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Postnatal development of central corneal thickness in chicks of Gallus gallus domesticus
Fabiano Montiani-Ferreira1, Fernando Cardoso, Simon Petersen-Jones
1Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, D-208 Veterinary Medical Center, East Lansing, MI 48824-1314, USA.
Insights
Chickens show initial decreases in corneal thickness until 12 days, then a gradual increase, reaching stable corneal thickness by 70 days. No significant gender differences were observed in this Gallus gallus domesticus study.
Area of Science:
- Ophthalmology
- Comparative physiology
- Developmental biology
Background:
- Corneal development and maturation are crucial for visual function.
- Understanding species-specific changes in corneal thickness aids comparative ophthalmology.
- Previous studies have documented corneal thickness changes in dogs and humans.
Purpose of the Study:
- To investigate the changes in corneal thickness during the maturation of Gallus gallus domesticus (chick) eyes.
- To establish a timeline for corneal development in chicks up to 450 days of age.
- To identify potential influences of gender and eye laterality on corneal thickness.
Main Methods:
- Ultrasonic pachymetry was used to measure central corneal thickness (CCT) in 29 chicks from hatch to 450 days.
- Segmented regression analysis was applied to identify distinct phases of CCT change.
- Age, eye, and gender were included as factors in the statistical model.
Main Results:
- Mean CCT initially decreased, reaching a minimum around 12 days post-hatch.
- CCT then increased, stabilizing by 70 days of age at a plateau of 0.242 ± 0.0002 mm.
- No statistically significant differences in CCT were found between genders or between left and right eyes.
Conclusions:
- Chick corneal thickness undergoes an initial decrease followed by a plateau, similar to dogs and humans in the early phase.
- A unique characteristic in chicks is the sustained plateau in corneal thickness after 70 days.
- Unlike in humans and dogs, corneal thickness in chicks does not show gender-based differences.
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.
