Purpose
While evidence from cross-sectional studies suggests that choroidal thickness varies with age and refractive error in childhood, to date there have been no longitudinal studies examining changes in pediatric choroidal thickness. In this prospective study, the longitudinal changes in choroidal thickness and its relationship with eye growth were examined in a population of normal children with a range of refractive errors.
Methods
One hundred and one children (41 myopes and 60 non-myopes), aged 10-15 years participated in this study. For each child, 6 monthly measures of choroidal thickness (using enhanced depth imaging optical coherence tomography (OCT)) and axial ocular biometry were collected 4 times over an 18 month period. An experienced masked observer manually segmented all OCT images to derive subfoveal choroidal thickness measures. Linear mixed models were used to examine the longitudinal changes in choroidal thickness and the relationship between changes in choroidal thickness and axial eye growth over the study period.
Results
A significant increase in subfoveal choroidal thickness was observed over 18 months (mean increase 13 ± 22 µm, p<0.001). The myopic children (mean 299 ± 75 µm) exhibited significantly thinner choroids compared to the non-myopic children (mean 368 ± 76 µm) (p<0.001). There was no significant time by refractive group interaction (p=0.46), indicating a similar change in choroidal thickness over time in myopes and non-myopes. However, a significant predictor of the change in subfoveal choroidal thickness was the change in axial length over time (p<0.001, β = -0.14). This negative association indicates that children showing larger amounts of axial eye growth over the 18 months of the study exhibited greater subfoveal choroidal thinning (Figure 1), independently of the level of myopia.
Conclusions
A significant increase in choroidal thickness of normal children was found to occur over an 18 month period. Although myopic and non-myopic children on average both exhibited an increase in choroidal thickness, those children undergoing faster axial eye growth/myopia progression exhibited less thickening, or a thinning of the choroid. These findings support a potential role for the choroid in the mechanisms regulating eye growth in childhood.