Simultaneous pattern visual evoked potential and pattern electroretinogram in strabismic and anisometropic amblyopia

Amblyopia is a relatively common condition in which visual acuity through an eye is subnormal despite no overt pathology. Pattern visual evoked potential [PVEP] can detect any defect from optic nerve to occipital cortex and pattern electroretinogram [PERG] can detect retinal defects specially the ganglion layers. This study was performed to evaluate the cortical and retinal activity in strabismic and anisometropic amblyopia. PVEP and PERG were recorded simultaneously in 40 amblyopes [20 strabismics and 20 anisometropics] and 20 normal control subjects. Normal subjects were age and sex matched with patients. The P100 latency in PVEP was increased in both groups of patients but the P100 amplitude was reduced only in anisometropic group. In PERG, the amplitude of P50 was reduced in all patients with no significant change in latency. Beside reduced PVEP responses in strabismic and anisometropic amblyopia, the activity of retina reduced too. It is likely that retinal impulses can affect the development of visual system

[ investigation of relationship between binocular vision status and migraine headaches]

According to controversial results between migraine headaches and binocular vision anomalies, this study was designed to investigate the relationship between some parameters of binocular vision refractive errors and migraine headache. In this case-control study, 30 patients with neurologically diagnosed migraine who had inclusion criteria were selected as case group and 30 persons with no migraine headache were selected as control group. First, patients were screened by standard headache questionnaire and diagnosis refined by neurologist. The Refractive errors were determined by retinoscopy and were corrected. Then near point of convergence, jump convergence, stereopsis, fusional reserves and far and near deviation were determined. Data were analyzed by SPSS.15 software, using Man-Withney U test and multiple logistic regressions. The mean of near phoria, stereopsis, far positive fusional reserve, far negative fusional reserve, near positive fusional reserve, near negative fusional reserve in case and control groups were 6.5 +/- 2.85, 8.3 +/- 6.72 pd, 49.0 +/- 26.11, 154.17 +/- 333.82 sec/arc, 10.7 +/- 2.76, 6.07 +/- 5.07, 18.2 +/- 4.7, 11.0 +/- 7.37, 16.5 +/- 4.49, 13.97 +/- 8.72, 22.7 +/- 5.22 and 14.67 +/- 9.25 pd, respectively. The means of above parameters and jump convergence was significantly different between two groups [P<0.05]. However; no significant difference was observed between two groups for other variables [P>0.05]. In multiple logistic regression only jump convergence, far positive fusional reserve and near positive fusional reserve stayed in model [P<0.05]. This study showed higher rates of binocular vision anomalies [abnormal jump convergence, higher amounts of near deviation, abnormal positive and negative fusional convergence and reduced stereopsis] in migraine group than control. Hence, people who experience migraine headaches should be referred to their optometrist regularly to evaluate their binocular vision statuses

[ prevalence of visual problems in school children, Shiraz, Iran]

Refractive errors [myopia, hyperopia and astigmatism] could lead to an impaired quality of life affect a large proportion of the population worldwide, irrespective of age, sex and ethnic group. Such refractive errors can be easily diagnosed, measured and corrected with spectacles or other refractive corrections to attain normal vision. Since there is paucity of information in school children in Iran we aimed to investigate the distribution pattern of refractive status and prevalence of refractive errors in school-age children in Shiraz. A random sampling strategy in geographically defined clusters was used to identify children aged 6-15 years in Shiraz between 2008-2209. We carried out a school survey and actual eye examinations, including visual acuity measurements, stereopsis examination, anterior segment and eyeball movements, fundus examinations, and cycloplegic retinoscopy with 1% cyclopentolate. Of 3065 selected individuals, 2683 were participated in the study [response rate 86.6%]. According to cycloplegic refraction, 4.85% [95% [CI], 3.52 to 6.16] of the primary and middle school students were myopic and 4.64% [95% CI, 3.52 to 6.19] were hyperopic. For high school students, these rates were 22.19 and 11.4% respectively. Myopia and hyperopia were shown to be correlated with age. Prevalence of anisometropia, amblyopia and strabismus were 2.51%, 2.31[95%CI 1.51-3.11] and 1.83% [95%CI 1.15-2.50]. Compared to other published reports, the rate of myopia in the school children of Shiraz seems relatively high

[Effect of occlusion therapy on visual acuity, contrast sensitivity and stereopsis in amblyopia]

To determine the effect of occluding a normal eye on visual acuity, contrast sensitivity and stereopsis in amblyopic school children. Amblyopic children from primary schools of region 2 in Mashhad were identified and referred to Optometry Clinics of Mashhad Medical University through a screening program. Informed consent was obtained from the parents. All subjects underwent an ophthalmologic examination including visual acuity, subjective refractive error, biomicroscopy and funduscopy. Best-corrected visual acuity [BCVA], contrast sensitivity and stereopsis were measured by Snellen E chart, Cambridge low contrast chart and Titmus stereotest, respectively. All tests were repeated 2 weeks, 1 month and 3 months after initial examination. Of 1,947 children, 289 [14.8%] were amblyopic of whom 62 subjects were eventually enrolled for the study. BCVA in the amblyopic eye was less than 3/10 in 25.8% of subjects before treatment however all children had BCVA of 3/10 or better afterwards. Mean BCVA in amblyopic eyes significantly increased from 0.53 +/- 0.26 logMAR to 0.24 +/- 0.23 logMAR after 2 months of treatment [P<0.001]. Mean contrast sensitivity in amblyopic eyes was 68.3 before treatment which improved to 152.5, 138.2 and 198 after 2 weeks, 1 month and 2 months of treatment, respectively [P<0.001]. Contrast sensitivity may provide better assessment of visual function as compared to visual acuity. Changes in contrast sensitivity are more sensitive to occlusion therapy as compared to visual acuity. Therefore, contrast sensitivity may yield better evaluation of subclinical changes not detectable by testing visual acuity

[Prevalence of amblyopia in school children in Mashhad]

To determine the prevalence of amblyopia and its determinants in students of region 1 in Mashhad, 2006. Using randomized cluster sampling, 2510 students were selected to undergo ophthalmologic examinations. Amblyopia was defined as corrected visual acuity of 8/10 or less in either eye. Of the 2510 selected student, 2150 were examined [85.6% participation rate]. The prevalence of amblyopia was 1.9% [95% confidence interval [CI], 0.94 to 2.9] including 2.1% in female and 1.7% in male subjects [P=0.620]. Amblyopia was detected in right eye in 31.7%, left eye in 41.5% and both eyes in 26.8%. About 66% of amblyopic cases had refractive errors. The prevalence of amblyopia in students of region 1 in Mashhad is comparable to that of other parts of the country. Refractive error is a significant risk factor for occurring amblyopia

[Visual acuity and contrast sensitivity in pseudophakic patients after cataract surgery]

This study was designed to determine the role of intraocular lens implantation in visual acuity and contrast sensitivity in pseudophakic patients. This case control study was done in the year 2004 in Mashhad Ophthalmology Center of Khatam- al- Anbia. with convenience sampling method based on object visual acuity and contrast sensitivity in 85 pseudophakic patients [110 eyes] with a mean age of 63.83, and 20 age - matched phakic subjects [40 eyes] were compared. The visual acuity and contrast sensitivity at distance after correction of refractive disorders were measured by Snellen chart and Cambridge Low Contrast grating chart at 6 meter. Individual data, surgery date, visual acuity, and contrast sensitivity were gathered in a questionnaire and analyzed by descriptive statistics and frequency distribution tables. Statistical test showed that the best corrected visual acuity in IOL group had no significant difference from that in the phakic group [p=0.36]. But the contrast sensitivity reduces in the pseudophakic group comparing with the phakic group [p=0.004]. These patients often complain of blur vision, despite of good visual acuity. Contrast sensitivity reduced significantly with increase of age in both groups of normal and pseudophakic patients. No improvement in contrast sensitivity and visual acuity was found over the time [P[va]=0.174, P[cs]=0.257]. This study showed that intraocular lenses could provide good visual acuity for distance but there was slight reduction in contrast sensitivity. Contrast sensitivity test is an important tool for evaluation of visual function; especially age related changes or intraocular differences, which may not have been detected by visual acuity tests