Centuries ago, individuals born with poor eyesight often had to struggle with the side effects of refractive errors indefinitely with no true way to seek relief. In modern times, however, we have several ways of addressing poor eyesight. Corrective lenses, like glasses and contacts, have been used with large success for many years. While the crude beginnings of glasses date back thousands of years, modern science in the field of vision correction is a relatively recent occurrence.
Techniques to correct one’s vision have been around for millennia. We had this whole section written about it but then we realized it was really, really boring so we cut it. Moving on…
Converging vs. Diverging Lenses
Converging lenses are often referred to as plus lenses or positive lenses and have at least one convex surface. Some have two convex surfaces and others have one convex surface and one flat surface. Regardless of style or shape, converging lenses are thicker in the middle than on the sides. They allow light waves to penetrate the thick middle of a lens at a single point before diverging to produce an inverted image. Converging lenses are often used to correct hyperopia and presbyopia.
Diverging lenses, also called negative or minus lenses, have at least one concave surface and are thinner in the middle and wider on the edges. Diverging lenses allow light waves to spread out once they penetrate the lens and are often used to help correct myopia.
Spherical vs. Cylindrical Lenses
Both converging and diverging lenses can be either spherical or cylindrical. Spherical lenses are more common and have two completely symmetrical spherical surfaces, causing light waves that are parallel to the lens axis. Cylindrical lenses are uniform and cylindrical in shape, hence the name, and are used to correct unequal refraction from the cornea in refractory issues such as astigmatism.
Rigid Gas Permeable (RGP) Lenses
Rigid Gas Permeable (RGP) lenses are hard lenses that can also be used to treat many vision problems. Prescriptions for RGP lenses are similar to soft lenses. Many of the same measurements, such as power, base curve and diameter, are used in both RGP and soft lenses. Soft lenses are malleable and can be manufactured to fit comfortably over the typical cornea in a roughly uniform manner. RGP lenses, on the other hand, must be specifically measured and designed to fit the eye precisely. Due the precise measurements that must accompany the production of RGP lenses, there are generally more detailed numbers assigned to RGP lens prescriptions.
The brand in an RGP lens prescription generally doesn’t indicate an actual brand but rather the material used to manufacture the lens. While soft lenses are mass produced, RGP lenses are custom made in a lab specifically for each patient. Companies that make the plastic polymers for RGP lenses do so in bulk and ship plastic polymer rods to production labs that in turn produce the individual lenses. To make the RGP lenses, the manufacturer will shave a small circle of plastic off the end of a rod and grind it to meet the parameters noted in a particular prescription.
Some measurements, like power, are similar between soft and RGP lenses but there are factors that differ between the two. For example, the base curve of a rigid lens is more specific than in a soft lens and thus is measured in hundredths of millimeters rather than simply millimeters. The average base curve for a rigid gas permeable lens is between 7.00 and 8.5 millimeters, although this varies from person to person. Base curve, diameter, and other measurements are required for RGP lenses.
Health care for your eyes is just as important as regular physicals and exams for the rest of your body. There are three different kinds of eye doctors who specialize in eyes. They are optometrists, ophthalmologists and opticians.
Ophthalmologists are eye doctors who attended medical school, experienced clinical rotations and underwent at least four years of specialized residency, occasionally preceded by an internship year. They are licensed MDs (Doctor of Medicine) or DOs (Doctor of Osteopathic Medicine) and are trained to diagnose and treat vision problems and perform eye surgery when necessary. Some ophthalmologists receive additional training in more specialized areas of eye care, such as retinal or corneal surgery. They are all certified by a national board and held to rigorous standards to ensure the highest level of care possible.
Optometrists are eye doctors who hold a Doctor of Optometry (OD) degree. Optometrists receive an undergraduate degree and then go on to attend a four year optometry school program. Optometrists diagnose and treat disorders of vision and diseases of the eye. Optometrists prescribe glasses and contact lenses as well as medications to treat eye diseases. Optometrists in some states perform some surgical procedures, but typically refer patients who need complex surgeries to an appropriate ophthalmologist. Optometrists also must be certified by national and state boards and are also held to rigorous standards to ensure high levels of care.
Opticians, unlike ophthalmologists and optometrists, are not doctors. Most opticians have a high school diploma and a two year technical degree from a community college or university. They are not permitted to diagnose, prescribe or treat eye disorders. Instead, opticians specialize in fitting glasses, choosing frames and ensuring prescribed products fit and functions properly. Although opticians do not prescribe corrective lenses, they are aware of the different measurements and their meanings in order to make sure glasses and contacts fit appropriately. While some opticians are licensed, there is no national board regulating the education and care provided by an optician.
Many people are quite unhappy to learn that they were born with poor vision or have developed poor vision over time. However, at some point in time, almost everyone experiences refractory errors. There are multiple treatment options for patients to consider including glasses, contact lenses and corrective surgery, making a diagnosis far less burdensome than it may have been in the past.
Contact lenses are rapidly growing in popularity. They are, in many cases, more comfortable and easier to wear than glasses, making them the first choice for many individuals. They are much more convenient for sports. Additionally, contact lenses can treat virtually all forms of refractory errors. Cosmetic lenses are also a growing trend; some individuals order tinted prescription lenses or even non-prescription lenses to alter the appearance of their eye color.
Glasses are often made from a high-strength resin, a kind of plastic, making glasses lighter and more durable than ever before. Polycarbonate is one of the most popular materials for lenses, due to its durability, high index potential and UV filtering properties.
Modern glasses are made using high index lenses, a form of lens that is thinner and sleeker, despite the severity of a refractory error. While commonly employed in resin glasses, this technology is also available for those who choose to have glass lenses. High index lenses can be made in any shade, eliminating the need for sunglasses. Certain brands even offer glasses that change to sunglasses when in bright light and return to regular clear lenses under fluorescent or other interior lighting.
Modern science has taken great strides when it comes to glasses. Bifocals can be made invisible, even glasses for the worst refractory errors can be thin and durable, trifocals and multifocals are possible and tinted glasses allow for a stylish lens and a prescription sunglass all in one. Computer glasses are also available, allowing relief for individuals who spend long periods of time looking at a screen. Eyeglasses exist for virtually all demographics and purposes and are easy to put on and take off, making them a simple solution to turn to for vision correction.
Some procedures, such a LASIK, a procedure using a laser, are quick and painless and can permanently correct refractory errors. Despite the advantages, however, all surgery comes with risks.
LASIK can correct nearsightedness and astigmatism and some amount of farsightedness, but not all issues can be solved through surgery. Presbyopia, for example, cannot be treated with surgery. This means that patients who undergo corrective surgery to treat another condition may have to wear reading glasses later in life.
Many people have been pleased with the results of refractive surgery but it is not for everyone. Some people are ineligible based on age, physical condition and prescription. The cost of surgery can be between $1,500 and $2,500 per eye and is generally not covered in full by insurance.
The three most common kinds of refractive surgery are Radial Keratotomy (RK), Photorefractive Keratectomy (PRK) and Laser-Assisted in Situ Keratomileusis (LASIK).
Radial Keratotomy (RK)
In Radial Keratotomy, a surgeon makes several incisions in the cornea with a diamond scalpel, causing the center of the cornea to flatten. This surgical procedure is only used for treating myopia caused by an overextended cornea. RK is rarely performed today due to the increased safety and better results with laser refractive surgery.
Photorefractive Keratectomy (PRK)
In Photorefractive Keratectomy, a surgeon uses a laser to reshape the cornea. The reshaping process differs for myopia, hyperopia and astigmatism but the process is effective for all three conditions.
Laser-Assisted in Situ Keratomileusis (LASIK)
LASIK, like PRK, uses a laser to reshape the eye. However, a LASIK procedure involves creating a superficial flap of the cornea and hinging it during the procedure, allowing a surgeon access to the inner layers of the cornea. Once the necessary changes have been made with the laser, the surgeon places the flap of cornea back in place. This procedure is the newest and most precise refractive surgery procedure. LASIK is suitable for treating myopia and astigmatism and moderate degrees of hyperopia.