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Title: Astigmatism

Author: Michael Murri, 4th Year Medical Student, Baylor College of Medicine

Astigmatism refers to a focusing power of the eye that is not symmetrical in all directions.1  There are many types of astigmatism.  One of the most common types is when the vertical and horizontal images of the eye are not focused together on the retina creating multiple points of focus (Figure 1A).  Different types of astigmatism can result in different types of horizontal, vertical, or otherwise irregularly blurred images on the retina (Figure 1B).2 Regular astigmatism refers to a consistent difference in two directions of the eye 90 degrees apart and can often be corrected through contact lenses or glasses.  Irregular astigmatism refers to complex patterns of irregularity and often requires refractive surgery such as LASIK or PRK or a gas permeable (or “hard”) contact lens to be corrected.

Figure 2: Representation of the refractive light path of horizontal and vertical light in one type of astigmatism known as mixed astigmatism (2A). Example of how the letter “H” might appear in different types of astigmatism (2B).


  1. Kee C-S. Astigmatism and its role in emmetropization. Experimental Eye Research. 2013;114:89-95. doi:10.1016/j.exer.2013.04.020.
  2. Read SA, Vincent SJ, Collins MJ. The visual and functional impacts of astigmatism and its clinical management. Ophthalmic and Physiological Optics. 2014; 34(3):267-294. doi:10.1111/opo.12128.
  3. Mozayan E, Lee JK. Update on astigmatism management. Current Opinion in Ophthalmology. 2014; 25(4):286-290. doi:10.1097/icu.0000000000000068.

Identifier: Moran_CORE_24063