A refractive error of 800 degrees can cause vision loss, but due to individual differences, it is not possible to accurately predict a patient’s vision based on the number of degrees. Refractive errors include myopia, hyperopia, and astigmatism, and their severity is indicated by the number of diopters, with the higher the number of diopters, the more severe the refractive error. In general, the higher the refractive error, the more significant the vision loss, but due to individual differences, different patients have different tolerance levels for the same refractive error, and the magnitude of vision loss is also different. Because there is no one-to-one quantitative relationship between the degree of refractive error and visual acuity, it is not possible to speculate on a patient’s visual acuity based on the degree of the patient’s refractive error. If a patient with refractive error wants to know the exact visual acuity, it is recommended that the patient should go to the ophthalmology department of the hospital for a visual acuity test to determine this.