Purpose:32 To describe corneal astigmatism in the UK Biobank population, to look for associations with other 33 biometric variables and socio-demographic factors, and to report the proportion with abnormal 34 keratometry and irregular astigmatism suggestive of pathological corneal ectasias such as keratoconus.35 Methods:36 Cross-sectional data were obtained from UK Biobank (www.ukbiobank.ac.uk/). A subsample of 107,452 37 participants from UK communities had undergone an enhanced ophthalmic examination including 38 autorefractor keratometry (Tomey RC 5000, Tomey Corp., Nagoya, Japan). After quality control and 39 applying relevant exclusions, data on corneal astigmatism on 83,751 participants was available for 40 analysis. Potential associations were tested through univariable regression and significant parameters 41 carried forward for multivariable analysis.
42Results:43 In a univariable analysis, the characteristics significantly protective against corneal astigmatism were 44 gender (male), older age, darker skin colour and increased alcohol intake (all p<0.001). The parameters 45 significantly associated with increased corneal astigmatism were older age at completion of full time 46 education, use of UV protection and lower corrected visual acuity. After inclusion in the multivariable 47 analysis, age, gender, age at completion of full time education, corrected visual acuity and skin colour 48 remained significant (all p<0.001). Increased corneal astigmatism was also found to be significantly 49 associated with amblyopia or strabismus. No individuals with abnormal keratometry or irregular 50 astigmatism were reported.
51
Conclusions:52 This analysis of associations with astigmatism in a large cohort of volunteers confirms previous 53 associations including adverse associations with younger age and female gender, and identified novel 54 associations including darker skin colour and frequency of alcohol intake. The highest risk group for 55 corneal astigmatism were younger females of lighter skin colour, having completed full time education 3 56 later, with higher logMAR corrected visual acuity. We also confirmed that corneal astigmatism is a high 57 risk factor for amblyopia and strabismus. Finally since no cases of keratoconus were identified, this 58 would suggest that simple keratometry indices may not be sufficient for population screening of 59 keratoconus. 60 Introduction 61 Uncorrected refractive error is the leading cause of moderate to severe visual impairment in all age 62 groups globally (101.2 million individuals in 2010), and the second commonest cause of avoidable 63 blindness in children after cataract (6.8 million individuals in 2010) [1][2]. Refractive error (ametropia), is 64 a significant public health burden, frequently associated with worse visual acuity and higher risk of 65 developing amblyopia (lazy-eye). Corneal astigmatism is a leading cause of refractive error in children 66 and a significant increase in myopia as well as astigmatism has been reported in the Singaporean 67 population...