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Cheng H.-M.,University of Medical Sciences and Technology | Cheng H.-M.,Chung Shun Medical University Hospital | Sun H.-Y.,University of Medical Sciences and Technology | Lin D.P.-C.,University of Medical Sciences and Technology | And 12 more authors.
Clinical and Experimental Optometry | Year: 2012

Purpose: The aim was to screen children from Grades 1 to 6 in an urban elementary school in Central Taiwan for visual deficits and associated parameters and, as an extension, to examine the acceptance of cycloplegic therapy as well as the lag in optimal vision correction. Methods: Of 900 students in one school, 731 participated in the study, with parental consent. Data from 694 students, who had also completed a vision correction history were analysed. In addition to body height and weight, the screening included vision, non-cycloplegic autorefraction and distance retinoscopy, axial length and functional testing. Results: There was a decrease in students with vision of 1.0 or better from 55.8 per cent in Grade 1 to 20.0 per cent in Grade 6. The decreases between Grades 2 and 3 and Grades 5 and 6 were significant. These trends were in general agreement with those based on refractive error and axial length. The students had abnormal functional findings including: stereoscopic vision, 9.2 per cent; cover tests, 14.1 per cent; pupillary responses, 13.8 per cent; and less commonly in extraocular muscular functions (3.0 per cent) and colour vision (5.2 per cent). A full 40 per cent of students received cycloplegic therapy with 25 per cent dropping out for various reasons. These cases were generally associated with lower vision and higher myopia. A lag between subnormal vision and optical correction was also observed with 55.1 per cent apparently not optimally corrected. Other parameters, including body height, weight and body mass index were not correlated with vision or refractive error. Conclusions: Age-dependent increase in the prevalence of myopia appears to continue despite the common practice of topical cycloplegic therapy in Taiwan. Timely correction of the refractive error is also lacking. While maintaining a visual acuity of 1.0 or better for all students at all times is not possible, this lag might be shortened by more frequent screening and/or direct provision of optical aids. © 2012 Optometrists Association Australia.


Sun H.-Y.,Chung Shan Medical University | Sun H.-Y.,University of Medical Sciences and Technology | Sun H.-Y.,Chung Shun Medical University Hospital | Wang H.-C.,National Chung Cheng University | Yang S.-F.,Chung Shan Medical University
Optics Communications | Year: 2013

With the rapid development of vision correction techniques, increasing numbers of people have undergone laser vision corrective surgery in recent years. The use of a laser scalpel instead of a traditional surgical knife reduces the size of the wound and quickens recovery after surgery. The primary objective of this article is to examine corneal surgery for vision correction via multi-layer swim-ring-shaped wave circles of the technique through optical simulations with the use of Monte-Carlo ray tracing method. Presbyopia stems from the loss of flexibility of crystalline lens due to aging of the eyeball. Diopter adjustment of a normal crystalline lens could reach 5 D; in the case of presbyopia, the adjustment was approximately 1 D, which made patients unable to see objects clearly in near distance. Corneal laser surgery with multi-layer swim-ring-shaped wave circles was performed, which ablated multiple circles on the cornea to improve flexibility of the crystalline lens. Simulation results showed that the ability of the crystalline lens to adjust increased tremendously from 1 D to 4 D. The method was also used to compare the images displayed on the retina before and after the treatment. The results clearly indicated a significant improvement in presbyopia symptoms with the use of this technique. © 2013 Elsevier B.V. All rights reserved.


Cheng H.-M.,Chung Shun Medical University | Cheng H.-M.,Chung Shun Medical University Hospital | Chang H.-H.,Chung Shun Medical University | Sun H.-Y.,Chung Shun Medical University | And 5 more authors.
Life Science Journal | Year: 2012

To examine the correlation between visual acuity and refractive error of elementary school students with (1) parental vision status; (2) dietary history; (3) visual habits; and (4)in- and out-door activities. 694 (of 731) students from one urban elementary school participated in the study.They underwent visual acuity test and distance retinoscopy together with completion of a multi-item questionnaire with the help of their parents and teachers. There was a decrease in the number of students with 1.0 or better vision from over 50% in Grade 1 to around 20% in Grade 6. At the same time, those with 0.2 or worse vision increased from Grades 1 to 6. No difference was noted between males and females in refractive error. And in parallel to the change in visual acuity, there was a decrease in students with -1D or less and an increase in students with -1D or more of refractive error from Grades 1 to 6. These visual parameters were also associated with mother's(but not father's) refractive error, ingestion of table grapes, near work, and indoor exercises, but not with outdoor activities on weekdays, weekends, or during vacation time. In the absence of efficacious myopia control at present, progression of school myopia maybe minimized through practice of visual hygiene and reduction of indoor hours.


Cheng C.-Y.,Chung Shun Medical University | Cheng C.-Y.,Chung Shun Medical University Hospital | Huang W.,Yuanpei University | Sun H.-Y.,Chung Shun Medical University | And 9 more authors.
Life Science Journal | Year: 2012

The occurrence of the lag in optimal optical correction was investigated in three geographically different urban elementary schools in Taiwan. The results showed that among the schools in Tamsui (N=606), Taichung (N=702), and Tainan (N=586), Tainan had the highest proportion of students with correction (47.9% of all students), followed by Taichung (26.2%), and Tamsui (20.8%). Tamsui appeared to have the most lag in optimal correction: 55.3% needed further correction, yet only 20.8% had been corrected, or a lag of 34.5%. In contrast, the lag in Tainan and Taichung was 16.3% and 28.9%, respectively. Based on linear regression analysis, the lag or unmet needs could result in the worsening of myopia. To reduce the lag, follow up with the parents after student vision screening was supplemented with public health education or direct provision of any optical devices to the students.


Sun H.-Y.,Chung Shan Medical University | Sun H.-Y.,Chung Shun Medical University | Sun H.-Y.,Chung Shun Medical University Hospital | Yang H.-W.,Central Taiwan University of Science and Technology | And 4 more authors.
Life Science Journal | Year: 2013

To compare the values of the data on the central and peripheral curvature of the cornea in order to determine the differences between the overall corneal curvature after custom laser in situ keratomileusis (LASIK) and orthokeratology procedures in correcting refractive error. We evaluated 12 patients undergoing orthokeratology for the correction of myopia spherical equivalent (OD, mean±SD = -3.67 ± 2.16D; OS, mean±SD = -4.02 ± 2.21D), 10 patients undergoing custom LASIK surgery (OD, mean±SD = -4.25 ± 2.43D; OS, mean±SD = -4.41 ± 3.01D). The values of the front corneal surfaces were derived using Medmont E300 corneal topographer Version 4.9.0.0 (Medmont, Camberwell, Victoria, Australia) prior to and at least 3 months after each treatment with samples taken from the center of the cornea and 4 points to each side of the horizontal meridian at intervals of 1 mm. Among the two clinical groups, no statistically significant differences on OD and OS were found for the spherical equivalent (p = 0.756 and p = 0.423). The refractive power of elevation became positive in the central nasal (4 mm) and temporal regions (4 mm). The changes in OD were statistically significant (p<0.001) in nasal 2 mm after orthokeratology compared to the value for the case of LASIK. The OS date of post- minus pre-orthokeratology compared with that of LASIK exhibited significant differences on the nasal region (2-3 mm) and temporal region (2-3 mm) (p<0.001). The differences in the changes in the front corneal curvature between LASIK and orthokeratology reveal a much different mechanism for alternating corneal power. The changes in the corneal surface refractive power are 2 to 3 times greater in LASIK procedures than in orthokeratology for both central and peripheral regions.


Ou C.-J.,Hsiuping University of Science and Technology | Sun H.-Y.,Chung Shun Medical University Hospital
International Journal for Numerical Methods in Biomedical Engineering | Year: 2012

The finite element method with linear elastic assumption for predicting the intraocular pressure (IOP) readings after reshaping of the corneal structure is demonstrated in the present study. Twelve effective eye measurements in seven subjects were examined using the TOPCON LX-10, a noncontact intraocular pressure measurement technique, before and after laser-assisted in situ Keratomileusis surgery. A linear elastic model was introduced to reduce possible errors from a complicated anisotropic model with uncertain tissue parameters. Linear relationship between the simplified removal depth of laser-assisted in situ Keratomileusis and predicted IOP was expected, and the comparisons between measurements and the predicted model were made. The results indicated that the expected IOP readings are close to the measurement IOP values, while larger errors occur at smaller IOP conditions. In conclusion, the linear elastic finite element approach can already reveal parameters that influence measurement data the most, and the interaction between parameters was higher than we had expected. This helps us to build the confidence on implementing the anisotropic model. © 2012 John Wiley & Sons, Ltd.

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