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Extended wear of contact lenses is an attractive alternative to daily wear regimens. Immediate application has been for therapeutic purposes. Recently, cosmetic investigations have occurred, primarily outside of the United States. Regardless of the application, extended wear requires careful patient selection, fitting and post-fitting care to insure that ocular integrity has not been disturbed.
Disposable soft contact lenses (DSCLs) have been marketed as a safer alternative to conventional soft lenses. Extended-wear DSCLs are designed for one or two weeks of continuous use before disposal. Those for daily wear are designed for use as conventional daily wear soft lenses, with daily removal and storage for 2 to 4 weeks before disposal. Beside minor complications, such as corneal abrasion, giant papillary conjunctivitis and toxic epithelial reactions to contact lens solutions, the most serious complication occurring in contact lens users is ulcerative keratitis. Several case-control studies performed over the last years, demonstrated that disposable contact lenses were associated with a 14-fold excess risk of ulcerative keratitis compared with that for patients wearing conventional daily-wear soft contact lenses and a 13-fold excess risk compared with that for wearers of rigid gas permeable contact lenses. However, the major risk factor for corneal ulceration in contact lens wearers is overnight lens wear of 1 to 3 nights. It was estimated that 49 to 74% of cases of contact lens associated ulcerative keratitis could be prevented by eliminating overnight wear.
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The adherence of microorganisms to contact lenses may be an important initial step in the pathogenesis of contact lens-associated infectious keratitis. Using a strain of Candida albicans whose interaction with various polymers has been well characterized we systematically investigated the adherence of this pathogen to hard hydrophobic and soft hydrophilic extended-wear contact lenses. Yeasts adhere to the hydrophobic lenses in direct proportion to the wetting angle of the lens whereas yeasts adhere to the hydrophilic lenses in direct proportion to the water content of the lens. Tear proteins such as albumin, lactoferrin, and lysozyme in addition to fibronectin enhance yeast adherence to both types of lenses (P less than 0.01). Concanavalin A reduces adherence of yeasts to both lens types (P less than 0.01). Among tear components however, only mucin (0.5%) consistently reduced yeast adherence to both lens types. Hydrophilic extended wear lenses worn for at least 28 days by normal patients consistently had greater adherence of yeasts than unworn lenses of the same type, often as much as ten-fold or greater yeasts/mm2 of lens surface area (P less than 0.05). These investigations indicate that tear components both in solution and adsorbed to the lens surface enhance microorganism adherence to contact lenses.
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BACKGROUND: Contact lenses play an important role in the management of childhood aphakia. However, the use and care of the lenses can be challenging. The aim of this study was to determine how parents coped and what problems they encountered. METHODS: Thirty-one families of aphakic children who were fitted with contact lenses between 1990 and 1997 were contacted and invited to participate in a telephone survey. RESULTS: Thirty families agreed to participate. Eighteen families (60%) were still using contact lenses successfully at the time of the study. Four families (13.3%) stopped using contact lenses within a year because of overwhelming difficulties handling the lenses. There was an initial learn-ing process that was often stressful and frustrating. The learning curve lasted from 1 to 24 months (first quartile 2.0 months; median 3.3 months; third quartile 15.0 months). The personality of the parent, temperament of the child and the frequency at which problems occurred may all have contributed to how each family coped with the lenses. Common initial problems included inserting the lenses into the eyes of an uncooperative child and the loss of lenses. Other problems included irritation associated with dryness, and the financial cost of maintaining the lenses. CONCLUSION: Although most parents initially found contact lenses daunting, 70% of families surveyed eventually learned to cope well. Parents felt that proper education of both parents and children on why the lenses were required, a good appreciation of problems that may occur, a strong social support network and adequate financial aid were important factors in learning to cope.
This paper discusses contact lenses in a military environment and reports the results of a literature survey, an extensive questionnaire sent to 1400 spectacle and contact lens wearers, and a short questionnaire given to soldiers taking part in a large scale and long military maneuver. Only a small number of publications were found concerning the relation between adverse environmental conditions and contact lens wearing. In Vietnam dust and poor hygiene often led to eye irritations that precluded the wearing of contact lenses by soldiers. Nevertheless, persons in the army are often in favor of contact lenses. In the air force and navy, wearing contact lenses seems compatible with nearly all military duties. A questionnaire was sent to all known contact lens wearers in the Dutch army and air force and to about an equal number of spectacle wearers. The responses indicate that the proportion of contact lens wearers is 1.8%. The distribution of hard vs. soft lenses was 60 and 40%, respectively. Military personnel wore their lenses during nearly all daily activities. Most contact lens wearers were of the opinion that in military conditions contact lenses have advantages over spectacles. To obtain more information on field exercises, a second questionnaire was handed out immediately after a large-scale NATO field maneuver. Twenty percent of the contact lens wearers had decided in advance not to wear their lenses, but another 30% ceased wearing their lenses during the exercise. It was recommended that for nearly all functions and/or conditions, wearing of contact lenses should be allowed, but that during extended field exercises wearing of hard contact lenses should be discouraged.
Many aircraft passengers wearing contact lenses have complained about visual disturbances, tearing and smarting of the eyes. This kind of discomfort has been named jet-set disease. The literature on this subject has been reviewed. Also my own study is reported. In that study seven test persons were examined during four hours in a decompression chamber. The atmospheric pressure was lowered to 560 millibars , which corresponds to an altitude of 4,000 metres. All test persons wore soft contact lenses. Objective symptoms were verified in four eyes after one hour and in all 14 eyes after three hours. The most serious objective findings were corneal erosions in 4 and opacities of corneal stroma in 10 eyes. The two investigators who did not wear contact lenses remained without both subjective and objective symptoms.
The study was undertaken to evaluate the efficiency of use of traditional contact lenses versus planned replacement lenses in two hundred and eighty-four patients who had worn traditional contact lenses (92 patients), quarterly replaced contact lenses (104 patients), and monthly replaced contact lenses (88 patients) in the daytime for 12 months. A comprehensive examination of patients was performed, by using an original procedure for quantitatively assessing the objective and subjective status of the visual organ while wearing contact lenses. The findings suggest that planned replacement contact lenses provide a stable and statistically higher state of the anterior chamber of the eye and comfortable wearing these lenses than that in wearing traditional contact lenses. The differences found in the clinical efficiency of use of planned replacement contact lenses and traditional contact lenses are associated with the presence of a number of factors (the degree of lens dirtying, toxicoallergic reactions of the eye to lens care agents, lens damage, the terms of wearing, etc.) that in combination with the medical and professional features of planned replacement contact lens (the possibility of rapid lens replacement, easiness-to-care) make it possible to consider, in most cases, the use of planned replacement contact lenses as medical indications that afford the patient effective prevention of complications and prolonged and comfortable wearing.
Although cosmetic extended-wear contact lenses are generally safe, they can be associated with a number of complications. A review of 124 cases of corneal ulcers treated between Jan. 1, 1982, and June 1, 1983, disclosed six cases in otherwise healthy patients (four women and two men, ranging in age from 15 to 41 years) who wore extended-wear contact lenses for correction of myopia. In five of the six, the contact lenses had undergone recent manipulation. Two patients had changed their contact lenses without proper disinfection procedures. Five of the six had been treated with antibiotics before corneal scrapings were cultured and three had been treated with corticosteroids. The cultures grew gram-negative rods (in three cases Pseudomonas organisms and in one case Serratia organisms); both patients whose cultures grew no organisms had received antibiotics. Vigorous treatment with tobramycin and cefazolin eyedrops and cycloplegics produced final corrected visual acuities of 20/20, 20/30, 20/60, 20/20, and 20/50. In the sixth case, the final uncorrected visual acuity was counting fingers at 1 foot.
Some hypermetropes, when corrected with contact lenses, appear to have a much smaller AC/A ratio than when corrected with spectacle lenses. Ocular convergence measured with contact lenses is greater than that measured with spectacles. Studies were carried out to establish the cause of these effects. Theoretical considerations are compared with the experimental results obtained. This study emphasizes the importance of the different amounts of magnification induced by contact lenses as compared with spectacles.
Contact lenses are worn by many individuals in military and civilian populations. Anecdotal reports have described contact lenses "sticking" and "freezing" to the eye during extreme cold conditions. However, some articles indicate the advantages of wearing contact lenses in cold environments. Military operations frequently taken place in cold regions; therefore, we need to known whether contact lenses can be worn safely in extreme cold. Rabbits were fitted with hard (polymethyl methacrylate) contact lenses and exposed to -28.9 degrees C temperatures with winds up to 78 mph (125 km/hr) for 3-hr periods. The wind-chill factor in these conditions exceeded -67.8 degrees C. No effects of the cold or contact lenses were seen in 85% of the eyes. A few of the eyes, both with contact lenses and without, showed mild superficial fluorescein staining of the cornea which cleared within a few ours after exposure. Histologic examination of the corneas revealed no abnormalities attributable to the cold. Inasmuch as this study showed that rabbits wearing contact lenses in extreme cold suffered no acute deleterious effects to the eyes, the research can be expanded to include human subjects.
PURPOSE: Contact lenses have assisted the refractive correction of keratoconus since the 19th century. In these case reports, the authors describe their experience with a new soft contact lens design. METHODS: The Soft K is a new soft lens comprising a thick fenestrated design to fit in patients with mild to moderate corneal distortion and fitting problems or physical intolerance to rigid gas-permeable (RGP) contact lenses. Three eyes with mild keratoconus from two 25-year-old patients (one man and one woman) were fitted with the Soft K contact lens. Both patients had previously worn other contact lens types. RESULTS: Improvements in comfort and quality of vision compared with previously worn RGP or soft toric contact lenses were the most remarkable advantages objectively observed and subjectively described by both patients. For one patient, a professional soccer player, the benefits were also important in terms of compatibility with the dynamic environment of his activity, satisfying the need for stable correction and constant full field-of-view demand without spectacles. No physiologic complications such as edema or neovascularization were observed during the follow-up period. CONCLUSIONS: This new soft lens design for irregular corneas is especially indicated for those with intolerance to RGP or other contact lenses and for patients for whom RGP lenses do not satisfy the dynamic environment inherent to some professional or leisure activities, particularly sport activity. This is a good option to consider in patients with mild to moderate keratoconus and good correction of slight or moderate irregular corneal astigmatism with good tolerance. Aftercare implications are also discussed.
Eleven subject (22 eyes) wore the best fitting lenses of each of four different types of hydrogel contact lenses (Bausch and Lomb Soflens contact lenses, Hydrocurve HCII contact lenses, AOSOFT-TM/Aquaflex hydrophilic contact lenses, and Alcon Tresoft contact lenses) in a random order for 2-3 week periods so that their short-term responses to the lenses could be evaluated and compared. None of the subjects had any contraindications to hydrogel lens wear. All the lenses centered well with proper movement. Using a double masked procedures, we evaluated each patient's response to each lens type according to the standard of success of Sarver, Harris and Polse. Approximately 63% to 72% of the patients were successful with each lens type. We found no statistically significant differences in the patients' responses to the different lens types, even though individual differences were found. The majority of our subjects were successful with several or all of the lens types evaluated.
Measurements were made of the amplitude of accommodation for myopes wearing spectacles, rigid contact lenses, and flexible contact lenses. Both forms of contact lenses placed greater accommodative requirements on the myope than did spectacle correction, but no significant difference was found between the 2 types of contact lenses in this respect.
The use of contact lenses by firefighters is currently prohibited. However, many firefighters may benefit from this form of visual correction, without predisposing themselves to additional risk. Visual benefits gained by contact lens wear may increase a firefighter's safety. To determine if it is safe to allow firefighters to use contact lenses 29 were fitted with soft contact lenses and 21 with rigid gas permeable contact lenses. Questionnaires were completed prior to fitting, after 1, 4 and 10 months of contact lens wear. Both soft contact lens (SCL) wearers, and rigid gas permeable contact lens (RGPCL) wearers showed a statistically significantly reduction in the frequency with which they experience irritable foreign bodies and irritant fumes in the eyes, compared to not wearing contact lenses. Firefighters felt that their performance on the fireground had been improved by the use of contact lenses. SCL wearers also benefited from a reduction in the frequency with which they experienced watery eyes and ocular discomfort. There were significantly fewer problems encountered with SCL wearers than RGPCL wearers. The frequency with which firefighters experienced lenses falling out, lens displacement, watery eyes, ocular discomfort, and operational difficulties was significantly less for the SCL group than the RGPCL group. SCL appear to offer considerable benefits for firefighters with refractive error, but their use cannot be sanctioned without assessment of their effect on the ocular adnexa.
Gas-permeable cellulose acetate butyrate (CAB) contact lenses may often be worn succesfully by aphakic and other patients who are unable to wear hard contact lenses. The comfort characteristics of the CAB lenses are betweeen those of hard and soft contact lenses. They are much more permeable to O2 and CO2 than soft lenses and thus are less apt to cause edema. They are more flexible and more wettable than hard lenses. This study presents 50 patients who, having had to discontinue wearing hard contact lenses because of discomfort, diffuse central corneal edema, or visual problems, were fitted with CAB contact lenses. Thirty of the fifty were able to wear the CAB lenses successfully.