Dive mask rx compensation?

[MHBaker]

Good day,

I recently had a question directed to me; Would you compensate an rx for dive mask or swim goggles based on index of water or air?

Not sure? Would it make a difference?

[lensgrinder]

If the front curve of the lens is not plano and since it is in water yes you would compensate the front curve. You would not compensate the back, because it is still surrounded by air.

D=nr-ni/r
D = Dioptric Value
nr = index of the refracting medium(in this case material of lens)
ni = index that light is incedent on(in this case it would be water)
r = radius of curvature in meters

[HarryChiling]

I think it might help with general questions about lenses in other surrounding media if we were to teach the Diopter as:

n_r=refracting media
n_i=inceident media
r=radius of curvature
K=curvature (1/r)

D=(n_r-n_i)/r

instead of what most have come to know it or see it:

D=(n_r-1)/r

I would also recommend that opticians learn that the curvature is a sepearate component in and of itself so:

D=(n_r-n_i)*K

The reason for the last is that in many research papers I have read the curvature is a seperate component and often can be confusink if the it is not known as the inverse radius.