Fig. 26—Showing how to scrape the choroid free from the sclerotic near the optic nerve.
To remove the remaining part of the first coat is a little more difficult, and needs a little more care. Hold the optic nerve in the left hand, and pull it so that the sclerotic will pull away from the choroid. Then, using the cutting edge of the scalpel, scrape the choroid loose from the sclerotic close up to the entrance of the optic nerve. ([Fig. 26].) Do not separate the optic nerve from the choroid. Cut away the remainder of the sclerotic close up to the optic nerve and the choroid will be free. ([Fig. 27].)
Fig. 27—Showing the choroid, the optic nerve still attached, the ciliary ring, and the ciliary nerves.
Fig. 28—Showing method of inserting scalpel in order to loosen the lens and cut through the vitreous.
To get a perfect specimen and completely isolated choroid, it must be emptied of its contents. Insert the scalpel between the lens and the iris, force it on through, and in such a manner as to keep the scalpel close to the ciliary processes. ([Fig. 28].) Cut the vitreous around the processes. Push the scalpel further into the vitreous, and cut out the central part of it, just as one would cut out the core of an apple. ([Fig. 29].) Remove the scalpel, pick out the lens and the cut centre of the vitreous with the broad-point tweezers, holding the choroid a trifle suspended by the optic nerve. The remaining part of the vitreous may be broken down by cutting with the scalpel, and by squeezing and crushing with the fingers of both hands. ([Fig. 30].) The choroid will be tough enough to stand this treatment provided the pupil is left clear and open to prevent inter-choroidal pressure. After the vitreous has been removed the choroid will be left in a greatly collapsed condition. Dropping it into water and letting it fill up will make it resume its original shape immediately. The retina does not always come out with the vitreous. In such a case, the tweezers may be used to pick out the retina when the choroid is in a collapsed condition.
Fig. 29—Taking out the lens and “core” of the vitreous.
