Contact Lens Spectrum Supplements

Special Edition 2017

Contact Lens Spectrum

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c l s p e c t r u m . c o m C O N T A C T L E N S S P E C T R U M S P E C I A L E D I T I O N 2 0 1 7 7 RESEARCH REVIEW those previously reported. New lens types have not reduced the inci- dence of disease. Overnight use of any contact lens is associated with a higher risk compared to daily use. In another study evaluating MK in wearers of high-Dk silicone hy- drogel contact lenses worn for 30- day continuous wear (Schein et al, 2005), the authors found that the incidence of visual acuity loss due to MK among users of the silicone hydrogel contact lens was low; how- ever, the overall rate of presumed MK with the wearing schedule of as many as 30 nights was similar to that previously reported for tra- ditional extended wear soft lenses worn for fewer consecutive nights. Defining and Understanding MK in Contact Lens Wear Diagnostic criteria for MK can have a dramatic impact on study in- cidence rate outcomes. Efron and Morgan (2006) looked at this im- portant issue. The authors applied a number of diagnostic criteria sets to a data set of cases and examined a variety of lens wearing modalities and lens types. They found that the choice of criteria for diagnosing contact lens-associated MK has a significant impact on calculations of the incidence of this condition. An interesting study looked at the relative risk of silicone hydrogel overnight wear contact lens-associ- ated MK as compared to other life risks (Szczotka-Flynn et al, 2009). A comparative ratio was defined as the incidence of MK in a population of silicone hydrogel extended wear contact lens users divided by the incidence of other disease or occur- rence in a given population at risk. The authors found that the risk of silicone hydrogel lens-related MK is about 1.5 to 16 times less risky com- pared to certain nonfatal disruptive occurrences in the general popula- tion, and it is about the same as the risk of developing breast cancer. Compared with other ocular condi- tions, the risk of MK with silicone hydrogel lenses is about the same as developing late-stage age-related macular degeneration or retinal de- tachment after cataract extraction on an annual basis; it is more than 200 times greater than developing eye or orbit cancer; it is about 7, 20, or more than 30 times less than pro- ceeding to penetrating keratoplasty in keratoconus, developing nuclear cataract, or experiencing a corneal inflammatory event during low-Dk extended wear, respectively. They concluded that although the risk of MK with modern day silicone hydrogel contact lens ex- tended wear has not changed since the 1980s, when put in perspective with other life risks, it is a relatively rare occurrence. What about those "Specialty" Contact Lenses? We have quite a bit of data relat- ed to the incidence rates of MK in standard contact lens wear both for daily wear and extended wear; how- ever, little is known about MK rates for what some would call "specialty" contact lenses. Again, a definition would be in order to identify what lenses would be classified as such. Lenses such as hybrid designs, scler- al GPs, custom-designed soft lenses, and piggyback/tandem lens systems would arguably fall into this catego- ry. Unfortunately, there is virtually no information pertaining to MK rates for these types of lenses based upon well designed and controlled clinical trials. One study looked at the perfor- mance of a high-Dk rigid GP lens design worn for up to 30 days of con- tinuous wear (Albright et al, 2010). In this study of 507 participants over a 24-month follow-up period, there were no incidences of MK. Another study looked at the suc- cess rate for scleral GP contact lenses fit for patients following pen- etrating keratoplasty (Severinsky et al, 2014). In this study, a total da- tabase of 31 consecutive patients fit with scleral GP lenses was retro- spectively reviewed. Demographic data, etiology prior to lens fitting, visual outcomes, follow-up time, and complications were analyzed. The authors found that during the studied period, 10 eyes (30.0%) pre- sented at least one graft rejection episode, and two eyes (6%) had an episode of MK. One other study looked at the performance of a particular GP scleral lens used to treat patients who had persistent epithelial de- fects that did not respond to other traditional therapies (Ciralsky et al, 2015). The study was based on a retrospective review of eight eyes of seven consecutive patients who had persistent epithelial defects refractory to traditional therapies. The standardized treatment regi- men consisted of 1) 24-hour scleral lens wear until re-epithelialization was achieved; 2) brief daily device removal, cleaning, disinfection, and reservoir fluid replacement; 3) addition of a benzalkonium chlo- ride (BAK)-free fourth-generation fluoroquinolone antibiotic drop to the reservoir; and 4) transition to Continued on p.20 D i a g n o s t ic c ri t e ri a f o r m ic r o bi a l k e r a t i t i s c a n h a v e a d r a m a t i c i m p a c t o n s t u d y i nc i d enc e r a t e o u t c o me s .

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