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Convenience and safety are major motivating factors in the choice of a mode of correction for refractive errors. Extended wear of contact lenses is associated with greater convenience than daily wear, but questions remain concerning the safety and risks associated with this modality. This paper investigates the hurdles that have rendered extended wear an unfavorable option thus far and seeks to identify strategies to overcome these obstacles.We review the history of extended contact lens wear, focusing on soft extended wear for cosmetic use. Results of incidence and relative risk studies for the major complications are scrutinized. The factors that are associated with increased risk together with mechanisms which have been proposed on based on scientific research are analyzed to derive strategies for preventing adverse reactions in extended wear.Infectious keratitis associated with extended wear of contact lenses has been identified by the community as a major issue, although the degree of concern may be disproportionate. Current perceptions of the relative risk of extended wear versus daily wear in the context of the risk for nonwearers may be misplaced, and the role of eye closure versus consistency and duration of wear remains open to debate. In the minds of practitioners and patients, other adverse reactions may be of greater significance in rejecting extended wear. Nonetheless, the potential extent of injury from infection demands attention. Studies collectively attest that corneal hypoxia during extended wear is a potential causative mechanism in infectious keratitis, suggesting that the provision of higher oxygen levels to the cornea will reduce morbidity rates from this unwanted complication. However, the issues of stagnation of the post-lens tear film during eye closure, mechanical properties of the lens, and lens movement remain unresolved and may prove to be contributing factors to adverse responses.Attention to oxygen permeability and mechanical properties of soft contact lenses should solve the remaining problems with extended wear. Materials currently under development promise to meet at least some of the desired properties and may lead to the long-awaited advent of safe extended wear.

To investigate the effect that extended wear of a tight necktie has on the intraocular pressure (IOP), measured by Goldmann applanation tonometry in a normal and aged-matched glaucoma group.One eye of 18 normal and 19 primary open-angle glaucoma patients was included in this prospective study. The intraocular pressure of each patient's randomly selected eye was measured with the patient dressed in an open shirt collar, again 3 minutes after their collar was fastened and necktie tightened, again after a further 12 minutes, and finally 3 minutes after the necktie was loosened and collar unfastened. The same examiner performed all measurements in a masked fashion.The mean intraocular pressure in the normal group (n = 18) increased by 0.56 mm Hg (P = 0.30) and increased significantly (*) in the glaucoma group (n = 19) by 1.58 mm Hg (P = 0.001*) after tightening the necktie for 3 minutes. The mean IOP then decreased after leaving the necktie on for a further 12 minutes, by 0.89 mm Hg (P = 0.08) in the normal group and decreased significantly by 0.94 mm Hg (P = 0.04*) in the glaucoma group. Finally after loosening the necktie for 3 minutes (immediately after 15 minutes of continuous necktie wear) the mean IOP decreased in the normal group by 0.89 mm Hg (P = 0.02*) but only minimally in the glaucoma group by 0.16 mm Hg (P = 0.72). The patient's age or collar size showed no significant correlation with the change in mean IOP following tight necktie wear.A significant increase in IOP after 3 minutes of tight necktie wear occurred only in the glaucoma group, but this increase was followed by a significant decrease in IOP after 15 minutes of tight necktie wear. Avoidance of wearing a tight necktie over an extended period is therefore not necessary in patients with glaucoma.

Generally in keratoconus the corneal apex displacement is inferior in position and bilateral in expression. Two young male keratoconic subjects enrolled in the Dundee University Scottish Keratoconus Study (DUSKS) demonstrated with corneal topography the presence of unilateral superior keratoconus. Successful visual rehabilitation of a superior cone with contact lens fitting represents a particular challenge to the contact lens practitioner. This report discusses the management of two such cases.

During an eight-day study of the eye's response to hydrogel contact lenses worn continuously, the open eye endothelial bleb response, having rapidly decayed from its overnight peak to a level much nearer baseline, appeared to increase again some six hours after eye opening. Further, the bleb response at eye opening each morning, the 'second phase' response seen some six hours later and the overall bleb response were all observed to decrease as the number of days of lens wear increased such that by about the fifth day the bleb response was almost imperceptible.

The contact lens industry has grown steadily during the last forty years; it will continue to expand because the public demands correction of refractive errors without the need to wear glasses. The popularity of contact lenses rests largely on their cosmetic and optical advantages as well as their usefulness in sports and professional activities. Hard plastic polymethylmethacrylate (PMMA) contact lenses were for decades the industry standard. They were inserted and removed each day, and lens care was simple. Hard lenses, however, were often irritating and uncomfortable. Soft contact lenses, made from hydroxyethylmethacrylate (HEMA), were introduced around 1970. In 1980 extended wear soft contact lenses were approved by the U.S. Food and Drug Administration for continuous (day and night) use over periods of 30 days. More recently, new rigid gas-permeable lenses have been approved for extended wear, and disposable soft extended wear lenses are currently also available. Because of their relative convenience, many users prefer extended wear soft lenses to soft (and hard) lenses requiring daily removal.

Background. Understanding the rate of contact lens-related complications and the factors that affect their occurrence can facilitate better prescribing decisions. Methods. In a managed care setting, 1496 patient visits were evaluated using a common protocol by 11 optometrists to determine the prevalence of all contact lens-related complications. Results. Over one-half (61%) of the visits were normal, with the remainder showing some type of complication. The more prevalent complications included superficial punctate staining (17.3%) and neovascularization (11.4%). Total complications were less prevalent with rigid gas permeable (RGP) and disposable lens types. Planned replacement soft lenses, used on a daily wear schedule, had the lowest prevalence of more serious complications when compared to conventional soft and disposable lenses. Patients on an extended wear schedule greater than 3 days were more likely to experience complications. The use of nonapproved care systems showed more complications, with serious complications reduced when a one-step care system was used. Conclusion. Choice of lens type, wearing schedule, and care system does affect the prevalence of complications, which underlines the importance of the recommendations of the prescriber.

To investigate the effects of experimentally induced defocus on eye growth and refractive development, one eye of four infant rhesus monkeys was fit with either a +3.0 D (N = 2) or -3.0 D (N = 2) extended-wear, soft, contact lens, and the other eye was fit with a zero-powered, control lens. The lens rearing regimen was started between 12 and 22 days of age and continued for 24 to 64 days. Hyperopic shifts in refractive error were found in all eyes, including the eyes treated with plano lenses. In addition to these absolute hyperopic shifts, 1.5 to 3.25 D of axial anisometropia were produced in all four monkeys, with the eyes wearing the powered lenses becoming relatively more hyperopic than the control eyes wearing the plano lenses. The induced hyperopia and anisometropia decreased rapidly after lens removal. The reapplication of the lenses at later ages in two animals produced smaller, but similar, changes. It appears that in very young primates extended-wear, soft, contact lenses can alter eye growth and refractive development through both visual and nonvisual mechanisms.

The influence of lens parameter variation on the frequency and persistence of rigid gas-permeable (RGP) lens adherence after overnight lens wear was investigated. In 3 separate studies, 11 subjects wore lenses of different designs in each eye over 5 nights. No significant differences in the frequency of lens adherence were found with loose vs. tight peripheral fittings (49% vs. 42%), or with 9.6-mm vs. 8.7-mm diameter lenses (42% vs. 52%). However, a significantly higher frequency of adherence was found for flat-fitting lenses compared to steep-fitting lenses (84% vs. 49%; p < 0.05, Binomial test). Adherence was also significantly more persistent after eye opening with flat-fitting lenses, whereas steep-fitting lenses regained mobility more rapidly than the other lens designs tested. These findings suggest that the "suction cup" theory of RGP lens adherence does not adequately explain this phenomenon, and that the lens parameter variations investigated in this study do not reliably reduce or eliminate lens adherence during RGP extended wear.

AIM: Although 1 week of continuous wearing time (CWT) is recommended for extended wear soft contact lenses (EWSCL), there have been few studies concerning the appropriateness of this or other CWTs. The current study was undertaken to examine the effect of various CWTs on the cornea by observing the corneal epithelium. METHODS: Specular microscopy was used to evaluate corneal epithelial changes induced by EWSCL in 19 myopic patients (24.0 (SD 6.7) years), divided into four groups: CWT of 0, 1, 3, and 6 days. RESULTS: The initial mean cell area was 628.2 (13.4) micron2. After 6 months this was 629.3 (28.6) micron2 for daily wear (ns), and 660.0 (40.9) micron2, 727.7 (49.6) micron2 (p < 0.01), and 815.5 (67.2) micron2 (p < 0.01) for CWT of 1, 3, and 6 days, respectively (p < 0.01). CONCLUSION: These findings indicate that the corneal epithelium changes proportionally with the CWT; the shorter the CWT, the better the epithelial morphology. This suggests that the CWT for EWSCL be minimised, so as to reduce the potential risk of contact lens related problems.

The binding of rigid contact lenses to the cornea is a phenomenon that is poorly understood. A variety of strategies have been advocated for the resolution of this problem. Two case reports are presented highlighting the difficulty in managing patients wearing rigid contact lenses who experience lens binding. A prospective, single-center, controlled, double-masked randomized study was conducted to determine if the regular replacement of daily-wear and extended-wear rigid contact lenses influenced the phenomenon of lens binding. Subjects, divided into four groups, wore Quantum 2 lenses (Bausch and Lomb, Rochester, NY; Dk = 120) for 12 months on either a daily-wear or an extended-wear basis: Group I: daily wear, replacement every 3 months; Group II: daily wear, no scheduled replacement; Group III: extended wear, replacement every 3 months; Group IV: extended wear, no scheduled replacement. The occurrence of binding was monitored both subjectively and objectively. Subjective binding assessment appeared to be a reliable indicator as to the occurrence of this phenomenon, whereas objective assessment appeared to provide unreliable results. The regular replacement of lenses worn on an extended-wear basis reduced the level of binding reported subjectively (p

A prospective, single-centre, controlled, double-masked randomised study was conducted to determine the benefits, ifany, of regular replacement of daily-wear rigid gas permeable (RGP) contact lenses. Forty-one subjects, divided into two groups, wore Quantum 2 lenses (Bausch & Lomb, Rochester, New York, USA; Dk=120) for 12 months on a daily-wear basis; subjects in group I replaced lenses every 3 months, whereas those in group II were not scheduled to replace lenses. All subjects were existing RGP lens wearers without any contact lens-induced pathology (>grade 1). The integrity of the lenses and the ocular responses to lens wear were monitored in both groups every 3 months. Compared with lenses worn by subjects in group II, lenses worn by subjects in group I displayed significantly less surface drying (at 9 months), less mucus coating (at 12 months), less surface deposition (at 12 months), and less surface scratching (at 9 and 12 months) (p 0.05, ANOVA). Compared with the ocular response of subjects in group II, the ocular response of subjects in group I displayed significantly less corneal staining at 12 months (p

Twelve subjects were fitted with a high water content, nonionic contact lens (Pilkington Barnes-Hind "Precision UV"), which was either replaced every month for 3 months or worn for 3 consecutive months before replacement occurred. Visual quality, high and low contrast acuity, and comfort were unaltered with either replacement schedule, but overall satisfaction was significantly greater with the shorter replacement schedule (p = 0.04). Front surface wettability revealed a large amount of intersubject variability and was reduced at the 3-month visit with the longer replacement period lenses (p = 0.003). Visible deposits also increased with longer replacement times (p < 0.05). Laboratory-based analytical results showed that both gross lipid and gross extractable protein significantly increased in the 3-month lenses compared with the 1-month lenses, with 44% less lipid accumulation and 60% less protein deposition occurring with the shorter replacement time. The results support the replacement of high water content lenses on a monthly basis.

Gram-negative bacteria may play a role in the etiology of certain soft contact lens (SCL)-related diseases. Contact lens (CL) wear may modify the normal ocular biota, providing a more favorable environment for potential pathogens. This study reports temporal changes in ocular biota in daily-wear (DW) and extended-wear (EW) disposable SCL use in experienced and neophyte wearers. Lid margin and bulbar conjunctival biota were sampled prior to CL fitting in 26 previous DW SCL users, 18 previous EW SCL users, and 26 neophytes. Wearers were fitted with an etafilcon A CL in one eye and a polymacon CL in the fellow eye. Lenses were worn on a daily basis by the 26 previous DW SCL wearers and on an EW basis by the remaining 44 subjects. The ocular biota was further sampled after 1, 3, 6, 9, and 12 months of wear. The ocular biota consisted of coagulase-negative staphylococci, Corynebacterium spp., Micrococcus spp., and Propionibacterium spp. Potential pathogens were rarely isolated at baseline. No significant trend of increasing ocular colonization was shown for extended CL wear. Lid and conjunctival colonization increased with DW SCL use (P < 0.001), although this increase occurred for nonpathogenic species only. Fewer potential pathogens were isolated from DW SCL than from EW SCL users (P < 0.05). The lid margin consistently showed greater colonization than the conjunctiva and may be a source of potential pathogens during CL wear. Hydrogel CL wear appears to modify the ocular biota. An increased number of commensal organisms were present in DW SCL use. EW SCL use altered the spectrum of organisms isolated. These alterations may suppress the normal ocular defense mechanisms and may be relevant in the pathogenesis of CL-related disease.

Objective: To record the frequency and type of complications that occur following photorefractive keratectomy (PRK) for myopia. Design: Prospective, with follow-up for 1 year. Setting: Mater Private Hospital Laser Clinic, Dublin, Republic of Ireland. Patients: One hundred and sixty one myopic eyes in 120 patients. Main Outcome Measures: Any complications occurring in the follow-up period. Patient satisfaction rating, on a graded scale, was recorded in the first 50 eyes in 50 consecutive patients at 1 year. Results: Of 161 eyes 22.4% had early complications of their procedure. These were most commonly caused by the use of routine post-laser medications. Furthermore, only 6% of 50 patients surveyed, failed to achieve their original aim (wholely or in part) in undergoing the treatment. In no case was the visual outcome compromised by non-refractive complications. Conclusions: PRK is safer than extended wear soft contact lens use.

Purpose: To study the compliance of contact lens (CL) wearers and the prevalence of CL-related ocular complications. Materials and Methods: This was a cross-sectional study conducted from December 2012 to May 2013 which included CL wearers coming to outpatient department or emergency department where these patients underwent ophthalmic examination. An interview was performed about the use and care of CLs. Results: The study included 102 patients, where 26 (25.50%) were men and 76 (74.50%) were women. Patient's ages ranged from 13 to 55 with an average (mean ± standard deviation) 29.48 years. Results showed myopia in 41 (40.19%), hyperopia 13 (12.74%), astigmatism 37 (36.27%), keratoconus 8 (7.84%), and others 3 (2.94%). More than 2/3 of the patients had, at least, one complication in their eyes. The average complication rate of gas permeable (GP) lenses was significantly (P < 0.04) lower than soft CLs (SCLs) (0.75). The most common complications were papillae, giant papillary conjunctivitis, conjunctival injection, corneal infiltrates, and corneal abrasions in both GPs and SCLs wearers. Silicone SCLs had a lower average number of complication rates per eye (0.73) than nonsilicone SCLs (0.76), but the difference was not statistically significant (P = 0.19). Extended wear CL use was associated with higher complication rate (86.84%) as compared to daily wear CL use (67.85%) and it was statistically significant (P < 0.03). Conclusion: Use of CL is associated with ocular complications. Most of these complications are minor and easily manageable. It is advised that patients should adhere with the recommendations of both manufacturer and optometrist to avoid complications.

Purpose. For 14 years, the U. S. Food and Drug Administration (FDA) and eye care practitioners have strongly discouraged patients from sleeping in contact lenses. In the past 9 months however, the FDA has approved three new hyper-oxygen transmissible lenses for up to 30-night extended wear. Is this a great advance or another clinical triumph of hope over experience? What should the public know? What should patients do? Methods. Our research group has studied all three new lenses in prospective, randomized, masked, parallel clinical trials in a single center. As an outcome measure, we looked at whether lens wear caused more bacterial binding to surface corneal cells. Results. Compared with conventional lens use, the new lenses caused no or only small increases in bacterial binding in either daily or extended wear. Furthermore, the increases seen stratified with known infection risks by both lens type (hard or soft) and wearing schedule. Indeed, early epidemiologic reports indicate that this new generation of lenses may reduce lens-related microbial infection risks by 10- to 40-fold. Conclusion. This represents a true clinical paradigm shift of the first magnitude in safety of contact lens wear. Taken together, this data suggest that patients will soon replace their current, conventional lenses with this new generation of materials for any schedule of wear.

It was widely anticipated that after the introduction of silicone hydrogel lenses, the risk of microbial keratitis would be lower than with hydrogel lenses because of the reduction in hypoxic effects on the corneal epithelium. Large-scale epidemiological studies have confirmed that the absolute and relative risk of microbial keratitis is unchanged with overnight use of silicone hydrogel materials. The key findings include the following: (1) The risk of infection with 30 nights of silicone hydrogel use is equivalent to 6 nights of hydrogel extended wear; (2) Occasional overnight lens use is associated with a greater risk than daily lens use; (3) The rate of vision loss due to corneal infection with silicone hydrogel contact lenses is similar to that seen in hydrogel lenses; (4) The spectrum of causative organisms is similar to that seen in hydrogel lenses, and the material type does not impact the corneal location of presumed microbial keratitis; and (5) Modifiable risk factors for infection include overnight lens use, the degree of exposure, failing to wash hands before lens handling, and storage case hygiene practice. The lack of change in the absolute risk of disease would suggest that exposure to large number of pathogenic organisms can overcome any advantages obtained from eliminating the hypoxic effects of contact lenses. Epidemiological studies remain important in the assessment of new materials and modalities. Consideration of an early adopter effect with studies involving new materials and modalities and further investigation of the impact of second-generation silicone hydrogel materials is warranted.

PURPOSE Compared with daily disposable wear schedule, continuous wear (CW) or extended wear of contact lenses has been associated with an increased risk of developing an ocular infection. Proof-of-principle studies were conducted to investigate the impact of daily replacement of lenses on the rate of contact lens-related ocular adverse events (AEs) during 30-night CW. METHODS A total of 215 subjects were dispensed with silicone hydrogel lenses on a 30-night CW schedule but replaced lenses daily either each night before sleeping (n = 178 eyes) or each morning after waking (n = 252 eyes). Scheduled clinic visits were conducted at 1 week and 1 month. Neophytes were required to complete 1 week of daily wear before commencing CW. A historical control (n = 191 eyes) using the same site, subject demographics, and visit schedule but monthly lens replacement was used for AE rates. RESULTS Logistic regression analysis showed a significant reduction in mechanical AEs (0.8 vs 5.2%, p = 0.01) and overall AEs (inflammatory and mechanical events) (4.0 vs 8.9%, p = 0.04) when lenses were replaced each morning compared with being replaced monthly. Estimation of handling-related lens contamination of unworn lenses in a subgroup of subjects showed isolation of Staphylococcus aureus from the lenses of 35% of subjects, and 65% of subjects had more than 1000 colony-forming units per lens of gram-positive bacterial contamination. CONCLUSIONS Morning lens replacement during CW reduced mechanical and overall ocular AEs. Replacing lenses at night had no beneficial effects perhaps because the benefit of a fresh lens at night might be partially negated by contamination of the contact lens caused by lens handling before overnight eye closure. Contact lens wearers on an extended wear or CW schedule should be advised to minimize lens handling before sleep to reduce the risk of complications.

To evaluate predisposing factors in subjects susceptible to solution-induced corneal staining (SICS).Four hundred forty-six existing soft contact lens wearers were randomly fitted with one of two study lenses (lotrafilcon B, CIBA Vision, or omafilcon A, CooperVision) and used a hydrogen peroxide care system (Clear Care, CIBAVision) for a 1-month period. Each subject was then challenged with the same lenses presoaked in a multipurpose solution (ReNu MultiPlus, BauschLomb) and assessed after approximately 2 h to be categorized as either "stainers" or "non-stainers" based on whether they showed a classic SICS pattern (diffuse punctate corneal staining in three or more peripheral quadrants).Overall, 36% (155 of 425) of eligible subjects were classified as stainers and included a higher proportion of omafilcon wearers: 44% (91 of 205) vs. 29% (64 of 220). After using the peroxide system, the stainers were more likely to show poorer wetting (odds ratio [OR] = 1.76, p = 0.02) compared with the non-stainers. Lens wetting showed a significant negative correlation with film deposits (r = -0.63, p0.0001, n = 425). Furthermore, on slit lamp examination, the stainers were more likely to show higher levels of upper- and lower-palpebral hyperemia (OR = 2.18, p = 0.02; OR = 1.93, p = 0.04), tarsal roughness (OR = 1.71, p = 0.01), corneal staining (OR = 17.1, p0.0001), and conjunctival staining (OR = 1.94, p = 0.004). Although not exposed to preservatives, twice as many eyes in the stainers group had some level of corneal staining: 51% vs. 25%. There were no significant differences between the stainers and non-stainers with respect to age, sex, refraction, or keratometry (p0.05).This study highlighted some notable trends in patients susceptible to SICS. The findings point toward poor tear quality as a predisposing factor for SICS.

Objectives This randomized, parallel group, single centre clinical trial was conducted to evaluate the safety and compare the whitening efficacy for an extended wear of an experimental 9.5% H2O2 high-adhesion whitening strip, relative to a marketed 10% H2O2 control strip. Methods Twenty-nine eligible adult volunteers were randomly assigned to either a treatment series with an experimental 9.5% H2O2 high-adhesion whitening strip at home for 2 h, once a day, for 8 days; or a marketed 10% H2O2 whitening strip for 30 min, on a similar daily regimen. Tooth color/whitening progression was recorded under standardized lighting conditions at baseline, day 3, day 5, and day 9, via digital imaging. Outcomes were reported using the CIELAB system. Usage safety was also assessed at each follow-up visit. Whitening efficacy for each group was investigated using a paired-difference t-test. The treatment groups were compared among each other using the analysis of covariance, with the baseline value and age as the covariates. Results Both treatment groups demonstrated statistically significant mean color improvement from baseline for b* (yellowness) and L* (lightness) at each post-baseline visit. In addition, the 2-h high-adhesion strips demonstrated significantly greater improvement in b* and L* relative to the 30-min strip group at each follow-up visit. Conclusions The 2-h regimen for the 9.5% H2O2 high-adhesion whitening strip was more efficient for tooth whitening than the 30-min regimen of 10% H2O2 whitening strip. Both treatments were well tolerated and the use of the test products during the study time frame was considered safe. Clinical relevance Extending the daily wear time of whitening strips can improve the efficacy of the treatment and ultimately shorten the length of the treatment without any significant adverse effects.

Purpose Individuals with PFL have problems moving about, and there are some optical aids that are proposed to enhance mobility performance. However, currently the efficacy of these aids cannot be determined without extended wear. This study aims to design a new clinical measure to assess the visual awareness in PFL patients, so that this new test could be used to determine the efficacy of optical aids in a clinical setting Methods PFL was simulated using goggles in 50 normally-sighted subjects. The simulated field of view (FoV) was varied from 5° to 20°. In the new test, observers were asked to search for a stimulus in a 60° field of view and the detection time (DT) & detection efficiency (DE) (DE is the Inter-quartile range of the DT responses at each eccentricity for every subject) were measured. Head and eye movements were allowed and the presentation time was unlimited. Clinical validity was investigated by correlating the DT and DE scores with the percentage preferred walking speed (PPWS) and the number of collisions on an indoor mobility course Results The DT and DE scores were inversely correlated with the FoV (r=-0.60; p

The purpose of this study was to determine the corneal epithelial alterations induced by various types of contact lenses. By employing the specular microscope, the corneal epithelia of 60 patients who had worn contact lenses for more than 1 year were re-examined along with 15 myopic controls. The morphological changes in aphakic patients who changed from extended wear soft to extended wear rigid gas permeable lenses were also studied. The mean cell area of the corneal epithelium was 621.5 (SD 92.5) microns 2 for daily wear rigid gas permeable lenses (n = 15), 645.8 (98.1) microns 2 for daily wear soft lenses (n = 15), and 634.7 (88.6) microns 2 for extended wear rigid gas permeable lenses (n = 15), none of which differed significantly from the control value of 610.5 (98.1) microns 2. Only the extended wear soft lens group (n = 15) showed significantly enlarged epithelia (806.1 (50.1) microns 2, p < 0.01 versus the other groups). The epithelium partially returned to normal after changing from extended wear soft lenses to extended wear rigid gas permeable ones. The corneal epithelium showed increased cell area only with extended wear soft contact lenses which are known to pose a risk for corneal infection.

All cases of contact lens induced keratitis (epithelial defects with an underlying infiltrate or ulcer) among cosmetic wearers in Sweden were collected in a 3-month prospective study and analyzed for risk factors in relation to lens type and wear schedule. Every ophthalmologist in Sweden was invited to participate and 100% responded. Viral cases were excluded. The number of lens wearers in Sweden, subdivided by lens type and wear schedule, was obtained in a parallel 3-month study among 71% of the lens fitters, who counted all their wearers, recording lens type and wear schedule as well as revisit and replacement schedules. The annualized incidence per 10,000 wearers was 1.48 for daily wear of rigid gas permeable lenses, 2.16 for daily wear and 10.00 for extended wear of disposable soft lenses, and 2.17 for daily wear and 13.33 for extended wear of conventional soft lenses. Thus, extended wear was associated with a significantly (P < 0.01-0.001) higher (5-6 times) risk of keratitis than daily wear. There were no other significant differences between the incidence figures. The Swedish incidence figures were approximately half as high as those reported in the U.S. Of the lesions, only 12% were located within the pupillary area and only 8% were corneal ulcers. Only three patients (12%) suffered a decrease in visual acuity. Severe keratitis was significantly (P < 0.01) more common among conventional soft lens wearers (accounting for all ulcers, all lesions within the pupillary area, and all decreases in visual acuity) than among wearers of disposable lenses.

The main clinical purpose of prescribing contact lenses on a planned replacement modality is to ensure that an optimal performance, indistinguishable from that of a new contact lens, is maintained throughout lens usage. The rate at which the performance of a contact lens is adversely affected has been shown to be highly patient-dependent. It is further suspected that other factors such as modality of wear (daily vs. extended wear), care system, and material also play a role. In the current study, we examined the effect of the contact lens material on the maintenance of an optimal performance with daily wear. To that effect, we compared the daily wear performance of a high water content, nonionic, deposit-resistant FDA Group II material (Netrafilcon A), replaced every 3 and 6 months, to that of two high water content, ionic, FDA Group IV materials, one replaced twice weekly (Etafilcon A) and the other replaced every 1 and 3 months (Vifilcon A). The study design was a single-site (Danish Contact Lens Consultants), single-masked, right/left-eye comparison. The lens performance was monitored in terms of comfort, vision, effects on ocular tissues, and contact lens in vivo wettability. The results obtained showed that changes in contact lens in vivo wettability, investigated by a noninvasive wide field technique, using the Tearscope light attachment to the biomicroscope, were the earliest to manifest. The key criterion was an increase in the surface mucus contamination of the contact lens surface; this led to the following main conclusions: (i) The replacement frequency, needed to maintain an optimal performance, is material-dependent, with FDA Group IV lenses needing to be replaced more often than deposit-resistant FDA Group II lenses. (ii) For the vast majority of patients, an optimal performance is maintained with 3-month replacement for deposit-resistant FDA Group II lenses, whereas monthly replacement is needed with FDA Group IV lenses. (iii) The rate of alteration of the lens performance is highly patient-dependent for all contact lens types tested. Selected subjects can use a very infrequent replacement schedule and maintain an optimal lens performance, whereas with some subjects, very frequent replacement is needed to achieve the same results.

A clinical investigation was conducted to determine the success rate for two groups of presbyopic subjects who wore ACU-VUE ® contact lenses on a monovision basis. Group I consisted of 172 consecutive presenting patients who had never before worn contact lenses. Group II subjects consisted of presenting or preselected presbyopes who were (a) currently wearing contact lenses for distance correction only; (b) previously unsuccessful with bifocal contact lenses; or (c) currently wearing bifocal contact lenses less than satisfactorily. Following a brief explanation of monovision, patients of both groups were simply asked if they would be interested in trying monovision contact lenses on a free trial basis. Subjects who expressed interest, and who satisfied routine eligibility and clinical performance criteria, wore lenses for either 1 week or 2 weeks. At the investigator's discretion, lenses were worn either on an extended wear disposable basis (7 days/6 nights maximum without removal) or on a daily wear 2-week replacement basis. If clinical performance was acceptable, subjects were given the option at the end of the trial to continue monovision contact lens wear as full paying patients. Of 172 Group I subjects asked, 102 (59%) responded affirmatively and 87 (51%) participated in the free trial. Of the 87 Group I subjects participating in the trial, 55 (63%) chose to continue in monovision lenses (73% of whom were still successful after 6 months). Of 72 Group II subjects asked, 67 (93%) responded affirmatively and 64 (89%) participated in the free trial. Of the 64 Group II subjects participating in the trial, 52 (81%) chose to continue in monovision lenses (81% of whom were still successful after 6 months). The study results support the contention that monovision wear of disposable or daily wear 2-week replacement contact lenses offers the contact lens fitter a significant practice-building opportunity when presented in a free trial format to potentially interested patients.

The cervical motion in three planes was evaluated in 10 subjects while they wore each of four contemporary cervical collars (Philadelphia, Miami J, Malibu and Newport Extended Wear) and no orthosis. The amount of force placed on the orthosis by the subject was controlled and monitored. The c

Traditional hydrogel soft contact lenses (SCL) have limited oxygen permeability.1, 2 Recently introduced silicone hydrogel SCL have much higher oxygen transmissibility (Dk/t O2), allowing near normal oxygen supply to the cornea during extended lid closure, and are hoped by some to address most of the problems related to corneal hypoxia encountered with previous extended wear soft contact lenses.1, 3 They have therefore been approved for up to 30 days of continuous wear in both Europe and Australia. Four cases of microbial keratitis in patients who were using silicone hydrogel SCL (either CibaVision Focus Night and Day lenses (Lotrafilicon A, fluorosiloxane hydrogel) or Bausch & Lomb PureVision lenses (Balafilcon A, silicone hydrogel)) on an extended wear basis are presented. The minimum amount of continuous wear was 24 hours. All cases were treated either in private or at the corneal clinic of the Royal Victorian Eye and Ear Hospital from December 2000 to February 2001. All the patients underwent a complete ophthalmic examination by a corneal specialist. Microbiological specimens were taken from all patients via cornea scrapings and were submitted for Gram and Blankophor staining, and bacterial and fungal cultures via direct inoculation onto sheep blood agar, chocolate agar, and Sabouraud agar. Bacterial sensitivities of cultured organisms were also obtained. Where possible, the contact lenses themselves were also sent for microbial cultures. Each case is described in brief, and a summary presented in Table 1. View this table: Table 1 Summary of case details This 22 year old man presented with a 2 day history of left ocular injection, pain, photophobia, and blurred vision. He was wearing CibaVision Focus Night and Day SCL continuously for 10 days at a time, discarding the lenses after a month of use. He had swum in the sea while wearing the same lenses 2 weeks before, after which …

PURPOSE: To determine the extent of extended wear (EW) contact lens prescribing worldwide and to characterize the associated demographics and fitting patterns. METHODS: Up to 1000 survey forms were sent to contact lens fitters in up to 39 countries between January and March every year for five consecutive years (2006-2010). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Survey data collected since 1997 was also analyzed to assess EW fitting trends since that time. RESULTS: Details for lens modality were received for 107,094 rigid and soft lens fits of which 88,392 were for soft lens daily wear (DW) and 7470 were for soft lens EW. Overall, EW represents 7.8% of all soft lens fits, ranging from 0.6% in Malaysia to 27% Norway. Compared with DW fittings, EW fittings can be characterized as follows: older age (32.7 � 13.6 vs. 29.4 � 12.0 years for DW); males are over-represented; greater proportion of refits; 72% silicone hydrogel; higher proportion of presbyopia and spherical designs; and higher proportion of monthly lens replacement. Of those wearing EW lenses, 80% use multipurpose solutions, whereas 9% do not use any care system. Between 1997 and 1999, the rate of EW prescribing decreased from 5 to 1% of all soft lens fits; it increased to a peak of 12% in 2006, and settled back to 8% by 2010. CONCLUSIONS: EW prescribing has failed to break through the "glass ceiling" of 15% and is unlikely to become a mainstream lens wearing modality until the already low risks of ocular complications can be reduced to be equivalent to that for DW.

To quantify non-polar lipids deposited on senofilcon A silicone hydrogel contact lenses (JJ Acuvue OASYS) when disinfected with a no-rub one-step hydrogen peroxide system (CIBA Vision ClearCare) and a care system preserved with PolyquadAldox (Alcon OPTI-FREE RepleniSH).Thirty existing soft lens wearers symptomatic of dryness were enrolled into a 4-week prospective, randomized, bilateral eye (lens type), cross-over (care regimen), daily wear, double masked study. Subjects were refitted with senofilcon A lenses, which were replaced biweekly. During each period of wear, participants used either the peroxide or preserved system. After each period of wear, lenses were collected and lipid was extracted using 1.5 ml of a 2:1 chloroform:methanol solution for 3 h at 37 °C. Lens extracts were analyzed for non-polar lipids [cholesterol oleate (CO), cholesterol, oleic acid (OA), triolein, and OA methyl ester] using normal phase high-performance liquid chromatography.The total lipid (sum of CO and cholesterol) detected was 34 ± 28 μg/lens for the peroxide-based system and 22 ± 21 μg/lens for the system preserved with Polyquad and Aldox (p = 0.029). Although there was no difference between products for cholesterol (1.4 vs. 1.3 μg/lens; p = 0.50), use of a system preserved with Polyquad and Aldox resulted in significantly less deposited CO (33 ± 28 vs. 21 ± 20 μg/lens; p = 0.033). Approximately, 95% of the detectable lipid deposited on the material was CO, followed by cholesterol. OA and triolein contributed1% of the total lipid and no OA methyl ester was found on any of the lenses.A care system preserved with Polyquad and Aldox removed higher amounts of CO from senofilcon A contact lenses used for 2 weeks than a peroxide-based system, in soft lens wearers who were symptomatic of dry eye.

Symptoms of contact lenses induced dry eye (CLIDE) are typically treated through application of macromolecular re-wetting agents via eye drops. Therapeutic soft contact lenses can be formulated to alleviate CLIDE symptoms by slowly releasing comfort agent from the lens. In this paper, we present an extended wear silicone hydrogel contact lens with extended, controllable release of 120 kDa hydroxypropyl methylcellulose (HPMC) using a molecular imprinting strategy. A commercial silicone hydrogel lens was tailored to release approximately 1000 μg of HPMC over a period of up to 60 days in a constant manner at a rate of 16 μg/day under physiological flowrates, releasing over the entire range of continuous wear. Release rates could be significantly varied by the imprinting effect and functional monomer to template ratio (M/T) with M/T values 0, 0.2, 2.8, 3.4 corresponding to HPMC release durations of 10, 13, 23, and 53 days, respectively. Lenses had high optical quality and adequate mechanical properties for contact lens use. This work highlights the potential of imprinting in the design and engineering of silicone hydrogel lenses to release macromolecules for the duration of wear, which may lead to decreased CLIDE symptoms and more comfortable contact lenses.

Extended wear soft contact lenses have been implicated in the increased occurrence of corneal bacterial infections. This research investigated the effects of polymer chemistry, water content, and pre-sorbed proteins upon the adherence of Pseudomonas aeruginosa to model hydrogels with chemistries similar to those of extended wear soft contact lenses. The hydrogels were exposed to washed suspensions of R aeruginosa in a laminar flow cell. Albumin, fibrinogen, desialylated fibrinogen, or mucin were deposited on the hydrogels before exposure to the bacteria. Results showed that with or without protein pre-exposure, bacterial adhesion decreased as water content increased. In the presence of the sorbed protein, the number of adherent bacteria increased by about 45%, and all four proteins caused similar increases in adhesion. Bacterial adhesion was not significantly influenced by the presence of sialic acid residues in the pre-sorbed protein.

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).

Success in contact lens wear is often judged on the basis of patient "survival" rather than the achievement of satisfactory performance based on specific criteria. In 1971, Sarver and Harris defined a series of standards for successful polymethyl methacrylate (PMMA) lens wear which incorporated criteria for wearing time, comfort, vision, ocular tissue changes, and patient appearance. In this paper we propose a revision of these criteria based on current understanding of the ocular response to contact lens wear. These revised CCLRU (Cornea and Contact Lens Research Unit) standards for success are intended as realistic performance objectives, and can be applied in clinical trials to evaluate and compare the clinical performance of present and future rigid and soft contact lenses, worn for daily and extended wear.

A number of reports of serious ocular complications due to contact lens wear and lack of proper after-care services in Tianjin, China, have aroused the interest of staff members at the Hong Kong Polytechnic. A visit was arranged to Tianjin Eye Hospital to review and report on the local contact lens-fitting situation. About 82% of the contact lenses fitted by the hospital during the review period were for extended wear. The major problems found in the Tianjin contact lens practice were poor general hygiene in the environment, limited knowledge of contact lenses and complications of contact lens wear, poor service and sense of responsibility toward the patient, and lack of patient compliance.

Contact lenses made of conventional hydrogel materials were defined according to their abilities to supply equivalent corneal oxygenation. Human EOP was mathematically solved according to water content (WC) and thickness (L), by algebraic combination and simplification of two empirical linear semilogarithmic equations involving equivalent oxygen percentage (human EOP), gas-to-gas oxygen transmissibility (Dk/L), and oxygen permeability (Dk). The resultant equation revealed a new clinical “rule of thumb” concerning conventional hydrogel “soft” lenses, for within the range of applicability (4–19% EOP), a change of 10% water content (e.g., from 45 to 55% H2O) resulted in a 2.5% change of EOP (e.g., from 6 to 8.5% O2) when thickness was held constant. Among currently available extended wear hydrogel lenses in the United States, it was shown that some lenses having water contents from 55 to 60% maximized the central corneal oxygen supply, presumably because the required critical thicknesses for lenses of higher water content more than offset the “oxygen advantage” in terms of material permeability. Future contact lenses made of nonconventional hydrogel materials may become clinically feasible, i.e., these materials could have permeabilities greater than those predicted on the basis of water content. Such materials may be necessary to upgrade gel lenses into those high- and super- Dk L ranges now occupied by lenses made of nonhydrogel materials, and for soft contact lenses to more effectively compete with other forms of ametropic optical correction.

We conducted a historical cohort study of 2,433 cosmetic contact lens wearers (1,055 conventional [non-disposable] daily wear lens users, 905 disposable extended wear lens users, and 473 conventional extended wear lens users) in order to estimate the rates of occurrence of complications and symptoms among disposable extended wear contact lens users and compare these rates with those for conventional soft daily wear users and conventional soft extended wear users. Data were abstracted from the office records of eight eye care practitioners for the period February 1987 through April 1989. The prevalence of all complications for disposable extended wear lens users was not significantly different from the prevalence for conventional daily wear lens users but was significantly lower than the prevalence for conventional extended wear lens users. The incidence of ulcers among disposable extended wear lens users did not differ significantly from the incidence found with conventional extended wear, but was significantly higher than the rate for conventional daily wear. Disposable extended wear lenses, in contrast to conventional extended wear lenses, may be more strongly associated with benign peripheral infiltrates than with the more serious central ulcers. Disposable extended wear lens users reported symptoms less frequently at routine scheduled visits than both conventional daily wear and conventional extended wear users and had a lower rate of unscheduled visits for complications and symptoms.

Pseudomonas aeruginosa adherence in vitro to perfilcon A (ionic, 71% H2O) extended wear soft contact lenses--both new and after 7 days of continuous wear on closed rabbit eyes--was found to be related directly to the bacterial concentration in the contaminating solution. Thirty rabbits wore perfilcon A lenses for 7 days with complete lid closure to mimic contact lens overwear. After 7 days, conjunctival cultures showed no growth of pathogens, but all corneas had developed epithelial cell exfoliation and/or epithelial defects and stromal edema. The lenses were then incubated in various concentrations (10(7), 10(6), 10(5), 10(4), and 10(2) colony-forming units per milliliter or saline control; n = 5/group) of P. aeruginosa suspensions and replaced on their respective corneas with tarsorrhaphies for an additional 48 h. By day 9, corneal thickness had increased significantly, and P. aeruginosa keratitis had developed in 13 of 25 bacterially exposed eyes but not in 5 control eyes. Although with decreasing P. aeruginosa concentration the prevalence of ulcerative microbial keratitis also decreased, the initial concentration of bacteria or the initial extent of soft contact lens-induced corneal damage had no influence on the ultimate clinical severity of the disease.

Contact lens wear, more particularly the extended wear of soft contact lenses, can produce corneal vascularisation, but the incidence and management are poorly documented in the literature. In this study we assessed the limbal blood vessel changes in a group of contact lens wearers during the course of 6 months of continuous wear of disposable soft lenses. The techniques of red free video angiography and fluorescein angiography were found to highlight the dynamics of the limbal vascular changes that occurred. The clinical significance of the findings is discussed and current theories of corneal vascularisation are reviewed.

The present investigation concerns the validation of testing visual performance of disposable contact lenses soon after insertion as a means of predicting their performance over their normal length of intended use. The evaluation was carried out on a group of 40 subjects over 1 week of extended wear with two contact lens types to represent Group I (SeeQuence 2™) and Group IV (Acuvue®) disposable lenses. The investigation involved the measurement of visual acuity with Logmar progression charts (Regan Contrast Sensitivity letter charts) of two different contrasts (92 % and 6%) at two luminance levels (250 and 2.5 cd/m2) and the evaluation by questionnaire of the subjejcts' visual acceptance. The results indicate the following: (i) The evaluation of the visual performance of a disposable contact lens, after 30 minutes of wear, is a reliable predictor of the performance achieved by the lens over the overall period of use for both Group I and Group IV disposable lenses. (ii) For the visual acuity (VA) evaluation routine used, involving measurements made to the nearest letter with two logMAR charts (contrasts 92% and 6 %), under two luminance levels (250 cd/m2 and 2.5 cd/m2), an overall difference of half a VA line was associated with a significant difference in subjective vision and is therefore considered clinically significant. (iii) The visual subjective acceptance of disposable hydrogel extended wear lenses was lowest at waking, a daily phenomenon not indicative of a permanent loss of performance with increased lens usage. (iv) The visual performance in terms of visual acuity and subjective visual acceptance was intrinsically higher with Acuvue than with SeeQuence 2 and remained unchaged for both lenses during the 1 week extended wear. This confirms that from a visual performance standpoint dispensing contact lenses for 1 week of wear achieved the intended objective of replacing lenses prior to loss of performance. (v) The reliability of the subjective scales used was confirmed by the results obtained for overall patient satisfaction ratings. These nonspecific ratings indicated that a greater overall satisfaction was achieved with Acuvue than with SeeQuence 2, confirming both the greater comfort and subjective vision obtained with Acuvue than with SeeQuence 2.

Objectives To estimate the rate of corneal erosion coupled with gram-negative bacterial contamination of contact lenses and compare this with the rate of microbial keratitis (MK) with contact lenses. Methods The rate of corneal erosion and contact lens contamination by gram-negative bacteria were calculated from several prospective trials. These rates were used to calculate the theoretical rate of corneal erosion happening at the same time as wearing a contact lens contaminated with gram-negative bacteria. This theoretical rate was then compared with the rates of MK reported in various epidemiological and clinical trials. Results Corneal erosions were more frequent during extended wear (0.6-2.6% of visits) compared with daily wear (0.01-0.05% of visits). No corneal erosions were observed for lenses worn on a daily disposable basis. Contamination rates for lenses worn on a daily disposable basis were the lowest (2.4%), whereas they were the highest for low Dk lenses worn on an extended wear basis (7.1%). The estimated rate of corneal erosions occurring at the same time as wearing lenses contaminated with gram-negative bacteria was the lowest during daily wear of low Dk lenses (1.56/10,000 [95% CI: 0.23-10.57]) and the highest during extended wear of high Dk lenses (38.55/10,000 [95% CI: 24.77-60.04]). These rates were similar in magnitude to the rates reported for MK of different hydrogel lenses worn on differing wear schedules. Conclusion The coincidence of corneal erosions during lens wear with gram-negative bacterial contamination of lenses may account for the relative incidence of MK during lens wear with different lens materials and modes of use.

There have been significant improvements in toric soft contact lens design over the past decade. Data from our international contact lens prescribing survey were mined to assess recent trends in toric soft contact lens fitting. This survey was conducted by sending up to 1000 survey forms to contact lens fitters in Australia, Canada, Japan, the Netherlands, Norway, the UK and the USA each year between 2000 and 2009. Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the forms and to return them to us for analysis. The data revealed a gradual increase in the extent of toric soft lens fitting this century. Excluding Japan – which had a consistently low rate of soft toric lens fitting over the survey period – soft toric lenses now represent over 35% of all soft lenses prescribed; it can be assumed that, on average (and again excluding Japan), all cases of astigmatism 0.75 D or less remains uncorrected among contact lens wearers. Toric lenses are fitted more to those who are older, full-time wearers and reusable lens wearers, and less to those wearing silicone hydrogel and extended wear lenses.

Purpose. Silicone hydrogel (SH) lenses are usually replaced after 2 weeks (2W) or 1 month (1M); however, many patients do not comply with the manufacturers’ recommended replacement frequency (MRRF). The purpose of this analysis was to investigate the effect of compliance with MRRF on comfort and vision in SH wearers. Methods. As a part of a larger study investigating compliance with MRRF, patients were asked to rate their subjective comfort and vision from 0 (very poor) to 10 (excellent) in the morning, at the end of the day (EVE), when lenses were new, and needed replacing (NR). Results. One thousand three hundred forty-four patients wore 2W replacement modality (2WR) (n 717) or 1M replacement modality (1MR) (n 617) SH lenses. Comfort and vision in the morning and when lenses are new were significantly higher than for EVE and NR (p 0.001). Twenty-nine percent (95% confidence interval 25.3–32.4) of 1MR and 59% (95% confidence interval 55.5–62.7) of 2WR wearers were non-compliant with the MRRF. Compliance had a significant effect on EVE (p 0.002, p 0.008) and NR (p 0.001, p 0.001) comfort and vision. After accounting for compliance, EVE and NR comfort and EVE vision were higher for 1MR than 2WR (p 0.015, p 0.044, p 0.019). Conclusions. Compliant patients had better EVE and NR comfort and vision than non-compliant patients, regardless of replacement modality. Optimal subjective performance with SH lenses seems to be facilitated by replacing lenses as recommended. (Optom Vis Sci 2010;87:1–●●●)

Extended wear has long been the 'holy grail' of contact lenses by virtue of the increased convenience and freedom of lifestyle which they accord; however, this modality enjoyed only limited market success during the last quarter of the 20th century. The introduction of silicone hydrogel materials into the market at the beginning of this century heralded the promise of successful extended wear due to the superior oxygen performance of this lens type. To assess patterns of contact lens fitting, including extended wear, over the past decade, up to 1000 survey forms were sent to contact lens fitters in Australia, Canada, Japan, the Netherlands, Norway, the UK and the USA each year between 2000 and 2009. Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Analysis of returned forms revealed that, averaged over this period, 9% of all soft lenses prescribed were for extended wear, with national figures ranging from 2% in Japan to 17% in Norway. The trend over the past decade has been for an increase from about 5% of all soft lens fits in 2000 to a peak of between 9 and 12% between 2002 and 2007, followed by a decline to around 7% in 2009. A person receiving extended wear lenses is likely to be an older female who is being refitted with silicone hydrogel lenses for full-time wear. Although extended wear has yet again failed to fulfil the promise of being the dominant contact lens wearing modality, it is still a viable option for many people.

A strategy is developed for identifying cutting tool wear on a face mill by automatically recognizing wear patterns in the cutting force signal. The strategy uses a mechanistic model development to predict forces on a lathe under conditions of wear and extends that model to account for the multiple inserts of a face mill. The extended wear model is then verified through experimentation over the life of the inserts. The predicted force signals are employed to train linear discriminant functions to identify the wear state of the process in a manner suitable for on-line application.

As part of a study examining the effects of contact lens extended wear in monkeys (Macaca fascicularis), reversible endothelial changes were observed in the cornea with slit lamp biomicroscopy and contact specular microscopy. These changes were associated with anterior eye inflammation in four monkeys (as occurs in humans). However, in two monkeys no obvious cause for these changes other than the presence of a contact lens on the cornea was apparent. In these two monkeys the endothelium displayed features similar to the transient endothelial bleb response, which has been observed only in humans. The monkey (M fascicularis) may thus be an appropriate model for further investigation of the endothelial response during anterior eye inflammation and the transient endothelial bleb response.

The present investigation assessed the performance of the 02 series lenses used on an extended wear modality, on a disposable/regular replacement schedule. In this study, the lenses were not replaced, but lens performance was monitored in order to detect any change upon which to decide the “optimal” replacement frequency. The objectives of the present study were to investigate the possible benefits of individually prescribing lens replacement schedules. To date the study has shown the following: 1. (i)The extended wear performance of 02 series lenses in time is highly patient-dependent. 2. (ii) If the replacement frequency is chosen based upon changing lenses before any significant alterations (in lens wettability, subjective comfort, or vision) take place, the necessary replacement frequency will vary between I week and 3 months among a representative contact lens population. 3. (iii) For current wearers, those who are symptomatic with their own lenses will require early lens replacement, most likely I week (65% cases), whereas those that are asymptomatic will need to replace their lenses only every 2 weeks to 3 months. In conclusion a management strategy is proposed to advise patients and to decide on the required regular replacement frequency (based upon monitoring the changes in “keratometer” breakup time, lens front-surface deposits, and subjective comfort and vision) that is feasible in routine practice.

A 12-month clinical trial involving 88 subjects was undertaken to compare the clinical performance of rigid gas-permeable contact lens extended wear (EWRGP) with that of RGP daily wear (DWRGP) lenses and soft lens extended wear (SLEW) with medium water content lenses. Withdrawals from the EWRGP group tended to result from lens-related problems, whereas the SLEW withdrawals generally resulted from adverse effects on corneal physiology. Changes in spherical refractive error during the 1-year study were small (less than 1.00 D) and similar for both gas-permeable lens-wearing groups. Most of the SLEW group (58%) showed an increase in myopia and the mean increase was 0.38 D, which represented a significant difference from the EWRGP group. The EWRGP group showed a mean flattening in corneal curvature of 0.11 and 0.15 mm in the flattest and steepest corneal meridians, respectively. A positive correlation was noted between change in corneal curvature and baseline corneal astigmatism, which suggests corneal molding as a result of lid pressure as the most likely cause. The DWRGP and SLEW groups showed small, nonsignificant changes in corneal curvature. Most of the EWRGP subjects (69%) who completed the study showed increased corneal distortion. This compares with 30 and 17% with the DWRGP and SLEW groups, respectively. Likely corneal edema was a major contributory factor. For most of the slitlamp variables monitored, there were no significant differences between the groups. However, microcystic changes were detected in both EWRGP (35%) and SLEW subjects but not in the DWRGP group. Corneal staining was noted in all groups but was more prevalent among the EWRGP group. The findings of this study are discussed in relation to the clinical management of RGP extended wear.

A retrospective study of patient records from the Indiana University School of Optometry Contact Lens Clinic was conducted for the period of June to December 1990. This investigation compared the frequency of wear-related complications of conventional soft contact lenses and disposables. All clinic patients wearing daily and extended wear disposable lenses during the 6-month period were used in the study. The control group was selected by pulling every third patient information card on a randomly selected day each week from June to December 1990. The records of the soft contact lens wearers in this group were studied. For the purposes of statistical analysis, patients were also matched for age and sex and placed into modality-specific groups, and the frequency of wear-related complications was analyzed. Patients wearing disposable contact lenses were found to have a 0.33 times estimated risk of experiencing wear-related complications when compared to patients wearing conventional lenses. The data also indicate that the frequent replacement of lenses reduces the complications of giant papillary conjunctivitis and lens deposits.