The effect of anisometropia on stereopsis

Background and aim: For good stereopsis, the two retinal images should have similar clarity, shape, and size. Anisometropia is one of the factors which has affect on stereopsis. The purpose of this study was investigation of induced anisometropia effect on binocular function and stereopsis. Methods: In this semi experimental study, a total of 135 students from Zahedan University of Medical Sciences who had inclusion criteria were selected randomly. At the beginning of the work, the refractive errors of the subjects were determined and corrected with retinoscop and their stereopsis measured using T.N.O test. Subsequently, this hyperopic and myopic anisometropia induced by use of negative and positive spherical lenses (power 1, 2, 3 diopter) in trial frame in front of one eye and in each state stereopsis measured again. In agreement and against the rule astigmatic anisometropia induced by positive cylindrical lenses in 180 and 90 degree axes and stereopsis measured again. Data were analyzed by SPPS.14 software using within subjects factorial and repeated measurement ANOVA test. Results: This study showed that both type and amount of anisometropia had significant effect on stereopsis (P<0.001). The mean of stereopsis before intervention was (36.42±12.65). The most and least reduction of stereopsis were related to 3D hyperopic anisometropia (339.42±125.1) and 1D with the rule astigmatic anisometropia (36.57±12.6), respectively. The mean of stereopsis before and after different type and amount of induced anisometropia were significantly different (P<0.001). Conclusion: The result of this study showed that with increasing of anisometropia, stereoacuity decreases. Therefore, low degree of anisometropia, even 1D, can decrease both stereopsis and binocular function and thus, the amendment of stereopsis is necessary

The cross dominancy and structural disorders of head and vertebral column

زمینه و هدف: برتری متقاطع وجود چشم غالب در یک سمت و دست غالب در سمت دیگر بدن می باشد. این حالت می تواند سبب بروز اختلالاتی در وضعیت سر و ستون فقرات شود. هدف این مطالعه، بررسی ارتباط بین برتری متقاطع چشمی با ناهنجاری های ساختاری سر و ستون فقرات در دانشجویان دانشگاه علوم پزشکی زاهدان بود. روش بررسی: در این مطالعه توصیفی-تحلیلی،300 دانشجوی دانشگاه علوم پزشکی زاهدان به صورت تصادفی انتخاب و چشم غالب آنها با تست مایلز تعیین شد. سپس افراد به دو گروه با و بدون برتری متقاطع تقسیم شدند. وجود یا عدم وجود اختلالات ساختاری ستون فقرات و وضعیت قرار گیری سر با استفاده از صفحه شطرنجی و شاقول در دو گروه بررسی شد. داده ها با استفاده از آزمون کای دو تجزیه و تحلیل گردید. یافته ها: از 300 مورد، 76 نفر (3/25 ) دارای برتری متقاطع و 224 نفر (7/74 ) فاقد برتری متقاطع بودند. بین برتری متقاطع چشم و دست با اسکولیوزیس (001/0

The investigation of relationship between binocular vision status and migraine headaches

زمینه و هدف: با توجه به نتایج ضد و نقیض در مورد ارتباط بین سردردهای میگرنی و اختلالات دید دوچشمی، این مطالعه با هدف تعیین ارتباط بین برخی از پارامترهای دید دو چشمی با میگرن انجام شد. روش بررسی: در این مطالعه مورد- شاهدی، 30 نفر بیمار میگرنی که معیارهای ورود به مطالعه را داشتند به همراه 30 نفر بدون سردرد میگرنی مورد مطالعه قرار گرفتند. ابتدا بیماران با استفاده از پرسشنامه استاندارد سردرد غربال شده و تایید نهایی توسط نورولو‍‍‍‍‍‍‍‍‍‍‍‍ژیست انجام شد. عیوب انکساری به روش رتینوسکوپی تعیین و سپس نقطه نزدیک تقارب، تقارب پرشی، استریوپسیس، ذخایر فیوژنی، انحراف دور و نزدیک در دو گروه تعیین شد. داده ها با استفاده از آزمون های من- ویتنی و رگرسیون لجستیک تک متغیره و چندگانه تحلیل شد. یافته ها: میانگین استریوپسیس در گروه مورد و شاهد به ترتیب 82/33±17/154 و 1/26±0/49 ثانیه بر کمان بود و به ترتیب در گروه مورد و شاهد میانگین فوریای نزدیک 72/6±3/8 و 85/2±5/6، ذخایر فیوژنی مثبت دور 76/2± 7/10 و 07/5±07/6، ذخایر فیوژنی منفی دور 7/4±2/18 و 37/7±0/11، ذخایر فیوژنی مثبت نزدیک 49/4±5/16 و 72/8±97/13 و ذخایر فیوژنی منفی نزدیک 22/5±7/22 و 25/9±67/14 پریزیوم دیوپتر بود. متوسط متغیرهای فوق و تقارب پرشی در دو گروه تفاوت معنی داری داشت (05/0>P) ولی متوسط سایر متغیرها در دو گروه معنی دار نبود. در رگرسیون لجستیک چندگانه فقط تقارب پرشی، تقارب فیوژنی مثبت در دور و نزدیک در مدل باقی ماند (05/0

Visual Field Abnormalities among Adolescent Boys with Hearing Impairments

The aim of this study was to compare the visual field (VF) categorizations (based on the severity of VF defects) between adolescent boys with hearing impairments and those with normal hearing. This cross-sectional study involved the evaluation of the VF of 64 adolescent boys with hearing impairments and 68 age-matched boys with normal hearing at high schools in Tehran, Iran, in 2013. All subjects had an intelligence quotient (IQ) &gt; 70. The hearing impairments were classified based on severity and time of onset. Participants underwent a complete eye examination, and the VFs were investigated using automated perimetry with a Humphrey Visual Field Analyzer. This device was used to determine their foveal threshold (FT), mean deviation (MD), and Glaucoma Hemifield Test (GHT) results. Most (50%) of the boys with hearing impairments had profound hearing impairments. There was no significant between-group difference in age (P = 0.49) or IQ (P = 0.13). There was no between-group difference in the corrected distance visual acuity (P = 0.183). According to the FT, MD, and GHT results, the percentage of boys with abnormal VFs in the hearing impairment group was significantly greater than that in the normal hearing group: 40.6% vs. 22.1%, 59.4% vs. 19.1%, and 31.2% vs. 8.8%, respectively (P &lt; 0.0001). The mean MD in the hearing impairment group was significantly worse than that in the normal hearing group (-0.79 ± 2.04 and -4.61 ± 6.52 dB, respectively, P &lt; 0.0001), and the mean FT was also significantly worse (38.97 ± 1.66 vs. 35.30 ± 1.43 dB, respectively, P &lt;0.0001). Moreover, there was a significant between-group difference in the GHT results (P &lt; 0.0001). Thus, there were higher percentages of boys with VF abnormalities and higher mean MD, FT, and GHT results among those with hearing impairments compared to those with normal hearing. These findings emphasize the need for detailed VF assessments for patients with hearing impairments.Â

Induced vertical disparity effects on local and global stereopsis

Purpose: Although significant amounts of vertical misalignment could have a noticeable effect on visual performance, there is no conclusive evidence about the effect of very small amount of vertical disparity on stereopsis and binocular vision. Hence, the aim of this study was to investigate the effects of induced vertical disparity on local and global stereopsis at near. Materials and Methods: Ninety participants wearing best-corrected refraction had local and global stereopsis tested with 0.5 and 1.0 prism diopter (Δ) vertical prism in front of their dominant and non-dominant eye in turn. This was compared to local and global stereopsis in the same subjects without vertical prism. Data were analyzed in SPSS.17 software using the independent samples T and the repeated measures ANOVA tests. Results: Induced vertical disparity decreases local and global stereopsis. This reduction is greater when vertical disparity is induced in front of the non-dominant eye and affects global more than local stereopsis. Repeated measures ANOVA showed differences in the mean stereopsis between the different measured states for local and global values. Local stereopsis thresholds were reduced by 10s of arc or less on average with 1.0Δ of induced vertical prism in front of either eye. However, global stereopsis thresholds were reduced by over 100s of arc by the same 1.0Δ of induced vertical prism. Conclusion: Induced vertical disparity affects global stereopsis thresholds by an order of magnitude (or a factor of 10) more than local stereopsis. Hence, using a test that measures global stereopsis such as the TNO is more sensitive to vertical misalignment than a test such as the Stereofly that measures local stereopsis. © 2014 Informa Healthcare USA, Inc. All rights reserved: reproduction in whole or part not permitted

Corneal hysteresis and corneal resistance factor in pellucid marginal degeneration

Purpose: To evaluate and compare corneal hysteresis (CH) and corneal resistance factor (CRF) in pellucid marginal degeneration (PMD), keratoconus (KCN), and normal eyes using the Ocular Response Analyzer (ORA). Methods: In this retrospective study, corneal biomechanical parameters were measured in patients with PMD (n = 102) and KCN (n = 202) and normal subjects (n = 208) using the ORA. Data, including full patient history as well as the results of refraction, slit-lamp biomicroscopy, Pentacam HR (Oculus), and ORA (Reichert; Buffalo, New York, USA), were collected from medical records. Also, the data of only one eye per individual were selected for the analysis. The inclusion criteria for PMD and KCN groups were a reliable diagnosis of these ectatic disorders based on the clinical and corneal tomographic findings. CH, CRF, CH–CRF, intraocular pressure (IOP) measurements were assessed for each subject. Data were analyzed with SPSS and MedCalc using the ANOVA, Pearson Correlation, and receiver operating characteristic (ROC) curve analysis. Results: The mean CH was 8.91 mmHg ± 1.05 [standard deviation (SD)], 8.43 ± 0.78, and 10.89 ± 1.08 in the PMD, KCN, and normal group, respectively. Also, the mean CRF was 8.21 ± 1.35, 7.19 ± 1.11, and 10.69 ± 1.41 in the PMD, KCN, and normal group, respectively. ANOVA showed differences in the mean CH, CRF, and CH–CRF between three groups (P 1.3 mmHg for CH, CRF, and CH–CRF in the PMD group, respectively. For biomechanical parameters in PMD eyes, CRF had the highest sensitivity (75.49%) while the greatest area under the ROC curve (AUC) was seen for CH (0.903). Moreover, central corneal thickness (CCT) showed no correlation with CH (P = 0.30, r = −0.104) or CRF (P = 0.75, r = 0.033) in the PMD group. Conclusions: This study presented the values of corneal biomechanics for PMD using the ORA. The results of the ORA were markedly different between PMD, KCN, and normal eyes