The Duke Elder exam commonly tests your knowledge on certain dimensions relating to the eye and surrounding structures. This article contains the key facts you should know relating to dimensions.
The spiral of Tillaux describes an imaginary line connecting the insertions of the recti muscles of the eye. Note that the insertion distances are given in millimetres and are maximum values. Insertion distances vary in different individuals.
The diagram below shows the insertion distances of the recti muscles in the right eye.
Diagram showing the insertion distances of the recti muscles in the eye.
The sclera is thicker in males than in females.
A: The Sclera is thinnest at the insertion of extra ocular muscles (0.3 mm).
B: It is thickest near the optic nerve, where it is approximately 1 mm in thickness.
C: Sclera gradually thickens towards cornea and at limbus the thickness of sclera is 0.83 mm.
Diagram showing the thickness of the sclera around the globe.
Diagram showing the anatomical course of the optic nerve.