Question

A person's left eye has a near point of 43 cm and requires eyeglasses to correct their vision.

a) What would the prescription for the left eye?

b) A 9.0 mm base curve (radius of curvature) will best fit the person's cornea. Using the material with index of refractive 1.422, what should be the radius of curvature (include the correct sign) fo the other side of the lens?

c) What is their new far point after wearing the contact lens?

Answer 1

A) for an healthy eye near point must be at 25 cm so to choose lens we have to shift this near point from 43 cm to 25cm

So, object distance p=- 43cm

and image distance q= -25 cm

So from lens maker formula

So focal length

f = -59.72 cm

So power of lens = 1/f = -0.0167 Dioptre

2) So focal length can be written as

n = 1.422

R1 = 9 cm

R2= -R

So solving for R2 we get

R2 = -13.97 cm for the other side

C) so near far point is now at 25 cm from left eye