Without glasses, a person needs to have his eyes 35.0 cm from a book to read com

Question

Without glasses, a person needs to have his eyes 35.0 cm from a book to read comfortably and can focus clearly on distant objects up to 2.75 m away, but no farther. A typical eye should be able to focus on objects that are between 25.0 (the near point) and infinity (the far point) from the eye.

a. What type of correcting lenses does the person need: single focal length or bifocals? Why?

b. What focal length(s) should the optometrist prescribe from the correcting contact lens(es)?

c. What is the power, in diopters, of the correcting lens(es)?

Please provide clear, step by step solutions. Thank you!

Explanation / Answer

a) THere are different types of correcting lenses opted depending on whether the person is nearsighted or far sighted

Single focal length is used for a person with near sightedness.They contain the same amount of vision correction through out.

Bifocal is used to corect both near and far sightedness since they contain two prescription on the same lens.

b) For bifocal lenses the focal length would be minimum 12-18 inches from the face and distance of 10 feet and beyond.

c) Positive and negative signs are used to express the power of lenses in diaopter

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