The sight of people who wear glasses is so common today that it is easy to underappreciate the valuable role this simple vision-correcting technology plays in our well-being. A technique introduced by the Romans, pieces of glass were employed to change the refraction of light in ancient times so people could read small print more clearly. This was how the magnifying glass was invented.
The basic principle behind glasses is refraction, a term that refers to how light slows and bends when it passes from a light-density medium like air into a thicker-density medium like transparent glass. An easy way to observe the dynamics of refraction is by dipping a pencil into the water and witnessing how it no longer appears straight.
How Does A Lens Work?
Prescription eyeglasses work by bending light (refraction), before it enters your eyes to focus it perfectly on your retina. But to understand this, let’s first look at how the eye functions.
Your eyes perform a series of internal mechanisms that transfers light to your optic nerve to create images. The system comprises pupils, cornea, lens, and retina. When you look at an object, the following happens:
- Light from the object reaches your eyes as scattered rays.
- Your pupils dilate and contract to allow light into the retina at the back of your eye.
- If your vision is perfect, the scattered light is focused directly on the retina.
- Retina relays the reaction to light to the brain, where it is translated into an image.
You suffer from common vision problems when the lens fails to focus the light on the retina. Eyeglasses or other corrective lenses are frequently used to bend the light and focus it on the retina, helping everyone have a clear viewing field.
Near or Far? All of the Above?
Depending on the shape of the eye, people can have near or far-sightedness. For instance, if the pupil or cornea adjusts all the incoming light to focus in front of the retina, your distance vision is impaired, known as nearsightedness or myopia. Similarly, when the light is focused behind the retina, the items close to you appear indistinct, referred to as farsightedness or hyperopia.
Now, what happens if the cornea itself is misshaped? Yet another condition called astigmatism occurs when you suffer from blurred vision. Depending on the type of vision problem you suffer from, you will need different types of prescription glasses. Glasses of different thicknesses and shapes compensate for the various vision problems.
Concave Lenses
Thin at the center and thick at the perimeter, the concave-shaped lenses are used to correct nearsightedness (myopia).
Convex Lenses
Thickest at the center like a magnifying glass brings the eye’s focus forward to correct farsightedness (hyperopia).
Cylindrical Lenses
These glasses correct astigmatisms with asymmetrical thicker or thinner portions.
Another type of lens rising in popularity these days is progressive lens. The progressive lens helps people suffering from both nearsightedness and farsightedness. This happens when each of your eyes develops its own conditions.
You can be nearsighted and farsighted to varying degrees in each eye.
People between the ages of 35 and 40 should consider getting progressive glasses that help you have a single pair of glasses for all your vision needs.
Lens Materials
The material from which a lens is made rarely impacts the corrective power of the lens. However, it can have a major effect on your lifestyle.
Hi-Index
Hi-index lenses are made of a unique plastic material that refracts light differently than regular plastic lenses. It helps correct vision with less material, making the lens much thinner, allowing the glasses to be more cosmetically attractive and appealing.
Polycarbonate
Polycarbonate lenses are made from impact-resistant plastic. These lenses are thinner, lighter in weight, and often have built-in UV protection.
Trivex
Another similar material is Trivex, but it comes with higher-quality optics, meaning clearer vision. Trivex is also more rigid, making it an ideal option for rimless or drill mount frames.
Atmospheric
Aspheric lens design offers several advantages. Featuring flatter peripheral curvatures than a regular spherical lens, it eliminated the lens bulging out of the eyeglass frame, which improves cosmetic appearance. Flatter peripheral curves also reduce distortions, making vision much crisper.
Get the Right Eyeglasses
Once you get a new pair of eyewear, it will take some time to adjust to them, in most cases, about two to three days. It is common to experience discomfort, headache, neck pain, and light sensitivity for a few days. However, if it continues for a few weeks and worsens, consult your optometrist to ensure the prescription is correctly suited to your needs.
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