Sympathetic inhibition of accommodation after sustained nearwork in subjects with myopia and emmetropia

PURPOSE. The purposes of the present study were to assess the effect of a sympathetic inhibitory pharmacologic agent, timolol maleate, on the magnitude of nearwork-induced transient myopia (NITM) and its decay in different refractive groups for an extended near task duration and to determine the proportion of the young adult population manifesting effective sympathetic access under naturalistic closed-loop viewing conditions. METHODS. Ten subjects with emmetropia and 10 with myopia were tested. They read binocularly for 1 hour at a distance of 35 to 40 cm. NITM was calculated as the difference in distance refractive state after task as compared with before task immediately after reading. All subjects received timolol maleate to block the sympathetic nervous system and betaxolol as a control agent in independent test sessions separated by at least 3 days. Forty minutes after drug instillation, the NITM measurement procedure was repeated. RESULTS. Initial NITM magnitude was larger in subjects with myopia than in subjects with emmetropia before and after timolol instillation. Furthermore, NITM magnitude in subjects with sympathetic access was increased after timolol instillation. In contrast, with the control agent betaxolol, there was no increase. NITM decay duration to baseline was increased after timolol instillation in the subjects with myopia only. Only 15% of the subjects (n = 3 subjects with myopia) demonstrated effective and significant access to sympathetic facility. CONCLUSIONS. Subjects with myopia demonstrated an increase in decay duration with timolol, thus suggesting impaired sympathetic inhibition of accommodation. This may be a precursor for myopia progression in some persons

Reading eye movements performance on iPad vs print using a visagraph

This study investigated reading comprehension, reading speed, and the quality of eye movements while reading on an iPad, as compared to printed text. 31 visually-normal subjects were enrolled. Two of the passages were read from the Visagraph standardized text on iPad and Print. Eye movement characteristics and comprehension were evaluated. Mean (SD) fixation duration was significantly longer with the iPad at 270 ms (40) compared to the printed text (p=0.04) at 260 ms (40). Subjects’ mean reading rates were significantly lower on the iPad at 294 words per minute (wpm) than the printed text at 318 wpm (p=0.03). The mean (SD) overall reading duration was significantly (p=0.02) slower on the iPad that took 31 s (9.3) than the printed text at 28 s (8.0). Overall reading performance is lower with an iPad than printed text in normal individuals. These findings might be more consequential in children and adult slower readers when they read using iPads.

Near work, outdoor activity, and myopia in children in rural China: The Handan Offspring Myopia Study

Dataset. (XLS 112 kb

Elementary school comprehensive intervention and myopia development: the Wenzhou Epidemiology of Refraction Error Study

AIM: To investigate the effects of school-based comprehensive intervention on myopia development in elementary school children. METHODS: As a part of the Wenzhou Epidemiology of Refraction Error Study, there were 1524 participating elementary students (730 girls, 47.9%) in grades 1 to 3 from three campuses of one school, aged 7.3±0.9y, who were examined twice every year for a 2.5y follow up period. Comprehensive intervention and other reminders were given at school every semester for the intervention group. The control group did not receive comprehensive intervention and did not have reminders of it. RESULTS: There were 651 students in the intervention group [mean age 7.3±0.9y; 294 (45.2%) girls] and 737 students in the control group [mean age 7.2±0.9y; 346 (46.9%) girls]. Overall mean myopia progression during the 2.5y follow-up was -0.49±1.04 diopters (D) in the intervention group and -0.65±1.08 D in the control group (P=0.004). The majority that not get myopia at baseline spherical equivalent (SE≤-1.0 D). Their mean myopia progression during the 2.5y follow-up was -0.37±0.89 D in the intervention group and -0.51±0.93 D in the control group (27.5% reduction, P=0.009); Overall, mean axial length elongation was less in the intervention group (0.56±0.32 mm) than in the control group (0.61±0.38 mm, 10.5% reduction, P=0.009). The percentage of close reading distance (<30 cm) in the intervention group was less than in the control group (73.4% vs 76.2%, P<0.001), the percentage of everyday perform eye exercises in the intervention group was more than in the control group (27.8% vs 20.7%, P<0.001) 30mo later. CONCLUSION: The comprehensive intervention program at elementary school has a significant alleviating effect on myopia progression for children during the 2.5y follow-up, especially for those non-myopia at baseline

Conceptual model of human blur perception

AbstractAn empirically based, conceptual model of human blur perception is presented. It incorporates the concepts of blur detection and blur discrimination in depth, and across the central and peripheral retina, in two- and three-dimensional visual space. Key aspects of the model are its dynamic nature, predictability regarding the blur-based depth-ordering of objects, patterns of retinal defocus with far and near viewing, and interactions related to retinal defocus between the central and peripheral retina. Furthermore, a two-dimensional schematic representation of the blur-free region during near viewing is depicted in dioptric space. This model has implications with respect to accommodative control, depth perception, and refractive error development and progression

Effect of defocus on response time in different age groups: A pilot study

Purpose: To assess the response time associated with visual performance (VP) tasks in the presence of defocus in different presbyopic populations. Methods: 58 eyes between the ages of 35 and 50 years were studied. Subjects were categorized as pre-presbyopic (35–39 years), early-presbyopic (40–45 years), and mid-presbyopic (46–50 years). VP measurements obtained monocularly included distance and near high contrast (HC) and low contrast (LC) optotype recognition, and contrast threshold at 12 cpd for different defocus magnitudes between 0D and 3D in 1D steps. Response time defined as the time taken to recognize and verbalize an optotype, was compared among different presbyopic age groups. Results: From 58 eyes, mean (SD) response time for high contrast distance visual acuity for 0D through 3D ranged between 1.48 (0.23) and 1.87 (0.31) s, whereas low contrast distance visual acuity ranged between 1.5 (0.22) and 2.09 (0.49) s. Mean response time for high contrast near visual acuity for 0D through 3D ranged between 1.56 (0.19) and 2.23 (0.45) s. However, for low contrast near visual acuity it ranged between 1.75 (0.32) and 2.71 (0.94) s. Mean (SD) response time for 12 cpd ranged between 2.11 (0.50) and 5.72 (1.09) s. ANOVA revealed a significant difference in response time for distance, near visual acuity and contrast sensitivity as a function of defocus for different age groups. Conclusions: Response time is increased in the presence of increasing defocus for both distance and near visual acuity and could impact on performance for critical tasks. Full correction of visual acuity at distance and near in presbyopes is warranted always

Under-correction of human myopia – Is it myopigenic?: A retrospective analysis of clinical refraction data

Purpose: To investigate retrospectively, based on routine clinical records in an optometric office, the effect of refractive under-correction of the myopic spectacle prescription on myopic progression in children and young adults. Methods: Patient records of children and young-adult myopes in a private optometric practice in Glendale, Arizona, USA, were initially reviewed to identify those that met the criteria. Information collected from the patient records included: age, gender, the dates and number of their visits (more than one visit was required for use of the data), final prescription, and non-cycloplegic subjective refraction. For each patient visit, the difference in spherical equivalent (SE) between the subjective refraction for maximum visual acuity and the final prescription was calculated for both the left and right eyes. Myopia progression was defined as the difference in SE between the final subjective refraction of the previous visit and that of the subsequent visit. Based on the study criteria, a total of 275 patient visits were obtained from the data collected in 76 patients. Results: A significant positive correlation was found between the magnitude of under-correction of the refractive error and myopic progression (r = 0.301, p < 0.01); that is, the greater the under-correction, the greater the myopic progression. In addition, there was a significant positive correlation between myopia progression and subjective refraction (r = 0.166, p = 0.006); that is, the greater the degree of myopia, the greater the effect of under-correction. However, there was no significant correlation between myopia progression and either age (r = −0.11, p = 0.86) or gender (r = −0.82, p = 0.17). Conclusion: Under-correction of myopia produced a small but progressively greater degree of myopic progression than did full correction. The present finding is consistent with earlier clinical trials and modeling of human myopia