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Clair Enthoven, Willem Tideman, Jan Roelof Polling, Virginie JM Verhoeven, Caroline Klaver; Increase of axial length in eyes with high corneal astigmatism.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2399.
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© ARVO (1962-2015); The Authors (2016-present)
Multiple studies have concluded that astigmatism is associated with ametropia. This study explores the association between corneal astigmatism and axial length increase in young children.
A total of 4491 children from the birth-cohort study Generation were included. Participants received an ophthalmic examination including measurements of axial length and corneal radius of curvature at 6 and 9 years. Corneal astigmatism was defined as >1.25 D. Axial length was divided into short (< 22 mm), medium (22 - 24 mm) and long (> 24 mm). The axial length corneal radius ratio (AL/CR) was divided into tertiles. Analyses were based on data from right eyes. Paired samples T tests, Chi-square tests and linear regression were performed to investigate the relationship between axial length, AL/CR and corneal astigmatism.
The mean age at first visit was 6.1y (SD 0.46), at second visit 9.8y (SD 0.32); and 50.6% were female. Mean corneal astigmatism was 0.85 D (SD 0.55) at first visit and 0.84 D (SD 0.50) at the second visit. The prevalence of corneal astigmatism was 16.2% at 6 years and 15% at 9 years. Mean axial length increased from 22.35 mm (SD 0.73) at 6 years to 23.11 mm (SD 0.84) at 9 years (p<0.001). Mean AL/CR increased from 2.88 (SD 0.08) at age 6 to 2.97 (SD 0.09) at age 9 (p<0.001). At age 6, corneal astigmatism was 21.8% in eyes smaller than 22 mm, 13.4% in eyes between 22 and 24 mm and 23.5% in eyes larger than 24 mm (χ2=51.22, p<0.001). At age 9, this was 26.6%, 13.8% and 14.9% respectively (χ2=40.68, p<0.001). Regarding AL/CR at age 6, corneal astigmatism was 18.4% in the small AL/CR group, 12.5% in the medium AL/CR group and 17.4% in the large AL/CR group at age 6 (χ2=20.68, p<0.001). At age 9, this was 15.7%, 11.8% and 17.5% respectively (χ2=19.56, p<0.001). Corneal astigmatism at age 6 was significantly associated with increase of axial length at age 9 (beta 0.018, p=0.05), and with increase of AL/CR at age 9 (beta 0.008, p<0.001).
This study shows that corneal astigmatism is more common in eyes with a short and a long axial length, and in eyes with a small and large AL/CR. The increase of axial length and AL/CR at age 9 years was larger in children with higher corneal astigmatism at age 6.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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