Changes in ocular astigmatism with age: A longitudinal study.

Purpose: To investigate changes in astigmatism with age. Are changes from with-the-rule (WTR) in younger ages to against-the-rule (ATR) in older patients mediated through oblique astigmatic axes or spherical prescriptions, and at what ages do these changes occur?

Methods: Prescription data were gathered retrospectively from one optical practice belonging to a large multiple group in the UK. Longitudinal assessments were made of the changes in astigmatism for 326 patients (mean age at first prescription 46 years, range 28-69 years) and 640 eyes through their recorded prescription history (median 20 years of prescription data per participant, IQR 19-22 years, range 18-29 years).

Results: Changes in small degrees of astigmatism (0.25 or 0.50 DC) from WTR to ATR were more than three times more likely to pass through an oblique cylinder axis as through a spherical prescription (56 vs. 16,  = 22.2, p < 0.0001). For patients aged 28-40 years at their first recorded eye examination, 55% (92/167) of eyes had an onset of astigmatic changes at a mean of 44 years (SD 6.2) and 41% (68/167) of eyes had no change until after a mean of 54 years (SD 4.6). Compared with a measured prevalence of oblique astigmatism in the literature of 11%-19%, 36% (232/640) of the eyes in this study had an oblique cylinder prescribed at least once in their refraction history and of these oblique cylinders, 78% were transient in nature.

Conclusions: The change in ocular astigmatism with age, from WTR to ATR, was more than three times more likely (56 vs. 16) to pass through oblique cylinder axes as through a spherical prescription. Changes in oblique astigmatism have been implicated in complaints with new spectacles, so given this prevalence of oblique cylinder axes (232/640, 36%), continuing professional development is needed regarding reconciling these oblique changes with previous prescriptions.