Treasury of Optics

12. The centers of the spheres of the whole eye, the crystalline lens, both surfaces of the cornea, and the convex surface of the aqueous humor, are one single point. 7 p 3.

And since it has been declared [6.8 n] that the center of the cornea and the center of the anterior surface of the glacialis crystalline lens both lie upon that line, and both are further removed in depth from the center of the uvea, it is better that the center of the anterior surface of the glacialis should be the center of the cornea itself, so that the centers of all the surfaces opposite the foramen of the uvea are one common point. Thus, all lines emerging from the center to the surface of the eye will be perpendicular to all the surfaces opposite the foramen. From this it will be explained later, in our discussion on the quality of vision, that the center of the surface of the cornea and the center of the anterior surface of the glacialis is one common center. Therefore, the surfaces of the membranes of the eye, opposite the foramen of the uvea, are spherical surfaces whose center is one common point.

13. In the whole eye, whether in motion or at rest, the position of the parts remains stable. 25 p 3. The same, 9 n.

And again, because this center is the center of the manifest surface of the eye, continuous with the surface containing the whole eye, and the whole eye is round—except for what is missing from the completion of the sphere of the consolidating fat original: "pinguēdinis cõsolidatiuæ"; likely referring to the sclera or connective tissue from the anterior part of the eye—this defect does not cause a difference in the motion of the eye, since it does not touch the concavity of the bone. Therefore, this center will be the center of the whole eye; thus, it is within the whole eye. Therefore, when the surface of the membranes of the eye, opposite the foramen of the uvea, changes, it remains within the whole eye. When the eye moves, the point of the eye, which is the center of the surfaces of the membranes of the eye, will not change, nor will its position change relative to these surfaces; rather, it guards its position. For when the eye moves, it does not move except as a whole, and the position of the parts of the whole relative to each other does not change during motion. And this center is internal. Therefore, its position does not change during its motion. Similarly, the position of the membranes does not change in relation to the whole eye, that is, in relation to the motion of the eye itself. Therefore, the position of this center relative to the surface of the membranes of the eye does not change, neither in motion nor in rest. It has already been declared [5 n] that the declination of the nerve during the motion of the eye and during rest occurs only at the foramen of the eye, which is in the concavity of the bone: because it is only at the posterior of the whole eye. The declination of the nerve during the motion of the eye and during rest is only from the posterior of its center, and the position of the parts of the whole eye relative to each other does not change, neither in motion nor in rest. Therefore, the position of the centers of the membranes of the eye relative to the whole eye does not change, neither in the motion of the eye nor in rest. The line passing through the center does not change its place or position relative to the whole eye, nor relative to its parts, namely, neither in motion nor in rest. And since the position of this line does not change relative to the whole eye, nor relative to its parts: the position of this line does not change relative to the surface of the circle of consolidation, nor relative to the circumference.

A schematic anatomical diagram depicts the human eye in cross-section. The layers of the eye are visible, including the Cornea, Uuea, Tunica aranea, and Tunica adherens. The internal humors are labeled as humor aqueus (aqueous humor), humor vitreus (vitreous humor), and the lens as Crystallina (glacialis). The optic nerve is shown at the bottom, surrounded by membranes and eye muscles.

And this circle is the extremity of the concavity of the nerve. Therefore, the position of its surface relative to the surface of the concavity of the nerve is a similar position. And the declination of the pyramidal part of the nerve upon the surface of this circle is a similar declination, since the position of the glacialis relative to this nerve is a similar position, and the position of the parts of the eye does not change relative to each other. Therefore, the surface of the concavity of the nerve, from the location of the circumference of the circle of consolidation to the location of the declination of the nerve (which is the pyramidal part), does not change its position relative to the whole eye, nor relative to the circle of consolidation. And it has already been declared [5 n] that the position of the line passing through all the centers does not change relative to the circle of consolidation, and that it extends into the middle of the concavity of the nerve. And since the position of this line does not change relative to the circle of consolidation, nor does the surface of the concavity of the nerve (which is from the location of the circumference of the circle of consolidation to the location of the declination) change its position relative to the circle of consolidation: therefore, this line does not change its position relative to the concavity of the nerve until it reaches the location of the declination. Therefore, the line that passes through the centers of the membranes passes through the center of consolidation; it is erect upon it at right angles, and it extends into the middle of the concavity of the pyramidal nerve until it reaches the location of the declination of the nerve. Its position will always be the same relative to the surface of the concavity of the nerve (which is within the whole eye), relative to all parts of the eye, and relative to all surfaces of the membranes of the eye, and it does not change either in the motion of the eye or in...