Decoding your eyeglass prescription is essential for choosing colored contact lenses that enhance your appearance while correcting your vision. This comprehensive guide explains key terms like OD, OS, Sphere (SPH), Cylinder (CYL), and Axis to help you make an informed decision.
Understanding OD and OS in Eye Prescriptions
When reviewing your contact lens prescription, you'll notice the abbreviations OD and OS instead of "right eye" and "left eye." These optometry terms originate from Latin:
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OD (Oculus Dexter): Indicates your right eye prescription
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OS (Oculus Sinister): Indicates your left eye prescription
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OU (Oculus Uterque): Occasionally appears, meaning "both eyes"
The 3 Key Components of Your Contact Lens Prescription
Your eye prescription details contain three crucial elements that determine your vision correction needs:
1. Sphere (SPH) - Correcting Nearsightedness & Farsightedness
The SPH value shows the lens power required to fix:
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Negative numbers (e.g., -2.50): Correct myopia (nearsightedness) - difficulty seeing distant objects
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Positive numbers (e.g., +1.75): Correct hyperopia (farsightedness) - difficulty seeing nearby objects
This correction applies uniformly across the entire lens.
2. Cylinder (CYL) - Astigmatism Correction
The CYL value addresses astigmatism, caused by an irregularly shaped cornea or lens. Unlike SPH, it provides customized correction in specific lens areas.
3. Axis - Positioning Your Astigmatism Correction
The Axis number (0°-180°) determines the orientation of your astigmatism correction, ensuring proper lens alignment with your eye's unique shape.
