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PubMed1980

[Applanation tonometry on contact lenses with high water content. Problems, results, correction factors].

The use of contact lenses with high water content for different therapeutic purposes has become widespread in the past four years. Permanent-wear contact lenses of this type are used in the treatment of corneal conditions which resist therapy, and also postoperatively. They cause no problems in follow-up examinations with the slit lamp but make it very difficult to measure IOP, which is frequently necessary in such cases. Therefore, we carried out invetigations with the aim of calculating correction factors for applanation tonometry on contact lenses with high water content. It was found that the power of the contact lens has a highly significant effect on the reading obtained. Simple correction tables are given which enable a sufficient degree of accuracy to be achieved in tonometry on these contact lenses.

Contact Lenses, Hydrophilic↗
PubMed1991

Task and visual performance with concentric bifocal contact lenses.

We evaluated the effects of concentric simultaneous vision bifocal contact lenses on task performance, visual acuity, and stereopsis. Forty extensively screened presbyopes were fitted with CIBA Spectrum center-near bifocal contact lenses (BCL) and with distant contact lenses combined with reading spectacles (DCL) which served as the control. Thirty-two subjects completed the 8-week study. At dispensing and after 8 weeks of regular BCL wear, performance times with BCL were significantly greater than with DCL for all three near tasks. BCL generally resulted in more errors per trial. Visual acuities with BCL were reduced significantly by 0.8 to 1.4 acuity lines compared to DCL. Stereopsis was reduced significantly by 32 to 36 sec arc with BCL compared to DCL at both measurement sessions. It is likely that the decreased task performance with the simultaneous vision BCL is caused by the decreased visual acuity with these lenses. Nonetheless, 27 patients (58.7% of those selected to be fitted; 67.5% of those who were fitted) chose to wear the BCL on a regular basis at the study conclusion. Thus, even though BCL reduced task and visual performance, thoroughly screened and properly fitted presbyopic patients can become satisfied BCL wearers. However, the reduced task and visual performance with BCL should be considered when evaluating prospective BCL candidates.

Adult↗
PubMed2002

[Frequent replacement contact lenses--patient's evaluation].

PURPOSE: To measure the level of satisfaction connected with use of frequent replacement contact lenses. MATERIAL AND METHODS: Questionnaire forms were sent to 600 patients aged 7 to 54 years fitted with contact lenses between the years 1996 to 1999. Each questionnaire consisted of 31 questions about satisfaction, complications and every day care. RESULTS: 281 patients (46.8%) answered questionnaires, 94.7% of them were satisfied with the vision ensured by contact lenses. However 43% of contact lenses wearers used one pair of lenses at last 1 week longer then it was allowed. Only 38% of them followed control visit schedule. CONCLUSIONS: Our study demonstrated high level of satisfaction related to the use of frequent replacement contact lenses. However it was observed, that ophthalmologist indications were not completely fulfilled.

Adolescent↗
PubMed2001

Low-power microwave disinfection of soft contact lenses.

PURPOSE: To evaluate the effectiveness of low-power microwave irradiation on the disinfection of contaminated contact lenses. METHODS: We infected 24 soft contact lenses with Staphylococcus epidermidis, Staphylococcus aureus, and Pseudomonas aeruginosa. Each contact lens was placed into a vial containing 10 mL of contaminated, non-preserved saline. Each vial was then exposed to 2, 4, 6, 9, 12, 15, or 18 minutes of microwave irradiation in an oven (2,450 MHz 600W) set at 10% power. RESULTS: We found all contact lenses to be disinfected after 15 minutes of exposure. All lenses remained hydrated and revealed no apparent damage when examined under the slit-lamp biomicroscope. CONCLUSIONS: Low level microwaving in a home microwave oven can result in effective and non-damaging disinfection of soft contact lenses.

Contact Lenses, Hydrophilic↗
PubMed1988

Reflection of laser light from ophthalmic contact lenses.

Reflections of laser radiation from ophthalmological contact lenses are measured and hazard analysis calculations are presented. Measurements were made on the contact lenses using ophthalmic argon and krypton lasers. Reflection coefficients were around 0.2% for lenses with 'anti-laser' coatings and in the region of 4% for uncoated lenses. It can be shown that the nominal ocular hazard distance for a typical ophthalmic argon laser beam reflected from a contact lens with a flat front surface is approximately 30 cm for a coated lens and 1 m for an uncoated lens. The necessity of protective glasses for attending staff in particular circumstances is reviewed.

Contact Lenses↗
PubMed1996

[Use of contact lenses in children with severe myopia].

PURPOSE: To present own observation on the usefulness of soft contact lenses in treatment of high myopia in children and youth. MATERIAL AND METHODS: 43 children with high myopia were selected from 2320 patients fitted with lenses due to refraction errors. The whole complex of ophthalmological examinations including ultra sound scan of eyeballs and measurement of corneal sensitivity were performed prior to the lens fitting. Visual acuity and stereoscopy of glass and contact lenses were estimated. RESULTS: The contact lens fitting enabled to achieve significant visual acuity improvement in all patients. The improvement was observed in 53.4% patients in comparison with glass correction. Stereoscopy was achieved in 58.1% patients, with glass correction and 81.4% patients with contact lenses. CONCLUSIONS: Soft contact lenses are very useful in high myopia correction in growing-up patients. The basic and indispensable factor of successful contact lens fitting is a good cooperation with parents.

Adolescent↗
PubMed1997

Therapeutic contact lenses and eyedrops--is there a problem?

Numerous authors have investigated the interactions of contact lenses with their care solutions. Many reported hypersensitivity and toxicity reactions induced by the preservative in the care solution, especially with soft contact lenses. In medical contact lens practice the concurrent use of eyedrops in a patient wearing therapeutic contact lenses is a contentious issue. The usual practice is to prescribe unpreserved drops. In reviewing the literature, we found no evidence of complications using preserved eyedrops with such contact lenses in situ. The reluctance to prescribe preserved topical medication could stem from the evidence relating to contact lens care solutions.

Journal Article↗
PubMed1992

Vision and task performance with monovision and diffractive bifocal contact lenses.

We measured vision and task performance on 26 presbyopes, ages 46 to 65 years, fitted with diffractive bifocal contact lenses (BFCL) and monovision contact lenses (MVCL). Distance contact lenses combined with reading spectacles (DCL) served as the control condition. Twenty subjects completed the 6-week study. All subjects wore BFCL and MVCL daily for a period of 3 weeks each. Performance times for three near tasks were 6 to 8% longer with BFCL compared with DCL and 2 to 6% longer for MVCL compared with DCL. There were significant reductions in distance visual acuity with BFCL (0.4 to 1.5 Snellen lines) and MVCL (0.5 to 0.8 Snellen lines) compared to DCL. At the conclusion of the study, given a choice between BFCL and MVCL, 2 of the 20 subjects chose to continue wearing BFCL, whereas 18 of the 20 subjects chose MVCL. Our results show greater visual compromise and decreased task performance with BFCL and MVCL compared to DCL and greater patient preference for MVCL.

Aged↗
PubMed2003

Comparison of corneal endothelial bleb formation and disappearance processes between rigid gas-permeable and soft contact lenses in three classes of dk/l.

PURPOSE: To compare corneal endothelial bleb formation and disappearance processes between rigid gas-permeable (RGP) contact lenses and soft contact lenses (SCL) in the same class of oxygen transmissibility (Dk/L). METHODS: Experiments were conducted on 20 eyes of 10 nonwearers of contact lenses using six kinds of RGP lenses or soft lenses with hyper (A), high (B), and medium (C) classes of Dk/L. Each subject kept their eyes closed for 20 minutes after putting on each test lens. Starting just after eye opening, the subjects' eyes were examined for blebs every 5 minutes by specular microscopy, and percentage area of the blebs were calculated. For control, the same eyes were also examined without contact lens wear. RESULTS: The percentage area of the blebs just after eye opening was 1.2% for RGP-A, 1.7% for SCL-A, 5.1% for RGP-B, 4.7% for SCL-B, 6.9% for RGP-C, 8.6% for SCL-C, and 0.4% for the control. The difference from the control became insignificant in the bleb disappearance process just after eye opening for RGP-A and SCL-A, after 5 minutes for RGP-B and SCL-B, after 10 minutes for RGP-C, and after 30 minutes for SCL-C. CONCLUSIONS: Regarding bleb formation and disappearance, there was no difference in influence on the corneal endothelium between RGP lenses and soft lenses with similar Dk/L in the high and hyper classes. In the medium class, however, it was suggested that RGP lenses may have less of an impact on the corneal endothelium than soft lenses do.

Adult↗
PubMedDate not supplied

[Correction of keratoconus with soft contact lenses].

The authors present their experience in using soft contact lenses in 33 eyes with keratoconus (18 patients). Adaptation was possible only when the doctor-patient collaboration was good. Visual acuity (VA) of 0.4-1 was obtained in 85% cases versus 42.5% when glasses were used. In the period under observation no case of VA decrease was recorded. The subjects tolerated well the contact lenses. The specialty literature contains data indicating not only the optical role of the contact lenses but also their therapeutic, tectorial role.

Adaptation, Physiological↗
PubMed2006

Higher order aberrations induced by soft contact lenses in normal eyes with myopia.

PURPOSE: To evaluate and compare the wavefront characteristics of normal eyes with and without hydrogel soft contact lenses for correction of myopia. METHODS: Higher order aberrations (HOA) of 30 eyes of 15 soft contact lens users who had no ocular diseases other than myopia were quantified with a Nidek Marco three dimensional Wave wavefront analyzer. Zernike's polynomial was used to describe the wavefront measurements. Root mean square (RMS) values of the total HOAs, total coma, total trefoil and total spherical aberrations were obtained in the same eyes with and without soft contact lenses. We used paired sample t-test to analyze the data. RESULTS: Mean RMS values for all higher order aberration components with and without soft contact lenses were: total HOA 0.364 +/- 0.129 microm without lenses and 0.456 +/- 0.175 microm with lenses (P = 0.01), total coma 0.203 +/- 0.095 microm without lenses and 0.220 +/- 0.133 microm with lenses (P = 0.51), total trefoil 0.193 +/- 0.074 microm without lenses and 0.254 +/- 0.153 microm with lenses (P = 0.06), total spherical aberration 0.126 +/- 0.121 microm without lenses and 0.148 +/- 0.095 microm with lenses (P = 0.36). CONCLUSIONS: Wavefront analysis showed soft contact lenses for myopia induced a significant increase in total HOA. Though total coma, trefoil and spherical aberrations were also higher with contact lenses they were not statistically significant when individually evaluated and compared to values without contact lenses.

Astigmatism↗
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↗
PubMed2001

Compensatory changes in eye growth and refraction induced by daily wear of soft contact lenses in young marmosets.

Several studies have shown that growth of the primate eye responds in a compensatory direction to both positive and negative spectacle lenses--eyes grow more slowly and become hyperopic in response to positive lenses, and eyes grow more rapidly and become myopic in response to negative lenses. On the other hand, extended wear soft contact lenses, whether positively or negatively powered, induce hyperopia (Hung & Smith, 1996. Extended-wear, soft, contact lenses produce hyperopia in young monkeys. Optometry & Vision Science 73, 579-584.). We investigated whether responses in a compensatory direction occurred to soft contact lenses worn on a daily wear basis (8 h per day on an 8:16 h light:dark cycle). Ten infant marmosets (8-13 weeks of age) wore a soft contact lens, in one eye only, for 5-9 weeks. Lens powers used were zero (n = 2), +2 D (n = 1), +2 D followed after 5 weeks of lens wear by +4 D (n = 1) for 4 weeks, +4 D (n = 2), -2 D followed after 5 weeks of lens wear by -4 D (n = 2) for 4 weeks, -4 D (n = 2). At the end of the lens-wear period the positive lens-wearing eyes were more hyperopic relative to the fellow untreated eyes [mean +2.39 +/- 0.24 D (SE)] and the negative lens-wearing eyes were more myopic than the fellow untreated eyes [mean -2.48 +/- 0.91 D (SE)]. Fellow eyes were unaffected by lens wear [mean final refraction +0.45 +/- 0.09 D (SE)]. Plano lenses did not affect eye growth in either marmoset fitted with plano contact lenses.

Analysis of Variance↗
PubMed2003

Monochromatic wavefront aberrations in the human eye with contact lenses.

PURPOSE: The aim of this study was to investigate the effect of contact lenses on the optical performance of the eye by measuring wavefront aberrations for the eyes with or without contact lenses. METHOD: A sensitive aberrometer was used to measure wavefront aberrations for 54 eyes in 27 subjects for three conditions: with no contact lens (non-CL), with soft-contact lenses (soft-CL) and with rigid gas permeable contact lenses (RGP-CL). The root mean square (RMS) value of the wavefront aberrations and Zernike aberrations were calculated. RESULTS: A change in the RMS values of wavefront aberrations with CL wear was observed for every eye. The change in wavefront aberrations with CL wearing was found to vary substantially from individual to individual. Relative to the mean RMS value of the group for the non-CL condition, the mean RMS value was increased for the soft-CL condition and was significantly reduced for the RGP-CL condition. A significant increase in mean RMS for the soft-CL condition was found when astigmatisms were removed. Although soft-CL wearing resulted in significant increases in higher orders of Zernike aberrations (fourth, fifth, and higher), the RGP-CL condition led to a significant decrease in second-order Zernike aberrations. For the eyes with low wavefront aberrations in the non-CL condition, either soft-CL wearing or RGP-CL wearing results in increases in the RMS values. CONCLUSION: Contact lens wearing, either with soft lenses or the RGP lenses, causes changes in the wavefront aberrations of the eye. The changes in wavefront aberrations vary substantially from eye to eye. Although soft-CL wearing tends to induce more higher-order aberrations, RGP-CL effectively reduces the astigmatisms. Both soft-CL and RGP-CL induce more aberrations for the eyes that have low wavefront aberrations. The change in wavefront aberrations due to contact lens wearing may explain the changes in visual performance for contact lens wearers reported previously.

Adolescent↗
PubMed2002

The use of contact lenses by U.S. civilian pilots.

BACKGROUND: Since 1976, the use of contact lenses by civilian pilots has been permitted to correct distant vision for obtaining a Federal Aviation Administration (FAA) aeromedical certificate. This study examined the civil airman population's experience with contact lens use for a 30-year period (1967 to 1997). METHODS: Population totals for airmen who carried pathology codes 161 (contact lens) and 158 (orthokeratology) from January 1, 1967 through December 31, 1997 were used to calculate prevalence rates by class of medical certificate and age. The National Transportation Safety Board and FAA databases were queried to determine if contact lens use had contributed to aviation mishaps. RESULTS: The prevalence of contact lens use grew faster for first-class medical certificate holders and airmen > or = 40 years of age during the period. The frequency of airmen with orthokeratology increased by 23 times in a 10-year period. Reports from five aviation accidents and one incident suggested that contact lens use was a contributing factor in these mishaps. CONCLUSIONS: Professional pilots and older airmen were found to be more inclined to use contact lenses. The increasing use of contact lenses and the rapid changes in contact lens technology warrant continued monitoring to ensure aviation safety.

Adult↗
PubMed1980

Prevalence of conjunctival changes in wearers of hard contact lenses.

The prevalence of elevated papillae more than 0.3 mm in diameter was 10.5% in the conjunctivae of 200 subjects who had successfully worn polymethylmethacrylate hard contact lenses for eight hours or more daily for more than five years. Only three of 500 (0.6%) control subjects who had never worn contact lenses had these papillary changes. The prevalence of papillary changes for those with the so-called normal symptoms of mucus, itching, or both associated with wearing of hard contact lenses was 53% (16 of 21 subjects). The prevalence of these symptoms was 76% among subjects with polymethylmethacrylate contact lenses who had papillary changes and 8% among subjects with polymethylmethacrylate contact lenses who did not have papillary changes. We conclude that changes in the upper tarsal conjunctiva are associated with the wearing of hard contact lenses, occur in a significant percentage of patients wearing hard contact lenses for prolonged periods, and include a spectrum of papillary changes.

Conjunctival Diseases↗
PubMed2006

Prevention of bacterial colonization of contact lenses with covalently attached selenium and effects on the rabbit cornea.

PURPOSE: Although silicone hydrogel materials have produced many corneal health benefits to patients wearing contact lenses, bacteria that cause acute red eye or corneal ulcers are still a concern. A coating that inhibits bacterial colonization while not adversely affecting the cornea should improve the safety of contact lens wear. A covalent selenium (Se) coating on contact lenses was evaluated for safety using rabbits and prevention of bacterial colonization of the contact lenses in vitro. METHODS: Contact lenses coated with Se were worn on an extended-wear schedule for up to 2 months by 10 New Zealand White rabbits. Corneal health was evaluated with slit-lamp biomicroscopy, pachymetry, electron microscopy, and histology. Lenses worn by the rabbits were analyzed for protein and lipid deposits. In addition, the ability of Se to block bacterial colonization was tested in vitro by incubating lenses in a Pseudomonas aeruginosa broth followed by scanning electron microscopy of the contact lens surface. RESULTS: The covalent Se coating decreased bacterial colonization in vitro while not adversely affecting the corneal health of rabbits in vivo. The Se coating produced no noticeable negative effects as observed with slit-lamp biomicroscopy, pachymetry, electron microscopy, and histology. The Se coating did not affect protein or lipid deposition on the contact lenses. CONCLUSION: The data from this pilot study suggest that a Se coating on contact lenses might reduce acute red eye and bacterial ulceration because of an inhibition of bacterial colonization. In addition, our safety tests suggest that this positive effect can be produced without an adverse effect on corneal health.

Animals↗