Ординатура / Офтальмология / Английские материалы / Relearning To See_Quackenbush_2000

strong electric light... is substituted ...

allowing it to shine on his closed eyelids as

in the sun....

In Better Eyesight magazine, July 1927, Mr. Ian Jardine, a Natural Vision teacher, tells of his own introduction to closed-eyelid sunning:

.. .Then I was shown how to sun my eyes by letting the rays of the sun fall on the closed eyelids, while moving the head gently from side to side. This seemed a strange thing to do, as previously I had worn blue glasses to shield the eyes from strong light.

CLOSED-EYELID SUNNING

Closed-eyelid sunning is a natural, healthy activity. Animals "sun" naturally. Sunning is not an "exercise"; it is a self-healing activity. Remember to keep the eyelids closed while sunning.

* £ TO S U N :

Sit in a comfortable chair facing the sun. A reclining chair is especially relaxing. Close your eyelids. Depending upon the relationship of your head to the sun, tilt your head slightly toward the sun. Then, swing your

nose-feather gently to the right, then to the left, then to the right, and continue alternating back and forth slowly across the sun.

Even though the eyelids are closed, notice how the sun appears to move in the opposite direction of your head movement.

The infinity sign/figure-8 shape is an excellent pattern while sunning. Remember to move the nose-feather up through the center and down on the outsides of the loops, ie., counterclockwise on the left and clockwise on the right.

Even a few minutes of sunning can be very beneficial. Do not sun for so long a period that you get a sunburn. Five to ten minutes at a time is fine for most people If at first the light is too bright, you can sun while sitting under a shady tree.

If the sun is not available, you can "sun" indoors by using a regular 100-watt light bulb. Of course, the sun is always the best.

Another wonderful way to sun is to do the Long Swing at sunrise or sunset. Remember to keep the eyelids closed while sunning.

TOM'S PERSONAL LOG: I was sitting on a bench with a friend at a park one day. I noticed she had closed her eyelids and was moving her

slightly uplifted head gently to the right and left, across the sun.

She did not know about "sunning" by reading or hearing about it. This was simply natural for her to do. She has normal sight.

THE SUNNING SANDWICH

One way to develop better brightness-to- darkness and darkness-to-brightness adaptation is to alternate sunning with palming. You can enjoy closed-eyeUd sunning for three minutes, followed by three minutes of palming. Then do three minutes of sunning again, three minutes of palming, and so forth. Palming is described in Chapter 21, "Palming and Acupressure."

STROBING (OR FLASHING ) W H I L E

SUNNING

Do not do this activity if you are prone to photo-convulsive seizures.

Another variation on sunning is to flicker your fingers in front of your closed eyelids. This creates a stroboscopic or flashing effect, which stimulates micro-movements in the eyes.

BATES O N L I G H T

From Perfect Sight Without Glasses:

It is not light but darkness that is dangerous to the eye. Prolonged exclusion from the light always lowers the vision, and may produce serious inflammatory conditions. Among young children living in tenements this is a somewhat frequent cause of ulcers upon the cornea, which ultimately destroy the sight. The children, finding their eyes sensitive to light, bury them in the pillows and thus shut out the light entirely.

ChapU r SLXU i n LiH'hl

The universal fear of reading or doing fine work in a dim light is. however, j unfounded. So long as the light is sufficient so that one can see without discomfort, this practice is not only harmless, but may be beneficial.

Sudden contrasts of light are supposed to be particularly harmful to the eye There is no evidence whatever to support these statements.... Such practices as reading alternately in a bright and a dim light, or going from a dark room to a well-lighted one, and vice versa, are to be recommended. Even such rapid ... fluctuations of light as those involved in the production of the moving picture are, in the long run, beneficial to all eyes. I always advise students to go to the movies frequently and practice centralizing. They soon become accustomed to the flickering light, and afterward other light and reflections cause less annoyance.

ARTIFICIAL LIGHTING

Until man duplicates a blade of grass, Nature can laugh at his so-called scientific achievements.

—Thomas A. Edison

Ever since Thomas Edison invented the electric light bulb in 1 8 7 9 , w e have been participating in an experiment with artificial light. Due to modern technology the amount and quality of light many people are exposed to has been radically altered.

Quantitatively, many people in our society are outdoors only 10% of the time, compared to 80% before the invention of the electric light bulb. When outdoors, many people wear dark sunglasses, which reduces even further their reception of natural sunlight—an essential nutrient.

Qualitatively, the spectrum of light we are under when indoors differs significantly from the natural light our visual system has evolved under. Many studies have shown that common types of artificial light can be harmful to our health.

For example, studies have shown that biological stress and learning difficulties increase when individuals are under standard "coolwhite" fluorescent tubes. Based partly on research by Dr. Fritz Hollwich6 in 1980, Germany placed a ban on cool-white fluorescent fights in medical facilities.

Conventional lighting, including standard incandescent light bulbs and cool-white fluorescent tubes, are very poor substitutes for natural sunlight. If a person is going to spend a great portion of the day indoors, it is important to weigh the benefits and drawbacks of various types of artificial lighting.

Since there are disadvantages with each type of artificial light, no artificial light is an adequate substitute for natural sunlight. What type of hghting is best for homes and workplaces? The answer is complicated.

See the Light Comparison Table in Appen- dix D.

NATURAL, "FULL - SPECTRUM " SUNLIGH T

See Plate 26: Spectral Power Distribution

Curves.

"Outdoor Daylight" shows the sun providing a fairly even distribution of the visible spectrum. Notice how the "Outdoor Daylight" spectrum changes depending upon the location and time of day.

Outdoor sunlight also provides a small amount of midand near-UV light in about a 1:10 ratio.

Note that the vertical and horizontal axes are different between "Outdoor Daylight" and the other three graphs. Spikes in fluorescent spectrums are characteristics of the phosphor coating used inside the tubes.

T H E C C T S A N D C R I S O F LIGHT

Changes in a light's spectrum are, in part, due to the source's temperature, known as chromaticity, or Correlated Color Temperature (CCT). CCT is a measure of a light source's apparent "whiteness," yellowness (warmth), or blueness (coolness), and is measured in units of degrees Kelvin (K). CCT is a measure of the light source's direct appearance to our eyes. CCT measurements do not include the midand near-UV spectrum.

A candle flame has a very warm, orange/yellow CCT of approximately 1600K; the sun and sky at sunrise are 1800K (yellow/warm); one hour after sunrise, the sun has a CCT of approximately 3600K (warm); at noon 4870K (slightly warm; almost white); an overcast sky is approximately 7100K (bluer/cooler); the Northwest sky is 25,oooK (very blue/cool). Near 5500K, the sunlight is "white."

Notice the inverse relationship with CCTs—a "warmer" light source has a lower CCT, and a "cooler" light has a higher CCT. The terms "warmer" (yellow/orange/red) and "cooler" (blue/indigo/violet) refer to the psychological effects of the light source, not its temperature.

Another indicator of a light's "naturalness" is the Color Rendering Index (CRI), which ranges from 1 to 100. CRI indicates how wel the colors of objects are rendered (reflected), using a light source at a specific CCT. Outdoor sunlight has a "perfect, natural"CRI

rating of 100. Unlike CCT, CRI measurements include visible spectrum and midand nearUV factors.

The CRIs of lights that have different CCTs cannot be compared. This is because even though two light sources may have the same CRIs, they may render colors very differently if they have different CCTs.

An incandescent bulb with a high CRI of 95, but a low CCT of 2700K, is yellow/red intense and blue-deficient. See Plate 26, "Incandescent." It would not be valid to compare this incandescent bulb's light quality to another light with a CRI of 95, but a higher CCT of 5000K. It is valid to compare the CRIs only of lights that have the same CCTs.

Generally, a light source with a CCT of 5000K and a CRI of 80-89 will give a good color rendering. A CCT of 5000 and a CRI of 90-100 will give excellent color rendering.

light. At least one company says that the proper ratio of midand near-UV light must be included in the light to be considered "truly" full spectrum.

Some modern fluorescent tubes or fixtures have these characteristics. Most standard incandescent and halogen bulbs have very high CRIs, but low CCTs. So, they do not "qualify" as full-spectrum lights.

An additional consideration is how efficiently the light is produced. Efficiency, also known as efficacy, is measured in lumens per watt. Lumens refers to the amount of light produced; wattage is the power consumed. A very high-wattage light bulb or tube may produce a small amount of light, and therefore, would be relatively inefficient. A more efficient light bulb or tube may produce a large amount of light with the same or even fewer watts.

Let's review the pros and cons of various types of artificial lights.

THE QUEST FOR A R T I F I C I A L ,

FULL-SPECTRUM L I G H T I N G

In recent years light manufacturers have become aware of the many benefits of fullspectrum lighting. They have attempted to improve on the poor (and many say unhealthy) light spectrums provided by standard incandescent and cool-white fluorescent lights. Much research and development has gone into creating an artificial light (or combination of lights) that attempts to emulate, as closely as possible, the natural full-spec- trum light provided by the sun.

In evaluating artificial light sources, both CCT and CRI need to be taken into consideration. Generally, light that has a CCT between 5000K and 7500K and a CRI of 90 or more is considered to be "full-spectrum"

" R E G U L A R , " I N C A N D E S C E N T , T U N G S T E N L I G H T B U L B S

Regular incandescent lightbulbs were invented by Thomas Edison in 1879. Incandescent bulbs use a tungsten filament (wire) that glows when electricity passes through it.

Advantages of regular, incandescent bulbs:

1.Initial cost is low.

2.Easy to replace.

3.Provide good contrast and shadow— contrast is important to sight.

4.Variable brightness, by changing wattage.

5.Very high CRI of 95-98.

6.Can be used with dimmer (variable) switches, although dimming produces an even more distorted spectrum. If a

low level of light is desired, it is better to use a lower-wattage bulb than a "dimmer" switch. The lower-wattage bulb produces a better spectrum than a higher-wattage bulb lowered in wattage by a dimmer.

Disadvantages of regular, incandescent bulbs:

1. Expensive in the long term due to frequent replacements—much shorter lifetime than fluorescent tubes.

2.Inconvenience of frequent replacement.

3.Minimal midand near-UV light is emitted.

4.A very low CCT of 3000K. As can be

seen in the Plate 26, "Incandescent" graph, incandescent bulbs provide a very poor balance of colors, being very yellow-red intense, and violet-blue deficient. Note that natural sunlight peaks in the blue region.

5.As can also be seen from Plate 26, incandescent bulbs are very energyinefficient in regards to the production of light. Ninety percent of the energy from an incandescent bulb is given off not in the form of light, but as infrared heat; essentially, an incandescent bulb is an expensive space heater.

6.Approximately 22% of light output is lost during lifetime.

7.Many bulbs fail when switched-on or jarred.

8.Much less efficient than advanced fluorescent tubes.

9.Sixty-cycle flicker.

The incandescent bulb has a relatively high "visual efficiency" because the human visual

system has a greater sensitivity to yellow than blue. In other wordb, an incandescent bulb emits a high amount of energy in the yellow region, and we see yellow better than the other colors. Even though it has a high CRI of 95-98, the total spectrum is very imbalanced, and objects illuminated by this light render colors very "warm."

There are some incandescent bulbs that claim to be "full-spectrum." One such popular bulb has no CCT or CRI ratings on its package. The intensity of fight from a 150-watt bulb seems like the light from a standard 75watt incandescent bulb. The color of light appeared unnatural (dull purple) to some people. Some students say the spectrum looks more natural, and therefore feels better, than a regular incandescent bulb. One product claims an average life of 3500 hours, compared to a typical 750-hour, standard incandescent bulb.

"QUARTZ" HALOGEN LIGHTBULBS

Halogen lightbulbs contain a tungsten filament and halogen gas (typically iodine), which results in a "whiter" spectrum than most incandescent bulbs and higher lumens per watt (greater efficacy). Halogen lightbulbs are often used in automobile headlights.

Because halogen bulbs operate at a higher temperature, they require the use of quartz glass instead of regular glass. Halogen bulbs are usually more expensive than regular incandescent bulbs.

Advantages of halogen bulbs:

1.Very bright and can be precisely focused.

2.High CRI, 95 typical.

3.Last longer than incandescent bulbs.

4.Approximately 12% more energy-effi- cient than incandescent bulbs.

5.Can be used with dimmer (variable) switches.

6.Lose less light over its hfetime than incandescent bulbs; 10% light loss versus the incandescent's 22%.

Disadvantages of halogen bulbs:

t. Low CCT.

2.Initial cost higher than incandescent bulbs.

3.High heat output, sometimes requiring a special fixture.

4.Much less efficient than advanced fluorescent tubes.

5.Much shorter lifetime than fluorescent tubes.

6.Sixty-cycle flicker.

One report recently warned of supposed harm of UV from halogen light. Unlike regular glass used for regular incandescent and most fluorescent lights, UV light created in the halogen bulb is transmitted through the quartz glass. One government agency is recommending people not use halogen lights unless manufacturers add "regular glass" to prevent the UV from escaping.

The reader will need to decide whether different sources of UV light are harmful or beneficial.

HIGH-INTENSITY DISCHARGE ( H I D ) LIGHTS

High-Intensity Discharge (HID) lights are made in three types: mercury, sodium, and metal halide.

Mercury HIDs are the older type. They have a high CCT but a very low CRI. Mercury HIDs are not as efficient as the newer HIDs, and are becoming obsolete.

Sodium HIDs have higher CRIs, but lower CCTs.

Metal halide HIDs have CCTs ranging up to 3800K, and CRIs up to 75.

Because of their very high efficiencies, modern HIDs are used primarily outdoors to fight large areas at night, like streets and parking lots. HIDs cannot be used with a dimmer.

" C O M P A C T " FLUORESCENT ( C F ) LIGHTS

"Compact fluorescent" (CF) fights fit in standard "screw-in" light fixtures and can, therefore, replace many standard incandescent bulbs. Because some CFs are taller and wider than regular incandescent bulbs, they may not fit into some lamps or lighting fixtures unless a taller lampshade harp or a socket extender is used.

The lower-wattage CFs are rated to be equivalent to much higher-wattage incandescent bulbs. For example, an 18-watt CF is often stated to be the equivalent of a 75watt incandescent bulb.

However, CFs seem to put out less light than the "equivalent" incandescent bulb. This is partly due to the high visual sensitivity to yellow and the yellow-intense incandescent bulb factors discussed above. There can be a period of adjustment when switching to CFs. CFs are more economical in the long run because they last much longer than incandescent bulbs.

Many of the newer CFs use the much improved electronic ballast discussed below.

I am not aware of any CFs that provide midand near-UV spectrum. Also, many CFs do not produce as much contrast as incandescent bulbs. Contrast is important to eyesight.

Current CFs cannot be used with dimmer switches

One-piece (integral) CFs use a built-in ballast, which can be either electronic or magnetic. Integral CFs have the disadvantage of having to throw away the entire unit when it burns out.

Two-piece (modular) CFs incorporate a reusable magnetic ballast contained in the screw-in base, and a replaceable fluorescent tube that attaches to the base. The tube is typically rated at 10,000 hours, while the base/ballast is rated at approximately 50,000 hours.

Modular CFs currently use only magnetic ballasts—a disadvantage. The magnetic ballast in a CF base can be much heavier than the light incandescent bulb it is replacing. As a consequence, replacement in some fixtures may not be practical. The wattages of both the tube and the ballast need to be added to get the total wattage of a modular CF.

Never use any type of fluorescent light with a dimmer switch, even if it is set atfull power. Doing so could cause premature burn-out, and could create a fire hazard.

FLUORESCENT L I G H T S

Standard fluorescent tubes, invented in 1938, are much more energy-efficient than incandescent bulbs. In contrast to the 1 0 % efficiency of incandescent bulbs, approximately 30% of the energy used to power fluorescent tubes is converted to light.

Many "full-spectrum" fluorescent tubes are not only energy-efficient, but have a much longer lifetime than typical cool-white fluorescent tubes. So, even though the full-spec- trum tubes have a higher initial cost, their long-term cost can be much less than the equivalent light from standard fluorescent tubes. The longer lifetime also eliminates inconvenient, frequent replacements of tubes. I have found this to be major advantage.

As seen in Plate 26: Spectral Power Distri- bution Curves, the typical "Cool White" fluorescent tube provides an imbalanced spectrum compared to "Outdoor Daylight." The phosphor composition in the "Cool White" maximizes the yellow-green region, where our eyes are most sensitive to colors. The "Cool White," which has a low CRI of 68 and a CCT of only 4200K, is deficient in the green, blue, violet, and UV parts of the spectrum. Like incandescent bulbs, cool-white fluorescents are deficient in the blue region, where sunlight has its maximum intensity.

There are many types of fluorescent tubes, ranging from cool-white to the advanced fullspectrum tubes.

F L U O R E S C E N T T U B E T Y P E S

For many years, most fourand eight-foot fluorescent tubes had a diameter of one and a half inch, known as tubes.

Some manufacturers now produce more efficient, one-inch-diameter "T-8" fluorescent tubes. T-8s are rated at 32 watts, while the larger T-12S typically operate at 40 watts. The smaller surface area inside theT-8s allows the use of more expensive and efficient phosphor combinations. T-8s can produce more lumens (light) per watt and can result in higher CRI ratings (at CCTs of 5000-5500K). However, the total lumen output is usually less than that from T-ios and T-12S.

Even though T-8s have a smaller diameter, the bipin width is the same as the standard This means can be used in standard fluorescent fixtures. T-ios have an inter-

mediate diameter of a ilA", and have the same bipin width as the T-12S and T-8s. T-5S are miniature, low-wattage (typically 6W) tubes, with a small bipin width.

P A R T F I V E : L I G H T , T H E R E T I N A , A N D

ADVANCED FULL-SPECTRUM

FLUORESCENT TUBES

As can be seen in Plate 26, "C50" (Chroma 50) produces a more balanced spectrum than the "Incandescent" bulb and the "Cool White" fluorescent tube. The Chroma 50's spectrum is closer to the spectrum of "Out­ door Daylight." The Chroma 50 has a CCT of 5000K, and a CRI of 90.

"DIFFUSION IS STILL CONFUSION"

"Full-spectrum" fluorescent tubes do not, by themselves, provide adequate hghting.

Due to the design of fluorescent tubes, and the way fluorescent tubes use phosphors to produce light, fluorescent light is more dif­ fused than incandescent (point) light sources. Diffused light gives a relative dullness to objects, i.e., less contrast

A CF is slightly less diffused than a stan­ dard four-foot fluorescent tube because of the CF's smaller size.

Contrast is very important to sight. Sight functions largely by the detection of edges and shadows. Contrast indoors can be obtained by using incandescent or halogen bulbs, or by allowing natural sunlight to enter through windows or skyHghts.

S T E R E O S C O P I C V I S I O N

Many fluorescent fixtures have plastic cov­ erings, called diffusers. Since UV light is absorbed by conventional diffusers, it is impor­ tant that the UV light produced by spedal flu­ orescent tubes not be absorbed by the diffuser.

There are three solutions to this problem:

1.Use a special UV-transmitting diffuser.

2.Use an "egg-crate" diffuser, which has large, square holes through which the light passes—a practical solution; eggcrate diffusers are available at many hardware and lighting stores.

3.Do not use a diffuser; however, aesthetics may not make this a practical solution.

BALLASTS FOR FLUORESCENT LIGHTS

Unlike regular incandescent bulbs, fluores­ cent tubes require a transformer, or ballast, to regulate the electricity delivered to the tubes Ballasts come in two types: the older magnetic type, also known as "core-coil," and the newer electronic type. Usually, either type will power two four-foot, 40-watt (or less) flu­ orescent tubes.

Advantages of magnetic ballasts:

1.Initially less expensive than the newer electronic ballasts.

2.Already installed in many fluorescent fixtures.

FLUORESCENT HARDWARE

CONSIDERATIONS

The fluorescent tubes mentioned above will fit in most fluorescent fixtures. However, flu­ orescent lights cannot be used with dimmer switches—at least not yet.

Some fluorescent tubes emit the midand near-UV spectrum. The glass or plastic used with some fluorescent tubes is specially designed to let the UV light out of the tube.

Disadvantages of magnetic ballasts:

1.Many have an annoying hum or buzz. Magnetic ballasts have sound ratings, which are usually indicated on the label on the ballast. A ballast with sound rat­ ing "C" can be annoying—especially if listened to for a long time. If you are going to use a fluorescent fixture con­ taining a magnetic ballast, be sure to

get the quieter type with sound rating "A." Unfortunately, the sound level can increase over time with either type.

2. Physical vibration, which can cause the entire fixture, especially the metal parts, to vibrate, producing additional irritating noise.

3.Less energy-efficient than electronic ballasts, which makes them more expensive to operate in the long run.

4.Subtle but "unnerving" flicker, or strobelike, effect. Magnetic ballasts alternate off and on at 60 cycles per second. This flicker can be eliminated by converting the source of power from alternating current (AC) to direct current (DC), but this would be impractical for many people.

5.Generation of more heat than

electronic ballasts.

6. Delay, accompanied by flickering, when starting.

7. Heavier than electronic ballasts.

Advantages of electronic ballasts:

1.Silent; no noise; no vibration.

2.Thirteen to twenty-five percent more energy-efficient than magnetic ballasts, which makes them less expensive to operate in the long run.

3.Operate at 20,000-25,000 cycles (on/off) per second; no noticeable flicker or stroboscopic effect.

4.Start more quickly (nearly instantaneously) than magnetic ballasts.

5.Operate cooler than magnetic ballasts.

6.Weigh less than magnetic ballasts.

Disadvantages of electronic ballasts:

1.Higher initial cost.

2.May need to replace magnetic ballasts in current fixtures.

Chapter Sixteen: Light

Ballast issues can become very complex. Ballasts come in different grades, or qualities. Also, some manufacturers recommend "matching" a specific ballast with a specific fluorescent tube. These issues are beyond the scope of this book.

Considering the advantages of electronic ballasts, they are highly recommended.

Investigate BEFORE You Invest"

Since new technology in lighting is often expensive, it is worthwhile comparing prices of lights and hardware. Consult with lighting manufacturers, and lighting and hardware stores in your area.

Since advanced types of fluorescent lights have a very long lifetime, and since you probably will not replace these lights until they burn out, it may be worthwhile spending some time to research which ones are best for you.

As advanced lighting products are produced in greater quantities, and as more companies enter this market, prices should come down. For example, the cost of some electronic ballasts has dropped from $59 to $39 in the last four years.

There is a myriad of features in the new lights and fixtures. So, as a financial advisor once cautioned his students, "Investigate before you invest."

Helping the environment is another reason for using energy-efficient full-spectrum fluorescent tubes, CFs and electronic ballasts.

X - R A Y S , A N D O T H E R R A D I A T I O N

At least one light researcher has expressed concern about, and has gone to lengths to eliminate, low-level x-rays coming from cathodes of fluorescent tubes.