First, please let me apologize for the harsh and profane comments that I directed towards you many months ago regarding one of your posts. It was inappropriate and I will not insult you again. Also, thanks for not blocking me after my outburst.
Regarding your question, there is an excellent article in the September 2011 issue of Review of Optometry
that answers practically any question you could have on this topic. It is entitled Bacterial vs. Viral: Name That Infection!
and was written by Aaron Bronner, OD.
I just finished reading the piece and it is an excellent reference to learn or re-learn about the differential diagnosis of these two very different conditions.
As my friend Tom has correctly pointed out, these lesions can be similar in appearance until the clinical presentation gets worse. In other words, the pre-dendritic stage of herpes simplex is often overlooked or vague enough to create clinical confusion.
To quote from the article:
"Unfortunately, what we see more often are non-specific findings, such as injection, minimal mucous discharge, papillae or follicles (or both) and some degree of corneal infiltration, running the gamut from diffuse stromal white blood cells to a dense focal area of infiltration either with or without an overlying epithelial defect. When faced with non-specific findings, it is up to us to come to a reasonable diagnosis and form an appropriate treatment plan."
After I read the article, I was reminded of the specific regions of the cornea that play a role in the immune response to infection. In my own Review of Optometry
article entitled Understanding Specular Microscopy
from several years ago, I touched on the differences in endothelial anatomy between the central corneal region and the peripheral corneal region. Well, the cornea also has two distinct immunologic regions - the limbal/peripheral zone and the central zone.
The location-dependent duality of corneal immunity is the source of some fairly common differences between lesions of the periphery and lesions of the paracentral zone. For example, when the ulcer is caused by the herpes virus, if the insult is at or near the corneal periphery, the proximity to the limbus allows the immune system to more effectively contain viral activity and the characteristic dendritic appearance never develops or it may be obscured by any type of corneal infiltration.
I believe that is an important piece of information to assist in your medical decision-making.
I could go on and on, but I would simply encourage any optometrist that wants to be well-read on the question that Dr. Bova posed to just read the article and go from there...
This is a picture from one of my patients with herpes simplex. The presentation can change depending on the stage of the disease and the patient's response to treatment.
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