The prevalence of myopia in schoolchildren in Northeastern Iran is considerably lower than that of East Asian populations, but similar to many other populations, including South Africa, Chile and other countries of the Middle East. Whilst comparisons with other studies show that the prevalence of hyperopia and astigmatism in Northeastern Iran is higher than that of some countries, it is lower compared with others.

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To compare the corneal cone location on different maps and instruments and their agreements with elevation maps. Methods:In 90 left eyes with bilateral keratoconus, the apex of cone location was determined based on the maximum simulated keratometry (Kmax) location on the anterior sagittal curvature map by Pentacam HR, the maximum curvature on the mean curvature map by ATLAS 9000, most elevated point of the island of positive elevation relative to the best fit sphere on the front and back corneal elevation maps by Pentacam HR, and thinnest point on the thickness map by Pentacam HR and Orbscan, and the thinnest points on pachymetry and epithelial thickness maps by RTVue OCT.Results: There was a significant difference among the location on different maps along the xand y-axes (p< 0.001). The lowest agreement with the cone apex on both front and back elevation maps was for the anterior sagittal curvature map and the highest agreement for the Pentacam thickness map. The majority of keratoconus cone apexes were displaced in the inferotemporal direction on the different maps except for the epithelial thickness maps.Conclusions: Despite the variability between different devices and methods; the thickness map on the Pentacam HR showed the highest correlation with the front and back elevation maps, while the RTVue epithelial thickness map showed the poorest correlation. Based on this study, epithelial thickness maps and anterior curvature maps should be utilized with caution to determine the location of the cone.

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Objective The Müller-Lyer illusion is a visual illusion in which a horizontal shaft with an inward-pointing chevron (fins-out) affixed to each end is perceived longer than a shaft with outward-pointing chevrons (fins-in). The goal of this study was to compare the effects of experience and knowledge about the Müller-Lyer illusion on participants' perceptual precision. Method Participants were undergraduate students (n = 108) who were not familiar with the Müller-Lyer illusion prior to the experiment. The task of participants was to adjust one movable line to make it equal to the other in Müller-Lyer figure. They received ascending and descending Müller-Lyer trials in three blocks with 20 trials each. The Experimental Group received information about the Müller-Lyer illusion prior to the third block. Results For the Experimental Group, the amount of departure in Block 3 was reduced significantly compared with previous blocks. Conclusion Knowledge about the mechanisms underlying visual illusions may play an important role in helping individuals overcome them.