Flashcards in Eye Conditions Deck (7)
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1
Q
Qué es amor?
A
Cuando una persona te hace sentir que tienes que dar todo por ella. Te da felicidad, ganas de amar y de seguir viviendo. Te amo baby. Eres parte de mi vida y por eso quiero que seas parte de ella siempre.
2
Q
What is Glaucoma?
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A
A common eye condition in which the fluid pressure inside the eye rises to a level higher than healthy for that eye. If untreated, it may damage the optic nerve, causing the loss of vision or even blindness.
There are several different types of glaucoma, including open-angle glaucoma and acute angle-closure glaucoma. Open-angle glaucoma is the common adult-onset type of glaucoma. Acute angle-closure glaucoma is a less common form of glaucoma that can rapidly impair vision.
The treatment of glaucoma may include medication, surgery, or laser surgery. Eyedrops or pills alone can usually control glaucoma, although they cannot cure it. Some drugs are designed to reduce pressure by slowing the flow of fluid into the eye, while others help to improve fluid drainage. Surgery to help fluid escape from the eye, and laser surgery is now often used for the same purpose. In laser surgery for glaucoma, a laser beam of light is focused on the part of the anterior chamber where the fluid leaves the eye. This results in a series of small changes, making it easier for fluid to exit. Over time, the effect of laser surgery may wear off.
There are several different types of glaucoma, including open-angle glaucoma and acute angle-closure glaucoma. Open-angle glaucoma is the common adult-onset type of glaucoma. Acute angle-closure glaucoma is a less common form of glaucoma that can rapidly impair vision.
The treatment of glaucoma may include medication, surgery, or laser surgery. Eyedrops or pills alone can usually control glaucoma, although they cannot cure it. Some drugs are designed to reduce pressure by slowing the flow of fluid into the eye, while others help to improve fluid drainage. Surgery to help fluid escape from the eye, and laser surgery is now often used for the same purpose. In laser surgery for glaucoma, a laser beam of light is focused on the part of the anterior chamber where the fluid leaves the eye. This results in a series of small changes, making it easier for fluid to exit. Over time, the effect of laser surgery may wear off.
3
Q
What is Retinitis pigmentosa?
A
-What is?
Retinitis pigmentosa is the most common of a group of hereditary progressive retinal degenerations or dystrophies. There is considerable variation and overlap among the various forms of retinitis pigmentosa. Common to all of them is progressive degeneration of the retina, specifically of the light receptors, known as the rods and cones. The rods of the retina are involved earlier in the course of the disease, and cone deterioration occurs later. In this progressive degeneration of the retina, the peripheral vision slowly constricts and central vision is usually retained until late in the disease.
-What causes retinitis pigmentosa?
Retinitis pigmentosa is an inherited condition which involves both eyes. If it starts in one eye, the other eye usually develops the same condition in a number of years.
Retinitis pigmentosa is usually diagnosed during the teenage years but may be present at birth. The latter congenital type is usually fairly stable and nonprogressive. Cases that are diagnosed later in life are often milder and may progress more slowly.
RP is sometimes associated with other systemic illnesses. Usher syndrome, characterized by retinitis pigmentosa and neural hearing loss, is the most common cause of deaf-blindness in the United States. The hearing loss usually is diagnosed earlier than the eye changes.
-What are retinitis pigmentosa symptoms and signs?
Retinitis pigmentosa begins as rod degeneration, the patient first notices increasing difficulty in night vision, followed by difficulty seeing in the periphery. Slowly progressive constriction of the visual field leads to tunnel vision. A small area of central vision in both eyes usually persists for years. Generally night blindness precedes tunnel vision by years or even decades.
- How is retinitis pigmentosa diagnosed?
*Decreased vision at night or in low light
*Loss of side (peripheral) vision
*Loss of central vision (in advanced cases)
Two tests are essential in the diagnosis and the follow-up exams.
Visual field testing will find defects in the peripheral (side vision) with the degree of loss related to defects in relation to the damage occurring in this disease. Over time, the visual field may reduce to a small central island of vision causing "tunnel vision." The final progression may be the complete loss of the remaining central vision.
Electrophysiological testing by the ophthalmologist (often by referral to a university ophthalmology department, since very few private offices would have this equipment) is often diagnostic. Responses to flashes of light are measured via electrodes placed on the surface of the eye. It is a painless test. The electroretinogram (ERG), in conjunction with the visual field exam, will usually make the diagnosis. This will also determine if there is any cone involvement.
- What is the treatment for retinitis pigmentosa?
There is no specific cure for retinitis pigmentosa.
Some Facts:
Retinitis pigmentosa is a bilateral inherited condition that involves both eyes.
It usually starts later in life and progresses to blindness.
Low-vision rehabilitation provides some help in coping with the condition, but there is no treatment or cure at this time.
Retinitis pigmentosa is the most common of a group of hereditary progressive retinal degenerations or dystrophies. There is considerable variation and overlap among the various forms of retinitis pigmentosa. Common to all of them is progressive degeneration of the retina, specifically of the light receptors, known as the rods and cones. The rods of the retina are involved earlier in the course of the disease, and cone deterioration occurs later. In this progressive degeneration of the retina, the peripheral vision slowly constricts and central vision is usually retained until late in the disease.
-What causes retinitis pigmentosa?
Retinitis pigmentosa is an inherited condition which involves both eyes. If it starts in one eye, the other eye usually develops the same condition in a number of years.
Retinitis pigmentosa is usually diagnosed during the teenage years but may be present at birth. The latter congenital type is usually fairly stable and nonprogressive. Cases that are diagnosed later in life are often milder and may progress more slowly.
RP is sometimes associated with other systemic illnesses. Usher syndrome, characterized by retinitis pigmentosa and neural hearing loss, is the most common cause of deaf-blindness in the United States. The hearing loss usually is diagnosed earlier than the eye changes.
-What are retinitis pigmentosa symptoms and signs?
Retinitis pigmentosa begins as rod degeneration, the patient first notices increasing difficulty in night vision, followed by difficulty seeing in the periphery. Slowly progressive constriction of the visual field leads to tunnel vision. A small area of central vision in both eyes usually persists for years. Generally night blindness precedes tunnel vision by years or even decades.
- How is retinitis pigmentosa diagnosed?
*Decreased vision at night or in low light
*Loss of side (peripheral) vision
*Loss of central vision (in advanced cases)
Two tests are essential in the diagnosis and the follow-up exams.
Visual field testing will find defects in the peripheral (side vision) with the degree of loss related to defects in relation to the damage occurring in this disease. Over time, the visual field may reduce to a small central island of vision causing "tunnel vision." The final progression may be the complete loss of the remaining central vision.
Electrophysiological testing by the ophthalmologist (often by referral to a university ophthalmology department, since very few private offices would have this equipment) is often diagnostic. Responses to flashes of light are measured via electrodes placed on the surface of the eye. It is a painless test. The electroretinogram (ERG), in conjunction with the visual field exam, will usually make the diagnosis. This will also determine if there is any cone involvement.
- What is the treatment for retinitis pigmentosa?
There is no specific cure for retinitis pigmentosa.
Some Facts:
Retinitis pigmentosa is a bilateral inherited condition that involves both eyes.
It usually starts later in life and progresses to blindness.
Low-vision rehabilitation provides some help in coping with the condition, but there is no treatment or cure at this time.
4
Q
What is macular and age-related macular degenaration?
A
-What is macular degeneration?
Macular degeneration is a common, painless eye condition in which the central portion of the retina deteriorates and does not function adequately.
-What is age-related macular degeneration (AMD)?
Age-related macular degeneration (AMD or ARMD) is by far the most common type. AMD is a disease associated with aging that gradually destroys sharp central vision that is needed for seeing objects clearly and for common daily tasks such as reading and driving.
AMD occurs in two forms:
"Wet" age-related macular degeneration is less common but more aggressive in its progression to severe central vision loss.
"Dry" age-related macular degeneration is the more common type and is more slowly progressive in causing visual loss.
Wet:
Wet AMD occurs when abnormal blood vessels grow from the choroid (the layer of blood vessels between the retina and the outer firm coat of the eye called the sclera) under and into the macular portion of the retina. These new blood vessels (known as choroidal neovascularization or CNV) tend to be very fragile and often leak blood and fluid. The blood and fluid raise the macula from its normal place at the back of the eye and interfere with the retina's function and causes the central vision to blur. Under these circumstances, vision loss may be rapid and severe. Some patients, however, do not notice visual changes despite the onset of CNV. Therefore, periodic eye examinations are very important for patients at risk for CNV.
Once CNV has developed in one eye, whether there is a visual loss or not, the other eye is at relatively high risk for the same change.
All wet AMD is described as advanced AMD, whether or not there is serious visual loss. Wet AMD does not have not have stages like dry AMD. The wet form generally leads to significantly more vision loss than the dry form.
All people who have the dry form of AMD are at risk for development of the wet form. All people who have the wet form had the dry form first. The dry form can advance and cause vision loss without turning into the wet form. The dry form also suddenly can turn into the wet form. Currently, there is no certain way to predict if or when the dry form will turn into the wet form.
-What is the treatment for wet macular degeneration?
Wet AMD can be treated with laser surgery, photodynamic therapy, and injections into the eye. None of these treatments is a permanent cure for wet AMD. The disease and loss of vision may progress despite treatment.
Dry:
In dry AMD, the light sensitive cells in the macula slowly break down. With less of the macula functioning, central vision diminishes. Dry AMD often occurs in just one eye at first. Later, the other eye can be affected. The cause of dry AMD is unknown.
Dry AMD has three stages, early, intermediate, or advanced, all of which may occur in one or both eyes. People with early AMD have either several small drusen or a few medium-sized drusen. At this stage, there are no symptoms and no vision loss.
People with intermediate AMD have either many medium-sized drusen or one or more large drusen. Some people see a blurred spot in the center of their vision. More light may be needed for reading and other tasks.
In addition to drusen, people with advanced dry AMD have a breakdown of light-sensitive cells and supporting tissue in the central retinal area. This breakdown can cause a blurred spot in the center of your vision. Over time, the blurred spot may get bigger and darker, taking more of your central vision. You may have difficulty reading or recognizing faces until they are very close to you.
The dry form is much more common than the wet form. In dry AMD, there is no CNV (abnormal new blood vessel formation under the retina) and no fluid or blood leakage into the retina (retinal swelling or bleeding). More than 85% of all people with intermediate and advanced AMD combined have the dry form. However, if only advanced AMD is considered, about two-thirds of patients have the wet form.
Dry AMD can advance and cause vision loss without turning into wet AMD. Dry AMD can also rapidly transform into the wet form by the growth of new blood vessels.
-What is the treatment for dry macular degeneration?
There is currently no treatment available to reverse dry macular degeneration. However, dry macular degeneration is usually slowly progressive and most patients with this condition are able to live relatively normal, productive lives. Often one eye is affected more than the other.
-What are risk factors for macular degeneration?
The greatest risk factor is age. Other risk factors include smoking, obesity, white race, female gender, a family history of macular degeneration, a diet low in fruit and vegetables, high blood pressure, and elevated blood cholesterol.
- What are macular degeneration symptoms?
Neither dry nor wet AMD cause any eye pain.
The most common early symptom in dry AMD is blurred vision. As fewer cells in the macula are able to function, people will see details less clearly in front of them, such as faces or words in a book. Often this blurred vision will go away in brighter light. If the loss of these light-sensing cells becomes great, people may see a small black or gray blind spot in the middle of their field of vision.
Dry macular degeneration symptoms usually develop gradually and do not include total blindness. However, the symptoms may worsen the quality of life by making reading, driving, and facial recognition difficult Other symptoms may include decreased night vision, a decrease in the intensity or brightness of colors, increase in the haziness of overall vision.
Dry macular degeneration may affect one eye or both eyes. If only one eye is affected, symptoms may not be noticed because the unaffected eye has no visual symptoms.
All of the above symptoms may also be noticed in the wet form of AMD. In addition, the most common symptom in wet macular degeneration is straight lines appearing crooked or wavy. This results when fluid from the leaking blood vessels gathers within and lifts the macula, distorting vision. Larger areas of gray or black in the central area of vision may also occur. The central vision may decrease over a short period of time.
-What are signs of macular degeneration?
In both dry and wet forms of macular degeneration, the ophthalmologist may find decreased visual clarity (acuity) with preservation of peripheral vision and changes in the central retina visible with the ophthalmoscope.
-How is macular degeneration diagnosed?
Your ophthalmologist may suspect the diagnosis of AMD if you are over age 60 and have had recent changes in your central vision. To look for signs of the disease, he or she will use eyedrops to dilate, or enlarge, your pupils. Dilating the pupils allows your ophthalmologist to view the back of the eye better.
Early AMD is often diagnosed during a comprehensive eye exam in patients without significant symptoms. This eye exam includes having drops placed in your eyes to enlarge, or dilate, the pupils. Your ophthalmologist will carefully examine the central portion of the retina to determine the presence or absence of AMD using various illuminating and magnifying devices.
During the eye exam, you may be asked to look at a checkerboard pattern called an Amsler grid. When looking at an Amsler grid with one eye, patients with AMD may notice that the straight lines of the checkerboard appear wavy or are missing.
Other diagnostic tests that your ophthalmologist may perform include retinal photography, fluorescein angiography and optical coherence tomography. All of these can help to differentiate between dry and wet forms of AMD and also document the abnormalities so that progression and response to treatment can be better measured.
Macular degeneration facts
The macula is in the center of the retina, the light-sensitive layer of tissue at the back of the eye. The macula is responsible for central vision (straight-ahead vision). Degeneration of the macula occurs most often after the age of 60 years and is termed age-related macular generation (AMD).
AMD is a painless condition.
There are two types of AMD: dry AMD and wet AMD.
Smoking, high blood pressure, obesity, a diet high in unsaturated fats and simple carbohydrates and lack of exercise all increase the risk of AMD.
Early symptoms of dry AMD include slightly blurred vision, the need for more light for reading, and difficulty recognizing faces until very close to the person. A symptom of more advanced dry AMD is the presence of a blurred spot in the center of vision. An early symptom of wet AMD is the wavy appearance of straight lines.
Dry AMD cannot be treated at present, but progression can be slowed through a healthy lifestyle and, in certain cases, through anti-oxidant vitamins. Injections into the eye of anti-angiogenic agents are successfully used in arresting or slowing wet AMD. Because of new therapies for the wet form of AMD, early diagnosis of wet AMD is particularly critical.
Macular degeneration is a common, painless eye condition in which the central portion of the retina deteriorates and does not function adequately.
-What is age-related macular degeneration (AMD)?
Age-related macular degeneration (AMD or ARMD) is by far the most common type. AMD is a disease associated with aging that gradually destroys sharp central vision that is needed for seeing objects clearly and for common daily tasks such as reading and driving.
AMD occurs in two forms:
"Wet" age-related macular degeneration is less common but more aggressive in its progression to severe central vision loss.
"Dry" age-related macular degeneration is the more common type and is more slowly progressive in causing visual loss.
Wet:
Wet AMD occurs when abnormal blood vessels grow from the choroid (the layer of blood vessels between the retina and the outer firm coat of the eye called the sclera) under and into the macular portion of the retina. These new blood vessels (known as choroidal neovascularization or CNV) tend to be very fragile and often leak blood and fluid. The blood and fluid raise the macula from its normal place at the back of the eye and interfere with the retina's function and causes the central vision to blur. Under these circumstances, vision loss may be rapid and severe. Some patients, however, do not notice visual changes despite the onset of CNV. Therefore, periodic eye examinations are very important for patients at risk for CNV.
Once CNV has developed in one eye, whether there is a visual loss or not, the other eye is at relatively high risk for the same change.
All wet AMD is described as advanced AMD, whether or not there is serious visual loss. Wet AMD does not have not have stages like dry AMD. The wet form generally leads to significantly more vision loss than the dry form.
All people who have the dry form of AMD are at risk for development of the wet form. All people who have the wet form had the dry form first. The dry form can advance and cause vision loss without turning into the wet form. The dry form also suddenly can turn into the wet form. Currently, there is no certain way to predict if or when the dry form will turn into the wet form.
-What is the treatment for wet macular degeneration?
Wet AMD can be treated with laser surgery, photodynamic therapy, and injections into the eye. None of these treatments is a permanent cure for wet AMD. The disease and loss of vision may progress despite treatment.
Dry:
In dry AMD, the light sensitive cells in the macula slowly break down. With less of the macula functioning, central vision diminishes. Dry AMD often occurs in just one eye at first. Later, the other eye can be affected. The cause of dry AMD is unknown.
Dry AMD has three stages, early, intermediate, or advanced, all of which may occur in one or both eyes. People with early AMD have either several small drusen or a few medium-sized drusen. At this stage, there are no symptoms and no vision loss.
People with intermediate AMD have either many medium-sized drusen or one or more large drusen. Some people see a blurred spot in the center of their vision. More light may be needed for reading and other tasks.
In addition to drusen, people with advanced dry AMD have a breakdown of light-sensitive cells and supporting tissue in the central retinal area. This breakdown can cause a blurred spot in the center of your vision. Over time, the blurred spot may get bigger and darker, taking more of your central vision. You may have difficulty reading or recognizing faces until they are very close to you.
The dry form is much more common than the wet form. In dry AMD, there is no CNV (abnormal new blood vessel formation under the retina) and no fluid or blood leakage into the retina (retinal swelling or bleeding). More than 85% of all people with intermediate and advanced AMD combined have the dry form. However, if only advanced AMD is considered, about two-thirds of patients have the wet form.
Dry AMD can advance and cause vision loss without turning into wet AMD. Dry AMD can also rapidly transform into the wet form by the growth of new blood vessels.
-What is the treatment for dry macular degeneration?
There is currently no treatment available to reverse dry macular degeneration. However, dry macular degeneration is usually slowly progressive and most patients with this condition are able to live relatively normal, productive lives. Often one eye is affected more than the other.
-What are risk factors for macular degeneration?
The greatest risk factor is age. Other risk factors include smoking, obesity, white race, female gender, a family history of macular degeneration, a diet low in fruit and vegetables, high blood pressure, and elevated blood cholesterol.
- What are macular degeneration symptoms?
Neither dry nor wet AMD cause any eye pain.
The most common early symptom in dry AMD is blurred vision. As fewer cells in the macula are able to function, people will see details less clearly in front of them, such as faces or words in a book. Often this blurred vision will go away in brighter light. If the loss of these light-sensing cells becomes great, people may see a small black or gray blind spot in the middle of their field of vision.
Dry macular degeneration symptoms usually develop gradually and do not include total blindness. However, the symptoms may worsen the quality of life by making reading, driving, and facial recognition difficult Other symptoms may include decreased night vision, a decrease in the intensity or brightness of colors, increase in the haziness of overall vision.
Dry macular degeneration may affect one eye or both eyes. If only one eye is affected, symptoms may not be noticed because the unaffected eye has no visual symptoms.
All of the above symptoms may also be noticed in the wet form of AMD. In addition, the most common symptom in wet macular degeneration is straight lines appearing crooked or wavy. This results when fluid from the leaking blood vessels gathers within and lifts the macula, distorting vision. Larger areas of gray or black in the central area of vision may also occur. The central vision may decrease over a short period of time.
-What are signs of macular degeneration?
In both dry and wet forms of macular degeneration, the ophthalmologist may find decreased visual clarity (acuity) with preservation of peripheral vision and changes in the central retina visible with the ophthalmoscope.
-How is macular degeneration diagnosed?
Your ophthalmologist may suspect the diagnosis of AMD if you are over age 60 and have had recent changes in your central vision. To look for signs of the disease, he or she will use eyedrops to dilate, or enlarge, your pupils. Dilating the pupils allows your ophthalmologist to view the back of the eye better.
Early AMD is often diagnosed during a comprehensive eye exam in patients without significant symptoms. This eye exam includes having drops placed in your eyes to enlarge, or dilate, the pupils. Your ophthalmologist will carefully examine the central portion of the retina to determine the presence or absence of AMD using various illuminating and magnifying devices.
During the eye exam, you may be asked to look at a checkerboard pattern called an Amsler grid. When looking at an Amsler grid with one eye, patients with AMD may notice that the straight lines of the checkerboard appear wavy or are missing.
Other diagnostic tests that your ophthalmologist may perform include retinal photography, fluorescein angiography and optical coherence tomography. All of these can help to differentiate between dry and wet forms of AMD and also document the abnormalities so that progression and response to treatment can be better measured.
Macular degeneration facts
The macula is in the center of the retina, the light-sensitive layer of tissue at the back of the eye. The macula is responsible for central vision (straight-ahead vision). Degeneration of the macula occurs most often after the age of 60 years and is termed age-related macular generation (AMD).
AMD is a painless condition.
There are two types of AMD: dry AMD and wet AMD.
Smoking, high blood pressure, obesity, a diet high in unsaturated fats and simple carbohydrates and lack of exercise all increase the risk of AMD.
Early symptoms of dry AMD include slightly blurred vision, the need for more light for reading, and difficulty recognizing faces until very close to the person. A symptom of more advanced dry AMD is the presence of a blurred spot in the center of vision. An early symptom of wet AMD is the wavy appearance of straight lines.
Dry AMD cannot be treated at present, but progression can be slowed through a healthy lifestyle and, in certain cases, through anti-oxidant vitamins. Injections into the eye of anti-angiogenic agents are successfully used in arresting or slowing wet AMD. Because of new therapies for the wet form of AMD, early diagnosis of wet AMD is particularly critical.
5
Q
What is the definition of astigmatism?
A
In order to see clearly, the eye must be able to focus light into a single plane at the retinal surface. In astigmatism, a point (or spot) of light is focussed at two different planes, causing blurred vision. An optical system (or eye) without astigmatism is called spherical and has only one focus for all rays of light. An optical system with astigmatism is one in which rays that propagate in two perpendicular planes have different foci. For example, if an optical system with astigmatism is used to form an image of a plus sign, the vertical and horizontal lines will never be in focus at the same time, since they are in sharp focus at two distinctly different distances.
In an eye without astigmatism, the surface of the cornea is shaped like a ping-pong ball, where all the curves are the same. This is called a spherical surface. In an eye with astigmatism, the surface of the cornea is shaped more like a football, where there are two different surface curves located 90 degrees apart. This is called a toric surface.
-What are the different types of astigmatism?
There are various classification systems for astigmatism, based on the anatomical source of the astigmatism, the regularity/ irregularity of astigmatism, or the direction of astigmatism.
Most astigmatism in the human eye has its source within the cornea, although there are irregularities of the lens that can lead to astigmatism, known as lenticular astigmatism.
Most corneal astigmatism is regular, meaning that the cornea is most curved (steepest) 90 degrees away from the surface of the cornea that is the least curved (flattest) and that the transition from most curved to least curved surface occurs in a regular manner. Regular astigmatism can be corrected with glasses, soft lenses, rigid lenses, or refractive surgery.
Irregular astigmatism is defined as arising from any corneal surface that is neither spherical nor regularly astigmatic. Irregular astigmatism cannot be corrected with glasses or soft contact lenses.
A historical classification of astigmatism differentiates “with the rule” astigmatism from "against the rule" astigmatism. In with the rule astigmatism, the steepest curvature (most curved part to the cornea) lies in or close to the vertical meridian, similar to the surface of a football lying on it side. In against the rule astigmatism, the steepest (most curved) part of the cornea is in or close to the horizontal meridian, similar to the surface of a football standing on end.
-What causes astigmatism?
Most astigmatism does not have a recognized cause, but merely is an anatomical imperfection in the shape of the cornea, in which the front curvature of the cornea is toric, rather than spherical.
Astigmatism is often associated with myopia (nearsightedness) or hyperopia (farsightedness). Astigmatism can increase in amount during the growing years.
In regular astigmatism, the meridians in which the two different curves lie are located 90 degrees apart. Most astigmatism is regular. In irregular astigmatism, the two meridians may be located at something other than 90 degrees apart, or there are more than two meridians.
A scar in the cornea, resulting from an injury or infection, or a disease called keratoconus may also cause astigmatism. This type of astigmatism is usually irregular.
- What are symptoms of astigmatism?
In an eye with astigmatism, vision is blurred due to the inability of the optical elements of the eye to focus objects into a sharp image on the retina. In astigmatism, a point of light is focused and perceived as a line, rather than as a point. Astigmatism makes it difficult to see fine details, both close-up or at a distance. Small amounts of astigmatism may not be noticed at all. Sometimes uncorrected astigmatism can lead to eye strain, eye fatigue, squinting, or headaches in addition to blurring and distortion of vision at all distances.
In an eye without astigmatism, the surface of the cornea is shaped like a ping-pong ball, where all the curves are the same. This is called a spherical surface. In an eye with astigmatism, the surface of the cornea is shaped more like a football, where there are two different surface curves located 90 degrees apart. This is called a toric surface.
-What are the different types of astigmatism?
There are various classification systems for astigmatism, based on the anatomical source of the astigmatism, the regularity/ irregularity of astigmatism, or the direction of astigmatism.
Most astigmatism in the human eye has its source within the cornea, although there are irregularities of the lens that can lead to astigmatism, known as lenticular astigmatism.
Most corneal astigmatism is regular, meaning that the cornea is most curved (steepest) 90 degrees away from the surface of the cornea that is the least curved (flattest) and that the transition from most curved to least curved surface occurs in a regular manner. Regular astigmatism can be corrected with glasses, soft lenses, rigid lenses, or refractive surgery.
Irregular astigmatism is defined as arising from any corneal surface that is neither spherical nor regularly astigmatic. Irregular astigmatism cannot be corrected with glasses or soft contact lenses.
A historical classification of astigmatism differentiates “with the rule” astigmatism from "against the rule" astigmatism. In with the rule astigmatism, the steepest curvature (most curved part to the cornea) lies in or close to the vertical meridian, similar to the surface of a football lying on it side. In against the rule astigmatism, the steepest (most curved) part of the cornea is in or close to the horizontal meridian, similar to the surface of a football standing on end.
-What causes astigmatism?
Most astigmatism does not have a recognized cause, but merely is an anatomical imperfection in the shape of the cornea, in which the front curvature of the cornea is toric, rather than spherical.
Astigmatism is often associated with myopia (nearsightedness) or hyperopia (farsightedness). Astigmatism can increase in amount during the growing years.
In regular astigmatism, the meridians in which the two different curves lie are located 90 degrees apart. Most astigmatism is regular. In irregular astigmatism, the two meridians may be located at something other than 90 degrees apart, or there are more than two meridians.
A scar in the cornea, resulting from an injury or infection, or a disease called keratoconus may also cause astigmatism. This type of astigmatism is usually irregular.
- What are symptoms of astigmatism?
In an eye with astigmatism, vision is blurred due to the inability of the optical elements of the eye to focus objects into a sharp image on the retina. In astigmatism, a point of light is focused and perceived as a line, rather than as a point. Astigmatism makes it difficult to see fine details, both close-up or at a distance. Small amounts of astigmatism may not be noticed at all. Sometimes uncorrected astigmatism can lead to eye strain, eye fatigue, squinting, or headaches in addition to blurring and distortion of vision at all distances.
6
Q
What is Myopia?
A
Nearsightedness, or myopia, as it is medically termed, is a vision condition in which close objects are seen clearly, but objects farther away appear blurred. Nearsightedness occurs if the eyeball is too long or the cornea, the clear front cover of the eye, has too much curvature. As a result, the light entering the eye isn’t focused correctly and distant objects look blurred.
People who are nearsighted have what is called a refractive error. This means that the light rays bend incorrectly into the eye to transmit images to the brain. In people with myopia, the eyeball is too long or the cornea has too much curvature, so the light entering the eye is not focused correctly. Light rays of images focus in front of the retina, the light-sensitive part of the eye, rather than directly on the retina, causing blurred vision.
-What Are the Symptoms of Myopia?
People who are nearsighted often complain of headaches, eyestrain, squinting or fatigue when driving, playing sports, or looking more than a few feet away.
How Is Myopia Treated?
Glasses, contact lenses, or refractive surgery can correct myopia.
People who are nearsighted have what is called a refractive error. This means that the light rays bend incorrectly into the eye to transmit images to the brain. In people with myopia, the eyeball is too long or the cornea has too much curvature, so the light entering the eye is not focused correctly. Light rays of images focus in front of the retina, the light-sensitive part of the eye, rather than directly on the retina, causing blurred vision.
-What Are the Symptoms of Myopia?
People who are nearsighted often complain of headaches, eyestrain, squinting or fatigue when driving, playing sports, or looking more than a few feet away.
How Is Myopia Treated?
Glasses, contact lenses, or refractive surgery can correct myopia.
7
Q
What is Exotropia also known as strabismus?
A
Strabismus, also known as crossed eyes, is a condition in which the eyes don't look towards an object together. One of the eyes may look in or out, or turn up or down. The eye turning can occur all of the time or only sometimes, such as during stressful situations or illness.
