Use of agar in ophthalmic pathology - A technique to improve the handling and diagnosis of temporal artery biopsies, subfoveal membranes, lens capsules, and other ocular tissues

Design: Prospective laboratory methodology study. Purpose: Certain tissues, by virtue of their shape and extreme thinness or pliability, are difficult to position correctly during routine paraffin emb edding to provide the optimal orientation for histopathologic studies. Biop sy specimens from temporal arteries must be sampled at different points alo ng the length of the artery. Other tissues such as subfoveal neovascular me mbranes and fragments of lens capsule lack the thickness and rigidity to be positioned on edge to yield cross-sectional views. The authors' technique improves the orientation and thereby maximizes the histologic information o btained from such specimens. Methods and Materials: From January 1, 1990, to April 30, 1999, the authors studied 500 consecutive temporal artery biopsy specimens and 200 successiv e subfoveal neovascular membranes. Results: Cutting a 20-mm cylindrical fragment of temporal artery at 1- to 1 ,5-mm intervals yielded approximately 13 to 20 cross-sections along the len gth of the artery. When the specimens were positioned together and embedded in agar, the pathologist could easily study multiple cross-sections of the artery. Additionally, using the agar technique, the authors were able to o btain cross-sections of other specimens submitted, such as subfoveal neovas cular membranes, and studied each of the different layers to evaluate the d isease process. By the same method, the authors placed small fragments of l ens capsule with underlying cortex on edge and readily identified short, gr am-positive coccobacilli consistent with Propionibacterium acnes endophthal mitis. Conclusion: The agar technique can greatly improve the quality of diagnosti c information gleaned from temporal artery biopsy specimens and other small tissue samples.