Soft Lenses Research Articles

Adverse Events and Discontinuations With Rigid and Soft Hyper Dk Contact Lenses Used for Continuous Wear

The purpose of this study was to assess the relative clinical success of hypertransmissible rigid and soft contact lenses in terms of the rates of adverse events and clinical discontinuations. One hundred subjects (50 experienced wearers and 50 neophytes) were fitted with either the Z-alpha lens (Menicon) or the Focus Night & Day lens (CIBA Vision), which were worn on a 30-day continuous wear basis. The rates of adverse events and clinical discontinuations were monitored over 12 months. There were 20 adverse events that were categorized as being serious or significant--four with rigid lenses and 16 with soft lenses (p = 0.003). There was no significant difference between the experienced (10) and the neophyte (10) groups (p = 1.00). There were 23 clinical discontinuations--13 with rigid lenses and 10 with soft lenses (p = 0.46). Fewer experienced wearers (five) discontinued than neophytes (18) (p = 0.002). Practitioners should anticipate fewer adverse events with rigid versus soft lenses prescribed for continuous wear. Experienced wearers are less likely to discontinue compared with neophytes.

Advances in Spectacle Free Refractive Corrections

Advances in Spectacle Free Refractive Corrections

Trends in Contact Lens???Related Corneal Ulcers

To analyze the frequency of contact lens-related corneal ulcers and its relationship to the type of contact lens and care. Charts of 376 patients with corneal ulcers seen at the Cornea Service of Wills Eye Hospital from July 1, 1999 to December 31, 2002 were retrospectively reviewed. All patients with contact lens-related corneal ulcers were identified, and information regarding cultures, lens type, usage, and cleaning was obtained. Of the 376 cases, 113 (30%) were related to contact lens use. The contact lens history was recorded in 83 of 113 cases (73%). The soft daily wear frequent replacement lens was the most common lens type associated with corneal ulcers (n = 36/83, 43%). Corneal cultures were performed in 71 of 113 cases (63%) and were positive in 51 of 71 cases (72%). The most common microorganism involved was Pseudomonas aeruginosa (n = 17/51, 33%). The frequency of contact lens-related corneal ulcers from 1999-2002 (n = 113/376, 30%) was significantly greater than that from years 1996-1999 (n = 37/299, 12%) at our institution (P < 0.05). There was a significant increase in the number of contact lens-related corneal ulcers between 1999 and 2002 compared with previous years (P < 0.05). The contact lens type most frequently associated with corneal ulcers was the soft daily-wear frequent-replacement contact lens (43%). Contact lens-related corneal ulcers continue to be a serious problem despite a shift in the market to the use of frequent-replacement daily-wear contact lenses and advances in contact lens technology.

Long-Term Changes in Corneal Endothelial Morphology After Discontinuation of Low Gas-Permeable Contact Lens Wear

Low gas-permeable contact lens wear of polymethyl methacrylate or hydroxyethyl methacrylate material is known to cause morphologic abnormalities in the corneal endothelial cell layer. These lenses were widely prescribed and successfully worn until their use was actively discouraged in the late 1980s and early 1990s. This study was designed to investigate whether discontinuation of low gas-permeable contact lens wear leads to an improvement of corneal endothelial cell morphology. At the time of discontinuation and at least 5 years after discontinuation of low gas-permeable contact lens wear, noncontact specular photographs of the central corneal endothelium were made in 66 patients (14 male and 52 female, mean age 37.7 +/- 8.4, range 24.6-69.0). By computer analysis of endothelial photographs, parameters for polymegethism and pleomorphism were calculated, as well as cell density. Mean follow-up time between photographs was 6.8 years (SD 1.1). Sixty-one patients were refitted with rigid high gas-permeable contact lenses or high-water-content soft lenses, and 5 patients switched to spectacle wear. A small but significant recovery of the corneal endothelial cell morphology was found for the mean coefficient of variation of cell area, from 37.5 to 35.7 (P = 0.022), and for the coefficient of variation of the number of sides, from 13.1 to 12.4 (P = 0.004). The mean percentage of hexagonal cells increased from 54.2 to 56.2 (P = 0.013). Although the corneal endothelial cell morphology improved significantly on cessation of LGP contact lens wear, the values did not return to levels observed in normal, non-contact lens wearing individuals. During follow-up, the mean endothelial cell density decreased significantly (P = 0.001) from 2994 to 2890 (a 3.5% cell loss in 6.8 years), which is similar to the known normal age-related cell loss of 0.6% per year in non-contact lens wearing healthy individuals. Endothelial polymegethism and pleomorphism caused by PMMA or HEMA contact lens wear is partly reversible.

Intraoperative complications during phacoemulsification in myopic eyes

Background: To assess the incidence of intraoperative complications during phacoemulsification in myopic eyes such as rupture of posterior capsule, vitreous loss, intraoperative haemorrhage and posterior dislocation of nucleus. Methods: In this retrospective study we analyzed medical records of all cataract operations between January 1, 2003 and December 31, 2003 at the Department of Ophthalmology, General Hospital Maribor. We treated 52 myopic eyes from 40 patients with axial length more than 24.5 mm. Exclusions criteria were other ocular pathology, preceding ocular operation, combined operation of cataract and glaucoma and serious systemic disease. Standard phacoemulsification was done with clear cornea cut and soft foldable intraocular lens (IOL) was implanted in the capsular bag. Results: In 52 operated eyes none of the observed complications occurred. Conclusions: Phacoemulsification in myopic eyes without any previous pathology is a safe surgical procedure.

Corneal Oxygen Deficiency

To compare the ocular effects of low Dk hydrogel and high Dk silicone hydrogel contact lenses. A review of recent literature was conducted to determine the effects of wearing low and high Dk soft lenses on corneal swelling, vascular response, refractive error and the corneal epithelium. High Dk silicone hydrogel contact lenses became available for research and clinical practice almost 10 and 5 years ago respectively. During that time many studies have been conducted and it has been demonstrated repeatedly how much improvement there has been to the physiological response of the eye particularly when wearing the lenses on an overnight basis. Although silicone hydrogels only constitute about 2% of current wearers, their positive effects on the eye compared with low Dk hydrogel lenses should make them the most dominant lenses in the near future.

Cytotoxicity Evaluation of Soft Contact Lens Care Solutions on Human Conjunctival Fibroblasts

Purpose: To determine whether different contact lens care solutions for soft lenses cause damage to human conjunctival cells. Methods: Primary cultured human conjunctival fibroblasts were incubated with various concentrations of four different commercially available soft contact lens care solutions (OptiFree^®, Renu^®, SoloCare^®, Titmus^®) at concentrations of 5, 10 and 50 µl/ml medium. Toxicity was examined by determination of (1) the cell viability and mitochondrial activity with the colorimetric MTT test, and (2) the number of living cells with a cell analysis system (CASY 1) as compared with untreated cells. Results: For all four soft contact lens care solutions at a concentration of 5 µl/ml medium, no significant decrease in mitochondrial activity of the human conjunctival fibroblasts was found by the MTT test. At 10 µl/ml, only OptiFree and Titmus reduced mitochondrial viability significantly. The greatest reduction in mitochondrial activity occurred with all of the four soft contact lens care solutions at a concentration of 50 µl/ml. No significant decrease in the number of living conjunctival fibroblasts was observed by CASY 1 even at higher concentrations of the four solutions investigated. Conclusion: This in vitro study demonstrates that the examined soft contact lens care solutions induce changes in mitochondria of human conjunctival cells only at higher doses as observed by the MTT test. However, this damage to the mitochondria did not lead to cell death as shown by the cell analysis system.

Assessment of capsular block syndrome with anterior segment optical coherence tomography

A 59-year-old woman developed progressive, moderate myopia 1 year after routine phacoemulsification and insertion of a soft posterior chamber intraocular lens (IOL). After biomicroscopy, late capsular block was diagnosed and treated with a neodymium:YAG laser posterior capsulotomy. The myopia disappeared immediately. This case was illustrated using optical coherence tomography developed for the anterior segment. After capsulotomy, the IOL moved backward by 448 μm, corresponding to –0.75 diopter of induced myopia.

Water properties of soft contact lens materials

The properties of water in soft contact lenses such as the water content, free-to-bound water ratio, and the extent to which soft lenses dehydrate during wear, are key determinants of their in eye performance and oxygen transmissibility characteristics. This study describes clinical and laboratory experiments that were conducted in order to examine the state of water in eight soft contact lenses manufactured from different materials. Specifically, lenses made from the following eight materials (and nominal water contents) were used: HEMA/VP 40%, HEMA/VP 55%, HEMA/VP 70%, VP/MMA 55%, VP/MMA 70%, HEMA 40%, HEMA/MAA 55% and HEMA/MAA 70% [HEMA = 2-hydroxy-ethyl methacrylate, VP = vinyl pyrrolidone, MMA = methyl methacrylate, MAA = methacrylic acid]. Differential scanning calorimetry (DSC) was used for measuring the free water content in the materials listed above. Some noticeable differences in water properties among soft contact lens materials having approximately the same water contents were revealed. Low water content materials exhibited a simple endotherm and all water melted around 0 °C. On the other hand, medium and high water content materials exhibited multiple melting endotherms, representing a broad range of interactions between water and the polymer. Low water content soft contact lenses have approximately the same amount of bound water as those with much higher water contents. Six subjects were then fitted with the same lenses for one day. In vitro measurements of water content and oxygen transmissibility were taken at 35 °C, both before lens fitting and after 6 h of lens wear. Water content and oxygen transmissibility were correlated with the water properties of the soft contact lens materials. The relative change in lens water content (%ΔWC) and relative change in lens oxygen transmissibility (%ΔDk/ t) were calculated and correlated with the water properties of the eight soft contact lens materials. It was concluded that (a) oxygen transmissibility, free water content and free-to-bound water ratio are increased when the water content of a contact lens is increased and (b) water content, free water content and free-to-bound water ratio cannot be used for the prediction of soft contact lens dehydration in vivo.

Overnight Corneal Reshaping Versus Soft Daily Wear

To evaluate patients' perceptions of visual quality of life differences in a crossover study with two different modes of contact lens wear: overnight corneal reshaping (OCR) lenses and daily-wear soft lenses. Qualified subjects wore one mode of contact lens for 8 weeks and then completed the National Eye Institute RQL-42 questionnaire. After a washout period, subjects wore the alternate mode for 8 weeks followed by the questionnaire. During soft lens mode, subjects wore lenses during their waking hours. During the overnight corneal reshaping mode, subjects wore lenses only while sleeping. Soft lenses were Biomedics 55 2-week disposable lenses. OCR lenses were Corneal Refractive Therapy (CRT) lenses by Paragon. Subjects were randomly assigned to wear soft contact lenses or OCR lens first. After completing both phases of the study, patients were asked to choose which mode they preferred. Interim results show that of 74 subjects enrolled, 45 have completed both phases; 14 have dropped out of the study; and 15 are still in process. Of the 45 subjects completing both phases, 32 have chosen to continue with the CRT lenses, and 13 have chosen to stay with the soft lenses. Logarithm of the minimum angle of resolution visual acuity was 0.06 (20/20) for soft contact lenses and 0.11 (20/25) for CRT lenses. RQL-42 scoring for overall satisfaction was 81.33 for OCR lenses and 74.67 for soft lenses. Although overall satisfaction scores and vision were comparable between the two modes, 71% of the subjects elected to stay with CRT lenses. In this study of patients who experienced both modes of lens wear, 71% chose OCR lenses.

Contact Lens Complications

Hans-Walter Roth Contact Lens Complications, Etiology, Pathogenesis, Prevention, Therapy 214 pages Georg Thieme Verlag, Stuttgart, New York, 2003 ISBN 1 58890 132 7 Price: $119.00 This book is an authorized translation of the German edition published in 2002. It is composed of 10 chapters concerning different aspects of the various complications associated with contact lens wear, and contains 476 illustrations, 466 of which are in colour. The bulk of the text concerns clinical descriptions and illustrations of most pathological findings in complications related to contact lens wear. The complications are classified according to anatomical position and each location begins with a short description of its anatomy and physiology. Thereafter, the different conditions are presented in terms of symptoms, clinical findings, differential diagnosis and prophylaxis. A separate chapter related to the clinical location describes the treatment for each type of condition. This clear and mainly regional method of presentation makes it easy for the ophthalmologist to access information on specific types of contact lens problems. Other chapters describe patient counselling and examination, fitting and wearing problems, and eye injuries in contact lens wearers. These chapters are marked by the author's experience in a university eye clinic attended by patients with many types of eye disease and are not necessarily representative of the experience of the majority of normal contact lens wearers. For example, the author states that despite recent advances in soft lens technology, hard lenses are still better tolerated in the longterm. I think it will be difficult to convince the general contact lens wearer of this! The book contains over five pages of references. Unfortunately these references are not related to specific statements in the text. Otherwise it could be desirable with a reference, which for instance documented the benefits of the proposed 3–6 month interval between follow-up examinations of adults wearing soft lenses. The frequency of contact lens complications is described as being between 1% and 30%. The author emphasizes that such figures are mostly based on reports that fail to state either the composition of their patient populations or the length of wearing time. Furthermore, in my opinion it is also important to distinguish between the frequencies of mild and severe complications. It is interesting that in the author's experience, 60% of contact lens complications are caused by faulty handling, cleaning or disinfection. This is important to mention in patient counselling. In conclusion, this book contains much useful information presented in a clear and short text complemented by many good illustrations. It represents excellent reference material for any ophthalmologist confronted with complications arising from contact lens wear.

Pseudomonas aeruginosa Corneal Binding After 24-Hour Orthokeratology Lens Wear

To examine the effect of short-term 24-hr orthokeratology lens (OKL) wear on Pseudomonas aeruginosa binding, epithelial surface cell morphology, epithelial sheet thickness, and stromal thickness in a rabbit model. Seventeen New Zealand white rabbits were treated according to the Association for Research in Vision and Ophthalmology Statement for the Use of Animals in Ophthalmic and Vision Research. Partial membranectomy was performed on all rabbits 1 week before the experiments. Baseline values for epithelial and stromal thickness and epithelial surface cell size were determined by in vivo confocal microscopy in one randomly chosen eye (n = 6). One week later, rabbits were fitted in the same eye with a hyper oxygen-transmissible OKL. Twenty-four hours later, confocal microscopy was repeated. The second group of rabbits (n = 6) was fitted with an OKL in one randomly chosen eye for 24 hr. P. aeruginosa binding to the corneal epithelium was assessed for the control corneas and those exposed to the test lens. Scanning electron microscopy was performed on a third group of rabbits to assess epithelial surface damage (n = 5). There was a statistically significant difference (P<0.001) in P. aeruginosa binding between the control (1.11 +/- 0.74 x 10(5) colony-forming units per cornea) and the OKL-wearing eyes (2.74 +/- 0.69 x 10(5) colony-forming units per cornea). The central epithelium thinned by 6.5% after lens wear (48.2 +/- 1.9 microm to 45 +/- 1.7 microm, P=0.005); however, central stromal thickness increased by 7.3% (322 +/- 22 microm to 345 +/- 29 microm, P=0.006). Compared with the baseline value, central epithelial cell size increased significantly from 1,253 +/- 140 mm(2) to 1,627 +/- 393 mm(2) (29.4%, P=0.02). Scanning electron microscopy showed increased surface epithelial damage associated with OKL wear. This prospective, masked, pilot study showed that 24-hr hyper oxygen-transmissible OKL wear induced a statistically significant increase in P. aeruginosa binding to the epithelium of the rabbit cornea, accompanied by central epithelial thinning, stromal thickening, and surface cell damage assessed by scanning electron microscopy. Collectively, the data suggest that despite adequate lens oxygen transmissibility, the mechanical pressure inherent in the OKL design exerted on the corneal surface appears to be associated with increased adherence of P. aeruginosa to surface corneal epithelial cells, which may pose an increased risk for lens-related microbial keratitis, especially in overnight (i.e., closed-eye) wearing conditions. Future studies are needed to determine whether these results are similar in human wear and how P. aeruginosa binding during OKL wear compares with other lens-wearing modalities, such as daily or continuous soft lens wear.

Cataract surgery with the AlphaCor artificial cornea

Purpose: To review the outcomes of AlphaCor artificial cornea (Argus Biomedical Pty Ltd.) implantation concurrent with or subsequent to cataract surgery. Setting: Nonrandomized multicenter clinical trial. Methods: AlphaCor devices were implanted under an approved protocol. Extracapsular cataract extraction with intraocular lens implantation was concurrently performed in 5 cases; an additional case had a displaced cataractous lens removed after severe blunt trauma subsequent to AlphaCor implantation. Results: Cataract surgery was difficult because the view was restricted and residual soft lens matter was retained. There was an increased incidence of postoperative complications (eg, melt, glaucoma) in cataract cases compared with noncataract AlphaCor cases. The mean best corrected visual acuity was worse in cases with cataract than in cases without. Conclusions: The technique for cataract surgery in AlphaCor cases needs to be refined. Imaging studies performed postoperatively may help ascertain whether soft lens matter remains so additional antiinflammatory medication can be considered. Melting appears to be preventable by topical medroxyprogesterone 1% therapy.

Confocal microscopy of the corneas of long-term rigid contact lens wearers

<h2>Abstract</h2> Slit scanning confocal microscopy (Tomey Confoscan P4) was used to evaluate the central cornea of 22 subjects who had been wearing rigid lenses on a long-term, daily wear basis. Anterior and posterior keratocyte densities appeared unaffected by rigid lens wear (<i>P</i>=0.10 and 0.34 for anterior and posterior keratocyte densities, respectively). Subjects with a previous history of polymethyl methacrylate (PMMA) lens wear showed a reduction in anterior keratocyte density (AKD) (<i>P</i><0.0001) and an increased level of haze in the anterior stroma. This may represent previous hypoxic damage. Endothelial cell density (ECD) was unaffected by rigid lens wear (<i>P</i>=0.36) although an increase in endothelial polymegethism was evident (<i>P</i><0.0001). Subjects who had only worn rigid lenses with no history of PMMA lens wear did not show an increase in endothelial polymegethism (<i>P</i>=0.10). An increased number of microdot opacities compared to the non-lens wearing eye was apparent (<i>P</i>=0.05). The number of microdot opacities induced by rigid lenses, as reported in this study, appears to be less than that reported by others in respect of soft lenses.

Unusual presentation of angle-closure glaucoma treated by phacoemulsification

We report the case of a 70-year-old woman with a history of acute primary angle-closure glaucoma (PACG) in the left eye who, 2 hours after a fundus examination and mydriasis, experienced acutely elevated intraocular pressure (IOP) up to 40 mm Hg in the presence of fully dilated pupil and a patent iridotomy. Gonioscopy revealed appositional angle closure in 3 quadrants. After medical control of the IOP, sutureless cataract surgery was performed, including clear corneal incision, phacoemulsification, and soft acrylic posterior chamber intraocular lens (IOL) implantation. Eighteen months after the operation, improvement of visual acuity, widening of anterior chamber angle, and deepening of anterior chamber depth were found. Intraocular pressures are now normal without medication, even after mydriasis. Modern cataract surgery is an effective treatment for selected patients with appositional angle closure and IOP elevation after acute PACG.

Prevalence of corneal ulcer among contact lens wearers in Nigeria

Corneal Ulceration has been described as the most serious complication of contact lens wear worldwide. The incidence of corneal ulceration in contact lens wearers in Nigeria was determined retrospectively. 1759 case notes of patients who had worn contact lenses for at least one year were obtained from eye clinics in Lagos, Abuja and Port Harcourt. The incidence of corneal ulcer was 1.36 per 100 wearers over the 5-year period (January 1994 –December 1998), with an annual incidence of 0.27 per 100 wearer. Disposable extended wear soft lenses had the highest incidence of 2.94 per 100 closely followed by rigid gas permeable lenses 2.86 per 100. There were no corneal ulcers among conventional daily wear soft lens users. Males showed more cases of corneal ulceration 1.63% than females 1.24% and the age group of 10-19 years had the highest rate of corneal ulcerations (1.66%). It is therefore important for contact lens practitioners to encourage patients to comply with their lens case regimen or switch to daily wear lenses. Key Words: Contact lenses, Corneal ulcers, Lens type, Age. Global Jnl Medical Sciences Vol.2(2) 2003: 127-130

Lentilles de contact et risques infectieux, aspects réglementaires

Contact lens-related infectious keratitis is a potentially sight-threatening complication. Bacterial keratitis, mostly due to Gram-negative bacteria, is associated with poor lens hygiene, overnight wear, and contaminated lens care solutions. Contamination of the lens storage case may cause fungal keratitis. Acanthamoeba infection is related to the use of tap water or swimming while wearing soft lenses. Viruses are of less concern among contact lens wearers. Possible transmission of Creutzfeldt-Jakob disease by multi-patient trial lenses must be taken in account. To minimize these risk factors, regulations are applied at various levels: CE marking of contact lenses and care products as they are medical devices; contact lens fitting only by health care professionals; distribution of contact lenses by opticians and lens care solutions by opticians and pharmacists; hygienic management of trial lenses following official recommendations. Contact lens-related keratitis must be reported to health care Authorities.

Why one million contact lens wearers dropped out

The early 1990s saw a large increase in the number of contact lens wearers in the UK. It is estimated that this figure doubled between 1990 and 1996 to reach approximately three million wearers. The increased uptake of contact lenses during this period is thought to have been due to a number of factors, including the availability of frequent replacement soft lenses, the introduction of daily disposable lenses and the effects of television advertisments [1].

In-eye performance of soft contact lenses made from different materials

The in-eye performance of soft contact lenses may be affected by the material from which they are fabricated and may alter during wear. This study describes clinical and laboratory experiments that were conducted in order to examine the in-eye performance of eight soft contact lenses manufactured from different materials; these materials (and nominal water contents) were: HEMA/VP 40%, HEMA/VP 55%, HEMA/VP 70%, VP/MMA 55%, VP/MMA 70%, HEMA 40%, HEMA/MAA 55% and HEMA/MAA 70% (HEMA: 2-hydroxy-ethyl methacrylate, VP: vinyl pyrrolidone, MMA: methyl methacrylate, MAA: methacrylic acid). Two lenses from each of the eight soft contact lens groups were used in experiments concerning their parameter stability. Six subjects were fitted with lenses for 1 day. Verification of back optic zone radius, total diameter, back vertex power, centre thickness and water content was undertaken at 20 °C. In vitro measurements of total diameter were taken at 35 °C before lens fitting and after 6 h of lens wear. In vivo measurements of lens centration, up-gaze lag, post-blink movement, total diameter and subjective assessment of comfort were taken (a) immediately after lens insertion (1 min), (b) 20 min later and (c) 6 h later (same day). The majority of differences of the in vivo parameters between lens types (with respect to lens centration, lag, movement on blink, lens total diameter and comfort) were not found to be statistically significant throughout the 6 h wearing period. It was also found that lenses increase in diameter when first placed on the eye and decrease in diameter when they were removed from the eye. The information generated in study concerning the in-eye performance of soft contact lens materials may assist the contact lens industry and contact lens practitioners in developing and prescribing soft lenses with optimal performance characteristics.

Confocal microscopy of the corneas of long-term rigid contact lens wearers

Slit scanning confocal microscopy (Tomey Confoscan P4) was used to evaluate the central cornea of 22 subjects who had been wearing rigid lenses on a long-term, daily wear basis. Anterior and posterior keratocyte densities appeared unaffected by rigid lens wear ( P=0.10 and 0.34 for anterior and posterior keratocyte densities, respectively). Subjects with a previous history of polymethyl methacrylate (PMMA) lens wear showed a reduction in anterior keratocyte density (AKD) ( P<0.0001) and an increased level of haze in the anterior stroma. This may represent previous hypoxic damage. Endothelial cell density (ECD) was unaffected by rigid lens wear ( P=0.36) although an increase in endothelial polymegethism was evident ( P<0.0001). Subjects who had only worn rigid lenses with no history of PMMA lens wear did not show an increase in endothelial polymegethism ( P=0.10). An increased number of microdot opacities compared to the non-lens wearing eye was apparent ( P=0.05). The number of microdot opacities induced by rigid lenses, as reported in this study, appears to be less than that reported by others in respect of soft lenses.