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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.
As one gets older, pockets of fluid can develop in the vitreous. When these pockets develop near the back of the eye, the vitreous can pull away from the retina and possibly tear it. Posterior vitreous detachment accounts for 3.7–11.7% of vitreous hemorrhage cases.
Less common causes of vitreous hemorrhage make up 6.4–18% of cases, and include:
- Proliferative sickle cell retinopathy
- Macroaneurysm
- Age-related macular degeneration
- Terson syndrome
- Retinal neovascularization as a result of branch or central retinal vein occlusion
- Other – about 7 cases in 100,000 have no known cause attributed to them.
Studies have identified the following abnormalities as risk factors for the development of BRVO:
- hypertension
- cardiovascular disease
- obesity
- glaucoma
Diabetes mellitus was not a major independent risk factor.
Risk factors for retinal detachment include severe myopia, retinal tears, trauma, family history, as well as complications from cataract surgery.
Retinal detachment can be mitigated in some cases when the warning signs are caught early. The most effective means of prevention and risk reduction is through education of the initial signs, and encouragement for people to seek ophthalmic medical attention if they have symptoms suggestive of a posterior vitreous detachment. Early examination allows detection of retinal tears which can be treated with laser or cryotherapy. This reduces the risk of retinal detachment in those who have tears from around 1:3 to 1:20. For this reason, the governing bodies in some sports require regular eye examination.
Trauma-related cases of retinal detachment can occur in high-impact sports or in high speed sports. Although some recommend avoiding activities that increase pressure in the eye, including diving and skydiving, there is little evidence to support this recommendation, especially in the general population. Nevertheless, ophthalmologists generally advise people with high degrees of myopia to try to avoid exposure to activities that have the potential for trauma, increase pressure on or within the eye itself, or include rapid acceleration and deceleration, such as bungee jumping or roller coaster rides.
Intraocular pressure spikes occur during any activity accompanied by the Valsalva maneuver, including weightlifting. An epidemiological study suggests that heavy manual lifting at work may be associated with increased risk of rhegmatogenous retinal detachment, but this relationship is not strong. In this study, obesity also appeared to increase the risk of retinal detachment. A high Body Mass Index (BMI) and elevated blood pressure have been identified as a risk factor in non-myopic individuals.
Genetic factors promoting local inflammation and photoreceptor degeneration may also be involved in the development of the disease.
Other risk factors include the following:
- Glaucoma
- AIDS
- Cataract surgery
- Diabetic retinopathy
- Eclampsia
- Family history of retinal detachment
- Homocysteinuria
- Malignant hypertension
- Metastatic cancer, which spreads to the eye (eye cancer)
- Retinoblastoma
- Severe myopia
- Smoking and passive smoking
- Stickler syndrome
- Von Hippel-Lindau disease
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
CSR is a fluid detachment of macula layers from their supporting tissue. This allows choroidal fluid to leak beneath the retina. The buildup of fluid seems to occur because of small breaks in the retinal pigment epithelium.
CSR is sometimes called "idiopathic CSR" which means that its cause is unknown. Nevertheless, stress appears to play an important role. An oft-cited but potentially inaccurate conclusion is that persons in stressful occupations, such as airplane pilots, have a higher incidence of CSR.
CSR has also been associated with cortisol and corticosteroids. Persons with CSR have higher levels of cortisol. Cortisol is a hormone secreted by the adrenal cortex which allows the body to deal with stress, which may explain the CSR-stress association. There is extensive evidence to the effect that corticosteroids (e.g. cortisone), commonly used to treat inflammations, allergies, skin conditions and even certain eye conditions, can trigger CSR, aggravate it and cause relapses. In a study documented by Indian Journal of Pharmacology, a young male was using Prednisolone and began to display subretinal fluid indicative of CSR. With the discontinuation of the steroid drop the subretinal fluid resolved and did not show any sign of recurrence. Thus indicating the steroid was the probable cause of the CSR. A study of 60 persons with Cushing's syndrome found CSR in 3 (5%). Cushing's syndrome is characterized by very high cortisol levels. Certain sympathomimetic drugs have also been associated with causing the disease.
Evidence has also implicated helicobacter pylori (see gastritis) as playing a role. It would appear that the presence of the bacteria is well correlated with visual acuity and other retinal findings following an attack.
Evidence also shows that sufferers of MPGN type II kidney disease can develop retinal abnormalities including CSR caused by deposits of the same material that originally damaged the glomerular basement membrane in the kidneys.
Predisposing factors for Postoperative PVR are preoperative PVR, aphakia, high levels of vitreous proteins, duration of retinal detachment before corrective surgery, the size of the retinal hole or tear, intra-ocular inflammation, vitreous hemorrhage, and trauma to the eye. An equation to calculate the patient's risk for acquiring PVR is:
1 is added if the risk factor is present and 0 if the risk factor is absent. A patient is at a high risk for developing PVR is the PVR score is >6.33.
In general, BRVO has a good prognosis: after 1 year 50–60% of eyes have been reported to have a final VA of 20/40 or better even without any treatment. With time the dramatic picture of an acute BRVO becomes more subtle, hemorrhages fade so that the retina can look almost normal. Collateral vessels develop to help drain the affected area.
Although intermediate uveitis can develop at any age, it primarily afflicts children and young adults. There is a bimodal distribution with one peak in the second decade and another peak in the third or fourth decade.
In the United States the proportion of patients with intermediate uveitis is estimated to be 4-8% of uveitis cases in referral centers. The National Institutes of Health reports a higher percentage (15%), which may indicate improved awareness or the nature of the uveitis referral clinic. In the pediatric population, intermediate uveitis can account for up to 25% of uveitis cases.
All people with "diabetes mellitus" are at riskthose with Type I diabetes and those with Type II diabetes. The longer a person has diabetes, the higher their risk of developing some ocular problem. Between 40 and 45 percent of Americans diagnosed with diabetes have some stage of diabetic retinopathy. After 20 years of diabetes, nearly all patients with Type I diabetes and >60% of patients with Type II diabetes have some degree of retinopathy; however, these statistics were published in 2002 using data from four years earlier, limiting the usefulness of the research. The subjects would have been diagnosed with diabetes in the late 1970s, before modern fast acting insulin and home glucose testing.
Prior studies had also assumed a clear glycemic threshold between people at high and low risk of diabetic retinopathy.
However, it has been shown that the widely accepted WHO and American Diabetes Association diagnostic cutoff for diabetes of a fasting plasma glucose ≥ 7.0 mmol/l (126 mg/dl) does not accurately identify diabetic retinopathy among patients. The cohort study included a multi-ethnic, cross-sectional adult population sample in the US, as well as two cross-sectional adult populations in Australia. For the US-based component of the study, the sensitivity was 34.7% and specificity was 86.6%. For patients at similar risk to those in this study (15.8% had diabetic retinopathy), this leads to a positive predictive value of 32.7% and negative predictive value of 87.6%.
Published rates vary between trials, the proposed explanation being differences in study methods and reporting of prevalence rather than incidence values.
During pregnancy, diabetic retinopathy may also be a problem for women with diabetes.
It is recommended that all pregnant women with diabetes have dilated eye examinations each trimester to protect their vision.
People with Down's syndrome, who have extra chromosome 21 material, almost never acquire diabetic retinopathy. This protection appears to be due to the elevated levels of endostatin, an anti-angiogenic protein, derived from collagen XVIII. The collagen XVIII gene is located on chromosome 21.
Retinal haemorrhages commonly occur in high attitude climbers, most likely due to the effects of systemic hypoxia on the eye. Risk is correlated with the maximum altitude reached, duration of exposure to high altitude conditions, and climb rate.
Pars planitis is considered a subset of intermediate uveitis and is characterized by the presence of white exudates (snowbanks) over the pars plana or by aggregates of inflammatory cells in the vitreous (snowballs) in the absence of an infectious or a systemic disease. Some physicians believe that patients with pars planitis have worse vitritis, more severe macular edema, and a guarded prognosis compared to other patients with intermediate uveitis.
This ocular pathology was first described by Iwanoff in 1865, and it has been shown to occur in about 7% of the population. It can occur more frequently in the older population with postmortem studies showing it in 2% of those aged 50 years and 20% in those aged 75 years.
The incidence of retinal detachment in otherwise normal eyes is around 5 new cases in 100,000 persons per year. Detachment is more frequent in middle-aged or elderly populations, with rates of around 20 in 100,000 per year. The lifetime risk in normal individuals is about 1 in 300. Asymptomatic retinal breaks are present in about 6% of eyes in both clinical and autopsy studies.
- Retinal detachment is more common in people with severe myopia (above 5–6 diopters), in whom the retina is more thinly stretched. In such patients, lifetime risk rises to 1 in 20. About two-thirds of cases of retinal detachment occur in myopics. Myopic retinal detachment patients tend to be younger than non-myopic ones.
- Retinal detachment is more frequent after surgery for cataracts. The estimated long-term prevalence of retinal detachment after cataract surgery is in the range of 5 to 16 per 1000 cataract operations, but is much higher in patients who are highly myopic, with a prevalence of up to 7% being reported in one study. One study found that the probability of experiencing retinal detachment within 10 years of cataract surgery may be about 5 times higher than in the absence of treatment.
- Tractional retinal detachments can also occur in patients with proliferative diabetic retinopathy or those with proliferative retinopathy of sickle cell disease. In proliferative retinopathy, abnormal blood vessels (neovascularization) grow within the retina and extend into the vitreous. In advanced disease, the vessels can pull the retina away from the back wall of the eye, leading to tractional retinal detachment.
Although retinal detachment usually occurs in just one eye, there is a 15% chance of it developing in the other eye, and this risk increases to 25–30% in patients who have had a retinal detachment and cataracts extracted from both eyes.
No complications are encountered in most patients with lattice degeneration, although in young myopes, retinal detachment can occur. There are documented cases with macula-off retinal detachment in patients with asymptomatic lattice degeneration. Partial or complete vision loss almost always occurs in such cases. Currently there is no prevention or cure for lattice degeneration.
Retinal haemorrhages, especially mild ones not associated with chronic disease, will normally resorb without treatment. Laser surgery is a treatment option which uses a laser beam to seal off damaged blood vessels in the retina. Anti-vascular endothelial growth factor (VEGF) drugs like Avastin and Lucentis have also been shown to repair retinal haemorrhaging in diabetic patients and patients with haemorrhages associated with new vessel growth.
The prognosis for CSR is generally excellent. Whilst immediate vision loss may be as poor as 20/200 in the affected eye, clinically over 90% of patients regain 20/30 vision or better within 6 months.
Once the fluid has resolved, by itself or through treatment, visual acuity should continue to improve and distortion should reduce as the eye heals. However, some visual abnormalities can remain even if visual acuity is measured at 20/20, and lasting problems include decreased night vision, reduced color discrimination, and localized distortion caused by scarring of the sub-retinal layers.
Complications include subretinal neovascularization and pigment epithelial detachment.
The disease can re-occur causing progressive vision loss. There is also a chronic form, titled as type II central serous retinopathy, which occurs in approximately 5% of cases. This exhibits diffuse rather than focalized abnormality of the pigment epithelium, producing a persistent subretinal fluid. The serous fluid in these cases tends to be shallow rather than dome shaped. Prognosis for this condition is less favorable and continued clinical consultation is advised.
A posterior vitreous detachment (PVD) is a condition of the eye in which the vitreous membrane separates from the retina.
It refers to the separation of the posterior hyaloid membrane from the retina anywhere posterior to the vitreous base (a 3–4 mm wide attachment to the ora serrata).
The condition is common for older adults; over 75% of those over the age of 65 develop it. Although less common among people in their 40s or 50s, the condition is not rare for those individuals. Some research has found that the condition is more common among women.
The vitreous (Latin for "glassy") humor is a gel which fills the eye behind the lens. Between it and the retina is the vitreous membrane. With age the vitreous humor changes, shrinking and developing pockets of liquefaction, similar to the way a gelatin dessert shrinks and detaches from the edge of a pan. At some stage the vitreous membrane may peel away from the retina. This is usually a sudden event, but it may also occur slowly over months.
Age and refractive error play a role in determining the onset of PVD in a healthy person. PVD is rare in emmetropic people under the age of 40 years, and increases with age to 86% in the 90s. Several studies have found a broad range of incidence of PVD, from 20% of autopsy cases to 57% in a more elderly population of patients (average age was 83.4 years).
People with myopia (nearsightedness) greater than 6 diopters are at higher risk of PVD at all ages.
Posterior vitreous detachment does not directly threaten vision. Even so, it is of increasing interest because the interaction between the vitreous body and the retina might play a decisive role in the development of major pathologic vitreoretinal conditions, such as epiretinal membrane.
PVD may also occur in cases of cataract surgery, within weeks or months of the surgery.
The vitreous membrane is more firmly attached to the retina anteriorly, at a structure called the vitreous base. The membrane does not normally detach from the vitreous base, although it can be detached with extreme trauma. However, the vitreous base may have an irregular posterior edge. When the edge is irregular, the forces of the vitreous membrane peeling off the retina can become concentrated at small posterior extensions of the vitreous base. Similarly, in some people with retinal lesions such as lattice retinal degeneration or chorio-retinal scars, the vitreous membrane may be abnormally adherent to the retina. If enough traction occurs the retina may tear at these points. If there are only small point tears, these can allow glial cells to enter the vitreous humor and proliferate to create a thin epiretinal membrane that distorts vision. In more severe cases, vitreous fluid may seep under the tear, separating the retina from the back of the eye, creating a retinal detachment. Trauma can be any form from a blunt force trauma to the face such as a boxer's punch or even in some cases has been known to be from extremely vigorous coughing or blowing of the nose.
Optic pits occur equally between men and women. They are seen in roughly 1 in 10,000 eyes, and approximately 85% of optic pits are found to be unilateral (i.e. in only one eye of any affected individual). About 70% are found on the temporal side (or lateral one-half) of the optic disc. Another 20% are found centrally, while the remaining pits are located either superiorly (in the upper one-half), inferiorly (in the lower one-half), or nasally (in the medial one-half towards the nose).
There is no good evidence for any preventive actions, since it appears this is a natural response to aging changes in the vitreous. Posterior vitreous detachment (PVD) has been estimated to occur in over 75 per cent of the population over age 65, that PVD is essentially a harmless condition (although with some disturbing symptoms), and that it does not normally threaten sight. However, since epiretinal membrane appears to be a protective response to PVD, where inflammation, exudative fluid, and scar tissue is formed, it is possible that NSAIDs may reduce the inflammation response. Usually there are flashing light experiences and the emergence of floaters in the eye that herald changes in the vitreous before the epiretinal membrane forms g
No particular risk factors have been conclusively identified; however, there have been a few reports that demonstrate an autosomal dominant pattern of inheritance in some families. Therefore, a family history of optic pits may be a possible risk factor.
Eales disease most commonly affects healthy young adults. Male predominance (up to 97.6%) has been reported in a majority of the series. The predominant age of onset of symptoms is between 20 and 30 years. The disease is now seen more commonly in the Indian subcontinent.
Familial transmission is now recognized in a small proportion of people with MacTel type 2; however, the nature of any related genetic defect or defects remains elusive. The MacTel genetic study team hopes that exome analysis in the affected population and relatives may be more successful in identifying related variants.