Although you can decide on what type of frame you want for your glasses, you don’t get to decide on the prescription lens that you would need. Despite vision-correct surgery or contact lenses, eyeglasses are still a popular choice for many.
There are different types of lenses for glasses, such as single vision, progressive, bifocal, trifocal, and more. These lenses have various functions, and depending on your eye condition, your optometrist will prescribe you the right lenses best fit your needs.
How will you know the right lenses for you with so many types of lenses available to correct one’s vision?
Brief History of Eyeglasses
The inventor of the first eyeglass is yet to be discovered. It is said that Romans were the first to use a glass globe of water to see tiny objects, but it was the monks who created the “reading stones” by refining domes of transparent quartz in the 10th century.
Historians believed that artisans in Italy were the first to form eyeglasses shaped like two magnifying glasses fixed into a bone mounting that could be perched on the nose bridge.
The first eyeglasses back then were only used to correct hyperopia and presbyopia. Glasses for myopia appeared in the 1400s. The first wearable eyeglasses became a status symbol because they were made of expensive materials such as crystal. But when the printing press launched in 1440, demand for reading glasses skyrocketed, and the material was switched to glass, making these spectacles more affordable.
Glasses have become hands-free in the 1700s. At the same time hinges were created so glasses could be folded and stored easily in the pockets; Benjamin Franklin contributed to the invention of bifocals. Cylindrical glasses came along in the early 1800s to correct astigmatism. Still, the standardized vision correction with the “big E” chart was only invented by Doctor Herman Snellen in 1862.
Understanding Different Vision Problems
The human eye is a complex organ and can go through different sight problems. But some of these issues can be corrected through surgeries or wearing eyewear, such as eyeglasses.
What are the common vision problems can an eyeglass correct?
Astigmatism is a condition where there is an irregularity in the shape of the cornea, causing blurred vision. This condition prevents light from focusing correctly on the retina resulting in blurry vision at any distance.
A person can have astigmatism if the front part of their eye is shaped more like a football than a basketball. Astigmatism is often caused by an irregularly shaped cornea or a curved iris that doesn’t fully open to let light into the eye.
There are various treatment options for astigmatism depending on what type you have and what other conditions you may have.
Myopia is a condition where people have a hard time seeing objects that are not close to them.
Myopia can affect kids and adults or people of all ages. It’s because the eyeball becomes too long, and the lens becomes stiff and thick, increasing nearsightedness (and decreasing eyesight at a distance).
Hyperopia is a vision condition that leads to people being farsighted when they have poorer visual acuity at close distances.
Individuals with hyperopia have an easier time seeing things that are closer to them because their eyeball is too short. It’s a pretty common eye disorder found in children.
Presbyopia, or aging eyes, is a condition where the eye’s lenses slowly lose their ability to focus clearly on texts on printed objects but not affect the vision at a distance. Presbyopia is not something one can prevent by changing lifestyle as it’s part of aging.
However, it is treatable by using prescription glasses such as progressive, bifocal, trifocal, or single-vision reading glasses.
Different Types of Lenses and Their Characteristics
The prescription of the lenses depends on the person’s eye condition and the type of lens they need. There are two primary types of lenses: single vision lens and bifocal lens. Single vision is recommended for people with issues in one eye, while bifocal lenses are recommended for people with presbyopia who experience difficulty reading text up close.
Aside from these two common types of lenses, other options will correct various eye conditions, and we will explain them more in detail.
There are also different types of coating available on these lenses, including anti-reflective coating, ultraviolet protection coating, scratch-resistant coating, etc., which can protect your eyes from harmful UV rays, scratches, and glare from light sources.
There are many different types of lenses for your glasses to choose from. The most important thing is to find the right lens type for your needs.
Single Vision Lenses
Single vision lenses are the most common type of prescription glasses. These lenses are created to assist individuals who need correction for a specific vision zone: nearsightedness and farsightedness.
Distance glasses and reading glasses have single vision lenses for people who have trouble seeing from neither near nor far. Reading glasses helps you to see things up close if you are farsighted (hyperopic). On the other hand, distance glasses can help you see things beyond arm’s length if you’re nearsighted (myopic).
For example, if you struggle reading a message with your phone or computer, single-vision reading glasses will help correct your eyesight. However, if you have difficulty seeing traffic signs while driving, you might be prescribed single vision distance glasses.
Benefits of Single Vision Lenses
Beyond restoring or correcting your ability to see clearly, here are other benefits to wearing single vision lenses:
- Boost quality of life because of improved visual health and perception
- Like all types of glasses, it also protects your eyes from trauma or common irritants
- It helps relieve eye fatigue and migraines
Types of Single Vision Lenses
Single vision lenses have a few different options for vision correction:
- 1.59 Polycarbonate Single Vision. These lenses are durable and include an anti-reflective or anti-scratch coating. It is light and thin compared to plastic lenses, and it offers protection against ultraviolet radiation.
- 1.57 Mid-Index Single Vision. These lenses are 15% thinner than traditional plastic lenses but not as thin as polycarbonate lenses. This lens is the ideal option for people with higher prescriptions.
- Polarized Single Vision. These lenses have a vertical filter that prevents glare from passing through. It protects the eyes from the light bouncing off highly reflective surfaces.
Generally, single vision lenses have a thickness ranging from 3-4mm, depending on the frame’s size and material. Single vision lenses for farsighted are thicker at the center compared to lenses for nearsighted wearers.
These lenses are used for individuals who are both nearsighted and farsighted. Bifocal lenses contain two lenses allowing you to see objects at all distances. It is commonly prescribed to people over the age of 40 where the eyes begin to have difficulty focusing on things from multiple distances.
In the lower part of the lens, a small portion has the ability to help with your nearsightedness, and the rest are for distance vision. This lens segmentation focused on correcting near-vision comes in various shapes:
- Round segment
- D segment or half-moon
- Ribbon Segment
- Executive or full bottom half
When wearing glasses with bifocal lenses, a person will have to look up through the distance part of the lens to see objects that are far away. And to focus on things near you or while reading, a person will have to look down through the small segment of the lens.
The Pros of Bifocal Lenses
- Cost is lower than progressive lenses
- These lenses can fit in any frame
- It can be manufactured using any lens material such as plastic, glass, or polycarbonate
- Bifocal lenses are be made with any type of coatings such as photochromic, hardening, and anti-reflective.
The Cons of Bifocal Lenses
- Bifocal lenses can only help with farsightedness and nearsightedness, lacking the intermediary who can cause problems when using the computer.
- People with bifocal lenses will have to go through an adjustment period to get used to wearing them.
Compared to a single vision and bifocal lenses, trifocal lenses correct three vision problems: near, intermediate, and distance.
Glasses with trifocal lenses have two lines on the lens, which is the most basic type. The top part corrects the vision for farsightedness, the middle for intermediate image, and the lowest part for nearsightedness.
Cataracts and presbyopia are two of the few eye conditions that might require you to use trifocal lenses to address this condition.
The Pros of Trifocal Lenses
- You’ll get all you’re three vision problems corrected. Its ability helps people to see objects clearly at different distances.
- Allows people to have a broader view for nearsighted and intermediate vision compared to progressive lenses. Trifocal lenses make it easier to see and read what is on the computer screen.
The Cons of Trifocal Lenses
- This type of lens can’t be customized, unlike other eyewear.
- It would take a couple of days or weeks of adjustment, which is expected, so it’s recommended to wear it all the time to speed up the process.
Trifocal lenses include multiple prescriptions and should be specifically created depending on your vision needs. Ensure that you are guided and checked by your optometrist to guarantee that this lens is the right one for you.
Progressive lenses are multifocal lenses without the lines. It almost has the same look as single vision lenses. Progressive lenses allow people to see clearly without the lines visible in bifocal and trifocal lenses.
These lenses have a unified progression of magnifying power for intermediate and near vision. It provides correct lens power for seeing things clearly at any distance. Compared to bifocals and trifocal, these lenses have a more advanced design.
Anyone can wear glasses with this lens. However, it’s used mainly by people age 40 and above who are farsighted. Meaning their vision is blurry when they are reading. Children can use this lens to help prevent myopia.
Advantages of Progressive Lenses
One of the main advantages of progressive lenses is not needing more than a pair of glasses to correct specific vision problems. So, there’s no need for you to switch glasses if you’re reading or driving.
There is also a smooth transition when seeing things at different distances. When you’re driving, if you switch to watching the road to your dashboard, you won’t experience the “jump” that you usually get when wearing bifocals or trifocals.
Drawbacks of Progressive Lenses
With progressive lenses, it will take for people to adjust, similar to bifocal and trifocal. You are required to train yourself when looking at the lower part of the lens to read, to look straight for distance, and to look in between when you’re doing some computer work.
While you are on the adjustment period, you might experience nausea just by looking at the wrong spot on your glasses. Your peripheral vision can also get distorted while adapting your new glasses, and it costs more than trifocal lenses.
Progressive lenses are best for anyone who needs their vision corrected at all distances – near, intermediate, and far. It’s also a lens of choice for people becoming presbyopic or gradually losing the eye’s ability to see objects from up close.
Prism lenses are used to treat vision conditions like double vision. Prism lenses are prescribed to treat Binocular Visual Dysfunction (BVD).
Prisms are made of plastic or glass to break up lights into a spectrum or change the reflected light. These lenses are infused into regular lens prescriptions and don’t help with correcting refractive errors.
Prisms deceive the eye into thinking that an object is in a different position to improve eye alignment. Similar to what a single vision lens can achieve, this will help improve one’s binocular vision, lessen double vision, headaches, and other issues that come with eye vision problems.
Prism glasses are prescribed for individuals with the following conditions:
- Regular headaches
- Eye strain
- Eye turn or Strabismus, which causes a challenge in combining two images
- Tiredness when working on the computer
Side Effects of Prism Glasses
Prism glasses are reasonable solutions for double vision correction, but a person might experience side effects when wearing these types of lenses.
- Pain that comes with eye movement
- Wandering or misaligned eyes
When one is wearing prism lenses, alignment is critical as they might not work correctly. These lenses require professional adjustment, and it is easy to fix.
Toric lenses or toric are commonly used in eyeglasses and contact lenses to fix astigmatism. It has a different focal length and optical power. One part of the lens is spherical, while the other is formed like a cap.
Toric contact lenses are either made of hydrogel or silicone hydrogel. The silicone hydrogel is more breathable than the traditional hydrogel and can cost more.
One important thing to note about toric lenses compared to soft lenses is that they focus on multiple parts of the lens to correct eye vision problems such as nearsightedness or farsightedness that comes with astigmatism.
Not all eyes with astigmatism are the same, and it will take a few trials and errors to find the right toric lenses to aid with your vision.
What are the Materials Used for Eyeglass Lenses?
Most eyeglass lenses are made of plastic. However, they can also be made of glass or other types of plastics like polycarbonate. Plastic lenses make it easier to make the shape for eyeglasses because it is lighter and stronger than glass. Let’s explore on these materials:
- Glass lenses were used in the early days of vision correction as they offer remarkable optics. However, it’s heavy and can break easily that can cause serious eye injury, so it’s no longer commonly used.
- Plastic lenses, which is first developed in the 1940s, are a lighter alternative to glass lenses, which is half of their weight. Plastic lenses are inexpensive, and it is impact-resistant compared to glass lenses.
- Polycarbonate lenses, on the other hand, were introduced in the 1970s. It is lighter than regular plastic lenses and is an excellent material for sports eyewear, kid’s glasses, and safety glasses.
- Trivex lenses, introduced in 2001, are a good substitute for polycarbonate lenses because of their impact resistance characteristics and much lighter weight of about 10%. Trivex lenses also produce sharper vision compared to polycarbonate lenses.
- High-index plastic lenses refract light more proficiently than glass or plastic lenses. This material has a higher index of refraction which produces thinner glasses. This material is beneficial for a higher prescription for nearsightedness, farsightedness, or astigmatism.
When someone needs glasses, they should find out what type of lens material is best for them. This depends on what the person wants their glasses to do, how much they are willing to spend, and what style they want their glasses to have.
Essential Features of Lenses for Glasses
Aside from various types of lenses for glasses, there are also features that you have to understand with regards to these lenses:
Index of refraction
The refractive index is an indicator of how effectively the lens material bends light. The higher the refractive index, the slower light travels through it, resulting in a greater focus of the light rays.
A lens material with a high refraction index will have a thinner lens than a material with a low refractive index. The most common eyeglass lens materials being used today are between 1.498 (CR-39 plastic) to 1.74 (high-index plastic).
Determines how much chromatic aberration or chromatic distortion does the lens produces. It is an occurrence where light rays pass through a lens focus at diverse points.
The range of abbe value for eyeglass lens materials is between 59 (glass) to 30 (polycarbonate). A low abbe value will result in noticeable chromatic distortion.
Glasses with aspheric lenses are slimmer and more striking compared to regular lenses. It is flatter than traditional lenses and results in lesser magnification.
Aspheric lenses enable the use of flatter arch when creating eyeglass lenses and improve peripheral vision. These lenses also make the person’s eye look more natural in terms of appearance and size.
High-index plastic lenses are mostly aspheric to improve the look as well as its performance. For polycarbonate or plastic lenses, aspheric lenses can be an option with additional cost.
Edge and Center Thickness
The Food and Drug Administration (FDA) issued a guideline on lenses’ impact resistance for eyeglasses in the USA. Due to this, the thinness of the lenses is limited.
Polycarbonate and trivex lenses are highly impact-resistant, and they can have a center thickness of 1.0 mm, which still follows the FDA standard. And for lenses that correct myopia, the material to be used should have a thicker center to pass the FDA guidelines.
If you have a higher prescription, the thickness is more noticeable, but the size and the shape of your glass frame also affect the width of the lenses. So, if you want to decrease the thickness and reduce weight, a more petite frame is recommended.
Are Expensive Eyeglass Lenses Worth It
For most people, eyeglasses are a necessity. Multiple factors contribute to making eyeglasses expensive: the frame and the manufacturing cost, and sometimes it’s the designer label you are paying for and not the actual lens.
Yes, it can be worthwhile to invest in suitable frames because the most expensive part is changing them every year or few years. Lenses don’t cost much as a whole new glass, so for it to be more affordable and sustainable, buying a reasonable quality frame is a better option, and then just change your lenses every year.
You can opt for an economical option, such as over-the-counter reading glasses, but this doesn’t help correct your vision because it only helps magnify the texts you’re reading. It might not be harmful to your eyesight, but you may experience eye strain or headaches when you use them as your regular glasses.
It is wiser to invest in a good pair of prescription lenses, so you don’t have to switch pairs whenever you are doing multiple tasks like driving or you’re in between reading and watching television.