Table 3. Prevalence and odds ratio of demographic characteristics and potential risk factors for infection in Acanthamoeba keratitis cases and controls who wore rigid gas-permeable lenses, stratified by orthokeratology or therapeutic use — United States, 2005–2011.
| Non-Orthokeratology | Orthokeratology | ||||
|---|---|---|---|---|---|
| Cases (N=28) |
Controls (N=17) |
Cases (N=9) |
Controls (N=0) |
||
| Demographic characteristic or exposure |
n (%) | n (%) | Unadjusted odds ratio (p- value)* |
n (%) | n (%) |
| Age | |||||
| 25 years or younger | 2/28 (7.1) | 0 | undefined (p=0.23) |
4/9 (44.4) | 0 |
| 26–55 years | 6/28 (21.4) | 8/16 (50.0) | referent | 2/9 (22.2) | 0 |
| 56 years or older | 20/28 (71.4) | 8/16 (50.0) | 3.3 (p=0. 07) | 3/9 (33.3) | 0 |
|
Duration of daily
lens wear |
|||||
| <12 hrs./day | 12/28 (42.9) | 4/17 (23.5) | 2.8 (p=0.12) | 6/9 (66.7) | 0 |
| >12-16 hrs./day | 14/28 (50.0) | 13/17 (76.5) |
referent | 2/9 (22.2) | 0 |
| >16 hrs./day | 2/28 (7.1) | 0 | undefined (p=0.30) |
1/9 (11.1) | 0 |
|
Overnight contact
wear |
|||||
| Never slept with lenses in |
22/27 (81.5) | 16/17 (94.1) |
referent | 2/9 (22.2) | 0 |
| Slept with lenses in some nights |
5/27 (18.5) | 1/17 (5.9) | 3.6 (p=0.24) | 1/9 (11.1) | 0 |
| Slept with lenses in every night |
0 | 0 | 6/9 (66.7) | 0 | |
| Tap water source | |||||
| Municipal water | 25/27 (92.6) | 10/16 (62.5) |
7.5 (p=0.02)** | 6/8 (87.5) | 0 |
| Private well | 2/27 (7.4) | 6/16 (37.5) | referent | 1/8 (12.5) | 0 |
| Tap water exposure | |||||
| Ever used tap water to store lenses |
14/27 (51.9) | 1/17 (5.9) | 17.2 (p=0.002)** |
4/9 (44.4) | 0 |
| Lens hygiene | |||||
| Ever topped off solution in lens case |
18/27 (66.7) | 5/17 (29.4) | 4.8 (p=0.02)** | 7/9 (77.8) | 0 |