Optic nerve compression by carotid arteries in low-tension glaucoma

Dolichoectatic arterial compression of the chiasm and optic nerve: a case report

Dolichoectatic arterial compression of the anterior visual pathway is a rare but recognized condition. The functional impact, however, is still less clear. We describe a case of a 56-year-old male with diminished visual acuity in the left eye and incongruent inferior visual defect in both eyes caused by dolichoectasia due to a congenital hypoplasia of one horizontal segment of the circle of Willis and subsequent arterial compression of the chiasm and left optic nerve.

Glaucomatous Type Cupping Caused by Internal Carotid Artery Compression: a Case Report

A 71-year-old woman with a diagnosis of normal tension glaucoma (NTG) presented with complains of progressive visual loss in the right eye. Examination revealed features consistent with compressive optic neuropathy. Although brain magnetic resonance imaging (MRI) was initially interpreted as normal, re-evaluation disclosed a compression on the right optic nerve from the right internal carotid artery. We highlight the clinical differential diagnosis between NTG and compressive optic neuropathy. This case is a reminder that a compressive optic neuropathy may be caused by anatomical variation of normal intracranial structures.

Optic Disc Cupping Due to Dolichoectatic Internal Carotid Artery Optic Nerve Compression

BACKGROUND

To determine whether significant compression of the optic nerve by the internal carotid artery (ICA) can produce an optic neuropathy with optic disc cupping that resembles glaucoma in patients without elevated intraocular pressure (IOP).

METHODS

This was a retrospective case series of patients referred to neuro-ophthalmology for a possible nonglaucomatous optic neuropathy. Patients were included in the study if they had preserved visual acuity, optic disc-related visual field defects, optic nerve cupping, IOP less than 21 mm Hg, open angles, and unequivocal radiological compression of the ipsilateral optic nerve by an intracranial blood vessel.

RESULTS

Three patients were included with a mean age of 56.3 (range 29-82) years. Patient 1 was a 58-year-old man incidentally noted to have left optic nerve cupping on a routine examination. He had an inferior arcuate defect and the left prechiasmatic optic nerve was elevated and compressed by a tortuous left ICA. Patient 2 was a 29-year-old man with a normal-tension glaucoma (NTG) diagnosis for 7 years in the right eye treated with latanoprost. He had a superior greater than inferior arcuate defect and there was vascular compression of the optic nerve between the supraclinoid ICA and A1 segment of the anterior cerebral artery. Patient 3 was an 82-year-old woman with an NTG diagnosis for 10 years who had progression of her visual field defects despite low IOPs. MRI showed mass effect on the right optic nerve by a dolichoectatic right supraclinoid ICA.

CONCLUSIONS

Significant compression of the optic nerve by a normal, tortuous, or dolichoectatic ICA may result in an optic neuropathy with optic disc cupping that resembles glaucoma.

[Clinical evaluation of the optic disc in glaucoma]

BACKGROUND

Glaucoma is defined as a progressive neuropathy of the optic nerve, characterized by specific changes of the optic disc, parapapillary region, and retinal nerve fiber layer.

OBJECTIVES

Characteristic glaucomatous changes of the optic disc, parapapillary region, and retinal nerve fiber layer are discussed and their ophthalmoscopic examination is described.

MATERIALS AND METHODS

A literature search in the PubMed database was conducted.

RESULTS

A systematic step-by-step approach to a qualitative and quantitative ophthalmoscopic evaluation of the optic disc regarding glaucomatous damage is presented.

CONCLUSION

A systematic, clinical, qualitative, and quantitative assessment of the optic disc can be performed with little effort and forms the basis for diagnosis and treatment of glaucoma.

Indications for a systemic work-up in glaucoma

Most glaucomas are primary in nature. However, many adult and childhood glaucomas are secondary, and they require systemic evaluation to pick up associated systemic disease. Conditions such as nocturnal hypotension and sleep apnea may contribute to glaucomatous progression, whereas neurologic diseases may mimic normal tension glaucoma based on disc appearance. This review highlights those conditions in which a focused systemic work-up can improve glaucoma management and potentially discover life-threatening disease.

Differentiation of compressive from glaucomatous optic neuropathy with spectral-domain optical coherence tomography

PURPOSE

To compare optic disc topography in eyes with compressive optic neuropathy (CON) and open-angle glaucoma (OAG) using spectral-domain (SD) optical coherence tomography (OCT) and Heidelberg retinal tomograph (HRT) (Heidelberg Engineering GmbH, Heidelberg, Germany).

DESIGN

Cross-sectional, observational study.

PARTICIPANTS

A total of 200 eyes from 123 patients with CON (69 eyes) or OAG (58 eyes) and controls (73 eyes).

METHODS

Univariate and multivariate analyses of HRT parameters, SD-OCT circumpapillary retinal nerve fiber layer (RNFL) thickness, and optic nerve head (ONH) parameters.

MAIN OUTCOME MEASURES

Circumpapillary RNFL, OCT ONH parameters, and HRT parameters.

RESULTS

The univariate analysis of OCT parameters demonstrated significant differences between the temporal and nasal quadrants; clock hours 3 (55 vs. 73 μm), 4, 8 (93.9 vs. 70.7 μm), 9, and 10; vertical cup-to-disc ratio (C:D) (0.6 vs. 0.8) and cup volume (0.2 vs. 0.5) (P<0.001) between patients with CON and OAG, respectively. The CON discs were significantly different from normal discs for all OCT parameters except cup volume. The CON discs were not significantly different from normal discs for HRT parameters, except for mean RNFL thickness and cup shape measure. The OAG discs were significantly different from normal discs in all HRT and OCT parameters (P<0.001). Multivariate analysis demonstrated that the OCT 3 o'clock temporal sector, average C:D ratio, vertical C:D ratio, and cup volume measurements were able to differentiate OAG from CON.

CONCLUSIONS

Compressive optic neuropathy is associated with significantly thinner nasal and temporal sectors compared with OAG, whereas OAG results in larger cups and cup volume with OCT measurements. The Heidelberg retinal tomograph is not able to differentiate CON from normal discs.

Glaucoma-like optic neuropathy in patients with intracranial tumours

PURPOSE

To examine frequency and associated factors of glaucoma-like appearance of the optic nerve head in patients with intrasellar, suprasellar or parasellar tumours.

METHODS

This retrospective clinical observational study included patients who were consecutively treated for intrasellar tumours (n = 143), suprasellar tumours (n = 321), parasellar tumours (n = 36) or retrosellar tumour (n = 1), and all of whom had undergone fundus photography and full-threshold visual field examination. The tumour spectrum included 336 pituitary gland tumours, 32 meningiomas, 89 craniopharyngiomas, 9 chiasmal gliomas and 35 other types of tumours or lesions. An age-matched control group was formed from the population-based Beijing Eye Study. Using fundus photographs and visual field examinations, glaucoma was defined by a neuroretinal rim shape not following the ISNT rule (Disc glaucoma group) and by an abnormal rim shape plus glaucoma-like visual field defects (Field glaucoma group). Type and size of the tumours were assessed on neuroradiological images.

RESULTS

Five-hundred and one patients fulfilled the inclusion criteria. Disc glaucoma and Field glaucoma were detected significantly more frequently in the study population [34 (6.8%) patients and 31 (6.3%) patients, respectively] than in the population-based control group of the same ethnicity (1.3% ± 0.5%; p < 0.001). In multivariate analysis, presence of Disc glaucoma [odds ratio (OR) = 2.64; p = 0.016] and presence of Field glaucoma (OR = 3.01; p = 0.027) were significantly associated with tumour location [suprasellar > parasellar > intrasellar]. The same held true for tumour width (OR = 1.08; p = 0.002; and OR = 1.08; p = 0.003, respectively).

CONCLUSIONS

Large perisellar tumours were associated with a glaucoma-like appearance of the optic nerve head in eyes. It may diagnostically and pathogenetically be of importance.

Corneal thickness measurements in normal-tension glaucoma workups: is it worth the effort?

PURPOSE

To correlate central corneal thickness (CCT) and intraocular pressure (IOP) with disease severity in normal-tension glaucoma (NTG) patients.

METHODS

We conducted a retrospective review of all patients diagnosed with NTG in our institution between 2002 and 2006. NTG was diagnosed according to the glaucomatous visual fields loss, glaucomatous optic disc cupping, and an IOP <22 mm Hg on diurnal curve measurements. Mean CCT and IOP values before and after treatment were also evaluated. Patients were divided into 3 groups according to advanced glaucoma intervention score (mild, moderate, and severe visual field defects).

RESULTS

A total of 33 females and 35 males with bilateral NTG were enrolled. The mean follow-up was 4.6 years. CCT was inversely correlated with glaucoma severity. CCT was normal in both eyes in mild disease, thin in the right eye (RE) and normal in the left eye (LE) in moderate disease, and low in both eyes in severe disease. Initial bilateral mean maximal IOP was similar at all disease stages and became lower after treatment in parallel to disease severity: 13.44, 12.22, and 11.63 mm Hg in the RE and 13.29, 12.60, and 12.32 mm Hg in the LE, respectively. There was no statistical difference in disease severity between the RE and LE.

CONCLUSIONS

CCT correlated with disease severity: the more advanced the disease, the thinner the cornea. Initial maximal IOP did not predict disease severity, but it was lower in the more severe cases after treatment, possibly representing a more aggressive treatment protocol.

Optic nerve compression by normal carotid artery in patients with normal tension glaucoma

AIM

To determine whether compression of the optic nerve by the intracranial carotid artery (ICA) can be a causative factor of normal tension glaucoma (NTG).

METHODS

The medical records of 103 eyes of 54 Japanese patients with NTG and 104 eyes of 52 age matched control patients were reviewed. The neuroradiological findings of magnetic resonance images (MRI) were evaluated to determine the relation between the optic nerve and ICA. The clinical characteristics and general medical conditions, such as diabetes and systemic hypertension, were also compared between the two groups.

RESULTS

The prevalence of optic nerve compression by the ICA in patients with NTG was 49.5%, which was significantly higher than that in control group with 34.6% (p = 0.035). Bilateral compression of the optic nerve was detected in 22 patients with NTG (40.7%), and this was also significantly higher (p = 0.029) than that in the control group (11 patients, 21.2%). In the NTG group, eyes with cup/disc ratio (C/D ratio) > or =0.7 showed a higher percentage of compression (52.6%) compared with eyes with C/D ratio of <0.7 (12.5%; p = 0. 042). The presence of diabetes and hypertension did not affect the incidence of optic nerve compression by ICA significantly.

CONCLUSIONS

The significantly higher percentage of NTG patients who had optic nerve compression by the ICA suggests that compression of the optic nerve by ICA may be a possible causative factor or a risk factor for optic nerve damage in some patients with NTG.

Is normal tension glaucoma actually an unrecognized hereditary optic neuropathy? New evidence from genetic analysis

Normal tension glaucoma and dominant optic atrophy share many overlapping clinical features, and differentiating between these two diseases is often difficult. The gene responsible for dominant optic atrophy is the OPA1 gene located on chromosome 3. This gene encodes for a protein product that is involved in mitochondrial metabolic function. Recent genetic linkage analysis of patients with normal tension glaucoma has shown an association with polymorphisms of the OPA1 gene. This association suggests that normal tension glaucoma may actually be a hereditary optic neuropathy with a pathophysiology based in mitochondrial dysfunction.

Neuroradiologic screening in normal-pressure glaucoma: study results and literature review

PURPOSE

To determine if there was an increased prevalence of intracranial compressive lesions in patients with clinically diagnosed normal-pressure glaucoma compared with a group of patients with progressive primary open-angle glaucoma.

PATIENTS AND METHODS

In a prospective, comparative, observational case series, the authors performed cranial magnetic resonance imaging in patients with consecutively diagnosed normal-pressure glaucoma (n = 62) and progressive primary open-angle glaucoma with controlled intraocular pressures (n = 70). The prevalence of intracranial compressive lesions, demographic data, and clinical characteristics were compared between both groups.

RESULTS

Four of the 62 (6.5%) patients with normal-pressure glaucoma had clinically relevant intracranial compressive lesions involving the anterior visual pathway, compared with none of the 70 patients with primary open-angle glaucoma (P = 0.039).

CONCLUSIONS

Intracranial compressive lesions are an important diagnostic consideration in the workup of normal-pressure glaucoma.

Nonglaucomatous cupping of the optic disc

Optic disc cupping is a consequence of myriad disorders. The anatomy and vasculature of the disc provide great insight into why, how, and when ODC occurs in various conditions. Approaches to distinguish glaucomatous from nonglaucomatous causes of ODC should rely on patient history, visual fields assessment, and funduscopic findings, as described. Cupping can be seen with neurological processes, including benign tumors, that are treatable. The clinician must remain vigilant to detect uncommon but potentially threatening forms of nonglaucomatous optic disc cupping.

Carotid artery ectasia coexistent with primary open angle glaucoma

A 60-year-old smoker presented with high intraocular pressure in the right eye with a right afferent pupil defect and visual field suggestive of primary open angle glaucoma in the right eye only, when an examination 2 years earlier had revealed no hint of ocular pathology. Radiological investigations demonstrated prominent ectasia of the internal carotid arteries extending into the proximal middle cerebral arteries. The changes in the carotids extended throughout the cavernous sinus regions, encroached on the under surface of the optic chiasm and were closely related to the internal aspects of both optic canals. In primary open angle glaucoma management, neural imaging is not normally recommended; however, neural imaging investigations should be considered if the presentation is not typical of a chronic bilateral optic neuropathy

Prolapsing gyrus rectus as a cause of progressive optic neuropathy

The pathogenesis of optic neuropathy caused by neurovascular compression or by similar mechanisms is unclear. Thin-slice magnetic resonance (MR) imaging was performed in 69 patients with optic neuropathy without demonstrable ophthalmological lesions (57.0 +/- 17.1 years of age) and 102 normal subjects (57.7 +/- 13.9 years of age). The MR imaging features were classified into "no compression" by the internal carotid artery (ICA), "compression" by the ICA, "no contact" with the anterior cerebral artery (ACA) or the gyrus rectus, "contact" with either or both, "compression" by the ACA, and "compression" by the gyrus rectus. The Spearman correlation coefficients were calculated between patients or controls, the MR classification, and the age, and the number of patients in each MR classification were evaluated by the chi 2 test. Five of the 69 patients with rapidly progressive symptoms were operated on via the frontotemporal approach. The MR imaging feature of "compression" by the gyrus rectus was the best predictor of optic neuropathy (Spearman correlation coefficients rho = -0.23646, p < 0.0018). This MR imaging feature was observed in 38 of 69 patients and in 32 of 102 controls (p = 0.002). Compression of the nerve by the gyrus rectus or the ACA was confirmed in all five operated cases. Decompression of the nerve was fully achieved in four of the five patients, and their symptoms have not progressed since then. Optic neuropathies due to compression by the prolapsing gyrus rectus are not well understood. Such neuropathies may be detected by MR imaging.

Symptomatic compression of the optic nerve by the carotid artery: clinical profile of 18 patients with 24 affected eyes identified by magnetic resonance imaging

OBJECTIVE

To characterize the clinical features and course of patients with magnetic resonance imaging (MRI)-defined optic nerve compression by the supraclinoid carotid artery.

DESIGN

Retrospective, observational case series.

PARTICIPANTS

Eighteen patients with 24 affected eyes were identified by reviewing case records from the author's referral-based neuro-ophthalmology practice. Predetermined inclusion and exclusion criteria were applied to potential participants.

MAIN OUTCOME MEASURES

The following variables were abstracted from the medical record: age, gender, presenting symptoms, past medical problems, visual acuity, color vision, visual field, pupillary reactions, optic disc appearance, other neurologic signs, and previously documented and follow-up examinations.

RESULTS

There were eight women and ten men ranging in age from 28 to 86 years (median age, 72 years) at the time of diagnosis. Ten (56%) of 18 patients had hypertension. Twelve patients had unilateral optic neuropathy, whereas 6 patients had bilateral optic neuropathy. One patient presented with subacute superior orbital fissure syndrome due to mass effect of a dolichoectatic carotid artery. Another patient had oculomotor nerve palsy with signs of aberrant regeneration due to intracavernous mass effect of a dolichoectatic carotid artery. One patient had a bitemporal hemianopia associated with bilateral compression of the immediate prechiasmatic optic nerves by dolichoectatic carotid arteries. The predominant pattern of visual field loss in most patients reflected nerve fiber bundle injury. A central scotoma or absolute central visual field loss was noted in only 6 (25%) of 24 affected eyes. Most patients demonstrated saucerlike excavation of the optic disc. Progression of visual acuity loss occurred at a relatively slow rate.

CONCLUSIONS

Although uncommon, intracranial compression of the optic nerve by the carotid artery should be considered in a patient with unexplained or progressive unilateral or bilateral optic neuropathy. This entity can be diagnosed using clinical skills to exclude more common causes of optic nerve injury and coronal-oriented MRI to confirm anatomic compression of the symptomatic optic nerve. Although many affected patients have excavation of the optic disc and nerve fiber bundle visual field defects, most have additional signs atypical for glaucoma, minimizing the potential for diagnostic confusion between the two disorders.

Glaucomatous versus nonglaucomatous optic disc cupping: clinical differentiation

Cupping of the optic nerve head associated with normal intraocular pressure (IOP) is a common clinical presentation for which clearly defined management guidelines have not been established. The clinical approach represents a diagnostic challenge because the mechanism of optic nerve injury is often difficult to objectively establish. Of paramount importance is the primary distinction between physiologic cupping and pathologic cupping, and the accurate subclassification of eyes with pathologic cupping. Therefore, it is essential for clinicians to differentiate glaucomatous from nonglaucomatous disc damage. This article reviews the clinical differentiation of eyes with glaucomatous and nonglaucomatous optic disc cupping.

The cupped disc. Who needs neuroimaging?

OBJECTIVE

To determine the incidence of positive neuroradiologic studies in consecutive patients with glaucoma associated with normal intraocular pressure and to compare the psychophysical and clinical characteristics of these eyes with eyes with disc cupping associated with intracranial masses.

DESIGN

Retrospective case-controlled study.

PARTICIPANTS

Fifty-two eyes of 29 patients with glaucoma associated with normal intraocular pressure and 44 eyes of 28 control patients with compressive lesions were reviewed.

INTERVENTION

The medical records of consecutive glaucoma patients with normal intraocular pressure who underwent brain magnetic resonance imaging or computed tomography scanning as part of a diagnostic evaluation between January 1, 1985, and July 1, 1995, were reviewed. A masked reading of optic nerve photographs and visual fields was performed by one observer. A similar analysis was performed on a control group of consecutive patients with nonglaucomatous optic nerve cupping with known intracranial mass lesions.

MAIN OUTCOME MEASURES

The neuroradiologic findings, clinical characteristics, optic nerve head appearance, and patterns of visual field loss were compared between groups.

RESULTS

None of the patients diagnosed with glaucoma had neuroradiologic evidence of a mass lesion involving the anterior visual pathway. Compared to control subjects, patients with glaucoma were older (P = 0.0001), had better visual acuity (P = 0.002), greater vertical loss of neuroretinal rim tissue (P = 0.0001), more frequent optic disc hemorrhages (P = 0.01), less neuroretinal rim pallor (P = 0.0001), and more nerve fiber bundle visual field defects aligned at the horizontal midline (P = 0.0001). Visual acuity less than 20/40, vertically aligned visual field defects, optic nerve pallor in excess of cupping, and age younger than 50 years were 77%, 81%, 90%, and 93% specific for nonglaucomatous cupping associated with compressive lesions, respectively.

CONCLUSIONS

Anterior visual pathway compression is an uncommon finding in the neuroradiologic evaluation of patients with a presumptive diagnosis of normal-tension glaucoma. Younger age, lower levels of visual acuity, vertically aligned visual field defects, and neuroretinal rim pallor may increase the likelihood of identifying an intracranial mass lesion.

Optic nerve contact and compression by the carotid artery in asymptomatic patients

PURPOSE

To estimate the frequency and clinical correlates of contact and compression of the intracranial optic nerve by the supraclinoid carotid artery in asymptomatic patients.

METHODS

In a retrospective study, we identified asymptomatic patients who had undergone magnetic resonance imaging with sequences that could be used to evaluate the relation between the intracranial optic nerve and the carotid artery. These patients underwent neuroimaging evaluations for reasons unrelated to loss of vision, optic neuropathy, or carotid artery disorders. The relation between the optic nerve and carotid artery was graded in a standardized manner. The effect of a number of clinical covariates on the risk of compression was evaluated using multiple logistic regression.

RESULTS

The frequencies of some of the artery-nerve relationships included contact of one or both optic nerves in 70 (70%) of 100 patients; bilateral compression in 12 (12%) of 100 patients; and unilateral compression with no arterial contact or compression on the opposite side in five (5%) of 100 patients. The estimated odds of compression were significantly increased as the diameter of the carotid artery increased.

CONCLUSIONS

Among asymptomatic patients, supraclinoid carotid artery contact with the intracranial optic nerve occurs frequently. Anatomic compression, on the other hand, especially when unilateral, occurs infrequently. The risk of anatomic compression of the optic nerve is directly proportional to the diameter of the carotid artery.

Intracranial arterial calcification and ectasia in visual failure

Calcification of the major intracranial arteries is frequently observed on computed tomography (CT), particularly in the carotid siphon, and has been implicated as a causative factor in low tension glaucoma. Ectasia of the carotid siphon has also been postulated as a possible cause of compressive optic neuropathy. 153 patients, in whom high resolution CT of the orbits and parasellar region had been performed for suspected anterior visual pathway pathology, were retrospectively reviewed. The presence and severity of calcification and ectasia of the major intracranial arteries was recorded. There was a high occurrence of carotid siphon calcification, increasing with age, and independent of sex or race. Calcification was very rare in anterior cerebral, middle cerebral and basilar arteries in all age groups. The amount and degree of ectasia also increased with advancing age, and was more frequently observed in carotid and basilar than anterior and middle cerebral arteries. There was no correlation between the degree of calcification or ectasia and ophthalmological or neurological deficit.

Magnetic resonance imaging in patients with unexplained optic neuropathy

PURPOSE

To investigate the anatomic relation between the optic nerve and the adjacent intracranial internal carotid artery (ICA) in patients with unexplained optic neuropathy.

METHODS

Coronal magnetic resonance images (MRIs) of 20 patients with unexplained optic neuropathy and 20 age-matched controls were evaluated with digitizing software.

RESULTS

The distance between the optic nerve and ICA was significantly less on the side ipsilateral to the atrophic optic nerve than either the study group's contralateral optic nerve-ICA distance (P<0.001) or the control group's optic nerve-ICA distance (P<0.001). The diameter of the atrophic optic nerves was significantly less than either the diameter of the study group's contralateral normal nerves (P=0.008) or the control group's nerves (P<0.001). There was no significant difference between the diameters of the ICA flow voids adjacent to the atrophic optic nerves versus either the study group's contralateral ICA flow voids (P=0.91) or the control group's ICA flow voids (P=0.74).

CONCLUSIONS

The authors speculate that the intimate relation between the optic nerve and adjacent ICA may be important in the development of unexplained optic neuropathy. The ICA need not appear abnormal in MRIs.