Postnatal development of central corneal thickness in chicks of Gallus gallus domesticus

Objective To investigate the changes in corneal thickness that occur during maturation of the Gallus gallus domesticus chick eye over the first 450 days of life. Animals studied Twenty-nine chicks, of which 12 were males and 17 were females. Procedures The central corneal thickness (CCT) was measured by ultrasonic pachymetry from hatch until 450 days of age. Segmented regression was applied to capture the two phases observed in the CCT plotted against age. Eye and gender were also included in the model. Results Mean CCT values initially decreased, with the lowest point being reached at around 12 days of age. CCT then gradually increased as the chick matured. At 70 days of age the animals have completed corneal development and reached the plateau value of 0.242 +/- 0.0002 mm. CCT differences between gender or between left and right eyes were not statistically significant. Prediction equations for mean CCT according to the bird's age are presented. Conclusions There is an initial decrease in corneal thickness until approximately 12 days of age, which presumably mirrors maturation of corneal endothelial cell function. The pattern of changes in corneal thickness during the first phase of development of the chick CCT was similar to the one reported for dogs and humans. However, a unique feature of the development of CCT in chicks is that after reaching a plateau at 70 days corneal thickness did not significantly change over the remainder of the study period. Additionally, unlike in humans and dogs, there is no gender difference for corneal thickness in chicks.