An Unexpected Association between Childhood Hyperopia

and Parental Smoking

Dr Elaine YH Wong

Ms Leanne Finch

Dr Christine Chen

Dr Lionel Kowal

Background

• Effects of nicotinic antagonists on ocular growth and experimental myopiaStone 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 shifting refraction toward hyperopia

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 is suggestive of being

associated with hyperopic refraction in children (p=0.03; but only 1.7% of mother smoked)

– Paternal smoking is not associated with refractive error or axial length

Background

• Associations between childhood refraction and parental smoking. Stone RA, Wilson LB, Ying GS, Liu C, Criss JS, Orlow J, Lindstrom

JM, Quinn GEInvest 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

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

The Pilot Study

• 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

Associations between Childhood Refraction and Parental Smoking

Patient’s cycloplegic refraction: Right Eye: _______________________ Left Eye: ___________________________ QUESTION 1. Parents’ race (please tick): Father: Caucasian______Asian: ______ Mother: Caucasian: ______ Asian: ______ Other (please write): _____________ Other (please write): ______________ QUESTION 2. Are either of the patient’s parents long or short-sighted (tick which)? Father: hyperopic _____ Mother: hyperopic _____ myopic _______ myopic _______ unknown: _____ unknown: _____ QUESTION 3. Do either of the patient’s parents smoke? Father: yes / no / former smoker Mother: yes / no / former smoker If both parents answered no to question 3, the questionnaire is now complete. QUESTION 4. If yes, how long have you smoked for? Father 1: _______ years Mother: _______ years QUESTION 5. Did you smoke during the patient’s gestation? Father: yes / no Mother: yes / no QUESTION 6. If you have since quit, at what age was the patient when you stopped? Father: ________ years Mother: _________ years

Patient Label

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 0-12yo• 52% female• 21% mother smoke; 16% smoked during pregnancy• 26% father smoke; 32% smoked during pregnancy• 32% have either parent smoking now• 38% have parent smoking during pregnancy

Results

Adjusted for age & ethnicity

Odds Ratio 95% CI Significance

Parental Smoking 0.25 0.03-1.99 0.19

Father Smoking 1.77 0.15-20.50 0.65

Father ExSmoking 2.44 0.43-13.95 0.32

Mother Smoking 19.75 1.65-236.51 0.02

Mother ExSmoking 3.90 0.66-23.08 0.13

Gestational Smoking 2.02 0.11-36.15 0.63

Father Smoking 0.42 0.02-8.96 0.58

Mother Smoking 0.11 0.01-0.18 0.07

Refraction

Father hyperopia 0.94 0.22-3.96 0.93

Father myopia 0.59 0.21-1.68 0.32

Mother hyperopia 2.09 0.56-7.79 0.27

Mother myopia 0.32 0.13-0.80 0.02

Discussion

• 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 folds

• Mother with myopia is protective of a child having > moderate hyperopia

Discussion

• This is a biased population and a small sample• Larger study will be 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)