Table 5

Significant predictors for requiring surgery following failure of primary treatment of suspected microbial keratitis

CharacteristicsPrimary treatment failure requiring surgeryRisk ratio95% CIp Value
“Crude” estimates of risk ratio with no adjustment for confounding factors
Age 60+ years10/4240.0<0.001
Age < 60 years0/760.0
Culture positive ulcer >5 mm2 7/2626.98.32.3–29.7<0.001
Other ulcers3/923.3
Hypopyon present5/1533.36.92.3–20.90.003
Hypopyon absent5/1034.9
Previous corneal disease8/3821.18.41.9–37.80.002
No previous corneal disease2/802.5
Topical steroids before diagnosis5/1926.35.21.7–16.30.01
No prior steroid5/995.1
In the age group 60+ years old
Culture positive ulcers9/2437.56.70.94–48.60.026
Other ulcers1/175.6
Previous corneal disease8/2138.14.00.96–16.70.032
No previous corneal disease2/199.5
  • In the 60+ year old group, presence of hypopyon was a borderline risk factor (RR 2.5 (0.9–7.1), exact p=0.117), as was the presence of large culture positive ulcers (RR 2.8 (0.8 9.5), exact p=0.143). There were only 10 cases requiring surgery, all in the older age group. The small sample had little power in detecting significant predictors in regression analysis with adjustment for confounding factors, none was detected.