Discover the Different Types of Astigmatism

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  • While astigmatism is generally defined as having an irregularly shaped cornea, there can be varying differences in terms of the optical shape, which leads to differences in vision
  • This refractive error may also be identified as either regular or irregular. If you have regular astigmatism, it means that the principal meridians are 90 degrees apart, and are perpendicular to each other

You may be surprised to learn that there’s not just one type of astigmatism. While astigmatism is generally defined as having an irregularly shaped cornea, there can be varying differences in terms of the optical shape, which then affect where the meridians of your eye fall.1

While the symptoms may be similar, the irregularity of the eyeball may differ according to which meridians are affected. According to All About Vision:

“To understand what the meridians are, think of the front of the eye like the face of a clock: A line connecting the 12 and 6 is one meridian; a line connecting the 3 and 9 another.”2

These principal meridians are perpendicular to each other, and are the flattest and steepest meridians of the eye. Eye doctors will then examine and use these meridians to measure the curvature of the eye, which helps determine the particular type of astigmatism you have. The doctor will also identify whether nearsightedness or farsightedness is also present in the principal meridians, allowing them to accurately identify the type.3

The 3 Primary Astigmatism Classifications

By properly identifying the astigmatism, a more thorough treatment plan can be put in place, and the doctor can more specifically tailor the needs of each patient’s condition. Here are the three primary types of astigmatism:4,5

  • Myopic astigmatism — If you have this type, it means that either one or both of your principal meridians are nearsighted. If only one of your meridians is nearsighted, it means you have simple myopic astigmatism. If both are nearsighted, with one being more pronounced than the other, it means you have compound myopic astigmatism.6
  • Hyperopic astigmatism — This type means that one or both of your principal meridians are farsighted. Like myopic astigmatism, if only one of your meridians is farsighted, you have simple hyperopic astigmatism. If both are affected, with one being more severe than the other, then you have compound hyperopic astigmatism.
  • Mixed astigmatism — As its name implies, this means that one of the meridians is nearsighted, while the other is farsighted.

Here’s Another Way of Classifying Astigmatism

This refractive error may also be identified as either regular or irregular. If you have regular astigmatism, it means that the principal meridians are 90 degrees apart, and are perpendicular to each other. However, if the principal meridians are not perpendicular, it means that you have irregular astigmatism.

The majority of astigmatism cases are regular, meaning the front surface of the eye has a football-like shape. However, if caused by factors like an eye injury or eye surgery that led to cornea scarring, the astigmatism is usually irregular.7 Another cause of irregular astigmatism is keratoconus, an eye disease that leads to gradual thinning of the cornea.8

While regular astigmatism is usually corrected with glasses or contact lenses, irregular astigmatism cannot be addressed by these methods. It is not a normal condition, as those with this condition usually see double images or experience a general distortion of images. They may also complain of seeing a “starburst” effect.9

MORE ABOUT ASTIGMATISM

Astigmatism: Introduction

What Is Astigmatism?

Astigmatism Symptoms

Astigmatism Causes

Astigmatism Test

Types of Astigmatism

Astigmatism Treatment

Contact Lenses For Astigmatism

Astigmatism Prevention

Astigmatism FAQ



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