Dispensing II Lecture
Very often in the course of an optician’s career, he or she is forced to deal with ignorance. The common person is not a specialist in optics, and commonly believes what rumors or old wives’ tales he hears. Not only does this annoy opticians, it also makes it much harder to help patients make informed decisions. People need to know the truth about their eyes and how to care for them. It is our duty to be educators as well as opticians. This quite often entails upending their mistakenly held notions. This is best done with a respectful tone and a gentle, conversational manner.
Nearly the most common misconception people tend to have about vision is also by far the most frustrating. “I don’t want to wear my glasses all the time because it’ll make my prescription get worse faster,” or something to that effect, is a sentiment echoed in dispensaries all over. There is an idea out there that wearing corrective eyewear weakens the eyes.
Where do people get these ideas? The scientific community is partly to blame. People tend to trust men in white coats, and this was the case when William Horatio Bates published The Cure of Imperfect Eyesight by Treatment Without Glasses in 1920. The early 20th century saw the twilight years of the age of pseudo-science. For example, these were the same years that saw the popularity of phrenology, the belief that personality, intelligence, and various other characteristics of a person could be divined through careful studying of the shape and contours of the head. Bates taught that ametropia was the result not of imperfections in the refractive tissues or in the shape or size of the eye. Instead, poor eyesight was due to imbalances in the intraocular and extraocular muscles. In effect, vision problems were blamed on stress and tension, and could be treated through exercises to relax the muscles and strengthen the eye. He claimed that such exercises could cure myopia, hyperopia, astigmatism, presbyopia, even cataracts and other diseases. Bates denounced the use of spectacles, saying that by helping one to focus, they caused the eyes to deteriorate. (Bates, 1920).
Although quickly dismissed by the eye care profession at large, Bates’ ideas caught on with some, and supporters of the “Bates Method” began publishing books and selling training kits to the public. One can still find books promising to improve vision through exercises and therapy, including one that dismisses Bates’ method in favor of the author’s own. (Kavner, 1978). Typically, such quacks sell expensive gadgets to go with the exercises, such as pinhole occluders ($40), and trampolines ($249.95). (Goodrich, 1999). Unfortunately for eye care professionals, there is a sizable contingent of believers who refuse to accept the mainstream theories of modern science.
The widely denounced writings of a long dead quack physician can only explain this phenomenon so far. There must be a deeper cause for the resistance that scrupulous opticians and doctors meet when trying to put patients into up to date prescriptions. Why would people still think that glasses make the eyes get worse, even when Bates has been so long discredited? The problem lies in the unscientific observations of day-to-day life. It is true that people trust men in white coats, but they trust their own senses far more readily. To the untrained mind, the facts speak for themselves. Those who wear glasses typically see their prescriptions increase over time. Myopes who start wearing glasses very young tend to reach much higher minus prescriptions than those who start later. It certainly seems that wearing glasses makes vision deteriorate, as Bates claimed.
It is simply not the case, however, that helping the eye see weakens its ability to function. All of our evidence points to the contrary. Refractive errors are caused by physical shortcomings in the structure of the eye. An emmetropic eye is one in which parallel rays of light are refracted by the cornea, crystalline lens, and to a lesser extent the aqueous and vitreous humors, to form a point focus on the retina. Myopia and hyperopia are divided each into two categories: axial and refractive. Axial myopia describes an eye where the globe is simply too long, causing light to focus prematurely. Refractive myopia describes the refractive tissues of the eye causing too much convergence, to the same effect. Axial and refractive hyperopia work in the same way, except that they cause too little convergence, causing light rays to meet the retina before coming to a focus. Astigmatism describes light focusing unevenly in a line focus due to a cylindrical cornea, lens, or both. Presbyopia is the gradual loss of accommodation for near vision due to thickening of the crystalline lens with age. (Koretz, 1988).
None of these are related to muscles except presbyopia. Even presbyopia can’t be treated with exercises because the problem is due to physical changes in the lens itself much more so than the ciliary muscle responsible for accommodation. (Moses, 1987). The other refractive errors are all due to imperfections in non-muscular tissues. These seem to be inherited, rather than caused by environment or behavior.
When assailing the preconceived notions of others, it is important to avoid sounding overly confrontational. Also important is to refrain from overloading the patient with technical jargon. Nothing produces opposition more than making someone feel stupid. Opticians should gently but confidently assert that refractive error and changes in vision are natural, biological occurrences, and are not cause for worry (barring severe power shifts or other warning signs).
The list of purported ways to make the eyes worse is long, ranging from the silly to the strange to the somewhat true. Your mother may have told you that reading in the dark would make you go blind or ruin your eyes, and though you were right to do what she told you to do, she might not have always been right. Research in the area has been limited, but it seems that light levels have no correlation to changes in one’s prescription. (Guggenheim 2003). The same is true of sitting too close to the television, rubbing your eyes while you have a fever, masturbating, and the myriad other things you were told would in some way harm your eyes. Just in case you’re wondering, no, if you cross your eyes, they won’t stick that way, though you will eventually get a headache. Short of injury, there isn’t much a person can do to harm his or her vision.
Likewise, motherly advice suggests that eating carrots will improve one’s eyesight. Although nutrition does affect vision, it is more accurate to say that malnutrition adversely affects how you see. Proper nutrients, especially vitamin A, allow the eye to sustain itself and function properly. They do not produce emmetropia. Without such nutrients, however, severe consequences are the result. For example, vitamin A deficiency is the leading cause of blindness worldwide. In the poorer regions of the world, vitamin A deficiency has been found to cause xeropthlamia (thickening and dryness of the conjunctiva), corneal xerosis (dryness of the cornea), night blindness, and keratomalacia (corneal softening and scarring). (Witten, 2004). In this sense, Mom was right, as carrots are a good source of vitamin A. Unfortunately, this doesn’t affect the need for glasses or contacts.
The myths in which many believe are not limited to their eyes. Preconceived notions about eyewear frequently prove the bane of an optician’s existence. It is our job to provide people with frame and lens products to meet their optical needs to the greatest extent possible. That is why it is so frustrating to hear so much misinformation spewing from the mouths of our patients.
Many think that they need the lenses in their glasses to be much larger than they really do. They think larger lenses will gain them increased peripheral vision. Spectacle wearers already reduce their peripheral vision by limiting themselves to the world seen inside their frames. It stands to reason that larger lenses should equal a wider field of view. The problems with this idea are those inherent in any refractive lens.
All lenses have certain aberrations, including chromatic aberration, marginal astigmatism, curvature of field, distortion, coma, and spherical aberration. Coma and spherical aberration are of no real concern in ophthalmic lenses due to the small aperture of the pupil. Chromatic aberration is divided into longitudinal (axial) and lateral chromatic aberration. Axial chromatism describes the dispersion of white light into its constituent wavelengths along the visual axis. Lateral chromatic aberration refers to the resulting discrepancy in image sizes in the various wavelengths as white light is dispersed through a prism, such as when looking in the periphery. Both are present in all lenses, but are more prevalent in lenses with low Abbe values, such as polycarbonate. Marginal astigmatism is the failure of oblique light rays to form a point focus, instead acting like they are passing through a lens with increased cylinder power. Curvature of field, also known as power error, causes lens power to be different on the periphery than at the optical center. Distortion results from variance of magnification at the periphery from the optical center. It manifests itself in pincushion distortion with plus lenses, when the edges of an object appear to curve inward, and barrel distortion with minus lenses, when the edges of an object appear to curve outward. (Brooks, 1996)
Using manufacturers’ recommended base curves for the lenses could reduce marginal astigmatism and curvature of field. Many of these problems are only present in the periphery, and larger lenses do nothing if not increase peripheral lens area. (Brooks, 1996). This means that smaller lens sizes decrease aberrations and thus, improve vision.
This is also true in regards to progressive addition lenses. One of the most common complaints patients have when first wearing progressives is the loss of peripheral vision. A byproduct of the progressive channel is the loss of clear vision on the edges of the lens, particularly in the lower areas. Wider lenses don’t widen the channel; they merely widen the parts of the lens filled with unwanted astigmatism. (Brooks, 1996) Contrary to patient’s wishes, they will actually perceive more distortion with wider lenses than with smaller ones. Helping patients choose frames that fit properly will prevent dissatisfaction with lens performance and, ultimately, non-adapts.
In this case, the best way to express issues of size is with visual aids whenever possible. Patients certainly don’t need to hear the complex optical explanations attached, but general descriptions and a quick demonstration will win over most. For those that insist on ordering larger lenses, recommend aspheric lenses. Aspheric lenses have a gradually flattening objective surface, reducing thickness and increasing peripheral vision. This limits many of the aberrations noticeable in larger lens sizes. (Brooks, 1996).
To an extent, this misconception actually does ring true with sunglasses. Sunglass lenses need to cover the eyes in order to provide adequate protection. Ultraviolet rays coming in peripherally can still cause cataracts, though typically on the peripheral areas of the crystalline lens. If the sunglass lenses are oversized, however, increased reflections on the backside of the lenses can result. Although this can be treated with an anti-reflective coating, it can more effectively and less expensively treated by choosing properly fitting sunglasses. (Brooks, 1996).
Partially as a result of a successful decades-long advertising campaign, the general public is aware of photochromic lenses. Developed in 1964 by Corning, photochromics are now available in a number of colors, materials, indices, and lens types. (www.corning.com, 2005). Such lenses can be used by opticians to generate a good deal of profits. Unfortunately for dispensers, many patients are under the false impression that photochromics replace sunglasses. It is simply not true that one pair of glasses with photochromic lenses can serve all needs in all light conditions.
Why do they think this? Advertisements by Corning and Transitions imply that their lenses act like sunglasses with claims that they get “as dark as a sunglass in bright, glaring sunlight.” (www.transitions.com, 2004). While no explicit claim is made that they function in exactly the same way, and under exactly the same circumstances, as sunglasses, the uneducated public is left with no reason to conclude otherwise.
Although the latest generations of photochromics can now approach light transmission levels similar to a standard sunglass (around 15%), there are still drawbacks to choosing photochromics over separate sun and dress pairs. First and most obviously, photochromics don’t work well while driving. Photochromics, whether made with in-mass, imbibition, or photochromic coatings, depend on exposure to UV to get dark. Automobile windshields prevent UV transmission, leaving very little UV to reach the lenses from ambient light through the side windows. A better suggestion to our patients would be a polarized sunglass for bright daytime driving. Another problem with photochromics is that they retain some tint even when not exposed to ultraviolet light. As a result, the lenses limit light transmission indoors or at night. It has been demonstrated that night drivers have substantially lower visual acuity than the do in daylight. Cutting their light transmission further only limits that already compromised visual acuity, making night driving slightly more dangerous for our patients and other drivers. If this were not enough, photochromics in all forms of plastic do not age well. With the exception of glass lenses, photochromics lose the ability to darken and to clear after a period of about two years. Add to this the fact that all photochromics function better in cold temperatures than in the heat, and the idea of using photochromics to replace sunglasses loses its allure. (Thomas, 2005).
Once again, a simple explanation and visual aids will get the point across without turning the patient off. Also important in this instance is to make alternate suggestions for sun protection, such as a separate pair of sunglasses or a clip-on sunglass. Once they understand that photochromics’ function is not to replace sunglasses, patients tend to choose more appropriate options like separate dress and sunglass pairs. This helps patients meet their optical needs, and it helps opticians maintain a profitable business.
Psychology is an important aspect of the practice of ophthalmic dispensing. We know about optics, we know about optical products, and we know how to use our knowledge to help patients. The real trick to being a successful optician is convincing patients to do what is best for them. This very often means correcting their misconceptions with education. Care must be taken not to appear confrontational, but instead we must come across as people trying to help. Properly provided with knowledge, patients will make intelligent decisions. We must ensure that they have this knowledge. That is our job as opticians every bit as much as interpreting prescriptions and fitting and dispensing eyewear.
Bates, William Horatio. (1920). The cure of imperfect eyesight by treatment without glasses. New York, NY: Central Fixation Publishing Company.
Brooks, Clifford W., and Borish, Irvin, M. (1996). System for ophthalmic dispensing, second edition. Boston, MA: Butterworth-Heinemann.
Corning Incorporated. (2005). Corning Ophthalmic Product Information. Retrieved April 12, 2005 from http://www.corning.com/ophthalmic
Goodrich, Janet. (1999). Help your child to perfect eyesight without glasses. Berkeley, CA: Celestial Arts.
Guggenheim, J. A., Hill, C, and Yam, T. F. (2003). Myopia, genetics, and ambient lighting at night in a UK sample. British Journal of Ophthalmology, 87(5), 580-582.
Kavner, Richard S., and Dusky, Lorraine. (1978). Total vision. New York, NY: A&W Publishers, Inc.
Koretz, Jane F., and Handelman, George H. (1988). How the eye focuses. Scientific American, July 1988.
Moses, Robert A., and Hart, William M., Jr. (1987). Adler’s physiology of the eye. St. Louis, MO: C.V. Mosby and Company.
Thomas, Brian. (2005). Internship in Ophthalmic Science. Course # OPTH-300-51, Raritan Valley Community College, North Branch, NJ.
Transitions Optical. (2004). Transitions Homepage. Retrieved April 11, 2005, from http://www.transitions.com