Commonly known as contacts, contact lenses are affordable visual aid devices used to treat various forms of myopia and hypertrophy. They are thin, finely crafted curved plastic or glass discs made to conform with the wearers’ cornea and the eye’s curvature. They are used to correct refractive errors by providing an artificial refracting surface to the eye. Apart from the cosmetic advantage they provide over glasses, contact lenses provide much better peripheral vision, a quality which has made contact lenses the top choice for people involved in kinesthetic jobs. Contact lenses trump glasses when it comes to image distortion too, due to the comprehensive way the lens is fitted, giving people who need to use glasses for anything else than reading, a much better choice. They help wearers to have a field of vision that is more natural as they are moving with the eyes and being closer to the eye they are correcting the refractive errors near the eyes. The surface tension of the tear fluid of epidermis of the eye’s. Eyelid pressure also helps keep them in place, while blinking is lubricating the cornea and it’s flushing away all the debris that is accumulated on the lens.
Glass contact lenses were the only form of contact lenses from when F.E Muller, a glassblower made the first wearable contact lens in the late 1880s until the early 1930s when Perspex (commonly known as Plexiglas) was invented allowing optometrist William Feinbloom to make a much lighter and smaller contact lens. The ’60s saw mass production of contact lenses made of glass and plastic composite. As Neil J. Bailey, OD, PhD. famously said “silicone contact lenses are the lens of the future and always will be,”
Today, contact lenses are used to correct all types of refractive defects of the eyes like farsightedness, nearsightedness, presbyopia, and astigmatism. For astigmatic especially, they are a boon as glasses cannot change the curvature of the cornea, but a specially crafted lens, usually made in a tapered form can restore their vision to normalcy. However, cases of corneal damage have been cured by using rigid or glass contact lenses.
How contact lenses work
We’ve already established how contact lenses correct the refractive index of the eye, now we’ll see how that pans out in different scenarios. The concept of how we see is simple, light rays bounce off everything around us and light rays enter through the cornea and meet at a certain point on the retina, known as the focal point. Problems with vision occur when the rays fail to converge at the focal point of the retina. Depending on the vision type defect one suffers from, contact lenses help refocus the converging light rays back on the retina. In this regard, contact lenses are the same as glasses. While a glass’ strength is measured in power, the strength of a contact lens is measured in diopter which is a measure of the light bending ability (refractive index) of the lens. The higher the diopter, the stronger is the lens.
Natural nearsightedness is caused by the eyeball being oblong i.e too wide, resulting in the rays converging not on the retina, but in front of the it. People with nearsightedness can see things which are close up normally, but can’t see things farther away. Thus, a concave lens is used to correct their vision. A concave lens tapers towards the middle, i.e is thinner in the center than it is at its edges. Since they’re tapered at the center, they help into spreading the light throughout the body of the lens and adjust the focus back to the retina’s focal point. The power of the lens and the deficient eye power is the same in absolute terms, but the sign is reversed.
Naturally farsighted people can see faraway objects clearly but are unable to see objects which are up close. In this case, the eyeball is too short resulting in the focal point being formed at the back of the retina. Thus, farsightedness is corrected by convex contact lenses, they’re the thickest at the center and taper towards the edges. This nature of construction allows them to bend towards the center, moving the point of focal forward into its appropriate position.
Special lenses, called toric contact lenses are used to correct astigmatism. Astigmatism is a condition which causes the cornea to have several irregularities across its surface, resulting in a weak focus occurring on too many places on the retina. Toric lenses are custom made for each person, with the specimen calibrated so as to confirm the irregular cornea. They are thicker at the bottom and taper towards the top, thus must be laced in a certain manner in the eye.
Colored contacts, despite popular perception, are not simply cosmetic in nature. Most of them are hybrid in nature. That means that the contacts are colored and have a refractive correction as well. The color of the eye depends on the amount of melanin on the iris’ surface, melanin is the same dark pigment that decides skin color. Most opaque lenses are having colors applied to them in the same patterns as they are present in the eye. The opaque color of the lens, when used, covers the eye’s natural color completely. Tinted lenses, on the other hand, are translucent in nature which means they allow the color of the wearer’s eyes to show through. They generally work on eyes that are light colored, but in the case of dark-colored eyes, the results are always somewhat off what is desired.
Advantages of contacts
Though most people choose contact lenses as they are dissatisfied with their appearance with glasses, contact lenses present several advantages over glasses as they are rarely in danger of slipping off, fogging up or getting wet, as well as being much harder to lose. Ages hyperopic patients and those who’ve had cataract removal procedures done reportedly feel much better-wearing lenses than glasses. This holds true for people with changed corneas also. Sportsmen and women obviously find contacts better than glasses, but a lesser know athletic use is the enhancement of normal vision, resulting in much clearer eyesight. This is made possible by the lens being tinted in a manner so as to block certain wavelengths from reaching the eye, making details much finer They’ve been dubbed as “Super Lenses for Superstar Athletes”. This technology has now been made available to the masses in the form of amber and gray-green lenses. They’re meant to shield the eyes from harmful UV ray exposure with the amber one blocking out the blue wavelength and heightening the red meant to be used for fast moving sports like baseball, football, and soccer. The green-gray one is better suited for slow-moving sports such as golf, which are played out in the open under bright sunshine.
All said contact lenses are amazing medical marvels that work wonders for the visually impaired.
