老视矫正的多样化研究进展

配戴框架凸透镜是矫正老视的主要方式，如单光眼镜、双光眼镜、渐变多焦镜及其他新兴衍射镜片。屈光性手术也为矫正老视提供了新的途径，可分为角膜屈光性手术、晶状体摘除联合可调节型人工晶状体（IOL）植人手术以及巩膜屈光性手术。角膜屈光性手术通过改变角膜的屈光力而改变眼球的屈光状态，包括激光角膜手术和角膜层间植人物手术两类。晶状体摘除联合人工晶状体植人术的关键在于可调节型人工晶状体的研发，现有的单焦调节型及多焦调节型人工晶状体优点是减少眩光或光晕，获得较好的夜间视觉，临床效果仍需进一步研究。巩膜屈光性手术通过增加晶状体赤道部与睫状肌的距离治疗老视，包括睫状体前巩膜切开术、激光老视逆转术和巩膜扩张术。老视矫正逐渐向多样化发展，为不同需求的老视者提供了更多的选择。     

飞秒激光晶状体老视手术的研究进展

由年龄增长所致的生理性眼调节下降引起、以视近困难为主要表现的屈光状态称为老视.老视的发生是多因性的,但晶状体年龄相关性硬化、弹性和变形能力下降以及调节力丧失是其主要致病机制.飞秒激光晶状体老视手术是近年来老视研究领域中出现的全新术式,其主要利用飞秒激光的光致分解作用按预设深度和形状在晶状体内进行微切开,从而制作出可滑动光爆破平面来治疗老视,整个手术过程在恢复自身晶状体弹性和变形能力的基础上,真正实现了眼的动态调节和连续聚焦功能,甚至逆转了年龄相关性的调节潜力丧失,为老视的治疗开辟了新的思路.在国外通过相关基础和临床试验,其矫治效果、有效性和安全性已得到初步验证,目前该技术尚处于研究阶段,仍面临很多问题,但它的出现革新了传统的老视治疗理念,相信其在老视手术中具有广阔的应用前景.本文就飞秒激光晶状体老视手术的理论依据、实验研究、效果评价及存在的问题等进行综述.     

激光老视逆转术初步临床疗效及其机理探讨

目的 观察激光老视逆转术（LAPR）的初步临床效果，并探讨其矫正老视的机制。方法 用PR-270激光老视治疗仪对四名老视患者行单眼激光老视逆转术（LAPR），观察手术前后的远近视力、调节幅度、屈光、眼压等改变，评价手术效果，探讨该手术矫正老视的机制。结果 术后术眼近视力及调节幅度明显提高，术后一年时调节幅度平均增加1．8D，短期对侧眼视力及调节幅度也有轻微的提高，但是3个月后很快回退。术后短期内远视力有轻度改变，术后半年基本恢复了原有的视力。早期术后屈光改变主要表现在散光和球镜的转化，但一年时基本恢复到初始状态。术后1周眼压轻度降低，一个月后基本恢复到术前的水平。术后没有发生明显的眼部并发症。结论 激光老视逆转术（LAPR）术式简单、安全性高、术后回退率低，是一种有效的老视矫正术。它矫正老视的机理主要是通过增加巩膜的弹性、扩大睫状环的空间来加强睫状肌的调节作用。     

人工晶状体矫正老视的临床应用

老视是一种随年龄增长出现的眼调节功能逐渐下降的生理现象。全球人口老龄化日益加剧, 目前有近1/4人口受到老视的影响。晶状体手术可以矫正老视, 包含有晶状体眼人工晶状体植入术和晶状体置换术。本文对各种矫正老视的人工晶状体, 如单焦点、多焦点、景深延长型、可调节等人工晶状体的临床应用及进展进行汇总分析, 以期为临床矫正老视提供参考。     

老视矫治手术治疗最新进展

老视是一种年龄相关的生理性老化现象.老视手术治疗已逐渐成为屈光手术最终需要面对的挑战.目前,其手术矫治包括眼外(施于角膜或巩膜)和眼内(晶状体置换或施于晶状体本身)两大策略,如角膜准分子激光手术、热传导成形术、飞秒激光基质内环形切开术、角膜植入物手术、各种多焦人工晶状体植入术、可调节人工晶状体植入术、晶状体软化术、巩膜扩张术等.各种手术方法均存在自身的优势和不足.本文就目前现有和近期即将问世的老视治疗方法及其被关注的问题作一综述.     

调节机制研究进展

有关调节的机制，早在19世纪Helmhohz就已提出了“松弛理论”，即调节时晶状体悬韧带处于松弛状态，晶状体依赖自身的弹性使前后极变凸；但该理论和实际观察到的许多调节时的晶状体改变不相符，故Tscherning在20世纪初又提出了“紧张理论”，认为调节时晶状体悬韧带至少一部分是处于紧张状态；20世纪90年代．Schachar从数学物理模型、组织解剖及临床等多方面论证了紧张理论，并将其作为治疗老视的一种依据。就有关调节机制的主要内容作一综述。     

老视的矫治研究现状

随着近视矫正技术的日趋成熟,老视逐渐成为屈光不正治疗下一个巨大的挑战.近年来,老视矫正呈现多样化发展,包括传统的配戴框架凸透镜、角膜接触镜,及近年来成为研究热点的屈光性手术,分为角膜途径、晶状体途径及以Schachar调节假说为基础的巩膜途径等.     

Monovision与老视矫正手术

Monovision(MV)矫正是一种成熟的矫正老视的方法,近10 a来,老视矫正手术逐渐开展,一些准分子激光角膜屈光手术(PRK、LASIK等)、激光角膜热成形术和传导式角膜成形术、人工晶状体植入术也采用MV矫正方法治疗老视,取得很好的效果,本文就MV矫正在这些老视矫正手术中的应用进行综述.     

老视矫治的研究进展

老视是一种与年龄相关、因调节能力下降而引起的渐进性视近困难,目前发生机制尚不明确,但矫正方法很多,包括配镜、角膜手术、巩膜手术、晶状体手术和药物治疗,也是屈光手术矫正近视、远视、散光取得良好效果后需要突破的重点;但各种方法均以增加屈光力为目的,并不能真正逆转老视的发生。就老视治疗的方法和集中关注的问题进行综述。     

传统验光和医学验光对人工晶状体眼老视验光的对比研究

目的:通过对比人工晶状体眼传统验光和医学验光的异同,探讨人工晶状体眼科学规范的老视验光方法。方法:双眼年龄相关性白内障超声乳化摘除及折叠型单焦点人工晶状体囊袋内植入的患者共30例60眼,术后3mo先后进行传统验光和医学验光,分别检测老视阅读近附加、调节幅度及在近矫正基础上测量的负相对调节(NRA)和正相对调节(PRA)、舒适阅读时间长度。结果:传统验光法所取得的近附加为1.50±0.42D,与年龄正相关(P<0.05),医学验光法所取得的近附加为1.28±0.19D,与年龄无相关性(P>0.05),且两者比较差异有统计学意义(P<0.05);医学验光法舒适阅读时间为30.13±5.10min,明显较传统验光法舒适阅读时间17.0±3.06min长(P<0.05)。结论:在进行人工晶状体眼老视验光时,医学验光可取得更有意义的屈光及调节参数,从而对验光处方进行更精确和个性化的调整,达到更舒适、持久用眼的老视验配目的。     

Presbyopietherapie mit Femtosekundenlaser

Presbyopia is by far the most common refractive error worldwide, with no permanent therapeutic option available. All efforts to restore accommodation by the use of surgery have not led to a generally accepted therapy. However, there is evidence from an animal model that the use of a femtosecond (fs) laser might influence the modulus of elasticity in the lens. Fs-laser impulses can create intralenticular disruption in animal eyes as well as human cadaver lenses and improve elasticity. The concept of treating presbyopia with fs-laser requires a new, complex theory combining the optical and the mechanical aspects of accommodation in the eye. Diagnostic tools for measuring optical change in power and geometrical modification as the eye views from far to near are needed to obtain objective clinical data. A non-invasive treatment of presbyopia to restore accommodation might be possible in the future.     

Comparison of the behavior of natural and refilled porcine lenses in a robotic lens stretcher

The mechanism by which the eye dynamically changes focal distance (accommodation), and the mechanism by which this ability is lost with age (presbyopia), are still contested. Due to inherent confounding factors in vivo, in vitro measurements have been undertaken using a robotic lens stretcher to examine these mechanisms as well as the efficacy of lens refilling - a proposed treatment for presbyopia. Dynamic forces, anterior and posterior curvatures, and lens thickness are all correlated for young natural and refilled porcine lenses. Comparisons are made to lenses refilled with a homogeneous polymer system. The amplitude of accommodation of the young porcine lens is very small such that it may be a suitable model for presbyopia. The behavior of refilled lenses was highly dependent on the refill volume. The volume could be tuned to maximize accommodative amplitude in the refilled lens.     

Pseudophakic accommodation with translation lenses – dual optic vs mono optic

PURPOSE: To investigate the pseudophakic accommodation effect in dual and mono optic translation accommodative intraocular lenses (AIOL) using linear matrix methods in the paraxial space. METHODS: Dual (anterior optic of power +32 D linked to a compensatory posterior optic of negative power) and mono lens power was determined in the non-accommodated state using linear geometric optics based on the Gullstrand model eye. The position of the AIOL was calculated from a regression formula. Pseudophakic accommodation was assessed with three systems: (1) forward shift of the mono optic lens, (2) anterior translation of the anterior optic in the dual optic lens system with an unchanged position of the posterior minus lens and (3) symmetrical anterior and posterior translation of the anterior and posterior lens. The Gullstrand model eye was modified by changing the axial length (and proportionally changing the phakic anterior chamber depth) to investigate the accommodative effect in myopic and hyperopic eyes. RESULTS: The dual optic lens system (2) yields a nearly constant accommodation amplitude of 2.4-2.5 D mm(-1) movement over the total range of axial lengths. The mono optic lens (1) provides a higher accommodative effect only in extremely short eyes (high refractive power of the lens), whereas for normal eyes (1.4-1.5 D mm(-1) movement) and for long (myopic) eyes the accommodative effect is much less than the dual optic lens. The dual optic lens system under condition (3) yields less accommodation amplitude compared with the dual optic system under condition (2) over the total range of axial length but provides higher accommodation amplitude compared with the mono optic lens system (1) with axial lengths greater than 22.3 mm (lens power 25.5 D). In the accommodated state, with lens translation of 1 mm, the absolute value of the lateral magnification increases with the refractive power of the mono optic lens (1) and decreases in both dual optic lens systems (under conditions 2 and 3). CONCLUSIONS: A mathematical strategy is presented for calculation of the accommodative effect of mono-optic and dual optic AIOL. The dual optic lens yielded a nearly constant accommodation amplitude of about 2.4-2.5 D mm(-1) translation, whereas the mono optic lens yielded an accommodative response of <2 D mm(-1) translation in long myopic or normal eyes. Only in extremely short eyes is the accommodative amplitude of the mono-optic lens higher than the dual optic lens.     

Deterioration of amplitude of the accommodation with age and its possible restoration in the intraocular lens implanted eye]

This study aimed to determine whether pseudophakia which have deteriorated amplitude of accommodation with age, i.e., presbyopia and which received implantation of refractively changeable intraocular lenses after cataract extraction are able to regain accommodative function. According surveys on aging in the literature, functional deterioration of the ciliary muscle and the zonular fiber is not so striking compared to the changes of crystalline lens material and capsule. Consequently the artificially pseudophakic eye can be expected to regain accommodative function when the crystalline lens material could be replaced by an appropriately visco-elastic material before 80 years of age when the crystalline lens capsule still retain its elasticity.     

Physiopathology in accommodation and presbyopia, clinical and surgical approach

Accommodation is a complex of phenomena by which the refracting power of the eye changes for focusing on near vision. Accommodative amplitude declines progressively with increasing age. Until today, this phenomenon called presbyopia was explained by Helmholtz's hypothezis which involves only ciliary muscle. It seems that in accommodation are involved, besides the ciliary muscle, the lens and extraventicular elastic components, biophysical dynamics of the lens capsule, vitreous, iris. According with the role of these factors and theirs pathophysiological implications, new surgical technique has developed to reverse presbyopia in the human eye (Surgical reversal presbyopia, Anterior ciliary sclerotomy) and offers a potential for understanding ocular hypertension and treatment of primary open-angle glaucoma.     

Crystalline lens accommodation and anterior chamber depth

Using paraxial equations, the change in dioptric power of the crystalline lens required to image objects at given distances from the eye, on the retina, is calculated. This shows that the depth of the anterior chamber affects crystalline lens accommodation more than other variables. The relationship between anterior chamber depth and presbyopia, and a possible geographical aspect, are discussed.     

Comparisons between pharmacologically and Edinger-Westphal-stimulated accommodation in rhesus monkeys

PURPOSE: Accommodation results in increased lens thickness and lens surface curvatures. Previous studies suggest that lens biometric accommodative changes are different with pharmacological and voluntary accommodation. In this study, refractive and biometric changes during Edinger-Westphal (EW) and pharmacologically stimulated accommodation in rhesus monkeys were compared. METHODS: Accommodation was stimulated by an indwelling permanent electrode in the EW nucleus of the midbrain in one eye each of four rhesus monkeys. Dynamic refractive changes were measured with infrared photorefraction, and lens biometric changes were measured with high-resolution, continuous A-scan ultrasonography for increasing stimulus current amplitudes, including supramaximal current amplitudes. Accommodation was then stimulated pharmacologically and biometry was measured continuously for 30 minutes. RESULTS: During EW-stimulated accommodation, lens surfaces move linearly with refraction, with an increase in lens thickness of 0.06 mm/D, an anterior movement of the anterior lens surface of 0.04 mm/D, and a posterior movement of the posterior lens surface of 0.02 mm/D. Peak velocity of accommodation (diopters per second) and lens thickness (in millimeters per second) increased with supramaximal stimulus currents, but without further increase in amplitude or total lens thickness. After carbachol stimulation, there was initially an anterior movement of the anterior lens surface and a posterior movement of the posterior lens surface; but by 30 minutes, there was an overall anterior shift of the lens. CONCLUSIONS: Ocular biometric changes differ with EW and pharmacological stimulation of accommodation. Pharmacological stimulation results in a greater increase in lens thickness, an overall forward movement of the lens and a greater change in dioptric power.     

Simultaneous measurements of refraction and A-scan biometry during accommodation in humans.

PURPOSE: Accommodation is a dioptric change in power of the crystalline lens resulting from ciliary muscle contraction that leads to an increase in lens surface curvatures and thickness and changes in the position of lens surfaces. Previous studies have used A-scan ultrasound to measure changes in the position of lens surfaces with voluntary accommodation, but have not simultaneously measured the change in refraction. The goal of this study is to simultaneously measure and correlate refractive and biometric changes in the lens during voluntary accommodation in humans. METHODS: Refraction was measured off-axis in the right eye and biometry on-axis in the left eye simultaneously during voluntary accommodation in 22 human subjects between the ages of 21 and 30 years (mean +/- standard deviation: 25.8 +/- 2.3 years). Subjects viewed a distant target and four near targets spanning the full accommodative range available to evaluate refraction and lens surface position at each accommodative state. RESULTS: Maximum objectively measured accommodative amplitude of all subjects was 5.64 +/- 0.21 D (mean +/- standard error of mean). Biometric and refractive changes during accommodation were linearly correlated. The mean +/- standard error of mean decrease in anterior chamber depth was 0.051 +/- 0.008 mm/D, increase in lens thickness was 0.067 +/- 0.008 mm/D, and increase in anterior segment length was 0.017 +/- 0.005 mm/D during accommodation. There was a net anterior movement of the lens center of 0.017 +/- 0.005 mm/D. CONCLUSION: Anterior chamber depth, lens thickness, and anterior segment length change linearly with refraction during accommodation. Per-diopter changes in the lens were greater in the current study compared with previous studies in which only accommodative demand was measured, which overestimates the accommodative response.     

飞秒激光在晶状体手术中应用的研究进展

飞秒激光主要用于角膜屈光手术,近年来随着全飞秒激光技术的问世,角膜屈光手术发生了巨大的变革和发展。飞秒激光的光致分解作用可使人体组织发生电离,可在组织内进行精确切削,而对切削区以外的组织影响较小,具有极高的安全性。飞秒激光在白内障手术中的应用包括透明角膜切口的操作、晶状体前囊膜的切开、晶状体核的碎核等,在晶状体屈光手术方面主要用于老视眼的矫治。就近年来飞秒激光技术在白内障手术和晶状体屈光手术中的应用进行综述。