Burma border eyeglass and refraction manual_English_Update Mar 09.pdf

Border Eye Care Program

Eyeglass and Refraction Training Manual. Page 1

Table of Contents

OPTICS 3 BASICOPTICS LENS POWER THE DIOPTER MAGNIFICATION AND MINIFICATION COMBINING LENS POWERS DIOPTERS AND LENS POWER VISION ANATOMY 13 VISUAL PATHWAY OPTICS OF THE EYE ACCOMMODATION BASIC REFRACTIVE ERRORS 21 HYPEROPIA AND MYOPIA CHECKING VISION 25 VISION COMPLAINTS CHECKING DISTANCE VISION PINHOLE TEST NEAR VISION TESTING NEAR VISION CHART THE BASIC REFRACTION 33 TOOLS FOR REFLACTION DISTANCE REFRACTION DISTANCE REFRACTION WITH TRIAL LENSES OF LENS BARS GOOD TECHNIQUE IN REFRACTION CHECKING DISTANCE REFRACTION RESULTS DOING A DISTANCE REFRACTION WITH THE FOCOMETHER PRESBYOPIA 38 NEAR REFRACTION 40 ASTIGMATISM 41 APHAKIA 45 STRABISMUS AND AMBLYOPIA 47 STRABISMUS AMBLYOPIA PROBLEMS IN REFRACTION 50 PROBLEMS STARTING THE REFRACTION OVER MINUSING RURING DISTANCE REFRACTION OVER PLUSING DURING NEAR REFRACTION DECINING WHAT POWER TO GIVE WHEN EACH EYE IS DIFFERENT PATIENT CANNOT SEE WELL WITH THE BEST LENS FOUNG IN REFRACTION NORMAL CHANGES IN VISION DURING LIFETIME 55 CHANGES IN MYOPIA AND HYPEROPIA DURING LIFETIME USUAL PROGRESSION OF MYOPIA$$$$ USUAL PROGRESSION OF HYPEROPIA DISEASES, DRUGS AND THE EYE 57 REASONS PEOPLE COME FOR EYE EXAMINATIONS 58 POOR VISION SEEING SPOTS ITCHING AND BURNING PAIN IN THE EYE SUNLIGHT PAINS THE EYE



EYEGLASSES 61 ANATOMY OF EYELGASSES TYPES OF EYEGLASSES ADJUSTING EYEGLASSES NOTES 66 BIBLIOGRAPHY 67



Optics

Basic optics

Optics is the science or study of how light travels. Light travels to fast for us to

watch it move. You can try this by turning the light on in a room. You cant see

the light start from the light bulb and travel to the corners of the room. Light

travels at almost 300,000 kilometers PER SECOND. Nothing else moves as fast as

light.

Think of light as being the same as the man walking. A man can walk on the road

faster than he can walk through the river. Light also slows down when it travels

through something other than air. Light travels a little bit slower in water, glass

and other materials because they are thicker than air. Even thought light travels

slower in material other than air, it is still much to fast for us to see it move.

A MAN WALKING ALONG THE ROAD IS WALKING IN ARE. HE WALKS AT NORMAL SPEED



A MAN WALKING IN THE RIVER TRAVELS SLOWER THAN THE MAN WALKING ON THE ROAD. THE WATER MAKES IT

MORE DIFFICALT TO WALK SO THE MAN WILL WALK SLOWER.

LIGHT TRAVESING IN AIR AND IN GLASS. THE ARROWS (LIGHT RAYS) TRAVEL FAST IN AIR. WHEN THE LIGHT RAYS

ENTER A THICKER MATERIAL SUCH AS GLASS, THEY SLOW DOWN. WHEN THE LIGHT RAYS COME OUT OF THE

GLASS AND GO BACK INTO THE AIR, THEY SPEED UP AGAIN.



When light enters a new material at an angle (not from straight on) the light will

BEND as it slows down in the new material.

$$

LIGHT RAYS HIT GLASS AN ANGLE, WHEN LIGHT RAYS DO NOT ENTER THE GLASS STRAIGHT ON, THE LIGHT RAYS IS BENT.

You can sometimes see an example of this when looking at an object that is in the

water. If you have ever tried to stab the fish that is in the water, you will know

what I mean. Another easy to see example is when you put a pencil in a glass of

water.



PENCIL IN A GLASS OF WATER. THE LIGHT RAYS SLOW DOWN IN THE GLASS AND IN THE WATER. THE LIGHT RAYS

ARE ALSO BENT, BECAUSE THEY DO NOT ALL ENTER THE GLASS AND THE WATER STRAIGHT ON. IF YOU LOOK AT

THE PENCIL IN THE GLASS FROM SOME ANGLES, IT WILL MAKE THE PENCIL LOOK LIKE IT BENDS WHEN IT ENTERS

THE WATER. THE PENCIL WILL ALSO LOOK LARGER UNDER THE WATER THAN ABOVE THE WATER.

This bending of light is how eyeglasses work and how magnifying glasses and

microscopes work. Refraction is the word we use to describe the bending of

light. By changing the shape of the curves on the front side and on the backside

of eyeglass lenses, we can change how the light is bent and we can change the

power of the lens.

Remember, when light hits glass or material other than air, it slows down. When

light passes through other material at an angle, the light is bent or refracted.

Using this idea, we can bend glass lenses to different shapes to control how

much the light is bent or refracted.

If we look at the side of a magnifying

glass, we will find that the shape of

the lens, when seen in cross section,

looks like this.

CROSS - SECTION OF A PLUS LENS

This shape is an example of a Plus Lens. When seen in cross section, the plus

lens is thicker in the middle than it is at the outside edges. When light passes

through the plus lens, it is refracted and comes to a focus on the other side of the

lens. When we refract or bend light this way, we say that we are converging the

light. A plus lens is a lens that will converge light.



CROSS-SECTION OF A PLUS LENS, CONVERGING THE LIGHT ON THE OTHER SIDE OF THE LENS

Plus lenses are not the only kind of lens. We also have Minus Lens. A minus lens

is exactly the opposite of the plus lens. When seen in cross section, the minus

lens is thicker at the outside edges and thinner in the middle of the lens.

CROSS-SECTION OF A MINUS LENS.

When light goes through a minus lens, it does not come to focus on the other

side. The light is not bent inwards to converging the light. When we refract or

bend light out, we say that we are diverging the light. In a minus lens, the light is

refracted outwards and the light is diverged. A minus lens is a lens that will

diverge the light. The light does not come to focus on the other side of the lens,

the light is scattered out more

CROSS SECTION OF A MINUS LENS DIVERGING THE LIGHT RAYS.



Lens Power

Not all plus lenses have the same power, or same ability to converge light. The

thicker the plus lens is in the middle, the stronger the power. A plus lens of a

strong power will refract the light more than a plus lens of weaker power.

CROSS-SECTION EXAMPLES OF WEAKER AND STRONGER PLUS LENSES.

The same is true for minus lenses. The thicker the lens is at the edges, the

stronger the power of the lens. A minus lens of strong power will diverge light

more than a minus lens of weaker power.

CROSS-SECTION EXAMPLES OF WEAKER AND STRONGER MINUS LENSES.



The Diopter

Diopter is the term we use to describe the units of power in lenses. A three

diopter plus lens will refract light more than a one diopter plus lens. A three

diopter minus lens will refract light more than a one diopter minus lens. When we

talk about plus and minus lenses, we use the word diopter to describe how much

power the lens has. When we write about lenses we use the following method:

+2.00 D = a two diopter plus lens

-2.00 D = a two diopter minus lens

We use a plus or a minus sign to describe if the lens is plus or minus. We use the

decimal point because we can have powers less than one diopter and powers

that are between diopters.

+1.50 D = a one and one half diopter plus lens

-1.50 D = a one and one half diopter minus lens

+0.75 D= a three quarters (3/4) diopter plus lens

-0.75 D= a three quarters (3/4) diopter minus lens

+10.25 D = a ten and one quarter (1/4) diopter plus lens

-10.25 D = a ten and one quarter (1/4) diopter minus lens

Most eyeglasses are made in quarter (1/4 or 0.25) diopter steps or in half (1/2 or

0.50) diopter steps. The higher the diopter power, the stronger the lens. If we

look carefully at a pair of eyeglasses, the front curve of almost all eyeglasses will

look like a plus lens. The lenses in eyeglasses are not made straight up and

down as we see in the top set of drawings. Eyeglasses are made curved so that

they look better and fit more naturally around the head and the eyes.



CROSS-SECTIONEXAMPLES OF NORMAL LENS AND EYEGLASS LENS. LEFT SIDE ARE PLUS LENS EXAMPLES AND

RIGHT SIDE ARE MINUS LENS EXAMPLES.

Magnification and Minification

Plus lenses magnify, or make things look bigger. When you look through a plus

lens, the picture of what you are looking at gets bigger. The more plus power that

you have, the larger the picture will be.

Minus lenses minify, or make things look smaller. When you look through a minus

lens, the picture of what you are looking at gets smaller. The more minus power

you have, the smaller the picture will be.

GRID FOR TRYING DIFFERENT POWER OF PLUS LENSES AND MINUS LENSES. NOTICE HOW THE LINES GET BIGGER

AND SMALLER DEPENDING UPON THE TYPE AND AMOUNT OF POWER THAT YOU USE.



Combing Lens Powers

Sometimes when we work in the eye clinic, we put more than one lens in front of

the eye. How do we know the power when we have two or more lenses together?

We add the powers together. For example:

+1.00 Diopter lens and a +2.50 Diopter lens = +3.50 Diopters

+1.00

+2.50

+3.50

+1.00 Diopter lens and a -250 Diopter lens = -1.50 Diopters

+1.00

-2.50

-1.50

What happens when we use a +1.00 Diopter lens and a -1.00 Diopter lens

together? We end up having NO POWER. When we have a lens with no power,

such as with ordinary sunglasses, we refer to this as being Plano. Plano is the

word we use to describe 0 Diopters when we talk about lens power.

On the next page is a chart to help you understand about Diopter power and plus

and minus lenses.



M in u s L e n s g e t th ic k e r a t th e e d g e s P lu s L e n s g e t th ic k e r in th e m id d le

In c re a s e d - in c re a s e d m in if ic a t io n In c re a s e d + in c re a s e d m a g n if ic a t io n

in m id d le a n d e d g e sP la n o L e n s s a m e th ic k n e s s

M o re M in u s (-) P o w e r M o re P lu s (+ ) P o w e r

-2 .5 0-3 .5 0 + 2 .5 0

L e n s P o w e r is M e a s u re d in D IO P T E R S

0

-1 .0 0-2 .0 0-3 .0 0

+ 3 .5 0

-4 .0 0-5 .0 0

-0 .5 0-1 .5 0-4 .5 0

+ 5 .0 0

P la n o

+ 4 .5 0

+ 1 .0 0 + 2 .0 0 + 3 .0 0 + 4 .0 0

+ 0 .5 0 + 1 .5 0



Vision Anatomy

Before we can learn about refractive errors and eyeglasses, we will need to learn

a bit more about anatomy of the eye and how the eye and brain work together so

we can see. From the Primary Eye Care Manual, you should remember all of the

parts of the eye as listed below. If you have forgotten, please read your Primary

Eye Care Manual to refresh your memory.

FRONT VIEW OF EYE AND CROSS SECTION VIEW OF EYE.

From the Primary Eye Care Course you should remember that the cornea must be

clear in the area in front of the pupil or we will not have good vision. If the cornea

is not clear in this area, light cannot pass into the eye. We should also remember

that the lens needs to be clear to have good vision. After light passes through the



cornea, it also must pass through the lens or light wont reach the retina and we

wont see well.

CROSS-SECTION VIEW OF EYE.

Between the cornea and the lens, we have a clear fluid called aqueous humour

(or DaqueousE). Between the lens and the retina, we have a clear jelly called

vitreous humour (or DvitreousE). Both the aqueous and the vitreous need to

remain clear or we will not have good vision. Light needs to be able to pass from

the front surface of the eye all of the way to the back, inside the eye or we will not

have good vision.

The tear layer, cornea, aqueous, lens and the vitreous are all like windows for the

eye. If they are not clear and if they are not clean, then it is not easy to see

through them.

The ciliary muscle (also called the ciliary body) is located just behind and a little

bit up from the iris. The ciliary muscle and the iris muscle are connected. The

ciliary muscle is connected to the lens by special small wires called zunules.



Visual Path way.

The eye is connected to the brain. Inside of the eye, the retina receives the

picture from the outside world. The retina is like the film in the camera. The

DpictureE from the outside goes to the retina. The retina is connected to the optic

nerve. The optic nerve comes out of the back of the eye and connects to other

nerves, which connect to the seeing part of our brain. The optic nerve and the

other nerves are like a telephone line that sends the picture from the retina to our

brain.

CROSS-SECTION VIEW OF OPTIC NERVES

We can have an eye that is 100% healthy and normal and still not see well, or

even be blind. If the nerves that connect the eye to the brain are not healthy, the

brain can not see. We can have bad vision or blindness if the seeing part of the

brain is injured or has disease.



CROSS-SECTION VIEW OF HEAD WITH VISUAL PATHWAY.

Our eye reads light and sends a message on the optic nerve to the brain. Our

brain reads the message that comes from our eyes. Sometimes we will not

always read the message from the eyes correctly. It is important to understand

about the nerves that connect the eye to the brain and that out brain interpret

these messages.

A person can have a normal healthy eye, but still not see well if there is a problem

with the nerves that connect the eye to brain or if there is a problem with the

seeing part of the brain.

Understanding that our brain interprets the message from the eyes is important to

remember when we do refraction because this can affect our refraction results.

We will discuss this more lately on in the course.

We learned how to check vision and examine the outside of the eye during the

primary eye care course. To see if the inside of the eye is healthy or not, we need

to use a special instrument. We can do this with an ophthalmoscope. We do not

have instruments to use in the field that allow us to see all along the optic nerve or

to look at the seeing part of the brain.



Sometimes the way a person feels can affect vision. For example, one patient

comes to the clinic and is happy healthy and has healthy eyes. We find that they

have 20/20 vision in both eyes. Another patient comes and this patient is very

tired and hungry and has many problems at home. We find that the eyes are

healthy, but that the vision is 20/30 or 20/40. The eye may work well but the brain

may not see so well if the patient is tired, ill or has a lot of stress.

Optics of the Eye

We have learned already that light slows down in material other than air so we

know that light will slow down a little bit as it travels inside the eye. We have also

learned that light will bend or refract if the surface of the material is not straight or

if light comes in on an angle. Because the cornea is curved and because the

lens is curved, the light is refracted as it enters the eye.

CROSS SECTION VIEW OF LIGHT RAQYS ENTERING THE EYE. LIGHT IS REFRACTED BY CORNEA AND LENS AND

FOCUSES ON THE RETINA.

Light comes into the eye and puts a picture on our retina. The light needs to be

refracted as it enters the eye so that the DpictureE is focused clearly at one place

on the retina. The retina takes the picture and sends it to the brain through the



optic nerve. If the light is not focused on the retina, then the picture that the retina

sends to the brain is not clear.

If part of the eye, such as the cornea or the lens, have the wrong power, light will

not focus on the retina and we will not have clear vision. The more far away that

the light is focused from the retina, the more blurry the vision is.

The eye is a plus lens. Most of the plus power of the eye comes from the cornea

(about +40.00 Diopter) and from the lens (about +20.00 Diopter). It the lens is

removed in cataract surgery and an artificial lens is not put in the eye, a very

strong plus lens eyeglass in needed for the eye to see clearly.

Accommodation

Looking at the cross section of the eye below, we should already know all of the

parts shown in this drawing.



The ciliary muscle surrounds the lens. When the ciliary muscle is flexed

(contracted) the shape of the lens changes. The muscle contracts and through

the zonules (special tissue like wires) this changes the shape of the lens.

This causes the lens to bend and become thicker in the middle. When we make

the center of the lens thicker, we add plus power. The lens becomes more plus

powered when the ciliary muscle is flexed. We call this change to the lens shape,

accommodation. It is important for us to understand about accommodation if we

want to do a good job of refraction.

Why do we need to change to focus in the eye? Think of an expensive camera

with an adjustable lens. When you look at something far away that is in focus

through the camera, and then change to look at something close, the close object

is not clear until you change the focus.

Our eye works the same way. We cannot focus at for away and up close at the

same time. You can try this yourself. Look straight ahead at something far away,

such as the nose of your friend on the other side of the room. Hold your pencil or

pen up to eye level about a half meter from your face and now look at the tip of

your pen. When you look at the tip of the pen, your friends nose will not be clear.

When you look at you friends nose, the tip of the pen will not be clear.

EXAMPLES OF DIFFERENT FOCUS FOR DISTANCE AND NEAR VISION. LEFT SID IS AN EXAMPLE OF CLEAR

DISTANCE VISION. RIGHT SIDE IS AN EXAMPLE OF CLEAR NEAR VISION.



NORMAL EYE LOOKING AT DISTANCE

When looking at 6 meters or more the picture is focused on the retina.

NORMAL EYE LOOKING AT NEAR WITHOUT ACCOMMODATION.

When we look at things at near (up close, such as when reading or sewing), the

picture is focused BEHIND the retina if we do not accommodate.

NORMAL EYE LOOKING AT NEAR WITH ACCOMODATION.

When we accommodate, we make more plus power for the eye. With more plus

power, we can move the focus back up to the retina and see clear again.



Basic Refractive Errors

Hyperopia and Myopia

If the cornea is curved too much, or is not curved enough, then the light will not

focus on the retina. The light will focus either in front of the retina or behind the

retina. If this happens, we do not see clearly because the light is not focused

exactly on the retina. If this happens, we have a refractive error. We have a

refractive error when the eye does not focus the light coming from a distance

correctly on the retina.

CROSS-SECTION EXAMPLES OF BASIC REFRACTIVE ERRORS AND THE NORMAL EYE. HYPEROPIA (TOP)

NORMAL (MIDDLE) AND MYOPIA (BOTTOM).

In the three cross section drawings of the eyes seen above, identify the eye with

normal vision. The two eyes that do not have normal vision are different from

each other. Can you describe how they are different?



In the top example, the vision in this eye will not be clear because the light does

not focus on the retina. In this example, the light is not bent enough to focus on

the retina, so it focuses somewhere behind the retina. When light coming from

the distance focuses behind the retina, we call this condition Hyperopia.

In the middle example, the vision is normal because the light is focused on the

retina. In this case there is no refractive error.

In the bottom example, the vision in this eye will not be clear because the light

does not focus on the retina. In this example, the light is bent too much and

focuses in front of the retina. When light coming from the distance focuses in

front of the retina, we call this condition Myopia.

Hyperopia and Myopia are two major types of refractive error. Why do some eyes

have refractive errors while other eyes do not have refractive errors? We do not

know all of the reasons, but we do know that family history (genetics) sometimes

determines if a person has a refractive error or not.

So, let us put all of this information together. The eye will refract the light so that

the light will focus on the retina. If the eye cannot refract the light correctly, we

have a refractive error. If the light is refracted too much and the light is in focus in

front of the retina, we have myopia. If the light is not refracted enough and the

light is in focus behind the retina, then we have hyperopia. To correct myopia we

need to diverge the light. The light needs to focus farther back, on the retina, so

we need to diverge the light with a minus lens.



EXAMPLE OF AN EYE WITH MYOPIA WITHOUT EYEGLASS CORRECTION(TOP) AND WITH EYEGLASS

CORRECTION(BOTTOM).

To correct hyperopia we need to converge the light. The light needs to focus

closer up, on the retina, so we need to converge the light with a plus lens.

EXAMPLE OF AN EYE WITH HYPEROPIA WITHOUT EYEGLASS CORRECTION (TOP) AND WITH EYEGLASS

CORRECTION (BOTTO)



How do we know how much power (how many diopters) to give to correct myopia

or hyperopia? We have to do some clinical testing. Earlier we learned that the

word refraction meant to bend the light. Refraction has two meanings.

Clinically, refraction is the testing of the eye to determine the type and strength of

refractive error. Thus we can say that we do refraction when we test the eye to

find the type and strength of refractive error.

Why do we have refractive error? Refractive errors happen when one or more

parts of the eye are not the correct size or shape. For example, if the cornea has

to much curve, the eye will have too much plus power and we will need minus

power to correct it for good vision.

Genetics (family history) can be part of the reason that some people do not have

the correct size or shape for some parts of the eye, but we do not completely

understand why this happens. On the border, we can expect about 10% of the

population to have myopia or hyperopia.



Checking Vision

Vision Complaints

To start diagnosing refractive errors of myopia and hyperopia, we start with the

case history. Does the patient complain of blurry vision at distance? Does the

patient complain about near vision? Does the patient complain about both

distance and near vision? If the patient complains of both distance and near blur,

do they report that the distance vision is worse or that the near vision is worse?

The case history is our first clue as to what type of refractive error that we may

have. Generally speaking, myopia is more of a problem with distance vision while

hyperopia causes more problems with near vision. Remember this.

After the case history, we must check the vision, very carefully, using the eye

chart. We check the vision eye by eye, because each eye is a different patient

and may not have the same problem. We should always check the right eye first.

Whenever you do any type of testing or examination on the eye, it is good

practice to always do the right eye first. If you make a habit of always do the right

eye first, it is easier to remember which eye is which when you are recording the

results of your examination in the medical records.

Checking Distance Vision

To check vision you need to use an eye chart. There are many kinds of eye

charts. Look carefully at the eye chart that you have available to use. On the

chart there will be instructions about what distance to use. Most charts are made

to be used at 6 meters. Some charts are made to be used at 3 meters. Here are

the important steps in checking vision.



V

Preparing

Chart must be placed at the proper distance, with good light and no glare. It is

best to put the chart about the same height as the eyes. If the chart is too close,

it is too easy to see the letters. If the chart is too far, it is too difficult to see the

letters.

Instructing

Explain to the patient that you need to determine what the vision is like in each

eye. Instruct the patient to point their finger in the same direction as the DEE that

you point to on the chart. If the patient does not understand, you can bring them

close to the chart and show them how the E points in different directions.

Testing

Test the vision EYE BY EYE. Check the right eye first. Do not block the view of

the chart with your body or with your pen or pointing stick.

Recording

Record results eye by eye in the medical record. Write a large V with an R and

an L to indicate right and left eye. Put the best vision measured for the right eye

next to the R. Put the best vision measured with the left eye next to the L. The

vision is the number next to the smallest line that the patient can see clearly. To

record the vision you can write like this:

R 20/50

L 20/50



Some charts will use different kinds of numbers for measuring vision. The charts

used in this program will use D20E measurements, which is the most common

measurement for vision. Some charts will use numbers like 6/6, 6/12.6/18, etc. or

numbers like .9, .8, .5 etc. Some charts will use English letters, numbers, and

letters from other languages, or pictures to measure vision.

EXAMPLES OF DISTANCE VISION CHARTS.

Because you want to check the vision EYE BY EYE, the eye that you are not

testing needs to be covered. When checking vision, check the vision of the right

eye first. To do this you must cover the left eye. The patient can cover the left

eye with their hand. Have them cover the eye with the palm of their hand. They

should not cover their eye with the fingers of their hand.



EXAMPLES OF CORRECT AND INCORRECT WAY TO COVER EYE WHEN CHECKING THE DISTANCE VISION.

Pinhole Test

Pinhole testing is another way to check vision. Pinhole testing is useful because it

can help you to decide if bad vision is due to needing eyeglasses, or if bad vision

is due to a health problem inside the eye. If the vision is normal. You do not need

to do the pinhole test. Vision that is 20/40 or better is normal. We do the pinhole

vision test the same was that we do the regular vision testing. The only difference

is that we must put the pinhole in front of the eye that we are checking.

If the vision is bad, the cause of the bad vision might be because the patient

needs eyeglasses, or might b because there is another problem with the eye. If

there is a problem on the outside of the eye, we can usually determine this from

the external eye examination. Sometimes there is a problem inside the eyeball,

but we do not have special instruments to look inside the eye. Doing the pinhole

test in cases of bad vision can help us to decide if the patient should be referred

for eyeglasses or other problems.

If the vision improves when looking through the pinhole, then at least part of the

problem is because the patient needs eyeglasses. If the vision does not improve



V

when looking through the pinhole, then eyeglasses may not help and there and

there may be another problem.

We write the results of the pinhole test the same way that we write the results of

the regular vision test, only we add the word DpinholeE under the V:

R 20/50

L 20/50

Pinhole

Even if you do not have an eye chart to check the vision, the pinhole test can be

used. Have the patient look through the pinhole and ask them if their vision is

better with the pinhole, or better without the pinhole.

The pinhole test works best when the distance vision is between 20/40 and

20/200. The pinhole test does not always work well if the patients vision is very

bad.



V

Near Vision Testing

After we check the vision at distance, and we also check the near vision with a

special near vision checking chart. The near vision chart is held at a comfortable

reading distance from the eyes, as seen in the drawing above.

Near vision charts can use letters, words or pictures of different sizes to

determine the near vision. Check the near vision, eye by eye starting with the

right yet. Record the results when you are finished so you do not forget! This is

how we record the near vision in the medical records:

R 20/50

L 20/50

Near



After checking both the distance and near vision, eye by eye and then recording

the results in the medical chart, we must then examine the eyes very carefully to

check for possible eye diseases.

It is very important to check the health of the eye by looking carefully to be sure

that are parts look normal, including underneath the eyelid. The patient may

come to the eye clinic complaining about blurry vision due to a refractive error,

but we might also find they have trachoma or xeropththalmia or some other

problem.

If any eye diseases are found, you must treat the patient for the problem. The

blurry vision may be due to cataract, cornea scar or an eye disease rather than

from a refractive error. If a condition is found that can reduce vision, we may still

want to see if refractive errors are responsible for some of the vision loss.

We can make a tentative diagnosis after the case history, checking the vision and

examining the eye. Most of the time, people with Myopia will say the distance

vision is worse than the near vision. People with Hyperopia will usually complain

that the near vision is worse than the distance vision. The fast way to find out

about this is to ask the patient Dwhich is worse, distance vision or near vision.E

The results of your vision check may not always be right because the patient may

not understand the vision test well or you might make a mistake when checking

the vision. It is VERY important that you give good, clear instructions to the

patient when you check vision and that you try to check vision as carefully as

possible.



The Basic Refraction

Once we think we know what type of refractive error the eye has, how do we

decide the amount of diopters needed to correct the refractive error? To

determine the type of refractive error and the amount of diopters needed to

correct the refractive error, we do refraction.

We learned that refraction was the word used for the bending of light. The word

refraction also has another meaning. We can also use the word refraction to

describe the clinical testing for refractive errors.

Tools for Refraction

The simplest way to do a clinical refraction is by Dtrial and error.E This means that

we try different lenses to find the lens that works the vest. Sometimes we can do

this by trying lenses one by one. These lenses might be from a special box of

lenses called a Dtrial lens set.E These kits are called trial lens sets, and each lens

is labeled with the amount of diopter power. A trail lens set will also usually

include a Dtrial frame.E The trial frame is an adjustable frame that you can put the

trail lenses in.

EXAMPLE OF A TRIAL LENS SET.



We can also use a lens bar set to check the refractive error. The lens bar sets

have the basic lens powers put to gather in order on pieces of wood or plastic.

The lenses are put in order from weaker power to stronger power

EXAMPLE OF LENS BARS.

In shops in bigger towns and cities, there are computers that can do the

refraction to find the power of the eye. There are hand held instruments that eye

doctors and other trained people use (called retinoscopes) that can also find the

refractive error. We can even do refraction by using different powers of ordinary

eyeglasses.

Distance Refraction

If we are going to use the Dtrail and errorE method with the trial lens set or the lens

bars, we need to pick a power to start with. It is possible just to try any lens and

then another lens power until you find the right power, but this can take a long

time and is not a very organized way to do refraction. It is easy to make mistakes

this way.

From our patient history and from checking the vision, we should have a good

idea if the patient has hyperopic or myopia. The patient with hyperopic will



complain that the near vision is worse than the distance vision. The patient with

myopia will complain that distance vision is worse than the near vision.

If we think that the patient has hyperopia, we start our distance refraction with a

+1.00 lens. If we think that the patient has myopia, we start our distance

refraction with a -1.00 lens.

Distance Refraction with Trial Lenses or Lens Bars

1. Have the patient cover their left eye so that you can test the right eye.

2. Have the patient look at the distance (6 meter or more).

3. Place a +1.00 lens in front of the right eye - have the patient look through the

lens.

4. Change between having no lens in front of the eye and having a +1.00 lens in

front of the eye several times.

5. Ask the patient if their eye is best or if the lens is best.

6. * If the +1.00 lens is best - repeat steps 4 and 5 but these times use a +1.00

lens and a +1.50 lens.

7. If the +1.50 lens is best, repeat steps 4 and 5 with a +1.50 and +2.00 lens.

(Each time you repeat, increase the power by +0.50 diopters)

8. When you find the best lens, check the distance vision in the right eye with the

best lens.

9. Record the best lens for the right eye and the distance vision with the best lens

for the right eye.

10. Repeat procedure on the left eye.

* If the patient reports that the eye is better than the +1.00 lens, then check

again, this time using a -1.00 lens.

The distance refraction procedure is the same for myopia, only you start with a -

1.00 lens and use minus lenses.



Good Technique in refraction

How we hold the lenses in front of the eye is very important. We need to hold the

lens directly in front of the eye without tilting the lens up or down, left or right. The

center of the lens needs to be placed so that it is in front of the center of the pupil.

Which one of these drawings above is showing the correct way to place a lens

bar in front of the eye?

Checking Distance Refraction results

The power that we find that is best for the patients eye is called the best distance

lens. We ADD +1.00 Diopters power to out best distance lens and check the

vision again. When you add +1.00 Diopters to the best distance lens, the vision

should not be so clear. The vision should be worse than, the vision with the best

distance lens.

If the vision is just as good or better with +1.00 and the best distance lens

together, then we need to redo our refraction because we may have made a

mistake.



We check our refraction by using a +1.00 Diopter lens over our best distance

lens. It does not matter if our best distance lens is plus or minus.

Doing a Distance Refraction with the Focometer

The Focometer is another tool we can use to determine the distance refraction.

To use the Focometer, we

We start by turning the Focometer to a high plus power.

We have the patient look though the Focometer at a distance object.

The patient then turns the dial on the Focometer until the picture FIRST

becomes clear.

Repeat to make sure the patient stops at the same power.

Note the best lens power found and check vision on the distance vision chart.



Presbyopia

When we start to get old, the lens inside the eye also gets old. As the lens gets

older, it does not bend and change shape as easily. When the lens cannot

change shape so easily, we loose the ability to accommodate. The natural loss of

accommodation is called presbypia. Presbyopia is not a disease of a refractive

error. Presbyopia is natural; it is related to age and happens to every person. As

we loose the ability to accommodate, it becomes more and more difficult to see

thing s clearly up close.

In most people on the border with normal eyes, this becomes a problem

sometime between the age of 35 and 40. At about this age, most people are

ready for reading glasses, which are plus powered glasses that give us back

some of the plus power that we need in order to see clearly up close. This

process of the lens getting harder to bend because of age continues to about

age 65. After that the lens doesnt bend anymore at all.

Because of this gradual change with age, the power we need for reading glasses

gradually increases between the age of about 35 or 40 and the age of about 60

or 65. In the normal eye that does not have any distance refractive error (myopia

or hyperopia) we can make a simple chart to show the amount of plus power

needed for reading glasses for different age.

AGE ADD POWER

40 to 45 +1.00

46 to 50 +1.50

51 to 55 +2.00

56 to 60 +2.50

61 and older +3.00



The above chart is an approximation only. Each patient is a little bit different, but,

if the eye is healthy and there is no distance refractive errors (myopia or

hyperopia) this chart will work pretty well.

We usually call eyeglasses that correct for presbyopia Dreading glasses.E Even if

a person cannot read, reading glasses are helpful for sewing and ding other

things up close.

We can use math to help us find the reading power. First we need to do careful

distance refraction. Then we need to know the age of the patient. The amount of

power in the chart is called an DAddE because it is the amount of power that we

ADD TO THE DISTANCE POWER to find the reading power.

A patient is 40 years old and has +2.50 Diopters of hyperopia; we would ADD

+1.00 to the +2.50 to the distance power to find the NEAR power.

+1.00

+2.50

+3.50

If the patient were a 40 year old with -2.50 Diopters of myopia, we would ADD

+1.00 to the -2.50 distance power to find the NEAR power

+1.00

-2.50

-1.50



Near Refraction

If we were very careful in doing the distance refraction and we know the age of

the patient, we have a very good idea what the reading power should be for the

patient. This will not work every time so we need to do a near refraction to find

the reading power.

We do a near refraction the same way that we do distance refraction, only we

have the patient look at a near chart at their ordinary reading distance. If the

distance refraction is the same for both eyes (within 0.50 diopters) we can do the

near refraction with both eyes together.

If the patient does not have a big distance refractive error, we can start the near

refraction with a +1.00 lens and work our way up to the correct power in +0.50

steps.

If the patient has a large distance refractive error (either hyperopia or myopia)

then we can calculate what the reading power should be for their age by adding

the distance refraction and the add power for their age. When we find what the

reading power should be, we can use this as a starting lens.

To check to make sure that the reading power that we find works well, let the

patient sit with the reading lens on for about 20 minutes and have them read a

magazine, book or newspaper.

NO NEAR REFRACTIONS ON ANYBODY UNDER AGE 35



Astigmatism

There is one type of refractive error that we cannot provide eyeglasses for on the

border. This type of refractive error is called astigmatism. Astigmatism is the

case when the cornea does not have a perfect shape. In the perfect cornea, the

front of the cornea is shaped like apiece of a Ping-Pong ball. The power of the

curve is the same in every direction because the Ping-Pong ball is perfectly

round.

EXAMPLE A PERFECT ROUND CORNEA.

In most people the cornea does not have a perfect shape. Instead of the front

surface of the cornea having a shape like a ping-pong ball, the front surface of

the cornea has the shape of an egg.

EXAMPLE OF AN EGG SHAPED CORNEA.

Because the cornea does not have the same curve in every direction, the power

of the eye is different along the long curve of the cornea than it is along the short

curve of the cornea. For example, the power of the short curve on the cornea



may be something like +40.00 and the power of the long curve on the cornea

may be something like +42.00.

Most people in our area only have a little bit of astigmatism, or no astigmatism.

When there is only a little bit of astigmatism, a normal refraction and a normal pair

of eyeglasses will work with no problem.

In a small percent of the people, there will be enough astigmatism to affect the

vision. With a trial lens set, lens paddles, or lens bars it is difficult to know if there

is astigmatism or not. This can sometimes give you a headache if you are trying

to do a good refraction.

You do the best distance refraction that you can. If the vision in the eyeglasses is

not good, then you might have astigmatism. How can you tell? Have the patient

look through the best lens that you can find with the refraction. If the vision is not

perfect or not good, then one or more of the following reasons may be

responsible:

- You have not found the best lens with your refraction.

- The patient does not understand your instructions very well, and does not

respond correctly to help you find the best lens.

- There may be a health problem or some other problem with the eye, other

than a refractive error.

- You may have astigmatism.

The first thing to do is to do your refraction again. This time, be very careful that

you give good instructions to the patient and that the patient understands you.

If you find that you still do not have good vision, you will need to be sure that you

have ruled out problems on the outside of the eye and cataracts. You might have

a problem inside the eye. If you dont have an ophthalmoscope and a lot of



training, you will not always know for sure. If you feel that there is no problem with

the eye and that you are doing a good refraction and that the patient understands

well. You may have astigmatism.

One way to try to diagnose this problem is to put the lens in front of the eye that

give you good vision and ALSO put a pinhole in front of the eye. This usually

works best if you put the pinhole closest to the eye and the lens on the outside of

the pinhole. Make sure that the lens is centered in front of the pupil. If the vision

improves when you use a pinhole and you best lens, you probably have

astigmatism.

We cannot provide eyeglasses that correct for astigmatism on the border at this

time. Eyeglasses that correct for astigmatism cost a lot and it takes a lot of

training and extra equipment to be able to diagnose astigmatism well. Also, it

would be impossible for us to keep all of the possible astigmatism powers

supplied.

If you feel confidant that your patient has astigmatism, and regular eyeglasses

give some improvement in vision, you can go ahead and give the regular

eyeglasses.

You will have to very carefully explain to the patient that the ordinary eyeglasses

will help the vision a little bit, but not 100%. You will need to explain to the patient

that to get the best vision, they will have to have special eyeglasses. You will also



need to explain to the patient that it is not possible to provide special eyeglasses

in our eye clinics.

How do astigmatism eyeglasses work?

Astigmatism eyeglasses also have two curves on the lens, just like the front of the

egg. Because the lens has two curves, the vision will look DfunnyE if you turn the

lens as you look through it.

Astigmatism can happen in eyes with Myopia and can also happen in eyes with

Hyperopia.



Aphakia

Aphakia is the word we use to describe an eye that does not have a lens inside.

Anytime you see somebody with aphakia, it is usually because they have had

cataract surgery to remove the natural lens and did not get an implant lens.

Sometimes aphakia might be from an unusual injury.

When you do not have a lens inside the eye, you will need very high plus power

lenses to see clear. This happens because the lens inside the eye is a plus lens

and with aphakia, you dont have a lens anymore.

How do we do refraction for aphakia? The same way as we do any refraction. In

this case we need to use high plus power lenses to see clear. In some cases the

patient with aphakia may need a power that is as strong as +13.00 or +14.00 or

as low as +8.00 or +9.00. Most people with aphakia will need a plus power lens

about +10.00 to +11.00 Diopters.

Without eyeglasses, the person with aphakia is almost blind. They can see light

and sometimes see very large things when they are close by, but usually cannot

see anything else.



NOTE: Not all patients who have had cataract surgery have aphakia. Many times

the eye surgeon will put an artificial lens inside the eye after taking out the old

lens with a cataract. In this case there is no aphakia, because there is a new,

artificial lens inside the eye.



Strabismus and Amblyopia

Strabismus

Strabismus is when the eyes are crossed. Sometimes one eye crosses in and

sometimes one eye crosses out. Other words that people might use to describe

strabismus are Dcross - eyedE Dwall - eyedE or Dtropia.E (Tropia is a medical word.)

EXAMPLES OF STRABISMUS. WHICH EYE IS NOT STRAIGHT IN DRAWING A AND DRAWING B?

Most people with strabismus will need to have surgery to make the eyes straight.

Sometimes, the eyes can be made straight by wearing the right eyeglasses. In

some cases, the person with strabismus has hyperopia, usually a high amount of

hyperopia. If you can do a good refraction and find a plus power for someone

with strabismus, ask them to return for a follow up in a few months. After a few

months you can check the refraction again and maybe will find that they need

even more plus power.

You might find that using plus eyeglasses will help to keep the eyes straight, but

not every time.

If you have a patient with strabismus, do a refraction to see if you find plus power.

If you find the patient meed eyeglasses, give them eyeglasses. Also put them on



your eye surgery list because most of the time, surgery is the only thing that will

help.

Amblyopia

You do a very good refraction, but one eye does not have good vision. You

suspect astigmatism, but find that a pinhole does not improve the vision in the

bad eye. You recheck your external examination and look again carefully for

cataracts. You suspect some problem inside the eye and refer to your doctor.

The doctor looks inside the eye and finds nothing is wrong. What is the problem?

You might suspect amblyopia.

Amblyopia is the word we use when an eye con not see well, even with the best

glass and even when there is no disease of the eye or the optic nerves or brain.

Sometimes amblyopia is also called DLAZY EYE.E

When we have amblyopia the usual reason is that one eye has much more power

than the other eye. The eye with the high power will usually not see very well,

even with the best eyeglass.

This usually happens when a baby is born with a higher power in one eye than in

the other eye. The brain will be lazy and always look with the eye that has the

best vision. In this case it is the eye with the least amount of power. After you are

about 7 years old, the brain will no longer even try very hard to look at the picture

from the eye with the high power. Even if you put the correct lens in front of the

eye, the brain has given up already and wont pay attention to vision coming from

that eye very much.

You cannot always tell if you have amblyopia or not, but if you can rule out

astigmatism, and all diseases of the eye, and if the eye has a high power, then

maybe you have amblyopia.



For amblyopia in older children and adults, there is nothing you can do. If the

other eye needs eyeglasses, you give eyeglasses according to the power of the

other eye.

For small children who you suspect have amblyopia, patching the eye can

sometimes help the brain to use the eye to see. Many times strabismus and

amblyopia will happen together in the same eye.



Problems in Refraction

Problems starting the Refraction

We usually know if the patient has myopia or hyperopia from the patient history

and from checking the vision. Sometimes if we dont know for sure, we can ask

the patient to compare a +2.00 lens to a -2.00 lens to see of they like plus or

minus better. This can help us to start the refraction if we dont know where to

start.

Sometimes a patient with a very high refractive error might not be able to decide

if a +2.00 of a -2.00 is best. If this happens we can try higher powers. We can

ask them to compare a +5.00 lens to a -5.00 lens.

Over Minusing during Distance Refraction

Many times a patient will want to have too much minus power in the distance

during the refraction. Why does this happen?

When we look in the distance, our eye can accommodate and give our eye more

plus power. If you are doing refraction and the eye is accommodating, the

patient will want more minus than they really need for the distance vision. If they

have myopia they will want too much minus power. If the patient has hyperopia,

they will not want enough plus power.

DOver minusingE can cause problems for the patient later on. When the eye is not

accommodating, then the power is not correct and they cannot see clearly.

We can do a few things to help prevent Dover minusingE during our examination.

The first thing we need to do is to make sure that the patient is really looking 6

meters or more in the distance. If the patient looks at a closer distance then they



will be accommodating. The closer they look, the more they will be

accommodation.

The second thing that we can do is to have the patient wear the gets distance

lens power that we find for them for a while. After you find you best distance lens,

let the patient wear these lenses for 20 or 30 minutes to be sure that they like it.

When they are wearing the distance lenses, they should be looking at the

distance and not reading or other near vision looking.

We can also check our refraction. When we finish with the refraction, put +1.00

over the best distance power and have them look at the eye chart again. The

patient should loose about one line of vision on the chart.

For example, if you find that the best distance vision is 20/20 with the best

distance lens, the vision should be 20/25 or 20/30 when you put a +1.00 lens over

the best distance lens.

If the vision does not get worse when you add +1.00 to the best distance lens,

you have over minuses the patient.

Over plusing during Near Refraction

When the eye looks as something close thought a plus lens, the picture gets

bigger. This is the reason that we DO NOT do a near refraction for people who

are younger than 35 years old. Every body will like too much plus at near. Plus

power makes the picture bigger and easier to see.

Over plusing is not a problem of accommodation, because when we

accommodate we make even more plus power. The reason that the brain

sometimes likes to have too much plus is that the picture gets DbiggerE and the

brain thinks that it is seeing Dbetter.E When this happens the patient may tell us



that they want +3.50 Diopters when they really only need +2.50 Diopters for near

power.

When you do the refraction, you only spend a few minutes testing the patients

eyes. If they take too much plus power at near, it may seem good to them for a

short time, but after a while, the plus power will be uncomfortable for them.

We can check to make sure that we have given presbyopia patients the correct

power by finding the reading power with math. We can find this by adding the

distance refraction to the amount of power we should add for their age.

If we find that the amount of reading power the patient likes during the refraction

is a lot different from the power they should have for their age and distance

refractive error; we might be over plusing.

To check for over plusing, we have the patient sit with the best reading power that

we find and have them read or do something else with near vision for 20 minutes

or so. If they are comfortable with the vision after that amount of time, they will

probably be OK.

Deciding what Power to give when each eye is different

We are lucky because in our area, the power in the right eye is usually the same

as the power in the left eye. But, sometimes you may find that the power in the

right eye is different than the power in the left eye. What do you do?

If the power in the right eye is different than the power in the left eye, most of the

time they will be very close. For example:

R = +3.50 (20/20)

L = +3.00 (20/20



In a case like this where the power is 0.25 or 0.50 different between the right and

the left eye, you can have the patient try eye glasses for both powers for a while.

Let them try the +3.00 for 15 or 20 minutes and let them try the +3.50 for 15 or 20

minutes. Let the patient decide which one is best.

If the power in the right eye is a lot different than the power in the left eye, then

most of the time the eye with the least amount of power will be the best. You will

probably want to give them eyeglasses for the eye that has the least power.

For example:

R = -2.50 (20/25)

L = -4.00 (20/40)

If they use -2.50 eyeglasses, the right eye will see well, but the left eye will not see

so well. If they use -4.00 eyeglasses the right eye will see OK, but the left eye will

not see well. Usually the patient would be more comfortable having eyeglasses

with the least amount of power. In most cases, if the vision is good in both eyes,

but he power is different between the right and the left eye, you would give the

eyeglasses for the eye that have the least amount of power.

If there is a big difference between the right and the left eye, and the vision is not

the same, you probably want to give the power for the eye that has the best

vision. This will usually be the eye that has the least amount of power. For

example:

R =-2.00 (20/20)

L = -5.50 (20/80)

If there is a very big difference between the right and left eye, and with the best

lens in front of each eye, the eye that has the stronger power will usually not have

good vision. This is usually amblyopia, which we will talk about later. In a case



like this, we would ALWAYS give the eyeglasses for the eye that has the least

power, which also has the best vision

Maybe if the patient has a small cataract or some other problem in one eye and

the vision is not so good, we would give the eyeglasses for the other eye, even if

the power is stronger. For example:

R = +1.00 (20/80) small cataract

L = +2.00 (20/30) healthy eye

This is a case where we would give the stronger power because the eye with the

stronger power can see well.

Sometimes you may not be sure what to do. If you cannot decide what power to

give, then let the patient try both powers for 20 minutes or so and let them decide

which power is more clear and comfortable.

Patient cannot see well with the best lens found in refraction

As mentioned before, sometimes you do your best job for refraction and the

patient still cannot see well. This may be because of astigmatism, a problem

inside the eye, amblyopia or a problem with the optic nerve or the seeing part of

the brain. We can usually rule out astigmatism by using a pinhole with the best

distance lens and checking the vision again, as written in the chapter on

astigmatism. We should look again carefully at the eye to make sure that we did

not miss a cataract or other disease that we can see. We might be able to refer

the patient to somebody who has an ophthalmoscope to rule out diseases inside

the eye.



Normal changes in Vision during Lifetime

NEWBORN

- The eye of the newborn does not have very good vision.

- The eye of the newborn does not accommodate very well.

INFANTS

- By the age of about six months, the eye should be seeing and

accommodating normally.

SMALL CHILDREN

- Small children, up to about the age of 6 or 7 years, will usually have a small

amount of hyperopia

- This hyperopia in small children is usually not a problem and glasses are

not needed most of the time

OLDER CHILDREN

- eyes in older children are usually Plano

OVER AGGE 34

- In the late 30s, people have lost enough accommodation to have

problems reading or doing other near vision work.

- These people will need reading glasses for presbyopia.

OLD PEOPLE

- Most old people will eventually develop Cataracts if they live long enough.

- The cataract may cause the eye in crease in myopia (or reduce

hyperopia).

- The other clear parts of the eye (cornea, aqueous, vitreous) also start to

get a little bit cloudy.

- The retina also starts to get old and not see very well

- The vision of most old people will not be perfect.



Changes in Myopia and Hyperopia during Lifetime

Usual Progression of Myopia

- Myopia usually starts to develop in older children and in teenagers.

- Myopia usually increases until the patient is in their 20s.

- People over 30 who develop myopia should be checked for diabetes.

- Old people may start to show some myopia when cataracts start to

develop

- Sometimes pregnant women start to show a little bit of myopia, this usually

returns to normal 1-2 months after delivery.

Usual Progression of Hyperopia

- Hyperopia may be present at birth and usually starts to develop in early

childhood or in infancy.

- Hyperopia may increase power a bit during early childhood years.

- Hyperopia will usually decrease in older children and in teenagers.

- Some people over age 35 starting to have Presbyopia may also show

Hyperopia. These people probably always have had Hyperopia, but were

accommodating to see clearly.

- A sudden change (increase) in Hyperopia in adults, especially older

adults, is usually from a swelling in the retina.



Diseases, Drugs and the Eye

Many, many diseases and drugs affect the eye. There is not enough time to talk

about all of the possible effects in this short course. The notes on this page are

very general.

Any disease that affects the blood vessels can affect the eye. The two most

important examples are Hypertension and Diabetes. These problems affect the

eye because they affect the blood vessels in the retina. If there is any

hemorrhaging of blood vessels in the retina, vision will be affected. Check for

BOTH diabetes and for hypertension if you see any hemorrhaging in the retina.

MOST DRUGS have at least some side effects on the eye, especially if given in

very high doses. Some of the more common examples are given here:

Steroids - can cause cataracts and can cause glaucoma

TB Medicine (Ethambutol) - can affect the optic nerve in some people

Chloroquine - can affect the retina and the optic nerve

Quinine - can also affect the retina

Oxygen - can cause vision loss in blindness in pre mature babies



Reasons People Come for Eyes Examinations

Most people come to eye clinics because of vision problems, People also come if

they think they have an infection (red eyes or discharge) have had and eye injury

or if they have pain around the eyes or other reasons.

Poor vision

Poor vision is the most common eye complaint. Refractive errors and diseases

can reduce vision and should always be considered and ruled out. One common

complaint is for patients to say that they cannot read for very long at night. It is

difficult for anyone to read or do near detailed work by candle light or lantern light

as it is normal to have slightly reduced vision in such circumstances.

Vision can also be reduced for psychosomatic reasons. It is common to have

minor visual complaints from people who are under stress. In the refugee setting,

this is fairly common in young adults.

**********************************************************************************************

A Sudden lose of vision is never normal.

Any case of sudden lose of vision should be examined very carefully and

referred, if need be.

**********************************************************************************************

Seeing Spots

People will sometimes complain about seeing spots, or sometimes having DfliesE

or DmosquitoesE in the eyes. This is a very common conditions referred to as

floaters. Cells and other debris are contained inside the eye in the vitreous

humor. Sometimes the cells and debris will cause small shadows, which appear

as small dark spots or DinsectsE when they fall upon the retina. These spots or

DfloatersE are only noticeable when the patient is in a well, lighted area or



outdoors and are easiest to see when they are near the line of sight. Usually

floaters are of no concern.

Itching and Burning

Many people will complain about itching and/or burning sensations in the eyes.

Often these people will also report increased tearing. Such complains may be

due to infections and thus the eye should be carefully examined for trachoma,

conjunctivitis, blepharitis and other infections. The eyelids of these patients

should be everted to rule out trachoma or presence of foreign bodies. May times,

the examination will reveal no problem. The dusty environment in the dry season,

use of face powder (which may get into the eye) and other environmental irritants

are usually responsible for these recommend they be regular in washing the face,

particularly around the lids and eyes, and be careful when applying face powder.

Some of these complaints of itching, burning and tearing may be due to mild

allergies. In older people and in people with certain arthritic conditions, these

same complaints may be due to Ddry eyesE which results from a decrease in the

volume and quality of the tears.

Pain in the Eye

Pain in the eye is a complaint that many patients will report. If a careful

examination reveals nothing wrong with the eye, pain in the eye is more likely to

be pain around the eye. Because many of the sinus cavities are near the eye, it is

common for patients to sense pain from sinus congestion or sinus infections as

eye pain. Migraine headaches can also seem to be coming from the eye.

Severe pain around the eye needs to be examined carefully. Sudden severe

pain, especially if around only one eye can be a sign of glaucoma.



Sunlight Pains the Eye

Eye sensitivity to sunlight is different for every person. On a sunny day in the hot

season, everyones eyes will be sensitive to the sun. Any damage to the cornea

can cause the eye to feel pain from sun light, so the cornea must be examined for

scratches, abrasions and infections. Examine the eye carefully, everting the

upper lids to look for foreign bodies and check the eyelashes for trichiasis.



Eyeglasses

Anatomy of Eyeglasses

a. Lens - the glass or plastic lens

b. Bridge - part of the frame that fits over the nose

c. Temple - the DarmsE that fit over the ears and connect to the face

d. Hinge - the connection between the face and the temple of the frame

e. Face - the front part of the frame

f. Nose pads - some frames have nose pads, some do not have nose pads



Types of Eyeglasses

a. Single Vision Lenses:E SingleE vision means that there is only one lens for each

eye (not a bifocal).

b. Half - Eyes: Half - glasses - you look over the top where there is no lens to see

distance. You look down, thought the lens for the reading power.

c. Bifocals: Top lens is for distance vision and the bottom lens is for the reading

power

d. Bifocals: another example.



Adjusting Eyeglasses

Adjusting the temples of the eyeglasses is very important for making the

eyeglasses fit well for the patients face. When you make any adjustments to the

temples, you should hold the temple that you are adjusting with both hands and

bend slowly but firmly.

EYEGLASSES SHOULD NOT ROCK WHEN PLACED ON THE TABLE AS SHOWN IN THE EXAMPLE HERE.

EXAMPLES OF TEMPLE ADJUSTMENT AROUND THE EARS.



TEMPLES SHOULD BE ADJUSTED STRAIGHT ACROSS AS SHOWN IN THE EXAMPLE HERE.

THE TEMPLES SHOULD NOT DIG INTO THE SKIN IN FRONT OF THE EARS OR BEHIND THE EARS.

THE TEMPLES SHOULD BE EVEN WHEN SEEN FROM THE SIDE. ONE SIDE SHOULD NOT HANG DOWN MORE THAN

THE OTHER SIDE.



Adjusting the face of the frame is also important. You need to be very careful

when trying to change the shape of the face, because the lens can come out if

you bend too much. If you bend too much where the face meets the temple, you

can also damage the hinge.

THE FACE FO THE FRAME SHOULD BE TILTED JUST A LITTLE BIT AS SEEN IN THE DRAWING HERE.

THE FACE OF THE FRAME SHOULD BE STRAIGHT WHEN YOU LOOK AT IT FROM THE TOP.



Notes

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Bibliography

The provision of spectacles at low cast. Geneva, World

Health Organization, 1987.

Kassalow, J., Rutzen, D. Providing low - cost spectacles.

New York.

Vincent, J. eye care in the field - a manual for health

professionals. Bangkok, American Rescue Committee, 1996

Vincent, J. Burma border primary eye care manual. Chiang

Mai, International Rescue Committee, 1999.

Vincent, J. Trainers Manual for Burma Border Primary Eye

Care Course. Chiang Mai, International Rescue Committee, 1999.

Documents

Burma border eyeglass and refraction manual_English_Update Mar 09.pdf