Abstract
Purpose: :
To study the distribution of peripapillary retinal nerve fiber layer (RNFL) thickness and optic disc parameters by ocular and demographic variables in young children.
Methods: :
The Sydney Childhood Eye Study is a population–based study of eye conditions in Australian children. 1765 children (78.9% of eligible) participated during 2003–4. Fast RNFL (3.4) and fast optic disc scans were performed using optical coherence tomography (StratusOCT, Zeiss). Cycloplegic autorefraction and axial length were also measured. Effects of gender, ethnicity, axial length and refraction were examined in multivariate analyses.
Results: :
Mean age was 6.7 years. RNFL average thickness was normally distributed with mean ± standard deviation (SD) of 103.7±11.4µm. It was thinnest in the temporal (75.7±14.7µm), followed by nasal (81.7±19.6µm), inferior (127.8±20.5µm), and superior (129.5±20.6µm) quadrants. Mean adjusted RNFL average thickness was greater in boys (104.7µm) than girls (103.2µm, p=0.007), and in East Asian (107.7µm) than Caucasian children (102.7µm, p<0.0001). Thinner RNFL was associated with increasing axial length (Ptrend<0.0001) and less hyperopia (Ptrend=0.004). Optic disc diameters and neuroretinal rim area were normally distributed. Disc horizontal and vertical diameters were 1.53±0.21mm and 1.79±0.28mm. Disc and neuroretinal rim areas were 2.20±0.39mm2 and 1.76±0.44mm2. Cup–disc (C/D) horizontal and vertical diameter ratios were 0.46±0.16 and 0.42±0.15, while area ratio was 0.22±0.13. There were no significant gender differences in both disc diameters and in cup, disc and neuroretinal rim areas and C/D area ratio. East Asian children had larger cup and disc areas, and C/D area ratios, but smaller neuroretinal rim area than Caucasian children. Larger disc (Ptrend<0.0001) and neuroretinal rim areas were associated with longer eyes (Ptrend=0.01). Disc (Ptrend=0.02) but not neuroretinal rim area (Ptrend=0.9) was smaller in more hyperopic eyes.
Conclusions: :
RNFL and disc parameters in young children compare well with adult values. There were marginal gender differences in RNFL thickness but not disc parameters. East Asian children had thicker RNFL, cup and disc areas, but smaller neuroretinal rim area. Effects of axial length on RNFL thickness and disc parameters were more marked compared to effects of refraction.
Keywords: nerve fiber layer • optic disc • topography