Search

Acanthamoeba keratitis is a potentially devastating protozoan infection of the cornea, the transparent outermost covering of the front of the eyeball. The infection is caused by Acanthamoeba, a free-floating protozoa that is found in air and soil, as well as in salt, fresh and chlorinated water. Contact lens use is associated with about 85 percent of cases of Acanthamoeba keratitis. The most frequently implicated contact lenses have been hydrogel disposable extended wear contact lenses. Three cases are reported in which patients using these lenses developed Acanthamoeba keratitis. In two cases, the lenses were removed and then reinserted without having been sterilized or disinfected. The third patient, rather than wearing the lenses continuously for one week and then discarding them as is the recommended procedure, replaced the lens after 10 to 14 days and frequently removed the lenses, rinsed them in tap water (well water), and stored them overnight. The supposed advantages of disposable contact lenses were negated when the lenses were either rinsed with a contaminated solution (well water) or stored temporarily or otherwise manipulated. It should be emphasized to patients that once disposable lenses are removed from the eye they should be disposed of or disinfected before they are reinserted. (Consumer Summary produced by Reliance Medical Information, Inc.)

IMPORTANCE: Determining factors associated with endothelial cell loss after Descemet stripping automated endothelial keratoplasty (DSAEK) could improve long-term graft survival. OBJECTIVE: To evaluate the associations of donor, recipient, and operative factors with endothelial cell density (ECD) 3 years after DSAEK in the Cornea Preservation Time Study. DESIGN, SETTING, AND PARTICIPANTS: This cohort study was a secondary analysis of data collected in a multicenter, double-masked, randomized clinical trial. Forty US clinical sites with 70 surgeons participated, with donor corneas provided by 23 US eye banks. Individuals undergoing DSAEK for Fuchs dystrophy or pseudophakic/aphakic corneal edema were included. INTERVENTIONS: The DSAEK procedure, with random assignment of a donor cornea with a preservation time of 0 to 7 days or 8 to 14 days. MAIN OUTCOMES AND MEASURES: Endothelial cell density at 3 years as determined by a reading center from eye bank and clinical specular or confocal central endothelial images. RESULTS: The study included 1090 participants (median age, 70 years) with 1330 affected eyes (240 bilateral cases [22.0%]), who underwent DSAEK for Fuchs dystrophy (1255 eyes [94.4%]) or pseudophakic/aphakic corneal edema (PACE) (75 eyes [5.6%]). Of these, 801 eyes (60.2%) belonged to women and 1207 (90.8%) to white individuals. A total of 749 participants (913 eyes; 164 [21.9%] bilateral cases) had functioning grafts with acceptable endothelial images preoperatively and at 3 years postoperatively and were included in this analysis. Factors associated with a lower ECD at 3 years (estimated effect with 99% CI) in the final multivariable model included donors with diabetes (−103 [−196 to −9] cells/mm2), lower screening ECD (−234 [−331 to −137] per 500 cells/mm2), recipient diagnosis of PACE (−257 [−483 to −31] in cells/mm2), and operative complications (−324 [−516 to −133] in cells/mm2). Endothelial cell loss (ECL) from a preoperative measurement to a 3-year postoperative measurement was 47% (99% CI, 42%-52%) for participants receiving tissue from donors with diabetes vs 43% (99% CI, 39%-48%) without diabetes; it was 53% (99% CI, 44%-62%) for participants diagnosed with PACE vs 44% (99% CI, 39%-49%) for those diagnosed with Fuchs dystrophy, and 55% (99% CI, 48%-63%) in participants who experienced operative complications vs 44% (99% CI, 39%-48%) in those who did not. No other donor, recipient, or operative factors were significantly associated with 3-year ECD. CONCLUSIONS AND RELEVANCE: Donor diabetes, lower screening ECD, a PACE diagnosis in the recipient, and operative complications were associated with lower ECD at 3 years after DSAEK surgery and may be associated with long-term graft success. While causation cannot be inferred, further studies on the association of donor diabetes and PACE in recipients with lower 3-year ECD warrant further study.

Two patients developed Acanthamoebakeratitis associated with the use of disposable extended-wear hydrogel contact lenses. Both patients removed, irrigated, and reinserted the contact lenses without disinfecting them. One patient wore the lenses on a daily basis, rinsed the lenses in tap water, stored them overnight, and discarded them weekly. Both infections were treated successfully. In a third patient, Acanthamoebaspecies was cultured from two pairs of disposable lenses that had been stored in cases rinsed with well water. Potential benefits from disposable contact lens wear are negated when patients do not comply with a continuous wearing schedule.

• Previous controlled studies on contact lens-associated ulcerative keratitis were performed before the widespread use of disposable contact lenses. Therefore, a controlled study was undertaken to determine the relative risk of ulcerative keratitis among users of disposable soft contact lenses compared with the risk among users of other lens types. Forty-six consecutive cases of contact lens-associated ulcerative keratitis were identified between January 1990 and June 1992 at a corneal specialty practice in western Michigan. Five controls, matched to each case patient according to the dispensing date and prescribing practitioner, were obtained for 42 cases (91%). Users of dailywear rigid gas-permeable lenses had the lowest risk of developing ulcerative keratitis. Relative to users of daily-wear soft contact lenses, users of extended-wear soft contact lens had an age-adjusted and sex-adjusted relative risk of 1.87 (95% confidence interval, 0.61 to 5.71). Disposable soft contact lens users had the highest risk of developing ulcerative keratitis, with an adjusted relative risk of 14.16 (95% confidence interval, 5.47 to 37.63) compared with daily-wear soft contact lens users and 7.66 (95% confidence interval, 2.27 to 25.83) compared with conventional extended-wear soft contact lens users.

OBJECTIVE: To assess the relative risk of contact lens—associated ulcerative keratitis by lens type and related lenswearing behavior. DESIGN: Case-control study. SETTING/PARTICIPANTS: Forty practice-based case patients with contact lens—associated ulcerative keratitis and 180 control patients matched to the case patients' dispensing practitioner and date of contact lens prescription. RESULTS: Compared with users of daily-wear soft lenses, users of disposable soft contact lenses had a 13.33-fold (95% confidence interval [CI], 5.35 to 33.20) excess risk of ulcerative keratitis. However, after adjusting for overnight wear, the excess risk associated with disposable contact lenses is reduced to 3.21 (95% CI, 1.22 to 14.36). Overall, overnight wear of contact lenses conferred an 8.25-fold excess risk (95% CI, 3.33 to 25.58) of ulcerative keratitis after controlling for lens type. No protective effect of standard compared with substandard lens hygiene was found. The risk of ulcerative keratitis attributable to overnight wear was estimated at 49% for users of daily-wear lenses and 74% for users of lenses approved for overnight wear. CONCLUSION: Overnight wear of contact lenses is the overwhelming risk factor for ulcerative keratitis among contact lens users. We estimate that 49% to 74% of cases of contact lens—associated ulcerative keratitis could be prevented by eliminating overnight wear.

IN REPLY. —We agree with Levy that the selection of suitable controls is the most difficult and most important aspect in the design of a case-control study. His main objection to our study design is that we did not match our cases and controls with regard to contact lens wear schedule. This was intentional, since we were not primarily interested in the lens material itself as a risk factor for ulcerative keratitis in isolation from the interaction of patients with contact lens products. Rather, we were interested primarily in the more clinically relevant question of the risk of ulcerative keratitis among users of different contact lens types.In a case-control study, cases and controls are compared with respect to the attributes or exposures thought to be related to the disease under consideration. Controls should ideally be matched to cases in all respects except for the risk factor(s) of interest. Any

The article discusses the postoperative care of patients who have undergone a penetrating keratoplasty. According to doctor David D. Verdier, patients should need numerous examinations, education related to the disease, and special attention to the corneal surface. Moreover, he suggests to apply a nonpreserved ointment like acyclovir to avoid the risks of recurrent corneal surface problems.