Progression of asymptomatic optic disc swelling to non-arteritic anterior ischaemic optic neuropathy

Non-Arteritic Anterior Ischemic Optic Neuropathy (NA-AION): A Comprehensive Overview

Non-arteritic anterior ischemic optic neuropathy (NA-AION) represents one of the most important causes of blindness or severely impaired vision in middle-aged and elderly people. Unilateral optic disc edema and abrupt, painless vision loss are its defining features. It is commonly assumed that NA-AION is caused by an ischemic infarction of the optic nerve head, and, although the exact pathogenesis is still unknown, several risk factors and comorbidities associated with its development have been found. NA-AION occurs generally in patients older than 50 years who have small optic discs and vasculopathy risk factors. Even though numerous treatment options have been proposed, no available effective medical or surgical therapy or prophylactic measure for NA-AION currently exists. The purpose of present-day therapeutic strategies is therefore to identify and possibly control any underlying modifiable risk factors, aiming to prevent the development of new NA-AION episodes in the affected and fellow eye. A thorough assessment of NAION, including its history, epidemiology, etiology, pathophysiology, risk factors, associated comorbidities, clinical findings, diagnostic tests, treatment choices, prognosis, and future research, is the goal of this work.

Non-Arteritic Anterior Ischemic Optic Neuropathy (NA-AION): A Comprehensive Overview

Non-arteritic anterior ischemic optic neuropathy (NA-AION) represents one of the most important causes of blindness or severely impaired vision in middle-aged and elderly people. Unilateral optic disc edema and abrupt, painless vision loss are its defining features. It is commonly assumed that NA-AION is caused by an ischemic infarction of the optic nerve head, and, although the exact pathogenesis is still unknown, several risk factors and comorbidities associated with its development have been found. NA-AION occurs generally in patients older than 50 years who have small optic discs and vasculopathy risk factors. Even though numerous treatment options have been proposed, no available effective medical or surgical therapy or prophylactic measure for NA-AION currently exists. The purpose of present-day therapeutic strategies is therefore to identify and possibly control any underlying modifiable risk factors, aiming to prevent the development of new NA-AION episodes in the affected and fellow eye. A thorough assessment of NAION, including its history, epidemiology, etiology, pathophysiology, risk factors, associated comorbidities, clinical findings, diagnostic tests, treatment choices, prognosis, and future research, is the goal of this work.

Approach to patient with unilateral optic disc edema and normal visual function

In patients with swollen optic nerve head and normal visual function, optic disc drusen (ODD) is the most common diagnosis. The best tests for detecting ODD are funds autofluorescence and enhanced-depth imaging ocular coherence tomography (EDIOCT). After ODD has been ruled out, asymmetric papilledema should be assumed to be the cause and MRI of the brain and orbits with contrast and venography should be performed in all patients. It allows one to look for indirect signs of increased inctracranial pressure (ICP), optic perineuritis, and other inflammatory or compressive processes affecting optic nerve or its sheath such as optic nerve sheath meningioma. If imaging signs of raised ICP are present, lumbar puncture should be performed with measurement of opening pressure and analysis of cerebrospinal fluid (CSF) contents in all patients with fever, meningismus or neurologic deficits as well as patients who are not in the typical demographic group for idiopathic intracranial hypertension (IIH). Optic nerve sheath enhancement on MRI should prompt work-up for causes of optic perineuritis. When the appropriate neuroimaging is normal, the differential diagnosis is limited and ophthalmological consultation is necessary to determine whether other subtle ocular abnormalities are present on biomicroscopic and dilated fundus examination.

Choroidal Thickness in Acute Non-arteritic Anterior Ischemic Optic Neuropathy

Purpose

To compare the choroidal thickness in eyes with acute non-arteritic anterior ischemic optic neuropathy (NAION) with healthy contralateral eye and normal controls.

Methods

Thirty-eight eyes with NAION, thirty-eight unaffected fellow eyes, and seventy-four eyes from 37 healthy, age- and sex-matched subjects were included in this prospective comparative case-control study. Choroidal thickness was measured by enhanced depth imaging (EDI) of spectral domain optical coherence tomography (SD-OCT). Peripapillary choroidal thickness (PCT) was measured at 1000 and 1500 μm from Bruch's membrane opening (BMO). Subfoveal choroidal thickness (SFCT) was measured in central subfoveal area, and 500 microns apart in temporal and nasal sides. Choroidal thickness among NAION eyes, uninvolved fellow eyes, and control eyes were compared.

Results

The mean of PCT at 1000 μm was significantly thicker in NAION and fellow eyes compared to control eyes (169.7 ± 47, 154.4 ± 42.1, and 127.7 ± 49.9 μm, respectively, P< 0.001 and P = 0.42). The mean PCT at 1500 μm was also significantly thicker in NAION and fellow eyes compared to control eyes (178.6 ± 52.8, 162.6 ± 46.1, and 135.1 ± 59 μm, respectively, P = 0.007 and P = 0.048). The mean PCT at 1000 and 1500 μm was significantly greater in NAION compared to fellow eyes (P = 0.027 and P = 0.035, respectively). The mean of SFCT was significantly thicker in NAION compared to control eyes (P = 0.032); however, there was no significant difference between uninvolved fellow and control eyes (P = 0.248).

Conclusion

Thicker choroidal thickness in acute NAION and uninvolved fellow eyes compared to normal eyes suggests a primary choroidal role in NAION pathophysiology.

Ischemic Optic Neuropathy

PURPOSE OF REVIEW

Vision is often threatened or lost by acute ischemic damage to the optic nerves. Such pathology most often affects the anterior portion of the nerve and is visible on funduscopic examination. Ischemic optic neuropathy is associated with typical vascular risk factors and with one systemic disease in particular: giant cell arteritis (GCA). This article provides an overview of the three major classes of ischemic optic neuropathy, including information on risk factors, differential diagnosis, evaluation, and management.

RECENT FINDINGS

Optical coherence tomography provides precise anatomic imaging in ischemic optic neuropathy, showing neural loss weeks before it is visible on examination. Refinements of optical coherence tomography reveal optic nerve microvasculature and may assist in understanding pathogenesis and verifying diagnosis. New diagnostic algorithms and cranial vascular imaging techniques help define the likelihood of GCA in patients with ischemic optic neuropathy. Finally, intraocular drug and biological agent delivery holds promise for nonarteritic ischemic optic neuropathy, whereas newer immunologic agents may provide effective steroid-sparing treatment for GCA.

SUMMARY

It is essential to recognize ischemic optic neuropathy upon presentation, especially to determine the likelihood of GCA and the need for immediate steroid therapy. A broad differential diagnosis should be considered so as not to miss alternative treatable pathology, especially in cases with retrobulbar optic nerve involvement.

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.

Nonarteritic Anterior Ischemic Optic Neuropathy Induced Retinal Folds and Deformations

Purpose

We hypothesized that the edema/swelling in the retina due to acute nonarteritic anterior ischemic optic neuropathy (NAION) can induce retinal folds (RF). We determined the pattern and frequency of folds in NAION at presentation and in follow-up, and the relationship between folds and a number of functional and structural parameters over time.

Methods

We prospectively studied eyes with acute NAION by spectral-domain optic coherence tomography (SD-OCT). We used transaxial and en face views to evaluate the presence of peripapillary fluid (PPF), peripapillary wrinkles (PPW), RF, choroidal folds (CF), creases, macular edema, and vitreous traction on the optic disc. Retinal deformations were correlated with the retinal nerve fiber layer (RNFL) thickness, logMAR visual acuity (VA) and mean deviation (MD).

Results

At presentation, 60 eyes had mean RNFL = 224 ± 75 μm, no vitreous traction, and similar VA and MD regardless of the retinal deformation or macular edema. There was PPF in 73%, PPW in 57%, RF in 38%, creases in 20%, and macular edema in 18% of eyes, and no CF. Eyes with retinal deformations had significantly greater RNFL thickness (P< 0.026). At 1 to 2 months, 49 eyes had reduction of the RNFL (112 ± 40 μm, P = 0.001) and unchanged VA and MD that did not correlate with fewer eyes having PPF (15%, P = 0.001), PPW (10%, P = 0.001), RF (10%, P = 0.001), creases (17%), and macular edema (0%, P = 0.007).

Conclusions

RF in NAION reflect stresses and strains due to extracellular fluid without increased pressure in the retrolaminar tissue and subarachnoid space, seen with papilledema. In NAION, the deformations and their resolution do not correlate with vision loss.