Continuous Contact Lens Wear Research Articles

Use of silicone hydrogel contact lenses by Australian optometrists

Background: Prior to the launch of silcone hydrogel (Si‐H) materials in Australia in 1999, only 1.6 per cent of lenses were prescribed on a continuous wear basis. Methods: One thousand surveys were distributed randomly to practitioners in Australia during January 2000, 2001 and 2002 (total surveys 3,000). Each anonymous survey requested data about the next 10 patients fitted with contact lenses, including date, age, gender, new fitting or refitting, lens material type, lens design, frequency of replacement, modality of wear, uses per week and care regimen. Results: Twenty per cent (599) were returned, reporting data on 5,976 fittings. A total of 710 fittings used Si‐H contact lenses (11.9 per cent), which represented 18.6 per cent of all soft lens fittings. During the three years, the proportion of practitioners prescribing Si‐H lenses increased from 42.2 to 52.5 per cent. In 2000, 43.8 per cent were daily wear, which decreased to 32.2 per cent by 2002. The solution system of choice for daily wear lenses was multipurpose solutions (98.4 per cent); the only alternative was hydrogen peroxide systems. Continuous wear represented 11.7 per cent of all fittings, ofwhich 85.7 per cent were Si‐H, 3.0 per cent RGP lenses and 11.3 per cent conventional hydrogels. For continuous wear, 79.0 per cent of fittings were to existing wearers, whereas for daily wear, 59.4 per cent were existing wearers. More males were prescribed Si‐H continuous wear contact lenses, while females were more likely to be prescribed Si‐H on a daily wear basis. Discussion: Si‐H contact lenses were introduced to the Australian market as a continuous wear contact lens, yet many practitioners use this product for daily wear with multipurpose solutions. By 2002, more practitioners were prescribing Si‐H contact lenses for continuous wear than in 2000, suggesting a growing confidence in that product for that mode of wear. A comparison with an earlier survey shows there is an increase in continuous wear from 1.6 per cent to 11.7 per cent over a five‐year period.

Effect of 30-day continuous wear of silicone hydrogel contact lenses on corneal thickness.

To investigate the effect of 30-day continuous-wear contact lenses (Focus Night & Day) on corneal thickness and physiology. Twenty-six myopic eyes with no history of contact lens wear were fitted with silicone hydrogel contact lenses. Complete ophthalmologic examinations, corneal topography, and corneal thickness measurements at the center and eight peripheral areas were performed before fitting and at each visit, namely on day 1, day 10, and 1 month. Mean corneal thicknesses were statistically compared by using one-way repeated-measures analysis of variance. All patients maintained their 20/20 vision with correction. Limbal vascularization was noted in one patient at the end of the study. No patient had subjective complaints. In another patient, a punctate corneal epithelial defect was noted on the 15th day, but it healed when the contact lens was removed for a day. The mean corneal thicknesses in different regions were significantly increased by approximately 14 to 38 microm compared with baseline measurements. There were no significant differences between the corneal topography taken on the first day and the one taken at the end of the first month. All patients maintained their visual acuity. Apart from the limbal vascularization and punctate epithelial corneal defects, which resolved when the contact lens was removed for 1 day, no serious complications were noted. Despite the high oxygen permeability of the monthly Night & Day contact lenses, the mean central and peripheral corneal thicknesses increased. These increases indicate that these lenses may have an effect on corneal metabolism.

Efficacy of continuous wear PureVision contact lenses for therapeutic use

Purpose: To evaluate the Bausch and Lomb PureVision™ contact lens as continuous wear contact lens for therapeutic and medical indications in a prospective open-ended non-randomized trial. Methods: Patients who required therapeutic contact lens wear for various indications such as pain relief, corneal protection, persistent epithelial defects, corneal perforation and chemical burns were fitted with PureVision™ continuous wear contact lenses (balafilcon A, 36% water content). Success or failure of specific treatment indication was assessed in each case with evaluation of ocular and lens related complications. Results: 30 eyes of 28 patients were fitted with PureVision™ continuous wear contact lenses. A successful fit was seen in 27 of 30 eyes with therapeutic success in 26 of 30 eyes. However, all patients reported symptomatic relief. Duration of lens use ranged from 3 days to 3 months. Dry eye was the most frequent cause of contact lens associated therapeutic failure. Complications included lens loss (two eyes), tight lens (one eye) and infective keratitis (two eyes). Conclusions: PureVision™ contact lenses were found to be safe and efficacious for continuous wear therapeutic use to a maximum of 90 days. The contact lens was also easier to handle by virtue of its resilient nature. There were no significant corneal complications of hypoxia, i.e. corneal oedema. Lens losses and deposits were minimal. The lens performance and fitting characteristics compares favorably with previous therapeutic lenses used by the investigators. This new lens may be considered as a safe and effective alternative for use as bandage contact lens.

Therapeutic use of Focus Night & Day contact lenses.

To evaluate the safety and efficacy of Focus Night & Day extended-wear contact lenses when used for therapeutic purposes. Fifty eyes of 50 consecutive patients presenting at the Ankara University Medical Center, Cornea and Contact Lens Service, and requiring bandage contact lens use for ocular surface disorders, were enrolled. All patients were fitted with Focus Night & Day contact lenses and were followed in regard to patient satisfaction, contact lens fit and performance, and success of treatment. Twenty-four patients (48%) were male, and 26 (52%) were female. Average age at the time of presentation was 46.9 +/- 21.6 years (range 1.5 to 88 years). Therapeutic contact lens indications included Fuchs' dystrophy (2 eyes), toxic epitheliopathy (1 eye), filamentous keratopathy (2 eyes), corneal perforation (2 eyes), corneal stromal melting (2 eyes), recurrent corneal erosion (4 eyes), chemical or traumatic epithelial defect (3 eyes), epithelial irregularity (1 eye), persistent epithelial defect (4 eyes), lamellar laceration (5 eyes), graft insufficiency (2 eyes), pseudophakic bullous keratopathy (7 eyes), aphakic bullous keratopathy (4 eyes), disciform keratitis (1 eye), postkeratectomy (4 eyes), and post-amniotic membrane transplantation or post-limbal autograft transplantation (6 eyes). Mean duration of continuous contact lens wear was 2.4 +/- 3.0 months (range 3 days to 12 months). At the end of the follow-up period, the mean change in visual acuity was a gain of 1.8 +/- 2.8 logMAR units (0-9 Snellen lines). No sight-threatening complications related to contact lens wear were encountered. A culture-negative sterile corneal infiltrate developed in one patient and was treated with cessation of lens wear and subsequent topical antibiotic and steroids. Focus Night & Day contact lenses are safe and effective when used for therapeutic purposes. Infrequent replacement of these lenses seems to be especially advantageous in patients for whom frequent lens insertion and removal may be associated with epithelial trauma, pain, and a potential increase in infection risk. Infrequent replacement of these lenses also decreased the office time and the cost of treatment without an increase in hypoxia-related complications.

Changes in corneal structure with continuous wear of high-Dk soft contact lenses: a pilot study.

Despite numerous studies that have considered the effects of extended wear of high-Dk soft contact lenses on ocular physiology, little attention has been paid to the impact of such lenses on central or peripheral corneal thickness and curvature. The present study aims to report the time course of changes in corneal thickness and curvature that accompanies the 30-night continuous wear of new silicone hydrogel soft contact lenses in a neophyte population in a longitudinal study. Six subjects wore high-Dk lotrafilcon (Dk = 140) on a 30-night replacement schedule for 12 months. Only measurements from the right eye were considered for analysis. Topographical measurements of corneal thickness and curvature were taken. The same parameters were monitored for an additional period of 3 months after lens removal. An almost homogenous increase in corneal radius of curvature was detected for all the locations studied, being statistically significant for the 4-mm cord diameter area. This effect was associated with a progressive thinning effect for the central cornea, whereas midperipheral and peripheral areas did not display such a thinning effect during continuous wear. These effects were still evident for the central cornea 3 months after contact lens wear discontinuation. Continuous wear of high-Dk silicone hydrogel contact lenses is associated with clinically appreciable changes in topographical corneal curvature, whereas only a reduction in corneal thickness is appreciated in the central area. This effect seems to be a result of mechanical pressure induced by these hybrid hyperpermeable materials, characterized by a higher modulus of elasticity. The small sample size compromises the conclusions addressed from this study, and further work will be necessary to confirm the present results.

Continuous wear contact lens surface chemistry and wearability.

Continuous wear (CW) contact lenses are defined as lenses composed of hydrogel polymers containing elements other than carbon, hydrogen, oxygen, and nitrogen that enhance oxygen permeability to an extent greater than water alone. Those elements are silicon and fluorine. Silicon is incorporated as siloxanes, and fluorine is used as fluoroalkyl. Despite the water present in CW lenses, they are not wearable without surface modification because of the tendency of siloxanes and fluoroakyls to move in the soft polymers, orient, and become enriched at the surface. Various methods of surface modification are discussed, with emphasis on the plasma technologies used by the two commercial CW lens products, Focus Night & Day and PureVision. Speculation about future directions in surface chemistry are also presented.

Microbial Keratitis and Vision Loss with Contact Lenses

Microbial keratitis is the only sight-threatening adverse event that occurs with contact lens wear. This article gives a preliminary estimation of the incidence of microbial keratitis and vision loss with continuous-wear contact lenses made from highly oxygen permeable (Dk) materials. The most up-to-date data available on microbial keratitis and vision loss are collected from a range of sources including industry, private practice, and publications and is reviewed. There have been 16 cases of microbial keratitis with high-Dk silicone hydrogel lenses. Of the 13 where data are available, none have lost two or more lines of best-corrected visual acuity (BCVA). First approximation indicates that the incidence of microbial keratitis with high-Dk silicone hydrogel lenses may be lower than the incidence with low-Dk soft lenses during extended wear. The rate of loss of more than two lines of BCVA is low in patients that develop microbial keratitis with low- and high-Dk soft lenses.

PATIENT PERCEPTIONS OF 30-DAY CONTINUOUS WEAR CONTACT LENSES.

Thursday, December 12, 2002: San Diego Convention Center: Room 11 A-B: Cornea and Contact Lens Lectures: PDF Only

Effect of lens base curve on subjective comfort and assessment of fit with silicone hydrogel continuous wear contact lenses.

To study the effect of base curve on subjective comfort of silicone hydrogel extended wear lenses. Ninety-five subjects were first trial fitted with 8.6-mm base curve lotrafilcon A (Focus Night & Day) lenses and then with 8.4-mm lenses only if poor subjective comfort or poor fit was present. Comfort and fit were assessed after 15 min. Subjects with discomfort or signs of poor fit were then trial fitted with 8.4-mm lenses. Of 190 eyes, 74.2% were fitted with 8.6-mm lenses, and 23.7% required 8.4-mm lenses. Two (2.1 %) subjects could not be fitted with either base curve. Mean steep keratometry (K) reading for eyes dispensed with 8.6-mm lenses was 43.88 D and 45.56 D for eyes dispensed in the 8.4-mm lenses (p < 0.001). A clinically useful criterion showing the need for 8.4-mm lenses was steep K of > or = 45.50 D; 77% of these eyes required the steeper lens for good comfort and fit. Subjective discomfort with 8.6-mm lenses was also a useful signal for the need of a steeper lens; mean comfort scores for those subjects rose from 6.33 with 8.6-mm lenses to 9.44 with the 8.4-mm lenses for eyes requiring the steeper lens (p < 0.001).

A 1-year prospective clinical trial of balafilcon a (purevision) silicone-hydrogel contact lenses used on a 30-day continuous wear schedule

Purpose To evaluate silicone-hydrogel balafilcon A (PureVision, Bausch & Lomb Inc., Rochester, NY) contact lenses worn on a 30-day continuous wear basis when compared with a traditional hydrogel (Acuvue, Vistakon, Johnson and Johnson Vision Products, Inc., Jacksonville, FL) worn on a 7-day extended wear schedule. Design Prospective, comparative, paired-eye, interventional, multicenter clinical trial. Participants Two hundred twelve ametropes with no significant ocular pathology. Methods Subjects with normal ocular health who conformed to a set of standard criteria were monitored at seven different sites around the globe. Subjects wore both study lenses simultaneously, one on each eye. Lenses were assigned to right and left eyes according to a randomized schedule. The silicone hydrogel was removed and replaced every month and the traditional hydrogel was removed every 7 days and replaced at 14-day intervals. Subjects were followed for up to 1 year with discontinuation on indication divided between lens-related causes, unrelated factors, and loss to follow-up. Main outcome measures Discontinuations, symptoms, vision, lens fit, lens surface assessment, slit-lamp assessment, and patient preferences. Results One hundred twenty three subjects completed the 12-month wearing period. There were no vision-threatening events with either lens type. The silicone-hydrogel lenses showed statistically superior performance in physiologic terms with regard to epithelial microcysts, striae, corneal staining, limbal injection, and bulbar injection. Inflammatory reactions, such as corneal infiltrates and tarsal conjunctival abnormalities occurred at similar rates between the lens types. Visible deposition and postlens debris with associated transient corneal indentation were significantly lower with the traditional hydrogel material at specific time points in the study. Visual acuity was comparable with the two lens types. Subjects rated the silicone-hydrogel material as preferable on subjective scales of dryness, comfort, and lens handling. Overall subjective performance was rated superior with the silicone-hydrogel material. Conclusions The high oxygen performance of the silicone-hydrogel lenses provides a superior physiologic environment compared with a traditional hydrogel material during continuous wear. Despite the slightly higher levels of visible deposit on the silicone-hydrogels, superior subjective responses suggest that the plasma coating technology on these lenses is effective in providing comfortable lens wear. The results look promising for the success of silicone-hydrogels as the material of choice for continuous wear contact lenses.

Maintaining the cornea and the general physiological environment in visual neurophysiology experiments

Neurophysiologists have been investigating the responses of neurons in the visual system for the past half-century using monkeys and cats that are anesthetized and paralyzed, with the non-blinking eyelids open for prolonged periods of time. Impermeable plastic contact lenses have been used to prevent dehydration of the corneal epithelium, which would otherwise occur in minutes. Unfortunately, such lenses rapidly introduce a variety of abnormal states that lead to clouding of the cornea, degradation of the retinal image, and premature termination of the experiment. To extend the viability of such preparations, a new protocol for maintenance of corneal health has been developed. The protocol uses rigid gas permeable contact lenses designed to maximize gas transmission, rigorous sterile methods, and a variety of methods for sustaining and monitoring the overall physiology of the animal. The effectiveness of the protocol was evaluated clinically by ophthalmoscopy before, during, and after the experiments, which lasted 8–10 days. Histopathology and quantitative histology were performed on the corneas following the experiment. Our observations showed that this protocol permits continuous contact lens wear without adversely affecting the corneas. Thus, it is possible to collect data 24 h each day, for the entire duration of the experiment.

Proposed practice guidelines for continuous contact lens wear

The introduction of silicone‐containing hydrogel contact lenses (SCHCLs) for continuous wear (CW) presents practitioners with a unique challenge. To facilitate the transition, we propose a set of guidelines for the conduct of CW practice. The general concepts for the guide are derived from a range of similar codes of practice that have been produced for a range of aspects of eye care. The more general competencies required of eye care practice are assumed and are not discussed in detail. The document is based on the precept that the prescription of SCHCLs is an appropriate practice for suitably screened patients. Practitioners should acquire general and specific knowledge of information applicable to CW with SCHCLs. Support staff should be educated to handle a range of requirements specific to CW. There are no consulting room facilities required beyond those necessary for general optometric practice but we highly recommend that the CW practitioner use grading scales for anterior eye complications and a guide to corneal infiltrative conditions. More stringent examination protocols are required than for general contact lens practice, particularly in the selection of the patient. Patient management should be conducted to a medical standard of care. Documentation is critical and will involve general information about the product, an agreement, disclosure of risk factors, instructions for wear and care, recording of patient questions and answers provided, an informed consent form and detailed, accurate record keeping. A guideline such as this document cannot be positioned as a legal standard of care, but may be used in the formulation of such a standard.

Continuous wear contact lenses: have we been here before?

New developments in contact lens materials have led to the introduction of new lenses designed for up to 30 days of continuous wear. Will these lenses lead to safer and healthier overnight use of lenses?

Attachment of Pseudomonas to Human-Worn, Disposable Etafilcon A Contact Lenses

After 7 days of continuous wear, Acuvue (Vistakon, Jacksonville, FL, U.S.A.; etafilcon A) lenses were soaked in a Pseudomonas aeruginosa suspension (1.4 x 10(8) cfu/ml). New Acuvue lenses served as controls. A single strain of P aeruginosa harvested from a human corneal ulcer was used throughout the experiment. Lenses were examined by culture and scanning electron microscopy (SEM). We found significantly greater (p less than 0.05) bacterial attachment to new Acuvue lenses [culture, 3.1 x 10(4) (+/- 0.82 x 10(4)) cfu/mm2; SEM, 2.6 x 10(4) (+/- 0.47 x 10(4)) bacteria/mm2] compared with those previously worn [culture, 1.0 x 10(4) (+/- 0.17 x 10(4)) cfu/mm2; SEM, 0.73 x 10(4) (+/- 0.21 x 10(4)) bacteria/mm2]. No statistical difference was found among the individuals. Our findings demonstrate that the biological coating resulting from 1 week of continuous contact lens wear restricts P. aeruginosa attachment to the Acuvue lens when comparing new and used lenses.

Contact lens anterior surface pH

Recent reports of CO 2 accumulation under hydrogel lenses, paired with the detection of a decrease in stromal pH following contact lens wear, have highlighted the potential for tear pH assessment as a clinical tool. The in situ anterior hydrogel lens surface pH was measured with a flat-surfaced, self-referenced pH electrode in order to indirectly evaluate fluid exchange between the precorneal tear film and hydrogel lenses. Volunteer human subjects were fitted with moderate water content (58%), disposable extended wear hydrogel lenses. Measurements were recorded from the lens in its packaged state (pH 6.99), from the lens in situ 5 minutes after initial lens application (pH 7.17), 24 hours later (pH 7.34), and at the end of 7 days continuous contact lens wear (pH 7.43). Possible cornea-tear film-hydrogel lens interactions could explain certain hydrogel lens-associated contrast sensitivity deficits and transient endothelial changes.

The Effects of Continuous Soft Contact Lens Wear After Radial Keratotomy in Cats

ABSTRACT: Radial keratotomy utilizing the American technique was performed on seven cat eyes. After six weeks both eyes were fitted with CSI extended wear soft contact lenses and corneal thickness and corneal vascularization analyzed. While the results of mean central corneal thickness were not significant, all experimental eyes showed some degree of vascularization (except those fitted three months after surgery). This complication following contact lens use must be closely monitored in patients with poor uncorrected visual acuity following radial keratotomy.

Extended-Wear Soft Contact Lenses-Reply

In Reply. —I regret that Stark et al believe we have misrepresented the intent and content of [their] past articles on extended-wear contact lenses by stating that [they] reported no significant This was not our intent. However, they reported ... good visual results with a minimum of complications,1 ... no cases of infectious corneal ulcers or scarring or permanent visual loss, 1 and ... no infectious corneal ulcers and no significant corneal neovascularization (at 22 months' follow-up). 2 These statements, which we believed connoted minimal complications with continuous wear of soft contact lenses, did prompt us to review and analyze our own experience 3 and that of others. 4,5 As reported, we 3 did note a significant incidence of potentially serious corneal complications. Others have reported a similar incidence of serious corneal complications, including infected corneal ulcers. 4,5 The less than 1% incidence of infected corneal ulcers now described by Stark et

Guttate endothelial changes with anterior eye inflammation.

This report details the rapid appearance and gradual disappearance of guttate endothelial changes in a patient who experienced an acute 'red eye' associated with the continuous wear of contact lenses. This episode of acute inflammation was accompanied by a diffuse corneal infiltrate, endothelial bedewing, and the guttage changes.

Ocular Chances Associated with Continuous Wear of Contact Lenses

This paper is based on clinical data derived from 35 patients having worn a variety of contact lenses on a continuous wear basis for periods up to two years. Aspects discussed include oedema-induced changes in the ocular parameters, miscellaneous disturbances to corneal integrity and adverse eye reactions. Although there has been considerable variation in the corneal swelling response (depending on contact lens gas transmission, patient age and state of the cornea), most patients have shown adaptation within the first one to two weeks. Epithelial microvesicular changes have been observed in a significant number of patients. The adverse eye reactions encountered included corneal ulceration, pannus and acute ‘red-eye’ reaction.

Some Criteria for Continuous Wear of Contact Lenses

From the time when the first contact lens was worn it has been the hope of all involved in contact lens practice to increase tolerance so that ultimately the appliance can be worn for first daily wear, and now in certain instances, for prolonged periods of wear. Given the range of modem materials, lens sizes, and forms, and the individual variations present in the human eye and environment, criteria can now be determined for prolonged wear. These criteria involve physiological and biochemical principles regarding eye tissue survival when in contact with plastic occlusion of the contact lens. The pathological changes in eye tissues that have been noted, and their significance, and the responsibilities of all professions fitting extended wear lenses form the fulcrum about which future policy for constant wear must evolve.