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Eye Power

More about kids eye problems

What is eye Power 

Eye Power is the collection of numbers and some alphabets that are mentioned in glass prescription that your eye doctor gives you.  It is the power of the lens that you will be wearing to see clarly. 

Eye power is actually known as refractive errors.

The eye power can be written with a plus or a minus sign. 
SPH stands for sphere or spherical

CYL stands for Cylindrical

Add stands for addition

OD stands for Oculus Dextrus meaning right eye
OS stands for Oculus Sinister meaning Left eye
OU stands for Oculus uterque meaning both eyes.

The glasses or contact lenses can have three types of numbers or eye powers

These are :

  1. Myopia –  A-minus numbered lens or minus eyesight power
  2. Hyperopia – A plus numbered lens or plus power eye
  3. Astigmatism – A plus power eye or minus power eye with an added axis to that number.

What do these different eye numbers mean? 

Let’s look at each of the types of eyesight numbers that one can have in their lenses.  In other words, let's try and understand what eyesight number is. Many must have heard the terms nearsightedness or farsightedness.  Let's understand what these mean.


Myopia is also called Nearsightedness.  This is the most common eyesight number.  Refractive error is a more technical name for eyesight power.
People with nearsightedness will have difficulty reading road signs and seeing distant objects.  In other words distance, visual acuity is affected.  Near is not.  You will yet see well for close-up tasks such as reading, mobile phone, and computer use.

Here, lenses have a minus number, and Myopia occurs because the eyeball is longer than normal.

If an eye doctor were to write this glasses number on a prescription, it would look like -0.50DS or -0.75DS or -1.25DS.  We wouldn’t write it as -0.50 power of eye or eyesight number.  Here DS stands for diopter sphere.  DS is the measurement of eyesight number.


This is also known as farsightedness or long-sightedness.  Some amount of Farsightedness is normal in younger children.  Here the lens is of a plus number.  Plus, sight means that the eye is slightly shorter than normal.  Despite having plus power eye, children can see things.  They may be seeing these things blurred, but they can still see things.  Thus, in children, this often goes unnoticed. Some children born with farsightedness have never seen close objects well. They may not be aware that it’s possible to see them better.  Also, hyperopic children can sometimes see close objects well by straining their eyes. Thus plus sight means they may complain of headaches, but not blurring.  These headaches occur due to them focusing hard to see things.

If an eye doctor were to write this glasses number on a prescription, it would look like +0.50DS or +0.75DS or +1.25DS.  We wouldn’t write it as +0.50 power of eye or eyesight number.

Please note that people tend to equate plus numbers of hyperopia with reading glasses.  While reading glasses have a plus number, there can be situations where a child who does not need reading glasses specifically still has a plus number.  The reading glasses that people usually associate a plus number with are seen in people above 42 years of age because of age-related weakness in the eye muscles.

Astigmatism or Cylindrical number

If you have astigmatism, you will have blurred vision at all distances. One may also complain of eyestrain and headaches.  Children also tend to squeeze or ‘squint’ their eyes to see better with astigmatism.   An Astigmatism prescription could contain both plus and minus numbers, but along with the numbers, they have an axis written next to it.  These eye numbers are also known as cylindrical numbers.

If an eye doctor were to write this glasses number on a prescription, it would look like -0.50DC*180 degrees or -0.75DC*90 degrees or -1.25Dc*110 degrees.  We wouldn’t write it as -0.50DC*180 power of eye or eyesight power.  Here DC stands for diopter cylinder.

There is something important you should know.  These powers are usually seen in both eyes.  These eyesight numbers are somewhat similar in both eyes most of the time.  Sometimes, these numbers can be very different in each eye.  Let's say the left eye has a number of -4.0 Diopter, and the right eye has a number of -0.50 Diopter.   In this situation, the person would see with the right eye and may not notice poor vision in the left eye. 

Normal Eye Power

It is but obvious that normal eye power would mean that a person can see everything very clearly without glasses.  So zero eye power.  

When we say someone has never needed glasses then it means they can see for both far and near clearly. This however, is only true till around 42 years of age.  At this age we start finding it difficult to read small print clearly and have to start wearing reading glasses. This is know as presbyopia and yes while this is not desirable this is what one would refer to as Normal Eye Power.

What is Anisometropia?

When the eyesight powers are different in each eye, it is known as anisometropia.  Anisometropia must be ruled out in children for the sake of their vision and eye health.  If this is not detected in time, it can lead to what is known as Amblyopia

Amblyopia, also known as lazy eye means that even though the eye structure is normal one or both eyes have poor vision. This condition develops in the first 3-8 years of life and should be treated early.

A few factors can cause development of Amblyopia.  Having a squint or a cataract and not getting it treated or having an eye power and not wearing your glasses.

Can the Eye Power increase?

Eye power can change based on your age. 

Your child’s glasses number can change.  Yes, usually this can increase.  But it’s not that simple.

  1. Myopia or minus eye numbers can increase with age.  Myopia progresssion has become a big issue in todays world and Eye Solutions has thus launched the first of its kind Myopia Control Clinic in South Mumbai.
  2. Hyperopia or plus eye numbers does not increase and, in fact, can reduce a bit up to 6-7 years of age.
  3. Astigmatism or cylindrical number does not increase with age and usually remains the same.

How does the eye power increase?

The actual reason why power increases is an increase in the eyeball length. Suppose the eye grows longer, then the glasses number increases.

As mentioned earlier, ‘ How to reduce eye power‘ or ‘How to improve eye number ?’ are the most common questions we get asked.  Reducing the eye power or improving the eye number is not something we can control.  This increase or decrease happens on its own.  Of course, new research says that an increase in the power of the eye can happen due to the following reasons.

  1. The first reason is genetics. If the parents have a high minus number, then the child's chances of having a high minus number increase.   It is not much you can do about this.
  2. The second factor is the amount of near work.  The use of Ipads and phones falls within this category.  If your child is spending too much time doing these activities, myopia may increase.
  3. The third factor is the amount of outdoor activity.  When we do any outdoor activity, we look at distant things.  This reduces the chances of the power of the eye increasing.

Thus, if one wants to improve the eye number or prevent the eye's power from increasing, they have to reduce their screentime. They also have to increase outdoor play.  These two steps will help protect your eyes from an increasing refractive error.

How to Reduce Eye Number?

Can eye power be reduced?  Well, there is no real way of reducing the eye number.  One can, however, get rid of their glasses by undergoing Lasik eye surgery.  Lasik is done only after 19 years of age. 

You can, however, take steps to decrease the chances of an increase in eye power.  These steps will not improve the eye number or decrease eye power. They will only prevent an increase in eye numbers.

Atropine eye drops

Atropine has ben used in opthalmology for many years. We now know, since a decdade almost, that diluted atropine reduces the chances of myopia progression. It does this by avoiding the stretching of sclera or the white external wall of the eye. 

These drops are used in 0.01% concetration and are suposed to be used once at night in both eyes till the child is 15-17 years old.

You can read more about Myopia control and Atropine eye drops.


These are types of contact lenses, and one wears these while sleeping.  These lenses change the shape of the cornea while we are sleeping.  This change is temporary.  Now, because of this change, when one gets up and removes the contact lens, they can see without glasses.  This clear vision would last until the evening. If one wants to remain glass-free, one must wear these contact lenses every night.  Not many eye doctors use this form of treatment, but it is still available.  This is available at Eye Solutions, and one can read about Orthokeratology.

Bifocal Glasses

Individuals usually wear these glasses over 40 years of age.  In children, they tend to reduce eye strain when seeing near objects. This reduction in strain decreases the chances of Myopia progression.  Now, it’s important to keep in mind that this is a theory, and even though literature does have reports supporting this, these reports are not many.

Blue Light Blocking Glasses

Because of the pandemic, we all got onto the computer for many more hours in the day.  There has been a lot of discussion about these blue light blocking or blue filter glasses.  These lenses provide no additional benefit.  You can read more about blue-light-blocking glasses.

Can eye exercises improve eyesight?

Many claim that eye exercises can help in reducing eyesight power.  Sometimes these eye exercises are referred to as eye yoga.  Some even tell you not to wear glasses because they can be addictive.  There is, however, no evidence to suggest that eye exercises can reduce eyesight power.  We also know that these exercises do not harm your eyes in any way.  So, we tell our patients that if they want to try out eye exercises or eye yoga to improve their eyesight, they can go ahead.  However, they should not stop wearing their glasses as sometimes it can significantly affect eye health and lead to something known as Amblyopia.

How do I know if my child has Eyesight Power?

You may think that your child does not have a vision problem.  Your toddler may not be old enough to read the eye chart, but that shouldn’t stop you from getting his eyes checked. This is where a routine eye check-up becomes important.  This is a comprehensive eye examination where both distance vision and near vision are checked.  It’s important to get your child a baseline eye evaluation for children early in life from an eye specialist.  We recommend an eye exam as early as two months. This is especially true if you have a family history of eye problems or notice anything unusual (like any symptoms below). Since he’s too young to know when something’s wrong with his eyesight or know that he has an eye problem, you have to look for the following symptoms.

  1. Sitting close to the TV while watching
  2. Eyes look crossed or don’t move in unison.
  3. A complaint of headache – the child may tell you his head hurts; other signs include holding his
  4. head and not liking bright lights or loud noises).
  5. Squints or cocks his head to one side when he gazes at something
  6. Shows signs of dizziness (he seems off balance or complains that he sees spots).
  7. Bumps into objects that other kids skillfully avert.
  8. Frequent rubbing or blinking of eyes
  9. Holding objects or books unusually close or far away
  10. Squeezing eyes to see

If your child has any of those symptoms, you should be taking your child to a pediatric ophthalmologist or an eye doctor for a routine eye check-up.

When can I test the eyesight power of my child?

Children need to undergo an eye power test.  This pediatric eye exam is slightly different from what we would do for an adult because the patient is a child.  The eye power check is slightly different for different age groups.

Eye Testing for infants

Babies can see as well as adults regarding focusing ability, colour vision, and depth perception by six months to 2 years. To assess whether your baby’s eyes are developing normally, your eye doctor will use the following tests :

“Fixate and follow” testing determines whether your baby’s eyes can fixate on and follow an object. The object could be a handheld toy as it moves. Infants should be able to fixate on an object soon after birth and follow an object by the time they are three months old.  

Eye Testing for preschool children 

Parents find it interesting that preschool children do not need to know how to read to undergo eye tests. This is true even when they are too young or too shy to verbalize.

Some common eye tests for young children

Lotus symbol chart for young children is like regular adult charts with letters. Except that they have special symbols instead of letters. These symbols include a kite, house, bell, bird, and star.


This test involves shining a light into the eye to look for the reflection from the back of the eye (retina). This test helps eye doctors determine your child’s eyeglass prescription or eye power.

Dilated retinoscopy

After putting eye drops in the child’s eye in this test, a confirmed eyesight number is obtained. This is to get the correct and precise spectacle numbers.  Dilation usually takes around 20 minutes.  Once we dilate to check the eye number, your eye doctor will also examine the retina and the optic nerve.

Frequently Asked Questions ?

Why does my child require glasses?
Your child requires glasses or has an eyesight power because the length of the eyeball is shorter or longer than what is considered normal.

Having glasses does not mean that the eye is weak. Neither does it mean that the parents or children have done something terribly wrong to get this power.
Does the power of the eye increase with age?
Your child requires glasses or has an eyesight power because the length of the eyeball is shorter or longer than what is considered normal.

Having glasses does not mean that the eye is weak. Neither does it mean that the parents or children have done something terribly wrong to get this power.

Myopia can increase with age. Hyperopia and astigmatism usually don't.
How to reduce eye power? If my child wears glasses regularly, will it improve the eye number?
No. Your children’s eye specialist will prescribe glasses to your child so that he or she can see clearly. In younger years glasses are also prescribed so that vision development proceeds normally. Glasses are not prescribed so that the number reduces or wearing glasses will not reduce the eye number.
Are glasses required to be worn all the time?
Usually yes. Sometimes children with myopia don't wear glasses when doing near work and that is fine. As mentioned in the article above there is a theory that not wearing glasses for near may actually reduce the chances of eye power increasing.

However, there is no harm either in wearing the glasses all the time. Hyperopes and children with astigmatism should wear glasses all the time.
Which eye power is dangerous?
If any type of eye power is very high then the chances of having other eye problems increase.  Since Myopia is the most common eye power, a myopic number of more than -6.00D increases the risk of retinal detachment manyfold. Retinal detachment is a serious eye condition.
How bad is 14 eye power for myopia? Will it eventually result in blindness?
A -14.00D eye power would be considered high myopia. Risks of retinal detachment is high. That does not mean one cant live a normal life but should avoid contact sports to avoid minor eye injuries. 

High myopia does not necessarily have to result in blindness. Retinal detachment may lead to blindness but the myopia per se does not lead to blindness.
Can eye exercises achieve what lenses and eye surgery can?
Most likely the answer is No. Eye exercises cannot make the number go away like the Lasik Procedure. There is no evidence as of yes that exercises can make your number go away.  In our practice we have seen many children who do eye yoga and if they do come back we always find the same number. 
Is better vision without glasses possible?
Yes better vision without glasses is possible by one of the following ways.
1. Wearing Contact Lenses
2. Wear OthoK lenses. These leneses are worn at night while you sleep and they are removed in the morning. They change the shape of the cornea and allow you to see clearly in the day without glasses.
3. Lasik - a laser surgery which gets rid of your eye number.
How can I reduce my risk of having less than 20/20 vision?
We think its important to live a normal life without unnecessary worry.  That being said one should be aware of eye problems in the family and also report to your eye doctor for any eye issue. For children its important to limit their screen time.
Can astigmatism get worse?
Yes, Astigmatism can get worse. When it does it is usually associated with an eye condition called Keratoconus. Keratocnus is a progressive eye condition in which the corna protrudes outwards like a cone and affects vision. 

Because Astigmatism can increase we perform a topography for anyone with an astigmatism of more than 2.5D once a year to detect early Keratoconus.
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