Leonardo Da Vinci had a vision. Actually his vision was for improved vision for people with less than perfect sight. He delved into the science of light and sight and devised a solution to eye defects. What was that science? How did Da Vinci come up with those conclusions? How did he envision the contact lens? We’ll answer those questions here with a look at how contact lenses work.
How does the eye see?
To best understand the science of corrective lenses, let’s first look at perfect vision – vision that doesn’t need correction. Perfect vision occurs when light rays converge at a point directly on the retina (the back of the eyeball). If light rays fail to hit that point at exactly the same point, then vision becomes blurry. So the purpose of corrective lenses is to refocus light rays so they do converge at that point on the retina.
Let’s look at defective vision – what happens when those light rays don’t hit that spot on the retina. There are a number of common eye, or vision defects. Two of the most common are myopia, or short-sightedness, and hyperopia, or long-sightedness. People with myopia can see clearly up close but not at a distance. Those with hyperopia see better at a distance than close up and sometimes experience difficulty bringing their vision into sharp, clear focus for reading and other close-up activities.
A couple of other well-known irregular eye conditions are astigmatism and presbyopia. A person with astigmatism has an irregularly-shaped cornea, which causes light images to focus on two separate points in the eye. Presbyopia is commonly known as an “ageing eye”. In this condition the eye loses its ability to shift focus between far and near objects. An example of difficulty caused by this condition is shifting focus between the road and the speedometer while driving.
So these are the problems that could arise with someone’s sight. However, with advancing contact lens technology, most common vision conditions can be treated with contact lenses, and in the last few years, many more options have been made available for treating each kind of problem.
What are contact lenses?
Contact lenses are small, thin transparent discs, designed to sit on your cornea and correct your vision. The cornea is the clear but tough covering of the central part of your eye. Because the surface is tough, it’s able to withstand the placement of the contact lens. You’d think that something that just rests on top of your eye would fall out, but not so. The moisture in your eyes acts as an adhesive, keeping the lenses in place. Your eyelids help to keep them in place, too, but to a lesser extent. But your eyelids do play an important role by keeping your contacts clean. Every time you move your eyelids, they ever-so-slightly move your contacts. This keeps them uniformly-covered in moisture, while at the same time, washing away any foreign substance that may have found it’s way between the lens and your cornea.
The actual shape of your contact lenses is determined by the actual shape of your eye. Of course, they have to be uniform, if the lens is to stay in place. So the inner surface of the lens is fit to the shape of your eye. The outer surface of the lens is designed in much the same way as your eyeglasses would be, although on a smaller scale – to help you see better.
The purpose of contact lenses is the same as eyeglasses – to correct vision defects. Many people find wearing eyeglasses a hassle, especially if they need them for a variety of activities. Taking them off and putting them on constantly throughout the day, as well as having them slide down their nose or fogging up in the wintertime, can be most frustrating. But with the creation of the contact lens, people could have the vision correction they needed without the hassle of eyeglasses.
Contact lens technology takes off
Originally, the first modern-day contact lenses were made of hard plastic, which was hard on the eyes and required a lot of maintenance to prevent irritation of the eye. A saline solution was applied frequently to keep the eyes moist.
Then came the development of soft flexible contact lenses. The range of possibilities expanded.
Soft contact lenses are made from a gel-like plastic that contains from 38%-79% water. Being softer, they’re more comfortable. And they last longer, too, some for up to a year with proper care.
There are a number of different types of soft contact lenses. Let’s look at some of the most common:
- Disposable lenses – replaced every day, every few weeks or every few months
- Daily-wear lenses – removed nightly
- Oxygen permeables (RPGs) – transmit oxygen; they don’t contain water, so they resist deposits and bacteria
- Color-tinted lenses – change the natural eye color
- Disposable contact lenses with ultra-violet absorber – protects against the sun’s harmful ultra-violet rays.
These are the most common types of contact lenses. There are also some specialty contact lenses used for special effects in movies. As time goes on, there’ll be many more.
The contact lens industry advances and prospers
Contact lens use is widespread these days. The industry is creating more and more different types and uses of contact lenses. Check with your ophthalmologist or optometrist to see which contact lens is best for your lifestyle – and see your way clear!
About The Author
Gareth Marples is a freelance copywriter providing valuable tips and advice for consumers ordering daily disposable contact lenses online including colored contacts and daily and monthly disposable contact lenses. His numerous articles offer moneysaving tips and valuable insight on typically confusing topics.
This article on "How Contact Lenses Work" reprinted with permission.
