Lens Replacement Research Articles

Characterization of patients who report compliant and non-compliant overnight wear of soft contact lenses

To describe compliant and non-compliant overnight wear (EW) of soft contact lenses from a large observational study. A retrospective chart review of 3211 SCL patients with known EW status (aged 8-33yrs, SCL power +8.00 to -12.00D) captured data from 10,516 clinical visits (2006-2009). Status of EW was either daily wear (DW), compliant EW (overnight wear of US Food & Drug Administration (US FDA) EW-approved lenses), non-compliant EW (overnight wear of DW-approved lenses). The effect of demographic and clinical characteristics on the likelihood of reporting EW was examined using logistic regression. Additionally, the effect of these same characteristics on the likelihood of non-compliant EW was assessed with logistic models. Eight-hundred and eight patients (25.2%) reported EW. Non-compliant EW was reported by 6% of wearers (13 hydrogel, 2 silicone hydrogel brands) In multivariate models, patient age and lens replacement schedule were significant factors for EW (vs. DW) and for non-compliant (vs. compliant) EW (p<0.0001). Other factors significantly related to EW were gender, smoking, lens material, sphere power, and years of CL wear (p≤0.007, all). Young people (ages 18-25yrs), males, smokers, myopes, silicone hydrogel lens wearers and patients with >1yr of CL wear were significantly more likely to report EW. Non-compliant EW occurred often in young people and daily disposable wearers, though many brands had non-compliant EW use. Understanding who is likely to wear EW and non-compliant EW will help clinicians pointedly counsel patients more at risk on best practices with EW.

Patient attitudes and behavior regarding hygiene and replacement of soft contact lenses and storage cases

To review important aspects of contact lens compliance and to survey contact lens replacement frequency, steps in lens care and hygiene and replacement of the lens storage case via online surveys. Random US samples (n=645 and 787) of frequent replacement contact lens wearers answered questions on contact lens wear in online, sponsor-masked surveys. Wearers of lenses prescribed by their practitioner for 2 weekly replacement reported that they replaced lenses as follows: within 2 weeks 45%, within 3 weeks (minor stretching) 68%, within 4 weeks 89%, ≥8 weeks (extreme stretching) 4%, compared to Monthly wearers who reported: within 4 weeks 37%, within 5 weeks (minor stretching) 57%, ≥8 weeks 23% (≥8 weeks extreme stretching, Chi-square p=0.001). Median frequency for cleaning lens storage case was 2-3 times per week, while 33% reported cleaning monthly or less often. Median lens storage case replacement was every 4-6 months, while 48% reported annual replacement or less often. Most patients cleaned their lens case with hot or cold tap water (72%). These internet surveys revealed significant non-compliance with lens care steps, case hygiene and lens replacement schedule. More than half of the contact lens wearers surveyed were not compliant with their 2-weekly or monthly schedule. Lenses prescribed for longer replacement intervals can lead to more extreme stretching of lens life. To encourage better patient habits, eye care providers should reinforce their recommended frequency of replacement of lenses and storage cases and should reinforce care and hygiene steps at each patient visit.

Achieving Best Visual Outcomes with a Monofocal Intraocular Lens

Specific monofocal intraocular lens (IOL) design features have been integrated over time to provide improved vision performance after lens replacement surgery. Features of the AcrySof® IQ single-piece monofocal IOL (SN60WF, Alcon Laboratories) include architectural, chemical, and surface characteristics that improve performance over earlier designs. The architectural features include single-piece construction with low resistance to compression, 3D haptics for easy implantation, and predictable and stable long-term positioning. The foldable hydrophobic acrylic plastic provides efficient light focus and incorporates ultraviolet (UV) radiation and light-normalized spectrum transmission characteristics. The plastic’s surface incites minimal post-operative uveitis and capsule reaction and also resists epithelial cell proliferation. The biconvex optic is asymmetric with most of the power incorporated into the anterior surface to reduce dysphotopsia. The posterior surface has a base convexity and incorporates an aspheric modification. The optic’s square edge provides a barrier that discourages epithelial cell invasion and consequent posterior capsule opacification and need for neodymium-doped yttrium–aluminum–garnet (Nd:YAG) posterior capsulotomy, and is frosted to reduce dysphotopsia.

Compliance with soft contact lens replacement schedules and associated contact lens–related ocular complications: The UCLA Contact Lens Study

Background Failure to comply with the manufacturers’ recommended replacement frequency (MRRF) is expected to result in ocular complications. The goal of this study is to evaluate the empirical relationship between compliance with MRRF and the presence of ocular complications. Methods All soft contact lens-wearing patients who presented at either of 2 clinics were evaluated prospectively for contact lens-related complications and for compliance with MRRF. Results Compliance with MRRF varies significantly across replacement modality ( P < 0.01) and lens solution type ( P = 0.04). Among noncompliant patients, average days of overwear beyond MRRF significantly varies across age group ( P = 0.02), lens material type ( P = 0.01), and lens solution type ( P = 0.02). Regression analysis controlling for demographic factors and lens and solution type found a marginally significant ( P = 0.07) positive effect of days of overwear on average complications per eye. Conclusions We find noncompliance broadly present across demographic groups and patient types and marginally positively related to complications.

Redefining tissue engineering for nanomedicine in ophthalmology

Working at the nanoscale means to completely rethink how to approach engineering in the body in general and in the eye in particular. In nanomedicine, tissue engineering is the ability to influence an environment either by adding, subtracting or manipulating that environment to allow it to be more conducive for its purpose. The goal is to function at the optimum state, or to return to that optimum state. Additive tissue engineering replaces cells or tissue, or tries to get something to grow that is no longer there. Arrestive tissue engineering tries to stop aberrant growth which, if left uncontrolled, would result in a decrease in function. Nano delivery of therapeutics can perform both additive and arrestive functions influencing the environment either way, depending on the targeting. By manipulating the environment at the nanoscale, the rate and distribution of healing can be controlled. It infers that potential applications of nanomedicine in ophthalmology include procedures, such as corneal endothelial cell transplantation, single retinal ganglion cell repair, check of retinal ganglion cell viability, building of nanofibre scaffolds, such as self-assembling peptides, to create a scaffold-like tissue-bridging structure to provide a framework for axonal regeneration in the case of optic nerve reconnection or eye transplantation, and ocular drug delivery. Examples of potential arrestive therapies include gene-related treatment modalities to inhibit intraocular neovascularization and to block retinal cell apoptosis. Looking towards the future, this review focuses on how nanoscale tissue engineering can be and is being used to influence that local environment.

System design considerations to improve isoplanatism for adaptive optics retinal imaging

Adaptive optics (AO) retinal images are limited by anisoplanatism; wavefront shape varies across the field of view such that only a limited area can achieve diffraction-limited image quality at one time. We explored three alternative AO modalities designed to reduce this effect, drawn from work in astronomy. Optical design analysis and computer modeling was undertaken to predict the benefit of each modality for various schematic eyes and various complexities of the imaging system. Off-axis performance was found to be limited by system parameters and not by the eye itself, due to the inherent off-axis characteristics of the eye's gradient index lens. This rendered the alternative AO modalities ineffectual compared with conventional AO but did suggest several methods by which anisoplanatism may be reduced by altering the design of conventional AO systems. Several of these design possibilities were explored with further modeling. The best-performing method involved the replacement of system lenses with gradient index versions inspired by the human eye lens. Mirror-based relay optics also demonstrated good off-axis performance, but their advantage was lost in regions of the system suffering from uncorrected higher-order aberration. Incorporating "off-the-plane" beam deviations ameliorated this loss substantially. In this work we also show, to our knowledge for the first time, that the ideal location of a single AO corrector need not lie in the pupil plane.

A ‘cost‐per‐wear’ model based on contact lens replacement frequency

Purpose: The aim was to construct and advise on the use of a cost‐per‐wear model based on contact lens replacement frequency, to form an equitable basis for cost comparison.Methods: The annual cost of professional fees, contact lenses and solutions when wearing daily, two‐weekly and monthly replacement contact lenses is determined in the context of the Australian market for spherical, toric and multifocal prescription types. This annual cost is divided by the number of times lenses are worn per year, resulting in a ‘cost‐per‐wear’. The model is presented graphically as the cost‐per‐wear versus the number of times lenses are worn each week for daily replacement and reusable (two‐weekly and monthly replacement) lenses.Results: The cost‐per‐wear for two‐weekly and monthly replacement spherical lenses is almost identical but decreases with increasing frequency of wear. The cost‐per‐wear of daily replacement spherical lenses is lower than for reusable spherical lenses, when worn from one to four days per week but higher when worn six or seven days per week. The point at which the cost‐per‐wear is virtually the same for all three spherical lens replacement frequencies (approximately AUD$3.00) is five days of lens wear per week. A similar but upwardly displaced (higher cost) pattern is observed for toric lenses, with the cross‐over point occurring between three and four days of wear per week (AUD$4.80). Multifocal lenses have the highest price, with cross‐over points for daily versus two‐weekly replacement lenses at between four and five days of wear per week (AUD$5.00) and for daily versus monthly replacement lenses at three days per week (AUD$5.50).Conclusions: This cost‐per‐wear model can be used to assist practitioners and patients in making an informed decision in relation to the cost of contact lens wear as one of many considerations that must be taken into account when deciding on the most suitable lens replacement modality.

Trends in Australian contact lens prescribing during the first decade of the 21st Century (2000–2009)

Purpose: The aim was to document contact lens prescribing trends in Australia between 2000 and 2009.Methods: A survey of contact lens prescribing trends was conducted each year between 2000 and 2009. Australian optometrists were asked to provide information relating to 10 consecutive contact lens fittings between January and March each year.Results: Over the 10‐year survey period, 1,462 practitioners returned survey forms representing a total of 13,721 contact lens fittings. The mean age (± SD) of lens wearers was 33.2 ± 13.6-years and 65 per cent were female. Between 2006 and 2009, rigid lens new fittings decreased from 18 to one per cent. Low water content lenses reduced from 11.5 to 3.2 per cent of soft lens fittings between 2000 and 2008. Between 2005 and 2009, toric lenses and multifocal lenses represented 26 and eight per cent, respectively, of all soft lenses fitted. Daily disposable, one‐ to two‐week replacement and monthly replacement lenses accounted for 11.6, 30.0 and 46.5 per cent of all soft lens fittings over the survey period, respectively. The proportion of new soft fittings and refittings prescribed as extended wear has generally declined throughout the past decade. Multi‐purpose lens care solutions dominate the market. Rigid lenses and monthly replacement soft lenses are predominantly worn on a full‐time basis, whereas daily disposable soft lenses are mainly worn part‐time.Conclusions: This survey indicates that technological advances, such as the development of new lens materials, manufacturing methods and lens designs, and the availability of various lens replacement options, have had a significant impact on the contact lens market during the first decade of the 21st Century.

Outcomes of Iris-Claw Anterior Chamber versus Iris-Fixated Foldable Intraocular Lens in Subluxated Lens Secondary to Marfan Syndrome

To compare the outcome of phacoemulsification using 2 different iris-fixation techniques for intraocular lens (IOL) replacement, a foldable posterior chamber IOL (PCIOL; AcrySof MA60AC, Alcon Laboratories Inc, Fort Worth, TX) and an iris-claw anterior chamber IOL (ACIOL; Artisan, Ophtec BV), for treatment of subluxated lenses in patients with Marfan syndrome (MFS). Randomized, controlled trial. A total of 31 eyes of 16 patients with subluxated lenses associated with MFS and a preoperative corrected visual acuity (CVA) < or =20/40 based on the Early Treatment Diabetic Retinopathy Study chart. Patients were enrolled and the eye with worse visual acuity was randomly assigned to 1 of 2 study arms: phacoemulsification and iris-fixated PCIOL or phacoemulsification and iris-claw ACIOL; the second eye of the same patient received the other IOL type. Preoperative and postoperative ophthalmologic examination, optical coherence tomography, and endothelial cell counts were performed. We recorded CVA results at 3, 6, and 12 months, complications, endothelial cell loss, and central retinal thickness. In the iris-fixated PCIOL group, CVA was significantly improved at 3 (P = 0.011; n = 16), 6 (P = 0.006; n = 16), and 12 months (P = 0.002; n = 16). In the iris-claw ACIOL group, CVA was significantly improved at 3 (P = 0.001; n=15), 6 (P = 0.001; n = 15), and 12 months (P = 0.009; n = 12). The CVA results did not differ significantly between groups. Dislocation of the IOL occurred in 3 of 16 (18.75%) eyes in the PCIOL group. Retinal detachment occurred in 3 eyes (2 in the PCIOL group and 1 in the ACIOL group) and was successfully repaired. Postoperative foveal tomograms in both groups revealed a decrease in the mean foveal thickness (MFT; < or =172 microm) in 54.16% of the patients. The iris-sutured PCIOL and iris-claw ACIOL produced comparable improvements in CVA at 3, 6, and 12 months postoperatively. Although IOL dislocation tended to occur more frequently in the iris-fixated PCIOL group, the difference was not significant. At 6 months postoperatively, all study patients tended to have a thinner MFT. None of the patients in either group developed cystoid macular edema.

Alternaria and Paecilomyces Keratitis Associated With Soft Contact Lens Wear

To report a series of 5 patients with soft contact lens (SCL) related fungal keratitis caused by unusual organisms diagnosed at the Wills Eye Institute, Cornea Service in 2008. Chart review of patients with SCL related Alternaria and Paecilomyces keratitis diagnosed in 2008 was performed. Causes of these fungal infections were compared to previous years. During a period from 1999 to 2007, among 64 patients with fungal keratitis, Alternaria was isolated from one case after corneal foreign body removal in 2004, and Paecilomyces was not isolated in any of these patients. In 2008, however, 5 patients with SCL-related atypical fungal keratitis were diagnosed. Alternaria was isolated from 2 cases and Paecilomyces from 3 cases. All patients wore Acuvue SCL (Johnson & Johnson Vision Care): Acuvue Oasys, Acuvue Advance, and Acuvue 2 (1 case each) and Acuvue unspecified (2 cases). A total of 2 patients with Alternaria and 1 patient with Paecilomyces used ReNu or a generic-brand solution manufactured by Bausch & Lomb; 2 with Paecilomyces keratitis used Opti-free Replenish solution. A total of 3 patients wore lenses for daily wear and 2 wore them occasionally for overnight wear. The patients were treated with either voriconazole drops alone or combined with voriconazole 200 mg pills or Natamycin 5% drops. Three patients responded well to treatment. One patient with Paecilomyces keratitis developed a corneal perforation managed with tissue adhesive. One Paecilomyces keratitis patient required an emergency penetrating keratoplasty because of a perforated corneal ulcer present at the initial examination. We report 2 cases of Alternaria and 3 cases of Paecilomyces keratitis in patients wearing frequent replacement lenses and using multipurpose solutions diagnosed during 2008. We want to raise awareness of fungal keratitis caused by unusual organisms associated with SCL wear.

Clinical Outcomes of Complex and Uncomplicated Cataractous Eyes After Lens Replacement with the AcrySof Toric IOL

to compare outcomes for uncomplicated versus complex eyes after implantation of AcrySof toric intraocular lenses (IOLs) (Alcon Laboratories Inc) in a retrospective series of cataractous astigmatic eyes. toric IOLs were implanted in 230 eyes of 162 adult patients. Approximately half (52%, n=120) the eyes had no complications (uncomplicated group). The other 110 (48%) eyes (complex group) had a variety of complexities, including retinal or macular problems (eg, age-related macular degeneration), angle or pressure problems (eg, glaucoma), or high astigmatism that required adjunctive limbal relaxing incisions (LRIs). Outcomes were retrospectively assessed approximately 6 weeks after surgery. preoperative corneal astigmatism was 1.60 ± 1.20 diopters (D) overall (1.40 ± 0.70 D in the uncomplicated group and 1.90 ± 1.60 D in the complex group). Residual cylinder was 0.40 ± 0.60 D overall (P<.01 compared to baseline) and was significantly lower (P<.01) for the uncomplicated group (0.30 ± 0.40 D) than for the complex group (0.50 ± 0.80 D), which contained the adjunctive LRI subgroup (residual cylinder 0.80 ± 0.70 D). A larger percentage of uncomplicated eyes (26%) than complex eyes (16%) had at least 20/20 uncorrected distance visual acuity (UDVA) (P=.05). Excluding eyes with intentionally targeted myopic postoperative spherical equivalent, no eyes lost Snellen lines of UDVA, and the average improvement in UDVA was 0.8 ± 0.6 logMAR. Corrected distance visual acuity of the retinal/macular subgroup was poorer than the uncomplicated group pre- and postoperatively but was significantly improved by the surgery (P<.001; average improvement approximately 3 Snellen lines). AcrySof toric IOLs reduced cylinder and improved UDVA in both complex and uncomplicated eyes with cataractous astigmatism.

Compliance with Contact Lens Replacement in Canada and the United States

To assess eye care practitioners (ECPs) recommendations for replacement frequency (RF) of silicone hydrogel (SH) and daily disposable (DD) lenses in Canada and the U.S. and to compare noncompliance (NC) with manufacturer recommended RF by the ECP and patient, and the reasons given for NC. Invitations to participate were sent by e-mail to ECPs in Canada and the U.S. Twenty patient surveys were sent to 420 ECPs, and 2232 eligible surveys were received from 216 ECPs (26% Canada, 74% U.S.). Questions related to patient demographics, lens type, wearing patterns, ECP instructions for RF, and actual patient RF. ECPs provided lens information and their recommendation for RF after the surveys were completed and sealed in envelopes. Responses were anonymous. DD accounted for 18% (Canada) vs. 16% (U.S.) of wearers (p > 0.05); 35% (Canada) vs. 45% (U.S.) wore 2-week replacement SH (2WR; p = 0.011); and 47% (Canada) vs. 39% (U.S.) wore 1-month replacement SH (1MR) lenses (p = 0.025). Thirty-four percent (Canada) vs. 18% (U.S.) of ECPs recommended longer RFs than the manufacturer recommended RF for 2WR lens wearers (p < 0.001); 6% (Canada) vs. 4% (U.S.) for DD wearers; and 2% (Canada) vs. 1% (U.S.) for 1MR lens wearers. NC rates for actual RFs reported by patients were not different between countries (p > 0.05) and were lowest for DD (13% Canada, 12% U.S.), followed by 1MR (33% Canada, 28% U.S.). The highest NC rates were with 2WR (50% Canada, 52% U.S.). The most frequent reason for NC with 2WR and 1MR was "forgetting which day to replace lenses" (54% Canada, 53% U.S.) and in DD wearers "to save money" (56% Canada, 29% U.S., p < 0.001). 1MR lenses are more frequently prescribed in Canada. ECPs in Canada were NC with 2WR lenses more frequently than U.S. ECPs, but patient NC rates were the same in both countries for all lens types. ECP and patient NC rates were highest for 2WR lens wearers.

Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement in Canada

Purpose: To assess current recommendations by optometrists for replacement frequency (RF) of silicone hydrogels (SH) and daily disposable (DD) contact lenses in Canada, determine rates of non-compliance with recommendations by both the optometrist and patient, and investigate reasons for non-compliance.&#x0D; Methods: Survey packages were sent to optometrists in Canada who had agreed to participate. Patients completed survey questions regarding demographics and contact lens wearing patterns, including recommended and actual contact lens RF. Optometrists were asked to provide lens information and their recommendation for RF. Fifty-eight optometrists returned 654 surveys, of which 578 were eligible for analysis.&#x0D; Results: Seventy percent of patients were female with a median age of 32 years. Lens type distribution was 18% DD, 35% two-week SH, and 47% one-month SH. Six percent were worn for extended wear. Daily wear median wearing time was 12 hours/day, a median of five days/week for DD, seven days/week for SH (two-week and one-month). Optometrists’ recommendations were non-compliant with the manufacturers’ recommended RF for 6% of DD, 35% of two week, and 2% of one-month patients. Patients were non-compliant with recommendations from both the manufacturer and optometrist for 12% of DD, 43% of two-week, and 31% of one-month lens wearers. The most common reason for non-compliance was forgetting which day to replace lenses. Fifty-six percent thought a reminder system would help with compliance. A higher proportion of compliant patients followed the RF because of confidence in their optometrist.&#x0D; Conclusions: Optometrists generally recommended RFs consistent with manufacturers’ recommendations for DD and one-month SH lenses but often recommended longer intervals for two-week SH lenses. Patients were most compliant when wearing DD lenses and least compliant when wearing two-week SH lenses. Communication between the patient and optometrists concerning the risks of non-compliance, or initiating a reminder system might improve compliance.

Patient and Practitioner Compliance With Silicone Hydrogel and Daily Disposable Lens Replacement in the United States

The objectives of this study were to assess current recommendations for replacement frequency (RF) of silicone hydrogel (SH) and daily disposable (DD) lenses, to determine compliance with these recommendations, and to investigate the reasons given for noncompliance. A package containing 20 patient surveys was sent to 309 eye care practitioners (ECPs) in the United States who had agreed to participate in the study. One thousand eight hundred fifty-nine completed surveys were received from 158 ECPs and 1,654 surveys were eligible for analysis. Questions related to patient demographics, lens type, lens wearing patterns, the ECP instructions for RF, and the actual patient reported RF. ECPs were asked to provide lens information and their recommendation for RF after the surveys had been completed and sealed in envelopes. All responses were anonymous. Sixty-six percent of patients were women and their mean age was 34 +/- 12 years. Eighty-eight percent of lenses were worn for daily wear, 12.8 +/- 3.2 hours a day, 6.2 +/- 1.5 days a week. Lens type distribution was 16% DD, 45% 2 week (2W) SH, and 39% 1 month (1M) SH. ECP recommendations for RF varied according to the lens type; 1% of 1M (95% CI 0.2-1.7), 4% of DD (95% CI 2.1-7.2), and 18% of 2W (95% CI 15.1-20.7) patients were given instructions that did not conform to the manufacturers' recommended RF (MRRF). When considering only those patients who were given the correct instructions for RF, 38% were not compliant with the MRRF; noncompliance rates varied according to the lens type and were 12% for DD (95% CI 8.6-17.2), 28% for 1M (95% CI 24.9-32.1), and 52% for 2W (95% CI 47.8-55.8). The most frequent reasons for over wearing lenses were "forgetting which day to replace lenses" (51%) and "to save money" (26%). Fifty-three percent believed that a reminder system would aid compliance; the most popular methods being a cell phone reminder or text message (29%) and a nominated day each week or month (26%). Discussions between the ECPs and the patients were more extensive for patients who were compliant with the MRRF. ECPs recommended RFs more frequently with DD and 1M SH lenses than with 2W SH lenses, consistent with manufacturers' recommendations. Patients were less compliant with RF than ECPs for all lens types investigated. Patients were most compliant with RF when wearing DD lenses and least compliant when wearing 2W SH lenses. Better communication facilitated greater compliance with RF. More than half of those not replacing lenses, when recommended, reported that this was because they forgot which day to replace their lenses.

Comparison of capsular opacification and refractive status after placement of three different intraocular lens implants following phacoemulsification and aspiration of cataracts in dogs

To evaluate the effect of lens design and biomaterial on formation of posterior capsular opacification (PCO) and refractive correction. Animals studied Sixty dogs undergoing bilateral phacoemulsification for mature or diabetic cataracts. One randomly selected eye received a rounded edge 41D polymethyl-methacrylate (PMMA) intraocular replacement lens (IOL) and the contralateral eye received either a squared edge 41D hydrophilic acrylic IOL (n = 35) or a squared edge 40D hydrophobic acrylic IOL (n = 25). At the (mean = 79 day) reexamination period, PCO was graded using direct slit-lamp observation and by masked observer evaluation of digital images of the IOLs. Streak retinoscopy and B-mode ultrasound were performed at this period. The PCO score via direct slit-lamp was significantly lower for the hydrophilic acrylic IOL when compared to the PMMA IOL. Masked observer evaluation of digital images revealed that the acrylic IOLs had lower but generally not statistically significant PCO scores than the PMMA IOLs. Streak retinoscopy showed that the PMMA IOL was significantly closer to emmetropia (+0.44 D) when compared to either the hydrophilic acrylic (+0.96 D) or the hydrophobic acrylic (+1.2 D) IOLs. B-mode ultrasonography revealed the center of the hydrophilic acrylic IOL is 0.31 mm closer to the retina and the center of the hydrophobic acrylic IOL is 0.63 mm further from the retina when compared to the center of the PMMA to retina distance. Square edged foldable acrylic IOLs show a predisposition towards generating slightly less PCO than round edged PMMA IOLs in the early postoperative period, however, both acrylic IOLs had greater persistent hyperopia than the PMMA IOLs.

Lentes de contato terapêuticas e as vantagens dos materiais de alto Dk

Therapeutic contact lenses are useful in a variety of ocular surface diseases. Their main indications are: to relieve the pain; protect ocular surface; promote corneal healing and epithelial regeneration; seal a leaking corneal wound and deliver ophthalmic drugs on the ocular surface. There are several kinds of lens designs and materials, and their choice is dependent on the specific disease to be treated, the duration of treatment and the physiologic needs of the diseased cornea. Bullous keratopathy, recurrent epithelial erosion syndrome, dry eye and postoperative epithelial defects are amongst their indications. Therapeutic contact lenses should not be indicated in the presence of active infectious keratitis or when the patient is not compliant. Corneal neovascularization, giant papillary conjunctivitis and infectious keratitis are serious complications, which can be prevented by correctly fitting and maintaining the therapeutic contact lenses. Silicon-hydrogel therapeutic contact lenses, due to their higher oxygen permeability, allow extended wear schedules, decreasing the need for frequent lens replacement.

The Association Between Showering With Contact Lenses And Acanthamoeba keratitis

To review important aspects of contact lens compliance and to survey contact lens replacement frequency, steps in lens care and hygiene and replacement of the lens storage case via online surveys.Random US samples (n = 645 and 787) of frequent replacement contact lens wearers answered questions on contact lens wear in online, sponsor-masked surveys.Wearers of lenses prescribed by their practitioner for 2 weekly replacement reported that they replaced lenses as follows: within 2 weeks 45%, within 3 weeks (minor stretching) 68%, within 4 weeks 89%, ≥8 weeks (extreme stretching) 4%, compared to Monthly wearers who reported: within 4 weeks 37%, within 5 weeks (minor stretching) 57%, ≥8 weeks 23% (≥8 weeks extreme stretching, Chi-square p = 0.001). Median frequency for cleaning lens storage case was 2–3 times per week, while 33% reported cleaning monthly or less often. Median lens storage case replacement was every 4–6 months, while 48% reported annual replacement or less often. Most patients cleaned their lens case with hot or cold tap water (72%).These internet surveys revealed significant non-compliance with lens care steps, case hygiene and lens replacement schedule. More than half of the contact lens wearers surveyed were not compliant with their 2-weekly or monthly schedule. Lenses prescribed for longer replacement intervals can lead to more extreme stretching of lens life. To encourage better patient habits, eye care providers should reinforce their recommended frequency of replacement of lenses and storage cases and should reinforce care and hygiene steps at each patient visit.

Optical quality of the eye after lens replacement with a pseudoaccommodating intraocular lens

To examine the optical quality of healthy presbyopic eyes before and after implantation of the pseudoaccommodating AcrySof ReSTOR Natural intraocular lens (IOL) (Alcon Laboratories) by measuring visual acuity and wavefront aberrations. University of Valencia, Fernández-Vega Ophthalmological Institute, Valencia, Spain. Monocular refraction and photopic distance (6 m) and near (0.33 m) visual acuities were determined before and after clear lens extraction with bilateral AcrySof ReSTOR Natural IOL implantation in 30 hyperopic eyes (+0.50 to +4.00 diopters [D]) of presbyopic patients with low astigmatism (< or = 1.00 D). Postsurgical binocular visual acuity was measured over a range of effective distances. Wavefront aberrations were measured before and after surgery. Aberrations for 2 pupil diameters (3.0 mm and 5.0 mm) were decomposed using Zernike polynomials; total, defocus, astigmatism spherical, and coma aberration terms were studied separately. Postimplantation results were compared with preoperative values. Safety and efficacy indices for distance vision were 1.01 and 0.96, respectively. At near, they improved to 1.07 and 1.06, respectively. Vision at intermediate distances was noticeably poorer. Total, defocus, and spherical aberrations changed after IOL implantation with both pupil diameters (P<.01). Total and defocus aberrations were significantly reduced postoperatively. Spherical aberration coefficients changed to negative and less positive values for a 3.0 mm and a 5.0 mm pupil, respectively. Implantation of the pseudoaccommodating IOL in healthy eyes yielded uncorrected levels of high-contrast, distance, and near acuities comparable to preoperative best corrected values. Higher-order aberration levels appeared to be similar to the preoperative values.

Medical technology transfer for sustainable development: A case study of intraocular lens replacement to correct cataracts

Cataracts account for almost 50% of blindness in the world (17 million people). The magnitude of this problem is stunning, and affects the sustainable economic progress of developing nations where 90% of the blind are located (and likewise 90% of the $19 billion dollars in lost global productivity each year). The Vision 2020 program has called for eliminating cataract as a cause of avoidable blindness through intraocular lens replacement surgery (IOL surgery), a relatively cheap solution with good outcomes. This paper will: (1) give background on the scope and problems surrounding international technology transfer of IOL surgery; (2) develop the international medical technology transfer framework adapted from work by Lall and Wei; (3) compare programs in the countries of Nepal and Nigeria; (4) evaluate the success of their technology transfer of intraocular lens replacement; and (5) provide recommendations for sustainable international transfer of IOL surgery.

A fitting tale

So wrote this prominent British educator and researcher in his contact lens textbook [ [1] Bier N. Contact Lens Routine and Practice. Butterworths, London1957 Google Scholar ] half a century ago – prior to the introduction of soft lenses, frequent replacement lenses, daily disposability and silicone hydrogels, to name just a few of the developments in the contact lens field since then. Would Bier have been correct if he had made that statement today? Based on the volume of contact lens-related research being undertaken in universities, the current rapid pace of change in the industry, the continuing introduction of new contact lens and lens care products into the market, and the enormous investments still being poured into research and development by the major international contact lens companies, the answer would have to be a resounding “no”! Which brings us to the point of this tale: that there is a need to constantly monitor movements in the marketplace and relate these changes to national and international trends in fitting habits, so that the contact lens industry can be assured that it is introducing appropriate products to serve the prescribing needs of practitioners, and that practitioners are able to meet the visual and lifestyle needs of their patients.