What is the diameter of the human eye?
Human eye
Dimensions typically differ among adults by only one or two millimetres, remarkably consistent across different ethnicities. The vertical measure, generally less than the horizontal, is about 24 mm. The transverse size of a human adult eye is approximately 24.2 mm and the sagittal size is  23.7 mm with no significant difference between sexes and age groups. Strong correlation has been found between the transverse diameter and the width of the orbit (r = 0.88). The typical adult eye has an anterior to posterior diameter of 24 millimetres, a volume of six cubic centimetres (0.4 cu. in.), and a mass of 7.5 grams (weight of 0.25 oz.)..
Optography
An issue that Kühne encountered when attempting to produce an image from a human eye is that the size of the fovea centralis, the actual focal point of the image on the retina, is very small (about 1.5 millimetres). Kühne had considerably more success producing optograms from animals such as rabbits and frogs, and the Reif image ended up being the only known "human optogram". The original image from Reif's eye no longer exists, apart from a simple line drawing of the shape in Kühne's 1881 paper "Observations for Anatomy and Physiology of the Retina".