It is often argued that eyeglasses- though one of the most important inventions in the medical industry- are a thing of the past. They often slide down your nose and can get misplaced easily. A contact lens is one of the most remarkable upgrades to eyeglasses in the past century. Contact lens removes the deficiencies in traditional eyeglasses while retaining their use at the same time. In fact, for millions of people who wear them, it is a preferred choice for many reasons- simple, compact, easy to use and more efficient. Contact lens provides a much better peripheral vision than normal eyeglasses and helps keep your eyes more relaxed while reading and focusing. It also helps to reduce fatigue and eyestrain. A contact lens moves with your eye which gives it an insurmountable advantage over its old-school rivals- that you can always look through the center of the lens, providing you with the best vision. In contrast, wearing eyeglasses can sometimes distort your vision too, since the lens in traditional glasses fails to provide the same quality at the edge as compared to the center. Contact lens also gives a more natural appearance and minimizes the size differences with better visual acuity, which means it is possible for you to read smaller letters on the eye chart.
A short history of contact lenses and their evolution to present form
The idea of putting corrective lenses on the eye to achieve better vision is not new. Legendary scientist and artist Leonardo da Vinci first conceived this brilliant idea around half millennia ago, which can be seen from detailed drawings and descriptions available from his works. Later, a Zurich scientist A. E. Fick manufactured the first contact lens in 1887. Even though the progress was remarkable, glass lenses weren’t very easy to use. It took a major innovation in the 1940s to produce plastic lens- made of a material called PMMA, which in fact is so adaptable to the human eye that it is still used for hard contact lenses, intraocular lens implants and orthopedic purposes. Soft contact lenses became available in the United States in 1972 and were more comfortable than the hard lenses available at that time. Since 1972, contact lenses have changed and improved considerably. Now, lenses are designed to correct almost any vision problem and are available in special designs for extended wear, cosmetic changes (like eye color), and disposability.
Types of Lenses
Hard and Soft lenses
In general, contact lenses can be divided into two major categories: hard and soft. Hard contacts have evolved significantly since their introduction in the 1940s. Initially, their design improved as manufacturing techniques improved, but major developments took place in the late I970s with the introduction of modified hard contacts. These lenses are called rigid gas-permeable contacts.
RGP lenses are flexible and fit better than earlier hard lenses, while also lasting longer and sometimes provide a better vision than soft lenses. They’re manufactured by computer-controlled algorithms that can create any kind of surface needed to correct one’s vision. RGP lens materials also allow for bifocal segments to be added. Because RGP lenses move significantly on the eye with a blink, these lenses can move the bifocal segment up so that it sits in front of the pupil while you’re looking down to read. Another significant advantage of RGP lenses is that they can provide a new cornea for people with a corneal problem that distorts vision.
Soft contact lenses are often referred as hydrogels since they’re made of a plastic material that holds water. By varying the amount of water that a lens can hold, manufacturers provide a broad assortment of materials for fitting. Water contents usually range from 38 percent to 79 percent. Soft contacts are available to correct myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and even presbyopia (loss of ability to focus at near distances). Computerization and automation of lathing and molding soft contact lenses have made for extremely accurate soft lens prescriptions.
Daily-Wear vs Extended-Wear Lenses
Daily wear lenses are designed to be put in when you wake up and be taken out before you go to sleep. All such lenses are made to provide enough oxygen to the cornea for the eye to breathe while its open. However, they are not appropriate for overnight wear.
Extended wear refers to any lens worn longer than twenty-four hours. These lenses are made to provide enough oxygen so that the eye can breathe even while you’re sleeping.
Disposable and Frequent replacement lenses-
With the improving technology, in addition to normal single-pair lenses built to last for a long time, there are soft contacts packaged for a frequent replacement and are disposable in nature. Disposable extended wear lenses are meant to be worn only once for a week at a time. Since extended wear lenses are expensive and often at risk of being worn away, disposable lenses are low-cost, safe and efficacious. Frequent- replacement lenses are designed to be replaced every few weeks so that they may be cleaned and re-used. This avoids any chance of infection due to an accumulation of bacteria in lens-area.
Which Lenses Are Right for You?
The first step in deciding which lenses to choose is to analyze the requirements of your eye and determine whether your eyes are healthy. An important part of this evaluation is your health history, which includes having any eye diseases such as dryness, chronic infections or corneal dystrophy. These diseases may interfere with contact lens wear. Further, it is also necessary to know if there are any functional problems with your eyes- such as a muscle imbalance, issues while focusing etc. Some other important questions include whether any medications are being taken which may cause dryness in eyes (or otherwise interfere with contact lens wear) or if there are any environmental allergies or sensitivities to preservatives (can affect the ability to use such lenses).
Another aspect of this evaluation is to determine whether your lifestyle and work tend to suit contact lens wear or not. Finally, it a good idea to clarify your goals and expectations with contact lenses. For instance, wearing contacts for competitive swimming may not be realistic, because of the chemicals and bacteria found in swimming pools. If your goal is to use extended wear soft contacts because you travel extensively on your job and don’t want the trouble of taking contact lens solutions with you, this may be a fine idea so long as your eyes are able to tolerate contact lenses.
Getting the Right Fit
Having a good fit is essential because it allows the contacts to give you the best vision possible. To ensure a good fit, your eye doctor needs to measure the corneal curvature and diameter for each eye. This curvature measurement taken from an instrument called a ‘keratometer’ helps to determine the right curvature of the back surface of the contact lens. It is also necessary to consider any surface irregularities on your eye that might affect a good fit, such as any bumps or elevations, corneal diseases etc. Apart from this, a standard testing procedure also includes examining eyelids, and inspection of quantity and quality of tears (useful since it helps in determining the amount of water required to be held up by lenses).
Author’s bio: Dr. Babak Shabatian, MD, is an ophthalmologist and founder and director of Cali Eye and Laser Institute. Dr. Shabatian practices comprehensive ophthalmology with a focus on advanced cataract surgery and LASIK.He has performed thousands of procedures with excellent and predictable results. He is frequently invited to lecture on topics of refractive and advance cataract surgery.