From the Guidelines
The optimal threshold for astigmatism correction should be between 0.25 D to 5.00 D, with the understanding that higher target astigmatism results in weaker correction effects after surgery. This recommendation is based on the most recent evidence from 2025, as outlined in the study published in the journal Ophthalmology 1. The study suggests that correcting astigmatism within this range can achieve better results after surgery, especially when using auxiliary positioning techniques such as axis alignment and cyclotorsion compensation.
When considering the thresholds for astigmatism correction, it's essential to weigh the balance between specificity and sensitivity. The evidence suggests that:
- Correcting astigmatism with axis alignment and cyclotorsion compensation can improve outcomes after surgery 1
- Higher target astigmatism may result in weaker correction effects, implying a need for careful consideration of the correction range 1
- The use of auxiliary positioning techniques can minimize alignment error and improve the accuracy of astigmatism correction, particularly in cases with large cyclotorsion angles 1
In clinical practice, the thresholds for astigmatism correction may need to be adjusted based on individual patient factors, such as symptoms and visual acuity. However, the evidence from the 2025 study provides a foundation for determining the optimal correction range, with the goal of optimizing specificity without losing sensitivity 1.
From the Research
Thresholds for Astigmatism
The thresholds for astigmatism that optimize specificity without losing sensitivity are not explicitly stated in the provided studies. However, some studies provide information on the levels of astigmatism that are considered significant and the factors that influence the decision to correct astigmatism.
- A study published in 2023 2 found that patients with corneal astigmatism of less than 0.75 diopters (D) may not require astigmatism correction, but those with against-the-rule (ATR) astigmatism should be considered for correction when using a 135° incision.
- Another study published in 2021 3 noted that more than 40% of patients undergoing cataract surgery have 1 diopter (D) power or more of astigmatism, which is visually significant if left untreated.
- A study published in 2000 4 suggested that surgeons should be less aggressive with patients with with-the-rule and against-the-rule astigmatism and more aggressive with oblique astigmatism.
Factors Influencing Astigmatism Correction
Several factors influence the decision to correct astigmatism, including:
- The magnitude and orientation of the astigmatism
- The presence of other refractive errors, such as myopia or hyperopia
- The type of surgical procedure being performed
- The use of toric intraocular lenses (IOLs) or other corrective measures
Measurement and Calculation of Astigmatism
The measurement and calculation of astigmatism are critical in determining the need for correction. Studies have shown that:
- Corneal astigmatism is a common condition, with over 60% of individuals having more than 0.50 D of astigmatism 5
- Posterior corneal astigmatism is an important component of total corneal astigmatism 5, 2
- The use of advanced imaging technology and software can improve the accuracy of astigmatism measurements and calculations 3