Material and Methods: One hundred and eleven healthy children aged between 3 and 6 years were examined in this study. The children were measured by optical coherence thomography (OCT) before and after pupil dilation for macula and RNFL thickness, and optic disc parameters. The pupil sizes of the children were determined by the Scheimpflug camera before and after pupil dilation. The measurements taken before and after pupil dilation were compared statistically.

Results: One hundred and forty seven eyes of ninety four children were included in our study. The mean age of the children was 58.56±11.24 months (range: 34-78 months). The pupil size of the children before and after dilation was 2.76±0.50 mm (range: 1.5 mm- 4.57 mm) and 7.27±1.02 mm (range: 3.08 mm- 9.70 mm), respectively. There was a statistically significant difference between the values obtained before and after pupil dilation in the nasal inner, superior inner, and nasal outer macular segments (p<0.001; p<0.001 and p=0.046, respectively). The values before dilation were significantly different from those after dilation in the parameters of cup area, cup area/disc area ratio, vertical cup/disc ratio, and signal strength of optic disc scan (p=0.034; p= 0.036; p=0.005 and p=0.001, respectively). There was no statistically significant difference between the values before and after pupil dilation for all RNFL parameters.

Conclusion: In preschoolers, pupil size may partially affect the measurements of the macula and optic disc obtained by OCT-3 whereas the RNFL measurements are not influenced by pupil size. Keywords : Optical coherence tomography, pupil size, children