Ischemic optic neuropathy (ION) is the loss of structure and function of a portion of the
optic nerve
In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i ...
due to obstruction of blood flow to the nerve (i.e.
ischemia
Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems ...
). Ischemic forms of
optic neuropathy
Optic neuropathy is damage to the optic nerve from any cause. The optic nerve is a bundle of millions of fibers in the retina that sends visual signals to the brain.
Damage and death of these nerve cells, or neurons, leads to characteristic featu ...
are typically classified as either
anterior ischemic optic neuropathy
Anterior ischemic optic neuropathy (AION) is a medical condition involving loss of vision caused by damage to the anterior portion of the optic nerve as a result of insufficient blood supply (ischemia). This form of ischemic optic neuropathy ...
or
posterior ischemic optic neuropathy according to the part of the optic nerve that is affected. People affected will often complain of a loss of
visual acuity
Visual acuity (VA) commonly refers to the clarity of visual perception, vision, but technically rates an animal's ability to recognize small details with precision. Visual acuity depends on optical and neural factors. Optical factors of the eye ...
and a
visual field
The visual field is "that portion of space in which objects are visible at the same moment during steady fixation of the gaze in one direction"; in ophthalmology and neurology the emphasis is mostly on the structure inside the visual field and it i ...
, the latter of which is usually in the superior or inferior field.
When ION occurs in patients below the age of 50 years old, other causes should be considered, such as
juvenile diabetes mellitus,
antiphospholipid antibody-associated
clotting disorders, collagen-vascular disease, and
migraines
Migraine (, ) is a complex neurological disorder characterized by episodes of moderate-to-severe headache, most often unilateral and generally associated with nausea, and light and sound sensitivity. Other characterizing symptoms may includ ...
. Rarely, complications of
intraocular surgery or acute
blood loss
Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, v ...
may cause an ischemic event in the optic nerve.
Presentation
Anterior ION presents with sudden, painless
visual loss
Visual or vision impairment (VI or VIP) is the partial or total inability of visual perception. In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment, visual impairment may cause the individual difficul ...
, developing over hours to days.
[
]
Diagnosis
Examination findings usually include decreased visual acuity, a visual field defect, color vision
Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different frequencies independently of light intensity.
Color perception is a part of the larger visual system and is mediated by a co ...
loss, a relative afferent pupillary defect, and a swollen optic nerve head. Posterior ION occurs arteritic, nonarteritic, and surgical settings. It is characterized by acute vision loss without initial disc edema
Edema (American English), also spelled oedema (British English), and also known as fluid retention, swelling, dropsy and hydropsy, is the build-up of fluid in the body's tissue (biology), tissue. Most commonly, the legs or arms are affected. S ...
, but with subsequent optic disc atrophy.["Chapter 7: Ischemic Optic Neuropathy." Walsh and Hoyt's Clinical Neuro-ophthalmology. Ed. Neil R. Miller, Frank Burton Walsh, and William Fletcher Hoyt. Illustrated ed. Vol. 1. N.p.: Lippincott Williams & Wilkins, 2005. N. pag. Print.]
Management
Although there is no recognized treatment that can reverse the visual loss, upon recent reports, optic nerve health decompression may be beneficial for a select group of patients with a gradual decline in vision due to ION.[Oria, Veronica. "Ischemic Optic Neuropathy: Abstract." Seminars in Neurology. By Monica Rodriguez Fontal, John B. Kerrison, and Reinaldo Garcia. N.p.: Thieme, 2007. N. pag. Print.]
See also
* Ocular ischemic syndrome
References
* ''Dictionary of Eye Terminology'', Triad Publishing Company, 1990.
{{Eye pathology
Disorders of optic nerve and visual pathways