JAN 16, 2009
Cornea/External Disease
The results of this small case series suggest that anterior segment optical coherence tomography (AS OCT) can play a valuable role in the clinical assessment of microbial keratitis and monitoring of the disease's course.
The study's authors prospectively scanned with AS OCT (Visante OCT, Carl Zeiss Meditec, Inc.) seven eyes of seven patients with suspected microbial keratitis upon presentation and at two follow-up visits. They took scans of the same area of corneal infiltration at each visit with the scanning beam running through the meridian that crossed the center of the infiltration. The subjects also received standard clinical exams and treatment based on slit-lamp findings.
In the initial stages of microbial keratitis, the cornea is thickened at the infiltrated area even in mild cases. Corneal thickness decreases as the infection and inflammation resolves, with scar tissue developing and affected cornea becoming thinner than adjacent healthy tissue in the later disease stages. The authors were able to see corneal infiltration as a hyper-reflective area in the corneal stroma on high-resolution AS OCT scans and measure changes over time.
In six of the cases, they were able to measure corneal and infiltrate thickness with the OCT device's caliper software tools. Measurements could not be made because of thick inflammatory plaque attached to the endothelium in one case, so they measured the width of the plaque on serial scans instead.
The authors emphasized that AS OCT can aid in microbial keratitis case assessment but must be interpreted in the context of the clinical situation and exam results. This is well illustrated by one of the cases, in which AS OCT detected corneal thinning earlier than did clinical examination but this thinning was not associated with the infection's resolution and the patient subsequently underwent penetrating keratoplasty.