硬性透气性角膜接触镜的形变与角膜形态的关系

目的 探讨硬性透气性角膜接触镜(RGPCL)在眼表面的形状稳定性及角膜形态对其的影响.方法 22名志愿者42只眼,用鹰式角膜地形图测量角膜像差后给予验配RGPCL,同样仪器测量RGPCL的像差后派发给志愿者,连续配戴1个月后回访,分别测量戴镜状态下以及摘镜30 min后的角膜地形图.采用配对t检验、W检验及相关分析对数据进行分析.结果 RGPCL戴到眼表面后,主要表现为离焦C4增加,右眼为离体(1.003 ±0.131) μm,在体(1.065 ±0.160) μm(P =0.015);左眼为离体(1.003±0.130) μm,在体1.069(0.851,1.594)μm,(P =0.017),水平/垂直散光C5变负,右眼为离体(0.072±0.083) μm,在体(-0.312 ±0.232)μm(P＜0.001);左眼为离体(0.066±0.056) μm,在体(-0.349±0.242)μm(P＜ 0.001),以及球差C12增加,右眼为离体(0.264±0.039)μm,在体(0.295±0.048) μm (P＜0.001);左眼为离体(0.266±0.035) μm,在体0.290(0.215,0.471) μm(P ＜0.001).角膜像差在戴镜前后发生改变的像差项有C4,C5,C7和C8等.在体RGPCL像差C4、C5、C12均与相应的戴镜前角膜像差呈正相关(右眼:r=0.557、0.596、0.581,P＜0.01,左眼:r=0.684、0.497、0.543,P＜0.01).结论 RGPCL戴在眼表面后,镜片前表面有一定程度的变平,球差增加,并且出现趋向于角膜的散光.RGPCL的配适不宜过于平坦.     

Guide to the clinical assessment of on-eye wettability of rigid gas permeable lenses

The number of rigid gas permeable (RGP) contact lens materials is increasing rapidly. One of the most critical issues for acceptance of new materials is lens wettability. This paper describes techniques for assessing lens wetting characteristics while the lenses are worn on the eye, and relates each observation to the lens material properties or patient tear characteristics. This method of lens wetting assessment is intended to aid the practitioner in determining the optimal lens material for a patient, based upon assessment of the interactions inherent in the lens-eye system.     

In vivo dehydration of disposable (Acuvue) contact lenses

The in vivo dehydration of the Acuvue disposable contact lens was measured in six subjects using a contact lens refractometer. On average, the lenses dehydrated 6.2 +/- 1.9% after 20 min and 10.2 +/- 3.9% after 6 h of wear. The magnitude of dehydration is greater than has been reported for other hydrogel lens types of similar water content. This information may assist practitioners in the interpretation of clinical signs pertaining to lens behavior and associated patient symptoms.     

The visby lenses.

PURPOSE: In this study, 10 lens-shaped rock crystals, manufactured not later than the early Middle Ages, have been examined with respect to their image-forming qualities. METHODS: The spherical aberration of the lenses served as a scale for comparison. Measurements have been taken with a specially designed light section method. Some of the examined lenses have a silver mounting and have been used as pendants, whereas others are unmounted and show no signs of use as jewelry. RESULTS: The two largest unmounted lenses have very interesting surface curvatures, rendering a very small spherical aberration of the lens. The combination of top and bottom surfaces of the lens causes an imaging quality comparable to the modern aspheric lenses used, e.g., in today's projectors. CONCLUSION: According to the results of this study, the knowledge and comprehension of optical design was much further developed in the Middle Ages than we assume today.     

The optics of occupational progressive lenses.

BACKGROUND: Occupational progressive lenses (OPLs) utilize progressive power optics and are designed primarily to meet near and intermediate viewing needs such as working at a computer workstation for presbyopic patients. OPLs are fabricated to have the prescribed near power in the lower part of the lens and the power in the upper portion of the lens is determined by the amount of power "degression" (decrease in plus power) relative to the near power. Independent measurements of the optical characteristics of these lenses have not been reported previously. METHODS: Manufacturers of 7 different OPL designs provided sample lenses for a patient with +2.50 D add that were measured with a Rotlex Class Plus lens analyzer (Rotlex Inc., Israel). Power measurements were normalized to the location specified by the manufacturer, and the vertical location of each lens was normalized to pupil center based on manufacturer fitting guidelines. RESULTS: Large optical differences exist among the OPL designs. The results show clear differences between the designs in terms of the add powers, their vertical location, and zone width. The size and location of the near, near-intermediate, far-intermediate, and far viewing zones were determined. CONCLUSIONS: The literature and clinical experience support that OPLs are successful at meeting the computer, general office, and other intermediate viewing distance needs of many patients. However, because of the large differences in the several OPL designs, patient success can likely be enhanced by selecting the design that best suits his or her viewing needs.     

Proton NMR relaxation in hydrogel contact lenses: correlation with in vivo lens dehydration data

A study of hydrogel contact lenses was undertaken to determine whether NMR relaxation data can be used as a predictor for on-eye lens dehydration. Proton NMR relaxation times (T1 and T2), were determined for a series of contact lenses for which on-eye dehydration data were also available. NMR relaxation times were found to depend upon lens water content, but the dependence was not monotonic. T1 values varied between 100 and 800 msec, and T2 values varied between 6 and 85 msec for the lenses studied. In this study, the NMR signal and corresponding relaxation times are average values, derived both from lens water protons as well as from exchangeable polymer protons. A simple analysis of the data indicates that the mobility of these protons varies by more than a factor of 10 for the lenses studied. A test for linear correlation between NMR relaxation rate, 1/T1 and relative change in lens water mass, % delta mw gave r = -0.830 for all data, and r = 0.904 if one lens was excluded.     

The IOL horizon: accommodative intraocular lenses.

BACKGROUND: For more than half a century, intraocular lenses have been used effectively to correct vision after cataract extraction. New developments in intraocular lens design have led to the creation of lenses that may have a significant role in the restoration of accommodation as well. PURPOSE: Accommodative lens technology is constantly evolving. Many different lens designs are currently under development. It is important for optometrists to be familiar with this technology and the various lenses being developed, as accommodative intraocular lenses stand to become the mainstay for cataract surgery, as well as for the surgical treatment of presbyopia. METHOD: The literature is reviewed in order to summarize the developments in accommodative lens technology.     

The disinfection of contact lenses contaminated with adenovirus.

PURPOSE: We compared the efficacy of different contact lens disinfection systems to eliminate adenovirus. METHODS: Laboratory study evaluating the elimination of adenoviral ocular isolates by contact lens disinfection systems. Hard (gas permeable) and soft contact lenses were contaminated with adenovirus serotypes 8 and 19, and then they were disinfected with chemical, hydrogen peroxide, and heat sterilization systems. The survival of the adenovirus was determined by the shell vial technique. RESULTS: Adenovirus survived chemical and hydrogen peroxide disinfection but not heat sterilization. CONCLUSION: Because heat sterilization is not readily available to sterilize adenovirus contaminated contact lenses, it may be prudent for patients with adenoviral keratoconjunctivitis to dispose of unclean contact lenses.     

The evolution of lenses

Structures which bend light and so form images are present in all the major phyla. Lenses with a graded refractive index, and hence reduced spherical aberration, evolved in the vertebrates, arthropods, annelid worms, and several times in the molluscs. Even cubozoan jellyfish have lens eyes. In some vertebrate eyes, multiple focal lengths allow some correction for chromatic aberration. In land vertebrates the cornea took over the main ray‐bending task, leaving accommodation as the main function of the lens. The spiders are the only other group to make use of a single cornea as the optical system in their main eyes, and some of these – the salticids – have evolved a remarkable system based on image scanning. Similar scanning arrangements are found in some crustaceans, sea‐snails and insect larvae.     

Phakic intraocular lenses.

Since Zaldivar's review of phakic intraocular lenses in these pages in 2000 [1**], further reports of experience with this technology have emerged. Their relative advantages and disadvantages over competing technologies are becoming clearer. Clinical trials, including Food & Drug Administration (FDA) trials, have shown predictability, stability, and efficacy. Safety of these implants over the long term remains a concern, but in some situations, at least, phakic intraocular lenses are becoming the refractive correction of choice. This brief review looks at the most recent data to emerge regarding phakic intraocular lenses.     

The predictability of retention and discontinuation of contact lenses.

BACKGROUND: The objective of this research was to investigate the possibility of predicting the retention or discontinuation of contact lenses on the basis of their effect on the quality of life of the wearer. While most studies of discontinuation of assistive technology devices have focused on other than psychosocial causes of discontinuation, there is reason to believe that a major cause is the psychosocial effect of the device on the user. METHODS: Participants were 418 adult volunteers who had been fitted with contact lenses. One hundred eighty of the participants had discontinued wearing their lenses, while 238 were still wearing their lenses. The participants were asked to complete a recently developed questionnaire, the Psychosocial Impact of Assistive Devices Scales (PIADS), which measures the psychosocial impact of assistive devices, and is used also to predict retention and discontinuation of other assistive devices. RESULTS: Overall correct prediction of the 418 respondents was 68.9%. The PIADS was better at predicting discontinuation than retention among males, while the reverse was true for females. CONCLUSIONS: The PIADS was shown to be a valid instrument to predict retention and discontinuation of contact lenses.