Difference between revisions of Close-up glasses
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→When are differentials worn
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== When are differentials worn == | == When are differentials worn == | ||
Standard EM advice is to wear differentials when looking at static focal planes (e.g. 2D planes like screens, books) at fixed distances for extended periods of time. It is okay to wear normalized in other contexts, such as when eating a meal, or looking at your conversation partners. It is also permitted to wear differentials in other close-up contexts based on personal preference, but there is no need to overdo normalized/differential glasses changes. (for example, there is no need to swap to differentials whenever someone walks up to you for a conversation) | |||
To determine if a close up activity is hurting your vision with the glasses you are using (differentials or normalized), it helps to have a point of comparison (like a line on a snellen chart), and to compare against that reference point before and after the activity in question. | |||
Read a book with differentials. Use your computer with differentials. | Read a book with differentials. Use your computer with differentials. | ||
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But for convenience, you might choose a threshold time and not change your glasses if it would be worn for less than that threshold. As an example, see the [[20-20-20 rule]] page. | But for convenience, you might choose a threshold time and not change your glasses if it would be worn for less than that threshold. As an example, see the [[20-20-20 rule]] page. | ||
'''What is "close" work?''' Norms minus diffs = the number of diopters you need to convert to find this answer. For example, if your normalized glasses are -5 and your differential glasses are -3.5, then you need to convert -1.5. You should be able to see 66.67cm with -1.50 myopia! That's about 26.24 inches, or a little more than 2 feet. | '''What is "close" work?''' | ||
Norms minus diffs = the number of diopters you need to convert to find this answer. For example, if your normalized glasses are -5 and your differential glasses are -3.5, then you need to convert -1.5. You should be able to see 66.67cm with -1.50 myopia! That's about 26.24 inches, or a little more than 2 feet. | |||
== See also == | == See also == | ||