Astigmatism: Symptoms, Types, Causes and Treatment

Astigmatism is one of the most common refractive errors affecting people of all ages across the globe. Despite its prevalence, many are unaware of its symptoms, diverse types, underlying causes, and the broad spectrum of treatment options. This comprehensive guide draws on recent research to illuminate every major aspect of astigmatism, empowering you to better understand, identify, and manage this visual condition.

Symptoms of Astigmatism

Astigmatism can affect daily life in subtle or dramatic ways. Recognizing its symptoms is the first step towards seeking effective care. The experience varies from person to person, but there are hallmark signs that can indicate its presence.

Symptom	Description	Frequency/Prevalence	Sources
Blurred Vision	Vision appears smeared or unclear	Highly prevalent in astigmatism	1 2 3
Eye Strain	Discomfort or aching in the eyes	Common, especially with near work	1 2
Headaches	Pain in forehead/temples	Often after visual tasks	2
Dry Eyes	Sensation of dryness/irritation	Frequently reported	1
Watery Eyes	Excessive tearing	Sometimes present	1

Table 1: Key Symptoms of Astigmatism

Blurred or Distorted Vision

Blurred vision is the most recognizable symptom. People with astigmatism often describe print or objects as looking smeared, shadowed, or doubled. This is due to the eye's inability to focus light evenly onto the retina. The degree of blur often correlates with the severity of astigmatism 1 3.

Eye Strain and Discomfort

Tasks that require prolonged focus—like reading, screen work, or detailed handcraft—can lead to significant eye strain. Soreness, aching, or a sense of tiredness in the eyes is especially common in those with uncorrected astigmatism. Certain forms, such as "against-the-rule" astigmatism, are particularly prone to causing asthenopic (eye strain) symptoms 1 2.

Headaches

Persistent or recurring headaches, particularly after periods of intense visual concentration, are a frequent complaint. These headaches often present in the forehead or around the eyes and are linked to the eye muscles' extra effort to compensate for blurred vision 2.

Dry and Watery Eyes

Astigmatism is also associated with sensations of dryness or excessive tearing. This may result from prolonged squinting or eye strain, which upsets the normal tear film and blinking patterns 1.

Who Is Most Affected?

• People who spend long hours on near work (e.g., artists, students, office workers)
• Females may report more symptoms compared to males 1
• Symptoms can appear at any age

Types of Astigmatism

Astigmatism is not a one-size-fits-all condition. It comes in different types, determined by both the orientation and nature of the refractive error. Understanding these distinctions is vital for accurate diagnosis and optimal treatment.

Type	Description	Prevalence/Notes	Sources
With-the-Rule (WTR)	Steepest corneal curve vertical (90°±30°)	Most common in youth	5 6 7 4
Against-the-Rule (ATR)	Steepest curve horizontal (180°±30°)	Increases with age	2 5 6 7
Oblique	Steepest curve not at 90° or 180°	Less common	5 6 7
Regular vs. Irregular	Symmetry of corneal shape	Irregular less common	6 8

Table 2: Types of Astigmatism

Orientation-Based Types

With-the-Rule Astigmatism (WTR)

This type is characterized by a steeper vertical meridian (usually around 90°). It is the most frequent form in children, adolescents, and young adults 5 6. Over time, the prevalence of WTR decreases.

Against-the-Rule Astigmatism (ATR)

Here, the horizontal meridian (around 180°) is steeper. ATR becomes increasingly common with age, particularly in the elderly, as the axis of astigmatism shifts from vertical towards horizontal 2 5 7 11.

Oblique Astigmatism

Oblique astigmatism refers to cases where the steepest corneal curvature is neither horizontal nor vertical, but at an angle (between 30°–60° or 120°–150°). This type is the least common but tends to be associated with more complex corneal irregularities and visual disturbances 5 6 7.

Nature of Astigmatism: Regular vs. Irregular

• Regular Astigmatism: The principal meridians are perpendicular and can be corrected with standard lenses. Most astigmatism is regular.
• Irregular Astigmatism: The principal meridians are not perpendicular, often due to corneal scarring, keratoconus, or pterygium. This type is harder to correct and may require specialized lenses or surgical intervention 6 8.

Compound, Simple, and Mixed Astigmatism

• Simple Astigmatism: Only one principal meridian is focused on the retina, while the other is not.
• Compound Astigmatism: Both meridians are out of focus, either both in front (myopic) or both behind (hyperopic) the retina.
• Mixed Astigmatism: One meridian is myopic, the other hyperopic 3.

Age and Ethnic Variation

• WTR is more common in youth; ATR rises with aging due to corneal curvature changes 5 7 11.
• Ethnic differences exist; for example, Han Chinese students have a higher prevalence compared to other groups 5.

Causes of Astigmatism

The origins of astigmatism are complex and multifactorial. Genetics, environmental factors, age, and eye health all play roles in its development.

Cause	Mechanism/Details	Noteworthy Points	Sources
Genetics	Inherited corneal/eye shape	Strong familial trends	9 12
Corneal Shape	Curvature irregularities	Main factor in most cases	10 12
Eyelid Pressure	Mechanical distortion of cornea	Theoretical; some supporting data	9 12
Aging	Changes in corneal curvature/axis	WTR shifts to ATR with age	11 12
Visual Feedback	Abnormal emmetropization	May affect development in youth	9 10
Ocular Surface Disease	Scarring, pterygium, keratoconus	Leads to irregular astigmatism	8 9
Surgery or Trauma	Post-surgical or injury-induced changes	Can induce or worsen astigmatism	7 16 17

Table 3: Primary Causes of Astigmatism

Genetics and Heredity

Studies show a significant hereditary component to astigmatism. Family history, especially in parents or siblings, increases the likelihood of developing astigmatism 9 12. However, genetics alone do not explain all cases.

Corneal and Ocular Shape

The most common cause is an irregular shape of the cornea or lens, which leads to uneven focusing of light. Even small deviations from a spherical cornea can induce significant astigmatism 10 12.

Eyelid Pressure and Extraocular Muscles

Some theories suggest that chronic pressure from the eyelids or tension in the muscles surrounding the eye may influence corneal shape, contributing to astigmatism over time 9 12. This may explain why astigmatism can change with age or certain habits.

Age-Related Changes

As individuals age, the axis of astigmatism often shifts from vertical (WTR) to horizontal (ATR), likely due to gradual changes in the corneal curvature 11 12. This is a normal physiological process and is well-documented in large epidemiological studies.

Visual Feedback and Emmetropization

In developing eyes, visual experience and feedback can influence the growth and refractive shape of the eye (emmetropization). Abnormal visual input in childhood (e.g., from uncorrected astigmatism) can impact this process, potentially leading to persistent astigmatism 10.

Ocular Disease, Surgery, and Trauma

• Ocular Surface Disease: Conditions like keratoconus and pterygium can distort the cornea, causing irregular astigmatism. For example, pterygium creates traction and tear pooling, distorting the corneal surface 8.
• Surgery/Trauma: Cataract surgery, corneal surgery, or injury may induce or worsen astigmatism, especially if the corneal structure is altered 7 16 17.

Ethnic and Environmental Factors

Prevalence varies by ethnicity and environmental exposure, with some populations being more susceptible than others 5 9.

Treatment of Astigmatism

Astigmatism is highly treatable, with a range of options tailored to the severity and type. Advances in technology have made correction more precise and accessible than ever before.

Treatment Option	Approach/Description	Key Considerations	Sources
Spectacles	Cylindrical lenses to correct focus	First-line, simple & safe	1 3 4
Contact Lenses	Toric or rigid lenses for more precision	Good for irregular cases	4 13
Refractive Surgery	LASIK, PRK, SMILE, etc.	Permanent, effective	14 15 13
Cataract Surgery	Toric IOLs, relaxing incisions	Corrects astigmatism & cataract	16 17
Management of Disease	Treat underlying cause (e.g., pterygium)	Needed for irregular types	8

Table 4: Astigmatism Treatment Options

Spectacles

Prescription eyeglasses with cylindrical correction are the most common and non-invasive way to correct regular astigmatism. They are easy to use, customizable, and widely accessible 1 3.

Contact Lenses

For those desiring a wider field of view or more active lifestyle, contact lenses offer an excellent alternative. Toric soft lenses are designed specifically for astigmatism, while rigid gas-permeable (RGP) lenses can mask irregular corneal surface to some extent 4. For significant irregular astigmatism, specialty contact lenses may be required.

Refractive Surgery

Procedures such as LASIK, PRK, and SMILE reshape the cornea to correct astigmatism, often providing permanent results. SMILE, for example, has shown predictable and effective outcomes for low to high myopic astigmatism, but mild undercorrection and axis rotation can occur 14 15. Vector analysis during planning improves surgical accuracy 13.

Cataract Surgery and Astigmatism

Modern cataract surgery offers simultaneous correction of astigmatism. This is achieved using toric intraocular lenses (IOLs) or peripheral corneal relaxing incisions (PCRIs) at the time of surgery 16 17. Intraoperative aberrometry and refined techniques have further improved outcomes.

Treating Underlying Ocular Conditions

When astigmatism is caused by diseases such as pterygium or keratoconus, addressing the primary problem (e.g., surgical removal of a pterygium) is necessary to restore corneal shape and vision 8.

Choosing the Right Treatment

• Mild Astigmatism: Glasses or contact lenses
• Irregular/High Astigmatism: Specialty lenses or surgery
• Concurrent Cataract: Toric IOLs or relaxing incisions during cataract surgery
• Associated Ocular Disease: Treat underlying cause first

Conclusion

Astigmatism is a prevalent and highly variable refractive error that can cause significant visual symptoms and impact quality of life. Fortunately, treatments are effective and continue to evolve.

Key Points:

• Symptoms include blurred vision, eye strain, headaches, dry and watery eyes.
• Types are distinguished by axis (with-the-rule, against-the-rule, oblique), regularity, and complexity.
• Causes range from genetics and corneal shape to ocular disease, surgery, and aging.
• Treatment options are diverse: glasses, contact lenses, surgery, and disease management, with newer surgical techniques offering improved outcomes.

Understanding astigmatism empowers individuals to recognize symptoms early and seek the most suitable care, ensuring clear, comfortable vision at every stage of life.