April 2026, Volume 4, Issue 4

Author

Padmanabhan Sundaram, Zakia Sugaina Mohammed, Divya Karupannasamy and Sundaram Devisundaram

Abstract

Introduction: Astigmatism results from the combined contribution of corneal and internal ocular components. Understanding the relationship between refractive astigmatism (RA), corneal astigmatism (CA), and ocular residual astigmatism (ORA) across different age groups is essential for optimizing outcomes in refractive surgery, toric intraocular lens implantation, and contact lens correction. Materials and Methods: This prospective cross-sectional study was conducted at a tertiary care hospital in South India from July 2023 to March 2024. A total of 150 eyes from 86 patients aged 10-59 years were included and categorized into five age groups. RA and CA were measured using automated refractometry and keratometry. ORA was calculated using power vector analysis as described by Thibos. Statistical analysis included descriptive statistics and Pearson correlation. Results: Refractive astigmatism was predominantly with-the-rule (WTR) in younger age groups (81% in 10-19 years) and shifted progressively to against-the-rule (ATR) in older age groups (76.9% in 50-59 years). Corneal astigmatism showed a similar age-related trend, with decreasing WTR and increasing ATR patterns. In contrast, ORA remained predominantly ATR (66%) across all age groups without significant age-related variation. ORA was found to compensate for corneal astigmatism in younger individuals and accentuate it in older individuals. Conclusion: Refractive astigmatism shows a significant age-related shift influenced primarily by corneal changes and modulated by ocular residual astigmatism. Accurate assessment of ORA is crucial for individualized refractive correction and improving surgical outcomes.