Power Vector Analysis of Refractive and Corneal Astigmatism Components, and Their Time-dependent Change: The Funagata Study.

Abstract

Purpose: To investigate how refractive and corneal astigmatism changes over 5-years in Japanese adults.

Methods: In the Funagata study cohort, we recruited 541 Japanese participants (263 men, 278 women, aged 59.4 +/- 10.4 years) who had systemic and ophthalmologic examinations both in 2005-2007 and 2010-2012. Refractive and corneal astigmatism were evaluated using power vector analyses of orthogonal astigmatism (J0), oblique astigmatism (J45) components, and vector value amounts calculated with J0 and J45. Changes in J0, J45 and vector value amounts over time were examined using multiple linear regression models.

Results: The vector values in both refractive and corneal J0 declined over 5 years (P < 0.001), indicating that aging resulted more of the against-the-rule astigmatism. J0 declined level was not associated with age at baseline (P = 0.405, P = 0.941, respectively). Mean change in the vector value amount of both refractive and corneal astigmatism over 5 years were increased by 0.013 (95% confidence interval [CI] 0.010 to 0.016) and 0.013 (95% CI 0.009 to 0.016) per 1 year at baseline age (both P < 0.001). Vector value amount of refractive astigmatism increased with baseline refractive cylinder (0.179 unit per 1 diopter, 95% CI 0.128 to 0.231, P < 0.01), and amount of corneal astigmatism increased with baseline corneal cylinder (0.499 unit per 1 diopter, 95% CI 0.450 to 0.547, P < 0.01) after adjusting for age at baseline, gender, height and weight.

Conclusions: We found that astigmatism changes over 5 years. Aging causes larger changes in the vector value amounts of both refractive and corneal astigmatism following 5 years. Astigmatic changes toward the against-the-rule with aging progressed constantly both in refractive and corneal astigmatism. We showed that larger cylinders express larger changes in the vector value amounts following 5 years both in refractive and corneal astigmatism.

Keywords: 428 astigmatism • 414 aging: visual performance • 677 refractive error development