The Sydney Myopia Study is a survey of refractive errors and other eye diseases in a large sample of year 1 (6- to 7-year-old) and year 7 (12- to 13-year-old) schoolchildren. A 3-year follow-up will be conducted to reexamine these children at ages 9 and 15 years, respectively. The study was approved by the Human Ethics Committee of the University of Sydney and by the New South Wales Department of Education. The research adhered to the tenets of the Declaration of Helsinki. In the first phase, all children in year 1 classes were asked to participate. Written, informed consent was obtained from parents, and the children provided verbal consent on the day of the examination. Details of survey methods are described elsewhere.
22 In brief, 34 primary schools across the Sydney Metropolitan region were selected by using random cluster sampling, stratified on socioeconomic status, to provide a representative sample of Sydney schools. A proportional mix of public and private/religious schools was included.
Procedures included a 193-item questionnaire for parents asking for estimates of time spent by each child engaging in close-up activities and distance activities. Sociodemographic information, including ethnicity, country of birth, education, occupations, age of parents, and type of current housing were collected, in addition to the mother’s obstetric history, child’s birth history, past and current medical history, and a detailed family history of eye disorders. The examination included a detailed assessment of visual acuity, identification of amblyopia and strabismus, and cycloplegic refraction with cyclopentolate. Autorefraction and keratometry (with an RK F-1 autorefractor; Canon Inc., Tokyo, Japan), ocular biometry (axial length, anterior chamber depth, and corneal radius of curvature with the IOLMaster; Carl Zeiss, Meditec AG Jena, Germany), aberrometry (with a COAS aberrometer; Wavefront Sciences, Inc., Albuquerque, NM), retinal and disc digital photography, and retinal thickness measures (with a StratusOCT3 optical coherence tomograph; Carl Zeiss Meditec Inc., Dublin, CA) were obtained.
The eye drop protocol included amethocaine hydrochloride 0.5% (Minims; Chauvin Pharmaceuticals Ltd., Romford, UK), which was instilled into each eye to provide anesthesia and enhance the absorption of the subsequent eye drops; two cycles of cyclopentolate 1% (1 drop) and tropicamide 1% (1 drop) instilled 5 minutes apart. The autorefractometer (RK-F1; Canon) was set to generate five valid readings of refraction in each eye automatically, performed 20 to 30 minutes after instillation of the eye drops. This autorefractor provides a median value of the five readings, which was used for analysis.
An ocular biometry system (IOLMaster; Carl Zeiss Meditec) was used to obtain five valid readings of axial length and anterior chamber depth and three keratometry readings. The measures were taken on the entire cohort before the instillation of eye drops and on a subsample after pupil dilation. Predilation measurements for ocular biometry were used in this study. Postcycloplegia anterior chamber depth measurements are also reported.