Your eye sphere, often referred to simply as "sphere" on your eyeglasses prescription, represents the lens power needed to correct your vision. This measurement is crucial for achieving clear and focused sight. The value is usually given in diopters (D).
Understanding Sphere in Your Eye Prescription
- Definition: The sphere value indicates the amount of lens power required to correct nearsightedness (myopia) or farsightedness (hyperopia).
- Measurement: The sphere measurement is expressed in diopters.
- Significance:
- A minus sign (-) before the sphere number means you are nearsighted. In this case, you have trouble seeing objects at a distance.
- A plus sign (+) before the sphere number indicates you are farsighted. This means you have more trouble seeing up-close objects.
How Sphere Works
Your eye sphere works by correcting how light focuses on your retina.
Nearsightedness (Myopia)
- With nearsightedness, light focuses in front of the retina.
- A minus sphere lens helps to diverge the light rays slightly, causing the focus to move onto the retina, thereby clearing up distance vision.
Farsightedness (Hyperopia)
- With farsightedness, light focuses behind the retina.
- A plus sphere lens helps to converge the light rays, causing the focus to move onto the retina for sharper vision, especially up close.
Example
Consider the following example of an eyeglass prescription:
| Eye | Sphere | Cylinder | Axis |
|---|---|---|---|
| Right | -2.00 | -0.50 | 180 |
| Left | +1.50 | -0.75 | 090 |
In this case:
- The Right eye has a sphere of -2.00, which means that this eye is nearsighted.
- The Left eye has a sphere of +1.50, which means that this eye is farsighted.
Important Notes
- The sphere value is only one component of an eyeglass or contact lens prescription. Other measurements, such as cylinder and axis (for astigmatism) are also important.
- Your sphere value may change over time, so regular eye exams are necessary to keep your prescription up to date.
