73 resultados para mesopic vision


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Purpose: To study safety of children’s glasses in rural China, where fear that glasses harm vision is an important barrier for families and policy-makers. Design: Exploratory analysis from a cluster-randomized, investigator-masked, controlled trial.Methods: Among primary schools (n=252) in western China, children were randomized by school to one of three interventions: free glasses provided in class, vouchers for free glasses at a local facility or glasses prescriptions only (Control group). The main outcome of this analysis is uncorrected visual acuity after 8 months, adjusted for baseline acuity.Results: Among 19,934 children randomly selected for screening, 5852 myopic (spherical equivalent refractive error <= -0.5 D) eyes of 3001 children (14.7%, mean age 10.5 years) had VA <= 6/12 without glasses correctable to > 6/12 with glasses, and were eligible. Among these, 1903 (32.5%), 1798 (30.7%), and 2151 (36.8%) were randomized to Control, Voucher and Free Glasses respectively. Intention-to-treat analyses were performed on all 1831 (96.2%), 1699 (94.5%), and 2007 (93.3%) eyes of children with follow-up in Control, Voucher and Free Glasses groups. Final visual acuity for eyes of children in the treatment groups (Free Glasses and Voucher) was significantly better than for Control children, adjusting only for baseline visual acuity (difference of 0.023 logMAR units [0.23 vision chart lines, 95% CI: 0.03, 0.43]) or for other baseline factors as well (0.025 logMAR units [0.25 lines, 95% CI 0.04, 0.45]). Conclusion: We found no evidence that spectacles promote decline in uncorrected vision with aging among children.

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Purpose
To evaluate the impact of the position of an asymmetric multifocal near segment on visual quality.

Setting
Cathedral Eye Clinic, Belfast, United Kingdom.

Design
Retrospective comparative case series.

Methods
Data from consecutive patients who had bilateral implantation of the Lentis Mplus LS-312 multifocal intraocular lens were divided into 2 groups. One group received inferonasal near-segment placement and the other, superotemporal near-segment placement. A +3.00 diopter (D) reading addition (add) was used in all eyes. The main outcome measures included uncorrected distance visual acuity (UDVA), uncorrected near visual acuity (UNVA), contrast sensitivity, and quality of vision. Follow-up was 3 months.

Results
Patients ranged in age from 43 to 76 years. The inferonasal group comprised 80 eyes (40 patients) and the superotemporal group, 76 eyes (38 patients). The mean 3-month spherical equivalent was −0.11 D ± 0.49 (SD) in the inferonasal group and −0.18 ± 0.46 D in the superotemporal group. The mean postoperative UDVA was 0.14 ± 0.10 logMAR and 0.18 ± 0.15 logMAR, respectively. The mean monocular UNVA was 0.21 ± 0.14 logRAD and 0.24 ± 0.13 logRAD, respectively. No significant differences were observed in the higher-order aberrations, total Strehl ratio (point-spread function), or modulation transfer function between the groups. Dysphotopic symptoms measured with a validated quality-of-vision questionnaire were not significantly different between groups.

Conclusion
Positioning of the near add did not significantly affect objective or subjective visual function parameters.

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The work of children’s liberationists have been long been critiqued for pushing the parameters of rights discourse too far; specifically, by suggesting that there are no significant differences between children and adults, including their ability for self-determination. John Holt’s 1974 text Escape from Childhood is one such work which was deemed highly controversial for its time. This article uses Holt’s Escape from Childhood as an overarching framework against which to examine the current state of play on children’s rights as explicated through the UN Convention on the Rights of the Child. It suggests that whilst Holt has often been critiqued for being too radical, in the context of current children’s rights discourse Holt’s visioning is not as radical as it might first appear.

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This paper examines the prevalence of vision problems and the accessibility to and quality of vision care in rural China. We obtained data from 4 sources: 1) the National Rural Vision Care Survey; 2) the Private Optometrists Survey; 3) the County Hospital Eye Care Survey; and 4) the Rural School Vision Care Survey. The data from each of the surveys were collected by the authors during 2012. Thirty-three percent of the rural population surveyed self-reported vision problems. Twenty-two percent of subjects surveyed had ever had a vision exam. Among those who self-reported having vision problems, 34% did not wear eyeglasses. Fifty-four percent of those with vision problems who had eyeglasses did not have a vision exam prior to receiving glasses. However, having a vision exam did not always guarantee access to quality vision care. Four channels of vision care service were assessed. The school vision examination program did not increase the usage rate of eyeglasses. Each county-hospital was staffed with three eye-doctors having one year of education beyond high school, serving more than 400,000 residents. Private optometrists often had low levels of education and professional certification. In conclusion, our findings shows that the vision care system in rural China is inadequate and ineffective in meeting the needs of the rural population sampled.

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Using a survey of 19,977 children in two provinces, this paper explores the prevalence, correlates and potential consequences of poor vision among children in China's vast but understudied rural areas. We find that 24% of sample students suffer from reduced uncorrected visual acuity in either eye and 16% in both eyes. Poor vision is significantly correlated with individual, parental and family characteristics, with modest magnitudes for all correlates but home province and grade level. The results also suggest a possible adverse impact of poor vision on academic performance and mental health, particularly among students with severe poor vision.

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Purpose: To estimate the prevalence, potential determinants, and proportion of met need for near vision impairment (NVI) correctable with refraction approximately 2 years after initial examination of a multi-country cohort. Design: Population-based, prospective cohort study. Participants: People aged ≥35 years examined at baseline in semi-rural (Shunyi) and urban (Guangzhou) sites in China; rural sites in Nepal (Kaski), India (Madurai), and Niger (Dosso); a semi-urban site (Durban) in South Africa; and an urban site (Los Angeles) in the United States. Methods: Near visual acuity (NVA) with and without current near correction was measured at 40 cm using a logarithm of the minimum angle of resolution near vision tumbling E chart. Participants with uncorrected binocular NVA ≤20/40 were tested with plus sphere lenses to obtain best-corrected binocular NVA. Main Outcome Measures: Prevalence of total NVI (defined as uncorrected NVA ≤20/40) and NVI correctable and uncorrectable to >20/40, and current spectacle wearing among those with bilateral NVA ≤20/63 improving to >20/40 with near correction (met need). Results: Among 13 671 baseline participants, 10 533 (77.2%) attended the follow-up examination. The prevalence of correctable NVI increased with age from 35 to 50-60 years and then decreased at all sites. Multiple logistic regression modeling suggested that correctable NVI was not associated with gender at any site, whereas more educated persons aged >54 years were associated with a higher prevalence of correctable NVI in Nepal and India. Although near vision spectacles were provided free at baseline, wear among those who could benefit was <40% at all but 2 centers (Guangzhou and Los Angeles). Conclusions: Prevalence of correctable NVI is greatest among persons of working age, and rates of correction are low in many settings, suggesting that strategies targeting the workplace may be needed.

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Purpose: The recently completed Chinese "Million Cataract Surgeries Program" (MCSP) is among the largest such campaigns ever, providing 1.05 million operations. We report MCSP outcomes for the first time, in Jiangxi, the province with the greatest program output. Methods: Ten county hospitals participating in MCSP were selected in Jiangxi (range of gross domestic product per capita US$743-2998). Each hospital sought to enroll 75 consecutive MCSP patients aged ≥50 years. Data recorded included type of cataract procedure, bilateral uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), and refractive error pre- and ≥50 days postoperatively. Results: Among 715 patients (mean age 72.3±9.1 years, 55.5% female), preoperative UCVA was <3/60 (legally blind) bilaterally in 13.3% and unilaterally in the operated eye in 50.9%. No subjects had UCVA >6/18 preoperatively. Small incision cataract surgery was performed in 92.3% patients. Among 662 patients (92.6%) completing follow-up was ≥ 40 days after surgery, BCVA was ≥6/18 in 80.1%, UCVA was ≥6/18 in 57.1% and UCVA was <3/60 in 2.1%. Older age (p<0.001), female sex (p=0.04), worse refractive error (p=0.02) and presence of intra- (p=0.002) and postoperative surgical complications (p<0.001), were independently associated with worse postoperative UCVA. Based on these results, the MCSP cured an estimated 124,950 cases (13.3%×[100-2.1%]×1.05 million) of bilateral and 502,500 (50.9%×[100-2.1%]×1.05 million) of unilateral blindness. Conclusions: Due to relatively good outcomes and the large number of surgeries performed on blind persons, the sight-restoring impact of the MCSP was probably substantial. © Informa Healthcare USA, Inc.

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AIM: To study the effect of posterior capsular opacification (PCO) on vision and visual function in patients undergoing cataract surgery in rural China, and to compare this with the effect of refractive error. METHODS: Patients undergoing cataract surgery in at least one eye by local surgeons in a rural setting between 8 August and 31 December 2005 were examined with slit lamp grading of PCO 10-14 months after surgery. Subjects with any PCO associated with best-corrected visual acuity of 6/7.5 or worse, or with grade 2+ or worse PCO without visual decrement, were offered YAG laser capsulotomy. Vision and self-reported visual function were assessed, and various demographic and clinical factors potentially associated with PCO were recorded. RESULTS: Of 313 patients operated on within the study window, 239 (76%) could be contacted by telephone; study examinations were performed on 176 (74%). Examined subjects had a mean (SD) age of 69.4 (10.5) years, 116 (67%) were female, and 149 (86%) had been blind (presenting visual acuity < or = 6/60) in the operated eye before surgery. PCO of grade 1 or above was present in 34 of 204 operated eyes (16.7%). Those with PCO had significantly worse presenting vision (p = 0.007) but not visual function (p>0.3) than those without PCO. Women had a significantly higher prevalence of PCO (20.9%) than did men (8.6%, p<0.05). Of 19 eyes undergoing capsulotomy with best-corrected visual acuity measured the next day, 13 (68%) improved by one or more lines, and seven (37%) improved by two or more lines. Despite a higher uptake of capsulotomy (95%) as opposed to refraction (35%) in this cohort, the yield in terms of eyes with poor presenting visual acuity (< 6/18) that could be improved was higher for refraction (26% = 9/35) than for capsulotomy (9% = 3/35). CONCLUSION: The prevalence of PCO and impact on vision and visual function in this cohort was modest 1 year after surgery. However, PCO prevalence increases with time. Follow-up of this cohort is underway to determine the effectiveness of this early intervention in identifying and treating subjects who will eventually experience clinically significant PCO.

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OBJECTIVE: To assess and improve the accuracy of lay screeners compared with vision professionals in detecting visual impairment in secondary schoolchildren in rural China. METHODS: After brief training, 32 teachers and a team of vision professionals independently measured vision in 1892 children in Xichang. The children also underwent vision measurement by health technicians in a concurrent government screening program. RESULTS: Of 32 teachers, 28 (87.5%) believed that teacher screening was worthwhile. Sensitivity (93.5%) and specificity (91.2%) of teachers detecting uncorrected presenting visual acuity of 20/40 or less were better than for presenting visual acuity (sensitivity, 85.2%; specificity, 84.8%). Failure of teachers to identify children owning but not wearing glasses and teacher bias toward better vision in children wearing glasses explain the worse results for initial vision. Wearing glasses was the student factor most strongly predictive of inaccurate teacher screening (P < .001). The sensitivity and specificity of the government screening program detecting low presenting visual acuity were 86.7% and 28.7%, respectively. CONCLUSIONS: Teacher vision screening after brief training can achieve accurate results in this setting, and there is support among teachers for screening. Screening of uncorrected rather than presenting visual acuity is recommended in settings with a high prevalence of corrected and uncorrected refractive error. Low specificity in the government program renders it ineffective.

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PURPOSE: Presbyopia limits activities of daily living, but population-based data from rural China are scarce. METHODS: A population-based, cross-sectional study was conducted in 2009 among all persons aged 40+ years in a rural area near Shenyang, China. Distance and near VA were measured using logMAR E charts. Individuals with pinhole-corrected distance vision ≥20/63 underwent detailed eye examination and near refraction. RESULTS: A total of 1008 (91.5%) respondents were examined (mean age, 58.4 ± 10.7 years for men, 56.8 ± 9.89 years for women). Women and older subjects were more likely to participate. The prevalence of functional presbyopia (near vision <20/50 [N8] improved by ≥1 line with correction) was 67.3% (95% confidence interval [CI], 64.30%-70.09%), increasing from 27.6% at 40 to 49 years of age to 81.8% at 60 to 69 years. Multivariate analysis showed that older age (P < 0.001), but not gender or education, was significantly associated with a higher risk of presbyopia. Self-reported presbyopic spectacle correction coverage was 51.5%. In multivariate logistic regression models, worse presenting near vision (P = 0.013) and higher required spherical equivalent power (P < 0.001) were associated with having correction, while age, gender, education, and distance vision were unassociated. Major barriers reported by persons without near correction included poor quality of available glasses (33.1%) and lack of awareness of the condition and its treatment (28.8%). CONCLUSIONS: Presbyopia is highly prevalent in rural China, and nearly half of affected persons have no access to correction. Interventions should focus on education and improvement in the quality of refractive services.

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PURPOSE: To evaluate the impact of near-vision impairment on visual functioning and quality of life in a rural adult population in Shenyang, northern China. METHODS: A population-based, cross-sectional study was conducted among persons aged 40+ years, during which functional presbyopia (correctable presenting near vision < 20/50 [N8] at 40 cm) was assessed. Near-vision-related quality of life and spectacle usage questionnaires were administered by trained interviewers to determine the degree of self-rated difficulty with near tasks. RESULTS: A total of 1008 respondents (91.5% of 1102 eligible persons) were examined, and 776 (78%) of completed the questionnaires (mean age, 57.0 ± 10.2 years; 63.3% women). Near-vision spectacle wearers obtained their spectacles primarily from markets (74.5%) and optical shops (21.7%), and only 1.14% from eye clinics. Among 538 (69.3%) persons with functional presbyopia, self-rated overall (distance and near) vision was worse (P < 0.001) and difficulty with activities of daily living greater (P < 0.001) than among nonpresbyopes. Odds of reporting any difficulty with daily tasks remained higher (OR = 2.32; P < 0.001) for presbyopes after adjustment for age, sex, education and distance vision. Compared to persons without presbyopia, presbyopic persons were more likely to report diminished accomplishment due to vision (P = 0.01, adjusted for age, sex, education, and distance vision.) CONCLUSIONS: Difficulties with activities of daily living and resulting social impediments are common due to presbyopia in this setting. Most spectacle wearers with presbyopia in rural China obtain near correction from sources that do not provide comprehensive vision care.