Pathogenesis of visual field defects. Role of the ciliary circulation

Optical Coherence Tomographic Optic Nerve Head Morphology in Myopia III: The Exposed Neural Canal Region in Healthy Eyes-Implications for High Myopia

PURPOSE

To determine the prevalence and magnitude of optical coherence tomography (OCT) exposed neural canal (ENC), externally oblique choroidal border tissue (EOCBT), and exposed scleral flange (ESF) regions in 362 non-highly myopic (spherical equivalent -6.00 to 5.75 diopters) eyes of 362 healthy subjects.

DESIGN

Cross-sectional study.

METHODS

After OCT optic nerve head (ONH) imaging, Bruch membrane opening (BMO), the anterior scleral canal opening (ASCO), and the scleral flange opening (SFO) were manually segmented. BMO, ASCO, and SFO points were projected to the BMO reference plane. The direction and magnitude of BMO/ASCO offset as well as the magnitude of ENC, EOCBT, and ESF was calculated within 30° sectors relative to the foveal-BMO axis. Hi-ESF eyes demonstrated an ESF ≥100 µm in at least 1 sector. Sectoral peri-neural canal choroidal thickness (pNC-CT) was measured and correlations between the magnitude of sectoral ESF and proportional pNC-CT were assessed.

RESULTS

Seventy-three Hi-ESF (20.2%) and 289 non-Hi-ESF eyes (79.8%) were identified. BMO/ASCO offset as well as ENC, EOCBT, and ESF prevalence and magnitude were greatest inferior temporally where the pNC-CT was thinnest. Among Hi-ESF eyes, the magnitude of each ENC region correlated with the BMO/ASCO offset magnitude, and the sectors with the longest ESF correlated with the sectors with proportionally thinnest pNC-CT.

CONCLUSIONS

ONH BMO/ASCO offset, either as a cause or result of ONH neural canal remodeling, corresponds with the sectoral location of maximum ESF and minimum pNC-CT in non-highly myopic eyes. Longitudinal studies to characterize the development and clinical implications of ENC Hi-ESF regions in non-highly myopic and highly myopic eyes are indicated.

Hyperbaric oxygen treatment of central retinal vein occlusion with cilioretinal artery occlusion secondary to hormonal treatment: Case report and review

INTRODUCTION

This report describes a case of central retinal vein occlusion (CRVO) and cilioretinal artery occlusion (CLRAO) after hormonal treatment for induction of ovulation that was successfully treated with hyperbaric oxygen.

CASE REPORT

A 48 year-old woman was admitted to our department for sudden blurred vision in her left eye. The patient had a history of 3-months hormonal treatment for induction of ovulation. The best corrected visual acuity was 7/10 (20/32) in the left eye and 10/10 (20/20) in the right eye. Fundus examination of the left eye revealed flame-shaped haemorrhages, whitening of the retina along the distribution of cilioretinal artery and tortuous retinal veins. Fluorescein angiography confirmed the combination of a non-ischaemic CRVO with CLRAO. The patient was treated with a 2 h session of hyperbaric oxygen at 253 kPa (2.5 atmospheres absolute) once daily for a total of 30 sessions. Best corrected visual acuity improved to 10/10 (20/20) in the left eye.

CONCLUSIONS

CRVO and CLRAO are both occlusive disorders. HBOT is a safe low-cost treatment modality that can be beneficial in some ocular pathologies. It can maintain oxygenation of the retina through the choroidal blood supply, decrease oedema and preserve compromised tissue adjacent to the ischaemic area.

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.

Effect of Choroidal Vessel Density on the Ellipsoid Zone and Visual Function in Retinitis Pigmentosa Using Optical Coherence Tomography Angiography

Purpose

We evaluate the effect of choroidal vessel density on the residual length of the ellipsoid zone (EZ) and visual function in patients with retinitis pigmentosa (RP) using optical coherence tomography angiography (OCTA).

Methods

Fifty-three patients with RP (n = 101 eyes) and 53 normal participants (n = 76 eyes) were enrolled in this study. Patients with RP were assigned to three groups according to their best-corrected visual acuity (BCVA). All patients underwent ophthalmologic examinations, including BCVA, fundus examination performed with a slit-lamp using an indirect 90 diopter (D) lens, OCTA, full-field electroretinogram (ERG), and visual field. The choroidal vessel density in the choriocapillaris-Sattler's layer (DC-S), Haller's layer (DH), horizontal length of the ellipsoid (HEL), and vertical length of the ellipsoid (VEL) were assessed using OCTA and Adobe Photoshop CS3 extended software.

Results

A significantly increasing impairment of choroidal vessel density (DC-S and DH) was characterized in the RP groups compared to those of the controls (P < 0.05 for all). The magnitude of the reduction in the DC-S and DH was much easier to identify for more severely impaired BCVA in the RP groups (P < 0.05 for all). The DC-S had the strongest correlation with the HEL, VEL, BCVA, visual field, and b-wave amplitude (r = 0.735, r = 0.753, r = -0.843, r = 0.579, and r = 0.671, respectively).

Conclusions

Using noninvasive OCTA, choroidal microcirculation, especially in the small/middle choroidal vessel layers, was a prominent factor affecting the EZ, visual acuity, visual field, and recordable ERG b-wave amplitude of patients with RP. This may provide new insights into the progress mechanism and treatment of RP.

SIGNIFICANT REDUCTION OF PERIPAPILLARY CHOROIDAL THICKNESS IN PATIENTS WITH UNILATERAL BRANCH RETINAL VEIN OCCLUSION

PURPOSE

To evaluate changes in peripapillary choroidal thickness in patients with branch retinal vein occlusion (BRVO) over 12 months, using spectral-domain optical coherence tomography with enhanced depth imaging.

METHODS

This retrospective, interventional case series included 20 treatment-naive patients with unilateral BRVO with at least 12 months follow-up. The peripapillary choroidal thickness was measured over 12 months.

RESULTS

In BRVO-affected eyes, the mean peripapillary choroidal thickness was 213.5 ± 51.7 μm (126.1[FIGURE DASH]326.9 μm) at baseline and 129.6 ± 39.3 μm (65.9[FIGURE DASH]197.1 μm) at 12 months. In nonaffected contralateral eyes, the mean peripapillary choroidal thickness was 194.1 ± 39.8 μm (158.5[FIGURE DASH]238.3 μm) at baseline and 156.6 ± 56.2 μm (125.9[FIGURE DASH]213.9 μm) at 12 months. The mean peripapillary choroidal thickness decreased significantly over 12 months in both BRVO-affected and nonaffected eyes (P < 0.001, both eyes). Although the mean peripapillary choroidal thickness was not significantly different between groups at baseline (P = 0.472), it was significantly lower in BRVO-affected eyes than in nonaffected eyes at 12 months (P = 0.036).

CONCLUSION

Peripapillary choroidal thickness decreased significantly over 12 months in BRVO-affected eyes and nonaffected eyes in patients with unilateral BRVO.

Paracentral acute middle maculopathy in nonischemic central retinal vein occlusion

PURPOSE

To better characterize a novel spectral-domain optical coherence tomography (OCT) presentation, termed paracentral acute middle maculopathy, to describe this finding in patients with nonischemic central retinal vein occlusion (CRVO), and to support a proposed pathogenesis of intermediate and deep retinal capillary ischemia.

DESIGN

Retrospective observational case series.

METHODS

Clinical histories, high-resolution digital color imaging, red-free photography, fluorescein angiography, near-infrared reflectance, and spectral-domain OCT images of 484 patients with acute CRVO from 2 centers were evaluated for the presence of coexisting paracentral acute middle maculopathy.

RESULTS

Of 484 patients diagnosed with CRVO, 25 (5.2%) demonstrated evidence of concurrent paracentral acute middle maculopathy. Patients averaged 51 years of age and presented with complaints of paracentral scotomas. All patients demonstrated hyper-reflective plaquelike lesions at the level of the inner nuclear layer by spectral-domain OCT and showed corresponding dark-gray lesions on near-infrared reflectance and perivenular deep retinal whitening on color fundus photography. There was no fluorescein angiographic correlate to these lesions. On follow-up spectral-domain OCT imaging, the lesions had resolved into areas of inner nuclear layer atrophy with persistence of scotomas.

CONCLUSIONS

Paracentral acute middle maculopathy refers to characteristic hyper-reflective spectral-domain OCT lesions involving the middle layers of the retina at the level of the inner nuclear layer that may develop in response to ischemia of the intermediate and deep capillary plexuses. This series is the largest to describe this spectral-domain OCT finding to date, and it is the first to associate it with nonischemic CRVO.

Ocular vascular occlusive disorders: natural history of visual outcome

Ocular vascular occlusive disorders collectively constitute the most common cause of visual disability. Before a disease can be managed, it is essential to understand its natural history, so as to be able to assess the likely effectiveness of any intervention. I investigated natural history of visual outcome in prospective studies of 386 eyes with non-arteritic anterior ischemic optic neuropathy (NA-AION), 16 eyes with non-arteritic posterior ischemic optic neuropathy, 697 eyes with central retinal vein occlusion (CRVO), 67 eyes with hemi-CRVO (HCRVO), 216 eyes with branch retinal vein occlusion (BRVO), 260 eyes with central retinal artery occlusion (CRAO), 151 eyes with branch retinal artery occlusion (BRAO) and 61 eyes with cilioretinal artery occlusion (CLRAO). My studies have shown that every one of these disorders consists of multiple distinct clinical sub-categories with different visual findings. When an ocular vascular occlusive disorder is caused by giant cell arteritis, which is an ophthalmic emergency, it would be unethical to do a natural history study of visual outcome in them, because in this case early diagnosis and immediate, intensive high-dose steroid therapy is essential to prevent any further visual loss, not only in the involved eye but also in the fellow, normal eye. In NA-AION in eyes seen ≤2 weeks after the onset, visual acuity (VA) improved in 41% of those with VA 20/70 or worse, and visual field (VF) improved in 26% of those with moderate to severe VF defect. In non-ischemic CRVO eyes with VA 20/70 or worse, VA improved in 47% and in ischemic CRVO in 23%; moderate to severe VF defect improved in 79% in non-ischemic CRVO and in 27% in ischemic CRVO. In HCRVO, overall findings demonstrated that initial VA and VF defect and the final visual outcome were different in non-ischemic from ischemic HCRVO - much better in the former than the latter. In major BRVO, in eyes with initial VA of 20/70 or worse, VA improved in 69%, and moderate to severe VF defect improved in 52%. In macular BRVO with 20/70 or worse initial VA, it improved in 53%, and initial minimal-mild VF defect was stable or improved in 85%. In various types of CRAO there are significant differences in both initial and final VA and VF defects. In CRAO eyes seen within 7 days of onset and initial VA of counting fingers or worse, VA improved in 82% with transient non-arteritic CRAO, 67% with non-arteritic CRAO with cilioretinal artery sparing, 22% with non-arteritic CRAO. Central VF improved in 39% of transient non-arteritic CRAO, 25% of non-arteritic CRAO with cilioretinal artery sparing and 21% of non-arteritic CRAO. Peripheral VF improved in non-arteritic CRAO in 39% and in transient non-arteritic CRAO in 39%. In transient CRAO, finally peripheral VFs were normal in 93%. In non-arteritic CRAO eyes initially 22% had normal peripheral VF and in the rest it improved in 39%. Final VA of 20/40 or better was seen in 89% of permanent BRAO, and in 100% of transient BRAO and non-arteritic CLRAO. In permanent BRAO eyes, among those seen within 7 days of onset, central VF defect improved in 47% and peripheral VF in 52%, and in transient BRAO central and peripheral VFs were normal at follow-up. My studies showed that AION, CRVO, BRVO, CRAO and BRAO, each consist of multiple distinct clinical sub-categories with different visual outcome. Contrary to the prevalent impression, these studies on the natural history of visual outcome have shown that there is a statistically significant spontaneous visual improvement in each category. The factors which influence the visual outcome in various ocular vascular occlusive disorders are discussed.

Perioperative visual loss after nonocular surgery

Although rare, a change in visual acuity after surgery for nonocular procedures has devastating consequences. Increased recognition and discussion of this complication is reported in recent literature, most notably following spinal and cardiac surgery. Various pathologies may be responsible for perioperative visual loss (POVL), including ischemic optic neuropathy, retinal vascular occlusion, and cortical blindness. Here we review the incidence of the problem, the anatomy and physiology of the ocular circulation, variants of POVL, and proposed predisposing factors. Potential perioperative methods to prevent this complication are discussed, and suggested treatment modalities are presented.

Acute retinal arterial occlusive disorders

The initial section deals with basic sciences; among the various topics briefly discussed are the anatomical features of ophthalmic, central retinal and cilioretinal arteries which may play a role in acute retinal arterial ischemic disorders. Crucial information required in the management of central retinal artery occlusion (CRAO) is the length of time the retina can survive following that. An experimental study shows that CRAO for 97min produces no detectable permanent retinal damage but there is a progressive ischemic damage thereafter, and by 4h the retina has suffered irreversible damage. In the clinical section, I discuss at length various controversies on acute retinal arterial ischemic disorders. Classification of acute retinal arterial ischemic disorders: These are of 4 types: CRAO, branch retinal artery occlusion (BRAO), cotton wool spots and amaurosis fugax. Both CRAO and BRAO further comprise multiple clinical entities. Contrary to the universal belief, pathogenetically, clinically and for management, CRAO is not one clinical entity but 4 distinct clinical entities - non-arteritic CRAO, non-arteritic CRAO with cilioretinal artery sparing, arteritic CRAO associated with giant cell arteritis (GCA) and transient non-arteritic CRAO. Similarly, BRAO comprises permanent BRAO, transient BRAO and cilioretinal artery occlusion (CLRAO), and the latter further consists of 3 distinct clinical entities - non-arteritic CLRAO alone, non-arteritic CLRAO associated with central retinal vein occlusion and arteritic CLRAO associated with GCA. Understanding these classifications is essential to comprehend fully various aspects of these disorders. Central retinal artery occlusion: The pathogeneses, clinical features and management of the various types of CRAO are discussed in detail. Contrary to the prevalent belief, spontaneous improvement in both visual acuity and visual fields does occur, mainly during the first 7 days. The incidence of spontaneous visual acuity improvement during the first 7 days differs significantly (p<0.001) among the 4 types of CRAO; among them, in eyes with initial visual acuity of counting finger or worse, visual acuity improved, remained stable or deteriorated in non-arteritic CRAO in 22%, 66% and 12% respectively; in non-arteritic CRAO with cilioretinal artery sparing in 67%, 33% and none respectively; and in transient non-arteritic CRAO in 82%, 18% and none respectively. Arteritic CRAO shows no change. Recent studies have shown that administration of local intra-arterial thrombolytic agent not only has no beneficial effect but also can be harmful. Prevalent multiple misconceptions on CRAO are discussed. Branch retinal artery occlusion: Pathogeneses, clinical features and management of various types of BRAO are discussed at length. The natural history of visual acuity outcome shows a final visual acuity of 20/40 or better in 89% of permanent BRAO cases, 100% of transient BRAO and 100% of non-arteritic CLRAO alone. Cotton wools spots: These are common, non-specific acute focal retinal ischemic lesions, seen in many retinopathies. Their pathogenesis and clinical features are discussed in detail. Amaurosis fugax: Its pathogenesis, clinical features and management are described.

Central retinal vein occlusion associated with cilioretinal artery occlusion

PURPOSE

To describe the clinical characteristics and pathogenesis of central retinal vein occlusion (CRVO) associated with cilioretinal artery occlusion (CLRAO).

METHODS

The study included 38 patients (38 eyes) who had CRVO associated with CLRAO and were seen in our clinic from 1974 to 1999. At their first visit to our clinic, all patients provided a detailed ophthalmic and medical history and underwent comprehensive ophthalmic evaluation, color fundus photography, and fluorescein fundus angiography. At each follow-up visit, the same ophthalmic evaluations were performed, except for fluorescein fundus angiography.

RESULTS

Of 38 eyes, 30 had nonischemic CRVO, 5 had ischemic CRVO, and 3 had nonischemic hemi-CRVO. Patients with nonischemic CRVO were significantly younger (mean age +/- SD: 45.3 +/- 16.0 years) than those with ischemic CRVO (72.3 +/- 9.2 years; P = 0.001) and those with nonischemic hemi-CRVO (64.7 +/- 7.5 years; P = 0.018). At least one third of the patients gave a definite history of episode(s) of transient visual blurring before the onset of constant blurred vision. Initially, the ophthalmoscopic and fluorescein angiographic findings were similar to those seen in CRVO and hemi-CRVO, except that all these eyes had retinal infarct in the distribution of the cilioretinal artery; its size and site varied widely. Fluorescein angiography typically showed only transient hemodynamic block and not the typical CLRAO. During follow-up, visual acuity improved markedly in nonischemic CRVO (P < 0.001) and nonischemic hemi-CRVO but deteriorated in ischemic CRVO. Retinopathy resolved spontaneously in 22 eyes with nonischemic CRVO (mean duration +/- SD: 42.0 +/- 101.0 months), in 2 eyes with ischemic CRVO (15.4 +/- 4.5 months), and in 1 eye with nonischemic hemi-CRVO. Retinociliary collaterals developed in 30% of eyes with nonischemic CRVO, in 40% of eyes with ischemic CRVO, and in 66% of eyes with nonischemic hemi-CRVO.

CONCLUSION

CRVO associated with CLRAO constitutes a distinct clinical entity. The pathogenesis of CLRAO in CRVO is due to transient hemodynamic blockage of the cilioretinal artery caused by a sudden sharp rise in intraluminal pressure in the retinal capillary bed (due to CRVO) above the level of that in the cilioretinal artery.

Alterations in the choroid in hypercholesterolemic rabbits: reversibility after normalization of cholesterol levels

Endothelial damage in atherosclerosis is characterized by abnormal vascular functionality. Hyperlipidemic patients show alterations in ocular vascularization. However, it is not known whether these alterations are reversible after the lipid profile returns to normal. This study evaluates a rabbit model of hypercholesterolemia, examining the ultrastructural changes in the choroid, and the changes in it after a period of normal blood-cholesterol values induced by a standard diet. Rabbits were divided into three groups: G0, fed a standard diet; G1A, fed a 0.5% cholesterol-enriched diet for 8 months; and G1B, fed a 0.5% cholesterol-enriched diet for 8 months followed by a standard diet for a further 6 months. Eyes were processed for transmission electron microscopy. G1A had a buildup of lipids at the suprachoroidea that compressed the vascular layers, and hypertrophy of endothelial and vascular smooth muscle cells. In G1B there was less lipid accumulation than in G1A, but this was not followed by reversal of the choroidal damage. The suprachoroidea thickness of G1B was still greater than in G0 due to abundant collagen fibers. The intervascular spaces of the choroid had fewer lipids than G1A but more collagen fibers than G0. The large- and medium-sized vessel layers and choriocapillaris were less compressed than in G1A but exhibited basal membrane and endothelial changes similar to those in G1A. Normalization of serum cholesterol levels is not enough to reverse cholesterol-induced vascular damage to the choroid. These choroidal changes could be compatible with a chronic ischemia that could produce retinal degeneration.

Central retinal artery occlusion: visual outcome

PURPOSE

To investigate systematically the natural history of visual outcome in central retinal artery occlusion (CRAO).

DESIGN

Cohort study.

METHODS

At entry, 244 consecutive patients (260 eyes) with CRAO (seen consecutively from 1973 to 2000) had a detailed ocular and medical history and ocular evaluation. CRAO eyes were classified into four categories: non-arteritic (NA) CRAO (171 eyes), NA-CRAO with cilioretinal artery sparing (35), transient NA-CRAO (41), and arteritic CRAO (13).

RESULTS

Within 7 days of onset of CRAO, initial visual acuity differed among the four CRAO types (P < .0001). In eyes with vision of counting fingers or worse, it improved in 82% of eyes with transient NA-CRAO, 67% of eyes with NA-CRAO with cilioretinal artery sparing, and 22% of eyes with NA-CRAO. Visual acuity improved primarily within the first 7 days (P < .0001). In the central 30-degree visual field, central scotoma was most common. Central visual field improved in 39% with transient NA-CRAO, 25% with NA-CRAO with cilioretinal artery sparing, and 21% with NA-CRAO. Peripheral visual field was normal in 62.9% of eyes with transient NA-CRAO and 22.1% in those with NA-CRAO. In 51.9% of eyes with NA-CRAO, the only remaining visual field was a peripheral island. Peripheral fields improved in NA-CRAO (39%) and in transient NA-CRAO (39%).

CONCLUSIONS

Classification of CRAO is crucial for understanding differences in visual outcome. Marked improvement in visual acuity and visual field can occur without treatment and is determined by several factors. Visual field information is essential to evaluate visual disability in CRAO.

Posterior ischaemic optic neuropathy: clinical features, pathogenesis, and management

PURPOSE

To investigate and present a comprehensive account of the clinical features, pathogenesis, and management of posterior ischaemic optic neuropathy (PION).

METHODS

This retrospective study is based on 53 consecutive eyes of 42 patients with PION seen in my clinic since 1973, who fulfilled the inclusion criteria. They were systematically evaluated, treated, and followed by me. All patients had initially detailed ophthalmic evaluation of the anterior and posterior segments, including visual field with Goldmann perimeter and fluorescein fundus angiography. All patients aged 50 years and older were also investigated for giant cell arteritis (GCA). Every attempt was made to rule out other causes of visual loss. Follow-up evaluation was similar to the initial evaluation except angiography. Aetiologically, PION can be divided into three types: arteritic due to GCA, nonarteritic not due to GCA, and surgical following a surgical procedure. Steroid therapy was given to only those nonarteritic PION patients who opted to try that, but was given to all arteritic PION patients.

RESULTS

PION was nonarteritic in 28 patients (35 eyes), arteritic in 12 (14 eyes), and surgical in three (four eyes). Visual acuity varied between 20/20 and no light perception--it was count fingers or less in 19 of 35 eyes with nonarteritic PION, four of 14 in arteritic, and all four with surgical PION. The most common visual field defect was central visual loss, alone or in combination with other types of visual field defects. Initially, optic disc and fundus showed no abnormality but the disc usually developed pallor in about 6-8 weeks. Aggressive treatment with high-dose systemic steroid during the very early stages of nonarteritic PION produced significant improvement of visual acuity as well as visual fields, but not so in arteritic or surgical PION. However, some spontaneous visual improvement also occurred in some untreated nonarteritic PION cases.

CONCLUSIONS

PION is a distinct clinical entity but should be diagnosed only after exclusion of all other causes of visual loss. In all patients older than 50, GCA must be ruled out. There is usually marked visual loss, with central field defect being the most common. The study suggests that high-dose steroid therapy in nonarteritic PION, soon after the onset of visual loss, resulted in significant visual improvement compared to the untreated cases, but not in arteritic and surgical PION.

Morphometric changes of the choriocapillaris and the choroidal vasculature in eyes with advanced glaucomatous changes

PURPOSE

In addition to an elevated intraocular pressure a compromise of the ocular blood supply have been implicated in the pathogenesis of primary open-angle glaucoma. The purpose of this study was to quantify morphologic changes in the choroid including choriocapillaris thickness and density and diameter of large choroidal vessels in post mortem eyes with advanced primary open-angle glaucoma.

METHODS

We analyzed 20 eye bank eyes (provided from the Georgia Eye Bank in Atlanta) with end stage primary open-angle glaucoma and compared them with 20 age-matched control eye bank eyes. The eyes were processed for light microscopy and following variables were measured with a digital filar micrometer: density and diameter of large choroidal vessels in the macular and equatorial choroid; thickness of the choroid in the macular and equatorial region; density and thickness of choriocapillaris in the macular, peripapillary, and equatorial choroid; and peripapillary capillary-free area nasal and temporal to the optic disk.

RESULTS

Eyes with glaucoma displayed a lower density of the capillaries of the choriocapillaris as compared to control eyes in the macular, temporal peripapillary, and equatorial choroid with 0.50-0.55 (p=0.018), 0.46-0.51 (p=0.016), and 0.50-0.55 (p=0.038), respectively. There was no significant difference for the choriocapillaris density in the nasal peripapillary choroid, the thickness of the capillaries of the choriocapillaris in all assessed locations, and the nasal and temporal peripapillary capillary-free zone of the choriocapillaris between eyes with glaucomatous damage and controls. Assessment of large choroidal vessels in the macular choroid showed that eyes with glaucoma had a decreased density of veins (11.7-38.9 mm(-2); p<0.001) and arteries (7.7-12.4 mm(-2); p=0.005) and arteries with a higher diameter (45.6-28.2 microm; p<0.001) as compared to control eyes. The large vessels in the equatorial choroid displayed no significant difference in diameter but a lower density (21.2-44.1 mm(-2); p=0.017) in eyes with glaucomatous damage as compared to controls.

CONCLUSION

Eyes with advanced glaucomatous damage after long standing primary open-angle glaucoma exhibit several changes including decreased density of capillaries of the choriocapillaris and decreased density of large choroidal vessels. We cannot conclude from our study whether the observed vascular changes in the choroid are primary pathogenic factors or secondary phenomena.

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.

Blood flow in the optic nerve head and factors that may influence it

In the recent past there has been great interest in the blood supply of the optic nerve head (ONH), how to evaluate ONH blood flow, and what factors influence it, in health and disease. This is because evidence has progressively accumulated that there is vascular insufficiency in the ONH in both anterior ischemic optic neuropathy (AION) and glaucomatous optic neuropathy (GON)-two major causes of blindness or of seriously impaired vision in man. For the management and prevention of visual loss in these two disorders, a proper understanding of the factors that influence the blood flow in the ONH is essential. The objective of this paper is, therefore, to review and discuss all these factors. The various factors that influence the vascular resistance, mean blood pressure and intraocular pressure are discussed, to create a better basic understanding of the ONH blood flow, which may help us toward a logical strategy for prevention and management of ischemic disorders of the ONH.

Laser Doppler flowmetry and optic nerve head blood flow

PURPOSE

Ischemic disorders of the optic nerve head constitute an important cause of visual loss. The optic nerve head is supplied by two main sources of blood flow: the superficial layers by the central retinal artery and the deeper layers by the posterior ciliary arteries. This study was conducted in rhesus monkey eyes to obtain a better understanding of which part of the optic nerve head circulation is measured by laser Doppler flowmetry.

METHODS

By means of a fundus camera-based laser Doppler flowmetry technique to measure blood flow in the optic nerve head tissue, laser Doppler flowmetry measurements were taken at baseline and then after experimental occlusion of central retinal artery (12 eyes), posterior ciliary arteries (nine eyes), and combined occlusion of central retinal artery and posterior ciliary arteries (nine eyes). Optic nerve head, choroidal, and retinal circulations were investigated by fluorescein fundus angiography after the various arterial occlusions.

RESULTS

Average laser Doppler flowmetry flow during central retinal artery occlusion alone was significantly decreased (P<.001) by 39%+/-21% (mean +/- 95% confidence interval) compared with normal baseline. Combined occlusion of central retinal artery and posterior ciliary arteries reduced laser Doppler flowmetry flow even more markedly by 57%+/-27% (P<.0005), but the difference between this flow reduction and that with central retinal artery occlusion alone was not significant (P>.20). After posterior ciliary artery occlusion alone, however, measurements showed a nonsignificant increase in laser Doppler flowmetry flow of 17%+/-37%.

CONCLUSIONS

The findings of this study suggest that the standard laser Doppler flowmetry technique is predominantly sensitive to blood flow changes in the superficial layers of the optic nerve head and less sensitive to those in the prelaminar and deeper regions, and their relative proportions are not known. In this laser Doppler flowmetry technique, the weaker Doppler signal from the deep layers cannot be separated from the dominant signal from the superficial layers to exclusively study the circulation in the deep layers; the latter circulation is of interest in optic nerve head ischemic disorders, including glaucoma. Emerging new optical modalities of the laser Doppler flowmetry technique may help in selectively measuring blood flow in the deeper layers.

Retrobulbar haemodynamic changes studied by colour Doppler imaging in glaucoma

PURPOSE

To determine the effect of spontaneously elevated intraocular pressure (IOP) on the ocular circulation, and evaluate the result of IOP-lowering procedures in terms of haemodynamics.

METHODS

Colour Doppler imaging (CDI) was employed to determine the peak systolic velocity (PSV), end-diastolic velocity (EDV) and time average maximal velocity (TAMV), as well as the Pourcelot ratio (PR) and pulsatility index (PI), of the central retinal artery (CRA), posterior ciliary arteries (PCA) and ophthalmic artery. Various CDI parameters of the eyes with elevated IOP were compared with those of the clinically healthy fellow eyes and the control eyes, separately. Also, data from CDI of glaucoma eyes obtained during the period of elevated IOP and then following IOP-lowering procedures were compared, deliberately avoiding the influence of glaucoma medications.

RESULTS

Eyes (n = 12) with elevated IOP showed significantly decreased flow velocities of the CRA and significantly increased PR and PI of the nasal and temporal PCA, compared with the fellow and control eyes, respectively. Following IOP-lowering procedures, the PR and PI of the nasal PCA decreased significantly.

CONCLUSION

Spontaneously elevated IOP may induce haemodynamic changes in the CRA and PCA, but no significant change is identified in the ophthalmic artery. Flow velocities tend to decrease while the resistance indices tend to increase with elevated IOP. Such haemodynamic changes may reverse following normalisation of IOP.

Open-angle glaucoma and ocular hypertension: the Long Island Glaucoma Case-control Study

This case-control study evaluated risk factors for open-angle glaucoma (OAG) and high intraocular pressure (IOP), including systemic hypertension and its treatment, other systemic factors, familial, and demographic variables. The three study groups were based on masked ophthalmologic gradings of visual fields and fundus photographs, as well as tonometry. The OAG group (n = 122) had OAG field defects, IOP > 21 mmHG, and cup-disc ratios > or = 0.5 and/or evidence of glaucoma disc damage. The ocular hypertensives (n = 108) had no field defects, IOP > 21 mmHg and normal discs. The controls (n = 190) had no field defects, IOP < 21 mmHg and normal discs. The data collection protocol included a standardized interview and measurements. Medical history was confirmed by contacting the primary care physicians (89% response from physicians). Study groups were compared by polychotomous logistic regression analyses. Men were more likely to have OAG and less likely to have ocular hypertension. Systemic hypertension was more frequent in ocular hypertensives (Odds Ratio = 2.36); high diastolic pressure was associated with OAG and ocular hypertension (OR = 2.13 and 2.21, respectively). Treatment for systemic hypertension was unrelated to OAG risk. Low perfusion pressures (blood pressure-IOP differences) were strongly associated with OAG and ocular hypertension, a finding that could be due to the high IOP in these groups. A family history of glaucoma was more frequent in OAG (OR = 3.08) and ocular hypertension (OR = 2.38) than in controls. Alcohol consumption was related to ocular hypertension (OR = 2.32). No other associations were significant. The results confirm an association of blood pressure with intraocular pressure. Since the OAG and ocular hypertensive groups had similar blood pressure results, an independent effect of blood pressure on OAG was not substantiated.

The 1994 Von Sallman Lecture. The optic nerve head circulation in health and disease

This is a brief overview of multifaceted anatomical, experimental and clinical studies conducted by the author since 1955 on the optic nerve head circulation in health and disease. Conclusions, based on the accumulated information provided by these studies, are summarized. The studies on the pattern of blood supply of the optic nerve head have shown that: (a) its main source of blood supply is the posterior ciliary artery circulation, with retinal circulation supplying only the surface nerve fiber layer, (b) there is marked interindividual variation in the blood supply pattern, and (c) the blood supply in the optic nerve head has a sectorial distribution. The various factors which produce interindividual variation in the blood supply of the optic nerve head are discussed, particularly those in the posterior ciliary artery circulation; this is because all available evidence indicates that it is derangement in the posterior ciliary circulation in the optic nerve head that is primarily responsible for the common ischemic disorders of the optic nerve head, e.g. anterior ischemic optic neuropathy and glaucomatous optic neuropathy. Factors that may derange the blood flow in the optic nerve head include defective autoregulation of blood flow in it, vascular changes in its feeding arteries, hematologic abnormalities, systemic arterial hypertension and hypotension, and intraocular pressure; their roles are discussed. For better understanding and management of optic nerve head ischemic disorders, there is an urgent need for an accurate clinical method of assessment of blood flow in the posterior ciliary circulation in optic nerve head, since no satisfactory method is currently available. Redness or pallor of the optic disk on ophthalmoscopy is not a true guide to the optic nerve head vascularity as it gives no information about the state of the posterior ciliary circulation. Fluorescein fundus angiography, though far superior to the optic disk color for evaluation of optic nerve head vascularity, has a number of limitations. All these topics and various controversies about them are discussed briefly.

Effects of high intraocular pressure on the glucose metabolism in the retina and optic nerve in old atherosclerotic monkeys

BACKGROUND

There are reasons to suspect that in patients with high intraocular pressure and glaucoma, there is underperfusion of the intraocular tissues and optic nerve head, leading to tissue hypoxia and neuronal damage. Studies in young, healthy monkeys have demonstrated that there is efficient autoregulation of the blood flow, and essentially normal glucose consumption, even at very high intraocular pressures that reduce the perfusion pressure to levels around 30 mm Hg. It seemed likely that the conditions might be different in old monkeys that had been on atherogenic diet for long periods of time and that such monkeys were a better model for glaucomatous patients.

METHODS

The perfusion pressure in one eye was reduced to 30-35 mmHg in four old rhesus monkeys that had been on atherogenic diet for 12.5 years, and the glucose consumption in the eyes and optic nerves was studied with the 14C-2-deoxyglucose (2DG) method of Sokoloff et al.

RESULTS

There was enhanced uptake of 2DG in the inner as well as outer parts of the retina and in the optic nerve head in all four monkeys studied, indicating compromised supply of oxygen resulting in anaerobic glycolysis.

CONCLUSION

Old monkeys that have been on atherogenic diet seem more susceptible to elevation of the intraocular pressure than young, healthy monkeys, thereby suggesting defective autoregulation in them. Such differences in susceptibility may play a role also in the development of ischemic disorders of the optic nerve head and glaucomatous optic neuropathy.

Mechanisms of optic nerve damage in primary open angle glaucoma

Several mechanisms have been postulated to explain the optic nerve damage that occurs in primary open angle glaucoma (POAG). No single mechanism can adequately explain the great variations in susceptibility to damage and the patterns of damage seen in this syndrome. The etiology of POAG is likely to be multifactorial. Mechanical, vascular and other factors may influence individual susceptibility to optic nerve damage. An enhanced understanding of the nature of the optic nerve damage in POAG and improved methods of study may result in earlier diagnosis or may allow us to distinguish among different pathological processes all currently grouped under the diagnosis of POAG. As we gain a better understanding of the neuropharmacology and cellular biology of injury and repair of the visual system we will undoubtedly refine the concepts of glaucomatous optic neuropathy.

Color Doppler imaging: methodology and preliminary results in glaucoma

Color Doppler imaging (CDI) has recently been applied to investigation of the normal vascular anatomy of the eye and orbit as well as a variety of conditions in which vascular abnormalities are important. Combining B-scan ultrasonography and Doppler waveform analysis, CDI enables noninvasive serial examination of blood velocity and vascular resistance from the ophthalmic, short posterior, ciliary and central retinal arteries. This technology is being used to study the ophthalmic circulation of patients with primary open-angle or normotension glaucoma.

Apparent cleavage of the retinal nerve fiber layer in asymptomatic eyes with high myopia

The appearance of the retinal nerve fiber layer was studied in one eye of 203 normal Asians (59 with high myopia greater than or equal to -5 D, and 144 with emmetropia or hyperopia). "Cleavage" of the retinal nerve fiber layer was observed in 3 of these 59 highly myopic eyes, but there was no significant damage to either the retinal pigment epithelium or the choroid. In contrast, no cleavage was observed in the other 144 emmetropic or hyperopic eyes. High myopia (P = 0.0237, Fisher's exact test) was a significant risk factor for "cleavage" development in the retinal nerve fiber layer. The occurrence of a defect (nerve fiber loss) in the retinal nerve fiber layer in severe myopia (5/59, 8%) was also greater than that in either emmetropia or hyperopia (2/144, 1%; P = 0.0229). These results indicate that subtle changes can occur in the appearance of the retinal nerve fiber layer of the eye in some patients with asymptomatic myopia.

In vivo choroidal circulation and its watershed zones

In vivo studies on choroidal vascular bed have shown that the posterior ciliary arteries (PCAs) right down to their terminal arterioles in the choroid have strictly segmental blood flow and they behave as end-arteries. These studies totally contradict the picture shown by all the postmortem cast studies of the choroidal vascular bed as a freely communicating system. The in vivo pattern helps to explain the typically localised nature of inflammatory, ischaemic, degenerative and metastatic nature of the choroidal lesions. Like other end-arterial vascular systems in the body, the choroidal vascular bed has watershed zones situated between the various PCAs, the short PCAs, the choroidal arteries, the arterioles, and the vortex veins. The end-arterial nature of the choroidal vasculature and the existence of watershed zones in the choroid are of great clinical importance; their role in the production of various ischaemic lesions in the choroid, anterior ischaemic optic neuropathy (AION) and other ischaemic disorders of the optic nerve head is discussed.

Anterior ischaemic optic neuropathy. Differentiation of arteritic from non-arteritic type and its management

Anterior ischaemic optic neuropathy (AION), a common, visually crippling disorder, is discussed, with particular emphasis on differentiating AION due to giant cell arteritis (arteritic AION) from that not due to it (non-arteritic AION). Giant cell arteritis is an ophthalmic emergency because of imminent danger of bilateral total blindness, which is almost always preventable if the disease is quickly identified and treated urgently and aggressively. My studies have revealed that the best means of differentiating arteritic from non-arteritic AION is a combination of information from the following: systemic and visual symptoms of giant cell arteritis, high erythrocyte sedimentation rate and C-reactive protein, early massive visual loss, chalky-white optic disc swelling, associated cilio-retinal artery occlusion, massive non-filling of the choroid on fluorescein fundus angiography and temporal artery biopsy. Management of giant cell arteritis and of arteritic AION is discussed. Current misconceptions about AION are pointed out.

Ocular vasospasm: a risk factor in the pathogenesis of low-tension glaucoma

The typical morphological and consequent functional damage caused by disease entities covered by the term 'glaucoma' is the result of inadequate circulation to the optic nerve fibres, predominantly in the papillary region, as a result of elevated intraocular pressure. The aim of this study is classification of different forms of glaucoma on the basis of blood flow parameters. Physiological and pathophysiological aspects of ocular blood flow and of microcirculation and hemorrheology will be considered and the significance of ocular vasospasm in low-tension glaucoma discussed. The frequent occurrence of vasospasm in the nailfold capillaries and of visual field deterioration after a cold-water test demonstrates that vasospasm is an expression of different underlying phenomena. Our results show that, in patients with ocular vasospasm, treatment with a calcium antagonist brings about a clear reversal of their visual field defects.

Anterior ischemic optic neuropathy: classification of field defects by Octopus automated static perimetry

Visual fields of patients with anterior ischemic optic neuropathy (AION) were classified according to quantitative criteria, using the Octopus perimeter. Although a significant altitudinal pattern of field loss was found in 55% of perimetric examinations, the "spared" hemifields routinely showed some loss of sensitivity. This finding, along with the diffuse loss of sensitivity in a high percentage of visual fields, indicates more extensive involvement of the circulation of the anterior optic nerve head than has previously been suggested. Furthermore, patients with diabetes mellitus alone were found to have a statistically separable pattern of visual field loss. The pathophysiologic implications of the visual fields in AION and their relationship to the clinical findings were investigated.

Changing concepts of primary open-angle glaucoma and early detection

The understanding of primary open-angle glaucoma has changed over the past 20 years and recommendations on early detection are being revised. In this paper the use of Shiotz tonometry is critically examined, and the problems encountered in instituting alternative screening techniques are reviewed.

Anterior ischaemic optic neuropathy. A correlative clinical and visual evoked potential study of 18 patients

The clinical and visual evoked potential (VEP) findings were analysed in 18 patients with anterior ischaemic optic neuropathy. The VEP studies showed a variety of abnormalities which could be interpreted as being the result of subcomponent interaction consequent upon loss or attenuation of the normal macular-derived P100 component. Delay of normal VEP subcomponents was not seen. The VEP findings were non-specific but pointed to a severe disturbance of transmission in optic nerve fibres subserving central vision. No significant changes were observed with time in most cases indicating a static monophasic process with no significant recovery.

Inferior altitudinal hemianopia associated with a tumor in the posterior fossa: report of a case

Altitudinal hemianopias may be related to chiasmatic involvement. A case in which horizontal inferior hemianopia is associated with a tumor in the posterior fossa producing a triventricular hydrocephalus is described. The visual field defect is interpreted as a consequence of the pressure by a dilated third ventricle upon the chiasmatic area.

Central retinal artery obstruction and visual acuity

The records of 72 patients (73 eyes) with acute central retinal arterial obstruction (CRAO) were reviewed. Three eyes (4%) were initially observed to have no light perception vision. However, two of these three were found to have concomitant posterior ciliary circulation defects on fluorescein angiography, and the third had electroretinographic evidence of both outer and inner retinal damage. Previous studies have indicated that a much higher percentage of patients with CRAO present with NLP vision. From the data presented it is the feeling of the authors that cases with obstruction of the central retinal artery alone and NLP acuity in the involved eye are most unusual. If true NLP vision is present, additional complicating factors should be suspected, particularly abnormalities of the choroidal circulation and the optic nerve.

Glaucomatouslike visual field defects in chronic papilledema

In 19 patients, 31 eyes with chronic papilledema were found to have visual field defects other than enlarged blind spots. In this series, the inferior nasal quadrant was most frequently involved. Dense paracentral scotomata were found in the Bjerrum area, some of which later progressed to form ring scotomata. Visual acuity usually deteriorated late in the course of the disease. The similarities of visual field defects in papilledema and glaucoma suggest common pathogenetic mechanisms of nerve fiber atrophy in both diseases.

Glaucomatous cupping -- sine glaucoma

A 72-year-old man presented with transient episodes of gradually descending vision loss in either eye. Both discs showed marked cupping, but applanation tensions were normal. Carotid occlusions were present. The etiology of the transient visual disturbances, the relationship of carotid disease to low tension glaucoma, and the management of such patients are discussed.

Infarction of the optic nerve head in children with accelerated hypertension

Four cases of anterior ischaemic optic neuropathy occurred in children with accelerated hypertension. The cause may have been a sudden relative fall in arterial pressure which reduced the perfusion of the optic disc, whose circulation was compromised by long-standing hypertensive vascular disease.