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 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 leads to differences in vision. This is what the eye doctors use to determine the specific type of astigmatism that a person has.1

While the symptoms may be similar, the irregularity of the eyeball may differ according to which of the meridian/s are affected. To understand what the meridians are, think of the eye as a clock: Imagine a line running from 12 to 6 – this is one meridian. Then, imagine another line connecting 3 to 9 – this is the other meridian.2

These principal meridians are perpendicular to each other, and are the flattest and steepest meridians of the eye. Eye doctors will then examine these and use them to measure the curvature of the eye, which helps determine the particular type of astigmatism that may be available. The doctor will also identify if nearsightedness or farsightedness is 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.4 Here are the three primary types of astigmatism:5,6

  • 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.7
  • Hyperopic astigmatism. This type means that one or both of your principal meridians are farsighted. Same with 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 it 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.

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. Another cause of irregular astigmatism is keratoconus, an eye disease that leads to gradual thinning of the cornea.8

While regular astigmatism are 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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