We analyze the accuracy of a laser keratopographer in the evaluation of corneal topography for non-smooth corneal surfaces and when some noise is introduced into measured data. Through some numerical simulations, cosinesoidal deformations with different amplitudes and spatial periods are introduced on theoretical surfaces. Gaussian noise is introduced on the simulated x and y position coordinates for the measured position of the reflected beam in order to simulate detection errors that are due to vibrations or electric and other noise on the position-sensing detector. We found that the topography of the surface could be obtained with reliable accuracy if the height-to-width ratio of the deformations of the surface is smaller than 0.02 and the error in the detection of position at the position-sensing detector is under 0.5 mm.