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SIA Vector Analysis and Keratometry Prediction in Temporal SICS with 350 µm Scleral Incision Depth
Prabhakar Srinivasapuram Krishnacharya1, Kedar Janardhan Prabhu1, Shreya Nataraj1
1Department of Ophthalmology, JSS Hospital, Mysore, Karnataka, India.
Romanian Journal of Ophthalmology
|August 10, 2026
Summary
A fixed 350 µm scleral incision depth resulted in a moderate surgically induced astigmatism (SIA) magnitude and minimal change in astigmatic axis. This standardization offers excellent postoperative keratometry prediction.
Area of Science:
- Ophthalmology
- Surgical Innovation
- Corneal Surgery
Background:
- Surgically induced astigmatism (SIA) magnitude and axis are influenced by sclera-corneal tunnel dimensions.
- Incision depth is often subjective, lacking standardization, which impacts astigmatic outcomes.
Purpose of the Study:
- To evaluate the SIA vector and centroid resulting from a fixed scleral incision depth of 350 µm.
- To assess the correlation between preoperative and postoperative keratometry and the predictability of outcomes.
Main Methods:
- 42 patients underwent scleral incisions of 350 µm depth.
- Preoperative and postoperative keratometry measurements were taken.
- Pythagorean theorem and keratometric data were used to determine SIA vector and centroid.
Main Results:
- A statistically significant difference in vertical keratometry was observed (p < 0.0009).
- The mean SIA magnitude was 2.05 (± 1.75) D, with a centroid at 22.3º.
- High prediction accuracy for postoperative keratometry was achieved (R² = 0.93 for horizontal, 0.74 for vertical).
Conclusions:
- A standardized 350 µm scleral incision depth leads to a moderate SIA magnitude and minimal astigmatic axis shifts.
- This approach provides a reliable method for predicting postoperative keratometry.
- Further research into scleral incision depth as a determinant of astigmatic outcomes is warranted.