Contact Lens Promising in Glaucoma With few severe side effects, the contact lens represents a safe treatment option In a 40-patient trial, in which participants wore the sensors for 24 hours on two separate occasions, all but two experience some type of adverse event such as blurred vision, conjunctival hyperemia, or superficial punctate keratitis, reported Robert N. Weinreb, MD, of the University of California San Diego, and colleagues. But only seven of 149 events overall were rated as severe, and suggested that the rate of adverse events was similar to what might be expected from ordinary contact lenses, they wrote online in Archives of Ophthalmology. In terms of efficacy, the device successfully delivered the full 24-hour pressure recordings in both sessions for 36 of the 40 patients. Weinreb and colleagues characterized the reproducibility of pressure measurements over the two sessions as fair to good, with a coefficient correlation of 0.59. The current study demonstrates that [the] contact lens sensor is a safe and well-tolerated device for repeated use in glaucoma patients or those suspected of having the disease, the researchers concluded. The availability of continuous 24-hour [intraocular pressure] monitoring holds the promise to improve glaucoma care, they added. Elevated intraocular pressure is a major risk factor for glaucoma and many treatments for the disorder are aimed at reducing pressure. In routine practice, the pressure is measured in the clinic in snapshot fashion, although a circadian pattern of variation throughout the day is well known. Obtaining a full 24-hour pressure curve requires an expensive study in a sleep laboratory, Weinreb and colleagues noted, and it may not be fully accurate because patients have to be awakened to take measurements at night. Therefore, no method now exists to measure intraocular pressure during undisturbed sleep — the time at which intraocular pressure is believed to be highest in glaucoma patients. However, a Swiss company named Sensimed AG has developed an oxygen-permeable soft contact lens containing two tiny strain gauges, which detect changes in corneal curvature that correlate with intraocular pressure. It transmits data wirelessly to a small antenna attached to the skin around the eye, which in turn passes the data via a thin cable to a recorder worn around the waist. The product, called Triggerfish, is approved in Europe but not in the U.S. The current study involved 19 patients with confirmed glaucoma and 21 suspected of having the condition. Each patient wore the contact lens sensor on one eye for 24 hours in each of two sessions, conducted 1 week apart. Numbers and rates of mild adverse effects were as follows (multiple events in a single patient were possible): Blurred vision: 58 events, 80 percent of patients Conjunctival hyperemia: 52 events, 75 percent of patients Superficial punctate keratitis: 5 events, 12 percent of patients Eye irritation: 3 events, 8 percent of patients Eye itching: 3 events, 8 percent of patients In addition, one patient each had moderate superficial punctate keratitis and blurred vision, and two patients experienced a total of five episodes of severe conjunctival hyperemia. Weinreb and colleagues found considerable intra-individual variation in 24-hour pressure patterns over the two sessions, leading to the correlation coefficient of 0.59 which they had prespecified as fair to good reproducibility (a coefficient of more than 0.75 was required for a rating of excellent). Use of antihypertensive glaucoma eyedrops did not appear to affect the reproducibility. Weinreb and colleagues found that patients visual acuity was reduced, compared with baseline, following removal of the contact lens sensor at the end of each session. They indicated that this effect was expected because the lenss intentionally tight fit can itself alter the corneal curvature. They noted that most patients reported that their vision had returned to baseline levels the day after the sessions. One limitation of the Triggerfish product is that its data output does not translate directly into mm Hg, the standard unit for measuring intraocular pressure, but rather an arbitrary unit corresponding to the strain gauges electrical signal, the researchers indicated. This limitation precludes the use of intraclass correlation coefficients for the statistical reproducibility analysis, they explained. Also, the contact lens sensor technology may be subject to artifacts. By John Gever, Senior Editor, MedPage Today Medically Reviewed by Robert Jasmer, MD Medical Device China You can find out more at croxxmore Croxxmore Service : - Sourcing and Manufacturing Solution - Supplier Inspection/ QC - In-Country Representation - Medical Device OEM/ODM/OBL - China Medical Device Industry Advisory - Marketing Analysis and Research in China - Medical Distributor Search in China - Exhibition Service
Posted on: Thu, 17 Jul 2014 06:18:06 +0000
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