How To Choose Contact Lenses Power Best For Your Eyes
Selecting the right power for your contact lenses is vital for clear vision and optimal eye health. Whether you’re farsighted, nearsighted, or have astigmatism, you need the correct lens power for effective vision correction.
In this article, we’ll discuss how to determine your contact lens power, factors, and considerations for selecting your contact lens power.
Understanding Contact Lens Prescription
Understanding your contact lens prescription can be challenging, especially when you aren’t familiar with the terms Optometrists use. You need to understand this before you can read your contact prescriptions. It is also vital to know that your contact lens prescriptions contain more information than your glasses prescription. Also, your contact prescriptions can be in a contact lens box or paper.
Introduction to Contact Lens Prescription
Your contact lens prescription contains a mixture of numbers and letters. In the prescription, you’ll see two numbers- one for your right eye and the other for your left eye. The two numbers exist because many people need different kinds of vision correction in each eye.
Let’s look at some of the abbreviations on some contact lens prescriptions.
- OS – Stands for Oculus Sinister, meaning left eye
- OD – Stands for Oculus Dexter, meaning right eye.
- DIA – Diameter refers to the size of your contact lens. It is the measurement across the lens from one edge to another. An accurate diameter covers your cornea without causing irritation or impairing your vision.
- BC – Stands for Brand Curve. Your base curve determines your comfortability. It shows the curvature of your contact lens and how well the lenses fit your cornea. Your base curve is measured in millimeters and between 8 and 9.
- Expiration Date: Expiration dates on contact lenses vary from state to state. Know that most contact prescriptions expire in 1 to 2 years.
Components of a Contact Lens Prescription
It is time to look critically at the various components of your contact lens prescription.
Sphere (SPH)
Your sphere power shows the strength of the lens you need for vision correction. Measurement is in diopters.
In measuring the lens strength you need, your eye doctor performs an eye exam. He/she uses various tools during the exam to identify where the light focuses in your eye.
Usually, most contact lens sphere powers are between -6.00 through +6.00 in quarter diopter steps. However, the maximum sphere power available for contact lens prescriptions is typically +8.00 for farsightedness and -8.00 for nearsightedness.
Cylinder (CYL)
You will always see your Cylinder Power abbreviated as ‘CYL’. It refers to the degree of astigmatism correction you need in a contact lens prescription. Astigmatism happens when your cornea or lens has an irregular curvature or shape, causing blurry vision at all distances. Like Sphere, Cylinder power is measured in diopters and can also have positive or negative values.
The powers range from -0.75 through -2.25 in half-diopter (0.50) steps.
Axis
Axis specifies the orientation of astigmatism in your eye. It ranges in degree from 0 to 180. It is common for any astigmatism correction.
Addition (ADD)
ADD power is common in multifocal contacts prescription. You’ll find this usually in people over 40 who need multifocal lenses. The ADD power contacts prescriptions that are written as low, medium, or high. It stems from the wearer’s needs and activities.
Determining Your Contact Lens Power
If you want the best vision and address any vision problems, determining the correct power for your contact lenses is essential. The process starts with a comprehensive eye test conducted by an eye care professional.
Consultation with an Optometrist
You will need guidance from an Optometrist to obtain the correct prescription for your lenses. If you have a written prescription from a previous eye test, your Optometrist will review it.
During the consultation, a series of tests will take place to evaluate your eye health. The results of these tests and your requirements will determine the most suitable lens power for your vision correction.
Don’t forget you need regular check-ups to monitor your eye health and ensure your lenses give you the best.
Interpretation of Prescription Numbers
A standard prescription contains a positive or a minus sign. The prescription figure has its function. We’ll look at the interpretation for each component.
Sphere Power
A negative number stands for a near vision, and a positive number indicates farsightedness.
Cylinder Power
Your cylinder power can be positive or negative and measures the degree of astigmatism present.
Axis Angle
Your axis angle ranges in degrees from 0 to 180. It shows the direction where the astigmatism is oriented in the eye.
Addition Power:
The additional power is usually a positive number and mainly for multifocal contacts.
Factors Influencing Contact Lens Power Selection
Refractive Error (Myopia, Hyperopia, Astigmatism, Presbyopia)
When eye doctors prescribe contact lenses, they do so to correct refractive errors. Your contact lens power must provide the necessary visual correction needed. For example, myopia needs negative power lenses, while hyperopia needs positive power lenses.
Eye Health Conditions
Some health conditions can be a factor in your contact lens power selection. For instance, irregular corneas may require special lenses with customized power.
Lifestyle and Activities
Your lifestyle and activities are determinants of your contact lens power. You may prefer specialized contact lenses for enhanced stability for outdoor sports and other active lifestyles.
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Types of Contact Lenses Based on Power
Soft lenses appear in various designs, and they include:
Spherical Lenses
These contacts are for myopic or hyperopia patients with little need for astigmatism correction. You can find this lens in daily, weekly, bi-weekly, and monthly lenses.
There are differences between an eyeglass prescription and a contact lens prescription. There are a few reasons for these differences. The first one plays out when the eye care professional is determining the power of a spherical lens, the professional considers spherical equivalent and vertex conversion.
Your spherical equivalent is the closest estimate of your prescription without astigmatism correction included. To calculate, divide the cylinder power of your eyeglass prescription in half. To your result, add spherical power.
Your vertex conversion makes up for the change in prescription when you go from eyeglasses to contact lenses.
Toric Lenses for Astigmatism
Toric lenses correct astigmatism. In a toric lens, your contacts sit in a specified orientation to give you a proper correction, unlike spherical contacts. Contact lens brands refer to various methods for stabilizing toric lenses. Some of them include thin zone, prism ballast, and Peri-ballast
Multifocal or Bifocal Lenses for Presbyopia
If you’re presbyopic or need near and far-distance vision correction, multifocal contacts are for you. In multifocal, you view multiple images at the same time. That’s why it is called simultaneous images. There are also toric vocals that combine toric and multifocal into one lens.
Customized Options
You can customize a soft lens. These contact lenses provide more than one function. An example is mono vision which involves one lens to correct near vision and another to correct distance vision. Another example is cosmetic colour lenses.
Considerations for Contact Lens Power Selection
Before your contact lens fitting and selection, you need to consider several factors:
Comfort and Visual Clarity
When determining the accurate power you need, eye doctors consider how much correction is needed for clear vision while maintaining comfort. While standard prescriptions are for the starting point, adjustments may be necessary to ensure comfort and clarity. Factors based on individual preferences like dominant eye and specific characteristics of different brands of contact lenses can also work.
Trial and Adjustment Period
During the trial period, you’re allowed to wear trial lenses. The lenses allow your eye care professionals to identify any necessary modifications to your prescription. The adjustment can be regarding comfort, clarity, and overall satisfaction.
Regular Eye Exams and Prescription Updates
Always go for regular eye exams, and ensure your prescription is up-to-date. A regular check-up is recommended as it helps determine if the prescription listed is still appropriate. Doing so, you position yourself for good eye health and great vision.
Summary
Most practitioners prescribe a soft lens because of its flexibility and comfort. However, considerations like tear film and the back surface of the lens must not be forgotten for optimal fit and comfort. Your eye care professionals can also consider your eyeglass prescription. A great piece of advice you must heed is to be aware of online suppliers. You must consult your eye care professional before purchasing lenses.