Contact lenses and glasses are some of the important vision aids that we require to correct our refractive errors. People often choose both glasses and contact lenses to correct myopia, presbyopia, or hyperopia at different points in time. For many people, eyeglasses and contact lenses can be a bit confusing.
Are contact lenses the same as glasses?
It’s common to get confused among glasses and contact lenses since both of them are used to correct vision errors. However, it’s not true.
To understand how each of these work, continue to read further.
What makes prescription glasses different from lenses?
Both prescription glasses and contact lenses are created using different materials. The contact lenses are made using hydrogen or silicone hydrogen. The material is helpful in keeping the lenses moist and provides more oxygen transition through the contacts into the eyes.
While eyeglasses are made out of a bunch of different materials. From plastic to now sustainable alternatives; bio-acetate, metals, wood, and others. The recently manufactured glasses are more lightweight, thinner, and offer improved scratch-resistance.
Contact lenses and glasses different based on their positioning with respect to the eyes. Contact lenses are placed inside the eyes, directly over the lens while glasses for fashion and prescription are positioned around 12mm away from the eyes, over the ears.
So, the prescription of both glasses and contact lenses is measured and manufactured differently. You’ll also have to give different types of eye tests for getting a new pair.
Usually, the prescriptive power of the contact lenses is mostly less nearsighted than eyeglasses. Thereby, the power of the contact lenses is lower than the prescription of eyeglasses due to the distance of the lenses from the eye’s surface. Additionally, if you wear multifocal glasses such as varifocals or bifocals, then you’ll also have to get multifocal contact lenses. Similar to glasses, contact lenses are also designed to be bifocal and multifocal.
To help you better on this matter, always consult your optometrist first before trying to contact lenses and always choose eyeglasses based on their recommendation.
Is it possible to use an eyeglasses prescription to get contact lenses?
No! The prescription for eyeglasses significantly differs from contact lenses. An eyeglasses prescription won’t be correct and must not be used to get contact lenses. Your eye prescription cannot be used interchangeably. And people who wear or require eyeglasses don’t always wear contact lenses. To get an accurate prescription for eyeglasses and contact lenses, make a visit to your local optometrist and get your eyes examined to understand if you require contact lenses or not.
Note: If you plan to wear both eyeglasses and contacts at different times based on your needs, you’ll have to get two different prescriptions.
How to read prescription glasses?
When you buy designer glasses online, the retailers often ask for your prescription to understand your eyesight, vision problems to offer the correct lens. Eyeglasses prescription helps to read and comprehend the vision error to enable the optometrist to recommend the accurate measurement to correct the vision.
Here’s how to understand glasses prescription –
Abbreviations – The numbers mentioned on your prescriptions, often placed under the abbreviated headings, namely OS, OD, and OU. These are Latin abbreviations and stand for oculus sinister (OS), oculus dextrous (OD), and oculus uterque (OU), respectively. OS is for the left eye, OD for the right eyes while OU is for both of the eyes.
Signs – There must also be “+” or “-” signs on your prescription. If you have a nearsighted vision and require distant vision, your focus power would be donated with “minus” (-) in front of the number. But, if you are farsighted, then a “plus” (+) sign would be mentioned to signify correction required for near vision.
Numbers – You must have noticed a few numbers on the prescription, right? The numbers refer to the focusing power of the lenses that your eyes require. The numbers are represented in diopters, often abbreviated and written as only “D” alongside the number. A diopter is a measurement unit of the correction or the focusing power of the lenses.
For instance, let’s say if your glasses prescription says -2.00, it means that you are nearsighted, and require a lens with focus power of 2 diopters. People with astigmatism have different prescriptions compared to the single vision one’s.
To understand the prescription for astigmatism, you must know the degree of astigmatism you have and also the difference in curvature. Astigmatism prescription comes with three numbers, mostly written as S x C x Axis. Let’s understand this in more detail.
S (“Sphere”) – The S represent the degree of nearsightedness or farsightedness
C (“Cylinder”) – The C can be a negative or positive number. It’s responsible for the degree of astigmatism a person has and is represented in diopters. The bigger the number is, the higher astigmatism you have.
Axis – It informs about the orientation of astigmatism. The number falls between 0 and 180 degrees.
How different is the prescription of glasses to contact lenses?
Based on both of their sizes, the focusing power of the lenses is quite different as mentioned before. The focusing power can also differ majorly depending on the degree of the refractive error and the type of contacts required. Plus, the prescription of the contact lenses comes with an additional specification that isn’t present with glasses.
Here are the additional specification present in contact lenses –
Base Curve – The base curve or abbreviated as BC refers to the curvature of the back surface of the contacts. It’s determined by the shape of your cornea, thus these are perfectly shaped, neither too tight nor loose.
Diameter – Abbreviated as DIA, the Diameter in the contact tells the overall size of the lens.
Date of Expiry – Your contact lenses come with an expiry date. So to use them after a while, you must check if they’ve expired or not. The lenses themselves don’t expire, it’s the saline solution that the lenses are kept in often comes with expiring dates. It is usually 1-4 years after manufacturing.