What does it mean to have a bare-eye vision of 4.8?
Naked eye vision refers to the maximum size of an image that a person can discern without wearing any glasses or contact lenses. Normal adult naked eye vision should reach 5.0 or above. In the five-point recording method, 4.8 corresponds to a visual acuity of 0.6 on the standard visual acuity chart, which is considered mild vision loss. Naked eye vision is determined by the refractive power, transparency, and axial length of the eye's lens. It can reflect the health status of the eyes to a certain extent, and most vision tests during physical examinations measure naked eye vision. It is important to note that the degree of refractive error and visual acuity are two separate concepts and do not have an absolute conversion relationship. Two individuals with the same refractive error may have different visual acuities, and vice versa. Each person's ability to adjust their vision varies, and there is no fixed proportional relationship between the visual acuity obtained from a vision test and the refractive error prescribed by an optometrist.
Naked eye vision of 4.8 is considered mild vision loss, but the specific refractive error (in diopters) cannot be determined without a medical refraction test. Visual acuity represents the central visual function of the macula, while refractive error indicates the refractive state of the eye. These are two completely different concepts. A visual acuity of 4.8 could be due to myopia, hyperopia, astigmatism, or pseudomyopia. If pseudomyopia is diagnosed, relieving muscle spasm of the ciliary body and allowing the eyes to rest fully can restore visual acuity to above 5.0. For low-grade myopia in adolescents, wearing glasses combined with low-concentration atropine eye drops may be recommended. Children over 8 years old may also try corneal reshaping lenses. For patients with astigmatism or hyperopia, correction with spectacles is recommended.
Eye vision refers to the ability to recognize objects at a certain distance under a 1-minute angle condition. Vision tests, whether they are scored on a visual acuity chart, decimal visual acuity chart, or logarithmic visual acuity chart, are all based on this fundamental principle. Generally, a visual acuity of 1.0 (on a decimal visual acuity chart, equivalent to 5.0 on a logarithmic visual acuity chart) under a 1-minute angle is considered the standard for normal vision. Everyone has a different minimum visual threshold, which depends on the relative density of cone cells in the macula of the eye. When the density is higher, the visual threshold is higher, and the minimum angle is smaller, resulting in higher visual acuities such as 3.0 (on a decimal visual acuity chart) or even higher. It is important to distinguish between visual acuity and corrected visual acuity. Visual acuity refers to the vision measured without wearing glasses or contact lenses, while corrected visual acuity refers to the vision measured after wearing glasses with the appropriate refractive correction.
