A cataract-impaired lens in an eye may be surgically removed and replaced by a m

Question

A cataract-impaired lens in an eye may be surgically removed and replaced by a manufactured lens. The focal length required for the new lens is determined by the lens-to-retina distance, which is measured by a sonar-like device, and by the requirement that the implant provide for correct distance If the distance from lens to retina is 22.4 mm, calculate the required power of the implanted lens in diopters. (a) Since there is no accommodation and the implant allows for correct distance vision, a corrective lens for close work or reading must be used. Calculate the required power of the eyeglasses that will allow for clear vision at a distance of 25.0 cm. You may assume that the glasses are worn a distance of 2.00 cm from the eye. (b)

Explanation / Answer

According to the concept of the defects of vision

power of the lens P=(1/0.25-1/n.p)

Given that

distance from lens to retina f=22.4 mm=0.0224 m

now we find the power

power of the lens =-1/f=-1/0.0224=-44.6 D

now we find the power of the lens glass at a distance f=0.02 m

power =(1/0.25-1/0.02)=(4-50)=-46 Diopters

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