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With respect to embolic and hemodynamic causes, this transient monocular visual loss ultimately occurs due to a temporary reduction in retinal artery, ophthalmic artery, or ciliary artery blood flow, leading to a decrease in retinal circulation which, in turn, causes retinal hypoxia. While, most commonly, emboli causing amaurosis fugax are described as coming from an atherosclerotic carotid artery, any emboli arising from vasculature preceding the retinal artery, ophthalmic artery, or ciliary arteries may cause this transient monocular blindness.
- Atherosclerotic carotid artery: Amaurosis fugax may present as a type of transient ischemic attack (TIA), during which an embolus unilaterally obstructs the lumen of the retinal artery or ophthalmic artery, causing a decrease in blood flow to the ipsilateral retina. The most common source of these athero-emboli is an atherosclerotic carotid artery. However, a severely atherosclerotic carotid artery may also cause amaurosis fugax due to its stenosis of blood flow, leading to ischemia when the retina is exposed to bright light. "Unilateral visual loss in bright light may indicate ipsilateral carotid artery occlusive disease and may reflect the inability of borderline circulation to sustain the increased retinal metabolic activity associated with exposure to bright light."
- Atherosclerotic ophthalmic artery: Will present similarly to an atherosclerotic internal carotid artery.
- Cardiac emboli: Thrombotic emboli arising from the heart may also cause luminal obstruction of the retinal, ophthalmic, and/or ciliary arteries, causing decreased blood flow to the ipsilateral retina; examples being those arising due to (1) atrial fibrillation, (2) valvular abnormalities including post-rheumatic valvular disease, mitral valve prolapse, and a bicuspid aortic valve, and (3) atrial myxomas.
- Temporary vasospasm leading to decreased blood flow can be a cause of amaurosis fugax. Generally, these episodes are brief, lasting no longer than five minutes, and have been associated with exercise. These vasospastic episodes are not restricted to young and healthy individuals. "Observations suggest that a systemic hemodynamic challenge provoke[s] the release of vasospastic substance in the retinal vasculature of one eye."
- Giant cell arteritis: Giant cell arteritis can result in granulomatous inflammation within the central retinal artery and posterior ciliary arteries of eye, resulting in partial or complete occlusion, leading to decreased blood flow manifesting as amaurosis fugax. Commonly, amaurosis fugax caused by giant cell arteritis may be associated with jaw claudication and headache. However, it is also not uncommon for these patients to have no other symptoms. One comprehensive review found a two to nineteen percent incidence of amaurosis fugax among these patients.
- Systemic lupus erythematosus
- Periarteritis nodosa
- Eosinophilic vasculitis
- Hyperviscosity syndrome
- Polycythemia
- Hypercoagulability
- Protein C deficiency
- Antiphospholipid antibodies
- Anticardiolipin antibodies
- Lupus anticoagulant
- Thrombocytosis
- Subclavian steal syndrome
- Malignant hypertension can cause ischemia of the optic nerve head leading to transient monocular visual loss.
- Drug abuse-related intravascular emboli
- Iatrogenic: Amaurosis fugax can present as a complication following carotid endarterectomy, carotid angiography, cardiac catheterization, and cardiac bypass.
Ocular causes include:
- Iritis
- Keratitis
- Blepharitis
- Optic disc drusen
- Posterior vitreous detachment
- Closed-angle glaucoma
- Transient elevation of intraocular pressure
- Intraocular hemorrhage
- Coloboma
- Myopia
- Orbital hemangioma
- Orbital osteoma
- Keratoconjunctivitis sicca
Severe ipsilateral or bilateral carotid artery stenosis or occlusion is the most common cause of ocular ischemic syndrome. The syndrome has been associated with occlusion of the common carotid artery, internal carotid artery, and less frequently the external carotid artery. Other causes include:
- Takayasu's arteritis
- Giant cell arteritis
- Severe ophthalmic artery occlusion, due to thromboembolism.
- Surgical interruption of anterior ciliary blood vessels supplying the eye, particularly during extensive strabismus surgery on 3 or more rectus muscles, leading to an anterior segment ischemic syndrome.
This condition can also occur in ruminants suffering from a vitamin B (thiamine) deficiency due to thiamine-related cerebrocortical necrosis (CCN).
Those experiencing amaurosis are usually advised to consult a physician immediately as any form of vision loss, even if temporary, is a symptom that may indicate the presence of a serious ocular or systemic problem.
If carotid occlusive disease results in ophthalmic artery occlusion, general ocular ischemia may result in retinal neovascularization, rubeosis iridis, cells and flare, iris necrosis, and cataract. The condition leads to neovascularization in various eye tissues due to the ischemia. The eye pressure may become high due to associated neovascular glaucoma. An ischemic optic neuropathy may eventually occur.
Vitamin A supplementation plays an important role, specifically vitamin A deficiency is a top causes of preventable childhood blindness. Though in measles cases, the administration of the vitamin to offset visual impairment has not been proven effective, as of yet.
Of these, cataract is responsible for >65%, or more than 22 million cases of blindness, and glaucoma is responsible for 6 million cases.
Cataracts: is the congenital and pediatric pathology that describes the greying or opacity of the crystalline lens, which is most commonly caused by intrauterine infections, metabolic disorders, and genetically transmitted syndromes. Cataracts are the leading cause of child and adult blindness that doubles in prevalence with every ten years after the age of 40. Consequently, today cataracts are more common among adults than in children. That is, people face higher chances of developing cataracts as they age. Nonetheless, cataracts tend to have a greater financial and emotional toll upon children as they must undergo expensive diagnosis, long term rehabilitation, and visual assistance. Also, according to the Saudi Journal for Health Sciences, sometimes patients experience irreversible amblyopia after pediatric cataract surgery because the cataracts prevented the normal maturation of vision prior to operation. Despite the great progress in treatment, cataracts remain a global problem in both economically developed and developing countries. At present, with the variant outcomes as well as the unequal access to cataract surgery, the best way to reduce the risk of developing cataracts is to avoid smoking and extensive exposure to sun light (i.e. UV-B rays).
The most common causes of visual impairment globally in 2010 were:
1. Refractive error (42%)
2. cataract (33%)
3. glaucoma (2%)
4. age related macular degeneration (1%)
5. corneal opacification (1%)
6. diabetic retinopathy (1%)
7. childhood blindness
8. trachoma (1%)
9. undetermined (18%)
The most common causes of blindness in 2010 were:
1. cataracts (51%)
2. glaucoma (8%)
3. age related macular degeneration (5%)
4. corneal opacification (4%)
5. childhood blindness (4%)
6. refractive errors (3%)
7. trachoma (3%)
8. diabetic retinopathy (1%)
9. undetermined (21%)
About 90% of people who are visually impaired live in the developing world. Age-related macular degeneration, glaucoma, and diabetic retinopathy are the leading causes of blindness in the developed world.
Among working age adults who are newly blind in England and Wales the most common causes in 2010 were:
1. Hereditary retinal disorders (20.2%)
2. Diabetic retinopathy (14.4%)
3. Optic atrophy (14.1%)
4. Glaucoma (5.9%)
5. Congenital abnormalities (5.1%)
6. Disorders of the visual cortex (4.1%)
7. Cerebrovascular disease (3.2%)
8. Degeneration of the macula and posterior pole (3.0%)
9. Myopia (2.8%)
10. Corneal disorders (2.6%)
11. Malignant neoplasms of the brain and nervous system (1.5%)
12. Retinal detachment (1.4%)
The number of children who suffer from blindness worldwide is approximately 1.4 million. 75% of the world’s blind children live in Africa and Asia. A 2014 review indicated that an estimated of 238,500 children with bilateral blindness (rate 1.2/1,000) in the Eastern Mediterranean region.
Genetic tests and related research are currently being performed at Centogene AG in Rostock, Germany; John and Marcia Carver Nonprofit Genetic Testing Laboratory in Iowa City, IA; GENESIS Center for Medical Genetics in Poznan, Poland; Miraca Genetics Laboratories in Houston, TX; Asper Biotech in Tartu, Estonia; CGC Genetics in Porto, Portugal; CEN4GEN Institute for Genomics and Molecular Diagnostics in Edmonton, Canada; and Reference Laboratory Genetics - Barcelona, Spain.
Nystagmus is a relatively common clinical condition, affecting one in several thousand people. A survey conducted in Oxfordshire, United Kingdom found that by the age of two, one in every 670 children had manifested nystagmus. Authors of another study in the United Kingdom estimated an incidence of 24 in 10,000 (~0.240 %), noting an apparently higher rate amongst white Europeans than in individuals of Asian origin.
It is usually autosomal recessive; however, importantly for family planning, it is sometimes autosomal dominant. It is a disorder thought to be caused by abnormal development of photoreceptor cells.
OMIM currently recognizes 18 types of LCA.
The gene has been associated with Joubert syndrome, as well as type 10 LCA.
Although there is a lack of robust studies demonstrating the efficacy of lifestyle changes in preventing TIA, many medical professionals recommend them. These include:
- Avoiding smoking
- Cutting down on fats to help reduce the amount of plaque build up
- Eating a healthy diet including plenty of fruits and vegetables
- Limiting sodium in the diet, thereby reducing blood pressure
- Exercising regularly
- Moderating intake of alcohol, stimulants, sympathomimetics, etc.
- Maintaining a healthy weight
In addition, it is important to control any underlying medical conditions that may increase the risk of stroke or TIA, including:
- Hypertension
- High cholesterol
- Diabetes mellitus
- Atrial fibrillation
By definition, TIAs are transient, self-resolving, and do not cause permanent impairment. However, they are associated with an increased risk of subsequent ischemic strokes, which can be permanently disabling. Therefore, management centers around the prevention of future ischemic strokes and addressing any modifiable risk factors. The optimal regimen depends on the underlying cause of the TIA.
It may be acquired from:
- Diseases. Some of the diseases that present nystagmus as a pathological sign:
- Aniridia
- Toxic or metabolic reasons could be the result of the following:
- Central nervous system (CNS) disorders, such as with a cerebellar problem, the nystagmus can be in any direction "including" horizontal. Purely vertical nystagmus is usually central in origin, but it is also a frequent adverse effect of high phenytoin toxicity. Causes include:
Choroideremia (; CHM) is a rare, X-linked recessive form of hereditary retinal degeneration that affects roughly 1 in 50,000 males. The disease causes a gradual loss of vision, starting with childhood night blindness, followed by peripheral vision loss, and progressing to loss of central vision later in life. Progression continues throughout the individual's life, but both the rate of change and the degree of visual loss are variable among those affected, even within the same family.
Choroideremia is caused by a loss-of-function mutation in the "CHM" gene which encodes Rab escort protein 1 (REP1), a protein involved in lipid modification of Rab proteins. While the complete mechanism of disease is not fully understood, the lack of a functional protein in the retina results in cell death and the gradual deterioration of the choroid, retinal pigment epithelium (RPE), and retinal photoreceptor cells.
As of 2017, there is no treatment for choroideremia; however, retinal gene therapy clinical trials have demonstrated a possible treatment.
While nothing currently can be done to stop or reverse the retinal degeneration, there are steps that can be taken to slow the rate of vision loss. UV-blocking sunglasses for outdoors, appropriate dietary intake of fresh fruit and leafy green vegetables, antioxidant vitamin supplements, and regular intake of dietary omega-3 very-long-chain fatty acids are all recommended.
One study found that a dietary supplement of lutein increases macular pigment levels in patients with choroideremia. Over a long period of time, these elevated levels of pigmentation could slow retinal degeneration. Additional interventions that may be needed include surgical correction of retinal detachment and cataracts, low vision services, and counseling to help cope with depression, loss of independence, and anxiety over job loss.
Other causes of color blindness include brain or retinal damage caused by shaken baby syndrome, accidents and other trauma which produce swelling of the brain in the occipital lobe, and damage to the retina caused by exposure to ultraviolet light (10–300 nm). Damage often presents itself later on in life.
Color blindness may also present itself in the spectrum of degenerative diseases of the eye, such as age-related macular degeneration, and as part of the retinal damage caused by diabetes. Another factor that may affect color blindness includes a deficiency in Vitamin A.
Some subtle forms of colorblindness may be associated with chronic solvent-induced encephalopathy (CSE), caused by longtime exposure to solvent vapors.
Red–green color blindness can be caused by ethambutol, a drug used in the treatment of tuberculosis.
Color blindness is typically inherited. It is most commonly inherited from mutations on the X chromosome but the mapping of the human genome has shown there are many causative mutations—mutations capable of causing color blindness originate from at least 19 different chromosomes and 56 different genes (as shown online at the Online Mendelian Inheritance in Man (OMIM)).
Two of the most common inherited forms of color blindness are protanomaly (and, more rarely, protanopia – the two together often known as "protans") and deuteranomaly (or, more rarely, deuteranopia – the two together often referred to as "deutans").
Both "protans" and "deutans" (of which the deutans are by far the most common) are known as "red–green color-blind" which is present in about 8 percent of human males and 0.6 percent of females of Northern European ancestry.
Some of the inherited diseases known to cause color blindness are:
- cone dystrophy
- cone-rod dystrophy
- achromatopsia (a.k.a. rod monochromatism, stationary cone dystrophy or cone dysfunction syndrome)
- blue cone monochromatism (a.k.a. blue cone monochromacy or X-linked achromatopsia)
- Leber's congenital amaurosis
- retinitis pigmentosa (initially affects rods but can later progress to cones and therefore color blindness).
Inherited color blindness can be congenital (from birth), or it can commence in childhood or adulthood. Depending on the mutation, it can be stationary, that is, remain the same throughout a person's lifetime, or progressive. As progressive phenotypes involve deterioration of the retina and other parts of the eye, certain forms of color blindness can progress to legal blindness, i.e., an acuity of 6/60 (20/200) or worse, and often leave a person with complete blindness.
Color blindness always pertains to the cone photoreceptors in retinas, as the cones are capable of detecting the color frequencies of light.
About 8 percent of males, and 0.6 percent of females, are red-green color blind in some way or another, whether it is one color, a color combination, or another mutation. The reason males are at a greater risk of inheriting an X linked mutation is that males only have one X chromosome (XY, with the Y chromosome carrying altogether different genes than the X chromosome), and females have two (XX); if a woman inherits a normal X chromosome in addition to the one that carries the mutation, she will not display the mutation. Men do not have a second X chromosome to override the chromosome that carries the mutation. If 8% of variants of a given gene are defective, the probability of a single copy being defective is 8%, but the probability that two copies are both defective is 0.08 × 0.08 = 0.0064, or just 0.64%.
It is relatively unusual (25% of the total number of cases) for cholesterol emboli to occur spontaneously; this usually happens in people with severe atherosclerosis of the large arteries such as the aorta. In the other 75% it is a complication of medical procedures involving the blood vessels, such as vascular surgery or angiography. In coronary catheterization, for instance, the incidence is 1.4%. Furthermore, cholesterol embolism may develop after the commencement of anticoagulants or thrombolytic medication that decrease blood clotting or dissolve blood clots, respectively. They probably lead to cholesterol emboli by removing blood clots that cover up a damaged atherosclerotic plaque; cholesterol-rich debris can then enter the bloodsteam.
Kawasaki disease affects boys more than girls, with people of Asian ethnicity, particularly Japanese and Korean people, most susceptible, as well as people of Afro-Caribbean ethnicity. The disease was rare in Caucasians until the last few decades, and incidence rates fluctuate from country to country.
Currently, Kawasaki disease is the most commonly diagnosed pediatric vasculitis in the world. By far, the highest incidence of Kawasaki disease occurs in Japan, with the most recent study placing the attack rate at 218.6 per 100,000 children <5 years of age (about one in 450 children). At this present attack rate, more than one in 150 children in Japan will develop Kawasaki disease during their lifetimes.
However, its incidence in the United States is increasing. Kawasaki disease is predominantly a disease of young children, with 80% of patients younger than five years of age. About 2,000-4,000 cases are identified in the U.S. each year (9 to 19 per 100,000 children younger than 5 years of age).
In the United Kingdom, estimates of incidence rate vary because of the rarity of Kawasaki disease. However, it is believed to affect fewer than one in every 25,000 people. Incidence of the disease doubled from 1991 to 2000, however, with four cases per 100,000 children in 1991 compared with a rise of eight cases per 100,000 in 2000.
In the continental United States, Kawasaki Disease is more common during the winter and early spring, boys with the disease outnumber girls by ≈1.5–1.7:1, and 76% of affected children are <5 years of age.
Carotid stenosis is a narrowing or constriction of the inner surface (lumen) of the carotid artery, usually caused by atherosclerosis.
Treatment of an episode of cholesterol emboli is generally symptomatic, i.e. it deals with the symptoms and complications but cannot reverse the phenomenon itself. In kidney failure resulting from cholesterol crystal emboli, statins (medication that reduces cholesterol levels) have been shown to halve the risk of requiring hemodialysis.
As the cause(s) of Kawasaki disease remain unknown, the illness is more accurately referred to as Kawasaki syndrome. Its cause is widely hypothesized to involve the interaction of genetic and environmental factors, possibly including an infection in combination with genetic predisposition to an autoimmune mechanism. The specific cause is unknown, but current theories center primarily on immunological causes. Evidence increasingly points to an infectious cause, but debate continues on whether the cause is a conventional antigenic substance or a superantigen. Researchers at Boston Children's Hospital reported, "some studies have found associations between the occurrence of Kawasaki disease and recent exposure to carpet cleaning or residence near a body of stagnant water; however, cause and effect have not been established."
Other data show a clear correlation between Kawasaki disease and tropospheric wind patterns; winds blowing from central Asia correlate with Kawasaki disease cases in Japan, Hawaii, and San Diego. This association with tropospheric winds has been shown to be modulated at seasonal and interannual timescales by the El Niño–Southern Oscillation phenomenon, further indicating the agent responsible for the disease is a wind-borne pathogen. Efforts are underway to identify the suspected pathogen in air-filters flown at altitude above Japan.
An association has been identified with an SNP in the "ITPKC" gene, which codes an enzyme that negatively regulates T-cell activation. Regardless of where they are living, Japanese children are more likely than other children to manifest the disease, which suggests genetic susceptibility. The HLA-B51 serotype has been found to be associated with endemic instances of the disease.