Infections vs. Inflammation
BY TIMOTHY MCMAHON, OD
In my last column, I gave you a scenario of a patient with a 1.5mm x 1.5mm infiltrate with an overlying epithelial defect. I then guided you into infectious ulcer management strategies. I skipped over the tough part--namely how does one make the decision to treat the case as a likely infectious process vs. a more purely inflammatory process? This quandary is an all too common one and one where I have been thoroughly disappointed in the lack of a common approach.
skipped over the tough part namely how do you make the decision to treat the case as a likely infectious process vs. a more purely inflammatory process? This quandary is all too common, and I have been disappointed in the lack of a common approach.
I attempt to use the weight of the evidence in segregating the picture into an infectious process or a non-infectious process. I do this because the management strategies are different. Key features to look for are in Table 1.
Generally, an infiltrate less than 2mm located outside the central 6mm (diameter) of the cornea, with no epithelial defect, being a focal infiltrate only, with minimal injection and no anterior chamber response will push the diagnosis in favor of an inflammatory process. In this case, I would remove the lens and, depending on the intensity of the infiltrate, I might add a topical steroid, such as Lotemax (loteprednol etabonate, Bausch & Lomb) or Vexol (rimexolone, Alcon).
On the other hand, the more infectious signs and symptoms one encounters the more cautious one must be. (See Table 1).
TABLE 1: Signs and Symptoms Suggestive of an Infectious Process
|MORE LIKELY INFECTIOUS||LESS LIKELY INFECTIOUS|
|2+ or greater pain||No pain|
|Infiltrate located centrally||Infiltrate located peripherally|
|Infiltrate greater than 1.5mm||Tiny infiltrate|
|2+or greater anterior chamber cells||No anterior chamber cells|
|No epithelial defect|
|Epithelial defect over the infiltrate|
|2+ or greater limbal conjunctival injection||No limbal injection|
|2+ or greater diffuse conjunctival injection||Mild diffuse injection|
|2+ or greater diffuse infiltrate||No diffuse infiltrate|
What to Do
The more signs and symptoms that come from the left-hand column, the greater the likelihood that you are dealing with an infectious process and should proceed accordingly. Those features from the top half of the table are more important. If one or more are present, I will think of the process as infectious and will proceed as discussed in my previous column. If only signs and symptoms from the bottom half of the table are present, I will look for several to be present before leaning towards an infectious process.
Lastly, you will notice that the presence of an epithelial defect is in the lower portion of the table. It is true that infectious ulcers will almost always have an associated epithelial defect, unfortunately so do many non-infectious corneal infiltrates found in contact lens wearers. Though it is a powerful clinical sign and has a high level of sensitivity for an infectious process, an epithelial defect has a relatively low specificity for such a process, reducing its usefulness in the differential diagnosis. More powerful still is the absence of an epithelial defect, which most often signals a non-infectious process. Unfortunately, this fact is not uniformly true, in that non-ulcerative bacterial keratitis in contact lens wearers has been reported. In the end, experience and clinical judgement will prevail.
Dr. McMahon is a professor and Director of the Contact Lens Service at the University of Illinois at Chicago Dept. of Ophthalmology & Visual Sciences.