Optics of Low Vision Aids

Question 1

How do low vision aids work

Answer 1

by presenting the patient with a magnified view of the object

Question 2

Which lens can be used as a magnifying lens

Answer 2

Convex lens

Question 3

What is the Galilean system composed of

Answer 3

A convex objective and concave eyepiece lens separated by a distance of their focal lengths

Question 4

What are the properties of image formed by the Galilean system

Answer 4

Erect, magnified image

Question 5

Galilean system angular magnification formula

Answer 5

M=Fe/Fo

Fe= power of eyepiece lens in dioptres
Fo= power of objective lens in dioptres

Question 6

What are some limitations of optical magnifying devices

Answer 6

1) High magnification= reduced field of view
2) Object has to be held close to the eye
3) Magnification means depth of focus is reduced

Therefore, the aim of the prescriber should be to provide the lowest magnification that is adequate for the patient’s requirements in a useable and acceptable form