I. Inaccurate optometry results or unconverted prescriptions. Second, the lenses are not properly fitted. Third, the lenses have some optical defects. (1) Optometry results and prescription Optometry methods are divided into subjective and objective. Subjective optometry is suitable for simple refractive error, while objective optometry is suitable for all refractive error cases. Objective optometry requires the use of a ciliary muscle paralyzing agent before optometry, which allows the tired muscles of the eye to rest, the regulating effect of the ciliary muscle to disappear, the pupil to dilate, and the recessive refractive abnormalities to become dominant, laying the foundation for us to arrive at a true result. Especially for those uncooperative patients, we can directly grasp their refractive situation. The reason for inaccurate optometry results is, on the one hand, the wrong method; on the other hand, no ciliary muscle paralyzing agent is used, the subjective optometry is objective, the dilated optometry is small pupil optometry, such as the objective optometry result is -4.5DS-1.00DC×180=5.0, the subjective optometry result may be -5.0DS=5.0, and the patient’s discomfort is inevitable with this prescription. The prescription is not exactly the same as the optometric result, it must be based on the latter appropriate “processing” and made, otherwise the patient may not tolerate. For example, refractive aberration will be controlled within 3.0D difference, so as not to cause unequal image in both eyes; the astigmatic axis of both eyes should be converted to parallel or symmetrical as far as possible, so as not to cause image aberration; column lens should be lowered when the prescription is high, and the spherical lens should be increased at the same time; high hyperopia should be lowered for the first time, etc. (2) The installation of lenses The inclination of the lenses. There are more chances for the eye to look down, especially for tall patients and reading eyes, so the lens must have a certain tilt, generally 10-150, in order to maintain verticality with the visual axis. The distance between the lens and the cornea. It plays an important role in determining the effective degree of the lens and the size of the retinal image. Theoretically, it is 15.7 mm, but generally 13-14 mm is sufficient, in order not to touch the eyelashes. Because the lens is either near or far from the cornea, it will lead to magnification or reduction of the retinal imaging, and when the difference between the refractive power of the two eyes is large, the image of the two eyes is not equal and cannot be integrated, causing discomfort. (3) Optical defects of the lens itself Some of these problems are unavoidable, such as the aberration of the image caused by the column lens or the refractive inequality of the two eyes, the reduction of the field of vision of the cataract lens, etc., which cannot be completely eliminated after excluding other factors, so the patient has to adapt slowly. Some of them can be reduced or even eliminated, such as the problem of oblique astigmatism, spherical aberration, image magnification, etc., which requires the installation and selection of lenses. It is well known that in order to make the eye see clearly in all aspects of the visual field, we should choose perimetric lenses (base arc 1.25D); in order to maximize the elimination of oblique astigmatism, choose crescent lenses (base arc 6.0D); when installing lenses, the concave surface is required to be always close to the eye in order to eliminate spherical aberration; in order to prevent the image from being unequal, you can also choose isoimagination lens lenses. In practice, I have the experience that many patients immediately disappear after switching to another model of lenses, although the indicators of the two pairs of lenses are exactly the same, so it is also important to choose the right lens model and reduce the optical defects of the lenses themselves to eliminate discomfort after prescription.