生物医用眼科材料的研究

主要综述了用于眼科的生物医用材料的种类、结构特点及其在眼科中应用的性能,重点介绍了用于人工角膜的光学镜柱材料和支架材料、人工晶状体材料、人工玻璃体材料、人工眼球义眼台和义眼材料、人工泪道和泪液材料、角膜接触镜材料及眼科药物载体材料,展望了生物医用眼科材料的发展方向.     

A modified double-torsion method for measuring the fracture toughness of polymeric ophthalmic lenses

A modified double torsion test has been developed to measure the fracture toughness of polymeric ophthalmic lenses. Measurements on PMMA sheet using both conventional double torsion and compact tension geometries gave the same fracture toughnesses as lenses made from the PMMA sheet and tested in the modified double torsion test. Tests on plano lenses made of commercial ophthalmic lens materials showed that the measured fracture toughness was independent of lens diameter and thickness and also crack length provided the notch length was within specified bounds. Test results showed quite small scatter. Because of the reproducibility and simplicity of the test, the modified double torsion test should provide a more reliable and cheaper measure of the impact performance of the lenses than does the existing drop weight test.     

Calculation of optical imbalances in ophthalmic lenses using a new algorithm based on the local dioptric power matrix formalism.

We present a new algorithm to calculate the optical imbalances and differential prismatic effects that appear when two eyes look at an object through correcting eyeglasses. These are important magnitudes in ophthalmic optics because large amounts of them will disturb the binocular vision of the spectacle wearer. As a practical application of our algorithm, the distribution of optical imbalances and differential prismatic powers for a pair of progressive addition lenses has been calculated, and we obtain information about the effects of this kind of lens on the binocular vision of the wearer.     

Visualizing vitreous using quantum dots as imaging agents

Vitreous is transparent tissue located between the lens and the retina of the eye, thus, difficult to look at by even ophthalmological microscope. But vitreous is connected with some sight-threatening eye diseases, for example, retinal detachment, macular hole, epi-retinal membrane, and so forth. Quantum dots (QDs) have been applied to a wide range of biological studies by taking advantage of their fluorescence properties. We established a novel technique of aqueous colloidal QD (ACQD) as a vitreous lesion detector. When compared with some conventional dyes used for clinical situation, i.e. fluorescein, indocyanine green, and triamcinolone acetonide, ACQD exerted a higher performance to detect a Weiss Ring. Furthermore ACQD is also effective to perform vitrectomy, an eye surgery to cut and eliminate vitreous. Some functional structures in vitreous are detected clearly when ACQD was injected into an enucleated porcine eye. We demonstrated that ACQD enabled any ophthalmic surgeon to perform vitrectomy reliably, easily, and more safely. Taken together, the ACQD-oriented vitreous staining system will promote ophthalmological science, and it will raise the cure rate of eye diseases     

Microfluidic Contact Lenses

Contact lens is a ubiquitous technology used for vision correction and cosmetics. Sensing in contact lenses has emerged as a potential platform for minimally invasive point‐of‐care diagnostics. Here, a microlithography method is developed to fabricate microconcavities and microchannels in a hydrogel‐based contact lens via a combination of laser patterning and embedded templating. Optical microlithography parameters influencing the formation of microconcavities including ablation power (4.3 W) and beam speed (50 mm s^?1) are optimized to control the microconcavity depth (100 µm) and diameter (1.5 mm). The fiber templating method allows the production of microchannels having a diameter range of 100–150 µm. Leak‐proof microchannel and microconcavity connections in contact lenses are validated through flow testing of artificial tear containing fluorescent microbeads (Ø = 1–2 µm). The microconcavities of contact lenses are functionalized with multiplexed fluorophores (2 µL) to demonstrate optical excitation and emission capability within the visible spectrum. The fabricated microfluidic contact lenses may have applications in ophthalmic monitoring of metabolic disorders at point‐of‐care settings and controlled drug release for therapeutics.     

柱面型声透镜设计及验证

介绍了声透镜波束形成的基本原理和分析方法,分析了柱面型声透镜的设计方法。用ZEMAX光学软件设计并用ABS塑料制作了一个组合声透镜,在水池中完成其多个参数的测量。在频率500kHz和20°的视场范围内该声透镜的角度分辨率为l°。实验结果表明,该声透镜系统的波束宽度、旁瓣高度和视场范围均达到了设计要求．并很好的验证了柱面型声透镜的聚焦性能。     

Plasmapolymerisation für die Hartbeschichtung von Kunststofflinsen

The use of plastic as a substrate material for optical lenses has been increasing in importance due to smaller density, simpler machining and lower price. However scratches present a major problem wherever the lens surface is exposed to the environment. Various processes have thus been developed to protect the surfaces with hard coatings. The most common technique is the dipping process while spinning or spraying are other methodsto apply lacquer. Common to all these techniques are the required post treatments such as drying and heat or UV curing. Safety considerations as well as the long processing time and the handling required between the different steps, gave rise to the development of new technologies. Plasma polymerization, a technology relying on plasma enhanced chemical vapor deposition (PECVD), is used to deposit dense organic layers with reproducible, well defined surface properties. In contrast to dip coating, plasma polymerization even coats strongly curved structures with good uniformity. This is important for bifocal or trifocal lenses, featuring sharp edges on the surface. Due to the wide range of refraction indexes (about n = 1.5–1.8) available by using different monomers, even the latest high index materials can be coated without disturbing interference fringes. After a survey of plasma polymerization basics, some aspects of industrial equipment and processes for ophthalmic applications are presented. An outlook into the future of plasma polymerization for optical applications concludes the paper.     

Optical Systems for Use at Low Light Levels

The development of image intensifier tubes and their application in instruments for operation under low light-level conditions created the need for optics which require specific properties. Recognition of the problems involved when combining a lens with a tube results in general requirements for the lens, some of which are different from those in standard lens design. Refined basic lens configurations and new systems have been introduced in this field, e.g. refractive and catadioptric lenses. Some examples of their performance are shown. In addition relay lenses having an extremely high speed have been realized for applications mainly for x-ray image intensifier systems. Single-tube instruments with a bi-ocular eyepiece are shown to have many advantages over the double-tube binocular.     

Numerical implementation of generalized Coddington equations for ophthalmic lens design

A method for general implementation in any software platform of the generalized Coddington equations is presented, developed, and validated within a Matlab environment. The ophthalmic lens design strategy is presented thoroughly, and the basic concepts of generalized ray tracing are introduced. The methodology for ray tracing is shown to include two inter-related processes. Firstly, finite ray tracing is used to provide the main direction of propagation of the considered ray at the incidence point of interest. Afterwards, generalized ray tracing provides the principal curvatures of the local wavefront at that point, and its orientation after being refracted by the lens. The curvature values of the local wavefront are interpreted as the sagital and tangential powers of the lens at the point of interest. The proposed approach is validated using a double-check of the calculated lens performance in the spherical lens case: while finite ray tracing is validated using a commercial ray tracing software, generalized ray tracing is validated using a software application for ophthalmic lens design based on the classical version of Coddington equations. Equations of the complete tracing process are developed in detail for the case of generic astigmatic ophthalmic lenses as an example. Three-dimensional representation of the sagital and tangential powers of the ophthalmic lens at all directions of gaze then becomes possible, and results are presented for lenses with different geometries.     

中 国 眼 科 现 状

改革开放以来，我国眼科资源取得较快增长。随着人们生活水平的提高，白内障、角膜病、沙眼、青光眼、眼底病、屈光不正等主要眼病的患病率也有较大变化。文章根据最新资料，从眼科临床和基础研究两个方面介绍了我国白内障、角膜病、屈光不正、眼底病、青光眼五种主要致盲眼病的现状。在部分城市医院已拥有国际上最先进的检查治疗设备和国际一流水平的优秀专家，但平均水平和发达国家尚有较大差距，主要设备完全依靠进口。在眼科基础研究方面，一些重要研究领域未取得突出的创新成果和重大建树，总体优势还未形成，需要在政策导向和政府投入等方面加大力度。     

Optical characterization of ophthalmic lenses by means of modulation transfer function determination from a laser speckle pattern

A method is presented for measuring the modulation transfer function of ophthalmic lenses by use of the generation of laser speckle with an integrating sphere. The measurements are performed with a rectangular double-slit aperture positioned at the output port of the integrating sphere. The distance between the lens and the detector determines the spatial frequency being tested; therefore high frequencies are tested close to the lens and low frequencies are tested far away from the lens. We can conclude that the double-slit method can be a versatile technique for comparing the optical quality of ophthalmic lenses from different makers.     

Stability storage and testing of ophthalmic products for global registration

Regulatory stability testing requirements for various types of ophthalmic products, including eyedrops, eye ointments, ophthalmic inserts, injections, irrigating solutions, lens washes, and lenses, are not always straightforward. The International Conference on Harmonisation (ICH) guidelines do not completely address all of the stability conditions required for these types of pharmaceutical products and medical devices; regulatory agencies around the world still differ on the exact data requirements, storage conditions (especially temperature and humidity conditions), and certain testing methods. These uncertainties make the development of a global ophthalmic product very difficult. This article reviews many of the appropriate, internationally recognized, regulatory guidelines and many of the important points to consider in stability studies for new ophthalmic products. Discussions of regulatory experiences and Expert Reports provide insight to common questions frequently asked by regulatory agencies on these types of products.     

Dynamic eye model for adaptive optics testing

An artificial dynamic eye model is proposed. The prototype enabled us to introduce temporal variations in defocus and spherical aberration, resembling those typically found in the human eye. The eye model consisted of a meniscus lens together with a modal liquid crystal lens with controllable focus. A diffuser placed at a fixed distance from the lenses acted as the artificial retina. Developed software allowed the user to precisely control the dynamic generation of aberrations. In addition, different refractive errors could simultaneously be emulated by varying the distance between the components of the model. The artificial eye was first used as a dynamic generator of both spherical aberration and defocus, imitating the behavior of a real eye. The artificial eye was implemented in an adaptive optics system designed for the human eye. The system incorporated an electrostatic deformable mirror and a Hartmann-Shack wavefront sensor. Results with and without real time closed-loop aberration correction were obtained. The use of the dynamic artificial eye could be quite useful for testing and evaluating adaptive optics instruments for ophthalmic applications.     

Ophthalmic application of poly(HEMA)s containing nanoparticles and dimethylacrylamide

High functional ophthalmic lens materials, poly(HEMA-co-MMA)s were prepared by the copolymerization of HEMA, MMA, MA, EDGMA, and N,N-dimethylacrylamide in the presence of platinum nanoparticles with antimicrobial properties. The hydrophilic monomer N,N-dimethylacrylamide has excellent biocompatibility and oxygen transmissibility. The combination where platinum nanoparticles were added produced a colorless transparent lens. The water contents were in the range of 36.68-44.08% and the refractive index was measured to be in the range of 1.424-1.436. Meanwhile, the oxygen transmissibility ranged from 11.13 x 10(-11) to 17.63 x 10(-11) (cm2/sec) (mlO2/ml x mm Hg) increased with increasing the addition ratio of N,N-dimethylacrylamide. The physical properties measurements of the produced polymers showed that the nanoparticles did not show significant effect on the water content and refractive index of the hydrogel contact lens, but the materials effected to reduce oxygen permeability to a certain extent. The copolymers have excellent oxygen permeability, indicating that the material can be used to fabricate hydrogel contact lenses with high oxygen transmissibility.     

Large-aperture automatic focimeter for the measurement of optical power and other optical characteristics of ophthalmic lenses

We propose an optical apparatus enabling the measurement of spherical power, cylindrical power, and optical center coordinates of ophthalmic lenses. The main advantage of this new focimeter is to provide a full bidimensional mapping of the characteristics of ophthalmic glasses. This is made possible thanks to the use of a large-area and high-resolution position-sensitive detector. We describe the measurement principle and present some typical mappings, particularly for progressive lenses. We then discuss the advantages in terms of speed and versatility of such a focimeter for the measurement of complex lens mappings.     

Investigation of shrinkage and cracking of ophthalmic lens coating by a cycle test of UV radiation and high humidity

This paper presents some ophthalmic lens coating failures such as shrinkage, cracking, and cracking with delamination caused by UV radiation, elevated temperature, and moisture. These phenomena are caused by: 1) interactions at the interface between the plastic substrate and the hard coating (HC), and 2) plastic deformation with stress and relaxation of the HC/substrate interface. This phenomenon leads to an understanding of the mechanical properties of ophthalmic lenses through a QUV test which is found to be a useful method in developing better ophthalmic lens systems. The coating failures were investigated by means of different analysis techniques including optical microscope, scanning electron microscope, atomic force microscope, thermo mechanical analysis, and dynamic secondary ion mass spectrometry.     

Adaptive optics and vision

It has long been recognised that the optical quality of the human eye is far from diffraction limited. This affects our visual acuity and severely limits the resolution at which images of the living retina can be obtained. Adaptive optics is a technique that can correct for the eye's aberrations and provide diffraction limited resolution. The origins of the technique lie in astronomy, but it was successfully adapted to the human eye just over 10 years ago. Since then there have been rapid developments in the field of adaptive optics and vision science. In vivo images of the retina can now be routinely achieved with unprecedented resolution. Sophisticated experiments can be performed to gain a deeper knowledge of the interaction of neural retinal architecture and visual perception. This article presents the theory behind adaptive optics for the human eye and reviews the developments in this field to date.     

Integrated light scattering as a function of wavelength in donor lenses.

The purpose of this work is to investigate the light-scattering properties of excised eye lenses with intact lens capsules--more specifically, to compare light scattering with light transmission at different wavelengths in aging and cataractous lenses. A lens is positioned at its focal-length distance from an optical fiber end and collimates the light from one of five laser lines (458-633 nm). By use of an integrating sphere with an extra circular port, the collimated directly transmitted light can be separated from the scattered light. For lenses with low light-scattering levels, integrated scattering showed a dependence on wavelength, but when light scattering increased the wavelength difference tended to level out. Despite the higher percentage of lens light scattering at lower wavelengths, when calculated as an "effective light scattering" (compensated for light transmission), more scattered light actually falls toward the retina at longer wavelengths.     

Computer Generated Diffractive Multi-focal Lens

The method has been proposed for computing Fresnel-type multi-focal lenses on the basis of special-type phase nonlinearity. A multi-focal lens is represented as a mathematical superposition of a thin lens and nonlinearity distorted Fresnel lens. Selection of the nonlinearity type is reduced to the problem of the groove form determination for the phase diffraction grating with pre-set energy distribution between orders. In particular, bi-focal lens and seven-focal lens have been investigated.