Age-related changes in with-the-rule and oblique corneal astigmatism

To describe the age-related changes in with-the-rule (WTR) and oblique keratometric astigmatism (KA), posterior corneal astigmatism (PCA) and total corneal astigmatism (TCA).

We used a Pentacam HR (high-resolution) rotating Scheimpflug camera to determine the KA, PCA and TCA in the right eyes of 710 patients, aged from 20 to 88 years. The age-related changes along the vertical, horizontal and oblique meridians were analyzed with Naeser's polar value method in a cross-sectional study.

In the whole group, all meridional astigmatic powers and polar values were stable in the age groups from 20 to 49 years, followed by a 1.0 dioptre (D) against-the-rule (ATR) change in KA and TCA, and a 0.12 D reduction in against-the-rule PCA. A nasal rotation of the steep meridian in KA and TCA was noted in the 70-88 years old. The PCA averaged approximately 0.25 D ATR in all age groups. Females displayed the same early astigmatic stability as in the whole group, while male eyes demonstrated a linear decay from 1.5 D WTR at 20 years to 0.5 D ATR astigmatism for the oldest patients.

Corneal astigmatism is stable until the age of 50 years; thereafter both keratometric and total corneal astigmatism show a 0.25 D ATR change per 10 years. The average 0.25 D ATR PCA compensates the predominant keratometric WTR astigmatism in the younger patients and increases the TCA in the elderly with keratometric ATR astigmatism. The gender-based differences in age-related astigmatism require further studies.