ABSTRACT
Color vision is one of the most important functions of visual system that has fundamental and considerable roles in visual data gathering, perceptual vision, visual information processing, correlation between different visual information and correlation with other senses. To investigate color vision, we need to understand color vision mechanism with respect to psychophysical findings. In this subject, retinal color vision mechanism and central nervous system play important function with each other, however, in different and parallel processes. For understanding this mechanism, we should focus on neuro-anatomy and neurophysiology of retinal cone cells, other retinal cells, color visual pathways, visual cortex, higher-order visual areas, and mechanisms that underlie the transformation from stimulus to perception. Most significant involved mechanism in color vision is the color opponency in visual system. Additionally, different types of neurons with its connections and other factors like contrast, luminance, brightness, boundary color and surround region color, color constancy, and etc., have many effects on color perception. In this systematic review, peer reviewed articles that published in PubMed from January 1970 to January 2015 have been searched, assessed and interpreted. Additionally, in this review, quantitative and qualitative peer reviewed evidences with regard to inclusion and exclusion criteria, have been gathered, summarized, discussed and concluded. The purpose of this study is to review the structure and function of visual system in color vision
ABSTRACT
Variations in sterioacuity may be used in an assessment of intermittent exotropia. Intermittent exotropia is divergent squint of eyes that is worsened due to daily visual tasks and its resultant tiredness therefore the amount of deviation increases. The purpose of this study is to determine the effect of daily work and resultant tiredness on near sterioacuity among intermittent exotropic patients. In this cross-sectional study, 600 dormitory students of Mashad University of Medical Sciences, ranging in age from 21 to 23 years, examined with alternate cover test to diagnose intermittent exotropic cases. 30 students had intermittent exotropia and along with 15 normal cases constituted the case-control group. Sterioacuity was measured twice, in the morning and at night, with Randot-SO 001 test. Suppression was checked with Bagoloni striate lens and 4 prism diopter base out test. Data were statistically analyzed with SPSS software [version 13]. The measured deviation in intermittent exotropic cases showed a significant difference between the deviation in the morning and late at night among 23.33% [7 cases] [P=0.00]. In addition, sterioacuity decreased significantly at night, [P=0.00] among these cases. Despite the increase in the deviation among 53.3% [16 cases] at night, steriacuity was not changed significantly. 23.33% [7 cases] did not show any changes in the morning and at night, both in deviation amount and sterioacuity measurement. In most intermittent exotropic cases, there is no significant correlation between intermittent exotropia and near sterioacuity variations after daily work and resultant tiredness [P<0.696]
ABSTRACT
To determine the prevalence rates of refractive errors in Mashhad, Iran. In this population-based study, random cluster sampling was performed on the urban population of Mashhad and of 4453 selected individuals, 70.4% participated in the study. Refractive errors were assessed using cycloplegic refraction in participants who were 15 years of age. The prevalence of myopia and hyperopia in individuals 15 years of age was 22.36% [95% CI: 24.66 to 20.06] and 34.21% [95 CI: 36.85 to 31.57], respectively. The prevalence of astigmatism and anisometropia were 25.64% and 5.84, respectively. Astigmatism and anisometropia were significantly more [p=0.005] and less [p=0.048] prevalent in females, respectively. Anisometropia, astigmatism and hyperopia were found to be increased with age. This study highlighted the valuable information on refractive errors in Mashhad. Hyperopia was the most common refractive error. In addition to subjects who were between 5 to 15 years of age, refractive errors were also prevalent among older people; therefore, more attention should be paid to the correction of refractive errors in these groups