Chromatic dispersion characteristics of optical fibers with near zero magnitude and slope is very important for such applications as optical transmission systems, dispersion compensation, and nonlinear optics. Theoretically-designed dispersion characteristics require a tolerance of AE2% to ensure reasonable dispersion accuracy during the fabrication process. This article describes dispersion accuracy of various photonic crystal fibers due to changes in dimension of the first ring of air-holes, as it is mostly responsible for the slope characteristics of the dispersion curves. It is demonstrated that for identical design parameters octagonal photonic crystal fibers can assume better dispersion accuracy in comparison to other configurations, such as hexagonal photonic crystal fibers, square photonic crystal fibers, and decagonal photonic crystal fibers in a 1.20 to 1.70 mm wavelength. Dispersion tolerance due to the dimension of the first ring of an optimized octagonal photonic crystal fiber is also investigated. It is found that the optimized octagonal fiber can also assume promising dispersion tolerance to dimension of the first ring with ultra-flattened characteristics in the 1.20 to 1.70 mm wavelength range.