continuous wear colloquy
Comparing Inflammatory Complications of EW Hydrogels
BY LORETTA B. SZCZOTKA-FLYNN, OD, MS, FAAO
Inflammatory complications have long existed in relation to low-Dk extended wear (EW) and we've effectively managed them for many years, yet they've received more formal names and attention since the introduction of silicone hydrogels. Overnight use of high-Dk silicone hydrogels has effectively eliminated hypoxia, and you may wonder what effect they've had on the incidence of inflammatory complications. First, let's review some of these inflammatory complications.
Contact Lens Peripheral Ulcer (CLPU) may present with symptoms, in which case the patient complains of mild pain, redness and watering. The lesion is usually unilateral, characterized by regional hyperemia and a well-circumscribed, dense, white, focal infiltrate that stains. If the episode is asymptomatic, then you'll see a white, focal scar(s) in the mid to far corneal periphery on a follow-up visit.
Contact Lens Acute Red Eye (CLARE) is an acute-onset red eye (by definition it's associated with sleeping in lenses) with possible small, multiple, faint, diffuse infiltrates in the cornea. The patient is symptomatic with irritation, pain and redness, and the condition is usually unilateral.
Infiltrative Keratitis (IK) is a general category for symptomatic infiltrative events that don't fit the profile of CLPU or CLARE. Typically, IK is a relatively mild event characterized by infiltration of the anterior stroma, with or without epithelial involvement. IK is usually accompanied by moderate redness and irritation, and isn't always associated with sleep.
The incidence of inflammatory complications with low-Dk, six-night EW is well documented in Australian studies.
One recent U.S. study (Dillehay et al, 2003) reported annualized incidence rates with 30-night silicone hydrogel lens wear (Table 1). Although two U.S. FDA silicone hydrogel 30-day CW studies from 2001 reported no statistical difference between the infiltrate rates between low-Dk and high-Dk lenses, we may be seeing a shift toward lower infiltrate rates with silicone hydrogel lenses as practitioners have the availability of multiple base curves with high-Dk lenses and are selecting their patients more appropriately.
Certain patient-dependent factors are associated with inflammatory adverse responses. In low-Dk extended wear, smoking, previous inflammatory complications and microbial lens contamination are associated risk factors.
In silicone hydrogel lens use, researchers have found that demographic factors such as younger age (<21 years), male gender and Asian ethnicity, as well as clinical slit lamp signs of blepharitis and bulbar redness, are associated with inflammatory complications.
Be proactive in fitting EW contact lenses for overnight use by effectively screening your patients for the potential risk factors that I just discussed.
TABLE 1Incidence Rates for Inflammatory Complications with Low-Dk and High-Dk Lenses
|SIX NIGHT, LOW-DK*||30 NIGHT, HIGH-DK**|
* From Sweeny D. Silicone Hydrogels. Butterworth-Heineman.
** Dillehay S, Long B, et al. Patient Experience and Management in HDK Silicone Hydrogel Soft Contact Lenses. Poster at 2003 AAO Annual Meeting.
Dr. Szczotka-Flynn is an associate professor at Case Western Reserve University Dept. of Ophthalmology and is director of the Contact Lens Service at University Hospitals of Cleveland.