Macular and Nerve Fiber Layer Thickness in Amblyopia The Sydney Childhood Eye Study Son C. Huynh, MBBS, MMed, 1 Chameen Samarawickrama, BSc(Med), MBBS, 1 Xiu Ying Wang, MB, MMed, 2 Elena Rochtchina, BSc, MAppStat, 1 Tien Y. Wong, MBBS, PhD, 3,4 Glen A. Gole, MD, 5 Kathryn A. Rose, PhD, 6 Paul Mitchell, MD, PhD 1 Purpose: To examine macular and peripapillary retinal nerve fiber layer (RNFL) thickness in amblyopia. Design: Population-based cross-sectional study. Participants: Of 4118 children examined in the Sydney Childhood Eye Study (incorporating the Sydney Myopia Study) from 34 randomly selected primary schools and 21 secondary schools from 2003 to 2005, 3529 (85.7%) were included in this analysis. The median age of the 2 samples was 6 years (n = 1395) and 12 years (n = 2134), respectively. Methods: A detailed eye examination was conducted on all children, including determination of best- corrected visual acuity (logarithm of the minimum angle of resolution [logMAR]), autorefraction (RK-F1 autore- fractor, Canon, Tokyo, Japan) after cyclopentolate (1%), cover testing to identify strabismus, and optical coherence tomography (StratusOCT, Carl Zeiss Meditec, Dublin, CA) through dilated pupils to obtain macula and peripapillary RNFL thickness. Amblyopia was defined as best visual acuity 0.3 logMAR units not explained by any obvious underlying eye or visual pathway abnormalities. Anisometropia was defined as an interocular difference of at least 1.0 diopter of the spherical equivalent refraction. Main Outcome Measures: Macular and peripapillary RNFL thickness. Results: Amblyopic eyes had slightly greater foveal minimum thickness than the normal fellow eye (by 5.0 m; 95% confidence interval 0.1–9.9) and right eyes of non-amblyopic children (by 10 m), both P0.05. This was more pronounced in 6-year-old children (6.9 m) than 12-year-old children (4.2 m). Amblyopic eyes also had slightly thicker central macula (1 mm diameter region) in both comparisons, although these differences were not statistically significant. The inner macular ring (outer radius 1.5 mm) was thinner in amblyopic than normal fellow eyes. Peripapillary RNFL thickness was not significantly different between amblyopic and normal fellow eyes or normal eyes of non-amblyopic children. Conclusions: In children aged predominantly 6 and 12 years, central macular thickness may be increased in eyes with amblyopia, although it is uncertain if this precedes or follows the development of amblyopia. No differences in peripapillary RNFL thickness were found when compared with normal eyes. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. Ophthalmology 2009;116:1604 –1609 © 2009 by the American Academy of Ophthalmology. Amblyopia is a visual disorder characterized by a reduction of vision that cannot be immediately improved by refractive correction or accounted for by clinically determined ana- tomic defects of the eye or visual pathway. Classic causes of amblyopia are strabismus, anisometropia, and form-vision deprivation. Each of these is thought to result in amblyopia via functional and morphologic effects on the visual cortex and lateral geniculate nucleus. 1 Evidence for direct retinal changes in eyes with ambly- opia has been controversial. 2–5 It has been hypothesized that amblyopia may affect the postnatal maturation of the retina, including the postnatal reduction of retinal ganglion cells, 5 which would lead to a measurable increase in retinal nerve fiber layer (RNFL) thickness in amblyopic eyes. However, although some studies have found increased RNFL thick- ness 5 in amblyopic eyes, others have found no significant differences. 6 The majority of previous studies, however, have been limited by relatively small sample sizes, 4,5,7,8 and few have also examined central macular thickness. 4,6 Optical coherence tomography is a relatively new technol- ogy that is increasingly being used for in vivo, high-resolution, cross-sectional imaging of the retina and optic nerve head. Its application in young children has been recently demonstr- ated. 9,10 This study examined the relationship between macular and peripapillary RNFL thickness and amblyopia in 2 large cohorts of children predominantly aged 6 and 12 years. Materials and Methods Study Population The Sydney Childhood Eye Study (incorporating the Sydney My- opia Study) was a population-based survey that examined child- 1604 © 2009 by the American Academy of Ophthalmology ISSN 0161-6420/09/$–see front matter Published by Elsevier Inc. doi:10.1016/j.ophtha.2009.03.013