Objective: Evaluation of corneal thickness and analysis of the factors related to the corneal thickness of patients seen at the National Eye Hospital. Methods: Measurement of central corneal thickness by ultrasound technique with Alcon pachymeter in patients aged from 18 without having acute ocular diseases. Results: The study was conducted in 274 patients (548 eyes), aged from 18 to 79. The average corneal thickness was 0.034 + or - 0.526 mm. Corneal thickness is associated with age (older patients have reduced corneal thickness) and corneal refractive power (the corneal thickness was highest in corneas of less 44 D and lowest in corneas of above 45 D), the difference is statistically significant (p 0.05). No significant difference of corneal thickness by gender, right or left eye, and axial length. Conclusion: Ultrasound measurement of corneal thickness is an essential exploration in in ophthalmology. It is necessary to perform the technique properly to ensure accurate measurements without affecting the cornea.