人眼高阶像差与调节间关系的研究进展

目的 波阵面像差是评价眼睛光学性能的重要客观指标.人眼作为动态变化的光学系统,其调节和高阶像差间相互作用,影响视网膜图像质量.研究此二者间的关系,可以更合理解释复杂视觉问题.本文就人眼高阶像差的调节线索作用,伴随调节的改变,调节静止时的高阶像差微波动,以及近视性屈光不正与调节相关的高阶像差变化做一综述.     

应当重视波前像差的应用研究

近年来随着角膜屈光手术的不断发展 ,波前像差成为目前眼视光学研究的热点之一。但直至目前 ,许多人对波前像差的概念还不甚明了 ,对其应用也只局限于准分子激光治疗屈光不正时的个体化切削。本期发表了任泽钦的“波前的概念及其与屈光系统的关系”和王雁等“人眼视觉光学波阵面像差的研究和进展”文章 ,旨在促进波前像差知识的普及和研究的进一步深入。波前和波前像差作为物理学概念 ,早已存在。光线是一种向前行进的电磁波。在某一时点 ,振动传播方向上同位相的点能形成一个面 ,称为波阵面 ,简称为波前。如果入射光为单色近轴光 ,物体上的…     

波阵面像差技术在临床上的应用

介绍波阵面像差技术的基本概念、评价方法及临床应用。波阵面像差技术是目前临床上较为关注的一项技术 ,不仅可用于检查屈光手术前后的波阵面像差的改变 ,还可以指导个体化切削 ,提高屈光手术后的眼视觉质量。此外 ,这一技术可用于评估配戴各种不同角膜接触镜前后的波阵面像差的改变 ,评估白内障、青光眼以及其他角膜手术的波阵面像差的改变等等     

人工晶状体研究最新进展

一、非球面人工晶状体 波阵面像差检测结果表明，功能性视觉的降低与晶状体的球差增加密切相关。随着波阵面像差检测技术的不断提高，临床认识到对比敏感度和功能性视觉质量与高阶像差密切相关。人眼角膜存在正球差，而年轻人的晶状体则存在负球差，两者相互抵消；随着年龄的增长，老化的晶状体由于核硬化以及屈光指数改变等原因，其球差逐渐增大，失去了补偿角膜正球差的能力。传统的人工晶状体增加了人眼的球面像差，降低了视网膜的成像质量，从而影响了功能性视觉。非球面人工晶状体能够消除部分像差，在一定程度上提高了光学质量，可产生良好的视网膜图像。     

瞳孔直径和调节刺激对年轻人正视眼单色高阶波阵面像差的影响

目的 探讨不同瞳孔直径下,调节对年轻正视眼单色高阶波阵面像差的影响.方法 干预性试验研究设计.使用光线追踪原理的波阵面像差仪测量12只年轻正视眼自然生理状态,在4.0、3.0、2.0 mm瞳孔直径下,0.00、1.00、2.00、3.00和4.00 D调节刺激下的单色波阵面像差.采用单因素方差分析及最小显著差法多重比较,对获得的数据进行统计学分析.结果 调节松弛下正视眼的总高阶像差、总彗差、总高阶散光、总球差和总三叶草像差的均方根值均随瞳孔直径减小而减小.在4.0、3.0、2.0mm瞳孔直径下,总彗差是调节松弛状态总高阶像差的最主要成分;总高阶像差仅在调节刺激达4.00 D时升高(P<0.05).瞳孔直径4.0 mm时,随调节刺激增加,4阶球差出现从大到小、从正值向负值的变化,但在瞳孔直径为3.0和2.0 mm时,4阶球差始终为正值.3阶水平方向三叶草像差在4.0、3.0、2.0 mm瞳孔直径下均表现出从负值向正值变化的规律.结论 不同瞳孔直径不同调节刺激下,正视眼各项单色高阶波阵面像差发生了不同规律和方向的变化.高阶像差在调节过程变化的意义和对不同注视距离视觉处理过程的作用有待于进一步研究,波阵面像差的研究将从单纯的消除向优化方向发展.     

眼的高阶像差与视觉质量

近年来,随着准分子激光屈光手术的广泛开展,许多手术后的并发症如眩光、光晕及夜视力下降等问题开始涌现.而波阵面像差的提出和研究为解决上述问题提供了新思路.本文就高阶像差的研究进展及与视觉质量的关系等作一综述.     

波前像差技术及其在屈光手术中的应用

介绍测量人眼像差的几种主要方法及其在屈光手术中的应用。以Hartmann-Schack、Tsherning or Scheiner-Smirnov theories理论为基础的像差仪或像差镜能测量人眼屈光系统所有的像差,所得到的数据与屈光手术系统相结合后设计个性化切削方案,从而能提高PRK、LASIK等屈光手术术后的视觉质量。     

非球面人工晶状体的设计与应用

非球面人工晶状体（intraocular lens，IOL）有着减少术后眼球面像差的作用，理论上能够带来更好的光学质量和视觉功能，因而在波阵面理论广泛普及的今天已受到越来越多的关注，不同设计理念的非球面IOL相继被推出。     

《波前像差与临床视觉矫正》一书出版

由王雁教授、赵堪兴教授为主编,国内、外视觉领域著名专家和知名学者参与共同编写的《波前像差与临床视觉矫正》一书已由人民卫生出版社正式出版。目前视觉科学领域发展较快,许多新的视觉理论和知识已渗透到眼科各个专业中,在我国目前尚缺少一本系统介绍人眼视觉光学基础及波前像差等临床应用的专业书籍。     

《波前像差与临床视觉矫正》一书出版

由王雁教授、赵堪兴教授为主编,国内、外视觉领域著名专家和知名学者参与共同编写的《波前像差与临床视觉矫正》一书已由人民卫生出版社正式出版。目前视觉科学领域发展较快,许多新的视觉理论和知识已渗透到眼科各个专业中,在我国目前尚缺少一本系统介绍人眼视觉光学基础及波前像差等临床应用的专业书籍。     

Changes in Bruch's membrane in experimental hypercholesteremia in rats

PURPOSE: We investigated the effect of high cholesterol diet for the aging changes in Bruch's membrane of rats. METHODS: After feeding a 4% cholesterol diet for 15 weeks to three young rats 3 months old and four aged rats 23 months old, we observed the morphological changes of Bruch's membrane by electron microscopy, and made a comparison with rats fed an ordinary diet. RESULTS: In one young rat fed a high-cholesterol diet, the endothelial basement membrane of the choriocapillaris formed multiple folds separated from the plasma membrane of the endothelium and showed lamellar thickening and crack in some areas. The elastic fiber layer in Bruch's membrane disappeared partly and some new microfibrils appeared. In one aged rat fed a high-cholesterol diet, the endothelial basement membrane of the choriocapillaris showed more lamellar thickening with lumps in some parts. Compared with rats fed an ordinary diet, rats fed a high-cholesterol diet showed thickening of the basement membrane and the changes were more severe. CONCLUSIONS: Our data indicated that high-cholesterol diet might promote age-related changes of Bruch's membrane.     

Advances in imaging in oculoplastics

Color Doppler imaging, computed tomography (CT) and magnetic resonance (MR) imaging are the most precious imaging tools for the clinician in the field of oculoplastics. Orbital and facial vasculature, with its dynamic changes and flow velocities seen in orbital varices, carotid-cavernous fistulas, and dural cavernous arteriovenous malformations, is best detected by Color Doppler imaging. Computed tomography remains the dominant imaging modality in the evaluation of orbital trauma. Helical CT axial scanning with multiplanar reconstruction and three-dimensional CT imaging are most helpful in assessing iatrogenic, traumatogenic, and teratogenic orbital abnormalities. Despite its poor histologic specificity, MR imaging provides superior soft tissue contrast, and contrast-enhanced MR imaging has an established role regarding soft tissue tumor infiltration. The greatest value of MR studies in the evaluation of orbital and palpebral tumors is that it has the capacity to show the precise relation between lesions and adjacent structures before the clinician contemplates a surgical approach. Finally, contrast-enhanced MR imaging proved to be a valuable vascularization indicator based upon the extent of relative enhancement within porous orbital implant in anophthalmic socket.     

Follow-up studies in pattern VECP in demyelinating diseases in children

Spectral sensitivity functions and the transient decrease of sensitivity to short wavelengths after the offset of yellow light (transient tritanopia) were measured by increment threshold techniques in patients suffering from hereditary macular degenerations. Color vision defects were determined by arrangement tests and the anomaloscope. Central areolar choroidal dystrophy was found to produce a mild protan defect and to reduce foveal spectral sensitivity throughout the visible spectrum by a factor of 100; it also abolishes transient tritanopia. Electroretinogram (ERG) was normal, electrooculogram (EOG) subnormal. Stargardt's disease, despite numerous fluorescent macular spots, does not abolish transient tritanopia nor does it reduce spectral sensitivity, although scotopic matches were performed on the Nagel anomaloscope. Only in severe, advanced cases was transient tritanopia reduced and spectral sensitivity found to follow the absorption spectrum of rods. Routine ERGs and EOGs were normal. Vitelliform macular degeneration, despite the ophthalmoscopically pronounced dystrophic macula, produced only very small changes in spectral sensitivity and transient tritanopia, although a widened matching range on the Nagel anomaloscope and electrophysiological abnormalities were found. Apparently damage of the retinal circuit which connects long and short wavelength-sensitive cones, caused by hereditary conditions, is different from that caused by retinotoxic drugs.     

Refractive error in children in a rural population in India

PURPOSE: To assess the prevalence of refractive error and related visual impairment in school-aged children in the rural population of the Mahabubnagar district in the southern Indian state of Andhra Pradesh. METHODS: Random selection of village-based clusters was used to identify a sample of children 7 to 15 years of age. From April 2000 through February 2001, children in the 25 selected clusters were enumerated in a door-to-door survey and examined at a rural eye center in the district. The examination included visual acuity measurements, ocular motility evaluation, retinoscopy and autorefraction under cycloplegia, and examination of the anterior segment, media, and fundus. Myopia was defined as spherical equivalent refractive error of at least -0.50 D and hyperopia as +2.00 D or more. Children with reduced vision and a sample of those with normal vision underwent independent replicate examinations for quality assurance in seven clusters. RESULTS: A total of 4414 children from 4876 households was enumerated, and 4074 (92.3%) were examined. The prevalence of uncorrected, baseline (presenting), and best corrected visual acuity of 20/40 or worse in the better eye was 2.7%, 2.6%, and 0.78%, respectively. Refractive error was the cause in 61% of eyes with vision impairment, amblyopia in 12%, other causes in 15%, and unexplained causes in the remaining 13%. A gradual shift toward less-positive values of refractive error occurred with increasing age in both boys and girls. Myopia in one or both eyes was present in 4.1% of the children. Myopia risk was associated with female gender and having a father with a higher level of schooling. Higher risk of myopia in children of older age was of borderline statistical significance (P = 0.069). Hyperopia in at least one eye was present in 0.8% of children, with no significant predictors. CONCLUSIONS: Refractive error was the main cause of visual impairment in children aged between 7 and 15 years in rural India. There was a benefit of spectacles in 70% of those who had visual acuity of 20/40 or worse in the better eye at baseline examination. Because visual impairment can have a significant impact on a child's life in terms of education and development, it is important that effective strategies be developed to eliminate this easily treated cause of visual impairment.     

Vitrectomy in traumatic cataracts and in the complications of surgery in congenital cataract in children

Vitrectomies were carried out in 35 children with traumatic cataracts and complications of surgery for cataracts, caused by injury to the posterior lenticular capsule and incorporation of its fragments to the vitreous. Complete removal of lenticular rudiments rapidly eliminated phacogenic iridocyclitis and improved visual acuity. Improvement of visual functions was attained in 66.6% cases; in 33.4% cases visual acuity did not change. Hemorrhages to the vitreous cavity occurred in 4 cases with pronounced iridocyclitis; therefore, a corneal approach is preferable for cases with pronounced iridocyclitis.     

Refractive error in children in an urban population in New Delhi

PURPOSE: To assess the prevalence of refractive error and related visual impairment in school-aged children in an urban population in New Delhi, India. METHODS: Random selection of geographically defined clusters was used to identify a sample of children 5 to 15 years of age. From December 2000 through March 2001, children in 22 selected clusters were enumerated through a door-to-door survey and examined at a local facility. The examination included visual acuity measurements, ocular motility evaluation, retinoscopy and autorefraction under cycloplegia, and examination of the anterior segment, media, and fundus. Myopia was defined as spherical equivalent refractive error of at least -0.50 D and hyperopia as +2.00 D or more. Children with reduced vision and a sample of those with normal vision underwent independent replicate examinations for quality assurance in four of the clusters. RESULTS: A total of 7008 children from 3426 households were enumerated, and 6447 (92.0%) examined. The prevalence of uncorrected, baseline (presenting), and best corrected visual acuity of 20/40 or worse in the better eye was 6.4%, 4.9%, and 0.81%, respectively. Refractive error was the cause in 81.7% of eyes with vision impairment, amblyopia in 4.4%, retinal disorders in 4.7%, other causes in 3.3%, and unexplained causes in the remaining 5.9%. There was an age-related shift in refractive error from hyperopia in young children (15.6% in 5-year-olds) toward myopia in older children (10.8% in 15-year-olds). Overall, hyperopia was present in 7.7% of children and myopia in 7.4%. Hyperopia was associated with female gender. Myopia was more common in children of fathers with higher levels of education. CONCLUSIONS: Reduced vision because of uncorrected refractive error is a major public health problem in urban school-aged children in India. Cost-effective strategies are needed to eliminate this easily treated cause of vision impairment.