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PubMed1997

Use of contact lenses in patients with filtering blebs.

PURPOSE: The purpose of this study was to describe the outcome of patients with filtering blebs who were fit with contact lenses. METHODS: We retrospectively studied patients with filtering blebs secondary to glaucoma or cataract surgery who were fit with contact lenses. Eight eyes from seven patients were identified. RESULTS: Five patients (six eyes) were fit with gas permeable contact lenses and two patients (two eyes) were fit with soft contact lenses. Successful fits were achieved in all patients. No complications were observed after a mean follow-up of 64.6 +/- 28.5 months. CONCLUSIONS: No significant complications were recorded in our series of patients with filtering blebs who were fit with contact lenses. We think that when indications for fitting contact lenses are justified, patients with filtering blebs are acceptable candidates for contact lens use. However, adequate selection of cases, careful contact lens fitting, patient education, and close follow-up are necessary.

Aged↗
PubMed1991

Corneal edema after overnight lid closure of rabbits wearing silicone rubber contact lenses.

Elastofilcon A silcone rubber contact lenses induce less corneal swelling than no lens wear during sleep, and increasing the central thickness and volume of the lens does not influence its overnight performance. We sought to elucidate whether a silicone rubber lens can promote the distribution of atmospheric O2 on the cornea through a small interpalpebral opening under closed-eye conditions. Three groups of rabbit eyes comprised 12 eyes wearing Silflex (Dk 79.8 barrer) lenses, 12 with elastofilcon A (Dk 340 barrer) lenses, and 12 without lenses. All eyes were surgically closed overnight; six eyes in each group had a complete lid closure and six eyes had a partial tarsorrhaphy that left a small, central gap approximately 3 mm in length. When the lids were opened the next morning, the partially closed elastofilcon A eyes showed less corneal swelling (6.2 +/- 1.4%) than the partially closed no-lens eyes did (9.6 +/- 1.3%) (p less than 0.01), whereas the partially closed Silflex eyes were significantly more swollen (12.8 +/- 2.1%) (p = 0.01) than the other two partially closed groups were. The completely closed eyes showed no significant difference in corneal swelling among the groups. These results indicate that small lid gaps during sleep may lead to less corneal swelling when elastofilcon A lenses are used than with no lenses.

Animals↗
PubMed1978

Prolonged-wear contact lenses in aphakia.

While prolonged wear of contact lenses is possible for the aphakic patient, careful consideration must be given to patient selection and to the potential complications of such use. Currently available lenses are far from ideal and, if used at all, must be carefully monitored. The newer lenses, specifically designed for extended wear, more closely fit our needs. Several manufacturers are testing their devices under strict FDA supervision. FDA guidelines dictate a minimum of two years follow-up before a determination will be made as to which lenses are safe and effective enough for prolonged wear in aphakic eyes.

Adult↗
PubMed2000

Comparative study of the hydration of hydrophilic contact lenses by refractive index and gravimetry.

PURPOSE: To compare the percent hydration by wet weight of hydrogel contact lenses given by the manufacturers with the values obtained using the refractive index and the gravimetry methods. METHODS: We used a Valentine refractometer to determine the refractive index of new hydrogel contact lenses at equilibrium swelling in the original solution and container. From the refractive indexes we then obtained the percent hydration of the lenses using a previously prepared graph of refractive index vs percent hydration of saccharose in a phosphate buffer solution (pH 7.0). We used an electronic analytical balance of 0.01 mg resolution to obtain the weights of new lenses when dry and at equilibrium swelling dry, and calculated the percent hydration of the lenses from the difference of the wet and dry weights. RESULTS: The hydration values of the contact lenses obtained from the index of refraction differed more than those obtained by gravimetry from the values given by the manufacturers. Acuvue lenses were an exception-the difference for them was negligible. CONCLUSION: Gravimetry is more accurate, but more cumbersome and time-consuming than the index of refraction for the determination of the hydration of the hydrogel contact lenses. However, when a fast and easy method is required to obtain the approximate hydration of hydrogel contact lenses, the use of the refractive index method can give acceptable results for most applications.

Contact Lenses, Hydrophilic↗
PubMed1991

Microbial keratitis associated with plano tinted contact lenses.

The use of plano contact lenses for cosmetic purposes is a recent phenomenon. We report five cases of severe microbial keratitis associated with the use of these lenses. This subpopulation of patients who possess no refractive error are at risk of developing severe complications from contact lens wear. We have identified several issues which should be addressed by eye care professionals and regulatory agencies.

Acanthamoeba Keratitis↗
PubMed1989

Hydration of hydrogel contact lenses during hydrogen peroxide disinfection.

Some hydrogel contact lenses are susceptible to changes in hydration when soaked in hydrogen peroxide solutions of acidic pH. This study uses a hand refractometer to assess the water content of four Hydrocurve Elite hydrogel contact lenses during prolonged hydrogen peroxide disinfection. A 3-week period of soaking in peroxide solution lead to a decrease in contact lens water content from 50% to approximately 30%. Full rehydration of the lenses occurred over a period of 2 days, using one rinse and two changes of the recommended sodium thiosulfate neutralizing solution.

Contact Lenses, Hydrophilic↗
PubMed1992

A clinical evaluation of two multifocal soft contact lenses.

We fit two multifocal soft contact lenses, Bausch & Lomb's Bi-Tech and the Unilens contact lens from Unilens Corporation, in two separate populations of presbyopes. Most patients (24/42, 57%) had no prior contact lens experience. Patients were evaluated at 6 and 12 months for comfort, visual acuity, lens fit, and corneal findings. Both distance and near vision were found to be slightly decreased with each contact lens when compared to best corrected visual acuity with spectacles. Seventy-seven percent (14/18) of the Unilens wearers and 67% (16/24) of the Bi-Tech wearers continued to wear their lenses for at least 1 year. Those who discontinued lens wear did so because they were dissatisfied with their vision. Presbyopes who seek correction with soft contact lenses appear to be more tolerant of a decrease in distance vision than a decrease in near vision. Both lenses were comfortable and no corneal pathology was induced. Our results suggest that the Unilens (simultaneous vision design) provides more predictable correction of presbyopic symptoms than the Bi-Tech (alternating vision design) because it is independent of lower lid position and translation. Both of these lenses are viable options for the correction of presbyopic symptoms.

Contact Lenses, Hydrophilic↗
PubMed1996

Effect of patient wear and extent of protein deposition on adsorption of Acanthamoeba to five types of hydrogel contact lenses.

Attachment of Acanthamoeba species to hydrogel contact lenses is a possible route of infection in Acanthamoeba keratitis. In this study, Acanthamoeba adsorption was compared with extent of lens deposition in worn lenses of different hydrogel polymers. After wear, lenses (80 lenses of 5 different types) were analyzed for total protein, surface area of deposition, and Acanthamoeba castellani trophozoite and cyst adsorption. Adsorption of Acanthamoeba trophozoites to worn lenses was greater than adsorption to unworn lenses for four of the five lens polymers (p < 0.01). Adsorption of cysts was greater for one of the five lens polymers (p < 0.001); all other adsorption assays showed no change with wear (p > 0.05). Adsorption was affected by both the water content and ionicity of the lens polymer. These results show that adsorption of Acanthamoeba to worn hydrogel contact lenses is greater than or equal to adsorption to unworn lenses.

Acanthamoeba↗
PubMed1987

Carbohydrate deposits on the surfaces of worn extended-wear soft contact lenses.

Three different commercial extended-wear soft contact lenses worn continuously by patients for at least 28 days were stained with fluorescein isothiocyanate-labeled lectins. These lectins detected the presence of alpha-linked or beta-linked D-mannose, D-glucose, D-galactose, L-fucose, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, and N-acetyl neuraminic acid (sialic acid) on the surfaces of the contact lenses. These saccharides are bound to other sugars that likely account for an integral part of glycoprotein and/or glycolipid deposits on lens surfaces. These tear deposits may contribute to the chemical spoilage of the lens and, furthermore, may serve as specific receptors for pathogenic microorganisms commonly implicated in extended-wear soft contact lens-associated infectious keratitis.

Contact Lenses, Extended-Wear↗
PubMed2005

Therapeutic applications of lotrafilcon a silicone hydrogel soft contact lenses.

PURPOSE: To investigate the effectiveness of silicone hydrogel soft contact lenses for therapeutic applications. METHODS: The study included 37 patients who had bullous keratopathy (n=12), recurrent corneal erosion (n=9), filamentous keratitis (n=3), corneal melting after corneal surgery (n=4), lamellar lacerations (n=4), or chemical trauma (n=5) and were fitted with silicone hydrogel soft contact lenses between May 2000 and August 2003 in First Eye Clinic of Kartal Training and Research Hospital. Changes in corneal signs by slitlamp evaluation, judgment of pain relief, additional complications, and success of therapeutic lens treatment were reported. Appropriate medical therapy was given as required. RESULTS: A total of 83.78% of the patients had complete healing, and 8.1% of the patients showed at least partial improvement. Visual acuity improved in 56% of patients, and pain relief was achieved in 91.16% of the patients. No additional complications were reported in relation to the lenses. CONCLUSIONS: The use of high-Dk lotrafilcon A soft contact lenses for therapeutic purposes is safe, effective, and practical.

Contact Lenses, Extended-Wear↗
PubMed2005

Over-the-counter decorative contact lenses: Cosmetic or Medical Devices? A Case Series.

PURPOSE: To illustrate the implications of the unauthorized sale and unmonitored wearing of decorative cosmetic contact lenses resulting in ocular complications and to determine the prevalence of the use of cosmetic contact lenses obtained from unlicensed providers by adolescents. METHODS: Observational case report, structured interview, and survey in a retrospective, observational, clinical practice setting. Reported sources of contact lenses were categorized as provider and nonprovider, and associations within the data were reviewed by using a Pearson correlation and chi-square test. RESULTS: Twelve patients (eight female and four male) were seen urgently for acute eye pain and redness after wearing plano decorative contact lenses. None of the patients had previously worn a contact lens. None of the lenses were dispensed by eye care professionals. Four patients developed blinding infections requiring hospital admission. Causative organisms included staphylococci, Pseudomonas, and acanthamoeba. One patient required a penetrating keratoplasty. One hundred fifty-nine patients were surveyed. Thirty-seven (23%) used decorative contact lenses. Lenses were obtained from an unlicensed provider 51% of the time. Education about lens care and handling was significantly associated with acquiring lenses from licensed providers (R = 0.74, P < 0.0001). CONCLUSIONS: Colored noncorrective contact lenses are being dispensed without a prescription or fitting from unlicensed vendors. Patients who acquire lenses from unauthorized providers are significantly less likely to be instructed on appropriate lens use and care. Consequently, uninformed lens wearers are experiencing acute vision-threatening infections and inflammation.

Adolescent↗
PubMed1978

Low atmospheric pressure effects on wearing soft contact lenses.

The majority of all research in the field of contact lenses has taken place in a normal, ground-level environment. The purpose of this study was to determine if any changes occurred in wearing hydrophilic soft lenses under conditions of low atmospheric pressures. The effects on visual acuity, refraction, keratometry, and biomicroscopy were investigated with eight naval volunteers while wearing soft contact lenses at simulated altitudes up to 30,000 ft (9144 m) in an aviation hypobaric chamber. The results indicated that the low atmospheric pressure at high atitude in itself did not affect the fit of soft contact lenses.

Aerospace Medicine↗
PubMed2006

Ocular motor triad with single vision contact lenses compared to spectacle lenses.

AIM: Theoretically myopes are required to exert more accommodation and vergence when wearing single vision contact lenses compared to glasses and hypermetropes less. This study aims to quantify the effects clinically. METHOD: Thirty subjects (21 female, nine male, average age 21.0+/-2.2 years) with a range of refractive errors (-7.87 D to +3.50 D) viewed in a random order, static targets at 0.1, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 D accommodative demand that were matched for angular subtense. The subjects were fully corrected with spectacles and daily disposable contact lenses to their full prescription. Accommodation was monitored objectively with the PowerRefractor and Shin-Nippon SRW5000 and vergence and pupil size with the PowerRefractor. RESULTS: Myopes exerted greater accommodative effort for viewing near targets with contact lenses than glasses and hypermetropes less (r(2)=0.35, p=0.001 PowerRefractor). Myopes also exerted greater vergence effort for viewing near targets with contact lenses than glasses and hypermetropes less (r(2)=0.22, p<0.01). CONCLUSION: Theoretical calculation of the accommodative and vergence requirements with glasses compared to contact lenses reflect clinical findings, although there is reasonable variability between individuals.

Accommodation, Ocular↗
PubMed1997

Acanthamoeba keratitis associated with contact lenses; report of three cases in Italy.

Three female patients, aged from 17 to 44 years, developed Acanthamoeba keratitis associated with the use of soft contact lenses and cosmetic contact lens. Two of these patients were myopic and wore soft contact lenses for optical purpose, while the third patient used a cosmetic lens. In this paper we describe the related risk factors, the success of cultural procedures and the outcome of medical management. In 2 out of the 3 cases we obtained cultures positive for Acanthamoeba, from the contact lenses and the contact-lens case. The isolated strains belong to the group II according to Pussard and Pons and they were proven pathogen for experimentally infected mice. All infections were treated successfully; however in 2 out of the 3 patients the visual acuity was reduced to the light perception.

Acanthamoeba↗
PubMed2001

[Quantitative analysis of tear protein profile for soft contact lenses--a clinical study].

PURPOSE: Approximately 3% of the patients with refractive errors wear contact lenses. Recent studies revealed contradictory results regarding the changes of the tear film in contact lens wearers. The aim of this study was to analyze the influence of wearing contact lenses on the tear protein patterns. The study was performed using a new method to analyze quantitatively the tear proteins based on digital image analysis of electrophoretical separations followed by multivariate statistical calculations. METHODS: Two groups were examined: 121 healthy volunteers (KO) and 66 wearers of soft contact lenses (KL). The tear proteins were separated by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). For each electrophoretic lane, a densitograph was built by digital image analysis. Subsequently a multivariate analysis of discriminance was performed. RESULTS: The concentration of the tear proteins lactoferrin, sIgA, lysozyme and albumin was slightly reduced. In contrast, the concentration of lipocalin was increased in the tears of contact lens wearers (p < 0.07). However, including all peaks found in each electrophoretic lane, the analysis of discriminance found a statistical significant difference between KO and KL (Wilks' Lambda = 0.88; p < 0.0001). CONCLUSIONS: Wearing contact lenses leads to significant changes in the composition of tear-film proteins. However, the pathomechanism of this alteration of the tear film is still unclear. Because of the large number of contact lens wearers, these alterations should be examined further.

Albumins↗
PubMed1988

Evaluation of contact lenses by microbial enumeration and protein determination.

Contact lenses worn for varying periods of time (from 1 to 48 months) were subjected to microbiological examination by plate counts and protein determination. Seventy percent of the lenses displayed bacterial colony counts below 120 colony-forming units (CFU)/lens, 28 percent were in the range of 140 to 9060 CFU/lens, and one lens was contaminated with greater than 6 x 10(4) CFU/lens. Fungal contaminants were detected in three lens specimens in the range of 220 to 760 CFU/lens. Protein accumulation showed wide variation of up to 1.2 mg of protein per lens. Statistical analysis indicated highly significant associations (p less than 0.001) between the bacterial colony counts obtained with three different media. Some significant associations were found between the protein concentration and bacterial counts. The data did not indicate statistically significant relations between the above variables and either the water content or the length of wear of the contact lenses.

Adolescent↗
PubMed1995

Quantitative comparison of Acanthamoeba castellanii adherence to rigid versus soft contact lenses.

We evaluated quantitative differences in adherence of Acanthamoeba castellanii trophozoites and cysts to new unworn contact lenses as a function of contact lens type and duration of exposure. Daily wear soft (polymacon), disposable soft (etafilcon A), rigid gas permeable (RGP) (siloxane acrylate), and polymethylmethacrylate (PMMA) contact lenses were exposed to 1 x 10(5)/mL log phase A. castellanii (trophozoite:cyst ratio 90:10) for 10 seconds, 30 minutes, 60 minutes, and 120 minutes. The number of adherent organisms was determined by light microscopy and confirmed by scanning electron microscopy. Rates of cyst adherence were similar among contact lens types. We observed significantly greater adherence of trophozoites to RGP and PMMA lenses compared with soft contact lenses (P < 0.05). This difference in trophozoite adherence was significant at all four time periods (P < 0.05). Our findings show that A. castellanii trophozoites and cysts adhere to both soft and rigid contact lens types. We also found that although trophozoite adherence increases as a function of duration of exposure, adherent organisms were observed with exposure times as brief as 10 seconds. This suggests that all contact lens types may be at risk for Acanthamoeba attachment and that even minimal exposure times may be sufficient for lens contamination.

Acanthamoeba↗
PubMed1992

Is atopy a risk factor for the use of contact lenses?

We studied the tolerance of soft contact lenses (CL) in 24 atopic (16 with hay fever) and 52 non-atopic subjects with a mean age of 20 years. They were examined when they first came to an ophthalmologist to have CL and re-examined after an average of 1.7 years. All subjects were allowed to use CL throughout the year, including the pollen season. Of the 76 subjects, 31 (41%) reported some kind of eye symptoms during the use of CL. Six subjects (8%) had stopped using CL because of symptoms. Altogether, in 29/76 subjects (38%) some objective sign was detected in the examination, confirming the subjective symptoms (conjunctivitis 16, keratoconjunctivitis 8, increased limbal blood vessels 4, and eczema palpebrae 1). Fourteen of the 24 atopics (58%) had experienced symptoms compared with 17 of the 52 non-atopics (33%) (p = 0.034). Eleven atopics had seasonal eye symptoms, and eight of them (73%) had problems with CL use. Eosinophils and neutrophils found in the conjunctival scrapings at the first examination appeared to predict poor CL tolerance when the occurrence of symptoms in different groups was first compared by bivariate analysis. The risk factors that could predict poor CL tolerance were also evaluated, with logistic regression analysis controlling potential confounders. History of an atopic condition increased 5-fold the risk of experiencing various external eye symptoms during the use of CL. We conclude that seasonal atopic allergy is a especially risk factor for wearing soft contact lenses, and their use should be restricted during the season.

Adolescent↗