It is not advisable to determine the degree of myopia based only on a visual acuity of 0.9, and you need to undergo an optometric examination to determine the exact degree of myopia. The higher the degree of myopia, the more obvious the decrease in naked eye vision, but there is no one-to-one quantitative relationship between the two. In some patients, because of strong eye adjustment, the naked eye vision may not be compatible with the degree of myopia. Therefore, it is not reliable to infer the degree of myopia based on the patient’s visual acuity, and the degree of myopia may be different for patients with the same visual acuity. Moreover, there are many factors affecting naked eye vision, cataract, fundus damage, corneal lesions, myopia, hyperopia, astigmatism, etc. may cause patients’ naked eye vision to decrease. Therefore, the naked eye vision of 0.9 is not necessarily myopia, but may also be caused by other diseases. It is recommended that patients with vision loss should seek prompt medical attention to assess their condition and follow the doctor’s instructions for treatment.