ISSN:1040-5488    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Increasing evidence of acute and chronic ocular effects of ultraviolet (UV) radiation has prompted some manufacturers to develop UV-absorbing rigid and soft contact lens materials. Currently, eight different lenses containing UV-absorbing agents are available in Canada. The spectral transmittance of a sample of these UV-absorbing contact lenses was measured in order to determine if all of them provide adequate protection from wavelengths in the UV spectrum. The sample consisted of 1 lens of each type: Cibasoft Ultrabloc; Permaflex UV; Boston RXD and Equalens; Alberta S; FluoroPerm 30, 60, and 92. A Philips single beam spectrophotometer was used. The lens under test was placed in a silica wet cell filled with unpreserved saline. Spectral transmittance was measured at 0.8-nm intervals over the waveband 200 to 800 nm. The results were recorded by a microcomputer interfaced to the spectrophotometer. The repeatability of spectral transmittance measurements of contact lenses using this method varied between 0% and ±1.55% of transmission depending on lens material and wavelength studied. The results showed that none of the rigid gas permeable (RGP) lenses, except the Alberta S, transmitted more than 0.1% (the sensitivity limit of the spectrophotometer) up to 380 nm. The Alberta S exhibited transmittance windows in the UV spectrum with peaks at 270 nm (23%) and 318 nm (29%). The Cibasoft Ultrabloc transmitted less than 1% up to 344 nm, whereas the Permaflex UV had a transmittance window in the waveband 240 to 316 nm with a maximum of 17% at 270 nm. The level of protection afforded by each lens was assessed by the computation of protection factor (PF) and safe exposure duration (SED). All lenses studied, including the five for which transmittance curves have not been published earlier, provide a better level of protection from normal environmental UV exposure than lenses without UV-absorber, although the Alberta S is the least effective among all the lenses studied. The clinical significance of these results will be discussed.

ISSN:1040-5488    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Purpose. To compare the test-retest variability (reliability) and the relations among clinical tests of texture and motion processing, visual acuity for highand low-contrast letters, and the Pelli-Robson contrast sensitivity test. Methods. In 20 normally sighted subjects, monocular visual acuity for letters of 96% and 11% contrast, Pelli-Robson contrast sensitivity, and motion-defined and texture-defined letter recognition thresholds were measured on each of two different days. Results. Test-retest correlation coefficients were 0.75, 0.91, 0.61, 0.90, and 0.84 and bivariate test-retest regression slopes were 1.0, 1.1, 0.8, 1.0, and 1.2 for high- and low-contrast acuity, contrast sensitivity, and motion and texture processing, respectively. The inter-test correlations with both test and retest significant were as follows: visual acuity for high-contrast letters vs. visual acuity for lowcontrast letters; and recognition threshold for texture- defined letters vs. acuity for letters of both high and low contrast. Conclusion. Test-retest variability for the tests of motion and texture processing were at least as low as for established clinical tests of high and low contrast acuity and contrast sensitivity. We conclude that these new tests offer a reliable means of obtaining clinical information which complements that provided by conventional tests with luminancedefined letters.

ISSN:1040-5488    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

TBUT and NITBUT (tear break-up time and noninvasive tear break-up time, respectively) were measured on four groups of subjects from different countries (two groups of Caucasians, two groups of Chinese). No significant difference was found in either TBUT or NITBUT values among the four groups of subjects. Gender of the subjects was not a factor affecting the TBUT or NITBUT values. The distributions of both NITBUT and TBUT were non- Gaussian and the median value of either parameter was lower than those previously reported. The NITBUT values were significantly higher than the TBUT values in both Caucasian and Chinese subjects. An investigation into the extent of agreement between the TBUT and NITBUT methods of assessing tear stability indicated that these methods do not agree sufficiently closely (that is, tear stability values measured with the NITBUT technique do not agree with those measured with the TBUT technique); short average tear break-up values are associated with small differences between the measures, whereas long average tear break-up values are associated with large differences between the measures.

ISSN:1040-5488    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Background. Acanthamoeba-assoc\ated keratitis occurs most often in contact lens wearers. The contact lens material may affect its ability to act as a mechanical vector, permitting transfer of viable amoebae from the storage case to the corneal surface. The purpose of this study was to investigate the effects of ionicity and water content on the comparative quantitative adherence of Acanthamoeba trophozoites and cysts to new, unworn hydrogel contact lenses and rigid gas-permeable contact lens materials. Methods. Sixteen quarter segments of each of 8 types of unworn hydrogel lenses representative of FDA groups 1 to 4 were exposed to freshly prepared cultures of either trophozoites or cysts of A. castellanii or A. polyphaga for 1.5 h, and then washed. Three types of rigid lens button were similarly exposed to A. castellanii trophozoites or cysts. Adherent trophozoites and cysts were then enumerated. Results. All hydrogel lenses showed binding of both trophozoites and cysts, with the former predominating in every case. It was primarily the ionic nature of a lens surface and secondly its water content that was associated with increased quantitative adherence of Acanthamoeba. Neither form of the amoebae bound to any of the hard lens buttons. Conclusions. Greater relative potential exists for contamination of ionic and highwater content hydrogels by Acanthamoeba. This combination may influence mechanical transmission of the protozoon to the corneal surface. Adherence to hard lenses (as buttons) did not occur if a postincubation wash step was performed.

ISSN:1040-5488    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

The Estradiol Transdermal Estrogen Replacement Patch System (Estraderm) is designed to provide continuous estrogen replacement therapy through a ratelimiting membrane applied to the skin. The relative advantage of the patch over the more commonly prescribed oral medication, Premarin, is that the drug is absorbed directly into the bloodstream without extended metabolism by the digestive system and the liver. Ocular side effects associated with Estraderm, reported in the literature, include fluctuation in corneal curvature and variations of keratitis sicca. Here, a case is presented in which a 50-year-old Caucasian female, without previous ocular sequelae status after hysterectomy and oophorectomy, experienced what appears to be atypical ocular symptoms associated with the Estraderm. To the best of our knowledge, this information has not been reported in the literature. Clinicians should be aware of the unusual symptoms that could accompany the use of the Estradiol Estrogen Replacement Patch and include them among the differential diagnoses. The condition, its associated symptoms, and summary of the literature are discussed.

ISSN:1040-5488    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Two studies have reported poor vision in opposite sex twins (evidenced by wearing glasses or low visual acuity, both of which are interpreted here as evidence of myopia), whereas none have reported an absence of such effects. If these reports are replicable, it would suggest a hormonal effect. There is one report of higher testosterone levels in those suffering from high myopia. A possible mechanism would be if sex hormones in opposite sex pairs transfer from one fetus to the other. There is evidence that sex hormones can cross the placenta, and reports of sex differences in the development of opposite sex twins are consistent with such transfers. If different parts of the eye respond differentially to sex hormones, eyes developing in the unusual hormonal environment of opposite sex twins would be expected to have high myopia rates.

ISSN:1040-5488    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:1995

数据来源: OVID