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PubMed1997

Adhesion and growth of Serratia marcescens on artificial closed eye tears soaked hydrogel contact lenses.

The adhesion to hydrogel contact lenses and growth of Serratia marcescens on artificial tear fluid (ATF) soaked lenses was investigated. Results indicated that a corneal ulcer isolate adhered more avidly to lenses; ATF increased adhesion for all strains tested. The contact lens induced acute red eye (CLARE) isolate adhered poorly, however, it grew to a larger extent on ATF-coated lenses. The ability of the corneal ulcer isolate to adhere to lenses may be an important factor in its pathogenicity whereas the ability of the CLARE isolate to grow on the lens in the presence of antimicrobial tear proteins may be important in the development of inflammation.

Bacterial Adhesion↗
PubMed1975

Initial treatment of descemetocele with hydrophilic contact lenses.

A hydrophilic contact lens was used as the initial mode of therapy in 5 cases of descemetocele. The lens was left in place over the descemetocele continuously for periods ranging from 2 to 15 months. Corneal perforation did not occur, and the anterior chamber remained formed in all cases. The device seemingly provides sufficient structural reinforcement to Descemet's membrane to prevent its distension by the intraocular pressure. It also maintains Descemet's membrane in a moist state and protects the descemetocele from the trauma of the lid margins during blinking. This series of cases indicates that a hydrophilic contact lens can be a very effective temporizing measure for the treatment of descemetocele, enabling the surgeon initially to cope with an ocular emergency in a very simple manner, and to convert the ultimate surgical repair to a scheduled, carefully planned procedure with a much greater potential for success.

Adult↗
PubMed1987

Bilateral simultaneous Pseudomonas keratitis with myopic extended-wear contact lenses.

Bacterial keratitis is reported more frequently in the literature with the use of extended-wear contact lenses. This report describes a case of bilateral simultaneous pseudomonas keratitis in an elderly patient wearing extended-wear contact lenses for correction of myopia. The lenses were not properly disinfected prior to the development of the corneal ulcers. When bacterial keratitis is suspected with the use of extended-wear contact lenses, prompt diagnosis and treatment are necessary. Appropriate microbiologic testing of the contact lenses, lens cases, and lens solutions should also be undertaken.

Aged↗
PubMed1994

Lipid deposits on hydrophilic and rigid gas permeable contact lenses.

Never-worn hydrophilic contact lenses (from each of the four FDA-classified groups) and rigid gas permeable (RGP) lenses were individually incubated for 24 hours at 37 degrees C with constant stirring in a mixture of 992 microL of 0.9% saline and 8 microL of a 1:1 chloroform:methanol solution of lipids (20 mg each of cholesterol, free fatty acid, triglyceride, fatty acid methyl ester, and cholesteryl ester, representative of lipids commonly found in the tear film). The lipid material deposited onto each lens was then extracted and its components separated using high performance thin layer chromatography. The chromatograms were analyzed by densitometry. Results indicate significant lipid deposition onto all lens types, with the siloxanyl alkyl acrylate RGP-type lenses accumulating two to three times as much total lipid as any of the other lenses. This suggests that hydrophobic RGP lenses, which also have lipophilic character, are most prone to develop lipid deposits. Among the hydrophilic lenses, nonionic polymer matrices and higher water content tended to increase lipid deposition.

Chromatography, Thin Layer↗
PubMed1975

Variation of visual acuity with soft contact lenses: a function of luminance.

The relationship between visual acuity and luminance with soft contact lenses, compared with the same one obtained with glasses or the naked eye, shows that acuity decreases at the same rate as luminance is reduced. This result differs from what had previously been found in comparing acuity with hard contact lenses and glasses. In the present case, soft lenses conform to the aspherical curvature of the cornea, and therefore the eye wearing soft contact lenses is not affected by spherical aberration, as in the case of hard contact lenses. At the outset, soft lenses produce a somewhat lower visual acuity but with adaptation, acuity improves and becomes equal or better, as evinced by measurements made after three months of wear.

Adult↗
PubMed1997

A computer-interfaced vertometer system for contact lenses.

BACKGROUND: The conventional vertometer (lensometer) is difficult to use for accurate measurement of contact lenses whose back vertex power (BVP) varies across the optic zone. BVPs of multifocal rigid and soft contact lenses have previously been measured using a conventional vertometer incorporating the Scheiner principle, which makes use of two light paths equidistant from the center of the lens. METHODS: We have developed a computer-based vertometer system based on the Scheiner principle which can be used to produce a profile of BVPs across rigid and soft contact lenses. A computer interface to the vertometer allows rapid acquisition of readings and software-based ray tracing derives in-air dioptric power readings across the optic zone at specific ray heights. RESULTS: Results are presented for soft and rigid, and spherical and aspheric surface contact lenses. CONCLUSIONS: The system improves the measurement resolution of a standard vertometer and shows an acceptable level of precision and accuracy for most applications.

Contact Lenses↗
PubMed1975

The use of therapeutic soft contact lenses in corneal disease.

Soft contact lenses are being applied as a therapeutic device in various diseases and postoperative conditions of the cornea. Ten cases illustrate several of the clinical conditions in which lenses of approved types may be used, with adjunctive medication in some instances.

Adolescent↗
PubMed1988

Acanthamoeba-contaminated hydrogel contact lenses. Susceptibility to disinfection.

Acanthamoeba keratitis has frequently been associated with contact lens use. In this study, contaminated hydrogel contact lenses of patients were subjected to disinfection by thermal hydrogen peroxide and chemical (quaternary ammonium) systems. New hydrogel contact lenses contaminated by incubation on Acanthamoeba polyphaga plates were similarly subjected to the disinfection systems described above. Thermal disinfection was universally effective in eradicating acanthamoeba, whereas hydrogen peroxide and quaternary ammonium disinfection were ineffective. Scanning electron microscope photomicrographs suggest that acanthamoeba may adhere to surfaces of hydrogel contact lenses. These findings have significant implications for soft contact lens users.

Acanthamoeba↗
PubMedDate not supplied

Soft contact lenses for irregular astigmatism after laser in situ keratomileusis.

PURPOSE: To investigate soft contact lenses for managing irregular astigmatism after laser in situ keratomileusis (LASIK). The prevailing notion has been that soft contacts conform to corneal surface irregularities and have a limited role for managing LASIK-induced irregular astigmatism. METHODS: A 41-year-old man with bilateral central steep islands following LASIK had best spectacle-corrected visual acuity of 20/40(+1) in the right eye and 20/70+2 in the left eye, despite 20/20 acuity in each eye with rigid contact lenses. Three soft lenses made of etafilcon A (58% H2O) in different center thicknesses were placed sequentially on each eye. All lenses were -2.00 D sphere, in the flatter of the two available base curves. With each lens, corneal topography, spherical over-refraction, and the resulting visual acuity were recorded. RESULTS: In all instances, corneal topography showed reduced surface irregularity although at least some irregularity still transmitted through the lenses. Each spherical over-refraction gave better visual acuity than the corresponding best spectacle-corrected visual acuity. The right eye achieved 20/20 with the thickest lens and spherical over-refraction. The left eye achieved 20/25 with the lens of intermediate thickness and spherical overrefraction. The patient reported functional vision and good comfort with these lenses. CONCLUSIONS: Disposable soft contact lenses can modestly mask irregular astigmatism caused by excimer laser ablation.

Adult↗
PubMed1989

A unifying parameter to describe the clinical mechanics of hydrogel contact lenses.

We studied the relation of postlens squeeze pressure to the clinical fit of hydrogel contact lenses. This relation was statistically significant (p less than 0.01) for a variety of contact lenses currently prescribed over a range of thickness, water content, back central optic radius, diameter, and back vertex power. The squeeze pressure provided a useful parameter to describe and compare the clinical fit of hydrogel contact lenses and a model with which the fit of a lens to an eye could be predicted. There was virtually no movement of the contact lenses across the eye when the squeeze pressure was more than -14 mm H2O (-1370 dynes/cm2). However, the mechanics of the lens motion when the squeeze pressure was less than this critical pressure appeared to be related to a more complicated combination of the squeeze pressure and the other forces in the eye-lens system.

Contact Lenses, Hydrophilic↗
PubMed1998

The use of occluding tinted contact lenses.

PURPOSE: We explored the clinical issues surrounding the use of tinted contact lenses for vision occlusion in cases of debilitating vision disturbance, such as intractable diplopia. METHODS: We report the results with four patients fit with occluding tinted contact lenses. RESULTS: Vision occlusion by contact lenses provided a suitable comfortable occlusion method with improved cosmesis compared to occlusion by spectacles. Lens parameters and tint specifications were ordered for each patient. Correct lens care and handling were necessary to avoid contact lens related ocular inflammation. CONCLUSION: Provided that lens care is satisfactory and the patient does not have unreasonable expectations, a tinted contact lens can be a useful alternative to a covered spectacle lens or eye patch when occluding one eye, such as in cases of intractable diplopia, severe vision distortion, or intolerable photophobia.

Adult↗
PubMed1980

Blemishes developing on soft contact lenses.

Suspected contamination of soft contact lenses lead to biological, X-ray spectrophotometric, and photographic investigations to attempt identification of substances which could not be cleaned from the lenses and which increased in number with time. All indications point to suspect contaminant not being foreign material but a breakdown of the polymer structure.

Contact Lenses, Hydrophilic↗
PubMed1979

Clinical evaluation of FDA approved toric hydrophilic soft contact lenses (Part I).

Three toric hydrogel contact lenses have been approved by the FDA, Durasoft TT, Hydromarc, and Hydrocurve II. These all incorporate prism ballast as the major axis stabilizing feature, but differ in diameter and placement of the cylinder. Correct cylinder axis positioning and maintenance of meridional stability are essential to fitting success.

Astigmatism↗
PubMed2003

Simulated optical performance of custom wavefront soft contact lenses for keratoconus.

PURPOSE: Outstanding improvements in vision can theoretically be expected using contact lenses that correct monochromatic aberrations of the eye. Imperfections in such correction inherent to contact lenses are lens flexure, translation, rotation, and tear layer effects. The effects of pupil size and accommodation on ocular aberration may cause further difficulties. The purpose of this study was to evaluate whether nonaxisymmetric soft contact lenses could efficiently compensate for higher-order aberrations induced by keratoconus and to what extent rotation and translation of the lens would degrade this perfect correction. METHODS: Height topography data of nine moderate to severe keratoconus corneas were obtained using the Maastricht Shape Topographer. Three-dimensional ray tracing was applied to each elevation topography to calculate aberrations in the form of a phase error mapping. The effect of a nonaxisymmetric soft contact lens tailored to the corneal aberrations was simulated by adding an opposite phase error mapping that would theoretically compensate all corneal-induced optical aberrations of the keratoconus eyes. Translation (0.25, 0.5, 0.75, and 1.0 mm) and rotation (2.5 degrees, 5.0 degrees, 7.5 degrees, and 10 degrees ) mismatches were introduced. The modulation transfer function (MTF) of each eye with each displaced correction and with various pupil sizes (3, 5, and 7 mm) was deduced from the residual phase error mapping. A single performance criterion (mtfA) was calculated as the area under the MTF over a limited spatial frequency range (5 to 15 periods per degree). Finally, the ratio (RmtfA) of corrected mtfA over uncorrected mtfA provided an estimate of the global enhancement in contrast sensitivity with the customized lens. RESULTS: The contrast improvement ratios RmtfA with perfectly located lenses were for an average pupil size of 4.5 mm between 6.5 and 200. For small translation errors (0.25 mm), RmtfA ranged between 2 and 7. The largest lens translation tested (1 mm) often resulted in poorer performance than without correction (RmtfA <1). More than threefold improvements were achieved with any of the angular errors experimented. RmtfA values showed significant variations for pupil diameters between 3 and 7 mm. CONCLUSIONS: Three-dimensional aberration-customized soft contact lenses may drastically improve visual performance in patients with keratoconus. However, such lenses should be well positioned on the cornea. In particular, translation errors should not exceed 0.5 mm. Angular errors appeared to be less critical. It is further questioned whether the visual system is able to adapt to variations in optical performance of the correction in situ due to lens positioning and pupil size.

Contact Lenses, Hydrophilic↗
PubMed1999

Transmittance of tinted and UV-blocking disposable contact lenses.

PURPOSE: Tinted and ultraviolet (UV)-blocking disposable contact lenses have become increasingly popular over the last decade. Wearers of UV-blocking contact lenses could benefit greatly by protecting their eyes from potential UV radiation damage. A Uvikon 930 dual beam spectrophotometer was used to measure three enhancement-tinted lenses (royal blue, evergreen, and aqua), two types of UV-blocking lenses, and two types of non-UV-blocking lenses. Enhancement-tinted lenses did show a decrease in transmittance at certain wavelengths on the visible spectrum, but they did not reduce the transmittance of UV radiation to the extent of the UV-blocking lenses designed specifically for this purpose.

Contact Lenses, Hydrophilic↗
PubMed1991

[Effect of intraocular pressure measurement through therapeutic soft contact lenses by noncontact tonometer].

The measurement of intraocular pressure (IOP) was compared with and without soft contact lenses by a non-contact tonometer. The soft contact lenses examined were Plano-T and Plano-B4 therapeutic contact lenses and Breath-O refractive lens. Twenty-nine eyes of 18 patients with an IOP ranging from 9 to 48mmHg were studied. The measurements of IOP were 19.7 +/- 8.6mmHg with Plano-T and 18.9 +/- 9.2mmHg with Plano-B4. Both numbers were not statistically different, when compared with controls (19.3 +/- 9.8mmHg without lens). There was, however, a significant difference significant difference with (44.7 +/- 10.7mmHg) and without the Breath-O (p less than 0.01). The results suggest that accurate IOP measurements can be obtained through therapeutic soft contact lens by a non-contact tonometer.

Adolescent↗
PubMed2001

Overnight lens removal avoids changes in refraction and eye growth produced by plano soft contact lenses in infant marmosets.

Infant marmosets were fitted with zero-powered (plano) soft contact lenses from 4 to 8 weeks of age worn either continuously (24 h per day) (n = 4), for 12 h (n = 4), or for 8 h (n = 3) per day to determine whether limiting the daily duration of lens-wear could significantly reduce or eliminate the effects of continuous lens-wear on ocular growth and refractive state. As in macaques (Hung, L. F., & Smith, E. L. (1996). Extended-wear, soft, contact lenses produce hyperopia in young monkeys. Optometry and Vision Science, 73, 579-584), eyes fitted with contact lenses worn continuously developed more hyperopic refractions (mean +3.22 +/- 1.49 D SE) compared to their fellow untreated eyes, inconsistent changes in vitreous chamber depth (-0.02 +/- 0.09 mm SE) and flatter corneas (mean decrease in corneal power 4.22 +/- 0.39 D SE). Eyes wearing lenses for only 12 h per day showed similar but reduced effects compared to the 24-h group. Most importantly, ocular growth, corneal power and refraction were unaffected in the 8-h group. Future studies using contact lenses in infant primates should employ a reduced daily duration of lens-wear to eliminate the undesirable effect of contact lens-wear per se on ocular development.

Analysis of Variance↗