View clinical trials related to Myopia.
Filter by:Glaucoma is the leading cause of irreversible blindness worldwide. Although the pathogenesis remains unclear, pathologic increase in intraocular pressure (IOP) due to blocked aqueous outflow through the trabecular-Schlemm canal is known to be an important risk factor, and reduction of IOP is the only clinically validated way to retard the progression of OAG. Ciliary muscle plays a central role in the trabecular meshwork-Schlemm canal outflow pathway. Clinical evidence suggests that ciliary muscle contraction stimulated by cholinergic receptor agonist and retraction of ciliary body position after cataract surgery can dilate the lumen of Schlemm canal and reduce IOP. Currently, Ultrasound biomicroscopy (UBM) can obtain two-dimensional images of the anterior segment using high-frequency Ultrasound transducers in medical imaging studies of the ciliary body - trabecular meshwork -Schlemm canal complex. UBM has better tissue penetration than Optical coherence tomography (OCT) and can image the ciliary body better, but it has a lower resolution (30um to 50um) and is poor at imaging tiny tissues such as trabecular meshwork and Schlemm canal. The latest swept-source OCT (SS-OCT) has faster image capture rate (1000000 A scans/SEC), stronger penetration and higher resolution (8um axial resolution and 20um transverse resolution). The structure and morphology of ciliary body-trabecular meshwork-Schlemm canal complex can be clearly photographed. The investigators intend to use CASIA2 to image the ciliary body-trabecular meshwork-Schlemm canal complex before and after administration of pilocarpine in healthy individuals and patients with glaucoma to assess the effect of pilocarpine on the anatomy of the ciliary body-trabecular meshwork-Schlemm canal complex.
The study aims to examine how the vascular layer of the eyeball (choroidal layer) responds when part of the visual field is exposed to specially generated visual stimulus. The study goal will be accomplished by producing specific blur visual stimulus at a particular visual field position and measure any consistent thickness change pattern in the choroidal layer. We propose to test the hypothesis that regional changes in the choroidal thickness may be induced differently after short-term exposure to specific visual stimuli.
The IOL-capsular complex is formed after cataract surgery and intraocular lens (IOL) implantation.Early postoperative mechanical wrapping of the anterior and posterior capsules plays a significant role in preventing IOL decentration and tilt, as well as formation of the IOL-capsular complex which reduces the incidence of posterior cataract opacity. Capsular tension rings were first introduced in the early 1990s for loosening and tightening the lens bag and maintaining the equatorial contour of the bag after cataract surgery.Today, capsular tension rings of many different designs are in use.The capsular tension rings can be used in eyes with fragile and split zonular fibers, as well as pseudoexfoliation, high myopia, Marfan syndrome, mature cataract and lens subluxation.The capsular tension ring reduces the incidence of decentration and tilt of the IOL by reducing capsular contraction. In addition, multi-focus IOL implantation combine with capsular tension ring result in smaller high-order aberrations in our eyes compared to cataract surgery with multi-focus IOL implantation alone.For patients with high myopia, they often have a longer axial length and a larger capsule diameter, which reduces the rotational stability of the IOL and may lead to tilt ,decentration and displacement of IOL.Currently, there is no literature guidance to compare the results of cataract surgery combined with or without capsular tension ring implantation in patients with high myopia.Our hospital has Swept-source Optical Coherence Tomography ( SS-OCT,Casia2, TOMEY, Japan), which can accurately photograph the process of IOL capsule bending and the changes of lens position after cataract surgery. SS-OCT can be used to evaluate the influence of capsular tension ring on the dynamic changes of IOL-capsular complex in patients with high myopia after cataract surgery.
The last decades have seen a significant increase in myopia in children and young adults. Possible cause: increased near-work (school, computer, smartphone). Rationale: Reading glasses support the accommodative effort of the eyes. By wearing reading glasses, there is less interference with the young eye´s physiological axial growth despite increased near-work. Main objective: does the use of reading glasses during near-work in children and adolescents reduce the incidence of myopia.
the purpose of the study is to compare the accuracy of optical and ultrasonic biometry in intraocular lens (IOL) calculation in high myopic cataractous patients
This study aims to perform biomechanical tests on extracted CLEAR lenticles that are routinely discarded after surgery. The investigators also aim to perform Brillouin microscopy to get an in-vivo assessment of the patient's cornea preoperatively and to correlate this data with the postoperative characterization of the extracted corneal lenticule. The characterization will be done with established biomechanical and morphologic tests.
The prevalence of myopia is seemingly increasing, and it is one of the major causes of blindness. High myopia is defined as a refractive error with spherical equivalent exceeding -6 diopters and/or the axial length longer than 26.5 mm. The global prevalence of high myopia is estimated to rise from 2.7% of the world population in 2010 to 9.8% of the world population in 2050. High myopia is characterized by axial length elongation, and consequent stretching of the posterior eye wall (thin retina and choroid). There are many complications of high myopia such as posterior staphyloma, lacquer cracks and myopic choroidal neovascularization. Normal labour may cause the ocular complication in pregnant women with high myopia, such as macular hemorrhage. Therefore, the caesarean section with epidural anesthesia is recommended. Moreover, there is no standard screening guideline for pregnant women with high myopia.
Retinal imaging is a corner stone in diagnosis of most retinal disorders. Standard imaging techniques e.g. fluorescein angiography and color fundus photography have a lot of limitations including limited resolution, invasive nature in cases of fluorescein angiography, and inability to segment the retina, accordingly, and only 2D image is provided. Optical coherence tomography angiography (OCTA) is a recent noninvasive imaging technique that allows for volumetric visualization of eye vasculature. OCTA has shown promise in better elucidating the pathophysiology of several retinal vascular diseases. Swept-source OCTA uses long wavelength ̰ 1,050nm, which can penetrate through deeper layers of the eye and can traverse opacities of media such as cataracts, hemorrhages and vitreous opacities. Optical coherence tomographic angiograms can further be manually or automatically segmented with preprogrammed software to highlight individual layers of the retina, optic nerve head choriocapillaris, and choroid. The user can either analyze en face images extending from the inner limiting membrane to choroid or use automated views to locate a vascular or structural lesion within the retina. Different quantitative metrics has been extracted from enface OCTA images including vessel density, FAZ area, choriocapillaries flow deficit, intercapillary area and fractal dimension. These metrics are helpful in evaluation the retinal perfusion and used by physicians to assess various retinal vascular disorders. Although some previous literatures had discussed the repeatability of OCTA metrics, however, comprehensive evaluation of widely used metrics in various retinal condition has not be done. Additionally, recent data suggest that various methods of calculation of these metrics my yield final different results of the same metric.
In recent decade, a major improvement in vitreoretinal surgery was the use of small gauge surgical systems that improved the safety of vitrectomy and also reduced the surgical time. However, there were still some concerns regarding small gauge vitrectomy system, especially 27-gauge system, in the stability of its instruments and the efficacy of removing vitreous during surgery. Although there were some studies that had reported the surgical outcomes of 27G vitrectomy system, none had focused on patients with high myopia. The highly myopic patients usually had thinner sclera, which was a risk factor for wound leakage after sutureless vitrectomy, they also had longer axial length which would make the surgical procedure more difficult especially in macular surgery. Based on previous clinical finding, gas leakage was 36.4% in 25G , while 27G sclerotomy showing less leakage comparing to larger gauge sclerotomy, the investigators believe 27G may have its clinical advantages in overcoming the thinner sclera of high myopia, and show the superiority of leakage control. Hypothesis: The 27G vitrectomy system has lower sclerotomy wound leakage rate compared with 25G system
Myopia is a global healthy concern, especially the high myopia and pathological myopia among Asian populations. However, its mechanism still remains largely unclear. Recent findings suggested choroidal changes might be related to the development of myopia. This study is to useOCT angiography (OCT-A) to investigate parapapillary choroidal microvasculature change in myopic eyes, and try to find the cause-and-effect relationship between choroidal change and the development of myopia.