Visual acuity of 4.9 is the visual acuity expressed by the five-point visual acuity recording method, which is equivalent to a visual acuity of 0.8 if converted to the familiar decimal visual acuity recording method. Currently, there are two main methods of visual acuity, the first is the five-point visual acuity recording method, which means that a normal adult should be able to achieve a visual acuity of 5.0 and above, and the second is the counting visual acuity recording method, which means that a normal adult should be able to achieve a visual acuity of 1.0 and above. The two are directly convertible, with a visual acuity of 4.9 being equivalent to a visual acuity of 0.8. The patient’s vision examination reveals that his current visual acuity is slightly lower than normal, which may be caused by refractive errors such as myopia, astigmatism, or diseases such as cataract or glaucoma. Patients with vision loss are advised to seek prompt medical attention to evaluate their condition and follow medical advice.