Prolonging contact lens wear and making contact lens wear safer
ABSTRACT To summarize the present status of safety and efficacy of contact lens wear.
Ovid Medline searches were performed on records from 1966 through 2005 using keywords: keratitis, contact lens complications, extended-wear contact lenses, and silicone-hydrogel contact lenses.
Patients desire comfort, clarity of vision, and prolonged contact lens wear when contact lenses are used to correct refractive error. Practitioners desire patient satisfaction but also require maintenance of the integrity of the eye and no complications that jeopardize vision or health of the eye. Improvements in the oxygen permeability of the contact lens materials, design of the contact lens and its surface, and solutions for the maintenance of the lens have reduced but not eliminated the risks of infection, inflammation, and conjunctival papillary reaction associated with contact lens wear. The lessons of past and recent history suggest that patient education and practitioner participation in the management of contact lens wear continue to be critical factors for patient satisfaction and safety in the extended wear of contact lenses.
The availability of highly oxygen permeable contact lenses has increased the tolerance and safety of extended contact lens wear, but patient instruction and education in proper use and care of lenses is required and caution is advised.
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- "Conventional or daily-disposable hydrogel contact lenses, which still form a common type of bandage contact lens after corneal refractive surgery, are associated with reduced oxygen availability, which does not fulfill the criteria for overnight wear. The introduction of silicone-hydrogel (SIH) lenses, just over 10 years ago, offered the choice of a material with high oxygen permeability (Dk) for therapeutic applications, which was also approved from the U.S. Food and Drug Administration (FDA) for extended/overnight wear  . It was not surprising, then, that the first clinical "
ABSTRACT: PURPOSE: To evaluate the efficacy of two silicone hydrogel (SiH) contact lenses, approved for continuous wear for one week, following photorefractive keratectomy (PRK). METHODS: Forty seven myopic patients (94 eyes) undergone bilateral PRK were enrolled in this prospective, double-masked, comparative study. One eye of each patient was fitted with a Lotrafilcon B lens (Ciba Vision, Duluth, US; 30-day recommended replacement) whereas the fellow eye was fitted with an Asmofilcon A lens (Menicon, Nagoya, Japan; 14-day recommended replacement). Epithelial defect size was assessed using slit lamp biomicroscopy on the day of surgery and at days 1-4 post-operatively. Uncorrected and best-corrected visual acuity and retinal straylight (C-Quant, Oculus Optigerate, Germany) were evaluated pre-operatively and one month post-operatively. RESULTS: Average epithelial defect size for Asmofilcon A and Lotrafilcon B was 25.5±11.0mm(2) vs. 27.1±9.9mm(2) at day 1 (p=0.007) and 6.3±7.0mm(2) vs. 9.2±9.5mm(2) at day 2 (p=0.012) post-operatively. Re-epithelialization at day 3 was completed in 87.2% of the eyes fitted with Asmofilcon A lenses, compared to 74.5% with Lotrafilcon B lenses (p=0.012). At the 3rd post-operative day 29.8% of re-epithelialized eyes showed irregular suture with Lotrafilcon B, compared to 12.8% eyes with Asmofilcon A lenses (p<0.001). Finally, no statistically significant differences were found post-operatively between the two lenses retinal straylight (p=0.98) and best-corrected visual acuity (p=0.68). CONCLUSIONS: SiH lenses can be used as an effective bandage after PRK due to the limited time requested for achieving complete corneal re-epithelialization. Faster and smoother epithelial healing is provided with Asmofilcon A over Lotrafilcon B lenses.Contact lens & anterior eye: the journal of the British Contact Lens Association 03/2013; 36(5). DOI:10.1016/j.clae.2013.02.015 · 2.00 Impact Factor
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- "Contact lenses are worn by over 34 million people in the United States . Hydrogel contact lenses partition the aqueous layer into two layers, a 2.5 m thick aqueous precontact lens layer, and a 2.5 m thick aqueous layer between the lens and cornea . "
ABSTRACT: Accelerated evaporation of tears may contribute to dry eye symptoms. It is not clear whether contact lenses decrease or increase the rate of evaporation of tears. In this study, the rates of evaporation through contact lenses (ERTCL) were measured in vitro to gain insight to this question. Contact lenses were equilibrated with various solutions to determine if they influenced ERTCL in vitro. ERTCL was measured gravimetrically. ERTCL measured in vitro for used contact lenses was about 20% faster than for buffer alone suggesting that natural tear components bound to the lenses changed the ERTCL. One natural tear component that binds to contact lenses is waxes. Equilibration of contact lenses with wax increased the ERTCL by about 30% suggesting that waxes might potentially increase ERTCL in vivo. Squalene, found in sebum and possibly meibum was infused into the contact lenses as a step toward decreasing the ERTCL. Squalene decreased ERTCL by over 60% in vitro. Soaking a contact lens in DuraSite(®) with benzalkonium chloride (BAK) did not alter the ERTCL. ERTCL were about 40% higher than the evaporation rate of DuraSite(®) alone or without BAK. In addition to lowering the ERTCL, the squalene in contact lenses could be a source of terpenoids to replace the terpenoids deficient in patients with MGD. If the ERTCL could be minimized in vivo, contact lenses could potentially be used to relieve dry eye symptoms in patients with evaporative dry eye.Contact lens & anterior eye: the journal of the British Contact Lens Association 08/2012; 35(6). DOI:10.1016/j.clae.2012.07.008 · 2.00 Impact Factor