Does an elevated cylinder power indicate astigmatism?

From the Guidelines

Yes, an elevated cylinder power in an eyeglass prescription indicates astigmatism, as it compensates for the irregular shape of the cornea or lens, causing light to focus on multiple points rather than a single point on the retina. Astigmatism is a common vision condition where the cornea or lens has an irregular shape, and it can be divided into corneal (or keratometric) astigmatism, lenticular astigmatism, and retinal astigmatism, with most astigmatism being corneal in origin 1. The cylinder component in a prescription specifically addresses this irregularity by compensating for the different curvatures in different meridians of the eye.

Key Points to Consider

• The higher the cylinder value (measured in diopters), the more significant the astigmatism, and this value is always accompanied by an axis measurement (0-180 degrees) that indicates the orientation of the astigmatism 1.
• Most people have some degree of astigmatism, and mild cases may not require correction, but when astigmatism causes blurred vision, headaches, or eye strain, corrective lenses with the appropriate cylinder power can help focus light properly on the retina, resulting in clearer vision.
• Regular eye examinations are important for monitoring changes in astigmatism over time, and refractive surgery options, such as toric IOLs, can also correct astigmatism, especially for larger amounts of preoperative corneal astigmatism 1.

Important Considerations for Astigmatism Correction

• Toric IOLs have been shown to provide lower amounts of residual astigmatism than nontoric IOLs, even when corneal relaxing incisions are used 1.
• The power of the toric component should be adjusted for the effective lens position of the IOL, and adding the contribution of the posterior cornea has been shown to improve outcome accuracy 1.

From the Research

Astigmatism and Cylinder Power

• Astigmatism is a common cause of blurred vision and asthenopia, and several different tests for its measurement have been described in the literature 2.
• Elevated cylinder power is often associated with astigmatism, as studies have shown that higher cylinder powers are associated with significant amounts of astigmatism 2, 3.
• The relationship between cylinder power and astigmatism has been investigated in various studies, with some finding that lower IOL cylinder powers are associated with significantly lower residual refractive astigmatism 4.

Measurement of Astigmatism

• Several tests for astigmatism have been compared, including the Jackson cross cylinder, Humphriss immediate contrast, and Pratt test, with results showing good reliability for each of the three methods 2.
• The AcrySof Toric intraocular lens has been shown to be effective in correcting corneal astigmatism, with studies demonstrating favorable efficacy, rotational stability, and safety results 3.
• High-cylinder toric intraocular lens implantation has been compared to combined surgery of low-cylinder intraocular lens implantation and limbal relaxing incision for high-astigmatism eyes, with results showing better clinical outcomes for the high-cylinder toric IOL implantation group 5.

Predicting Ocular Residual Astigmatism

• Studies have investigated the nature of ocular residual astigmatism in myopic patients and identified indicators to predict a patient's ocular residual astigmatism from corneal and ocular refractive data 6.
• Corneal astigmatism measured by true net power has been shown to be more representative of total ocular astigmatism than anterior corneal power, and total ocular spherical equivalent and total ocular astigmatism have been found to be significant correlates of ocular residual astigmatism 6.