Introduction : Horizontal corneal diameter is one of the diagnostic factors in some ophthalmic diseases. At present American Newborn horizontal corneal diameter is considered as our normal value in Iranian ones, while it may be quite different in Iranian newborns. Early diagnosis is critical in some ophthalmic diseases such as congenital glaucoma and awareness of normal corneal diameter is essential to distinguish glaucoma patients as well as microcornea and megalocornea. To diagnose abnormal corneal diameter in Iranian population we should know Iranian normal value. Since horizontal corneal diameters in mature newborns are different from immature ones, we studied corneal diameter in normal Iranian newborns Materials & Methods: In this cross sectional descriptive analytic study, horizontal corneal diameters of 170 mature newborn eyes were measured with ruler and digital camera in Mustafa Khomeini and Hazrat-e-Zeinab hospitals. The data was analyzed using SPSS statistical software, t-test and Spearman’s correlation coefficient index. Results: In this study horizontal corneal diameter of 170 one day mature newborn (340 eyes) was evaluated. From these, 48.2% was from females (No: 82) and 51.8% was from males (No: 88).There was no significant difference between right and left eyes (p < 0.45), mean corneal diameter was 9.79±0.44 mm. It has been shown that there was statistical significant and direct correlation between horizontal corneal diameter and gestational age (p < 0.001) as well as birth weight (p < 0.02). On the other hand, There was no statistical significant difference about sex (p < 0.51), height (p < 0.11) and head circumference (p < 0.26). Conclusion: In this study we measured the Iranian mature newborn horizontal corneal diameter with ruler and digital camera. Of course this is not most exact method to measure the cornea but IOL master and Orbscan are not practical in newborns. In the other hand manual methods are not perfect, such as caliper and so on. In this study we found mean horizontal corneal diameter 9.79 mm that is in the range of American studies.
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