Definition and Overview

Eyeglasses are used to correct any vision problems, such as astigmatism, nearsightedness, and farsightedness. Vision correction is accomplished through the shape of the lens. Concave lenses curve inwards and are used to correct nearsightedness. Convex lenses, on the other hand, curve outwards and are used for farsightedness vision correction.

The degree of the curve and thickness of the lens will be determined by your eye condition. An optometrist will prescribe the exact type of lenses you’ll need for your eyeglasses after performing a series of vision tests.

Prescription eyeglasses are given by an optometrist. Although they are considered as medical professionals, they are not doctors. Eye doctors are called ophthalmologists and are qualified to treat different eye conditions and diseases. Optometrists focus mainly on vision services and prescribing corrective eyewear.

If you’re having problems with your vision, you will likely need to visit an optometrist to undergo an eye exam. The optometrist will determine the strength of the lenses you require and provide you with a prescription.

Once you have the prescription, an optician will help you decide on the type of frame that will look best on your face. Opticians are not authorized to perform eye exams or provide prescriptions, but they do work closely with an optometrist especially in an eye clinic or a place where you can purchase eyeglasses.

What are the types of lenses available?

Eyeglass lenses are made from a variety of materials. Each material has its own set of strengths, so if you’re purchasing a pair of eyeglasses, be sure to study which type of lens will be most beneficial to your situation.

  • Polycarbonate lenses – Polycarbonate is an impact-resistant material. Polycarbonate lenses are perfect for people who participate in sports or work in an environment where regular eyeglasses could be easily damaged.

  • High Index Plastic Lenses – These are mostly used by people who have higher prescriptions and require thicker lenses.

  • Trivex Lenses – These are also impact-resistant, but a bit thinner and lighter than polycarbonate lenses. These can be much more comfortable if you need to wear eyeglasses for long periods.

  • Multifocal – Some people have a combination of vision problems thus have different prescriptions. In some cases, the prescriptions can be combined in a single lens. If two prescriptions are combined, these are called bifocal lenses. If there are three prescriptions, it’s called a trifocal lens.

    You can also choose coatings for the lenses depending on your requirements. Coatings can help you see better in certain situations. Some of the common coatings available are:

  • Tinted – These can help you see better in well-lighted environments, such as during a sunny day, or when you’re in a room with many lights.

  • Anti-reflective – These are similar to tinted coatings but are specifically designed to help block out the glare from a light source.

  • Scratch-resistant – Almost every type of modern eyeglasses are scratch resistant, but you may want to make sure that the pair you’re interested in does have this type of coating.

How to read a prescription

An eyeglass prescription will usually first identify the left or right eye by the symbols “L” or “R”, or “OS” and “OD”. OS stands for ocular sinister which refers to the left eye, and OD for oculus dextrus, which is the right eye.

After that you’ll see a (+) or (–) sign and series of numbers. A (+) sign is a condition called hyperopia or farsightedness. Meanwhile, A (–) sign indicates nearsightedness or myopia.

The numbers after the signs refer to the dioptre, which is the required focusing strength of the lens. The higher the number goes, the stronger lens you’ll require. For example, a +1.00 means that you are farsighted and require a lens that is 1.00 strong.

People who have astigmatism are issued prescriptions in this type of format, Sph x Cyl x Axis. Sph stands for the degree of hyperopia or myopia as described above. Cyl refers to the degree of astigmatism. Axis is the orientation of the astigmatism.

Care of eyeglasses

Your prescription may change over a period of time, so you’ll need to visit the optometrist annually to ensure that your eyeglasses are still ideal for your eye condition. Nevertheless, you should always take good care of your eyeglasses. The lenses may be scratch and impact resistant, but this doesn’t mean they aren’t prone to damage. Additionally, dirt on the lens or a build-up of oil will still affect your vision, so make sure that you regularly clean the lenses using a non-lint cloth.


  • Eyeglasses and Contact Lenses – Stanford Children’s Health
Share This Information: