Nearsighted correction lens

[FlowRate]

I found a thread similar to this one, but it didn't quite answer my question:

I know I could do the ray diagram, which I probably should, but I'm trying to figure out the "logic" behind this explanation for a Ptest question:

Myopic patients use a diverging lens to make distant images seem closer. "Since the lens is meant to bring distant objects closer, they
must also appear reduced in size to keep a reasonable proportion."

That seems super counter-intuitive to me. If you can't see something far away, wouldn't you want to enlarge the image so you could see it?


Thanks!


PS, this is totally unrelated to my question, but one more thing: What is the difference between CBT 8 and 8R? I can't seem to find the answer, all the posts I see assume that everyone knows the difference. (I surmise that 8r is a paper-test?)

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[FlowRate]

I hope it's okay if I bump this =)

 

[jikuty]

I can't answer your nearsightedness question, but I can tell you that 8R is the paper version of the test.

 

[FlowRate]

Thanks jikuty.

For anyone who may be interested in the answer, I think I "Get" it from this ray diagram:
http://www.antonine-education.co.uk.../Topic_2/topic_2__defects_of_vision_and_t.htm

(toward the bottom of the page).

When the diverging lens corrects the "rays" "given off" by a distant object (a distant object's real image), the resultant virtual image is formed "closer" to the eye (still on the other side of the lens) than the distant object. But, to achieve proper perspective, the distant image is now "closer," but "smaller." This is essentially what the quote I provided said, but it could have been a bit more meticulous with its reasoning.

=)

 

[wanderer]

Check this out: http://forums.studentdoctor.net/showthread.php?t=650082
Also, please edit your original post so that no one's AAMC (if that's where you got the question from) is ruined by seeing your answer ahead of time.

 

[FlowRate]

It's not from the AAMC, it's from EK 1h, for which I didn't see a thread (admittedly, I didn't search for one). Also, that is the thread I already found, and it was unhelpful to me for purposes of clarifying the logic in the answer explanation.

Thanks tho! =)

 

[wanderer]

If one is nearsighted and is trying to view a distant object, his lens will form an image in front of the retina. To make the image form on the retina the light rays have to be spread out and formed further back onto the retina. This must be done with a diverging lens.

I know this is a different explanation than EK's (which is pretty odd, imo) but it works.

 

[thebillsfan]

if you use a diverging lens to correct myopia, would the image formed on the retina be the same SIZE as the image that would be formed without myopia? alternatively, would it be the same size as the image formed in front of the retina in the uncorrected eye?