascular Zone Parameters and Visual-Field Defect Progression in Eyes with Open-Angle Glaucoma

Purpose

To investigate clinical factors associated with foveal avascular zone (FAZ) parameters obtained using OCT angiography (OCTA) with assistance from a previously developed artificial intelligence (AI) platform in eyes with open-angle glaucoma (OAG).

Design

Retrospective longitudinal.

Participants

This study followed up 885 eyes of 558 patients with OAG for ≥ 2 years; all eyes underwent ≥ 5 Humphrey visual-field (VF) tests and had 3.0 × 3.0 mm macular OCTA scans available.

Methods

Average total deviation (TD) in the superior, superocentral, inferocentral, and inferior sectors of the Humphrey 24-2 program was calculated. We collected 3.0 × 3.0 mm macular OCTA images from each patient and used a previously developed AI platform with these images to obtain FAZ parameters, including FAZ area, FAZ circularity index (CI), and FAZ perimeter. Multivariable linear mixed-effects models were used to analyze the relationship between FAZ parameters, TD or TD slope in each quadrant, and systemic factors, adjusting for potential confounding factors, including axial length.

Main Outcome Measures

Ophthalmic and systemic variables, FAZ parameters, and TD or TD slope in each quadrant.

Results

The multivariable model showed that FAZ parameters were correlated with both TD and TD slope in the inferocentral quadrant (β = -0.244 - 0.168, P < 0.001). Both upper-half and lower-half FAZ parameters were better associated with TD-inferocentral and TD-inferocentral slope than TD-superocentral or TD-superocentral slope in terms of β size and statistical significance, indicating that there was no evident vertical anatomical correspondence between TD in the central quadrant and FAZ parameters. Foveal avascular zone area enlargement was associated with female gender (β = 0.242, P = 0.003). Loss of FAZ circularity was associated with both aging and comorbid sleep apnea syndrome (SAS) (yes: 1, no: 0) (β = -0.188, P < 0.001; β = -0.261, P = 0.031, respectively). Foveal avascular zone perimeter elongation was associated with aging and female gender (β = 0.084, P = 0.040; β = 0.168, P = 0.042, respectively).

Conclusions

Artificial intelligence-assisted OCTA-measured FAZ enlargement and irregular shape might be good markers of ocular hypoperfusion and associated inferocentral VF defect progression in eyes with OAG. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Uveal vascular bed in health and disease: uveal vascular bed anatomy. Paper 1 of 2

The uveal vascular bed is the largest vascular system in the eye and has a role in supplying almost every tissue in the eyeball. This makes it the most important ocular vascular system. This is an up-to-date review of the literature of the entire uveal vascular bed in health based on detailed anatomy of the posterior ciliary arteries (PCAs), anterior ciliary arteries, cilioretinal arteries, and vortex veins. Although postmortem injection cast preparations gave us useful information on the morphology of the choroidal vascular bed; in vivo studies showed that they misled us for centuries about the in vivo situation. According to the postmortem cast studies, the uveal vascular bed has no segmental distribution, the uveal vessels anastomose freely with one another, there are inter-arterial and arteriovenous anastomoses in the choroid, and the choriocapillaris form a freely communicating and an uninterrupted vascular bed in the entire choroid.

Vascular supply of the optic nerve head: implications for optic disc ischaemia

The vascular supply of the optic nerve head is complex and remains incompletely delineated. Over the past 50 years, various investigators have attempted to clarify the relative contributions of the choroid, the short posterior ciliary arteries and the central retinal artery to the vascular beds of the inner retinal, prelaminar, laminar and retrolaminar segments of the nerve head. Conflicting theories have evolved, in no small part due to differing techniques of study, involving both flow parameters and anatomical constructs. These have included studies, both in normal subjects and in those with optic nerve ischaemia, of histopathology, electron microscopic corrosion casting, orbital colour Doppler flow studies, fluorescein angiography, indocyanine green angiography, laser Doppler flow studies, laser speckle flowgraphy, microperfusion and labelling studies and optical coherence tomography angiography. The nature of the optic disc, peripapillary retina and choroid microvasculature has implications for the pathophysiology of ischaemic optic neuropathy.

Intravitreal triamcinolone injections in non-arteritic anterior ischemic optic neuropathy - A retrospective report

BACKGROUND

Non-arteritic anterior ischemic optic neuropathy (NAION) is a common cause of vision loss but no treatment has demonstrated its efficiency. A preliminary study showed an improvement on the visual acuity (VA) in a group of patients who received intravitreal administration of triamcinolone acetonide (IVTA) versus a non-treated group. In the present series, the visual outcome of IVTA in NAION was evaluated on a larger group of patients.

METHODS

This retrospective, unmasked and non-randomized study took place at Reims University Hospital between 2009 and 2017. The data of consecutive patients presenting with isolated optic disc edema characteristic of recent NAION (<1month of visual acuity loss) were included. After informed consent, a single intravitreal injection of filtrated 4mg/0.1mL triamcinolone acetonide were administered. Twenty-seven control patients chose not to be injected and therefore served as controls. LogMar visual acuity (VA), VA rating (VAR) (1 line=0.1LogMAR=5 VAR letters), retinal nerve fiber layer thickness assessed by OCT and static visual field were evaluated at presentation, after 7days, after 3months and after 6months.

RESULTS

Sixty-eight patients with NAION were evaluated. Forty-one received IVTA, 29 were injected within 15days after the onset of symptoms and 12 after 15days. There was a higher proportion of patients improving VA of 2 lines or more (10 or more VAR letters) in the injected group (49%) compared with the non-injected group (11%, P=0.019). Among the patients injected before 15days, the proportion improving for 2 lines or more (55% vs. 11%, respectively, P=0.013) and for 3 lines or more (45% vs. 11%, respectively, P=0.035) were significantly higher than in the non-injected group. Also, comparing the VA at presentation with the VA after 6months in the injected eyes, it improved significantly (P=0.003) and also in the subgroup injected within 15days (P=0.0007) but not in the injected group after 15days (P=0.801). Visual field improvement was only observed in the subgroup of patients injected within 15days with a significant improvement of the mean deviation (dB) within 6months (P=0.015).

CONCLUSIONS

This follow-up study confirms the results of the previous series displaying an apparent benefit of intravitreal steroids injected in the acute phase of NAION. Only patients receiving IVTA within 15days from onset of NAION have a significant improvement of VA and visual field during the follow-up period of 6months.

Peripapillary Retinal and Choroidal Perfusion in Nonarteritic Ischemic Optic Neuropathy Using Optical Coherence Tomography Angiography

SIGNIFICANCE

Nonarteritic ischemic optic neuropathy (NAION) has been linked with vascular insufficiency, although the pathophysiology remains elusive. Optical coherence tomography angiography (OCTA) is a promising technology that noninvasively evaluates optic disc perfusion and that may help to characterize peripapillary vascular changes in NAION.

PURPOSE

This study aimed to evaluate peripapillary vascularity in NAION eyes and to compare it with fellow unaffected eyes and healthy control eyes using OCTA.

METHODS

In this cross-sectional study, OCTA of the optic nerve head was obtained in 10 nonacute unilateral NAION and 12 healthy age-matched controls using ZEISS Angioplex. Quantitative analysis of peripapillary retinal and choroidal vascularity of NAION eyes was done using the instrument's inbuilt algorithm and ImageJ software and compared with fellow and control eyes.

RESULTS

Mean total peripapillary superficial retinal vessel and perfusion density as calculated by the instrument was significantly reduced in NAION eyes compared with fellow eyes (13.93 ± 4.27 mm/0.36 ± 0.07 for NAION eyes; 17.77 ± 1.26 mm/0.43 ± 0.08 for fellow eyes; P = .01/P = .05). Using the ImageJ software technique, the mean superficial retinal perfusion was found to be significantly reduced in NAION eyes (0.17 ± 0.07) compared with fellow eyes (0.25 ± 0.06; P < .01) and control eyes (0.25 ± 0.04; P < .01). At the level of choriocapillaris, it was not significantly affected in NAION eyes (0.37 ± 0.13) versus fellow (0.34 ± 0.14; P = .1) and control eyes (0.31 ± 0.34; P = .83). Analysis with the two techniques yielded differing results: the ImageJ analysis technique found a 32% reduction in superficial retinal perfusion in NAION eyes, whereas the instrument's inbuilt algorithm found a 16% reduction compared with fellow and control eyes (P ≤.01).

CONCLUSIONS

Peripapillary vascularity can be estimated both at the retinal and choroidal levels using ImageJ software to analyze OCTA images. Retinal peripapillary vascularity is compromised in NAION eyes, but vascularity is not significantly affected at the choroidal level.

Biomarkers of lesion severity in a rodent model of nonarteritic anterior ischemic optic neuropathy (rNAION)

The rodent model of nonarteritic anterior ischemic optic neuropathy (rNAION) is similar in many of its pathophysiological responses to clinical NAION. Like human NAION, there is significant variability in the severity of the lesion produced, and little is known of the parameters associated with rNAION induction severity or if pre- or early post-induction biomarkers can be identified that enable prediction of lesion severity and ultimate loss of retinal ganglion cells (RGCs). Adult male Sprague-Dawley outbred rats were evaluated for various parameters including physiological characteristics (heart rate, respiratory rate, temperature, hematocrit [Hct]), optic nerve head (ONH) appearance, pre- and post-induction mean diameter, and intravenous fluorescein and indocyanine green angiographic patterns of vascular leakage at 5 hours post-induction, performed using a spectral domain-optical coherence tomography (SD-OCT) instrument. Early changes were correlated with ultimate RGC loss by Brn3a (+) immunohistology. RGC loss also was correlated with the relative level of laser exposure. The severity of ONH edema 2d, but not 5hr, post induction was most closely associated with the degree of RGC loss, revealing a threshold effect, and consistent with a compartment syndrome where a minimum level of capillary compression within a tight space is responsible for damage. RGC loss increased dramatically as the degree of laser exposure increased. Neither physiological parameters nor the degree of capillary leakage 5hr post induction were informative as to the ultimate degree of RGC loss. Similar to human NAION, the rNAION model exhibits marked variability in lesion severity. Unlike clinical NAION, pre-induction ONH diameter likely does not contribute to ultimate lesion severity; however, cross-sectional ONH edema can be used as a biomarker 2d post-induction to determine randomization of subjects prior to inclusion in specific neuroprotection or neuroregeneration studies.

Ocular and Systemic Factors Affecting Laser Speckle Flowgraphy Measurements in the Optic Nerve Head

Purpose

To investigate the ocular and systemic factors related to glaucoma and to be adjusted for interindividual comparison of ocular blood flow measurement results by laser speckle flowgraphy (LSFG) obtained from the optic nerve head (ONH) in normal Japanese individuals.

Methods

A multicenter, prospective cross-sectional study was conducted. The ONH tissue-area and vessel-area mean blur rate (MT and MV) were evaluated using LSFG and ONH structural parameters using planimetric methods. Multivariate linear mixed-effects modeled regression analysis was used to identify the contributing factors to the MT and MV. The explanatory variables were age; gender; smoking history; body mass index; mean arterial pressure (MAP); heart rate; intraocular pressure; axial length (AL); disc, rim, cup, and β-peripapillary atrophy (β-PPA) areas; and central retinal artery and vein equivalents.

Results

In total, 195 eyes of 126 healthy individuals with an average age of 48.1 years were included. Multivariate analysis showed that MAP and disc area had a negative (P < 0.001) correlation, whereas β-PPA area had a positive correlation with MT (P = 0.010). Age and AL had a negative correlation (P = 0.001 and P = 0.011, respectively), whereas cup area had a positive correlation (P = 0.012) with MV.

Conclusions

Interindividual comparison of MT or MV must be adjusted for both systemic factors (blood pressure or age) and local ocular factors (AL and disc, cup, or β-PPA area).

Translational Relevance

Our results provided reference data on the LSFG measurement and are important in comparing ocular blood flow between individuals using LSFG.

Differentiation of Nonarteritic Anterior Ischemic Optic Neuropathy from Normal Tension Glaucoma by Comparison of the Lamina Cribrosa

Purpose

To compare lamina cribrosa (LC) morphology between eyes with nonarteritic anterior ischemic optic neuropathy (NAION) and eyes with normal tension glaucoma (NTG) in the Korean population.

Methods

This retrospective study included 48 eyes with NAION, 48 eyes with NTG, and 48 healthy control eyes matched by age, intraocular pressure, axial length, and optic disc area. Eyes with NAION and NTG were also matched by retinal nerve fiber layer (RNFL) thickness in the affected sector. Optic nerve heads were scanned using enhanced depth imaging spectral-domain optical coherence tomography. LC depth (LCD) and the LC curvature index (LCCI) were measured at seven locations spaced equidistantly across the vertical optic disc diameter. LCD and the LCCI were compared in the three groups.

Results

RNFL thicknesses of the matched affected sectors did not differ between the NAION and NTG groups (P = 0.347). LCD and the LCCI were significantly larger in the NTG group than in the NAION and healthy control groups at all seven planes (P < 0.001 each), but were comparable in the NAION and healthy control groups. The LCCI was larger in the affected than in the unaffected sector of NTG eyes (P = 0.010) but did not differ in NAION eyes (P = 1.000). LCD did not differ between affected and unaffected sectors in either NAION (P = 0.600) or NTG (P = 0.098) eyes.

Conclusions

LC morphology differed in eyes with NAION and NTG, despite a similar degree of RNFL damage. Evaluation of LC morphology may help to understand the distinctive pathophysiology of NAION and to differentiate NAION from NTG eyes.

Time-Course Changes in Optic Nerve Head Blood Flow and Retinal Nerve Fiber Layer Thickness in Eyes with Open-angle Glaucoma

PURPOSE

To determine whether decreased optic nerve head (ONH) blood flow (BF) precedes or follows decreased circumpapillary retinal nerve fiber layer thickness (cpRNFLT) in eyes with open-angle glaucoma (OAG).

DESIGN

Retrospective, longitudinal study.

PARTICIPANTS

This study followed up 350 eyes of 225 OAG patients for at least 2 years and collected data from each patient from at least 5 examinations obtained with laser speckle flowgraphy (LSFG) and OCT.

METHODS

In the superior, temporal, and inferior ONH quadrants, tissue area mean blur rate (MT), representing ONH tissue BF, was measured with LSFG, whereas cpRNFLT was measured with OCT. A multivariate linear mixed-effects model was used to identify potential predictors of faster MT decrease, adjusting for possible confounding factors. Based on these results, each quadrant of each patient was assigned a risk point if the quadrant was the superior or temporal, if patient age was older than the median (61 years), and if patient pulse rate was higher than median (74 beats per minute). The quadrants were then compared with a mixed-effects Cox model for MT and cpRNFLT changes, defined as a difference between the baseline value and the values from the latest 2 consecutive follow-up visits of more than 1.96 × the corresponding coefficient of variation.

MAIN OUTCOME MEASURES

Ophthalmic and systemic variables and MT and cpRNFLT in the superior, temporal, and inferior quadrants.

RESULTS

The multivariate model showed that MT decrease was faster in older patients with higher pulse rate and slower in inferior quadrants (P < 0.05). Quadrants with 0 risk points showed primary cpRNFLT decrease (P = 0.048), 1-risk point quadrants showed simultaneous cpRNFLT and MT decrease (P = 0.260), and 2-risk point and 3-risk point quadrants showed primary MT decrease (P < 0.001).

CONCLUSIONS

Older patients with higher pulse rate are at greater risk of a primary reduction in ONH tissue BF, that is, preceding cpRNFLT decrease, in the superior and temporal quadrants.

Good long-term visual outcomes of parapapillary choroidal melanoma patients treated with proton therapy: a comparative study

PURPOSE

To evaluate why small- and certain medium-sized parapapillary choroidal melanoma (pcM) patients treated with hypo-fractionated proton therapy (PT) retain excellent long-term visual acuity (VA) and assess the negative predictive factors for retaining good vision (≤ 0.2 logMAR (≥ 0.6 decimal) after 5 years.

METHODS

This single-center, retrospective, comparative study recruited consecutive pcM patients that were treated with PT. Between 1984 and 2005, 609 patients received a total of 60 CGE, of whom 310 met the following inclusion criteria: posterior tumor border ≤ 2.5 mm from the optic disc, largest tumor diameter ≤ 17.9 mm, tumor thickness ≤ 5.2 mm and available follow-up data for at least 5 years.

RESULTS

Mean follow-up was 120.8 ± 48.8 months (54.0-295.0). Out of 310 patients, 64 (21%) maintained a VA ≤ 0.2 logMAR (≥ 0.6 decimal) for at least 5 years following PT and were allocated to the "good visual outcome" (GVO) group, while the remaining 246 (79%) constituted the "poor visual outcome" (PVO) group, subdivided into 70 (22%) with a VA of 0.3-1.0 logMAR (0.1-0.5 decimal) and 157 (57%) patients with a VA > 1.0 logMAR (< 0.1 decimal). On multivariate analysis, older age (P = 0.04), tumor localization ≤ 0.5 mm to the fovea (P < 0.03), volume of the optic disc and macula receiving 50% of dose (30 CGE) (P = 0.02 and P < 0.001, respectively) were independent negative predictors of GVO.

CONCLUSIONS

Of 310 small- to medium-sized pcM patients successfully treated with PT, 21% retained a VA ≤ 0.2 logMAR (≥ 0.6 decimal) for at least 5 years. Strongest negative predictive factor for retaining good long-term vision was the volume of the macula irradiated with at least 30 Gy.

Unraveling the Enigma of Nonarteritic Anterior Ischemic Optic Neuropathy

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

Relationship between ocular risk factors for glaucoma and optic disc rim in normal eyes

AIM

To study relationships between reported risk factors for glaucoma and neuroretinal rim area in normal eyes.

METHODS

The Kumejima study participants, 3762 of the 4632 eligible Kumejima residents 40 years and older, underwent a detailed ocular examination including sequential disc stereo photography. In a randomly chosen eye of a subject whose both eyes met the inclusion criteria, fundus photographs of 2474 ophthalmologically normal eyes of the 2474 subjects were analysed by computer-assisted planimetry to measure the disc, rim and β-peripapillary atrophy (PPA) areas. The rim was divided into the superior and inferior halves by a line connecting the fovea and disc centre.

RESULTS

The disc, superior and inferior halves rim and β-PPA areas averaged 2.53±0.50 (SD), 0.82±0.15, 0.84±0.16 and 0.45±0.66 mm². After adjustment for other systemic and ocular factors including age, disc and β-PPA areas, disc-fovea distance (p=0.013, 0.016) correlated positively and intraocular pressure (IOP) (p=0.004, 0.006) and axial length (AL) (p<0.000, 0.004) negatively with the superior and inferior halves rim area, respectively; central corneal thickness (CCT) (p=0.008) and mean blood pressure (mBP) (p=0.020) correlated positively and male gender (p=0.012) negatively only with the superior half rims.

CONCLUSIONS

Besides previously reported risk factors for glaucoma such as age or IOP, thinner CCT, lower mBP and male gender were newly found to significantly correlate with smaller rim area only in the superior half disc, and a greater disc-fovea distance with greater superior and inferior half rim areas in normal adult eyes.

The swollen optic nerve: an approach to diagnosis and management

The differential diagnosis of swollen optic nerves differs according to whether the swelling is unilateral or bilateral, or whether visual function is normal or affected. Patients with a unilaterally swollen optic nerve and normal visual function most likely have optic nerve head drusen. Patients with abnormal visual function most likely have demyelinating optic neuritis or non-arteritic anterior ischaemic optic neuropathy. Patients with bilaterally swollen optic nerve heads and normal visual function most likely have papilloedema, and require neuroimaging followed by lumbar puncture. However, if their visual function is affected, the most likely causes are bilateral demyelinating optic neuritis, neuromyelitis optica spectrum disorder and anti-myelin oligodendrocyte glycoprotein optic neuritis: these patients require investigating with contrast-enhanced MRI of the orbits.

Temporal Raphe Sign for Discrimination of Glaucoma from Optic Neuropathy in Eyes with Macular Ganglion Cell-Inner Plexiform Layer Thinning

PURPOSE

To evaluate the potential of the temporal raphe sign on the macular ganglion cell-inner plexiform layer (mGCIPL) thickness map for discriminating glaucomatous from nonglaucomatous optic neuropathy (NGON) in eyes with mGCIPL thinning.

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 175 eyes of 175 patients with mGCIPL thinning on Cirrus (Carl Zeiss Meditec, Dublin, CA) high-definition OCT were retrospectively included. Glaucoma specialists and neuro-ophthalmology specialists evaluated the patients' medical records for diagnosis of glaucomatous optic neuropathy (GON) or NGON. Finally, by consensus, 67 eyes with GON and 73 eyes with NGON were enrolled.

METHODS

A positive temporal raphe sign was declared in patients in whom there was a straight line longer than one-half of the length between the inner and outer annulus in the temporal elliptical area of the mGCIPL thickness map. Decision tree analysis was performed to formulate a diagnostic model.

MAIN OUTCOME MEASURES

Area under receiver operating characteristic curve (AUC) with sensitivity and specificity.

RESULTS

The temporal raphe sign was observed in 61 of 67 GON eyes (91.0%), but in only 21 of 73 NGON eyes (28.8%) (P < 0.001; chi-square test). On this basis, the diagnostic ability of the temporal raphe sign for discriminating GON from NGON was judged to be good (AUC, 0.811; 95% confidence interval, 0.749-0.874; sensitivity, 91.0%; specificity, 71.2%). The diagnostic performance of the decision tree-based model (AUC 0.879; 95% confidence interval, 0.824-0.933; sensitivity, 88.1%; specificity, 87.7%) was better than that of the temporal raphe sign or the relative afferent pupillary defect (RAPD) alone (P = 0.005, P < 0.001, respectively; DeLong's test). The decision tree model revealed the following: (1) If the temporal raphe sign is positive and the RAPD is absent, the case should be diagnosed as GON; (2) if the temporal raphe sign is absent regardless of the presence or absence of the RAPD, or both the temporal raphe sign and the RAPD are present, the case should be diagnosed as NGON.

CONCLUSIONS

In clinical practice, determining whether the temporal raphe sign appears on OCT macular scans can be a useful tool for discrimination of glaucomatous from nonglaucomatous mGCIPL thinning.

Sequential nonarteritic anterior ischemic optic neuropathy in patient on chronic hemodialysis

Nonarteritic anterior ischemic optic neuropathy (NAION) is a well acknowledged rare complication of chronic hemodialysis in patients with end-stage renal disease (ESRD). We present a unique case of a patient on chronic hemodialysis who presented with an NAION in the right eye, then 3 months later developed an NAION in the left eye followed in 1 month by second NAION episode in the left eye. Every episode of NAION was accompanied by intradialytic hypotension (drop in systolic blood pressure of over 20 mmHg) where visual loss was noticed at the end of the dialysis session. Clinicians should be aware of association between NAION and hemodialysis and that patients with dialysis-induced hypotension are at particularly increased risk of having NAION. Patients who had dialysis-associated NAION should be closely monitored to prevent occurrence of intra-dialytic hypotension as they are at the highest risk of sequential NAION and thus severe visual loss.

Update on Perioperative Ischemic Optic Neuropathy Associated With Non-ophthalmic Surgery

Perioperative visual loss (POVL) is a rare, serious complication of non-ophthalmic surgeries. Ischemic optic neuropathy (ION), and retinal arterial occlusion (RAO) are the main causes (1, 2). Less frequent are cortical blindness (3), acute glaucoma (4), and choroidal and vitreous hemorrhage (5). ION is the most common cause for which the neurologist or neuro-ophthalmologist is consulted as it is associated either with a normal ophthalmic exam (posterior ION, PION), or less often, with optic nerve (ON) head swelling (anterior ION, AION). The presumed cause is impaired blood supply to the optic nerve (Figure 1). The most common surgical procedures complicated by ION are cardiac surgery and spinal fusion. Retrospective studies, surveys, and case reports are the basis of most knowledge regarding peri-operative ION (poION), with cohort and case-control studies helping to identify candidate risk factors (6, 7). Animal models have provided insight regarding mechanisms (8). This mini-review is an update on the latest advancements regarding poION in non-ophthalmic surgeries in epidemiological, clinical, and animal studies.

Optical Coherence Tomography Angiography in Glaucoma Care

PURPOSE

To provide the reader with information on the principal techniques of optical coherence tomography angiography (OCTA); the current literature on OCTA reproducibility; its applications to glaucoma detection and monitoring of progression; and the role of OCTA in the assessment of the vascular component in glaucoma pathogenesis.

METHODS

A literature review of the pertinent publications for the OCTA in relation to the development, techniques, and its use in glaucoma was carried out.

RESULTS

Rapid improvements in optical coherence tomography (OCT) technology have allowed for enhancement of both image resolution and scanning speed, and the development of vascular assessment modality. OCTA is the non-invasive in vivo imaging of the vasculature located within the retina and optic nerve head area. The principle of OCTA is to use the variations in OCT signals caused by moving particles as the contrast mechanism for imaging of flow. Several algorithms which aim to maximize the contrast signal and minimize the noise have been developed including the phase-based techniques, intensity-based techniques (e.g., split-spectrum amplitude decorrelation angiography (SSADA)), and complex-based techniques (e.g., optical microangiography (OMAG)). With its reliable technique, high image resolution, and current availability, OCTA has been widely used in the assessment of posterior segment diseases including glaucoma in which ocular perfusion dysfunction has been proposed as a pathophysiological mechanism.

CONCLUSION

OCTA may enhance our knowledge of glaucoma pathogenesis and offer an improvement in our ability to detect glaucomatous change.

Optical Coherence Tomography Angiography in Nonarteritic Anterior Ischemic Optic Neuropathy

BACKGROUND

Optical coherence tomography angiography (OCTA) has demonstrated good utility in qualitative analysis of retinal and choroidal vasculature and therefore may be relevant in the diagnostic and treatment efforts surrounding nonarteritic anterior ischemic optic neuropathy (NAION).

METHODS

Retrospective, cross-sectional study of 10 eyes of 9 patients with a previous or new diagnosis of NAION that received imaging with OCTA between November 2015 and February 2016. Two independent readers qualitatively analyzed the retinal peripapillary capillaries (RPC) and peripapillary choriocapillaris (PCC) for flow impairment. Findings were compared with automated visual field and structural optical coherence tomography (OCT) studies.

RESULTS

Flow impairment seen on OCTA in the RPC corresponded to structural OCT deficits of the retinal nerve fiber layer (RNFL) and ganglion cell layer complex (GCC) in 80% and 100% of eyes, respectively, and to automated visual field deficits in 90% of eyes. Flow impairment seen on OCTA in the PCC corresponded to structural OCT deficits of the RNFL and GCC in 70% and 80% of eyes, respectively, and to visual field deficits in 60%-80% of eyes.

CONCLUSIONS

OCTA can noninvasively visualize microvascular flow impairment in patients with NAION.

Difference in patterns of retinal ganglion cell damage between primary open-angle glaucoma and non-arteritic anterior ischaemic optic neuropathy

PURPOSE

To compare the patterns of retinal ganglion cell damage between primary open-angle glaucoma (POAG) and non-arteritic anterior ischaemic optic neuropathy (NAION).

METHODS

In total, 35 eyes with unilateral NAION, and 70 age- and average peripapillary retinal nerve fibre layer (RNFL) thickness-matched eyes with POAG, were enrolled as disease groups; 35 unaffected fellow eyes of the NAION, and 70 age- and refractive error-matched normal subjects for the POAG, were enrolled as their control groups, respectively. The peripapillary RNFL thickness and macular ganglion cell plus inner plexiform layer (GCIPL) thickness were compared between the disease groups and their controls, and between the two disease groups.

RESULTS

Mean RNFL thicknesses at the 1 and 2 o'clock (superonasal) positions were thinner in NAION than in POAG (both p < 0.05). Mean RNFL thickness at 7 o'clock (inferotemporal) was thinner in POAG than in NAION (p = 0.001). Although there was no significant difference between NAION and POAG in average GCIPL thickness, all of the sectoral GCIPL thicknesses were thinner in NAION (all p < 0.05), except in the inferior and inferotemporal sectors. The ranges of the clock-hour RNFL with damage greater than the average RNFL thickness reduction, versus fellow eyes and control eyes, were 7 hours in NAION and 4 hours in POAG.

CONCLUSIONS

The more damaged clock-hour RNFL regions differed between NAION (1 and 2 o'clock) and POAG (7 o'clock). Most sectoral GCIPL thicknesses were thinner in NAION than in POAG.

Evaluation of Optic Nerve Head and Peripapillary Choroidal Vasculature Using Swept-source Optical Coherence Tomography Angiography

PURPOSE

The authors visualized arterioles from the peripapillary choroid to the optic nerve head in vivo, using swept-source optical coherence tomography angiography.

METHODS AND RESULTS

In this case series, we present 3 eyes with visible centripetal branches from the peripapillary choroid. The 3 eyes were diagnosed as glaucoma suspect, normal-tension glaucoma, and primary open-angle glaucoma. In the en face projection images of the choroidal layer, obtained by swept-source optical coherence tomography angiography, the vessels from the peripapillary choroid to the optic nerve head were observed in all 3 eyes; one of them was further evaluated by indocyanine green angiography using the Heidelberg retina angiograph. The filling pattern, as viewed on high-speed indocyanine green angiographic video, confirmed that the vessels were arterioles originating from the peripapillary choroid and supplying the prelaminar region of the optic nerve head.

CONCLUSIONS

The prelaminar region of the optic nerve head might be supplied by the peripapillary choroid in addition to the known major blood supply from the short posterior ciliary arteries.

PERIPAPILLARY ARTERIAL RING OF ZINN-HALLER IN HIGHLY MYOPIC EYES AS DETECTED BY OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To visualize the arterial circle of Zinn-Haller (ZHAC) in highly myopic patients by using OCT-A.

METHODS

Two hundred and fifty-three eyes of 146 consecutive patients with axial length ≥26.5 mm who underwent OCT-A centered onto the optic disk were studied.

RESULTS

Arterial circle of Zinn-Haller was detectable on OCT-A images within the area of the parapapillary myopic conus in 26 (10%) of 253 eyes. The ZHAC was annular in 18 (69%) eyes, triangular in (15%) 4 eyes, and irregular (15%) in 4 eyes. The visibility of the ZHAC on OCT-A images was similar to the visibility on indocyanine green angiograms and significantly better than on conventional fundus photos. Optical coherence tomography angiography visualized details of the ZHAC including the entry of the short posterior ciliary arteries into the circle up to the branches in direction to the optic nerve and ZHAC-associated cilioretinal arteries. In three eyes, the ZHAC was composed of multiple rings.

CONCLUSION

Noninvasive OCT-A allowed the visualization of ZHAC up to smaller vessel branches in 10% of highly myopic eyes. Because ZHAC is the main blood supply to lamina cribrosa of optic nerve, OCT-A-based assessment of ZHAC could become of interest in diseases such as glaucomatous optic neuropathy.

Ischemic optic neuropathies and their models: disease comparisons, model strengths and weaknesses

Ischemic optic neuropathies (IONs) describe a group of diseases that specifically target the optic nerve and result in sudden vision loss. These include nonarteritic and arteritic anterior ischemic optic neuropathy (NAION and AAION) and posterior ischemic optic neuropathy (NPION, APION). Until recently, little was known of the mechanisms involved in ION damage, due to a lack of information about the mechanisms associated with these diseases. This review discusses the new models that closely mimic these diseases (rodent NAION, primate NAION, rodent PION). These models have enabled closer dissection of the mechanisms involved with the pathophysiology of these disorders and enable identification of relevant mechanisms and potential pathways for effective therapeutic intervention. Descriptions of the different models are included, and comparisons between the models, their relative similarities with the clinical disease, as well as differences are discussed.

Intravitreal triamcinolone injections in non-arteritic anterior ischemic optic neuropathy

BACKGROUND

In non-arteritic anterior ischemic optic neuropathy (NA-AION), no treatments have demonstrated to be effective in recovering visual loss in randomized clinical trials. Oral steroids have been evaluated, and small series of intravitreal triamcinolone acetonide (IVTA) injection in NA-AION have been reported. The purpose of our study was to report the visual outcome and morphological changes in response to a single IVTA injection as a treatment for patients with NA-AION.

PATIENTS AND METHODS

The charts of 36 patients with visual symptoms and optic disc swelling caused by NA-AION were evaluated. Twenty-one patients had received 4 mg IVTA and were compared with 15 non-treated patients. Visual acuity (VA), retinal nerve fiber layer thickness and static visual field were evaluated after 6 months.

RESULTS

VA improvement at 6 months is statistically better in the treated group than in the non-treated group (p = 0.0035). In the treated group, there was a significant inverse correlation between the delay of the injection and the visual acuity achieved at 6 months (p < 0.0083**, r = -0.56). A significant improvement of the visual field was noted in the injected group when compared with the non-treated group at 6 months (p < 0.0028).

DISCUSSION

In this retrospective study, patients receiving IVTA in the acute phase of NA-AION have better improvement of VA and visual field during the follow-up period of 6 months. However, only a large randomized controlled trial may enable to evaluate the benefits of IVTA Injections on visual outcome in NA-AION.

Regional morphology and pathophysiology of retinal vascular disease

Disturbances in the retinal vascular supply are involved in the pathophysiology of the most frequent diseases causing visual impairment and blindness in the Western World. These diseases are diagnosed by noting how morphological lesions in the retina vary in shape, size, location and dynamics, and subsequently concluding the presence of a specific disease entity. This diagnostic approach can be used to identify the site of a retinal vascular occlusion, to assess whether retinal diseases are primarily due to changes in the larger retinal vessels or the microcirculation, and to differentiate the relative involvement of the choroidal and the retinal vascular systems. However, a number of morphological manifestations of retinal vascular disease cannot presently be related to the underlying pathophysiology. The review concludes that there is a need for developing new methods for assessing vascular structure and function in the ciliary vascular system supplying the choroid and the optic nerve head. Presently, the study of these structures relies on imaging techniques with limited penetration and resolution into the tissue. Secondly, there is a need for studying oscillations in retinal vascular function occurring within days to weeks, and for studying regional manifestations of retinal vascular disease. This may constitute the basis for future research in retinal vascular pathophysiology and for the development of new treatment modalities to reduce blindness secondary to retinal vascular disease.

Detection of Zinn-Haller arterial ring in highly myopic eyes by simultaneous indocyanine green angiography and optical coherence tomography

PURPOSE

To determine the intrascleral location of the circle of Zinn-Haller by simultaneous indocyanine green (ICG) angiography and enhanced-depth imaging optical coherence tomography (EDI-OCT) in highly myopic eyes.

DESIGN

Retrospective, consecutive, observational case series.

METHODS

Ninety-four eyes of 67 consecutive patients with pathologic myopia who underwent simultaneous ICG angiography and EDI-OCT examinations by Spectralis HRA-OCT, and whose Zinn-Haller ring was observed within the area of myopic conus by ICG angiography, were studied. The definition of pathologic myopia was a refractive error (spherical equivalent) <-8.00 diopters (D) or an axial length >26.5 mm.

RESULTS

The EDI-OCT images showed cross-sections of the vessels that were identified in the ICG images as the circle of Zinn-Haller. The vessels were seen as a hyporeflective circle within the peripapillary sclera. An intrascleral course of the Zinn-Haller ring was clearly observed in adjacent serial OCT sections. The filling of the Zinn-Haller ring was from the short posterior ciliary arteries, and OCT also showed a continuous pathway from the retrobulbar short posterior ciliary arteries to the circle of Zinn-Haller. Centripetal branches were seen to run toward the optic nerve from the Zinn-Haller ring in 20 eyes by ICG and were confirmed by OCT in 4 eyes.

CONCLUSIONS

The HRA-OCT images confirmed that the vascular structure surrounding the optic disc observed by ICG angiography had topographic features specific to the Zinn-Haller arterial ring by OCT. The in situ observation of the circle of Zinn-Haller by simultaneous ICG angiography and OCT is a useful method to examine the Zinn-Haller ring in eyes with pathologic myopia.

Perioperative vision loss: A complication to watch out

Postoperative vision loss, a rare but devastating complication, has been reported after spine, cardiac, and head–neck surgeries. Its incidence following spine surgeries exceeds that after cardiothoracic surgeries. Various causes attributed to postoperative blindness include ischemic optic neuropathy, central or branch retinal artery occlusion, cortical blindness, and rarely external ocular injury. Other contributory factors described are microvascular diseases and intraoperative hemodynamic compromise. However, the exact association of these factors with postoperative blindness has not yet been confirmed. In this review, we describe causes, presentation, and treatment of postoperative blindness and also recommend practical guidelines to avoid this complication. The search strategies for this review included both search of electronic databases as well as manual search of relevant articles.

Ischaemia in the Zinn-Haller circle and glaucomatous optic neuropathy in macaque monkeys

Aims

To elucidate the morphological features of optic neuropathy in an ischaemic model of glaucoma in macaque monkeys.

Methods

The regional degenerative process was investigated by experimentally occluding the paraoptic branches of the lateral short posterior ciliary artery, that is, the circle of Haller and Zinn, in 11 eyes. Morphological changes in nerve fibres in the lamina cribrosa were evaluated by histopathology, immunocytochemistry and angiography, and the findings were compared with those observed in an aged macaque with spontaneous glaucomatous optic neuropathy.

Results

Retinal ganglion cell axons were grouped in bundles and traversed through pores in columns of the lamina cribrosa. The processes of astrocytes extended to the bundles, and capillaries branched in surrounding connective tissue from the circular arterioles. Experimental ischaemia induced time-dependent anoxic deterioration of phosphorylated fibres in the temporal arcuate zone, accompanied by glial proliferation. A monkey with spontaneous visual impairment had nerve fibre loss and gliosis with collagenous proliferation in the temporal hemisphere, suggesting glaucomatous neuropathy.

Conclusions

Circulatory interference in the circle of Haller and Zinn caused time-dependent deterioration in the area where anoxic segmental degeneration is associated with pathogenesis of open-angle glaucoma.

Histomorphometry of the circular peripapillary arterial ring of Zinn-Haller in normal eyes and eyes with secondary angle-closure glaucoma

PURPOSE

To examine the location and size of the peripapillary arterial circle of Zinn-Haller (PACZH) and its associations with other eye measures in normal eyes and eyes with secondary angle-closure glaucoma.

METHODS

  The study included 29 human globes enucleated because of malignant choroidal melanoma (n = 19) (control group) or because of secondary angle-closure glaucoma (n=10). Anterior-posterior histological sections were morphometrically evaluated.

RESULTS

The PACZH was present in all eyes. The glaucoma group and the control group did not vary significantly in the distance from the PACZH to Bruch's membrane (297 ± 67 versus 270 ± 67 μm; p = 0.29), optic disc border (281 ± 103 versus 391 ± 170 μm; p=0.07), optic disc centre (1059 ± 191 versus 978 ± 205μm; p = 0.30) and retrobulbar cerebrospinal fluid space (173 ± 58 versus 172 ± 81 μm; p = 0.97) nor in the minimal PACZH diameter (39± 18 versus 36 ± 18 μm; p = 0.74) and maximal PACZH diameter (78 ±37 versus 65 ± 25 μm; p = 0.36). The PACZH location, measured as distance from Bruch's membrane, disc border, disc centre and cerebrospinal fluid space, was not significantly associated with axial length (p > 0.39), horizontal globe diameter (p > 0.17) and vertical globe diameter (p > 0.22). Both diameters were statistically independent of axial length (p = 0.72 and p = 0.58, respectively), horizontal globe diameter (p = 0.60 and p = 0.41, respectively) and vertical globe diameter (p = 0.64 and p = 0.52, respectively). All parameters were statistically independent of age (p > 0.10) and gender (p > 0.10).

CONCLUSIONS

The PACZH was present in all human eyes examined and did not vary significantly in location and diameter between eyes with secondary angle-closure glaucoma and nonglaucomatous eyes, nor between myopic versus hyperopic eyes.

Central retinal vein occlusion with cilioretinal infarction from branch flow exclusion and choroidal arterial steal

PURPOSE

The first definitive study of retinal vein occlusion complicated by infarction within the territory of one or more cilioretinal arteries was published in 1976. Many individual cases and further case series have been reported in the interim, but the nature of the interrelationship is still under debate.

METHODS

A review was undertaken of the relevant clinical and fundus fluorescein angiographic characteristics of this combined retinal vascular disorder together with the pathophysiological mechanisms currently presented in the literature to explain their association. Scientific publications up to 2008 were evaluated by one of the authors of the original report.

RESULTS

There are broad similarities between publications in their descriptions of the clinical features, but significant differences of detail and interpretation are also evident. Most of the mechanisms so far proposed to account for cilioretinal infarction after central or hemisphere retinal vein occlusion do not withstand critical scrutiny. Two related hypotheses are expounded that appear to satisfactorily elucidate this interrelationship -- branch flow exclusion and branch flow diversion (otherwise termed "choroidal arterial steal").

CONCLUSION

In eyes with a cilioretinal supply, the probability that cilioretinal infarction will complicate retinal vein occlusion increases with increasing severity of venous obstruction and the more distally the cilioretinal artery arises from the posterior ciliary arterial tree. A distal branch point also facilitates observation of dye front reciprocation within the artery. Indicators of the degree of venous obstruction that may be necessary to instigate cilioretinal infarction include very prolonged dye transit times in the central retinal circulation, exaggerated venous cyanosis and tortuosity, perivenous cotton-wool sentinels, and macular perivenular whitening.

Intravitreal triamcinolone acetonide injection for acute non-arteritic anterior ischaemic optic neuropathy

Non-arteritic anterior ischaemic optic neuropathy is the most common optic neuropathy of the elderly, characterised by unilateral, sudden, painless visual loss. No effective treatment has been proven to reverse or limit the course of this disease. We evaluated the role of intravitreal triamcinolone acetonide injection in eyes with non-arteritic anterior ischaemic optic neuropathy (NAION). Four eyes of four patients with acute NAION received a single intravitreal injection of triamcinolone acetonide (4 mg). The time between visual loss and intravitreal injection varied between four and 10 days. Mean age of patients was 57.25 years (range, 44 to 77 years). All patients experienced some visual gain. No complications related to the injection were observed during the following three months. Intravitreal triamcinolone injection may offer help in limiting the damage in this small group of patients with a relatively short history of visual loss due to NAION.

Nonarteritic anterior ischemic optic neuropathy

PURPOSE OF REVIEW

Nonarteritic anterior ischemic optic neuropathy remains a disease that is poorly understood in many aspects. The clinical presentation may diverge significantly from the classic unilateral, painless, sudden vision loss affecting patients over the age of 50 years. This variability might make nonarteritic anterior ischemic optic neuropathy hard to differentiate from optic neuritis and arteritic ischemic optic neuropathy. The course of nonarteritic anterior ischemic optic neuropathy is also variable, often sequentially affecting the other eye.

RECENT FINDINGS

Visual recovery has been reported, but it is not the rule. Multiple risk factors have been proposed, including crowded disc, atherosclerosis, diabetes, hyperlipidemia, hypertension, hypotension, hemoconcentration, hemodilution, and hypercoagulable states. The optic nerve damage in nonarteritic anterior ischemic optic neuropathy appears to result from a perfusion insufficiency in the short posterior ciliary arteries leading to infarction of the retrolaminar portion of the optic disc. The underlying mechanisms are still unclear, however. Multiple medical and surgical treatment options have been investigated, including optic nerve sheath decompression, standard and megadose corticosteroids, levodopa, carbidopa, hyperbaric oxygen, and neuroprotective agents, but no proven effective treatment is currently available.

SUMMARY

Intense investigations in humans and animals are under way. Hopefully these studies will enhance our understanding of the risk factors and pathophysiology of nonarteritic anterior ischemic optic neuropathy and aid in developing new strategies for prevention and treatment.

Does altered fractionation influence the risk of radiation-induced optic neuropathy?

PURPOSE

To analyze the parameters that influence the risk of radiation-induced optic neuropathy (RION) after radiotherapy for head-and-neck tumors.

METHODS AND MATERIALS

Between 1964 and 2000, 273 patients with tumors of the nasopharynx, paranasal sinuses, nasal cavity, and hard palate adenoid cystic carcinomas were treated with curative intent and had radiation fields that included the optic nerves and/or chiasm. Patients were followed for at least 1 year after radiotherapy.

RESULTS

Radiation-induced optic neuropathy developed in 32 eyes of 24 patients (9%). The 5-year rates of freedom from RION according to the total dose and once- vs. twice-daily fractionation were as follows: < or =63 Gy once daily, 95%; < or =63 Gy twice daily, 98%; >63 Gy once daily, 78%; and >63 Gy twice daily, 91%. Multivariate analysis revealed that the total dose affected the risk of RION (p = 0.0047), with patient age (p = 0.0909), once-daily vs. twice-daily fractionation (p = 0.0684), and overall treatment time (p = 0.0972) were marginally significant. The use of adjuvant chemotherapy did not significantly influence the likelihood of developing RION.

CONCLUSION

The likelihood of developing RION is primarily influenced by the total dose. Hyperfractionation may reduce the risk of experiencing this complication.

Treatment of ischemic optic neuropathy

Ischemic damage of the optic nerve has no proven effective treatment. While ischemia related to vasculitis (arteritic) is treated with systemic corticosteroids, the primary goal is to prevent further damage, either in the affected or fellow eye. Thrombolytic or anticoagulation supplementive therapy may be considerations for the future. In the more common idiopathic (nonarteritic) form (NAION), multiple attempts at therapy, including systemic corticosteroids, anticoagulants and antiplatelet agents, diphenylhydantoin, hyperbaric oxygen, and optic nerve sheath decompression have been unsuccessful. The use of levodopa has been proposed but is unproven. Megadose intravenous corticosteroid therapy has not been studied in a systematic way. Neuroprotective strategies are under intense investigation for optic neuropathies including NAION, and clinical trials in humans are in progress. Optic nerve regeneration studies are ongoing in animals. Prophylaxis in NAION is unproven.

Clinical assessment of optic nerve disorders

Optic nerve disorders range from the manifestations of life-threatening intracranial or systemic disease, to minor congenital anomalies. Careful clinical assessment, which relies upon a thorough evaluation of symptoms as well as signs, is essential for effective and timely investigation and treatment. Examination methods and pitfalls to be avoided are discussed.

The morphology of an infarct in nonarteritic anterior ischemic optic neuropathy

OBJECTIVE

The mechanism by which nonarteritic anterior ischemic optic neuropathy (NAION) causes an infarct in the optic nerve is controversial. We studied the three-dimensional anatomic configuration of a NAION infarct to better elucidate its pathophysiology.

DESIGN

Case report with clinicopathologic correlation.

METHODS

Serial sections of the optic nerve from a previously reported patient diagnosed with NAION 20 days before death were studied. Every fourth slide was stained with hematoxylin-eosin, photographed, and digitized. NIH Image 1.62 was used to reconstruct the nerve in all three dimensions, and the infarct morphology was analyzed.

MAIN OUTCOME MEASURES

Morphology of the reconstructed optic nerve infarct.

RESULTS

The area of axonal loss within each section of the optic nerve was identified and reconstructed. The loss was in the superior part of the nerve, encircling the central retinal artery at its greatest extent. Remaining areas of the nerve appeared healthy, and, notably, the periphery of the uninvolved inferior portion of the nerve was normal. Three-dimensional analysis revealed two distinct areas of infarct at the posterior extent of the lesion which coalesced toward the center of the lesion and finally tapered as the infarct reached the optic nerve head. Sagittal reconstructions gave the appearance of a two-pronged fork posteriorly connecting to a single "handle" anteriorly. There was no obvious correlation between the configuration of the infarct and any single vascular territory. The total length of the nerve involved by the infarct was approximately 1.5 mm.

CONCLUSIONS

The morphology of this NAION infarct is not consistent with disease of large or small vessels and, more likely, represents a form of compartment syndrome that causes tissue ischemia.

Pathogenesis of nonarteritic anterior ischemic optic neuropathy

Based on histopathology, electron microscopic corrosion cast studies, optic nerve blood flow studies, and clinical data, the pathogenesis of idiopathic nonarteritic ischemic optic neuropathy includes the following features: (1) structurally crowded optic discs are predisposed; (2) laminar and retrolaminar regions are the most common locations for infarction; (3) there is flow impairment in the prelaminar optic disc during the acute phase; (4) lack of consistent choroidal flow impairment and the retrolaminar location of infarcts suggest vasculopathy within or distal to the paraoptic branches of the posterior choroidal arteries; (5) diabetes is the most consistently identified vasculopathic risk factor; (6) impaired autoregulation of the disc circulation by atherosclerosis, with a possible contribution from serotonin and endothelin-mediated vasospasm, may play a role; and (7) progression may be caused by secondary cell death after the initial ischemic insult or compression from cavernous degeneration and mechanical axonal distortion.

Postoperative blindness

This chapter discusses the cases of postoperative blindness reported in the literature and the theories that attempt to explain the mechanisms involved. Although uncommon, alterations in vision and blindness after anesthesia for major surgical procedures, particularly cardiopulmonary bypass or spine surgery, are well documented, with an incidence varying between 0.05% and 1%. Accurate incidence data are unavailable because it is not known what percentages are reported. However, the large number of case reports over many years has provided some significant information. Although sustained compression of the eye is an important cause, postoperative visual loss may also occur, in an unrelated manner, because of ischemic optic neuropathy, central retinal artery or vein occlusion, or cortical blindness.

Indocyanine green and fluorescein angiography in nonarteritic anterior ischemic optic neuropathy

PURPOSE

To assess the value of indocyanine green angiography (ICGA) for demonstrating choroidal vascular abnormalities in patients with nonarteritic anterior ischemic optic neuropathy (NAION).

METHODS

The authors compared the ICGA and fluorescein fundus angiography characteristics of peripapillary circulation in 11 patients with acute NAION. There were 7 men and 4 women; the age range for the patients was 36 years to 72 years (mean +/- SD, 47.7 +/- 10.76 years). The angiographic factors considered significant were delay of peripapillary choroidal filling in the vertical watershed zone, leakage from the optic disk, and absolute filling defects on the disk. The authors compared the incidence of a vertical peripapillary watershed zone in the eyes of the 11 patients with that in the normal eyes of 50 controls (age range, 44-79 years) who had unilateral age-related macular degeneration.

RESULTS

Indocyanine green angiography revealed a peripapillary watershed zone in 8 of 11 patient eyes and 23 of 50 control eyes. There was no statistical difference in the number of eyes affected in each group (chi2 = 0.53; P = 0.47). Fluorescein fundus angiography showed leakage from the disk in 10 of 11 patients, whereas ICGA highlighted this problem in only 7 of the patients. The choroidal filling time of the watershed zones was significantly longer with ICGA (t = 3.13; P = 0.011).

CONCLUSION

Although ICGA allows better visualization of the choroidal watershed zones associated with NAION, it did not reveal any significantly different incidence of vertical choroidal watershed zone encompassing the optic disk for patients with NAION and controls. Fluorescein fundus angiography better visualized leakage from the disk in the patient group. These findings indicate that ICGA offers no significant advantage in terms of clinical diagnosis and management of NAION.

Clinical spectrum of posterior ischemic optic neuropathy

PURPOSE

To describe the systemic and visual characteristics and prognosis in patients with posterior ischemic optic neuropathy (PION).

DESIGN

Observational case series.

METHODS

Retrospective chart review in a multicenter setting. Seventy-two patients (98 eyes) with a clinical diagnosis of PION. Co-morbid systemic diseases and visual function were recorded at both initial presentation and after mean visual follow-up of 4.1 years and systemic follow-up of 5.4 years.

RESULTS

PION occurred in three main settings: in the perioperative period following a variety of surgical procedures (28 patients), associated with giant cell (temporal) arteritis (6 patients), and associated with nonarteritic systemic vascular disease (38 patients). Patients with perioperative and arteritic PION were more likely to have severe, bilateral visual loss that did not improve. Among eyes with nonarteritic PION, 34% experienced improvement in vision, 28% remained stable, and 38% worsened. Among patients with nonarteritic PION, carotid artery disease and a history of stroke (with or without carotid artery disease) were both associated with a statistically significant increased risk of poor final visual outcome.

CONCLUSIONS

There are three distinct subtypes of PION: perioperative, arteritic, and nonarteritic. Patients with PION that is unassociated with surgery should undergo an evaluation for systemic vascular diseases, including giant cell arteritis, that may or may not be apparent at the time of vision loss. The visual prognosis for patients with perioperative or arteritic PION is poor, whereas that for nonarteritic PION is similar to that for patients with nonarteritic AION.

The blood supply of the optic nerve head and the evaluation of it - myth and reality

Evidence has gradually emerged that there is vascular insufficiency in the optic nerve head (ONH) in both anterior ischemic optic neuropathy (AION) and glaucomatous optic neuropathy (GON); thus both represent ischemic disorders of the ONH. Together these diseases constitute a major cause of blindness or seriously impaired vision in man. Consequently there has recently been great interest in the ONH circulation in health and disease and in how to evaluate it. Many studies of the subject have been published, with conflicting interpretations and claims. The basis of the inconsistent information seems to be confusion on some fundamental issues concerning the ONH circulation itself. The objective of this paper is to differentiate myths and misconceptions from reality about the ONH blood supply; to elucidate the reasons for disagreement on the blood supply of the ONH; and to evaluate the reliability and validity of various methods currently used to measure ONH blood flow.

Three Common Assumptions About Ocular Blood Flow and Glaucoma

Although substantial indirect evidence exists to link altered ocular blood flow to glaucoma, it must be remembered that the validity of investigations in this area depends on acceptance of three basic assumptions: 1) ischemia directly causes or increases the susceptibility of the optic nerve to glaucomatous damage; 2) optic nerve vascular anatomy and physiology allows identification of the critical vascular beds in optic nerve disease; and 3) current measurement techniques provide the ability to monitor important vascular beds. The hypotheses underlying these assumptions are examined.

Optic nerve blood flow in glaucoma

Vascular disorders of the anterior optic nerve, historically, have been described as potential etiologic factors in the development of glaucomatous optic neuropathy. During the past several decades, clinical and experimental evidence of the involvement of vascular aberrations as a potential causative factor or associated risk factor have increased. However, the direct evidence that optic nerve ischemia contributes to glaucomatous optic neuropathy remains limited. Several questions about our current knowledge arise. Can ischemia alone or in combination with other factors cause glaucomatous optic neuropathy? Does our current knowledge of the vascular anatomy and physiology of the optic nerve allow us to understand vascular changes observed in individuals with glaucoma? Can we rely on current measurement techniques to assess and monitor the vascular beds of the optic nerve? This article summarizes the complex nature of the microcirculation in the anterior optic nerve, discusses the possible contribution of vascular factors in the development of glaucoma optic neuropathy, and examines the measurement techniques used in current studies.

Morphological variations of the peripapillary circle of Zinn-Haller by flat section

AIMS

To evaluate the morphometric and morphological variations of the circle of Zinn-Haller (CZH) in the human eye.

METHODS

42 human enucleated eyes were used in this study. After transverse flat thick sections were cut through the optic nerve and adjacent sclera, tissue sections were stained with haematoxylin and eosin or examined immediately by wet preparation under a light microscope. The average vessel diameter of the arterial circle and the average distance between the optic nerve head (ONH) and the arterial circle were determined. Various branching patterns of the CZH were also evaluated.

RESULTS

The vessel diameter of the arterial circle was 123 (SD 75) microm (range 20-230 microm). The distance of the CZH from the ONH margin was 403 (352) microm (0-1050 microm). The CZH gave off branches to the optic nerve and to the peripapillary choroid (PPC) with various branching patterns especially at the entry point of paraoptic short posterior ciliary artery.

CONCLUSIONS

The CZH exists within a variable distance from the ONH and its average diameter is similar to that of the central retinal vessels though it shows marked variation even in the same circle. The CZH also shows variable configurations in branching patterns. These variations may act as contributing factors that are responsible for the individual susceptibility of the anterior optic nerve and the PPC to circulatory disturbances.