Specimen Orientation

Globes may be oriented according to the location of the extraocular muscles and of the long posterior ciliary arteries and nerves, which are located in the horizontal meridian. The medial, inferior, lateral, and superior rectus muscles insert progressively farther from the limbus. Locating the inferior oblique muscle insertion relative to the optic nerve is helpful in distinguishing between a right eye and a left eye. The inferior oblique inserts on the sclera temporally over the macula, with its fibers running inferiorly (Fig 2-1). Once the laterality of the eye is determined, accurate location of ocular lesions is possible.

Figure 2-1 Posterior view of the right globe. N = nasal; T = temporal. A, Diagram. B, Macroscopic photograph. Note that the posterior ciliary artery and nerve appear as a subtle blue-gray line as they pass through the sclera. This marks the horizontal meridian of the globe. Also note that the rectus muscle insertions are not present. The rectus muscles are typically incised at their scleral insertion during enucleation so that they may be attached to the orbital implant.

(Part A modified by Cyndie C. H. Wooley from an illustration by Thomas A. Weingeist, MD, PhD; part B courtesy of Nasreen A. Syed, MD.)

When eyelid or conjunctival tissue is sent for pathologic evaluation, it may be important in some clinical situations to evaluate the resection margins (ie, determine whether the lesion is present in the margins of resection). Note that the smaller a tissue sample is, the more difficult it will be to accurately assess the surgical margins. If the tissue rolls up or bunches, it can be difficult to orient. Furthermore, once the tissue is fixed in formalin, it cannot be reshaped. For these reasons, when the biopsy specimen is obtained, it should be unrolled and placed on a dry piece of filter paper or similar absorptive to keep it flat. The tissue should be allowed to adhere to the paper for several seconds, and then the paper with the tissue can be floated in a container of formalin.

Figure 2-2 Marking the orientation of excised tissue for analysis of surgical margins. A, Sutures, 1 long and 1 short, are placed 90° apart. B, The tissue is carefully placed on a piece of filter paper and allowed to adhere for several seconds before it is placed in a container of formalin.

(Illustration by Cyndie C. H. Wooley.)

To properly orient a specimen, the pathologist needs landmarks. Therefore, before the biopsy tissue is placed in formalin, it must be marked in some way to enable correct orientation of the surgical margins; a corresponding diagram indicating the meaning of the marks must also be created. The best way to mark tissue is to use sutures (long and short) positioned 90° apart (Fig 2-2). Small sutures may look large with surgical magnification, but they are difficult to see in the pathology laboratory; thus, sutures that are visible with the naked eye should be used. Ink is not a good way to mark tissue because most types of ink, including permanent marker and surgical marking ink, dissolve in formalin.

Labeling both the specimen container and the paperwork with 2 patient identifiers is mandatory before submission to the pathology laboratory. The diagram should be submitted along with the specimen.

Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.