Understanding Corrective Lenses: Examining Reversed Prescriptions

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Discussion Overview

The discussion revolves around understanding corrective lenses, particularly in the context of nearsightedness and the effects of reversed prescriptions. Participants explore how wearing glasses with a prescription that is the opposite of a person's corrective lenses might provide insight into their uncorrected vision.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether wearing glasses with a reversed prescription would help them understand their girlfriend's uncorrected vision.
  • Another participant suggests that diopter powers are additive, proposing that wearing +3.0 diopter glasses could simulate the uncorrected vision of someone with -3.0 diopters.
  • It is noted that complications such as astigmatism and differences in individual eye focus may affect the accuracy of this approximation.
  • A suggestion is made to compare the distances at which both individuals can read, such as street signs, to gain a better understanding of the differences in vision.
  • One participant acknowledges the presence of a prism in the girlfriend's prescription, indicating a potential complication not addressed by standard reading glasses.
  • Another participant mentions that the presence of a prism may suggest astigmatism and recommends testing the glasses by rotating them to observe the effects on vision.

Areas of Agreement / Disagreement

Participants express varying degrees of agreement regarding the additive nature of diopter powers, but there is no consensus on the effectiveness of using reading glasses to simulate uncorrected vision. Complications such as astigmatism and the presence of a prism introduce uncertainty into the discussion.

Contextual Notes

Limitations include the assumption that diopter powers are strictly additive and the potential variability in individual eye conditions, such as astigmatism and differences in focus range.

Who May Find This Useful

This discussion may be of interest to individuals seeking to understand corrective lenses, those curious about the effects of different prescriptions, and anyone exploring the implications of vision correction on daily activities.

Flyboy
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My girlfriend has started wearing corrective lenses to address some nearsightedness and I'm not fully understanding what she's going through, or what the difference is for her with and without glasses. I was curious if you basically reversed the prescription of the lenses, would it take my normal vision and give me an idea of what she's seeing without the lenses?
 
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I believe that to first approximation that the diopter powers of lenses are additive. So if your friend has a correction of, say, -3.0 diopters you should be able to get a sense for what her uncorrected eyesight is like by wearing +3.0 "reading" glasses. You can find those at a pharmacy. They don't require a prescription and they are inexpensive.

Or maybe I'm wrong.
 
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JT Smith said:
Or maybe I'm wrong.
Nope, you had it right - diopters add. However, there are complicating factors. She may have some astigmatism. Her eyes might have different range of focus from yours, so your eyes might partially compensate for the reading glasses.

A better test is to compare the distances at which you and she can read, for example, street signs.
 
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JT Smith said:
You can find those at a pharmacy.
And they are typically just sitting in open display on a shelf or at a small kiosk. They are meant to be tried on, so you don't even have to buy a pair to get an idea. Just look at your GF's Rx and as mentioned above, pick the pair or reading glasses with the complementary Rx in diopters and look around as you stand there. Can you say what her optical Rx is?
 
Not off the top of my head, wanted to make sure I was understanding the physics right.

I do know she has a little prism to hers, which I don't think reading glasses have, but the reading glasses is a good idea for an approximation.
 
If 'prism', that suggests a degree of astigmatism. Try rotating her glasses while looking through them. The result may be disconcerting as eg verticals blur vs horizontals, then vice-versa...
 

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