Processing Of Ocular Specimens

FIXATION, ORIENTATION, DOCUMENTATION OF LESIONS AND SECTIONING The enucleated eye is placed in 20-25 times its volume of 10% buffered formalin for 48 h of fixation. The neck of the container should be approximately twice the diameter of the globe for ease of removal of the specimen (Fig. 7-4). Injection of fixative into the globe is not necessary and should be avoided as it introduces artifact into the globe.

If the eye and orbital contents have been removed in toto, the eye should be dissected from the orbital contents and placed in a separate container because otherwise, its fixation will be delayed. The orbital contents are fixed separately.

After 48 h fixation, the eye is rinsed in running water to allow easier handling by persons sensitive to formalin. It is then placed in 60% alcohol until it is sectioned, a period of 16-20 h.

Orientation with regard to side is determined by observation of the following (Fig. 7-7):

1. The horizontal plane is characterized by the posterior ciliary vessels; the more prominent vessels lie on the nasal side.

2. The temporal side is characterized by the insertion of the inferior oblique muscle, which is usually fleshy and extends inferiorly from the optic nerve.

3. The superior aspect is characterized by the tendinous insertion of the superior oblique muscle, which underlies the superior rectus muscle.

The superior pole is marked with a grease pencil to allow continued quick orientation with subsequent handling (Fig. 7-8). The anteroposterior, horizontal, and vertical planes are measured with a caliper (Fig. 7-9). If the presence of calcium, bone, or a foreign body is suspected, a roentgenogram of the globe is helpful (Fig. 7-10).

A phthisical eye contains bone and thus requires decalcification. This is performed using Formic Acid Decal which is a 20% solution of formic acid in 10% neutral buffered formalin. Orbital bone requires a stronger decalcification solution. The rapid method with Decalcifier ll (Surgipath) is effective but once the bone is placed in this solution, it must be examined every 2 h and cannot be left in the solution overnight. Adequate decalcification is determined by repeat roentgenograms.

The external appearance of the eye should be documented. Surgical and accidental penetrating or perforating wounds need to be noted. Transillumination of the globe is then performed. If a defect in transillumination is present, such as may be caused by an intraocular tumor, the area is outlined with a grease pencil, the size of the opacity determined, and the plane of section is made accordingly to give the best information.

Fig. 7-5. Scleral tissue for transplantation. Left, Sclera sealed in double plastic container is placed within containing jacket (Steri-Lok package) for sterilization. Note glass bead, which is clear before radiation process. Right, Upper package contains nonsterile sclera with a clear glass bead that indicates the tissue has not yet been exposed to radiation and is therefore not sterile. Lower package contains sterile sclera with darkened bead, which indicates exposure to radiation.

Fig. 7-5. Scleral tissue for transplantation. Left, Sclera sealed in double plastic container is placed within containing jacket (Steri-Lok package) for sterilization. Note glass bead, which is clear before radiation process. Right, Upper package contains nonsterile sclera with a clear glass bead that indicates the tissue has not yet been exposed to radiation and is therefore not sterile. Lower package contains sterile sclera with darkened bead, which indicates exposure to radiation.

Lacrimal gland

Left orbit viewed from in front ...

Fig. 7-6. Diagram of left orbit viewed from front. Note position of lacrimal gland in lacrimal fossa.

A transverse section of the optic nerve is made only if the length of the optic nerve is such that the back of the globe will not be opened by the cut (Fig. 7-11).

Sectioning is performed on a piece of dental wax, to which the escaping vitreous does not adhere; thus the attachment of the retina to the choroid is maintained. The eye is positioned so that the cornea is against the wax and the optic nerve projects upwards. The inferior 'cap' or calotte is removed by placing a razor blade immediately abutting the inferior aspect of the optic nerve (Fig. 7-12). With a smooth motion, the blade is directed toward the limbal edge of the cornea. The inferior calotte, together with the remaining globe, is examined in 60% alcohol under a dissecting microscope (Fig. 7-13). Pathological conditions and photography are recorded at this time.

Most eyes are sectioned in the horizontal plane (Fig. 7-14). This is known as the PO section (pupil/optic disc) and will show the macula as well as the optic disc and pupil. For eyes that have been traumatized or contain a neoplasm, such a horizontal cut may not show the pathology to advantage and an oblique or vertical cut may be required.

The larger portion of the globe with the superior pole is then placed with its flat surface on the dental wax. The razor blade is placed immediately adjacent to the optic nerve and the second cut is made parallel to the first; this mid-section of the globe, approx 3 mm thick, is submitted for processing. A diagram for sectioning the globes is shown in Fig. 7-15. The instruments used for sectioning are shown in Fig. 7-16.

Fig. 7-7. Eyes enucleated at autopsy. (A) Right eye. (B) Left eye. Note (a) optic nerve, (b) posterior ciliary vessels running horizontally, (c) inferior oblique muscle, (d) superior oblique muscle, and (e) rectus muscles.
Fig. 7-8. Left eye in position on piece of dental wax. Superior pole is marked with a grease pencil. Note inferior oblique muscle (a) and superior oblique muscle (b).
Fig. 7-9. Measurement of globe. Eye is measured in three planes: anteroposterior, horizontal, and vertical.
Fig. 7-10. Roentgenogram of globe showing foreign body (portion of bullet).

Fig. 7-12. Sectioning of globe. Eye is positioned with cornea facing down on dental wax and superior pole with grease pencil mark is to left. Razor blade is placed parallel to the horizontally running posterior ciliary vessels and immediately abutting the optic nerve. This cut removes the inferior calotte.

Fig. 7-11. Eye in position on dental wax. Blade in position for transverse section of optic nerve.

Fig. 7-12. Sectioning of globe. Eye is positioned with cornea facing down on dental wax and superior pole with grease pencil mark is to left. Razor blade is placed parallel to the horizontally running posterior ciliary vessels and immediately abutting the optic nerve. This cut removes the inferior calotte.

Fig. 7-13. Sectioned globe. Inferior calotte and remaining globe are placed in 60% alcohol and examined with a dissecting scope.
Fig. 7-15. Diagram demonstrating sectioning of the globe.
Fig. 7-16. Instruments used for sectioning globe. From left to right: glass bowl, tissue button, grease pencil, caliper, forceps, and razor blade. Piece of dental wax is in foreground.
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