How to perform optometry and choose lens frame for high astigmatism?
The definition of high astigmatism in textbooks is that when it reaches 75 degrees, it means high astigmatism, but in practice, when it reaches 150 degrees, it means high astigmatism. The current range of most brand lenses is up to 200 degrees. If the astigmatism is 225 degrees, most brands generally need to be customized.
1) How to optometry:
Two words are "foot correction"!
What is astigmatism? In other words, if you have myopia of 200 degrees and astigmatism of - 2.00, then in a specific direction, it is 400 degrees. The principle should be given enough degrees. The astigmatism symptom is to see where all ghosts, astigmatism is not corrected is one of the causes of visual fatigue. Of course, it will be difficult to adapt if the astigmatism degree is increased too much. You can increase the astigmatism degree step by step to finally correct the astigmatism. Don't be afraid of not coming down with enough astigmatism. The more uncorrected you are, the more tired your eyes become and the more unstable your degree is
2) Frame selection:
The choice of lens frame depends on your myopia degree, pupil distance and frame size. With high myopia, you need to choose a smaller frame to make the outside less thick.
If the degree of myopia is not high, you need to know what your astigmatic axis is. The range is 1-180 astigmatic axis.
I will focus on the selection of 180 and 90 astigmatic axis frames.
First of all, we need to know that the astigmatic axis is 180, so the thickness is 90 (vertical direction). So the frame height of the frame we choose must not be high. If we choose the frame height, the thickness of the vertical direction will be worn away, and the lenses will naturally be thinner. (If the frame is high, it will be round, and if it is high, it will be square)
On the contrary, if the axis position is 90, the thickness is 180 (horizontal direction). Usually, our thickness is on the outside, and the thickness of astigmatism is added on the outside, which is exaggerated. Therefore, the smaller the lens frame, the thinner it will be. That is, the closer the sum of lens width and center beam width is to your pupil distance, the thinner it will be. It is more necessary to choose a higher refractive index to make the thickness less obvious.
1) How to optometry:
Two words are "foot correction"!
What is astigmatism? In other words, if you have myopia of 200 degrees and astigmatism of - 2.00, then in a specific direction, it is 400 degrees. The principle should be given enough degrees. The astigmatism symptom is to see where all ghosts, astigmatism is not corrected is one of the causes of visual fatigue. Of course, it will be difficult to adapt if the astigmatism degree is increased too much. You can increase the astigmatism degree step by step to finally correct the astigmatism. Don't be afraid of not coming down with enough astigmatism. The more uncorrected you are, the more tired your eyes become and the more unstable your degree is
2) Frame selection:
The choice of lens frame depends on your myopia degree, pupil distance and frame size. With high myopia, you need to choose a smaller frame to make the outside less thick.
If the degree of myopia is not high, you need to know what your astigmatic axis is. The range is 1-180 astigmatic axis.
I will focus on the selection of 180 and 90 astigmatic axis frames.
First of all, we need to know that the astigmatic axis is 180, so the thickness is 90 (vertical direction). So the frame height of the frame we choose must not be high. If we choose the frame height, the thickness of the vertical direction will be worn away, and the lenses will naturally be thinner. (If the frame is high, it will be round, and if it is high, it will be square)
On the contrary, if the axis position is 90, the thickness is 180 (horizontal direction). Usually, our thickness is on the outside, and the thickness of astigmatism is added on the outside, which is exaggerated. Therefore, the smaller the lens frame, the thinner it will be. That is, the closer the sum of lens width and center beam width is to your pupil distance, the thinner it will be. It is more necessary to choose a higher refractive index to make the thickness less obvious.