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Objective: To evaluate the risk factors that may contribute to microbial keratitis in contact lens wearers., Material and Method: This prospective case-control study included 52 patients with contact lens related keratitis treated between 1 December 2006 and 15 October 2007 at the Faculty of Medicine, Siriraj Hospital. Controls were sixty-three contact lens users attending with disorders unrelated to contact lens wear All subjects with informed consent were interviewed about demographic data, types of contact lens and contact lens solutions, contact lens use past the recommended replacement date, overnight wear, and lens hygiene. Odds ratio (OR, estimates of relative risks) and 95% confidence interval (CI) were calculated through multivariable logistic regression analysis., Results: The use of contact lens past the replacement date caused the highest risk of developing microbial keratitis (OR = 9.1; CI 1.8-45.4, p = 0.005). Overnight wear of lenses (OR = 2.9, CI 1.3-6.2, p = 0.012) and poor lens hygiene (OR = 2.3, CI 1.0-5.1, p = 0.007) significantly increased the risk of microbial keratitis, respectively. None of the other risk factors showed a significant association., Conclusion: The significant risk factors for contact lens related microbial keratitis in the present study were the use of contact lens past the replacement date, overnight wear, and poor lens hygiene. Thus, the appropriate advice of contact lens care and usage may reduce the risk of microbial keratitis in contact lens wearers.

Clinical presentations of patients with Acanthamoeba keratitis (AK) attending the Faculty of Medicine Siriraj Hospital during 1996-2006 were reviewed. The studied parameters included history of ocular trauma, use of contact lenses, associated eye diseases, systemic diseases, visual acuity, symptoms, signs, treatment, visual outcomes, and sequelae. Data were analyzed by comparing non-contact lens (nCL) and contact lens (CL) wearers with eachother. Twenty-two patients (24 affected eyes) (68.2% female) had AK, 9 (37.5%) were nCL and 15 (62.5%) were CL. Both groups had similar basic characteristics; however the nCL group was significantly older (48.3 +/- 14.5 vs 30.6 +/- 15.3 years old, p=0.006), and tended to have a longer duration of symptoms with more severe clinical findings, but this was not statistically significant. Eleven had severe ciliary injection (nCL 55.5%, CL 40.0%), 3 had satellite lesions (nCL 22.2%, CL 6.7%), 2 had radial keratoneuritis in the CL group (13.3%), 1 ring infillrate in the nCL group (11.1%) and 1 pseudodendrite in the CL group (6.7%). The mean duration of follow-up was 8.2 +/- 7.9 (ranging 0.3-29) months. Therapeutic measures included anti-Acanthamoeba medications (5/9 for nCL, 8/15 for CL), penetrating keratoplasty due to uncontrolled infections (1/9 for nCL, 2/15 for CL) and corneal perforation (1/9 for nCL), and enucleation due to endophthalmitis (1/9 for CL). At the last follow-up visit, the CL [corrected] group had slightly better visual acuity (55.5% vs 66.7%). In conclusion, AK among patients who do not use contact lenses may have a delayed diagnosis, resulted in more severe ocular manifestations and poorer prognosis. Physicians should be aware of Acanthamoeba infection as a cause of keratitis in any patient, not just contact lens wearers. Long periods of follow-up are recommended to observe for recurrent episodes and proper management of AK patients.