There isn't one single "eye number" that defines normal vision. Normality depends on what aspect of vision is being measured. The references provided highlight several key measurements:
Visual Acuity
- 20/20 Vision: This is considered "normal" visual acuity. As stated in multiple sources (Cleveland Clinic, London Vision Clinic, AAO), this means you can see at 20 feet what a person with normal vision can see at 20 feet. It's possible to have better than 20/20 vision (e.g., 20/16, 20/12.5). The equivalent metric measurement is 6/6.
Eye Pressure (Intraocular Pressure)
- 10-21 mmHg: Normal eye pressure, also known as intraocular pressure, typically ranges from 10 to 21 millimeters of mercury (mmHg). Higher or lower pressures can indicate potential problems (AAO, Glaucoma Research Foundation).
Refractive Error (Sphere in Eyeglass Prescription)
- -0.25 to -2.00: This range in the sphere power of an eyeglass prescription indicates mild nearsightedness (All About Vision). A sphere of 0.00 indicates no refractive error in that meridian. Other values might represent hyperopia (farsightedness) or astigmatism, depending on the cylinder and axis values.
It's crucial to remember that these are just ranges, and individual variations exist. Regular eye exams are essential for accurate assessment and early detection of any potential issues. The "normal" value will vary depending on what aspect of your eyes is being measured.
