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At least 19 recordsLinked to original sources
PubMed1990

Ultraviolet-absorbing spectacle lenses, contact lenses, and intraocular lenses.

Optical materials that are available to the practitioner for protection of the eye against hazardous exposure to ultraviolet radiation (UVR) are discussed. Principles of protection, procedures for calculating safe ocular exposure duration, and transmittance curves of commonly prescribed spectacle lenses, contact lenses, and intraocular lenses are discussed. Suggestions are made to assist the practitioner in providing adequate protection for the patient.

Animals↗
PubMedDate not supplied

Advanced manual lensometry: a self-learning guide for evaluating multifocal and specialty lenses, progressive lenses, prisms, and rigid contact lenses.

Advanced manual lensometry techniques are required when automated lensometry may not be appropriate for reading special lenses or rigid contact lenses. These advanced techniques are challenging but provide accurate diagnostic and lens verification data. One should never assume that the glasses the patient is wearing match what the doctor prescribed. The prescription should be checked at least once, even when there are no patient complaints. If possible, learn and practice these special procedures under the supervision of an optician or ophthalmic clinical trainer. This will help to verify that you are performing these special techniques correctly.

Contact Lenses↗
PubMed2001

Multifocal versus monofocal intraocular lenses after cataract extraction.

BACKGROUND: Good unaided distance visual acuity is now a realistic expectation following cataract surgery and intraocular lens implantation. Near vision however still requires additional refractive power, usually in the form of reading glasses. Multiple optic (multifocal) intraocular lenses are available that are claimed to allow good vision at a range of distances. It is unclear whether this benefit outweighs the optical compromises inherent in multifocal intraocular lenses. OBJECTIVES: The objective of this review is to assess the effects of multifocal intraocular lenses, including effects on visual acuity, subjective visual satisfaction, spectacle dependence, glare and contrast sensitivity, compared to standard monofocal lenses. SEARCH STRATEGY: We searched the Cochrane Controlled Trials Register - CENTRAL (which includes the Cochrane Eyes and Vision Group specialised register), MEDLINE and EMBASE. The reference lists of relevant articles were searched. Investigators of included studies and manufacturers of multifocal intraocular lenses were contacted for information about additional published and unpublished studies. SELECTION CRITERIA: All randomised controlled trials comparing a multifocal intraocular lens of any type with a monofocal intraocular lens as control were included. Both unilateral and bilateral implantation trials were included. DATA COLLECTION AND ANALYSIS: Data were collected and trial quality assessed. Where possible, statistical summary measures were calculated, otherwise data were tabulated. MAIN RESULTS: One ongoing and six completed trials were identified. There was significant variability between the trials in the outcomes reported. Unaided distance acuity was similar in multifocal and monofocal intraocular lenses (Peto odds ratio 1.27 (95% Confidence Interval (CI) 0.76 to 2.11)), with a small increase in the proportion of multifocal intraocular lens participants achieving less than 6/6 best corrected visual acuity (Peto odds ratio 1.64 (95% CI 1.10 to 2.42)). Unaided near vision tended to improve with the multifocal intraocular lenses. This resulted in decreased spectacle dependence with use of the multifocal intraocular lenses (Peto odds ratio 0.16 (95% CI 0.11 to 0.23)). Adverse effects included reduced contrast sensitivity and the subjective experience of haloes around lights. REVIEWER'S CONCLUSIONS: Multifocal intraocular lenses are effective at improving near vision relative to monofocal intraocular lenses. Whether that improvement outweighs the adverse effects of multifocal intraocular lenses will vary between patients, with motivation to achieve spectacle independence likely to be the deciding factor.

Cataract Extraction↗
PubMed1997

Topographical distribution of lactate dehydrogenase activity in human clear eye lenses and in lenses with different types of senile cataract: a histochemical investigation.

BACKGROUND: Homogenates of human clear lenses show an age-dependent reduction of enzyme activities. Topographical patterns of enzymes in clear and cataractous lenses can be visualized by histochemistry. MATERIAL AND METHODS: Human lenses were characterized by slit-lamp investigations as bearing different types of senile cataracts. Subsequently, lenses were removed by intracapsular extraction. Clear human lenses served as controls. Bovine lenses served to standardize freeze-cutting and incubation for lactate dehydrogenase histochemistry. RESULTS: Bovine lenses show a sharp demarcation between the enzyme reaction of cortical fibers bearing cell nuclei and the non-reacting deeper fibers not exhibiting cell nuclei. Clear human lenses, lenses with deep supranuclear cortical cataracts, and lenses with nuclear cataracts exhibit the same borderline. However, in lenses with a subcapsular cortical cataract only the epithelium and a very thin layer of the most superficially located fibers show positive enzyme reactions. CONCLUSION: In growing clear human and bovine lenses, independent of age, the more peripherally located cortical fibers bearing cell nuclei exhibit strong enzyme-histochemical reactions. More centrally located lens areas lacking cell nuclei increase in volume in an age-dependent manner. These lens regions do not exhibit enzyme activities detectable by our histochemical technique. Therefore the lens areas free of histochemical reaction product become larger with increasing age, whereas the peripherally located lens fibers apparently do not change their enzyme activities with age. Thus, homogenates of total lenses show age-dependent reductions of enzyme activities, although enzyme activities remain at a physiological level in cortical lens fibers with recognizable cell nuclei. In lenses with immature supranuclear cortical and (particularly) in lenses with black nuclear cataracts, cortical fibers still can exhibit high enzyme activities. Unexpectedly, also ruptured and broken fibers in immature deep supranuclear cortical cataracts show strong enzyme activities. In contrast, in lenses with (incipient) subcapsular cortical cataracts only the most superficially located lens fibers exhibit some enzyme activity.

Aged↗
PubMed1993

Microbial contamination of hydrophilic contact lenses: quantitation and identification of microorganisms associated with contact lenses while on the eye.

Previous studies have demonstrated the presence of microorganisms on hydrogel contact lenses under various usage conditions. We conducted this study to quantify and identify viable bacteria and fungi associated with hydrogel contact lenses while on the eye. We removed the lenses from patients' eyes using aseptic techniques and cultured them to identify loosely adherent, as well as lens bound, microorganisms. Lenses were vortexed in a transfer medium (thereafter called the lens extract) and the lenses were then incubated in an agar sandwich separately from the transfer medium. We cultured 108 lenses (82 daily wear and 26 extended wear) from 49 patients. Bacteria were cultured from 38% (41) of the lenses; for 31 of these 41 lenses bacteria were isolated only from the lens extracts (made by vortexing lenses in a transfer medium), suggesting a transient association with the lenses. No fungi were isolated. Counts of less than 10 colony forming units (CFU)/lens were observed on 89% of the lenses. Staphylococcus epidermidis were the most frequently isolated bacteria. A statistically significant relation was observed between increased CFU/lens and increased lens age for extended wear lenses (p = 0.028).

Adult↗
PubMed2002

[Hydrophobic AcrySof lenses or heparin-modified PMMA lenses in combined vitrectomy surgery -- results of a four-year study].

BACKGROUND: Combining pars plana vitrectomy with phacoemulsification and implantation of an intracapsular IOL provides many advantages and is performed as a routine operation. MATERIALS AND METHODS: Over a period of 3 years we compared foldable acrylic lenses AcrySof (Alcon) to heparin-modified PMMA lenses (Pharmacia) in a prospective study. The last implanted lenses had a follow-up period of at least 1 year. Out of 396 eyes from 329 patients we implanted 182 AcrySof lenses and 214 heparin-modified lenses. RESULTS: Both a smaller scleral tunnel incision and a lower rate of secondary cataract are advantages of foldable AcrySof lenses. Higher vulnerability of an AcrySof lens and a less stable lens-iris-diaphragm are of disadvantage. Heparin-modified PMMA lenses do not show these disadvantages, however, in consequence of using them you have to accept the wider scleral tunnel incision and a higher adhesion to cells. Furthermore, we found slightly more posterior synechiae with these lenses. CONCLUSIONS: In all, both types of intraocular lenses are suitable for combined surgery. We recommend using heparin-modified PMMA lenses in case of pre-existent instability of the lens-iris diaphragm or of patients' inability to maintain the prone position.

Acrylates↗
PubMed2002

Evaluation of optical changes of three types of lenses: hard PMMA, hydrogel, and heparin surface modified hard lenses effected by silicone oil, used clinically as a substitute of the vitreous body.

The objective of these investigations was an in vitro evaluation whether silicone oil OXANE of viscosity 5700 cSt clinically used in eye surgery as a substitute of the vitreous body, being in contact with an artificial polymer lens used as an implant of human lens, causes the changes in its optical properties. The paper presents the results of spectral analysis of transmission of visible (VIS) radiation of three types of artificial lenses: hard PMMA, hydrogel, heparin surface modified (HSM) hard PMMA, and the same lenses damaged by YAG laser radiation with an energy increasing from 1.7 mJ to 3.7 mJ, exposed to clinically applied silicone oil. The studies were carried out, in two-week intervals, over a period of 20 weeks. Hard PMMA and HSM lenses were found not to have changed their optical properties after 20 weeks of exposure to silicone oil. The measured transmittance values were within the range of instrumental error (+/- 1%). Optical properties of hydrogel lenses exposed to silicone oils deteriorated with exposure and after 20-week exposure to silicone oil the average transmittance value decreased by about 18%, reaching its final value of 67.08 +/- 2.37% (RSD = 5.56%). A minimal decrease of the initial transmittance values was observed only for the lenses exposed to laser radiation of highest energy (3.7 mJ). After completed exposure to silicone oil, two kinds of lenses were found to have a slightly improved transmittance: hard PMMA lenses by about 4% and HSM lenses by about 2%. On the other hand, in case of hydrogel lenses the deterioration of optical properties to the extent comparable to that of hydrogel lenses not damaged by laser radiation was observed.

Heparin↗
PubMed1995

Corneal epithelial permeability during extended wear of disposable contact lenses versus daily wear of soft contact lenses.

AIMS: The corneal epithelial permeability during extended wear of disposable contact lenses was compared with that during daily wear of soft contact lenses. The study was performed to verify whether the extended wear of disposable contact lenses would result in a higher permeability value than the daily wear of soft contact lenses. A higher permeability makes the cornea more vulnerable for bacterial infections and thus could explain the higher incidence of bacterial keratitis found in extended wear of disposable contact lenses in comparison with the daily wear of soft contact lenses. METHOD: The corneal epithelial permeability was determined by fluorophotometry in 33 healthy volunteers after the wear of soft, daily wear contact lenses for at least 6 months. Thereafter the determination was repeated in each volunteer after extended wear of disposable contact lenses for 1 month. The permeability in 34 healthy non-contact lens wearing volunteers was determined as a control. The permeability value was calculated from the amount of fluorescein that passed into the cornea after application by means of an eyebath. RESULTS: The mean permeability values after daily and extended wear were 0.032 nm/s and 0.031 nm/s, respectively. The values were not significantly different (Wilcoxon paired test p > 0.5). The mean permeability for the non-contact lens wearing controls was 0.042 nm/s. CONCLUSION: The results do not sustain the explanation that a difference in permeability value is the main cause of the increased incidence of keratitis during extended wear of disposable contact lenses in comparison with daily wear.

Adolescent↗
PubMed1986

Proteases and protease inhibitory activities in normal mammalian lenses and human cataractous lenses.

Trypsin inhibition (reduction in benzoyl arginine p-nitroanilide hydrolysis), elastase inhibition (reduction in succinyl trialanyl p-nitroanilide hydrolysis), and chymotrypsin inhibition (reduction in acetyl tyrosine ethyl ester hydrolysis) by neutral extracts of mammalian lenses were estimated. The activities were found to be markedly elevated in human cortical cataract lenses compared to normal adult lenses (antielastase 7.21 +/- 3.90 units (mean +/- SD) in cataract compared to 1.46 +/- 0.57 in normals; antitryptic, 0.54 +/- 0.38 and 0.12 +/- 0.04; antichymotryptic, 1.03 +/- 0.61 and 0.297 +/- 0.055). Antielastase activity was distinctly higher in adult normal human lenses compared to infant lenses (0.159 +/- 0.068). Elastase- and trypsin-like activities were detected at low levels in all mammalian lenses. Chymotrypsin-like activity could not be observed in the lenses. The cataractous lenses had lower trypsin- and elastase-like activities compared to normal human lenses (elastase 1.20 +/- 0.643 in normal compared to 0.062 +/- 0.035 in cataract; trypsin, 0.367 +/- 0.154 and 0.069 +/- 0.038). The role of protease: inhibitor complexes in the expression of the individual activities and their role in cataractogenesis are discussed.

Adult↗
PubMed1990

Are hard lenses superior to soft? The advantages of soft lenses.

Soft lenses now account for 85% of all lens sales in the United States and 74% of all sales worldwide. Several factors account for their popularity with patients, practitioners, and lens manufacturers. For patients, soft lenses offer easier adaptation, greater comfort, better appearance, less nighttime flare and spectacle blur, more flexibility in wearing schedule, and less chance of lens loss than polymethylmethacrylate (PMMA) or rigid gas-permeable lenses. Soft lenses also provide the options of disposability and of iris color change. Practitioners prefer soft lenses because they are less likely than hard lenses to cause epithelial staining, corneal molding, corneal edema, corneal desensitivity, or lens overwear syndrome. Furthermore, soft lenses present fewer fitting problems, satisfy therapeutic needs, are easier to stock for replacement purposes, and generally require no in-office modifications. Practitioners also welcome the benefits of disposable lenses: a simple lens care regimen, a decreased potential for deposit buildup, and adaptability to many different lifestyles. Manufacturers like the fact that hydrogels can be stock molded, and that their fitting is easier to teach.

Conjunctival Diseases↗
PubMed2001

Use of SoftPerm contact lenses when rigid gas permeable lenses fail.

PURPOSE: We evaluated the performance of the SoftPerm contact lens (Wesley Jessen) in patients with irregular astigmatism, usually due to keratoconus or after penetrating keratoplasty (PK), who were unable to befitwith, or intolerant of, rigid gas permeable (RGP) contact lenses. METHODS: A retrospective study of patients fit with SoftPerm lenses in the Cornea Department at Wills Eye Hospital between March 1985 and March 2000 was performed. RESULTS: Thirty-five cases were reviewed, with follow-up available in 33 cases. Most of the eyes had irregular astigmatism secondary to keratoconus (22/35,62.9%) or PK (10/35,28.6%) and had failed a trial of RGP lenses. The mean logMAR visual acuity with SoftPerm lenses was 0.13+/-0.18 (range -0.12 to 0.6). In 25 cases in which comparison with glasses or RGP lenses was possible, SoftPerm lenses provided better visual acuity than glasses in 17/25 cases (68%) with a mean difference of -0.24 (P = 0.001, paired t-test); visual acuity with SoftPerm lenses was better than RGP visual acuity in 13/25 cases (52%), with a mean difference of -0.06 (P = 0.07, paired t-test). Complications included broken lenses (16/33,48.5%), giant papillary conjunctivitis (GPC) (9/33, 27.3%), and peripheral corneal neovascularization (9/33, 27.3%). The GPC and peripheral corneal neovascularization were often delayed in presentation. The major subjective complaint was discomfort (13/33, 39.4%). At the last follow-up, the SoftPerm lens was still in use in 22/33 cases (66.7%). Discomfort was the most common reason for discontinuation. The mean duration of lens wear was 52.5+/-31.7 months, range 3 to 110 months. CONCLUSIONS: The SoftPerm lens can provide satisfactory visual correction in many cases of irregular astigmatism with RGP failure. However, problems such as frequent breakage, GPC, peripheral corneal neovascularization, and discomfort necessitate close follow-up.

Adolescent↗
PubMed1991

Corneal ulcers associated with contact lenses including experience with disposable lenses.

We conducted a retrospective study of corneal ulcers that had been managed on the Cornea Service at Wills Eye Hospital in 1988 and 1989. Forty-four percent (51 of 116) of the ulcers were associated with contact lens use. Pseudomonas was the most often isolated organism (25 of 116, 22%) and was most frequently associated with cosmetic soft contact lenses (16 of 25, 64%). Ulcers associated with disposable contact lenses (five cases) were similar to those associated with conventional extended wear myopic lenses (15 cases). Pseudomonas was the predominant organism with both disposable (four of five, 80%) and conventional extended wear lenses (nine of 15, 60%). Staphylococcus aureus (19 cases) and Staphylococcus epidermidis (19 cases) were the next most frequently isolated organisms and usually occurred in ulcers not associated with contact lenses (29 of 38, 76%). Ulcers were treated 3.3 times more often in people using extended wear than in those using daily wear myopic lenses. Disposable contact lenses have not eliminated the problem of corneal ulcers associated with extended wear contact lenses.

Bacteria↗
PubMed1987

Comparison of complement activation by silicone intraocular lenses and polymethylmethacrylate intraocular lenses with polypropylene loops.

Silicone intraocular lenses are undergoing clinical investigation for use in the United States. We compared the ability of silicone intraocular lenses to activate the complement system in human sera with that of polymethylmethacrylate intraocular lenses with polypropylene loops using a radioimmunoassay that measures levels of activated complement fragments. Sera incubated with polymethylmethacrylate lenses with polypropylene loops had higher levels of C3a and C5a, but not C4a, than control sera incubated without intraocular lenses. On the other hand, there were no differences in levels of C3a, C4a, and C5a between sera incubated with silicone lenses and control sera. These results suggest that polymethylmethacrylate lenses with polypropylene loops activate the alternative pathway of complement, while silicone lenses do not.

Complement Activation↗
PubMed1998

Vision with disposable toric contact lenses and daily-wear toric contact lenses.

The study compared the vision, the use and evaluation criteria in a group of students with corrective daily-wear toric contact lenses and disposable toric contact lenses, in order to ascertain which of the two optical systems is more advantageous. We fitted 114 subjects with daily-wear and disposable lenses to be worn for 12 months, one type of lens in one eye and the other type in the fellow eye. The results reveal no significant differences between the two systems in terms of visual acuity attained; both lenses centred well and were comfortable. Nevertheless, the deposits were significantly greater in the daily-wear lenses. The ocular reactions were less with the disposable toric lenses. In conclusion, the disposable lenses led to fewer deposits and less ocular reactions, but are limited in parameters. However, both optical systems were appropriate for correcting for astigmatism, and provided good visual acuity.

Adolescent↗
PubMed1995

Medical applications of scleral contact lenses: 2. Gas-permeable scleral contact lenses.

The indications and outcome of the wear of gas-permeable (GP) scleral contact lenses in 118 eyes of 85 patients attending a Scleral Contact Lens Clinic during a 5-year period from July 1988 to June 1993 were analysed. Ninety-nine eyes (83.9%) were originally fitted with PMMA lenses and were subsequently changed to GP lenses, whereas 19 (16.1%) were fitted with GP lenses from the outset. The mean duration of GP scleral lens wear was 15.3 months, with a range between 3 and 58 months. The indications for refitting the cases previously wearing PMMA scleral lenses with GP material were related to problems of chronic hypoxia. Thirty-three eyes (26.8%) had previous episodes of corneal oedema, and of the 27 that had a minimum of 3 months' follow-up, none experienced further episodes of oedema. Of the 32 eyes (26%) that had developed corneal vascularisation associated with PMMA scleral lens wear, two eyes were noted to have significant vessel regression after a period of GP wear, whereas in the remainder of cases, vessels remained static and nonprogressive. Thirty additional eyes (24.2%) experienced inadequate wear times associated with discomfort, and in these eyes the change to GP scleral lenses produced a statistically significant reduction in the inability to wear lenses beyond 4 h (p < 0.05).

Adolescent↗
PubMed1985

Alpha neoprotein molecules in normal lenses from animals of different ages and in cataractous lenses.

Alpha neoprotein molecules are formed by an association of A and B subunits resulting in a different quaternary structure than in alpha crystallin. The content of alpha neoprotein vs. alpha crystallin was estimated separately on the crystallin, cryoprotein and albuminoid fractions in lenses of animals of different species and ages, in lenses with experimentally induced cataracts and in human cataractous lenses. Alpha crystallin was determined on immunoadsorbents with bound antibodies restricted to quaternary determinants of this protein. Alpha neoprotein molecules were determined in the filtrate containing lens proteins not bound on the above immunoadsorbent. The filtrate was applied on an anti-A chain immunoadsorbent, and after desorption the A chain-containing molecules were applied on an anti-B chain immunoadsorbent. The amount of lens proteins bound to the latter immunoadsorbent gave a measure of molecules formed by an association of A with B chains other than in alpha crystallin, that is of alpha neoproteins. No alpha neoprotein was present in lenses from 2-week-old rats or in the 3- to 6-month-old calf lens cortex. The 2-year-old bovine lens nucleus did contain alpha neoproteins, but only in the albuminoid fraction. The lenses of adult rats (i.e. 3- to 4-month-old) contained alpha neoprotein molecules mainly in the albuminoid fraction; small amounts were also found in the cryoprotein fraction. All three fractions of lens proteins from 1-year-old rats contained alpha neoprotein molecules. No significant differences in the content of alpha neoprotein molecules were found in lenses with experimentally induced X-ray and galactose cataracts and in normal controls. This finding does not exclude possible structural differences between normal and cataractous alpha neoproteins. In human senile cataractous lenses, the content of alpha neoprotein molecules in all fractions analyzed equaled or exceeded the content of alpha crystallin present. The present findings demonstrate an age-dependent formation in the mammalian lens of alpha crystallin neoproteins lacking native quaternary determinants. The data obtained point to the possibility that the structural lability of alpha crystallin may be a contributing factor in cataractogenesis.

Aging↗