How unique are your eyes?

As an optometrist, I am sometimes asked in the consulting room whether peoples eye are ‘generally the same’.

This got me thinking about the number of different lenses we use to examine peoples eyes and and the possibility that each pair truly is unique.

So if we consider the possible combinations (roughly).

• Sphere (range +20.00 to -30.00 in 0.25 steps) ~ 200 options
• Cyl (range +6.00 to -6.00 in 0.25 steps) ~ 48 options
• Cyl axis (range 0 to 180 in 1 degree steps) ~ 180 options
• Add (range +0.75 to +3.50 in 0.25 steps) ~ 11 options
• Number of eyes ~ 2

Therefore, we can calculate the odds of a spectacle or goggle prescription being unique at nearly 1 in 38,000,000 (200x48x180x11x2).

This may not be 100% statistically or scientifically accurate, but it gives a good feel for just how individual your eyes are.

But I am sure you all knew you were unique already.