A simple way to describe a bifocal is to say that it has two prescriptions combined into one lens. A trifocal has three prescriptions combined into one lens; a progressive bifocal has a “continuous” number.

That old kite flyer, Benjamin Franklin, came up with the idea for the bifocal in the 18th century. He found it very bothersome to switch back and forth from his distance glasses to his reading glasses all day long. His clever solution was to cut each set of lenses into half moons (lenses were perfectly round in those days), and put them together in one frame. The top half was for his distance prescription and the bottom half his reading lenses.

No matter what form or shape modern bifocals have, they are essentially two pairs of glasses put together. As in Franklin’s case, the most common reason for bifocals is presbyopia—when the eyes can no longer easily focus at near small objects. If you wear only reading glasses distance vision is blurred and they have to be removed to see far away. If you also need glasses for distance seeing, then you are in Ben’s predicament. By placing the reading prescription in only the lower part of the lens, there is little interference with normal distance seeing.

There are many variations in design of the modern bifocal lens. The particular one chosen for you must depend on your prescription, occupation, life style, etc. The reading segment can be any size, from very small to very large; its top edge can be flat, round or oval; it can be positioned high or low in the frame. The possible combinations can run into the hundreds.

What are some of the factors in choosing a bifocal? How you use them is the main consideration. Here are two extreme examples: A symphony musician must read the music at about twenty-four inches and also occasionally glance at the conductor thirty feet away for the tempo. This person needs a bifocal with a large reading area and just a small distance portion at the top. On the other hand, a golfer wants a large distance portion with just a tiny reading spot to write on the score card. The reading position must be very low in the frame so it’s out of the line of sight when the golfer addresses the ball.

Each patient must have the bifocals designed for his or her particular use. Many times it’s impossible to design an “all purpose” bifocal for all activities. This is quite obvious when you consider that the musician could also be an avid golfer. You can’t expect to use the same bifocals for all occasions, any more than you would wear a suit of armor on the golf course.

The prescription strength of the reading portion can be made, within reason, for the distance at which you will use it. A carpenter working at arm’s length wants to see clearly at about twenty-four inches; someone working a sewing machine would prefer to see clearly at about fifteen inches. That doesn’t mean you are limited to exactly twenty-four and fifteen inches respectively. Depending on your age, there is a latitude of clear vision both closer and behind these distances.

Certain occupations require rather unusual lenses. For instance, a pharmacist has to be able to read labels on shelves well above eye level as well as normal reading material. A double bifocal, with a reading segment at the top and bottom serves this purpose. An electrician doing overhead wiring would also benefit from this arrangement.

Trifocals are three pairs of glasses in one. Why would anyone need three different prescriptions? As you get older and the eye’s focusing flexibility dwindles, you may not be able to see clearly at all distances with a bifocal. The distance prescription at the top of the lens will let you see distinctly from about four feet all the way out to the stars; the reading segment will let you see up close. This leaves an area from about twenty inches to three feet which will be fuzzy. If you need or desire clear vision at that distance, the in-between segment of the trifocal will supply it. A typical user would be a computer opera‑

Tor who would use the mid-range portion to read the characters on the video screen.

In normal bifocals or trifocals there is an abrupt change in the prescription from one section to the next. One class of lens designs gaining in popularity has a continuously changing prescription from the distance to the reading power. These are called progressive addition lenses. Theoretically, all seeing is clear if you look through the appropriate part of the lens. In practice, it takes quite a bit of adaptation because the size of the intermediate and reading zones are rather small. Also, there are distortions at the edges of these zones. Most people do adapt within about a week and are quite pleased with the results. These multifocals do away with the normally visible dividing lines and are called “invisible”. They are, therefore, more acceptable cosmetically.

When you get your first bifocals, you’ll have to develop new seeing habits combined with different patterns of head and eye movement relationships. For one thing, when walking down stairs, don’t just lower your eyes. If you do, you’ll be looking through the reading segment and the steps will be blurry. Just lower your chin to look through the upper section and the stairs will be clear. Another common problem for beginning bifocal wearers is trying to read a notice on a bulletin board. Simply raise your chin until the reading section is in position.

Most people learn to use bifocals fairly rapidly, and within a week or ten days have everything mastered. A few people just never seem to be able to get the hang of it and must revert to using two pairs of glasses with its inherent nuisance. If you are one of these people, have the optometrist re-asses your vision needs. It’s possible that you were trying to use the wrong type of bifocal for your particular needs.

Because of technical limitations, only the very center of the lens has the exact prescription your eye needs. When you look away from the center (and you do every time you move your eyes), you’re actually looking through a slightly different prescription. This difference increases towards the edge of the lens and causes shapes and sizes to be distorted. The thicker the lens, the greater the distortion; the larger the lens, the more edge distortion. (The eye is increasingly farther from the lens margin.) In low power prescriptions, the warping of objects and space is manageable and you can adjust quickly. With high powers, the adjustment can be very difficult, and large size glasses should be avoided.

Another factor influencing your sight with glasses is the curvature of the lens surfaces. It is possible to produce lenses having the same prescription power but with a variety of curvatures. A lens can be made with one flat surface, two modest curves or nearly bulging. So what? The curvatures affect the image size and shape seen through that lens. For example, a concave lens for a nearsighted person will produce a larger image if made with a deep curve. If the prescription in your two eyes is quite different, it is no easy matter to select matching curvatures.

Has it ever happened to you that two supposedly identical pairs of glasses don’t feel the same? It could be that they were made with lenses of dissimilar curvatures.

If you are nearsighted and put glasses on for the first time, the world will look clearer but smaller. Since the brain uses size as one judgment of distances (small objects are assumed to be farther away), you will tend to think you are more remote from things than you really are. You may spill a cup of coffee when you reach for it because it’s closer than you visualize.

If you are farsighted, the opposite will happen. Objects will appear clearer but larger. So, you will judge things to be closer and when you reach for a doorknob you may come up short. Over the span of a few days, the brain will recalculate object/ distance relationships and you will regain your familiar distance judgement.

These annoyances are minor compared to the first-time correction for astigmatism. Objects will be tilted and curved; your entire perspective will be in shambles. (You’ll appreciate what fictional Alice experienced.) Be courageous—as confusing as things may be, they will slowly reassemble into a “normal” looking world within a few days.

Scientific and technical advancements in lens materials now makes it possible to produce thin, lightweight lenses out of high- index resins. The higher the index of refraction of a lens material, the more prescription power can be squeezed into a given area. The result is a dramatic, cosmetic improvement in the way the finished glasses look. However, because the prescription power is intensified, moving the eyes off the lens center will cause a quicker change in effective strength. It will take a little longer to adapt to glasses with these materials, but it’s well worth it.

A seemingly minor matter such as the distance between the lens and your eye will effect the power and image size. If you are farsighted and the glasses slip down your nose, the effective power and image size are increased. If you are nearsighted and wear your glasses at the end of your nose, the effective power is reduced. The exact amount will vary with the length of your nose and the prescription.

All the annoying symptoms are aggravated proportionally with high power prescriptions. The very nearsighted person also has to contend with unsightly, thick, light-reflecting edges on the lenses. While these can be reduced with the high-index lenses, a further improvement can be made by “rolling” the edges and tinting the lens. A better way is to choose a smaller frame because the edge thickness increases sharply with increased lens size.

A very farsighted person need not be concerned with a thick edge, but the eyes exhibit an enlarged “bug-eyed” look from the bulky center thickness. This can largely be overcome with special high-index materials which are designed with unique curvatures to flatten the center bulge. Of course, the adaptation time will be longer.

Some people are bothered by reflections from the surfaces of the lenses, especially at night. You should have little trouble learning to ignore them, but if desired, the reflections can be mostly eliminated with a multilayered, anti-reflective coating on the surfaces.

To get the best vision, the centers of the lenses must be positioned directly in front of your pupils. Rarely does the frame size exactly match this position. Therefore, the lenses must be offset to compensate for the actual eye placement. If this is not done, it can disturb your eye movements and focusing.

For all these reasons, it should be apparent that the making of glasses must not be a haphazard procedure. The measuring, fitting and aligning of the glasses has to be done accurately and knowledgeably. For your own good, the optometrist should oversee the entire process.

Actually, by itself, a very wide field of view is not all that beneficial. While it’s good for noticing movement and general shapes, it’s very poor for seeing details. (Try threading a needle out of the “corner” of your eye.) Seeing movement is adequate for a frog since it merely triggers a reflex action to catch a fly, but for us it’s important to know what caused that movement. Is it a charging rhinoceros or only the shadow of a bird? To make this vital decision we must see it in detail. Why can’t we see in detail over the entire field of view? Very simply, the limited size of the brain.

The retina’s area of detailed sight is the macula which is about 1/20th of an inch in diameter. The flood of nerve signals from this tiny area alone keeps a large part of the brain occupied with interpreting the visual meaning. (The visual cortex allocates about 35 times as much space to the fovea as the rest of the retina.) If the entire retina had the sight property of the macula, the eye would have to be much bigger and the brain logarithmically larger (room-size). It’s doubtful if you could even “attend” to so much information.

Our vision is actually an adroit compromise. To the sides we have a reasonable field of view without much detail; at the macula we have a very limited view with marvelous detail.

It would be possible, though, to have this arrangement with just one eye bulging out of the center of the forehead. That’s impractical because the eye would be very susceptible to injury. So the eye is placed within a bony vault for maximum protection. If you put your mind to it, you could come up with several alternate placements for the eyes—fore and aft, for instance. But there is a very distinctive advantage to frontally placed eyes with overlapping fields of view—depth perception.

Before you say, “Is that all?,” remember that nature thinks so much of stereoscopic vision that a very elaborate system is involved to produce it. The retina is divided almost exactly down the middle with the nerve fibers from the outer half of each eye connecting to the same side of the brain; the nerve fibers from the nasal side cross over and connect on the opposite sides of the brain. This seems like a curious arrangement, but it’s not the crossing that’s curious (your left hand is controlled by the right side of the brain). The nerve fibers which don’t cross are part of the secret of depth perception.

Because the eyes are about two and one-half inches apart, each retina receives a slightly different image. You can easily prove this if you hold your finger 8 inches in front of your nose and alternately close each eye. The position of the finger will seem to shift back and forth. Within the brain there are special cells which match the offset images from the two eyes to yield the sense of solid depth.

• A diagramatic view, looking down at a cross-section of the eyes and brain, showing how the nerve fibers cross over.
• The nerve fibers from the two right halves of the retina end up on the right side of the brain; the left halves end up on the left side.
• The two half-images are “welded” into one by the brain. We do not normally see the half images as shown in the drawing.
• However, in certain cases of brain injury or disease,it is possible that only half the field of view will be seen.

Stereopsis. By crossing or uncorssing your eyes you can fuse these two images into a single solid pyramid with depth. To cross your eyes, make believe you’re staring at a spot. To uncross your eyes, look at a spot between the two images and make believe you’re looking far away. When crossing the eyes, the pyramid will appear smaller and the point of the base will be further away.

There are other ways to see depth which can be achieved with only one eye: perspective, size, surface texture, shadows, etc. which are all employed to depict a sense of three-dimension in pictures. But it is simply not quite the same as true stereopsis.

Is stereopsis all that important for survival? It’s difficult to reconstruct exactly how much advantage it conferred on our ancestors. Certainly, grasping and picking up objects is much simpler with 3-D. Whatever the reason, nature labored long and hard to perfect it, so let’s enjoy it.

As with any system, the more complicated, the more potential there is for errors. To appreciate the full value of depth perception (and for it to develop), very precise and intricate alignment of the eyes is essential. Horizontally, the alignment must be within a few degrees of arc; vertically, much less. If the six muscles controlling each eye cannot point the two eyes at the same spot within this narrow range, the stereoscopic effect will be diminished or lost. The very narrow range of vertical alignment explains why people who develop a condition wherein one eye sights slightly higher than the other, will often see double.

Basically, what is a lens? It doesn’t have to be made out of glass or plastic to do its job. The only requirement is that it be transparent and capable of bending—refracting—light rays in 1 predetermined way. You could, if you put your mind to it, make a lens out of ice or gelatin and fulfill the basic requirement. It would make an interesting science fair project, but pretty strange glasses. No, we need something more durable.

Whether glass or plastic is used, it must be manufactured totally free of tiny air bubbles, striations, and distortions; it requires very exacting techniques. There are plenty of rejects and “seconds” in lenses which, unfortunately, find their way to unscrupulous operators and so-called “bargain” houses.

The lens power is measured in units called diopters which are based on the extent to which the light rays passing through the lens will be bent. As the power of the lens increases, so does the thickness. Three types of lenses are commonly used to correct vision problems—convex, concave, and cylindrical.

The convex lens is thicker in the center that at the edges, and gathers light rays together towards a point. Remember when you were a kid and used a magnifying lens to focus the sun’s rays on a piece of paper in order to start it burning? That was a convex lens. It is used in glasses for the farsighted eye which cannot bend the light rays as mush as they should. If the eye is 2 diopters farsighted, a 2 diopter convex lens will compensate for it. It is also commonly used in reading glasses.

The concave lens is thinner at the center than at the edges, and spreads light rays apart. You could not use this lens to focus the sun’s rays, because it never forms a real image anywhere. (The explanation involves physics—just take our word for it.) By putting this lens in front of the nearsighted eye, we can reduce the overall power to put the image neatly on the retina. A 1 diopter concave lens will correct 1 diopter of nearsightedness.

The cylindrical lens is shaped like a section of an auto tire, curved more in one direction than the other. It’s very difficult to ascertain the direction of the curve by simply looking at your glasses. Sometimes you can recognize it this way: Hold the glasses about twenty inches in front of you and sight a straight line or edge through the lens. Slowly rotate the glasses clockwise and then counterclockwise. If the line tilts with or against the rotation of the glasses, it’s a cylindrical lens and you have astigmatism. This type of lens must be carefully aligned in front of the eyes with an exact up and down orientation. Most often a cylindrical lens will be part of the prescription with a convex or concave lens.

Would you like to learn how to read a prescription for eyeglasses? A convex lens (for the farsighted eye) is written with a plus (+) symbol. A concave lens (for the nearsighted eye) is written with a minus (-) sign. If the prescription calls for a +2.00, it’s a 2 diopter lens for a farsighted eye, or it could be a 2 diopter reading lens for a presbyopic eye. A -2.50 is a 2 1/2 diopter lens for a nearsighted eye. The higher the number the stronger the lens.

For an eye with astigmatism, the prescription might look like this:

-2.50 -1.00 axis 45

This is 2 1/2 diopters of nearsightedness with 1 diopter of astigmatism. The axis indicates the orientation of the cylindrical part of the lens. It’s based on the degrees of a protractor- 180 is the horizontal, 90 the vertical meridians. The axis can be anywhere from 1 to 180.

A bifocal prescription will have additional numbers to indicate the strength of the reading part of the lens.

+1.75 -0.25 axis 95 add +1.50

This is 1 3/4 diopters of farsightedness with 1/4 diopter of astigmatism and an additional 1 1/2 diopters of power for reading.

Sometimes a prism effect has to be incorporated into the prescription to deviate the light rays in a desired way.

-3.25 -0.75 axis 70 2^A IN

The little triangular figure designates a prism and in this case the direction of the base is inward, though it could be out, up or down.

You need one more piece of information in order to read your RX—knowing which numbers are for which eye. The right eye is designated O.D. for the Latin oculus dexter; the left eye is O.S. for oculus sinister. O.U. is oculus uterque, both eyes.

You may still not be thrilled about having to wear glasses, but at least you now know what you’re wearing.

Color vision is routinely screened during the regular examination to detect any gross color deficiencies. For occupations requiring an excellent “color sense” such as printer, art director, stage-scenery designer, cloth dyer, etc., or for the detection of an early stage of a disease, more extensive color tests are administered. One such test requires arranging a series of round, colored discs in the correct sequence of hues. The most sophisticated color test, the anomaloscope, used mostly in research, challenges the person to mix primary green and red light sources together to match a standard yellow light.

Electrodiagnostic Tests

Very sensitive instruments can detect and measure the electrical nerve impulses which are generated in the eye and travel through the optic nerve to the brain. Similar in operation to an electrocardiogram, an electroretinogram (ERG) can provide practical information about the functioning of the retina in patients with acquired or inherited retinal disorders.

The more comprehensive visual evoked response (VER) test will measure the electrical activity along the visual pathway all the way to the visual cortex of the brain. Electrodes are attached to specific spots on the head, but there is no discomfort. The VER makes it possible to differentiate the vision in each eye, assess the potential visual acuity, and detect amblyopia objectively. It can be extremely useful with young children or retarded adults whose subjective responses could be unreliable or difficult to obtain.

Ultrasonography, Echography

When the inside of the eye cannot be clearly viewed because of a hemorrhage, cloudy fluid or a cataract, ultrasonography is employed to “see” what’s inside. The technique generates sound waves and measures the returning echoes to harmlessly probe the eye and surrounding tissue for fractures, tumors, detachments, foreign bodies, etc. A very common use for ultrasonography is to measure the size and location of the eye’s structures prior to cataract surgery to calculate the needed power of the lens to be implanted.

Fluorescein Angiography

This is an invasive test to assess the blood circulation in the retina and choroid at the back of the eye, or to verify the presence of a tumor. Fluorescein, a dye which glows in ultraviolet light, is injected into a vein and quickly circulates into the retinal vessels. Photographs taken every few seconds through a cobalt blue filter can pinpoint leaking, obstructed and/or new blood vessels. Because of a small but serious health-risk factor from the injected fluorescein, this procedure is used if the information cannot be gained in any other manner.

Gonioscopy

A gonioscope is essentially a contact lens fitted with tiny mirrors to view the angle opening between the cornea and iris inside the eye. The information gained can differentiate between open or closed angle glaucoma; inspect for tumors and lesions; recognize injury induced tears; evaluate effectiveness of laser treatments.

Interferometry

When a dense cataract is present, it is very important to estimate what degree of vision will be available after the cataract is removed. Since the view and inspection of the back of the eye is blocked by the cataract, the doctor may be unaware that retinal disease may also be present. If there is, removing the cataract will leave the person disappointed in the scantiness of sight improvement.

The interferometer focuses an intense, coherent source of regular or laser light into the eye to establish an approximate idea of the reclaimable vision. The instrument is also practical for predicting the eventual sight attainable after treatment for amblyopia.

Glare Tester

Cataracts or other opacities in the eye will often cause increased sensitivity to glare because they scatter the incoming light. If the glare source is bright enough it will functionally reduce your sight. For instance, a person may see 20/30 in normal illumination, but barely see 20/200 in very bright light.

A glare testing instrument can document the levels of glare which creates a disability, and can help determine if tints applied to the glasses can be beneficial in minimizing the effects. Another use for the instrument is to measure the time it takes to recover sight after the retina is dazzled with very bright light. This mimics entering a darkened area after exposure to sunlight, or being “blinded” by oncoming headlights in night driving. While the glare-recovery time normally increases with age, very slow recovery can also be caused by disease or vitamin deficiency.

Radiology, CT-Scan, MRI

Suspected fractures of any of the bones making up the eye socket will require X-ray pictures to identify the breaks. For complicated fractures with muscle entrapment, to localize foreign bodies, and investigate for suspected tumors, Computed Tomography (CT-SCAN) makes diagnosis easier. Magnetic Resonance Imaging (MRI) is more useful to differentiate between diseases of soft tissues, though it should not be employed when a metallic foreign body is present.

Cell Counts

The inner layer of the cornea, the endothelium, plays a crucial role in maintaining the transparency and health of the cornea. Unlike the surface epithelial layer, the endothelium doesn’t grow new cells to replace damaged ones. The remaining cells enlarge to fill in the spaces. (Long term contact lens wear seems to be implicated with changes in the cell shapes.)

Before cataract removal or corneal surgery, an instrument is often used to estimate the number and determine the condition of the cells. Since many are lost during surgery, the information helps assess the risk and success of the surgical procedure.

Pachometry

There are instances when it is important to know the thickness of the cornea and the depth of the anterior chamber of the eye. The pachometer, an instrument attached onto the biomicroscope (slit lamp) will accomplish this. A very useful application is to measure corneal swelling or thickening after contact lenses are worn for an extended time.

Ophthalmodynamometer

An instrument designed specifically to measure the systolic and diastolic blood pressure of arterioretinal vessels. It will often detect increasing intracranial pressure before other symptoms appear. (This instrument is giving way to more sophisticated methods.)

A field of vision testing instrument. The patient fixates a central target with one eye and responds to flashing and/or moving spots of light. An internal computer will analyze and provide a printed copy of the field of view.

If you lose either the central vision or the peripheral vision, you can be considered legally blind. You would suppose that having nice, clear central sight would be adequate, but it just isn’t by itself. Why not? Roll two sheets of paper into small tubes, hold them up against your eyes and look through them. You can definitely watch TV and reading can be mastered, but try walking around in unfamiliar surroundings or descending a flight of stairs. Driving an automobile with any degree of safety would be impossible. Conversely, if your central sight is lost, you can walk around, but you would not be able to read or easily recognize people’s faces.

There are many diseases which can decimate either the central or peripheral vision. Glaucoma is the classical example of one that gradually shrinks the peripheral vision until, in the final stage, only the narrow central sight remains.

Rather than the entire peripheral view being lost, it’s more likely that a section or portion is missing. Usually, you won’t even be aware of it because the blank area is filled in by the sight of the other eye. However, if the loss is to the outside or downward, and cannot be filled in, you may find yourself bumping into objects. These sector field losses can be caused by aneurisms, hemorrhages, tumors, etc.

The testing is generally done with computerized instruments which flash tiny spots of light against a blank background. The location, size and density of the missing area is plotted and recorded for analysis.

Amsler Grid

As the name implies, a grid of fine lines is used to detect subtle changes and distortions in the perceived view. While staring, with one eye at a time, at the central fixation dot, some portion of the lines may be seen to be missing or not perfectly straight. Retinal swelling, hemorrhages and certain diseases are the cause. Often, a patient will be given an Amsler grid to keep at home to monitor changes.

Contrast Sensitivity

The ability to see an object in dim light or to detect an object against a background of almost similar shading, depends on a person’s sensitivity to discern small differences in contrast.

The visual system has several subsystems (channels) each best tuned in to a particular level of contrast. The normal visual acuity test (20/40, 20/20, etc.) uses high contrast letters and is relatively insensitive for revealing any problems with the lower contrast channels. It’s of interest because, after all, most of our general seeing is not concerned with reading black letters on a white background at 20 feet.

There are normal variations among individuals, but aging, eye diseases, diseases affecting the visual system, amblyopia and the use of certain medications can have negative consequences.

Your contrast sensitivity can be screened with a test that takes only a few minutes. The test is also useful in predicting improvement with a prescription change or a tinted lens, and it can alert the doctor to avoid a change or tint which could worsen the problem.

Extensive Color Testing

Color vision is routinely screened during the regular examination to detect any gross color deficiencies. For occupations requiring an excellent “color sense” such as printer, art director, stage-scenery designer, cloth dyer, etc., or for the detection of an early stage of a disease, more extensive color tests are administered. One such test requires arranging a series of round, colored discs in the correct sequence of hues. The most sophisticated color test, the anomaloscope, used mostly in research, challenges the person to mix primary green and red light sources together to match a standard yellow light.

Electrodiagnostic Tests

Very sensitive instruments can detect and measure the electrical nerve impulses which are generated in the eye and travel through the optic nerve to the brain. Similar in operation to an electrocardiogram, an electroretinogram (ERG) can provide practical information about the functioning of the retina in patients with acquired or inherited retinal disorders.

The more comprehensive visual evoked response (VER) test will measure the electrical activity along the visual pathway all the way to the visual cortex of the brain. Electrodes are attached to specific spots on the head, but there is no discomfort. The VER makes it possible to differentiate the vision in each eye, assess the potential visual acuity, and detect amblyopia objectively. It can be extremely useful with young children or retarded adults whose subjective responses could be unreliable or difficult to obtain.

Loss of Corneal Sensitivity

The next time you get a piece of dust in your eye don’t complain about the pain and buckets of tears. Be thankful that your system is working as it should. The pain, of course, is a warning that something is damaging the cornea; the profuse tearing is an attempt to wash the offending object away.

In some rare instances, the cornea may lose its sensitivity. If you can’t feel foreign matter rubbing the cornea, serious eye damage can result. It’s quite easy to test for sensitivity with an instrument or a thin wisp of cotton. Total lack of sensitivity indicates a serious neurological problem. This should not be confused with the gradual diminishing sensitivity of aging.

Bulging or Protruding Eyes

We are not referring to people with naturally large eyes such as very nearsighted individuals, but when one or both eyes give the appearance of becoming larger. It doesn’t really mean that the eyes are getting bigger, but rather that they have started to protrude. If both eyes become more prominent,”frog-eyed” look—chances are an overactive thyroid is responsible. When only one eye protrudes, the chief causes are hemorrhages, inflammation, or tumors which must be quickly dealt with. Often the protrusions are tenuous, and instruments must be used to carefully compare the two eyes.

Double Vision

If you have ever experienced double vision when you are tired, after taking medication, or after drinking too much alcohol, you know how very disturbing it can be. Sudden double vision without any apparent cause is very frightening. No matter what the reason, it attests that the two eyes are not pointing at the same spot.

In the case of fatigue or drugs (including alcohol), there is a temporary interruption with the brain’s ability to control and coordinate the eye muscles. Getting sufficient rest or eliminating the offending chemical is usually all that’s needed.

A more serious matter is double vision which occurs abruptly and is present all the time. The typical culprit is a small stroke or hemorrhage; less likely is a brain tumor. In most instances, proper treatment of the underlying cause may slowly restore single vision. As a temporary measure, special prism glasses can keep the double vision under control.

If you have a choice, pick someone with more experience.

How long has the doctor been in that practice/office?

The optometrist might have graduated 25 years ago, but has shifted around every few years. A warning flag.

How much is the general examination fee?

The answer should be a range depending on specific tests you might need.

Does the doctor regularly attend continuing education classes?

Self evident.

Is the doctor a member of the Academy of Optometry?

A good sign of competency.

Does the doctor lecture and/or write on optometric topics?

Obviously, not everyone can be a lecturer or needs to be a lecturer, but you can decide.

Will the doctor examine an 18-month old toddler?

That’s a bit of a trick question, especially if you don’t have an 18-month old. However, the answer is very revealing because it indicates the doctor’s level of expertise and willingness to spend time with you.

Vision acuity usually declines at a gradual enough rate, so unless you pay close attention or measure it you are seldom aware of the change until it interferes with your daily activities. If you wear the same glasses constantly you will probably find that you don’t know much about the natural capabilities of your eyes. How far away can you recognize someone? Can you thread a needle without your glasses on? What special distortions do you create? Is your vision just blurry or do you see additional lines that aren’t there?

Muscles of the body are remarkably adaptable, but they maintain only the amount of mass and strength you need to meet daily physical demands. Fortunately, for most people, good sight requires nothing more than maintaining the muscle balance and coordination we were born with. Daily habits of how we use our eyes may make unclear sight due to irregular muscle form seem permanent, but because muscles are adaptable, when we begin changing our activities, our muscles will change too. Be sure you consciously challenge those old habits and give your eyes practice every day in seeing something that is now slightly out of focus just that little bit more clearly.

It was not until I started to improve my eyesight that I started to analyse the subtleties of the gestures of seeing. In my research I read about a connection between posture and eyesight that suggests that poor eyesight might cause or affect poor posture or vice versa. I feel that eyesight and posture develop together as a result of our activities and how we are using our muscles. They are both an expression of the gesture of seeing. Perhaps this way of explaining it can help us see how to reverse the condition by creating the opposite action.

The two basic ways to see include distance focus and close focus. In walking and athletic activity, the head is usually upright, the shoulders and back are straight, the chest is expanded to breathe deeply, our eyes are pointed straight ahead and the ciliary muscle is relaxed for distance focus. We have good peripheral vision. For close work, the head is usually positioned forward and down, the shoulders are rounded slightly to extend the arms, the muscles of the eyes contract to focus close and point the eyes inward. We are narrowing our peripheral vision.

Moving from one posture to another can naturally trigger the eye to change focus; however, a person with poor eyesight may have lost touch with his ability to change focus effectively and might try to incorporate the opposite gesture. To see into the distance, a short-sighted person may push his head forward and squint, often in a futile attempt to bring things close enough to focus on clearly. A more effective gesture is to pull the head upright and open the eyes wide. This should help to trigger the ciliary muscle to relax and the lateral recti muscles to pull the eyes outward to improve peripheral vision. People who are a little far-sighted or have presbyopia, faced with reading a menu, for example, often pull their head back and lengthen their arm in order to focus better. They may be attempting to create a distance focus. A gesture of bringing the head forward and down and focusing the eyes towards the end of the nose might be more effective in triggering the oblique and ciliary muscles.

Start practising going from one posture to another. At first, you may want to exaggerate them so that you can experience how different they feel. As you learn how to increase the flexibility of the eye patterns, you may also notice that you can reverse the intensity of frown lines, crowsfeet and sagging eyelids.