An Unexpected Association between Childhood Hyperopia and Parental Smoking

1. An Unexpected Association between Childhood Hyperopia and Parental Smoking Dr Elaine YH Wong Ms Leanne Finch Dr Christine Chen Dr Lionel Kowal

2. Background • Effects of nicotinic antagonists on ocular growth and experimental myopia Stone RA, Sugimoto R, Gill AS, Liu J, Capehart C, Lindstrom JM Invest Ophthalmol Vis Sci. 2001 Mar;42(3):557-65 • 1-week old chicks, injected with nicotinic antagonists – Chlorisondamine & mecamylamine • Inhibition of ocular growth and shift of refraction towards hyperopia

3. Background • Childhood myopia and parental smoking. Saw SM, Chia KS, Lindstrom JM, Tan DT, Stone RA Br J Ophthalmol. 2004 Jul;88(7):934-7. • N=1334, 8-11 yo school children • Maternal smoking ? associated with hyperopic refraction in children (p=0.03; but only 1.7% of mothers smoked) • Paternal smoking is not associated with refractive error or axial length

4. Background • Associations between childhood refraction and parental smoking. Stone RA, Wilson LB, Ying GS, Liu C, Criss JS, Orlow J, Lindstrom JM, Quinn GE Invest Ophthalmol Vis Sci. 2006 Oct;47(10):4277-87. • N=323 from tertiary paediatric clinic • If one or both parents ever smoked, their children had a lower myopia prevalence (12.4% vs. 25.4%; P = 0.004) and more hyperopic mean refractions (1.83±0.24 vs 0.96±0.27 diopters; P =0.02) • Smoking by either parent during the mother’s pregnancy had a similar effect

5. Background Prevalence of hyperopia and associations with eye findings in 6- and 12-year-olds. Ip JM, Robaei D, Kifley A, Wang JJ, Rose KA, Mitchell P Ophthalmology. 2008 Apr;115(4):678-685. • N = 1765 (6 yo); N = 2353 (12yo) • Maternal smoking associated with moderate hyperopia in 6 yo but not 12 yo • Smoking during pregnancy – borderline significant with moderate hyperopia (p=0.055) • Not significant when controlled for ethnicity • Moderate hyperopia is significantly associated with amblyopia, strabismus, poor stereoacuity and abnormal convergence

6. The Pilot S tudy • Aim • To explore the relationship between hyperopia and parental smoking in a population who present to a subspecialty strabismus practice • Methods • Patients between the age of 0 -12 undergoing a cycloplegic retinoscopy were recruited • A short questionnaire was administered to the accompanying parent[s] • Information regarding parental smoking status, gestational smoking status, parental refractive error and ethnicity were collected

8. Results • N = 142 participants • Mild hyperopia (+0.25 - +1.75) = 59 • Moderate hyperopia (+2.00 - +5.75) = 59 • Severe hyperopia (>+6.00) = 15 • Myopia = 8 • Mean age = 5.29, SD = 2.99, range 0-12y • 52% female • 21% of mothers smoke; 16% smoked during pregnancy • 26% of fathers smoke; 32% smoked during pregnancy • 32% have either parent smoking now • 38% have a parent smoking during pregnancy

9. Results Adjusted for age & ethnicity

10. Discussion In this cohort… • Gestational smoking is NOT associated with hyperopia • Having a mother who is smoking now increases the odds of moderate to severe hyperopia (>+3 DS) by nearly 20 fold • Mother with myopia is protective of a child having > moderate hyperopia

11. Discussion • This is a biased population and a small sample • A larger study is required, hopefully from sources other than a private strabismus practice • Relationship of smoking, hyperopia and strabismus will need to be explored If anyone like to contribute patients, please contact Lionel Kowal (strabism@netspace.net.au) or Elaine Wong (e.wong@unimelb.edu.au)