A Longitudinal Study of Corneal Astigmatism and Total Astigmatism

A review of astigmatism and its possible genesis

“…Generally, studies have shown that in young adults, WTR astigmatism occurs most commonly. 35,[37][38][39][40][41][42] With increasing age, a general shift in the axis of astigmatism is found from a predominance of WTR astigmatism (in adults younger than 40 years) to a predominance of ATR astigmatism (in adults older than 40 years). 35,[38][39][40]42,43 This shift in astigmatic axis in older age appears to be due to changes in corneal curvature.…”

“…35,[37][38][39][40][41][42] With increasing age, a general shift in the axis of astigmatism is found from a predominance of WTR astigmatism (in adults younger than 40 years) to a predominance of ATR astigmatism (in adults older than 40 years). 35,[38][39][40]42,43 This shift in astigmatic axis in older age appears to be due to changes in corneal curvature. [38][39][40]42 In a cross-sectional study of corneal and total astigmatism, Anstice 38 found that internal astigmatism remained relatively stable over time and that changes in astigmatism throughout life were due primarily to changes in corneal curvature.…”

“…35,[38][39][40]42,43 This shift in astigmatic axis in older age appears to be due to changes in corneal curvature. [38][39][40]42 In a cross-sectional study of corneal and total astigmatism, Anstice 38 found that internal astigmatism remained relatively stable over time and that changes in astigmatism throughout life were due primarily to changes in corneal curvature. Baldwin and Mills 39 investigated longitudinal changes in corneal and total astigmatism in patients over a 40-year period and found a steepening of the cornea and an increase in ATR astigmatism with aging.…”

Optics of Astigmatism and Retinal Image Quality

“… Irregular astigmatism, in which the principal meridians are not perpendicular to each other or there are other rotational asymmetries that are not correctable with conventional ophthalmic lenses. Many authors have measured the values and types of astigmatism exhibited by the human population (Baldwin & Mills, 1981;Kragha, 1986). There are various causes of change in eye astigmatism, including age and accommodation (Artal et al, 2002;Saunders, 1986Saunders, , 1988Atkinson, 1980;Gwiazda et al, 1984;Ukai & Ichihashi, 1991;Millodot & Thibault, 1985) and surgery (Bar-Sela et al, 2009;de Vries, 2009;Yao et al, 2006;Vilaseca et al, 2009a).…”

Possible optical, visual and behavioural effects of eyelids

“…Indeed, astigmatism is not classified as ametropia provided it does not exceed 0.5-1.0 dioptres (4)(5) . Teleologically speaking, physiological astigmatism may be useful, in some situations at least (6).…”