Writing:Very High Myopia
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This writing is by User:Dlskidmore - they should be the main editor to this page.
Thoughts from someone starting EM at -17D...
Different ranges of myopia may have different experiences with the EndMyopia method There are a few break points where the End Myopia methods get a little more complicated. The higher your myopia, the trickier measurements get. The exact ranges of concern vary depending on the sources you check with, but here’s some ballpark ranges:
|0 to -1.5D||Last Diopter, you don’t even need differentials. Your progress will be slower.|
|-1.5D to -4D||Low Myopia, vertex distance issues negligible.|
|-4D to -6D||Low myopia, but you need to start accounting for vertex distance. (Different sources use different numbers for the break point between Low and High myopia, -5D or -6D.)|
|-6D to -10D||High myopia but you can still use all the tools of EndMyopia|
|-10D to -20D||Very high myopia, cm measurement and subjective refraction become less reliable, but lenses are still commercially available (in decreasing number of options)|
|-20D and up||Very high myopia, lenses are harder to obtain.|
(see cm measurement)
At -10D, an additional quarter diopter is a matter of 2 mm. At -15, an additional quarter diopter is only 1mm. It is very hard to measure the distance to blur precisely enough to measure small changes in your vision.
(see vertex distance) Some people think they're going to solve the cm measurement issue with a test lens kit, but vertex distance issues are just as bad. At -10D, moving the test frame 2mm, can have a 0.25D effect on apparent lens strength. At -15D, moving the test frame 1mm has more than 0.25D effect on apparent lens strength. Even if you have your eyes professionally measured, if the frames you order have a different vertex distance than the apparatus you were measured in, a correction to the value may need to be made.
The stronger the lens, the more important vertical placement of the optical center is, and most places that make glasses without a prescription do not do custom pupil height lenses. (This would be difficult to do if offered, as this measurement is particular to specific frames and the shape of your face, so you’d have to order fitter frames with plano lenses, mark optical height and return them. Your optometrist does this, sending the marked plano lenses to the lab for reference when grinding your lenses.)
A strong lens, held at a slight angle to the intended angle, introduces an unintentional cylinder power. This cylinder can cause headaches, disorientation, difficulty adjusting to new glasses, and potential adaptation to the cylinder causing changes in your next subjective refraction. If your axis is changing frequently, this may be caused by an unintentional cylinder power in your glasses.
Time to 20/20
Even at the best possible rate of improvement, 0.75D per year, it may take a very high myope a very long time to get to 20/20 even if they can stick with the program that long and have steady progress.
Eyeballs are not round
As eye length increases, it tends to decrease in regularity of shape. Measurements of your eye length gets less reliable the longer your eye is. It's unknown what all the effects of this are, but possible it's contributing to astigmatism or the risk factors that come along with high myopia. It may also be why auto-refractors tend to be inaccurate.
Even if you can’t really expect to get to 20/20 any time soon, and there are some hurdles in your way, the practices recommended by EndMyopia can still be beneficial.
It’s quite probable you got to be so myopic, at least partially, through eye strain. You may not notice it because you’re used to it, but all that near work you do is affecting your eyes. If you have progression, tiredness, dry eye, or vertigo, you might benefit from taking more breaks from your computer/books/craft and wearing weaker computer glasses. (See Differentials and 20-20-20 rule)
Risks of other eye diseases
High myopia is associated with several more concerning eye diseases. Of the limited ranges studied, the more myopic you are, the higher your risk. The mechanism of this relationship is not known, but myopic defocus (the primary mechanism of EndMyopia) could help in multiple ways.
- The ciliary muscle affects drainage of aqueous fluid, which could affect glaucoma risk.
- The ciliary body, attached to the ciliary muscle, affects production of aqueous fluid, which could affect glaucoma risk.
- The choroidal tissue layer thickens with myopic defocus , which could affect risk of various retinal issues.
With optometrist glasses often running hundreds of dollars, and minor changes in frames causing disorienting distortion effects, being forced to get new prescriptions can be traumatic for those that are very high myopes, especially if they are breaking some barrier with additional challenges, like no longer being able to use your favorite brand of contacts because they don’t come in your new power. Just stabilizing your situation may have benefits in lowering your stress, keeping your current options open, and not elevating your risks for more severe eye issues any further.
As a very high myope, you’re more dependent on your lenses and your lens suppliers than lower myopes. This can have follow-on mental effects that are detrimental. Learning about your vision, learning how to get and adjust your lenses to suit you, having spare pairs of glasses that would have been unaffordable from the optometrist, gives you an additional level of control over your life and your environment. Even if you can order your own glasses, do continue to go get annual screenings to catch early signs of additional vision issues beyond the myopia itself.
How to do EM with very high myopia
Your best starting place is your professional refraction. The vertex distance issue is still an issue for them, but you should get a more consistent result from the professionals. Before ordering your first differentials remember to account for vertex distance. Change the vertex distance from 13 to 0 mm, then do your power reduction, then take that value and convert back to the 13mm vertex distance.
Because pupil height is a bigger issue for stronger lenses, you may need to adjust your glasses to get a better fit. Find the optical center of your lens. You may be able to adjust the optical center through adjusting built in nose pads or adding adhesive nose pads, or changing where they sit on your face. If you can’t correct this, you should try ordering the same lenses in a different frame. Once you find frames you can adjust correctly, stick with those frames for future purchases. You’ll not only make it easier to fine tune the optical center, but the unintentional cylinder will be more consistent between pairs and cause fewer issues with switching.
Once you get your first differentials, you’re pretty much on the same track as someone with moderate myopia. Forget about the numbers except when you’re ordering lenses, your subjective experience of distance to blur in your glasses is your key to knowing when to decrease. Notice when you are leaning into the screen/book and when you have enough clarity to back up. When you’re leaning in, notice if you’re leaning in because the text is too small or because it’s blurry. If the text is too small, use a larger font size and back up to the edge of blur. If you can see large text from further away than you want to sit, then you’re ready for a reduction already.
If you're a real stickler for measurement, the only way to eliminate vertex distance issues is to place a lens on your eye. You'll need a contact lens that is the same base curve and material as the ones you were professionally fitted with, but a power at least 1D low. You can then take your cm measurement in the contacts, then add that result to your contact lens power to get your total lens power needed to see clearly to infinity.
- Cooper, Gareth. "Back Vertex Distance Compensator". bvdcalculator.garethcooper.com. Retrieved 2021-07-25.
- "Lecture: Myopia: Dispelling Myths and Misconceptions". Retrieved 2021-07-25.
- Read, Scott A.; Fuss, James A.; Vincent, Stephen J.; Collins, Michael J.; Alonso-Caneiro, David (2019). "Choroidal changes in human myopia: insights from optical coherence tomography imaging". Clinical and Experimental Optometry. pp. 270–285. doi:10.1111/cxo.12862. Retrieved 2021-07-25.