A Quantitative Measurement of Ocular Rotation in Small Incision Lenticule Extraction: Double Marking of Corneal...

The small incision lenticule extraction (SMILE) has become a mainstream surgical procedure for correcting myopia and astigmatism. Nevertheless, the lack of an active cyclotorsion-tracking system prevents it from correcting rotational errors, which may compromise astigmatic correction accuracy. Evidence regarding the influence of intraoperative cyclotorsion on SMILE outcomes remains scarce, largely because of the unavailability of viable and dependable methods of measuring the degree of rotation during an operation. To address this gap, this protocol describes a novel corneoscleral double-marking technique to overcome a fundamental methodological limitation. It involves creating positional and dye-based marks on both the corneal and scleral surfaces, enabling direct observation and quantitative measurement of ocular rotation under a surgical microscope or a slit lamp. The primary goal of this protocol is to establish a standardized, objective approach for obtaining precise, quantitative data on cyclotorsion that has previously been inaccessible. The representative results of the statistical analysis of this data indicate that ocular rotation amplitude is an independent risk factor for residual astigmatism after SMILE surgery and has a significant impact on it (β = 0.520, P < 0.001). The analysis of astigmatism vectors also confirmed this. Therefore, the availability of this quantifiable data is pivotal. It provides an essential research tool to systematically investigate the specific impact of cyclotorsion in SMILE surgery. The measurements obtained are crucial for advancing studies on postoperative astigmatic outcomes, developing accurate predictive models for surgical accuracy, and refining treatment nomograms.