Associations of birth weight with ocular biometry, refraction, and glaucomatous endophenotypes: the Australian Twins Eye Study.
OBJECTIVE
To examine the relationship of birth weight with ocular measures in a Caucasian twin population.


METHODS
Cross-sectional study of 1498 twins (308 monozygotic and 441 dizygotic pairs) aged between 5 to 80 years participating in the Australian Twins Eye Study.


METHODS
All participants underwent ophthalmic examination including bilateral cycloplegic autorefraction, keratometry, interpupillary distance (IPD), central corneal thickness, intraocular pressure (IOP), and retinal photography. Birth weight and gestation were obtained from a self-administered questionnaire. A subset of the twins also participated in the Tasmanian Infant Health Study (288) and the Childhood Blood Pressure Study (184), which collected data on birth parameters allowing for verification of data. Linear mixed models were used for the main analysis.


RESULTS
Both the within-pair (β(w) 0.27, 95% confidence interval [CI] 0.15, 0.38 mm per kg increase in birth weight, P < .001) and between-pair associations (β(B) 0.22, 95% CI 0.08, 0.35, P = .002) of birth weight with axial length were significant and of similar magnitude (difference in effect, P = .56), after adjusting for relevant confounders. In contrast, birth weight was negatively associated with corneal curvature (β(w) -0.82, 95% CI -1.09, -0.55 diopters per kg increase; β(B) -0.69, 95% CI -0.98, -0.41, both P < .001). These associations remained significant within dizygotic and monozygotic pairs. Refraction, anterior chamber depth, IPD, IOP, and optic disc parameters are unrelated to birth weight.


CONCLUSIONS
Consistent with previous studies in singleton children, lower birth weight is associated with shorter axial length and more curved corneas in this twin study. This also adds new insights into the emmetropization process.
Centre for Eye Research, University of Melbourne, Department of Ophthalmology, Royal Victorian Eye and Ear Hospital, Melbourne, Australia.
Cong
C
Sun
Anne-Louise
AL
Ponsonby
Shayne A
SA
Brown
Lisa S
LS
Kearns
Jane R
JR
Mackinnon
Julie M
JM
Barbour
Jonathan B
JB
Ruddle
Alex W
AW
Hewitt
Margret J
MJ
Wright
Nicholas G
NG
Martin
Terence
T
Dwyer
David A
DA
Mackey
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001315:Australia; D001699:Biometry; D001724:Birth Weight / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D058068:Endophenotypes; D005123:Eye / Q000033:anatomy & histology*; D005260:Female; D005901:Glaucoma / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012029:Refraction, Ocular / Q000502:physiology*; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D055815:Young Adult