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Long-sightedness and Short-sightedness

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Author : Dr Deepak Garg

Healthy Eyes

For the stress-free and all-around performance at whatever work we do, it is important to have a clear and healthy vision. Clear vision is linked to improved quality of life and helps us to enjoy life to the fullest. Our eyes are exceptionally well-designed camera that uses simple yet intricate optics to make us see clearly. First, there is a clear layer called the cornea, then the lens and the focusing ability of our muscles which eventually projects the light on the retina (the back of the eye). The optic nerve then takes the information to the brain where vision is accomplished and we see clear 6/6 vision.

Thus, any problems with light either entering the eye or focussing the light on the retina may cause decreased vision especially if the light is either getting focused in front of the retina (causes short-sightedness) or behind the retina (causes long-sightedness). These errors in focussing the light on the retina are known as refractive errors or eye power and can be corrected by using different specifically designed lenses. 

What is Long sightedness or Hypermetropia? 

As the name suggests, long-sightedness means your long-vision (ability to see things in the distance) is good, while your near-vision (ability to see things up close) is blurry. Interestingly, the medical literature has shown that we all are born long-sighted with a certain degree of power and as we get older and reach 5-6 years of age, the number tends to go away because of the process known as emmetropization. The medical name for long sightedness is hypermetropia. Thus, many of us are a little bit long-sighted without even realizing it, only significant long-sightedness will cause blurry vision, headaches, and tired, achy eyes. Long-sightedness is often compensated for in our youth to some degree by the muscles in our eyes. However, as we age even further, this ability is reduced, and by our mid-40s reading glasses are required to help us to read. The condition is known as Presbyopia which is not an error but a natural aging process.

Hyperopia
Rays of light meeting behind the retina

Causes of Long Sightedness:

Our eyes are well adapted and accommodated to focus the distant objects on the retina. While we are young (, our lens has the flexibility to focus and adjust the light rays entering the eye from near objects, on the retina. However, due to long-sightedness, this focusability is not enough to make the light rays fall on the retina, thus instead, they end up falling behind the eye and the near objects appear blurry. 

The reasons for this to happen may be any of the following:

1. The eyeball is too short.

2. The front transparent layer of the eye i.e. cornea is too flat.

3. The lens inside the eye is unable to focus the light rays correctly on the retina.

Symptoms of Long Sightedness or hypermetropia:

In very young kids, the long-sightedness may not manifest any symptoms due to the flexibility of the lens. Commonly reported symptoms by patients having long-sightedness are:

1. Fuzzy/blurry near vision

2. need to squint the eyes to see clearly

3. Headache (around the eyes)

4. Pulling sensation or heaviness in eyes.

How do you correct  Long Sightedness naturally?

Apart from surgical procedures (LASIK), which are not recommended in children below the age of 18 years, certain spectacles and contact lenses can be prescribed until they become eligible for the surgical option. Moreover, children and young adults with long-sightedness may not need any treatment, as their eyes are often able to adapt to the problem and their vision may not be significantly affected. Only when the focusing system of the eyes fails to project the light rays properly on the eye, a correction is required. The main treatment to correct long-sightedness is prescription glasses. 

Which lens is used for the treatment of Long Sightedness?   

The glasses or contact lenses prescribed to correct long-sightedness has plus power that ensures light is focused onto the back of your eyes (retina) correctly.  They are known as convex lenses.

What is Short-sightedness or Myopia?

Short-sightedness is the exact opposite of long-sightedness which means, your far away vision is blurry but near vision is clear. The medical name for short-sightedness is myopia. Short-sightedness is a very common problem that can be corrected and even managed. Affecting 21.15% of school-going children (aged between 5-15 years) in urban India, myopia (short-sightedness) is a condition of concern as compared to hypermetropia (long-sightedness). In fact, WHO has estimated that by 2050, half of the world's population would be myopic, if not addressed appropriately. Certain studies done post-pandemic have reported a sudden surge in the cases of myopia globally, due to home confinements which lead to increased screen time caused by the lockdowns. 

Myopia
Rays of light meeting in front of the retina

Causes of Short Sightedness:

Generally, in myopia, the length of the eyeball is too long, such that the light rays entering the eye focus in front of the retina (opposite of hypermetropia), thus causing blurred vision. The exact cause of myopia, after more than 400 years of research remains unclear, however, we have medical evidence that links the following most common causes to myopia:

  1. Genetics - If one or both parents have myopia, the child may also develop myopia.
  2. Environmental factors: Children who tend to spend longer time using computer/phone/iPad screens are at more risk of developing minus power (myopia). (This explains, the post-pandemic surge in cases of myopia.)
  3. We also have evidence that says, that the lack of time outdoors in natural light may increase the chances of developing myopia. Thus, children are encouraged to be involved in outdoor sports.
  4. Certain illnesses like diabetes have also been linked to inducing a temporary form of myopia.

Symptoms of Short Sightedness or myopia.

Typically, myopia manifests during the early school years; the child may exhibit the following symptoms:

  1. Difficulty seeing far away objects, especially the projector/black/whiteboard in school.
  2. The child partially closes his/her eyes (squeezing) to see clearly.
  3. Commonly, the child may also complain of headaches caused due to eye strain.

How to cure Short Sightedness or Myopia permanently?

Since there still exists an ambiguity about the exact reason why myopia occurs, there is no sure shot "cure" for myopia, i.e. minus power once manifested cannot be reversed. However, based on the research done to understand how myopia occurs, we have strategies to make sure the minus power does not increase. Thus, your optometrist/ophthalmologist would ideally suggest options to control or manage the minus power, thus the strategies are known as "Myopia Management Strategies". There are two companies whose lenses have become popular for myopia control. One is Hoya which makes Miyosmart lenses and other the other is Zeiss which makes Myokids Pro and Myovision Pro.

Myopia Control
Miyosmart Glasses

Myopia can also be removed by performing Lasik eye surgery. This is a laser that reshapes the front surface of the eye and gets rid of glasses.

Steps of Lasik
Steps of Lasik Eye Surgery

Which lens is used for the treatment of Short Sightedness?

As discussed earlier, short-sightedness can be easily corrected using concave lenses or minus-powered lenses. The minus power can be incorporated either in spectacles or contact lenses. With contact lenses, parents are usually concerned about potential infections in the eye, however, studies done on the safety of contact lens wear in children demonstrated no extra risk of infections as compared to adults. The regular minus-powered lenses are a corrective option and have been found to not control myopia at all. Thus, well-renowned companies like Carl Zeiss and Hoya, have specialized myopia control spectacle lenses that reduce the risk of myopia progression. Consult your eye care professional to know more about them. 

Frequently asked questions

1. Difference between short-sightedness and long-sightedness?

Short-sightedness or Myopia is a type of refractive error in which the distance vision becomes blurry and is corrected using minus-powered lenses, whereas, in long-sightedness or hypermetropia, the near vision becomes blurry and is corrected using plus-powered lenses.

2. Can laser eye surgery fix short and long-sightedness?

Yes, laser eye surgery can fix both short and long-sightedness, however, candidature for laser surgeries is decided based on a battery of tests. Consult your eye care professional and make an informed decision.

3. What is long-sightedness also known as?

The medical name for long-sightedness is Hypermetropia.

4. What is short-sightedness also known as?

The medical name for short-sightedness is Myopia.

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