With the popularization of electronic products, more and  more people suffer from myopia, we can see eyewear shops everywhere when we walk on the street. Now there are many myopia frames with different materials. For example:metal optical, titanium optical, and the expensive buffalo horn optical and wood optical, etc., There are a lot of choices for us. It is easy to choose the shape of eyewear. Just take a look, try it, the style and color should macth your face shape, but for myopia glasses, you should pay more attention to it. Summarize the following factors that determine the quality of optical glasses, I hope it will be helpful to you.

1.Myopia degree of the lens. How to match the myopia degree of the lens more appropriately is the most important point in the lens matching process.Our optometry principle is the clearest state of the lowest degree. The most common way is to judge whether the focus is on the retina according to the different wavelengths of red and green.Show the red and green test marks. If you look at them with a single eye, the figures in green or red are clear.  The figure in red is clearer, indicating that the focus is still before the retina(under correction), the figure in green is clear, indicating that the focus is behind the retina (over corrected). The figures in red and green are clear that indicates the focus is on the retina (Best correction). At the same time, check the vision function together and optimize the prescription according to the actual situation.

2.Astigmatism degree and axis. This is particularly important for patients with astigmatism.The principle of astigmatism correction is to achieve the best correction.The astigmatism can be simply understood as:on the basis of myopia, there is an additional degree in a certain direction. For example, -1.00-0.50*180, the direction of the 90 axis is -1.50, and the other directions are -1.00. This is why the astigmatism should achieve the best correction, and we also understand the importance of the accuracy of the astigmatic axis.However, some patients with astigmatism need to have a adaptation period for the first time wearing glasses. In the long run, astigmatism still needs to be corrected. If the astigmatism is uncorrected, which means that everything is double,which is one of the causes of visual fatigue.In order to ensure more accuracy, the cross cylinder should be used to fine adjust the astigmatic axis and degree under the condition of best correction or slightly over correction.

3. The pupil distance refers to the horizontal distance between the pupil center of the two eyes.Many people have different pupil distances. For example, the total pupil distance is 66, the right pupil distance is 32, and the left pupil distance is 34. Only in this way to accurately measure the monocular pupil distance and make them separately,can we make glasses more suitable for customers. Especially for patients with high myopia,The requirements of pupil distance accuracy are very strict. Otherwise, the prism effect will be produced. Myopia lenses can be understood as a combination of many prism. Viewed from the center point, the patient can see things without shifting. Some stores have expensive imported processing machines with higher processing accuracy, and more comfortable glasses are produced.

4、pupil height. Pupil height refers to the vertical distance from the passing point to the bottom edge of the lens when the eyewear is worn on the face and the eyes are looking at the distance. Only when the eyewear is put on the face and observed by professionals can we try to avoid discomfort caused by pupil height. Too large frames can cause high pupil height. If you use a pair of frame, you can see clearly in the distance, but not in the near, or vice versa.It shows that this frame is not suitable for optical frame. In this case, you need to select the frame under the guidance of a professionals, and eliminate the inappropriate frames in advance. It can’t be arbitrarily selected according to your own preferences. Getting a right eyewear is a technical job, and you need to listen carefully to some opinions to get more appropriate glasses.

5. Front Curvature. The facial contour of Asians is relatively flat, so the frame curvature is relatively flat, or slightly inward. 0-8 degrees is a normal range. Proper bending will improve comfort.And if the frame turns outward, it will definitely be uncomfortable to wear,because the eyes can easily see the edge of the lens, and the imaging effect of the edge lens is poor. If the frame is too curved,it will also change the actual degree of lenses, causing discomfort.

6. Front inclination. The front inclination refers to the angle between the lens plane and the vertical line after wearing the frame.Generally, 3-10 degrees is a normal range. Some European and American glasses are worn by Asians. The front inclination is too large, many people wear discomfort and  it will change the actual degree. I have some statistics about the change of lenses degree caused by the size of the front inclination and the front curvature.When you look at the form, you know that it has a great impact. This is why many people need to lower the degree to match large curved sunglasses for comfort.How to choose a suitable front inclination? It mainly depends on the height of the bridge of your nose.If the bridge of the nose is high, you can choose the one with a higher inclination, while if the bridge of the nose is low, you can choose the one with a smaller inclination.

7. Vertex Distance.The vertex distance refers to the distance of the inner surface of the lens in the corneal vertex. The average Asian parameter is 12 mm. In optometry, the default parameter is 12mm.

If the vertex distance becomes smaller, the actual degree of myopia lenses will become larger, the vertex distance becomes larger, and the actual degree of myopia lenses will become smaller. This is one of the important reasons why many people feel clear when they try it on, and how they feel blurry after matching.On the premise that the eyelashes do not reach the lens, the smaller the vertex distance, the better. In this way, we can see more through the optical center point, and it is not easy to scan the edge of the lens to see the part with poor imaging, so as to achieve a good visual effect. Of course, too small vertex distance will make it difficult for the wearer of progressive multifocal lens to see the near area, which requires the comprehensive consideration of professionals.

8.Selection of frame size: Many people buy the frame just to see whether they like it or not, whether it looks good to wear, the quality is OK, and the price is reasonable. Many people buy their own frames and ask me to assemble lenses for them. Although The frame looks good, it is not suitable for myopia frame. There are two important size references for the frame: A and B. The closer the length of A is to the pupillary distance, the thinner the lenses is, the better the visual effect and the more beautiful it is. The longer the A is, the opposite is true.The length of B should also be moderate.

9.Lens thickness: The thickness can be ignored within 300 degrees. The appropriate frame size needs to be selected from 500 degrees. Higher refractive index makes the lens thin and light.Above 700 degrees, try to choose the highest refractive index within the budget. Heavy and thick glasses press on the bridge of the nose all day,the experience is really bad. The glasses often slide down, and the eyes can't see through the optical center of the lens.The degree of myopia in the eyes has quietly increased.

10. Refractive index.

Generally speaking, 1.5, 1.56 and 1.6 can be selected in -2.00.

1.6 and 1.67 can be considered within -5.00

1.67, 1.701 and 1.74 can be selected in -6.00

1.701 and 1.74 can be considered above -8.00

1.74 and 1.76 are considered above -12.00

The common pupil distance for boys is 60-68,

The common pupil distance for girls is 58-64,

The pupil distance is small, and the higher refractive index is selected.

The pupil distance is too large, and the lower refractive index is selected.

The frame is small, and the lower refractive index is selected,

The frame is larger, and the higher refractive index is selected.

The above datas are for reference only.

10.Optical center movement. It can be used to judge whether a pair of frames is suitable for you and whether the refractive index of the lens needs to be improved. The calculation method is: (the pupil distance of the eyewear frame - the pupil distance of the customer)/2.

12. Weight of glasses:

The higher the degree, the heavier the weight,

The smaller the pupillary distance, the heavier the weight,

The bigger the frame, the heavier the weight,

The lower the refractive index, the heavier the weight,

The bigger the optical center movement, the heavier the weight,

The thicker the frame, the heavier the weight.

If the degree exceeds - 5.00, the weight of glasses should be fully considered, and the above factors should be paid attention to.

13.The stability of the eyewear frame. The fitting process is extremely important. You need a professional to check which frame you choose to make sure it is more suitable. Even if consumers have done their homework, they still know a little about it. It is true that adjusting the eyewear frame can better match the face shape, provided that the frame is basically suitable. Too big or too small frame can't be adjusted later. Only stable wearing can let the eyes see through the optical center, prevent visual fatigue, and ensure the stability of the myopic degree.

14. Lens selection. According to the classification of ophthalmology, optometry and optical drugs, lenses are optical drugs. Since it's medicine, you can't buy it casually. It needs to be recommended by professionals who understand lens knowledge to ensure that it is suitable for you. The curative effect of the medicine is also different. The lenses suitable for you have high, middle and low grades. You can choose the best one according to your economic ability.

Don't follow the trend. We should choose the right lens according to our actual situation.

For example, 1.74 is selected for -2.00, but obviously 1.5 and 1.6 are cheap and suitable.

15.Nose pad. The acetate frame of the integrated nose pad is easy to slide when worn by people with collapsed nose bridge,that is, the details are not considered. People with a collapsed nose should choose a metal frame with an independent nose pad to better support the frame.The nose pad should fit the nose as much as possible. The larger the force area, the less the pressure, the higher the comfort, and the more stable the wearing. Progressive multifocal glasses need to choose S-shaped nose pad. If there is a slight deviation, you can also adjust the vertex distance and pupil height to improve the problems that may occur when you look far and near. It is strongly not recommended to use an integrated nose pad,which can't be adjusted at all.

16.Tips hook ears. The temple should have a force to pinch the head. More importantly, the bend of the tips can hook the ear to prevent the glasses from slipping down easily.After putting on the glasses, pull it forward, if it is pulled out 1-2 cm, it is ok. If it is pulled away, it means that you need to adjust the tips.Only front curvature,the nose pad, temple and tip are normal, can we wear the eyewear comfortably and stably.It is better to protect the vision stability and not easy to fatigue.During the use, in case of pressing it, or long-term single handed removal and wear, causing the deformation of the frame, the business should have the technology and service awareness to help customers adjust.

17.Glasses processing. In order to make a proper pair of glasses, all links need to be linked, and no problem can occur in any link. And the processing link is the same as optometry, which is an important link. Therefore, it is important to choose a regular eyewear shop, which has professional processing masters.

In fact, there is still a lot of knowledge about glasses.And after many years in the field,I have only known some basic knowledge.It is indeed necessary for consumers to do their own homework, but it is unrealistic to have a deep understanding through doing their own homework. Besides mastering some professional knowledge, the most important thing is to find a formal professional glasses shop and let professionals help you solve these problems. They will not only suggest what type of glasses you are suitable for, such as acetate optical, metal glasses or titanium glasses, full frame glasses, half frame glasses or rimless glasses, but also, most importantly, give you a lot of professional advice on glasses. It is very important to protect your eyesight.