准分子激光屈光性角膜切削术后高透氧性角膜接触镜的应用

目的:探讨高透氧性角膜接触镜对准分子激光屈光性角膜切削术(photorefractive keratectomy,PRK)后眼刺激症状及角膜上皮愈合的影响。方法:共95例190眼PRK病例,术后随机选择一只眼戴软性亲水性高透氧的角膜接触镜,另一只眼配戴普通月抛型角膜接触镜。术后记录术眼自觉症状,观察角膜上皮愈合情况,检查术后6mo裸眼视力,同时进行haze评分。结果:高透氧角膜接触镜组术眼视物模糊、眼痛、畏光均轻于普通月抛型角膜接触镜组,两组比较差异有统计学意义(P<0.05)。高透氧角膜接触镜组平均角膜上皮愈合时间分别为3.11±2.12d,普通月抛型角膜接触镜组为4.02±2.21d,两组比较差异有统计学意义(P<0.05)。角膜上皮72h内愈合者高透氧角膜接触镜组占46%,普通月抛型角膜接触镜组占36%。术后第7d裸眼视力高于1.0者高透氧角膜接触镜组为60眼(63%),普通月抛型角膜接触镜组为48眼(51%)。术后6mo两组术后裸眼视力无显著性差异(P=0.35),两组haze发生率比较无显著性差异(P=0.55)。结论:PRK术后使用高透氧性角膜接触镜可以明显减轻术后患者的角膜刺激症状,减少患者的术后不适感,缩短角膜上皮的愈合时间。     

日本角膜接触镜的历史、现状和展望

日本的角膜接触镜历史可以追溯到1951年，美尼康公司的创始人，现任主席田中恭一先生成功地研制出日本第一枚角膜接触镜，那是一种不透氧的硬性角膜接触镜。1960年，配戴舒适、具有亲水性和更好透氧性的软镜在捷克斯洛伐克出现了。而美尼康公司则继续致力于研究硬性高透氧角膜接触镜(RGP)，他们开发出含水量为72％的非离子软性角膜接触镜材料，同时他们研制了可以连续30d配戴的RGP镜片：美尼康Z，并最先获得获得美国FDA认证。目前，在日本配戴角膜接触镜的人群大约有一千五百万，其中硬镜配戴者与软镜配戴者的比例为4：6。在日本RGP的高配戴率是因为日本的眼科医生让配戴者充分相信RGP镜片的安全保证。1990年日本开始生产抛弃型角膜接触镜。角膜接触镜的抛弃和频繁更换概念改变了人们对角膜接触镜传统的认识，很快就被大众所接受。但是，原本被人们认为是一种医疗器具的角膜接触镜变成了人们熟知的日用品。这导致了配戴者的依从性下降，超时配戴，甚至角膜缺氧的现象日益增加。于是，研究人员开始开发高透氧的硅水凝胶(SH)材料。在欧洲和美国，硅水凝胶材料的角膜接触镜已被批准可以连续配戴30d。现在角膜接触镜的新功能体现在双焦点角膜接触镜和角膜屈光治疗镜(CRT)上，它们分别可以用于矫正老视和提高裸眼视力。中国的角膜接触镜配戴人群在很短的时间内就迅速增长到一千万人。     

硅水凝胶镜片作为绷带型角膜接触镜的应用前景

角膜接触镜除了能够矫正屈光不正外,还能够作为绷带型角膜接触镜（绷带镜片）用于眼表疾病的治疗,大多数绷带镜片需要连续过夜配戴以实现良好的治疗效果,而传统的水凝胶镜片由于透氧性能的不足可能导致角膜缺氧,因此有高透氧性能的硅水凝胶镜片是更为理想的绷带镜片选择。了解硅水凝胶镜片作为绷带镜片在角膜病变、角膜屈光手术后以及作为药物载体的应用情况,将有助于制定绷带镜片治疗措施的个性化方案。     

大气颗粒物PM2.5附着于角膜接触镜及其对角膜接触镜透氧性及折射率的影响

目的 观察大气颗粒物PM2.5在角膜接触镜的附着情况及其对角膜接触镜透氧性和折射率的影响.方法 采集大气颗粒物PM2.5,配制浓度为l mg · mL-1的PM2.5混悬液,取硬性透气性角膜接触镜(rigid gas permeable contact lens,RGPCL)和软性角膜接触镜(soft contact lens,SCL)各18只,分为对照组、实验组和洗脱组,每组6只.实验组和洗脱组角膜接触镜浸入PM2.5混悬液中,室温振荡24 h.洗脱组经上述处理后转入无菌PBS中,室温振荡1h.对照组镜片浸入无菌PBS中,室温振荡24 h.利用场发射扫描电子显微镜下观察PM2.5在各组角膜接触镜表面的附着情况.检测各组角膜接触镜的透氧性和折射率,记录结果,并进行统计分析.结果 经过PM2.5混悬液浸泡后,实验组RGPCL表面发现存在较多PM2.5附着,呈散在分布.实验组RGPCL表面大气颗粒物计数为每100 μm2(3.19±1.64)个.对照组电镜扫描未发现大气颗粒物沉着.经洗脱后,洗脱组RGPCL表面仍可见大量大气颗粒物附着,每100μm2(5.12±1.27)个.洗脱组与实验组差异有统计学意义(P＜0.05).实验组SCL表面,大气颗粒物集中附着在SCL水凝胶孔隙边缘,而在孔隙中未见大气颗粒物附着,大气颗粒物细小,均匀;实验组SCL表面大气颗粒物计数为每100μm2(2.16±1.19)个.对照组SCL表面无大气颗粒物附着.经洗脱后,洗脱组SCL表面大气颗粒物计数为每100 μm2(0.56±0.39)个,洗脱组与实验组差异有统计学意义(P＜0.05).对实验组RGPCL和SCL表面大气颗粒物附着数进行比较,RGPCL表面大气颗粒物附着数较多,差异有统计学意义(P＜0.05).经过PM2.5混悬液浸泡后,实验组RG-PCL的透氧性(100.00±3.17)与对照组(100.00±2.36)比较差异无统计学意义(P＞0.05).实验组SCL透氧性(42.00±2.57)与对照组(41.00±3.44)比较差异亦无统计学意义(P＞0.05).经过PM25混悬液浸泡24 h后,实验组RGPCL的折射率(1.415 6±0.000 4)与对照组(1.415 3±0.000 4)比较差异无统计学意义(P＞0.05).实验组SCL折射率(1.373 7±0.000 7)与对照组(1.373 2±0.000 1)比较差异亦无统计学意义(P＞0.05).结论 与SCL相比,PM2.5更易附着在RGPCL表面,且不易洗脱.在本研究条件下,PM2.5虽然附着于角膜接触镜,但短时间内并未对角膜接触镜的透氧性及折射率产生影响.     

角膜塑形镜相关阿米巴性角膜炎一例

角膜塑形镜（orthokeratology,OK镜）,是一种高透氧的硬性角膜接触镜,镜片基弧较角膜中央曲率平坦,通过这种逆几何的镜片设计米机械性乐平角膜．达到暂时性矫正近视的目的［1］。     

角膜接触镜润滑液的实验研究

为保护角膜免受戴接触镜的损伤，研制了一种角膜接触镜润滑液。选用同济海昌生产的软性角膜接触镜进行实验。用润滑液浸泡接触镜，以人工泪液作为对照，扫描电镜和相位差显微镜观察，润滑液浸泡的镜片，其透氧孔清淅。动物戴镜试验，润滑液组戴镜８－７２小时后，对角膜进行１％荧光素染色，结果为阴性。     

角膜接触镜内表面附着物的超微结构观察

应用相位差显微镜和扫描电镜,对10例停戴后角膜接触镜,根据其厂家、类型、配戴时间长短不同分为四组。对角膜接触镜内表面附着物的种类、大小及角膜接触镜透氧孔数进行了仔细观察比较。对角膜接触镜引起角膜溃疡的机理、附着物颗粒的来源、保持角膜接触镜透氧孔的意义进行了讨论。     

角膜接触镜配戴时间与泪膜稳定性的相关分析

目的 观察分析配戴软性角膜接触镜的时间与泪膜破裂时间（BUT）的相关性。方法 随机对132例264眼就诊于我科有角膜接触镜配戴史的近视患者进行Lasik术前测定泪膜破裂时间（BUT）。结果 132例中，戴角膜接触镜1y以内者46例（92眼），其中8眼（8．7％）BUT≤5s，44眼（47．8％）BuT〉10s；戴角膜接触镜5y以上者42例（84眼），其中26眼（31．0％）BUT≤5s，20眼（23．8％）BUT〉10s。结论 配戴角膜接触镜时间较长（5y以上）的近视患者泪膜破裂时间（BUT）≤5秒者的比例（31．0％）明显高于戴角膜接触镜时间较短（1y内）的患者（8．7％），角膜接触镜配戴时间与泪膜稳定性呈负相关。     

氧气与角膜接触镜配戴

全球大约有八千万人 (约占总人口的 1.5 % )在配戴角膜接触镜 ,镜片的透氧性及配戴角膜接触镜后角膜的获氧状态是保证配戴安全性和有效性的关键。角膜需要多种营养物质以保证其正常的代谢功能 ,氧气是其中是重要的部分 ,只有在充分氧供的状态下 ,角膜才能保持稳定的 78%的水合状态 ,保证角膜透明性。为了进一步了解氧气与角膜接触镜配戴的关系 ,本文着重对角膜接触镜所致的角膜缺氧的主要表现及角膜接触镜的透氧性能及其表达指标作一综述。配戴角膜接触镜后 ,角膜的氧供明显减少 ,特别在闭眼状态下氧供减少尤其明显 ,角膜接触镜引起的角膜缺氧变化主要表现为 :①角膜上皮 :角膜上皮水肿 ,即因细胞间隙中水液充盈而发生的微囊样水肿 ,水肿明显时会影响视力并使角膜的敏感性下降 ;②角膜基质 :角膜基质水肿达 5 %以上即可从裂隙灯检查中发现 ,主要表现为条纹或皱褶 ,长期慢性水肿会诱发角膜新生血管的发生 ,逐步发生角膜疤痕、屈光改变等一系列问题 ;③角膜内皮 :慢性角膜缺氧最终会导致角膜内皮细胞形态的改变 ,而且无法代偿。保持角膜功能的最低需氧量称为“临界氧” ,理想的角膜接触镜应该是通过该镜片后到达角膜面的氧供超过临界氧。角膜接触镜的透氧性能表达指标主要有 :透氧性 (oxygenpermeability     

软性角膜接触镜的不良反应及并发症

随着软性角膜接触镜(SCL)广泛应用,所引起的眼部不良反应及并发症日益增多,引起眼科界及眼镜行业的高度重视。近年来的研究结果表明:(1)SCL导致角膜微环境改变,包括低氧状态,二氧化碳潴留,pH值下降,渗透压及温度变化。(2)SCL引起角膜功能及结构异常,包括上皮微囊形成,角膜敏感度下降及上皮变薄,基质水肿、变薄及新生血管形成,内皮细胞多相性改变及细胞数目减少。(3)SCL并发眼部炎症及感染,包括滤泡性结膜炎、急性球结膜充血、角膜浸润及感染。(4)今后研究方向是选择高透气的材料,制造与角膜表面相容的接触镜。本文对该领域研究进展作简要综述。     

Changes in myopia with low-Dk hydrogel and high-Dk silicone hydrogel extended wear.

PURPOSE: This study compared changes in myopia between wearers of high-oxygen permeability (Dk) silicone hydrogel lenses and low-Dk hydrogel lenses after 1 year of extended wear (EW). METHODS: Ninety-two adult subjects were randomly assigned to a lens type. Subjective refraction and autokeratometry were performed at baseline and at 6 and 12 months. RESULTS: After 6 months of EW, myopia (spherical equivalent) regressed by 0.18 +/- 0.33 D (p < 0.001) in the high-Dk silicone hydrogel group and progressed by -0.23 +/- 0.36 D (p < 0.001) in the low-Dk hydrogel group. There were no further changes after 12 months. Previous lens wear history, baseline refractive error, and age and gender did not have an impact on the change in myopia, and only 35% of the variation could be accounted for by changes in corneal curvature and lens type. CONCLUSION: Soft contact lens type significantly affects the direction of change in myopia during EW. We hypothesize that these changes are driven by pressure-related redistribution of corneal tissue in high-Dk silicone hydrogel lens wearers and by hypoxia-associated corneal thinning in low-Dk hydrogel wearers. More long-term studies are required to confirm whether the effects of high-Dk silicone hydrogel lens wear on myopia are permanent.     

Rethinking contact lens associated keratitis

This review presents a critical analysis of the literature relating to the use of binomial and polynomial classification schemes for categorising corneal infiltrative events (CIEs) associated with contact lens wear and the epidemiology of such events. The results of the Manchester Keratitis Study—a 12‐month, prospective, hospital‐based epidemiological study of contact lens wearers suffering from CIEs—are used as a tool to challenge and test traditional thinking in relation to contact lens associated keratitis. An innovative aspect of this study is the use of a novel clinical severity matrix to systematically score the severity of CIEs based on 10 key signs and symptoms. The ambiguities inherent in using binomial classification schemes (such as, microbial versus sterile, ulcerative versus non‐ulcerative et cetera) are highlighted. The failure of a polynomial scheme—due to extensive classification overlap between proposed sub‐types of CIEs—is demonstrated using a Venn diagram. A cartographic analysis reveals that infiltrates tend to occur in the superior cornea of patients wearing extended wear silicone hydrogel lenses, in the central cornea of patients wearing daily wear hydrogel daily disposable lenses and in the peripheral cornea of patients wearing daily wear hydrogel (excluding daily disposable) lenses. Infiltrates that occur more towards the limbus are less severe. The incidence of CIEs is higher when contact lenses are worn overnight. Logistic analysis reveals that the risk of developing a severe CIE is five times greater with conventional hydrogel extended wear versus silicone hydrogel extended wear. The male gender, smoking, a healthy eye and body, and the late Winter months are associated with an increased risk of developing CIEs. The rate of significant visual loss as a result of developing a CIE is low. Two key conclusions are drawn from this work, which represent a radical rethinking of this potentially sight‐threatening condition.

• 1 CIEs should be considered as a continuous spectrum of ocular disease.
• 2 If a contact lens wearer presents with a sore eye that is becoming progressively worse and a CIE is observed in that eye, lens wear should be suspended and anti‐microbial therapy initiated immediately.

     

A market survey of contact lens practice in Hong Kong

Purpose : The aim of this survey was to evaluate the use of contact lenses, current prescribing habits of practitioners and the development of the contact lens market in Hong Kong. Methods : Questionnaires were sent to all registered contact lens practitioners in Hong Kong. This questionnaire sought information about their choices on prescribing contact lenses and lens care products and their opinions on continuing education and future trends of contact lens development. Results : A total of 286 responses (22 per cent) were returned. On average, the respondents reported that 36 per cent of their patients were contact lens wearers and most were myopes. The ratio of new fittings to refittings was 1:3. Of the contact lens wearers, 66 per cent were fitted with planned replacement lenses, mostly daily disposable lenses. Multipurpose solution was the most popular lens care regimen prescribed. Only 48 per cent of astigmatic patients were fitted with toric lenses and the use of overnight orthokeratology and silicone hydrogel lenses was limited. Single vision contact lenses with over‐spectacles and monovision contact lenses were the most popular management for presbyopes. Dryness was the major problem reported by contact lens wearers. Practitioners look forward to further development of custom‐made toric, multifocal and silicone hydrogel lenses. The major source of new contact lens information was communication with contact lens suppliers. Conclusion : Compared to previous reports, there was no significant change in the prescribing habits of practitioners. The major complaint of contact lens wearers is still ocular dryness. The contact lens market is driven by younger contact lens wearers, and planned replacement soft contact lenses together with multipurpose solutions dominate. The use of bifocal/multifocal lenses remained low and practitioners want low cost bifocal/multifocal contact lenses with better visual performance and toric lenses with a wider range in parameters. The use of overnight wear lenses such as silicone hydrogel and ortho‐k lenses is limited and 30 days continuous wear silicone hydrogel lenses are prescribed mainly for daily wear.     

Adhesion of Pseudomonas aeruginosa and Staphylococcus epidermidis to silicone-hydrogel contact lenses.

PURPOSE: The purpose of this study is to compare the adhesion capabilities of the most important etiologic agents of microbial ocular infection to the recently available silicone-hydrogel lenses with those to a conventional hydrogel lens. METHODS: In vitro static adhesion assays of Pseudomonas aeruginosa 10,145, Staphylococcus epidermidis 9142 (biofilm-positive), and 12,228 (biofilm-negative) to two extended-wear silicone-hydrogel lenses (balafilcon A and lotrafilcon A), a daily wear silicone-hydrogel lens (galyfilcon A) and a conventional hydrogel (etafilcon A) were performed. To interpret the adhesion results, lens surface relative hydrophobicity was assessed by water contact angle measurements. RESULTS: P. aeruginosa and S. epidermidis 9142 exhibited greater adhesion capabilities to the extended wear silicone-hydrogel lenses than to the daily wear silicone- and conventional hydrogel lenses (p < 0.05). No statistical differences were found between the adhesion extent of these strains to galyfilcon A and etafilcon A. The biofilm negative strain of S. epidermidis adhered in larger extents to the silicone-hydrogel lenses than to the conventional hydrogel (p < 0.05), but in much lower amounts than the biofilm-positive strain. The water contact angle measurements revealed that the extended wear silicone-hydrogel lenses are hydrophobic, whereas the daily wear silicone- and conventional hydrogel lenses are hydrophilic. CONCLUSIONS: As a result of their hydrophobicity, the extended wear silicone-hydrogel lenses (lotrafilcon A and balafilcon A) may carry higher risk of microbial contamination than both the hydrophilic daily wear silicone-hydrogel lens, galyfilcon A and the conventional hydrogel lens, etafilcon A.     

Corneal hypoxia secondary to contact lenses: the effect of high-Dk lenses

Contact lenses made from materials of low-oxygen permeability (Dk) do not meet the oxygen requirements of the cornea for overnight wear. Long-term extended wear of these lenses results in chronic changes to all layers of the cornea, many of which are associated with hypoxia. High-Dk silicone hydrogel and gas permeable lenses are now available for 30-night continuous wear. The high-oxygen transmissibilities of these lenses have enabled the development of a successful continuous wear modality by eliminating the hypoxic effects of long-term wear. Presently, the focus is on improving lens performance by developing lenses that are more biocompatible, provide greater comfort, and maintain a stable tear film without inflammatory or mechanically induced adverse events.     

Disposable contact lens use as a risk factor for microbial keratitis

AIMS—A case-control study was performed to evaluate soft contact lens (SCL) wear modality as a risk factor for microbial keratitis.
METHODS—Contact lens wearers presenting as new patients to Moorfields Eye Hospital accident and emergency department during a 12 month period completed a self administered questionnaire detailing demographic data and contact lens use habits. Cases were patients with a clinical diagnosis of SCL related microbial keratitis. Controls were SCL users attending with disorders unrelated to contact lens wear. Odds ratios (estimates of relative risks) and 95% confidence limits (CL) were calculated through multivariable logistic regression analysis.
RESULTS—There were 89 cases and 566 controls. A substantially increased risk with 1-4 weekly disposable SCL compared with non-disposable SCL was identified among both daily wear (DW) (odds ratio =3.51, 95% CL 1.60-7.66, p=0.002) and extended wear (odds ratio 4.76, 95% CL 1.52-14.87, p=0.007) users after adjustment for demographic, lens use and hygiene variables. Other significant factors among DW users were "occasional" overnight use, use of chlorine based (as opposed to other chemical) systems in combination with poor storage case hygiene, and irregular disinfection.
CONCLUSION—Properties of some disposable SCL may be partly responsible for these excess risks. It is also possible, however, that this finding is largely a reflection of widespread complacency among patients and practitioners with respect to disposable SCL fitting and use.

Keywords: microbial keratitis; disposable contact lenses     

Disposable and frequent replacement contact lenses

Disposable and frequent replacement contact lenses dominate the marketplace. They are available in a wide variety of parameters for use in refractive errors, including myopia, hyperopia, astigmatism, and presbyopia. They are convenient and affordable and lend themselves to most wearing modalities, including daily wear, flexible wear, and extended wear for up to 30 days. In addition, they have been shown to be the most trouble-free contact lens wear modality for daily wear or extended wear. They are an appropriate choice for patients who desire occasional contact lens wear and have gained wide acceptance as therapeutic bandage contact lenses. Disposable and frequent replacement lenses will remain important modalities for some time to come as the variety of contact lenses and contact lens parameters that are offered continue to expand. New contact lens varieties, such as the high-Dk silicone hydrogel lenses, will further expand the role of these contact lenses in vision correction.     

Silicone hydrogel contact lenses and the ocular surface

For 30 years, contact lens research focused on the need for highly oxygen-permeable (Dk) soft lens materials. High Dk silicone hydrogel contact lenses, made available in 1999, met this need. The purpose of this review is to examine how silicone hydrogel lens wear affects the ocular surfaces and to highlight areas in which further research is needed to improve biocompatibility. Silicone hydrogel lenses have eliminated lens-induced hypoxia for the majority of wearers and have a less pronounced effect on corneal homeostasis compared to other lens types; however, mechanical interaction with ocular tissue and the effects on tear film structure and physiology are similar to that found with soft lens wear in general. Although the ocular health benefits of silicone hydrogel lenses have increased the length of time lenses can be worn overnight, the risk of infection is similar to that found with other soft lens types, and overnight wear remains a higher risk factor for infection than daily wear, regardless of lens material. Future contact lens research will focus on gaining a better understanding of the way in which contact lenses interact with the corneal surface, upper eyelid, and the tear film, and the lens-related factors contributing to infection and inflammatory responses.     

Morphology of corneal nerves in soft contact lens wear. A comparative study using confocal microscopy

The aim of this study was to evaluate corneal innervation in soft contact lens wearers using the Tomey Confoscan confocal microscope (40x/0.75 objective lens). Three distinct age- and sex-matched subject groups were involved, including extended soft (hydrogel and silicone-hydrogel) contact lens wearers, overnight soft (hydrogel) contact lens wearers, and non contact lens wearers. A number of variables were objectively measured, subjectively evaluated, or graded in order to investigate the distribution and morphology of corneal nerves. For most of the evaluated parameters, no statistically significant differences were found. However, qualitative observations showed noticeable differences in corneal nerve appearance among the different subject groups; the degree of corneal oedema was suggested as the main causative factor. In conclusion, neither the short-term (overnight wear) nor the long-term (12-month extended wear) soft contact lens wear appeared to affect the morphology and/or distribution of corneal nerves as viewed with confocal microscopy.     

Contact lens-related corneal infection in Australia

Microbial keratitis is a rare but potentially severe sight-threatening condition, associated with societal burden, cost and morbidity. Compared with microbial keratitis without lens wear, the disease in contact lens wear is more common, occurs at an earlier age, has lower morbidity and is more often caused by Pseudomonas aeruginosa and Acanthamoeba spp. Resistance to common antibiotics is infrequent in contact lens-related isolates and there is little evidence to suggest increasing bacterial resistance over time. There is some evidence for increased reporting of cases of Acanthamoeba keratitis internationally. The incidence of contact lens-related microbial keratitis has remained stable over time. Rates vary with wear modality, with the lowest risk of severe disease in daily disposable and rigid gas permeable contact lens wear; however, there are limited studies in daily wear silicone hydrogel and in contemporary daily disposable contact lenses. Risk factors for contact lens-related microbial keratitis can be either modifiable or non-modifiable and interventions to reduce the risk of, or severity of disease may be prioritised based on the attributable risk. Key risk factors based on high attributable risk include any overnight wear, failing to wash and dry hands prior to handling lenses and poor storage case hygiene practice. The strong link between microbial keratitis and storage case hygiene and replacement suggests the relevance of microbial contamination of the storage case. Both risk factors and evidence-based strategies for limiting storage case contamination are presented, including storage case cleaning protocols and antimicrobial storage cases; however, it is unclear if such interventions can ultimately limit the rate or severity of microbial keratitis in daily wear. Emerging challenges include understanding and limiting the risk of infection associated with decorative or cosmetic contact lens wear, particularly in Asia, and in understanding the safety of contact lens modalities for myopia control in a paediatric population