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As society ages and the number of people with low vision grows, the need for low vision rehabilitation for patients is increasing.The electronic head-mounted display (HMD) aids is a new type of low vision aids, which can be divided into different types such as monocular, binocular, virtual reality (VR) and augmented reality (AR). The performance of electronic HMD visual aids is important in their development and evaluation, including improved illumination, contrast ratio, resolution, and expanded vision field.VR devices have higher resolution and richer image modes, which can effectively improve central vision acuity and contrast sensitivity, and are more suitable for static applications.AR devices do not block the patients' habitual field of vision and do not destroy stereoscopic vision, which are more suitable for dynamic applications.With the development of VR and AR display technology in recent years, electronic HMD aids have made great progress in functionality, portability and aesthetics.In most of the research, the application population of electronic HMD aids are patients with low central vision.Electronic HMD aids can improve their visual acuity, contrast sensitivity and reading ability by enlarging pictures, improving illumination and contrast ratio and enhancing contour.For patients with peripheral visual field defects, electronic HMD aids, especially AR devices, can significantly expand their peripheral visual field without blocking original visual field.However, the improvement of electronic HMD aids on daily activities, especially athletic ability, needs further research.This article summarized the types, performance and application progress of electronic HMD aids in patients with low vision.
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Objective:To observe the effects of blue light intervention on the development of optical defocus-induced myopia in guinea pigs and investigate its underlying mechanisms.Methods:Forty-eight normal-grade two-week-old tricolor guinea pigs were randomly divided into a blue light group and a white light group, with 24 animals in each group.The right eye of guinea pigs was fitted with a -5.00 D lens to establish an optical defocus model as the experimental eye, while the left eye served as the control without any covering.Before the experiment and after 8-week intervention, the refractive power of guinea pigs was measured by streak retinoscopy.The anterior chamber depth, lens thickness, and axial length were measured by A-scan ultrasonography.Corneal curvature radius was determined using a keratometer.After 8-week intervention, the guinea pigs were euthanized through overanesthesia, and the right eyeballs were enucleated and the retinas were isolated.The density of S and M cone cells of the guinea pig retinal sections were observed via immunofluorescence staining.The expression of retinal retinoic acid was assessed by high-performance liquid chromatography.The expressions of retinoic acid receptor (RAR-β) in the retina and matrix metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteinase-2 (TIMP-2), and type Ⅰ collagen in the sclera were detected by real-time fluorescence quantitative PCR.Changes in scleral thickness were observed through hematoxylin-eosin staining.The use and care of the animals complied with Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission.The study protocol was approved by the Ethics Committee of Eye and ENT Hospital of Fudan University (No.2022ETKLD10032).Results:After 8 weeks of intervention, guinea pigs in the blue light group showed (0.63±0.12)D of relative hyperopia and a deceleration of axial elongation by (0.08±0.00)mm compared with the white light group in the right eye.In the left eye, guinea pigs in the blue light group showed (0.42±0.09)D of relative hyperopia and a deceleration of axial elongation by (0.08±0.00)mm compared with the white light group.The guinea pigs in blue light group showed (1.52±0.09)D of myopia in the right eye compared with the left eye, with an increase in axial elongation of (0.06±0.00)mm.The guinea pigs in white light group showed (1.66±0.07)D of myopia in the right eye compared with the left eye, with an increase in axial elongation of (0.13±0.00)mm, and the differences were statistically significant (all at P<0.05). The density of M cone cells was lower and density of S cone cells was higher in the blue light group in the dorsal and ventral sides of the retinal sections compared with the white light group, showing statistically significant differences ( t=32.33, 52.23, 42.09, 25.02; all at P<0.05). The deceleration of myopia progression in the blue light group was strongly positively correlated with the increase in S cone cell density on the ventral side ( r=0.95, P<0.01). The expression levels of retinoic acid, RAR-β, and MMP-2 were decreased, and expression levels of TIMP-2 and type Ⅰ collagen were increased in blue light group compared with the white light group, showing statistically significant differences ( t=18.73, 7.45, 3.72, 6.19, 9.03; all at P<0.05). The scleral thickness in the blue light group was (125.0±7.8)μm, which was significantly thicker than (102.0±6.3)μm in the white light group ( t=26.93, P<0.05). Conclusions:Blue light intervention can inhibit the progression of defocus-induced myopia in guinea pigs.Refractive power changes in guinea pigs may be influenced by alterations in retinal cone cell density, retinoic acid expression, and scleral collagen expression.
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Objective To investigate the corneal posterior surface topography characteristics of keratoconus at early stages applying the Pentacam anterior segment analysis system. Methods The present study included 43 eyes of 43 patients with keratoconus at the subclinical stage (group A), 40 eyes of 40 suspected keratoconus patients (group B), and 143 normal eyes of 143 controls (group C). Based on an examination of the Pentacam anterior segment analysis system of each subject, a series of data, including the posterior surface refractive power, the posterior surface elevation were collected. The differences among the three groups, the correlation among indices, and the area under the receiver operating characteristic (ROC) curves were analyzed. Results The mean values of the posterior surface maximum refractive power in 3 groups were -6.2 D, Q=0.5;-5.6 D, Q=0.3;and -5.5 D, Q=0.3, respectively. The mean values of the posterior surface maximum elevation were 23 μm, Q=14;11 μm, Q=8.5;and 7 μm, Q=6, respectively. The posterior surface maximum refractive power and maximum elevation among three groups were statistically different. The area under ROC (AUR) of posterior maximum refractive power and the AUR of posterior maximum elevation were greater than that of other indices in the diagnosis of early keratoconus. Conclusions Based on the results from the Pentacam anterior segment analysis system, the changes of the posterior surface refractive power and elevation are important characteristics of early keratoconus.
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Objective In the early life period when eyes grow rapidly,visual experience can play an important role in axial growth and refractive development. For instance, depriving the eye of form vision during infancy will accelerate axial growth, resulting in substantial amounts of myopia, called form deprivation myopia (FDM). Similarly, imposing the eye with a negative lens produces compensating myopic growth in many species, called defocus induced myopia (DIM) . As one of the important visual experiences,color vision and its effects on eye growth deserve to be investigated. The purpose of this study was to investigate the effect of 530 nm monochromatic light and establish an innovative model of myopia in guinea pig by exposing to this monochromatic light. Methods Twenty male guinea pigs at 2 weeks old were randomly assigned to two groups (n = 10) . The experimental group was raised under the condition of 330 nm monochromatic light illumination. The control one was bred under white light illumination with 5000 k color temperature. These guinea pigs were raised in a specially designed cage. The light source was provided by specially made LEDs (green: peak value 530 nm and half bandwidth 30 nm; white: color temperature 5000 K) . The illumination parameters of the two groups were identical and the light quantum number was 3 x 10~(-4)μmol·cm~(-2)·s~(-1) . Through measuring,the irradiance value was 0.150 mW·cm~(-2) for green light and 0.247 mW·cm~(-2) for white light approximately. All animals were kept under a 12/12 h light/dark cycle (light: 8 a.m. - 8 p.m. ) ,in the temperature of 22℃ - 26℃ and a relative humidity of 55% -65% . Both groups underwent biometric measurement including refraction,corneal curvature and axial length,etc. before and after twelve weeks treatment. The refraction was examined using a streak rednoscope and trial lenses in a dark room one hour after topically administering a cycloplegic eye drop. The radius of comeal curvature was measured with a keratometer (Topcon OM-4, Japan) and axial components was measured by A-scan ultrasonagraphy ( Opticon Hiscan A/B).Repeated measurements were undertaken. Only the right eye's parameters of each guinea pig were used for analysis. Unpaired (-tests were used in all comparisons between the two groups of eyes with a statistical analysis software (Stata, version 7.0) . Results Before treatment, the refraction of experimental group was 4.6 ± 0.59 D.and that of the control group was 4.63 ± 0.48 D. The axial and vitreous body length was 7.48 ±0.11 mm and 3.16 ±0.07 mm in the experimental group,respectively,and 7.55 ±0.16 mm,3.21 ±0.09 mm in the control. The differences between the biometric parameters of the two groups including refraction, comeal curvature and axial components were not significant ( P > 0.05) . However,after a twelve-week exposure, the variation of refraction in the experimental group was -3.125 ± 0.76 D,and - 1.075 ± 0.71 D was observed in the control group. There was a 2.0 D myopia in the experimental group compared with the control. Axial length grew 0.98 ± 0.13 mm in the experimental group and 0.77 ± 0.22 mm in the control. Vitreous body extended to 0.33 ± 0.14 mm and 0.13 ± 0.14 mm in the two groups, respectively. The refraction of the experimental group shifted more towards myopia ( P < 0.0001) accompanied with a more accelerated speed of axial growth and vitreous body's extension ( P < 0.05) compared with that of the control group. There were no significant differences in the radius of comeal curvature, the depth of anterior chamber and the lens thickness between the eyes of the two groups at the end of the experiment ( P > 0.05) . Conclusion The 530 run monochromatic light can accelerate the prolongation of axial length and vitreous body inducing axial myopia in guinea pigs.
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Wound healing in the human cornea has distinctive characteristics in comparison to most other tissues in the body.The corneal wound healing response is a remarkably complex cascade mediated by cytokines,growth factors,and chemokines.The interactions in the epithelial,stromal,neural,lacrimal gland,immune cells are interwoven in the corneal response to injury.Corneal epithelial cells and basement membrane play important roles in this process.However,both of them are usually impaired during the procedures of excimer laser refractive surgery for myopia,hyperopia,or astigmatism,and complications such as overcorrection,undercorrection,regression,refractive instability,and haze may occur after surgery.A complete corneal wound healing process,the biologic and molecular processes that contribute to the healing response,and anomalies that lead to complications are critical for improving the efficacy and safety of excimer laser refractive surgical procedures.
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Objective To evaluate the effect of modified suction ring in laser in situ keratomileusis(LASIK) for special eyeballs.Methods Those eyeballs that couldn't be sucked successfully with regular suction ring were performed with modified suction ring, and the characteristic of those eyes was analyzed.Results Fifteen eyes of 9 cases were included in this study and were sucked successfully with modified suction ring with intact corneal flap.Eight eyes of 5 cases had small corneal power especially in the peripheral section. The corneal power in the peripheral section of 7 eyes was less than 41D. Corneal diameter of 1 eye was 9.5mm and 6 eyes of 3 cases had small palpebral fissure.Conclusions The modified suction ring is safe and effective for those eyes with flat cornea, small corneal diameter and small palpebral fissure.
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Objective:To observe the lens zonule infrastructure changes in experimental myopia. Methods; The eye lids were sutured to induce the myopia in guinea pigs and the zonule ultrastructure changes were observed. Results: There were significant differences in the eye axial length and diopter between lid-sutured eyes and controls(P