# Physiological Optics Question--darn math.

#### Eyegirl2k7

##### Bridget Jones here
7+ Year Member
15+ Year Member
Hi all,
I have an optics question from an assignment I'm doing. Rpames, if you're out there...you know what i'm talking about (Lecture 10-19 review).

The question is:
What is the depth of focus in diopters for an eye that perceives a clear retinal image for objects placed between 30-40 cm in front of the eye?

Since the clarity of image is between 30-40 cm, I converted that to diopters and said that the image is clear between -3.33 D and -2.50 D. Is it more complicated than that? Somehow i feel like it should b e.

Many thanks,
Eyegirl

#### cpw

##### It's a boy !!!
Moderator Emeritus
10+ Year Member
15+ Year Member
unless i remember incorrectly i do believe that's all you have to do... but it has been two years.. somebody back me up here

good to see you again eyegirl

#### Andrew_Doan

##### Doc, Author, Entrepreneur
Moderator Emeritus
15+ Year Member
Eyegirl2k7 said:
Hi all,
I have an optics question from an assignment I'm doing. Rpames, if you're out there...you know what i'm talking about (Lecture 10-19 review).

The question is:
What is the depth of focus in diopters for an eye that perceives a clear retinal image for objects placed between 30-40 cm in front of the eye?

Since the clarity of image is between 30-40 cm, I converted that to diopters and said that the image is clear between -3.33 D and -2.50 D. Is it more complicated than that? Somehow i feel like it should b e.

Many thanks,
Eyegirl
You got it. The eye is able to focus the object between -3.33 D and -2.50 D.

If they had added in a refractive error, i.e. -5.00 or + 5.00, and the accomodation of the eye then you could calculate the near and far points of the eye. In this case, it appears to be an emmetropic eye focusing on an object at 30 cm = 3.33 D and 40 cm = 2.50 D.

#### Eyegirl2k7

##### Bridget Jones here
7+ Year Member
15+ Year Member
Thanks, faithful SDNers!

I do not optics.

Eyegirl