After aneye exam your doctor will hand you a prescription. But have you ever tried to read it?
Ophthalmologists and optometrists sometimes use different measurements for astigmatism. Their prescriptions may appear different depending on what type of provider you see. The optical shops who make the glasses or contacts have no problem understanding the prescription no matter who is providing it.
+1.0 Astigmatism, +2 Astigmatism Prescription: What Do These Numbers Mean?
Astigmatism is measured in diopters. A perfect eye with no astigmatism has 0 diopters. Most people have between 0.5 to 0.75 diopters of astigmatism. People with a measurement of 1.5 or more typically need contacts or eyeglasses tohave clear vision.
Of the three numbers on your contacts or glasses prescription, the last two refer to astigmatism:
- Sphericalindicates whether you are nearsighted or farsighted. A plus sign indicates you are farsighted, a minus sign indicates you are nearsighted. The higher the number, the stronger your prescription.
- Cylindermeasures what degree of astigmatism you have, or how flat or irregular the shape of your cornea is.The more your eye looks like an American football (instead of a basketball), the more astigmatism you have.
- Axisis measured in degrees, and refers to where on the cornea the astigmatism is located. Axis numbers go from 0 to 180. If you think of the eye as a map hanging onawall, the 90 degree axis or line, runs up and down (or north to south) on the eye. The 180 degree line runs across the eye, east to west.
As an optical expert deeply immersed in the world of vision care, my extensive knowledge and experience allow me to dissect and explain the intricacies of the astigmatism measurements discussed in the article "¿Qué significan las mediciones del astigmatismo?" by Celia Vimont and David Turbert. This article, reviewed by J Kevin McKinney, MD, sheds light on the nuances of astigmatism prescriptions and the variations that may arise depending on whether an ophthalmologist or optometrist conducts the eye examination.
To unravel the mysteries of astigmatism prescriptions, one must first grasp the fundamental concept that astigmatism is measured in diopters. In a perfect eye devoid of astigmatism, the measurement is 0 diopters. However, most individuals have a slight degree of astigmatism ranging from 0.5 to 0.75 diopters. Those with a measurement of 1.5 or more often require corrective measures such as contact lenses or eyeglasses to achieve clear vision.
The article delves into the numeric codes embedded in an astigmatism prescription, exemplified by expressions like "+1.0 Astigmatism" or "+2 Astigmatism Prescription." These numbers hold the key to understanding the severity of astigmatism. The three numbers on a prescription reveal crucial information, with the last two specifically addressing astigmatism.
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Spherical: This component indicates whether the individual is nearsighted or farsighted. A plus sign signifies farsightedness, while a minus sign indicates nearsightedness. The magnitude of the number correlates with the strength of the prescription, with higher numbers indicating a more significant visual correction.
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Cylinder: The cylinder measurement gauges the degree of astigmatism, elucidating how flat or irregular the cornea's shape is. Astigmatism arises when the cornea resembles an American football rather than a basketball. A higher cylinder number signifies more pronounced astigmatism.
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Axis: This parameter, measured in degrees ranging from 0 to 180, identifies the location of astigmatism on the cornea. To visualize, consider the eye as a map hanging on a wall. The 90-degree axis runs up and down (north to south), while the 180-degree line runs across the eye (east to west). Understanding the axis aids in pinpointing the exact location of astigmatism for precise corrective measures.
In essence, decoding an astigmatism prescription involves comprehending these three components—spherical, cylinder, and axis. The intricate interplay of these elements forms the basis for crafting eyeglasses or contact lenses tailored to address the unique visual needs of each individual. This insight not only demystifies the numerical jargon found in prescriptions but also empowers individuals to make informed decisions about their eye care.
