Understanding the Difference Between Astigmatism and Myopia

Understanding Astigmatism and Myopia

Vision problems are very common, with myopia (nearsightedness) and astigmatism being two of the most prevalent issues. Although they share some similarities and often occur together, astigmatism and myopia are distinct conditions that affect vision in different ways.

What is Myopia?

Myopia, also known as nearsightedness or shortsightedness, is a refractive error that causes distant objects to appear blurry. It occurs when the eyeball is longer than normal or the cornea is too curved, causing light rays to focus in front of the retina rather than directly on it.

People with myopia typically have no problems seeing things up close, but objects farther away become progressively more blurred. Myopia usually develops in childhood and gets progressively worse through adolescence.

What Causes Myopia?

Researchers believe that both genetic and environmental factors play a role in the development of myopia. Some of the key risk factors include:

• Genetics - Studies show myopia tends to run in families. Having one or two myopic parents significantly raises a child's risk.
• Excessive near work - Spending long periods reading, using computers, smartphones or other near-vision activities may encourage the growth of a longer eyeball.
• Not enough outdoor time - Some research indicates a lack of exposure to natural daylight may influence myopia development.
• Urbanization - Myopia appears to be more prevalent in urban versus rural populations, perhaps due to lifestyle factors.

Symptoms of Myopia

The primary symptom of myopia is blurred distance vision. Other signs and symptoms may include:

• Headaches or eyestrain from visual effort
• Squinting or leaning forward to see distant objects better
• Difficulty seeing the board or presentations in school
• Trouble reading street signs or seeing cars until they are very close

Who Gets Myopia?

Myopia is extremely common, affecting around 30% of the American population. The rate is even higher in some Asian countries like Singapore, where up to 80% of young adults have myopia.

Myopia typically develops in school-age children between 6 and 14 years old. By adulthood, most myopes will have a prescription between -1.00 and -6.00 diopters.

Can Myopia Be Corrected?

The good news is that myopia can almost always be corrected with prescription lenses, either with glasses or contact lenses. Refractive surgery like LASIK can also be effective for permanently reducing dependency on glasses or contacts.

Unfortunately, myopia tends to gradually worsen over time, often by about -0.50 to -1.00 diopter per year during the teenage years. Periodic eye exams are necessary to monitor prescription changes.

Can Myopia Be Prevented or Controlled?

Although myopia cannot be completely prevented in predisposed individuals, some evidence suggests its progression may be slowed through lifestyle interventions like:

• Spending more time outdoors in natural daylight
• Taking frequent vision breaks during near work
• Correct use of bifocal lenses while reading
• Maintenance of healthy sleep and diet

Atropine eye drops are sometimes prescribed to children in Asian countries to slow myopic progression, but side effects include light sensitivity and reduced near vision. More research is still needed.

Understanding Astigmatism

Astigmatism is another common vision condition that affects focusing ability. It often occurs along with myopia, but can also happen on its own.

What is Astigmatism?

Astigmatism arises when the cornea or lens of the eye has an irregular curvature, causing light rays to focus at more than one spot. This results in blurred or distorted vision at all distances.

With normal vision, light focuses sharply on the retina at a single point. But with astigmatism, images focus on multiple points, resulting in visual distortion.

Types of Astigmatism

There are several types of astigmatism depending on where the irregularity occurs:

• Corneal astigmatism - Most common form arising from a curved cornea
• Lenticular astigmatism - Caused by irregularity in the lens inside the eye
• Mixed astigmatism - Involves corneal and lenticular components

What Causes Astigmatism?

The causes of astigmatism include:

• Irregular development of the cornea or lens
• Genetics
• Keratoconus - A disorder causing the cornea to thin and protrude
• Injuries, scars or infections involving the cornea
• Complications from surgery like LASIK or cataract removal

Symptoms of Astigmatism

Symptoms of astigmatism include:

• Blurry, distorted or fluctuating vision at all distances
• Eye strain, squinting, headaches
• Letters or lines appear blurry, overlapping or tilted
• Glare, light sensitivity, eyestrain with prolonged reading/computer use
• Difficulty reading blackboards or road signs

Types of Astigmatism Correction

Astigmatism can often be corrected with prescription eyeglasses or contact lenses. Other treatment options include:

• Toric lenses - Toric contact lenses that correct astigmatism may provide better vision than glasses.
• Refractive surgery - LASIK, PRK, and other surgeries can reshape the cornea to treat astigmatism.

Treatment choice depends on factors like the degree of astigmatism, eye health, and personal preferences.

Prevention and Control

There are no proven ways to prevent astigmatism. But wearing proper corrective lenses and maintaining healthy vision habits can help prevent eyestrain and symptoms.

Astigmatism often gets worse gradually. Regular eye exams allow early detection and treatment to maintain the clearest vision possible.

The Link Between Astigmatism and Myopia

Astigmatism and myopia are among the most prevalent vision disorders. Although they can occur independently, many people have both conditions together. Some key points about the relationship between astigmatism and myopia include:

• People with myopia often have astigmatism as well, especially those with higher myopia.
• Both conditions involve refractive errors in the focusing ability of the eye.
• Astigmatism arises from an irregularly shaped cornea or lens while myopia is due to an elongated eyeball.
• Genetic and environmental factors likely contribute to both astigmatism and myopia risk.
• Glasses, contacts, refractive surgery can correct both conditions in many cases.

It's common for people diagnosed with myopia to get an additional astigmatism prescription to optimize visual clarity. Similarly, managing astigmatism often involves assessing for any degree of accompanying myopia.

Treating Myopic Astigmatism

Myopic astigmatism, the combination of nearsightedness and astigmatism, is treated through corrective lenses or surgery to compensate for both refractive errors. Key management strategies include:

• Eyeglasses with lenses ground to specific myopic astigmatism prescriptions
• Soft toric contact lenses which correct for both myopia and astigmatism
• Refractive surgeries like LASIK and PRK which reshape the cornea to address both conditions
• Orthokeratology - Rigid contact lenses worn overnight to temporarily correct myopic astigmatism

Eye care providers determine the appropriate approach based on exam findings and the patient's vision needs and preferences. Periodic monitoring is important due to potential changes over time.

Conclusion

Astigmatism and myopia are common vision disorders that affect focusing ability. Myopia causes blurred distance vision, while astigmatism leads to distorted vision at all distances. The two conditions often occur together.

Understanding the difference between astigmatism and myopia is important for getting the right diagnosis and treatment. A comprehensive eye exam can identify refractive errors and guide management with corrective lenses or surgery to achieve the best possible vision.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.