Biomechanics Explains Variability of Response of Small Hypertropia to Graded Vertical Rectus Tenotomy.

PURPOSE: Small angle hypertropia in sagging eye syndrome is conveniently treated by graded vertical rectus tenotomy, yet an adjustable technique under topical anesthesia has been recommended because of variability of effect. We performed graded tenotomy in an experimental model to elucidate the reason for variability of response to this surgical procedure. DESIGN: Experimental study. METHODS: Thirty-two fresh bovine rectus musculotendon specimens were prepared including continuity with insertional sclera, and extending for a total 40 mm length to the proximal muscle bellies, and trimmed to 16 mm width. Specimens were anchored by the clamps at the scleral insertion and muscle belly ends within a physiological chamber. After preconditioning and elongation to 10% strain was imposed by a linear motor, tensile force was allowed to stabilize at a plateau state. Then 25%, 50%, 75%, 90%, and 100% marginal tenotomies were performed progressively as remnant forces were measured. RESULTS: Tendon thickness averaged 0.29 ± 0.05 mm and width 19.71 ± 2.25 mm. On average, remnant force decreased linearly (R2 = 0.985) from 4.23 ± 1.34, 2.76 ± 0.88, 1.70 ± 0.73, 1.01 ± 0.49, 0.39 ± 0.10, and 0 N, at 0%, 25%, 50%, 75%, 90%, and 100% tenotomy. However, there was marked individual variability in effect among specimens, with coefficients of variation of 32%, 32%, 43%, 49%, and 27%, respectively. CONCLUSION: On average, there is a linear relationship between graded rectus tenotomy and percentage force reduction, but the effect among individual tendons is large, paralleling the reported variation in surgical effect. This explains and implies continued advisability of adjustable technique in this procedure.

An improved strabismus screening method with combination of meta-learning and image processing under data scarcity.

PURPOSE: Considering the scarcity of normal and strabismic images, this study proposed a method that combines a meta-learning approach with image processing methods to improve the classification accuracy when meta-learning alone is used for screening strabismus. METHODS: The meta-learning approach was first pre-trained on a public dataset to obtain a well-generalized embedding network to extract distinctive features of images. On the other hand, the image processing methods were used to extract the position features of eye regions (e.g., iris position, corneal light reflex) as supplementary features to the distinctive features. Afterward, principal component analysis was applied to reduce the dimensionality of distinctive features for integration with low-dimensional supplementary features. The integrated features were then used to train a support vector machine classifier for performing strabismus screening. Sixty images (30 normal and 30 strabismus) were used to verify the effectiveness of the proposed method, and its classification performance was assessed by computing the accuracy, specificity, and sensitivity through 5,000 experiments. RESULTS: The proposed method achieved a classification accuracy of 0.805 with a sensitivity (correct classification of strabismus) of 0.768 and a specificity (correct classification of normal) of 0.842, whereas the classification accuracy of using meta-learning alone was 0.709 with a sensitivity of 0.740 and a specificity of 0.678. CONCLUSION: The proposed strabismus screening method achieved promising classification accuracy and gained significant accuracy improvement over using meta-learning alone under data scarcity.

An automatic screening method for strabismus detection based on image processing.

PURPOSE: This study aims to provide an automatic strabismus screening method for people who live in remote areas with poor medical accessibility. MATERIALS AND METHODS: The proposed method first utilizes a pretrained convolutional neural network-based face-detection model and a detector for 68 facial landmarks to extract the eye region for a frontal facial image. Second, Otsu's binarization and the HSV color model are applied to the image to eliminate the influence of eyelashes and canthi. Then, the method samples all of the pixel points on the limbus and applies the least square method to obtain the coordinate of the pupil center. Lastly, we calculated the distances from the pupil center to the medial and lateral canthus to measure the deviation of the positional similarity of two eyes for strabismus screening. RESULT: We used a total of 60 frontal facial images (30 strabismus images, 30 normal images) to validate the proposed method. The average value of the iris positional similarity of normal images was smaller than one of the strabismus images via the method (p-value<0.001). The sample mean and sample standard deviation of the positional similarity of the normal and strabismus images were 1.073 ± 0.014 and 0.039, as well as 1.924 ± 0.169 and 0.472, respectively. CONCLUSION: The experimental results of 60 images show that the proposed method is a promising automatic strabismus screening method for people living in remote areas with poor medical accessibility.

Increased myofiber size and reduced satellite cell numbers in medial rectus muscle of patients with intermittent exotropia.

PURPOSE: To elucidate the differences in muscle bundle and satellite cells in medial rectus muscle through histological and Immunofluorescence studies of intermittent exotropia patients and normal controls. Materials and Methods: From January 2015 to December 2017, 15 patients who underwent medial rectus resection surgery at Kosin University Gospel Hospital were enrolled. Four medial recti muscles collected from two brain-dead men without strabismus were used as controls and compared with the intermittent exotropia group. Hematoxylin and eosin (HE) staining were performed, and all muscle bundle diameters were measured with the Image J program and compared to the mean value. Immunological staining for MyoHC (Myosin Heavy Chain), PAX7 (Transcription Factor), and PCNA (Proliferating Cell Nuclear Antigen) were performed to analyze the distribution of myocytes and PAX7-positive and PCNA-positive cells. Results: The mean ages of the strabismus and control groups were 17.33 ± 13.05 and 22.0 ± 5.85 years, respectively, and the male to female ratio was 7:2 and 2:0. The average angle of deviation in the exotropia patients was 36.0 ± 16.83 prism diopters. The mean muscle bundle diameter under light microscopy was 60.21 ± 1.48 in the exotropia group and 52.27 ± 0.74 in the control group. The exotropia group showed significantly greater mean muscle bundle diameter (p < .001) and diameter regularity than the control group. The PAX7(+)/muscle bundle number ratio was 0.016 ± 0.014 and 0.056 ± 0.015 in the exotropia group and control group, respectively (p < .001), and the PCNA(+)/muscular bundle number ratio was 0.015 ± 0.017 and 0.182 ± 0.102 (p < .001). Both were significantly higher in the control group compared to that in the exotropia patients. Conclusion: In the exotropia group, mean diameter of medial rectus muscle bundle was significantly larger than that of control group. The ratios of PAX7 and PCNA to muscle bundle number were significantly higher in the control group than intermittent extropia group. We found the negative relationship between activation of satellite cells and muscle bundle diameter, and it might take one step forward to elucidate the pathogenesis of intermittent extropia.

Influence of Growth Temperature on the Characteristics of Single-Junction p­i­n InGaP Solar Cells.

Single-junction p­i­n InGaP solar cells are grown at various temperatures from 620 to 700 °C by low pressure metalorganic chemical vapor deposition on GaAs (001) substrates. The short circuit current density of the p­i­n InGaP solar cells increases by up to 38.8% when the growth temperature is reduced from 700 to 620 °C, while the open circuit voltage and fill factor show relatively small changes. The external quantum efficiency, especially, in the wavelength regime below 500 nm, is improved for the p­i­n InGaP solar cells grown at lower temperatures. The improvement might be attributed to the reduced absorption loss of the photons in the n-InGaP emitter region. The highest conversion efficiency of 11.01% is attributed from the p­i­n InGaP solar cell grown at 640 °C. Electron mobility and concentration of undoped InGaP layers are investigated as a function of the growth temperature and correlated with the p­i­n InGaP solar cell performance.

Ultra-high-throughput Production of III-V/Si Wafer for Electronic and Photonic Applications.

Si-based integrated circuits have been intensively developed over the past several decades through ultimate device scaling. However, the Si technology has reached the physical limitations of the scaling. These limitations have fuelled the search for alternative active materials (for transistors) and the introduction of optical interconnects (called "Si photonics"). A series of attempts to circumvent the Si technology limits are based on the use of III-V compound semiconductor due to their superior benefits, such as high electron mobility and direct bandgap. To use their physical properties on a Si platform, the formation of high-quality III-V films on the Si (III-V/Si) is the basic technology ; however, implementing this technology using a high-throughput process is not easy. Here, we report new concepts for an ultra-high-throughput heterogeneous integration of high-quality III-V films on the Si using the wafer bonding and epitaxial lift off (ELO) technique. We describe the ultra-fast ELO and also the re-use of the III-V donor wafer after III-V/Si formation. These approaches provide an ultra-high-throughput fabrication of III-V/Si substrates with a high-quality film, which leads to a dramatic cost reduction. As proof-of-concept devices, this paper demonstrates GaAs-based high electron mobility transistors (HEMTs), solar cells, and hetero-junction phototransistors on Si substrates.

Optical design of ZnO-based antireflective layers for enhanced GaAs solar cell performance.

A series of hierarchical ZnO-based antireflection coatings with different nanostructures (nanowires and nanosheets) is prepared hydrothermally, followed by means of RF sputtering of MgF2 layers for coaxial nanostructures. Structural analysis showed that both ZnO had a highly preferred orientation along the 〈0001〉 direction with a highly crystalline MgF2 shell coated uniformly. However, a small amount of Al was present in nanosheets, originating from Al diffusion from the Al seed layer, resulting in an increase of the optical bandgap. Compared with the nanosheet-based antireflection coatings, the nanowire-based ones exhibited a significantly lower reflectance (∼2%) in ultraviolet and visible light wavelength regions. In particular, they showed perfect light absorption at wavelength less than approximately 400 nm. However, a GaAs single junction solar cell with nanosheet-based antireflection coatings showed the largest enhancement (43.9%) in power conversion efficiency. These results show that the increase of the optical bandgap of the nanosheets by the incorporation of Al atoms allows more photons enter the active region of the solar cell, improving the performance.