Difference between revisions of Severe myopia

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==Retinal detachment==

As your eyeballs elongate with increasing myopia, the retina, which is the light-sensing membrane at the back of the eye becomes more tensioned and is at higher risk of detaching from the eyeball. For severe myopes, the risk of retinal detachment is markedly elevated[https://en.wikipedia.org/wiki/Retinal_detachment]. All the more reason to reverse direction.

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==Heavy glasses==

The front of minus lenses is flatter than the back, which is curved more strongly. In the center, minus lenses are typically only about 1.5mm thick (thinner would make the lenses too fragile), but moving away from the center (optical axis) the glass becomes thicker. The more minus the diopters, the larger the difference in curvature, and the thicker the edge of the lenses.

The front of minus lenses ~~are~~ flatter than the back, which is curved more strongly. In the center, minus lenses are typically only about 1.5mm thick (thinner would make the lenses too fragile), but moving away from the center (optical axis) the glass becomes thicker. The more minus the diopters, the larger the difference in curvature, and the thicker the edge of the lenses.

When choosing a normal frame with regular diameter lenses, you will end up with very thick lens edges and hence uncomfortable heavy glasses that easily slide off your nose and look ugly. What to do?

===Choose frames with small-diameter lenses===

The smaller the diameter of the lenses once they are cut to fit the frame, the thinner the edges and lower the weight. Such frames are not considered very fashionable, and hence can be hard to find. But with severe myopia, the aesthetic and weight inconvenience of very thick edges make frames with small-diameter lenses very desirable.

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===Pick frames with a well-matching pupillary distance===

Lenses are cut to fit the frame such that their optical axis (the thinnest part of a minus lens) sits right in front of the pupil of each of your eyes. If the frame matches your pupillary distance, this will have the optical axis right in the middle of the rims of the frame, which minimizes the thickness of the edges.

==View compression==

Strong minus glasses significantly compress objects in your field of view such that they appear smaller. The closer the lenses are to your eyeballs, the less compression happens. Try it: move your glasses away and toward your eyeballs, and the effect will be readily apparent, at least if you are a severe myope.

When the lenses sit on your eyeballs, view compression is absent. This is the case when you wear contact lenses. But for glasses you can get some of this benefit by choosing frames with really small diameter lenses and having the nose pads and ear hooks adjusted to pull the frames closer to your eyeballs there where larger diameter frames would have the lenses touch your face when pulled in that close.

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 ==Retinal detachment==
 As your eyeballs elongate with increasing myopia, the retina, which is the light-sensing membrane at the back of the eye becomes more tensioned and is at higher risk of detaching from the eyeball. For severe myopes, the risk of retinal detachment is markedly elevated[https://en.wikipedia.org/wiki/Retinal_detachment]. All the more reason to reverse direction.
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 ==Heavy glasses==
+The front of minus lenses is flatter than the back, which is curved more strongly. In the center, minus lenses are typically only about 1.5mm thick (thinner would make the lenses too fragile), but moving away from the center (optical axis) the glass becomes thicker. The more minus the diopters, the larger the difference in curvature, and the thicker the edge of the lenses.
-The front of minus lenses are flatter than the back, which is curved more strongly. In the center, minus lenses are typically only about 1.5mm thick (thinner would make the lenses too fragile), but moving away from the center (optical axis) the glass becomes thicker. The more minus the diopters, the larger the difference in curvature, and the thicker the edge of the lenses.
 When choosing a normal frame with regular diameter lenses, you will end up with very thick lens edges and hence uncomfortable heavy glasses that easily slide off your nose and look ugly. What to do?
 ===Choose frames with small-diameter lenses===
 The smaller the diameter of the lenses once they are cut to fit the frame, the thinner the edges and lower the weight. Such frames are not considered very fashionable, and hence can be hard to find. But with severe myopia, the aesthetic and weight inconvenience of very thick edges make frames with small-diameter lenses very desirable.
@@ Line 31: / Line 28: @@
 ===Pick frames with a well-matching pupillary distance===
 Lenses are cut to fit the frame such that their optical axis (the thinnest part of a minus lens) sits right in front of the pupil of each of your eyes. If the frame matches your pupillary distance, this will have the optical axis right in the middle of the rims of the frame, which minimizes the thickness of the edges.
+==View compression==
+Strong minus glasses significantly compress objects in your field of view such that they appear smaller. The closer the lenses are to your eyeballs, the less compression happens. Try it: move your glasses away and toward your eyeballs, and the effect will be readily apparent, at least if you are a severe myope.
+When the lenses sit on your eyeballs, view compression is absent. This is the case when you wear contact lenses. But for glasses you can get some of this benefit by choosing frames with really small diameter lenses and having the nose pads and ear hooks adjusted to pull the frames closer to your eyeballs there where larger diameter frames would have the lenses touch your face when pulled in that close.