Fig. 26.3 The equator. In this eye the presence of the vortex vein and the lighter color of the retina peripheral to the equator are clearly visible. The laser cerclage is being completed so that the posterior border of the treatment ring is central to the equator (see more in

Sect. 30.3.3)

•Equator.23 This is an important, although ill-defined, landmark.24 The vortex veins and occasionally the different coloration of the fundus help identify it (see below and Fig. 26.3).

•Maculopapillary bundle. The area between the fovea and the optic disc, containing the most crucial nerve fibers, those responsible for central vision.

•Peripheral retina. A ring of ~15 mm width, extending from the equator to the ora serrata.

•The long posterior ciliary nerves,25 along with the long ciliary arteries at the 3 and 9 o’clock meridians, run intrascleral before reaching the suprachoroidal space roughly at the equator.

26.1.4 Anterior Segment Dimensions

•The AC depth is 3.15 mm.

•The diameter of the lens is 10 mm. It is 4 mm thick at age 20, increasing to 4.7 mm by age 60.

– The thickness of the lens capsule is 4–24 μ, thinnest in the center.

26.2External Anatomy for the VR Surgeon

The external anterio-posterior diameter of the eye is ~24 mm; the internal is 22 mm. The sclera is thickest at the insertion of the optic disc (1.2 mm) and thinnest (0.3 mm) at the insertion of the extraocular muscles; it is 0.5 mm at the equator and 0.8 mm at the limbus.

23That is, the largest circumference of the globe in the frontal plane.

24Crucially important for the surgeon when a PVD is created (see Sect. 27.5.1).

25Named “long uveal nerves” in a new terminology. These are not retinal structures, but their location justifies discussing them here.