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• #1 Astigmatism – Symptoms & causes – Mayo Clinic

  https://www.mayoclinic.org/diseases-conditions/astigmatism/symptoms-causes/syc-20353835

  Astigmatism occurs when either the front surface of the eye (cornea) or the lens inside the eye has mismatched curves. Instead of having one curve like a round ball, the surface is egg-shaped. This causes blurred vision at all distances. […] Astigmatism is a type of refractive error caused when either the cornea or the lens has mismatched curves. This makes vision blurry because there are two image points. […] Astigmatism may be present from birth, or it may develop after an eye injury, disease or surgery. Astigmatism isn’t caused or made worse by reading in poor light, sitting too close to the television or squinting. […] If either the cornea or the lens is egg-shaped with two mismatched curves, light rays aren’t bent the same, which means that two different images form. These two images overlap or combine and result in blurred vision.

• #2 Astigmatism – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK582142/

  Astigmatism is a common refractive error encountered in clinical practice. It nearly accounts for approximately 13 percent of refractive errors in the human eye. […] Various factors influence astigmatisms, such as eyelid pressure, the pressure of extraocular muscles, pupil size, and accommodation. […] The most common and important causes of astigmatism are keratoconus, posterior keratoconus, corneal scar, keratoglobus, pellucid marginal degeneration, Dellen, LASIK, photorefractive keratectomy, pterygium, rheumatic ulcer, shield ulcer, Mooren ulcer, microbial keratitis, herpetic keratitis, band-shaped keratopathy, vortex keratopathy, corneal edema, basement membrane dystrophy, lattice dystrophy, contact lens wear, contact lens warpage, post keratoplasty astigmatism, suture induced astigmatism, ptosis, cataract wound-related, radial keratotomy, trabeculectomy, glaucoma shunt procedure, penetrating injury, foreign body, chalazion, tumor, and capillary haemangioma.

• #3 Astigmatism – Symptoms & causes – Mayo Clinic

  https://www.mayoclinic.org/diseases-conditions/astigmatism/symptoms-causes/syc-20353835

  Astigmatism occurs when the cornea or lens is curved more steeply in one direction than in another. You have corneal astigmatism if your cornea has mismatched curves. You have lenticular astigmatism if your lens has mismatched curves. […] Risk factors for astigmatism include: Genetics. Astigmatism can be hereditary, meaning it’s passed down from parents. […] Astigmatism can happen after eye surgery.

• #4 Astigmatism: Symptoms, Tests & Treatment

  https://my.clevelandclinic.org/health/diseases/8576-astigmatism

  Astigmatism is usually caused by your cornea having an irregular shape. Eye care specialists call this corneal astigmatism. […] You can also have lenticular astigmatism, where the lens in your eye has an irregular shape. Lenticular astigmatism is often caused by cataracts. […] Astigmatism is usually hereditary, which means its a condition biological parents pass down to their children. It can also be caused by your eyelids putting too much pressure on your cornea. […] Some conditions and issues that can cause astigmatism include: Eye injuries. Keratoconus. Complications after eye surgery.

• #5 Astigmatism Treatments and Symptoms | UVA Health

  https://uvahealth.com/services/eye-care/astigmatism

  Theres no known precise cause of astigmatism. While some people have it at birth, others get it later in life due to injury or disease. Sometimes age itself is enough to create some degree of blurred vision. While it can occur with either near or farsightedness, it can also occur on its own. […] There are actually two types of astigmatism. In corneal astigmatism the cornea (the front surface of the eye) is misshapen. In lenticular astigmatism, the lens is misshapen. When light hits the irregular curve it refracts, causing the blurriness.

• #6 Astigmatism – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK582142/

  Apart from the causes listed above for astigmatism, the exact cause of spontaneous astigmatism is not clearly understood. Recent research indicates that genetic factors play an essential role in the development of astigmatism. […] Other factors contributing to astigmatism include pressure from the lids, extraocular muscle tension, and visual feedback.

• #7 Astigmatism

  https://www.aao.org/eye-health/astigmatism

  Astigmatism is caused by a cornea or lens that has a different shape than normal. Astigmatism is very common. Doctors don’t know why the shape of the cornea or lens varies from person to person. But they do know the risk of getting astigmatism is inherited (passed down from parents). […] People can also get astigmatism from: eye disease, eye injury, or after surgery. […] It is a myth that reading in low light or sitting very close to the television causes astigmatism or makes it worse.

• #8 Astigmatism | What is it, Causes and Treatment

  https://plano.co/eye-conditions/other-eye-conditions/astigmatism/

  Astigmatism, is a complex eye disease that can develop due to genetics and other factors such as an irregular shape of the cornea or lens or due to corneal diseases. […] Astigmatism occurs when light is bent differently depending on where it hits the cornea and then through the lens. In an eye with no astigmatism, the cornea or lens has equal roundness in all areas, like a soccer ball. In an eye with astigmatism, the cornea or lens is curved like a rugby ball, with some areas steeper or more rounded than others. […] Studies have identified 3 major genes that are collectively responsible for the development of astigmatism, but the exact gene has not been identified yet. In a study analyzing astigmatism in families, it was reported that children who have one parent or a sibling with astigmatism have a close to 50% increased risk of developing the condition themselves.

• #9 Astigmatism: Causes, Types, Symptoms & Treatment

  https://www.healthline.com/health/astigmatism

  Astigmatism is caused by unusual curvature in the eyes lens or cornea that prevents light from being focused into the focal point of the retina. This results in decreased vision or blurry vision. […] Its not known what causes astigmatism, but genetics is a big factor. Its often present at birth, but it may develop later in life. It may also occur as a result of an injury to the eye or after eye surgery. Astigmatism often occurs with nearsightedness or farsightedness. […] Sometimes, though, a rare condition called keratoconus causes astigmatism. This eye disease affects the cornea, causing the clear tissue on the cornea to thin and bulge out. This leads to cloudy or blurry vision, and sensitivity to bright lights. The cause of keratoconus is also unknown, but its believed to be hereditary, too. […] The exact cause of astigmatism isnt known, and treatment might be necessary depending on the extent of this eye condition.

• #10 Pathologic Causes of Irregular Astigmatism

  https://www.reviewofcontactlenses.com/article/pathologic-causes-of-irregular-astigmatism

  Keratoconus is the most common non-inflammatory corneal thinning disorder, but its certainly not the only one. Other thinning disordersincluding pellucid marginal degeneration (PMD), keratoglobus, posterior keratoconus and Terriens marginal degeneration (TMD)may closely resemble keratoconus, so a thorough examination is necessary in each case. […] Research estimates genetics contribute the majority (60%) of the risk. […] Besides genetics, common risk factors determined in the Collaborative Longitudinal Evaluation of Keratoconus study include eye rubbing (50%) and atopy (53%). […] Keratoconus generally develops in the second decade of life, along with myopia and regular astigmatism, and stabilizes in the fourth decade. […] Irregular astigmatism is less extreme than in other types of keratoconus. […] Progressive, against-the-rule irregular astigmatism may result in the need for rigid contact lenses or surgery. […] Non-inflammatory corneal thinning resulting in irregular astigmatism demands swift diagnosispreferably at a stage when no slit-lamp findings are presentand expedient intervention.

• #10 Pathologic Causes of Irregular Astigmatism

  https://www.reviewofcontactlenses.com/article/pathologic-causes-of-irregular-astigmatism

  Thin is inbut not in the cornea. Heres a rundown of non-inflammatory corneal thinning disorders that lead to irregular astigmatism. […] Discuss the prevalence of astigmatism in the population and how the changes that occur in astigmatism throughout life may provide some clues to the causes of astigmatism. […] Identify the involvement and interaction of genetic and environmental factors in the development of irregular astigmatism. […] Explain how corneal degenerationsnon-inflammatory corneal thinning disordersresult in irregular astigmatism. […] While the crystalline lens may be one source of the problem, irregular astigmatism is more often caused by the cornea. Of the corneal etiologies, keratoconus is the most common cause of primary irregular astigmatism (i.e., not caused by extraneous causes such as surgery or contact lens wear).

• #11 Etiology of Astigmatism – Optography

  https://optography.org/etiology-of-astigmatism/

  Astigmatism is defined as the optical condition of the eye where the power of refraction in two or more meridian differs. […] This is due to the presence of toroidal instead of spherical curvatures of the refracting surface of the eye and the change of curvature is gradual from one meridian to another and in uniform increments. […] Irregular astigmatism may be due to one or more of the several factors. […] Factors that may increase your chance of Astigmatism include heredity, a family history of astigmatism, a disease history of corneal scarring or thinning, low birth weight, advancing age, corneal scarring due to injury, corneal thinning, pre-existing refractive errors of the eye such as Myopia or Hypermetropia, severe allergies resulting in constant rubbing of the eyes, and diabetes.

• #12 What Is Astigmatism? Causes, Symptoms & Treatment

  https://www.visioncenter.org/refractive-errors/astigmatism/

  Astigmatism is a common and treatable eye condition that occurs when either the cornea or the lens has an irregular shape. […] The exact cause of astigmatism is unknown. However, genetics may play a role. Astigmatism is often present at birth, but some people develop it later in life. […] Factors that may cause you to develop astigmatism include: Eye injury, Eye disease such as keratoconus, Complications of eye surgery. […] Studies show these factors increase your risk for astigmatism: Older age, Eye injuries that cause corneal scarring or thinning, Eye surgery, such as cataract surgery or LASIK, Having a parent with astigmatism, Family history of eye disorders, Having a mother who smoked while pregnant, Having refractive errors (e.g., myopia and hyperopia).

• #13 Astigmatism: Symptoms, diagnosis and treatment | HealthPartners Blog

  https://www.healthpartners.com/blog/astigmatism-symptoms-treatment/

  One of the most common eye issues is astigmatism, which affects one in three people. […] Many different factors can cause astigmatism, though doctors and scientists dont know all the causes. Some people are born with it, and some develop it in childhood or adulthood. […] Many people with astigmatism are born with it because it can be passed down from parent to child through genetics. […] Injuries from contact sports, chemicals, fireworks and accidents can all cause eye trauma that can lead to astigmatism. […] Like with any surgery, theres a small risk of complications with eye surgery, though theyre rare. Some surgical complications can cause changes to the curve of the eye or affect your glasses prescription in other ways. […] This condition happens when the cornea is weak, so it bulges and takes on a cone shape. […] Cataracts are normal changes to the lens of the eye and are caused by proteins breaking down over time. Theyre a normal part of aging. As they develop, the eyes lens changes, and this can cause astigmatism.

• #14 Astigmatism | What is it, Causes and Treatment

  https://plano.co/eye-conditions/other-eye-conditions/astigmatism/

  A study analyzing refractive errors (myopia, hypermetropia, astigmatism) in premature infants (born earlier than 32 weeks of pregnancy) reported that 2 in 10 premature infants had astigmatism. This may be because the cornea did not have enough time to develop properly in the womb. Structural issues that affect the development of the cornea may also cause astigmatism. […] Keratoconus is an eye disease where the cornea gradually thins and changes to a cone shape. This can lead to irregular astigmatism. Keratoconus affects 1 in 2000 Americans. Keratoconus can be acquired, or it can also be inherited through genes. It was found that 1 in 10 people affected with Keratoconus has a parent with the disease. […] Rubbing the eyes too hard or too often might damage the cornea or lens of the eye. It can affect vision or lead to an infection that needs medical attention. Some people who have allergies experience itchy eyes, causing them to rub their eyes. Eye rubbing might also be a reflex or a habit. Rubbing the eyes hard enough to make them lose the roundness of its shape can damage the eyes over time and has been associated with the development of astigmatism in some cases.

• #15 Astigmatism | National Eye Institute

  https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/astigmatism

  Astigmatism happens when your cornea or lens has a different shape than normal. The shape makes light bend differently as it enters your eye, causing a refractive error. […] Doctors dont know what causes astigmatism, and theres no way to prevent it. Some people are born with astigmatism, but many people develop it as children or young adults. Some people may also develop astigmatism after an eye injury or an eye surgery.

• #16 Physiology of Astigmatism – EyeWiki

  https://eyewiki.org/Physiology_of_Astigmatism

  We know that the expression emmetropia is a conventional one and that in fact all normal human eyes have mild degrees of spherocylindrical errors (Shilo, 1997) or consist of a bitoric optical system, i.e. have principal meridians of relatively higher and lower powers at right angles. It is generally accepted that genetic factors have a significant role in determining ocular refractive status as well as astigmatism (Hammond et al., 2001) but many conditions and procedures such as surgery, suturing, wound healing, and ocular comorbidities modify the cylindrical status of the eye. […] A variety of factors change the magnitude and shift the meridians of these cylindrical components and the perceived subjective astigmatism throughout life. Astigmatism is an extremely dynamic phenomenon, and changes in the shape of optical interfaces, refractive index, optical aperture, eyeball-extraocular structures (eyelids and extraocular muscles) interaction, visual tasks, accommodation, binocularity, tear film status, and even body position induce and modify baseline ocular astigmatism.

• #17 What Causes Astigmatism?: ABC Children’s Eye Specialists: Ophthalmologists

  https://www.abckidseyes.com/blog/what-causes-astigmatism

  Astigmatism is often present at birth. In fact, most newborns have some degree of astigmatism, although it typically changes slowly and improves as the eye and vision skills develop over time. […] Other times, astigmatism doesn’t fully resolve, leaving kids with vision issues. Researchers aren’t sure why this type of astigmatism occurs, but they think it’s caused by specific genes. […] Astigmatism can also occur following an eye injury, infection or eye disease, or after eye surgery, particularly surgery involving the cornea. Note that you can’t develop astigmatism as a result of habits like watching too much TV, using a smartphone too much, or reading or doing other activities in low-light environments.

• #18 Physiology of Astigmatism – EyeWiki

  https://eyewiki.org/Physiology_of_Astigmatism

  The degree of astigmatism is even higher in preterm newborns and has an inverse association with postconceptional age and birth weight (Friling et al., 2004; Varghese et al., 2009). […] Several studies have suggested that corneal shape changes throughout life. The linear reduction of the astigmatism to lower values with age is apparently a part of normal eye maturation (Friling et al., 2004) and emmetropisation. […] It has been suggested that the high astigmatism in early life induces and activates accommodation (Campbell Westheimer, 1959; Howland, 1982). […] However, this is not always true, and a role for myopia development has been attributed to ocular astigmatism, as it may degrade optical blur cues and disrupt emmetropisation, which can lead to axial myopia progression in school-aged children (Gwiazda et al., 2000).

• #19 Physiology of Astigmatism – EyeWiki

  https://eyewiki.org/Physiology_of_Astigmatism

  In early adulthood, astigmatism of more than one diopter is infrequent and is still with the rule. […] Anterior corneal (and total) astigmatism shows flattening in the vertical meridian with aging, in contrast to a trend towards with-the-rule astigmatism on the posterior corneal surface (Ho et al., 2010). […] It has also been demonstrated that with-the-rule astigmatism decreases when eyelids are retracted from the cornea (Wilson et al., 1982). […] The contribution of the lens to the ocular astigmatism is relatively constant throughout life (Hofstetter Baldwin, 1957). Development of this lenticular astigmatism may be due to an emmetropisation phenomenon, as it effectively decreases manifest astigmatism in the early decades of life. […] The magnitude and axis of astigmatism vary during the day; this variation can be described with regard to changes in eyelid pressure, extraocular muscle tension, pupil size and accommodation.

• #20 Astigmatism Symptoms, Causes and Treatments | Fusion Eye Care

  https://www.fusioneyecare.com/eyecyclopedia/astigmatism/

  Astigmatism typically results because of an irregularly shaped cornea. […] Astigmatism may also be caused when the lens of the eye is not shaped correctly. […] Irregular astigmatism may be caused by several things including keratoconus which is a condition that causes the cornea to gradually get thinner, an eye injury or eye surgery.

• #21 Physiology of Astigmatism – EyeWiki

  https://eyewiki.org/Physiology_of_Astigmatism

  Changes in corneal contour exerted through eyelid pressure have been widely discussed since the mid-1960s, and transient bilateral monocular diplopia after near work due to temporarily induced toricity in the cornea has been reported by a number of investigators (Bowman et al., 1978; Golnik Eggenberger, 2001; Knoll, 1975; Mandell, 1966). […] The tear layer has a refractive index near to that of the cornea (1.33 versus 1.376) and refraction at the air-tear film interface accounts for the majority of refractive power of the anterior ocular surface (Oldenburg et al., 1990). […] This decouples anterior corneal astigmatism from internal astigmatism and manifests as residual astigmatism. The nature of this astigmatism is frequently against the rule and at times can cause eye strain (see above). […] An in-depth understanding of physiology of ocular astigmatism may throw light on the pathobiology of refractive errors and lead to new avenues for the prevention of clinically significant astigmatism.

• #22 Astigmatism: Causes, Definition, Types, Treatment

  https://www.allaboutvision.com/conditions/astigmatism/overview-of-astigmatism/

  Astigmatism is a condition caused by subtle flaws in the way your eye bends light (a process called refraction) that passes to the retina, the light-sensitive area at the back of the eyeball. […] Unfortunately, corneas and lenses may have imperfect curves that interfere with refraction, generating the fuzzy or distorted vision that we call astigmatism. Defects in other structures within the eye may also contribute to astigmatism. […] Astigmatism has three primary classifications, defined by the principal meridians (the steepest and flattest meridians of the eye). […] Irregular astigmatism is sometimes caused by injuries and scarring of the cornea. Keratoconus, a long-term thinning of the cornea, and some forms of eye surgery also can cause irregular astigmatism.

• #23 3 Types of Astigmatism: Myopic, Hyperopic & Mixed

  https://www.lasikplus.com/lasik-resources/what-is-lasik/three-types-of-astigmatism/

  Regular astigmatism occurs when the principal meridians are separated by 90 degrees on the 90° and 180° lines. An example being 180° / 90°. […] Irregular astigmatism, which is typically caused by a physical injury that caused scarring on the cornea, occurs when the principal meridians are not perpendicular to one another. […] Hyperopic astigmatism occurs when one or two principal ocular meridians focus light behind the retina (are farsighted). […] Myopic Astigmatism occurs when one or two principal ocular meridians focus light in front of the retina (are nearsighted). […] Mixed astigmatism occurs when one principal ocular meridian focuses light behind the retina (is farsighted) and the other principal ocular meridian focuses light in front of the retina (is nearsighted).

• #24 Astigmatism

  https://www.sifigroup.com/s/astigmatism?language=en_US

  Astigmatism is a vision condition characterized by the inability, at any distance, to focus on the retina the image of a dot when you are watching at a point object. […] In most cases astigmatism is caused by an imperfection in the curvature of the cornea (external astigmatism), but there can be also a form of “internal astigmatism” caused by imperfections in the crystalline lens or in the retina. […] Irregular astigmatism can result from an eye injury that has caused scarring on the cornea, from certain types of eye surgery or from keratoconus, a disease that causes a gradual thinning of the cornea. […] Astigmatism is often present at birth and may occur in combination with nearsightedness or farsightedness.

• #25 Astigmatism: MedlinePlus Medical EncyclopediaLock

  https://medlineplus.gov/ency/article/001015.htm

  Astigmatism is a type of refractive error of the eye. Refractive errors cause blurred vision. They are the most common reason why a person goes to see an eye professional. […] The cause of astigmatism is unknown. It is most often present from birth. Astigmatism often occurs together with nearsightedness or farsightedness. If astigmatism gets worse, it may be a sign of keratoconus. […] Astigmatism is very common. It sometimes occurs after certain types of eye surgery, such as cataract surgery.

• #26 Etiology of Astigmatism – Optography

  https://optography.org/etiology-of-astigmatism/

  Corneal astigmatism occurs when the cornea is curved more steeply in one direction than in another. It constitutes the most common cause of astigmatism. […] Acquired corneal astigmatism is also not infrequent, but it is often irregular. […] Lenticular astigmatism is comparatively rare. […] Index astigmatism is due to inequalities of refractive index of lens in different meridian in patients suffering from diabetes and those developing nuclear sclerosis and or cataract. […] Retinal astigmatism is due to oblique placement of macula. […] Astigmatism is a type of refractive error that occurs due to imperfections in the shape of the cornea, which alters the direction of the light and affects the clarity of our vision. […] You can also develop astigmatism as an adult due to an injury to your eye, or from an underlying eye disease such as keratoconus, which occurs when your cornea tissue thins out and bulges outward.

• #27 Causes Of Astigmatism | Cataractsurgerydesign

  https://www.cataractsurgerydesign.com/causes-of-astigmatism

  What Causes Astigmatism? […] There are three sources of astigmatism in the eye before cataract surgery: the anterior cornea, posterior cornea, and natural lens. […] The primary source of astigmatism is the anterior cornea. When the anterior cornea is steeper in one dimension than the other, astigmatism results. This occurs because the steeper dimension of the cornea bends light more than the less steep dimension. […] The second source of astigmatism is the posterior cornea. The posterior cornea also can have a different curvature in one dimension than the other. The axis of astigmatism of the posterior cornea may be the same as, oblique to, or opposite the axis of the anterior corneal astigmatism. Therefore, the total corneal astigmatism may be greater than, or less than, the anterior corneal astigmatism. The clinical astigmatism of the entire cornea may therefore be different in both axis and magnitude than the anterior corneal astigmatism.

• #28 Causes Of Astigmatism | Cataractsurgerydesign

  https://www.cataractsurgerydesign.com/causes-of-astigmatism

  The natural lens is the third source of astigmatism. Before surgery, astigmatism in your natural lens might affect your glasses prescription. This source of preoperative astigmatism disappears when the natural lens is removed during cataract surgery. […] Astigmatism present in the anterior cornea, posterior cornea, and natural lens determine the total refractive astigmatism of the eye before surgery. […] The natural lens is removed during cataract surgery. This leaves only two sources of astigmatism inside the eye after surgery: the anterior and posterior cornea. The main source of astigmatism is the anterior cornea.

• #29 What Causes Astigmatism to Worsen? | Henderson Vision Centre

  https://hendersonvision.com/what-causes-astigmatism-to-worsen/

  Astigmatism can be caused by either the cornea or the lens of your eye having an irregular shape. […] Astigmatism can present at birth. If you have a family history of astigmatism or ocular diseases like keratoconus, you may develop astigmatism. Rubbing, or placing too much pressure on your eyes can also cause astigmatism. […] Factors like age, eye injuries, or keratoconus can lead to worsened astigmatism. […] As we age, the cornea may change in shape and become more oblong. This can worsen existing astigmatism and may occur because of changes in our eye muscles. […] Eye injuries can occur in a variety of ways, the result of factors such as foreign objects in the eye, chemical burns, or blunt force trauma. […] Keratoconus is a progressive condition where the cornea bulges outward into a cone shape and becomes thinner and weaker. Keratoconus impacts vision because the cone-shaped distortion worsens astigmatism.

• #30 What Is Astigmatism? Symptoms, Causes, Diagnosis, Treatment, and Prevention

  https://www.everydayhealth.com/astigmatism/

  Astigmatism is usually caused by the shape of the cornea, says Dr. See. The cornea is the clear part on the front of your eye, the place where a contact lens would rest on your eye, he explains. Many people are born with astigmatism, but its unknown why, he adds. […] The shape of the cornea is very important; if the corneas shape is not perfect, your vision isnt going to be perfect, he says. What normally causes astigmatism is if the cornea is steeper in one direction than it is in the other direction, he says. […] The imperfect shape of the sphere causes things to be blurry images are not focused properly, says See. An astigmatism is one factor that can affect your vision; theres lots of components that can, but thats one of them, he says. […] Certain factors may increase a persons chances of having astigmatism, including a family history of astigmatism, eye disease, or keratoconus.

• #31 What Is Astigmatism? Symptoms, Causes, Diagnosis, Treatment, and Prevention

  https://www.everydayhealth.com/astigmatism/

  Keratoconus is a degeneration of the cornea in which the cornea thins in the lower and center parts. […] One main risk factor for keratoconus is rubbing your eyes, he explains. The mechanical injury from repeatedly rubbing your eye can sort of stretch out the cornea and cause it to lose its strength, he says. […] Allergies and sleep apnea increase the risk of keratoconus, says See. Its also common in people with Down syndrome because of increased rubbing of the eyes, he says. […] Some other things that raise the chance of astigmatism include: Some types of eye surgery, such as cataract removal, a history of corneal scarring or thinning, a history of severe nearsightedness or farsightedness, a mother who smoked during pregnancy.

• #32 What Causes Astigmatism to Worsen? | The Eye Care Team

  https://theeyecareteam.com/what-causes-astigmatism-to-worsen/

  Keratoconus is a vision disorder that causes the cornea to thin and form a cone shape, significantly distorting light and exacerbating astigmatism. […] The condition is believed to have genetic links. It may also relate to factors such as eye allergies, excessive eye rubbing, and connective tissue disorders.

• #33 Understanding Astigmatism: Causes, Symptoms, and Solutions | Zenni Optical Blog

  https://www.zennioptical.com/blog/astigmatism-causes/?srsltid=AfmBOooilphoaIrnXnAJJUd9FkFiln0V7ugf9SEbciWRiGGfRH7WcxBZ

  Astigmatism is a common condition that affects millions of people worldwide. It occurs when the cornea or lens of the eye is not perfectly round, causing blurred or distorted vision. […] Most cases of astigmatism are hereditary, which means it’s passed down from parents to children. Other factors like eye injuries, certain types of eye surgery, or health conditions that cause changes in the cornea can also lead to astigmatism. […] It’s important to note that astigmatism is not caused by squinting, reading in low light, or sitting too close to the TV – these are all eye health myths.

• #34 Astigmatism — Symptoms, causes, treatment

  https://www.ophthalmology24.com/astigmatism-symptoms-causes-treatment

  Astigmatism is caused by an irregularly shaped cornea, which causes the light to focus unevenly on the retina. […] If those curves on the cornea or the lens are mismatched, then light rays fail to bend correctly, causing a refraction error (refractive error). All of this causes an unfocused image to form on the retina. So overall, astigmatism is a type of impaired refraction of light. […] The condition can be present from birth, or it can develop after an eye disease, eye injury, or surgery. […] Astigmatism is NOT a disease and is NOT caused does not get worse by reading in poor light, sitting too close to the TV, or squinting. […] High degrees of astigmatism, as well as progressing astigmatism, or hard to correct with glasses may be caused by a condition called keratoconus.

• #35 Astigmatism: Causes, Test, Symptoms, Glasses, Surgery, Reversible

  https://www.emedicinehealth.com/astigmatism/article_em.htm

  Astigmatism is a vision problem that results due to abnormal curvature of the eye’s cornea or lens. […] Most astigmatism does not have a recognized cause other than merely an anatomical imperfection in the shape of the cornea, where the front curvature of the cornea is toric, rather than spherical. […] A small amount of astigmatism is considered normal and does not represent a disease of the eye. This type of astigmatism is extremely common and frequently is present at birth or has its onset during childhood or young adulthood. […] There is some hereditary basis to most cases of astigmatism, and most people with astigmatism have it in both eyes. […] Astigmatism is often associated with myopia (nearsightedness) or hyperopia (farsightedness). […] Astigmatism can increase in amount during the growing years.

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