Astigmatism prediction in small-incision lenticule extraction

Area of Science:

• Ophthalmology
• Refractive Surgery
• Corneal Surgery

Background:

• Small-incision lenticule extraction (SMILE) is a popular refractive surgery for myopia.
• Predicting and managing postoperative refractive astigmatism is crucial for visual outcomes.
• Objective astigmatism measurements are used to guide refractive surgery planning.

Purpose of the Study:

• To determine if preoperative objective astigmatism, measured by autorefraction, keratometry, and Scheimpflug tomography, can predict postoperative-induced refractive astigmatism after SMILE.
• To assess the correlation between different preoperative astigmatism measurements and the development of postoperative astigmatism.

Main Methods:

• A retrospective case series included 358 eyes of 358 patients who underwent SMILE for myopia without preoperative subjective astigmatism.
• Preoperative and 3-month postoperative examinations included subjective refraction, keratometry, autorefraction, and Scheimpflug tomography.
• Astigmatism was analyzed using double-angle plots and multivariate statistics.

Main Results:

• Postoperative subjective astigmatism was significantly different from preoperative objective astigmatism across all measurements.
• However, for eyes with postoperative refractive astigmatism ≥0.50 D, preoperative astigmatism measured by keratometry and Scheimpflug tomography was not significantly different.
• Preoperative objective astigmatism ≥0.50 D increased the risk of postoperative subjective astigmatism ≥0.50 D by 2.2 times.

Conclusions:

• Preoperative objective astigmatism cannot be directly interchanged with postoperative subjective astigmatism after SMILE.
• The presence of preoperative astigmatism ≥0.50 D significantly increases the risk of developing postoperative astigmatism.
• Clinicians should exercise caution during subjective refraction in patients with high preoperative objective astigmatism.