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 Background and Aim: Optical blur due to refractive errors causes reducing retinal image quality and induces changes in how visual system responds. The purpose of this study is to evaluate the effect of myopic optical blur on visual cortex response by functional magnetic resonance imaging (fMRI). 

Materials and Methods: Five healthy volunteers with various degrees of myopia and age range 18-25 years (two females and three males) participated in this study. The results of functional magnetic resonance imaging of 18 emmetropic people (without refractive error) participated in a recent fMRI study with the same scanning conditions were applied as the control data. The functional scans were obtained by a Phillips scanner using a sine-wave grating visual task with spatiotemporal frequency of 2cpd/8Hz. The percentage of BOLD (Blood-Oxygen-Level-Dependent) signal change and number of activated voxels in different scan series were compared with each other after image processing.

Results: Non-linear reduction of visual cortex response due to increasing optical blur was observed in this study. The number of activated voxels and the percentage of BOLD signal change were both reduced in different amounts of myopia.

Conclusion: Considering the effect of optical blur on visual cortex responses in different amounts of myopia, it is better to provide the optimum optical correction during cognitive neuroscience fMRI research and FMRI study of neurologic diseases using patterned visual stimuli. 

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Background and Aim: Optic neuritis causes some deficits in visual function in the affected eye and there are some differences in these functions between the affected and unaffected eyes. The purpose of the study is to compare visual functions of both eyes to demonstrate the minimum and maximum value of affection in patients with acute unilateral optic neuritis.
Materials and Methods: Thirty patients (23 female, 7 male aged between 18 and 45 years) who 22 patients with retro-bulbar and 8 patients with anterior optic neuritis, enrolled in the study and their affected and unaffected eyes underwent visual function assessments. Visual acuity (VA), contrast sensitivity (CS), color vision (CV), and visual field (VF) (consist of MA and PSD) were examined for both eyes of all the patients and the significance of the differences between two eyes were calculated and compared by Independent T-test.
Results: According to our results, all the investigated visual functions consist of VA (t-test, t=7.29, P=0.00), CS (t-test, t=9.20, P=0.00), CV (t-test, t= -21.95, P=0.00), MD (t-test, t=5.29, P=0.01) except PSD (t-test, t=0.67, P=0.71) were affected by optic neuritis and there was a significant difference between the affected and unaffected eyes (P<0.01). The most significant difference were found for contrast sensitivity with letters (P=0.00) and there wasn`t any significance in the difference between two eyes for PSD parameter in VF (P=0.71).
Conclusion: Considering the most significant difference of contrast sensitivity between affected and unaffected eyes in patients with acute unilateral optic neuritis, it is suggested to pay more attention to the test in evaluating, diagnosis and follow up patients with acute unilateral optic neuritis.

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Abstract

Background and Aim: consider ing based on the presence or absence of swelling of the optic disc, optic neuritis classified nto two types of anterior and retrobulbar optic neuritis. The aim of this study was to compare the visual functions of patients with anterior optic neuritis and retrobulbar optic neuritis.

Materials and Methods:This cross-sectional study was conducted in 48 patients with optic neuritis including 35 patients (26 females) with retrobulbar optic neuritis and 13 patients (10 females) with anterior optic neuritis. Total cases aged ranging from 18 to 45 years old.The patients underwent clinical tests of visual functions, including visual acuity, contrast sensitivity and color vision. The collected data was recorded and statistical analysis was performed by SPSS software. The significance of the differences between two types of the diseases were calculated and compared by independent t-test.

Results: The anterior optic neuritis patients were slightly older than the retrobulbar optic neuritis ones (Average30.6yearsVs26.6years). Average defect to the visual functions was more severe in anterior optic neuritis in compare to retrobulbar. The visual functions of visual acuity (t=1.74, P=0.048) and color vision (t=-3.00, P=0.005) were significantly different between two types of the diseases. However, there was not a statistically significant difference (t=1.64, P=0.104) for contrast sensitivity as a visual function.

Conclusion: In the retrobulbar optic neuritis that there is not a specific appearance of fundoscopy ,the visual function of contrast sensitivity can be used as a helpful tool for primary diagnosis of the disease. especially

Key words: Anterior optic neuritis, etrobulbar optic neuritis, visual acuity, contrasts ensitivity ,colorvision.

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Background and Aim: Residual refractive error is one of the most common complications of keratorefractive surgeries including laser assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). This study aimed to determine the incidence rate and risk factors for re - treatment following photorefractive keratectomy (PRK) in patients with myopia and myopic astigmatism.

  

Materials and Methods: A case control study was performed on the surgical records of all eyes that underwent PRK from May 2009 to May 2012 at Farabi Eye Hospital by one surgeon. During this period, 70 eyes with indication for retreatment (cases) and 158 control eyes were identified. All of the eyes included in the study had refraction data at least 9 months post-operatively. Student t, Man-Whitney U and chi-square tests were used for univariate analysis of presumed associations. All variables with a P value of < 0.2 on univariate tests were entered in a multiple logistic regression to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for the risk factors of interest.

  

Results: Pre-op (pre-operative) manifests refraction spherical equivalent ≥-5.00 diopter, intended/nominal optical zone diameter of<6 mm and ocular fixational instability during surgery were associated with an increased risk of retreatment (all P values <0.001) and maintained their significance on multiple logistic regression with strong odd ratios of 6.12, 6.71 and 7.89 respectively. No statistically significant association was found between cases and controls in variables of age, sex, follow-up time, pre-op astigmatism, pre-op keratometry reading, pre-op pachymetry reading, pupil diameter and Kappa angle (all P values>0.05).

  

Conclusion: Small optical zone, deep ablation and unstable fixation during laser ablation are strong predictors for retreatment after photorefractive keratectomy.

  

Keywords: Re-treatment, Photorefractive keratectomy, Myopia, Myopic astigmatism

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Background and Aim : Vision plays an important role in maintaining balance in the body so that the visual defects produce some disturbances in the body balance. In order to establish balance, the first afferent signals to the brain are provided through the visual system. Therefor, diagnosis and treatment of visual disturbances are so most effective and important. This paper reviews the importance of the visual system in body balance control and visual disorders which affecting on balance.

  

Materials and Methods : In this study, the articles from 1989 to 2012 with issues of vision and body balance were reviewed. The research with medical subject heading terms and key words of “vision” and “balance” in Pub-med, Science Direct, Scopus, Iran Doc, Scholar Google, Iran Medex, Magiran were done.

  

Conclusion: Correction of visual disorders and improving vision in patients with balance disorders can hasten the healing process.

  

Keywords: Vision, Balance, Visual Disorders