Beginner's Guide: Spherical & Cylindrical Lenses | PPT

We understand that vision health is of utmost importance to everyone, and we are here to provide you with the answers you seek. This guide will address the common eye power-related questions that we frequently receive.

1. What Does Having Eye Power Mean?

Having eye power means your eyes have a shape such that the rays of light do not focus on the back part of the eye called the retina. Thus, to make them focus on the retina, you need specific lenses in front of your eyes, either spectacles or contact lenses. The power of the eye is denoted by the power of the lens used to make you see clearly. The power of the eye can be of three types: Plus number or hyperopia, minus number or myopia, and cylindrical number or astigmatism.

2. What Does Negative Eye Power Mean?

Negative eye power means you need a negative lens or a minus-powered lens to make the rays of light focus on the retina. In other words, a minus-numbered lens will help you see clearly. This type of power is found in individuals complaining of having blurry distance vision. The medical term for negative eye power is Myopia, and it has become a topic of interest in recent years because it is expected that half the world&#;s population will have negative eye numbers by . This is the most common type of eye power seen in the population. The eye number can progress, and there are certain tools available to help reduce the risk of this progression. It is also a common reason why people undergo Lasik eye surgery or Clear lens extraction.

3. What Does Positive Eye Power Mean?

Like negative eye power, positive eye power means you need a positive or plus-powered lens to focus the rays of light on the retina. This type of power is found in individuals complaining of blurry near vision. The medical term for positive eye power is Hypermetropia. Although it is not considered as big a concern as negative power, if undetected at a young age, it may cause a condition known as lazy eye or amblyopia. All humans are born with around +2.00 numbers, which is why eye doctors put certain drops in babies to determine their exact power and decide on the prescription that should be given, if needed.

4. What Does Cylindrical Power Mean?

Cylindrical power arises when the shape of the cornea, the frontmost layer of the eye, is like an oblate rugby ball shape, instead of being a regular spherical shape. This shape causes the power to be manifested only in a particular orientation called the axis. It does not mean that the eyes are weak or that there is a defect; it simply means the eyes have such a shape that the person needs a cylindrical number to see clearly. 

Abnormally high cylindrical numbers (>3.00) may indicate a condition called keratoconus, so the patients who have cylindrical eyesight of greater than 3 diopters undergo a test called topography once a year to make sure they have not developed keratoconus.

5. What Does Spherical Number in the Eye Mean?

Spherical power means the rays of light are not getting focused on the retina. They are either getting focused in front or at the back of the eye. Here, the shape of the cornea is regular, and the blur that the individual sees is a complete blur instead of the glare and shadowing effect seen in cylindrical power. Both Myopia and hyperopia are types of spherical powers.

6. What Does 6/6 Mean?

6/6 (read as 6 by 6) is a notation used in eye care to quantify your vision. &#;6&#; in the numerator stands for 6 meters, which is the testing distance, i.e., how far you are sitting when your eye test is being performed. The denominator denotes the ideal distance at which a person with no eye power must be able to see the line. Thus, ideal vision is 6/6 or 20/20. 20 refers to 20 feet, which is equal to 6 meters. It means that a person can see letters from a distance of 6 meters, which they are supposed to see from a distance of 6 meters. 6/9 means that a person can see letters from a distance of 6 meters, which they are actually supposed to see from a distance of 9 meters. 6/12 means that a person can see letters from a distance of 6 meters, which they are actually supposed to see from a distance of 12 meters, and so on. 

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7. My Eye Doctor Prescribed Me Powered Glasses. What Does It Mean?

Depending on your eye power, your eye doctor will prescribe you to wear either negative or positive power glasses. The lenses in your spectacles or contact lenses will have the power to help you see better. You could have a spherical power or a cylindrical power. The spherical power could be a plus power or a minus power.

Some Common Specific Questions 

People ask us specific questions about their eye powers most of the time. One of these questions is, 

• What does 0.25 eye power mean?
• What does 0.5 eye power mean?
• What does 0.50 eye power mean?
• What does 0.75 eye power mean? 
• What does 1.25 eye power mean? 
• What does minus 2 eye power mean?

I will answer all together. 

When one has eye power, they can&#;t see clearly without glasses. The rays of light entering the eye are not focusing on the retina because either the eye is longer or shorter than normal. In other words, the shape is not the perfect shape that the eye should be.

To see clearly, we have to do something which will focus the rays of light on the retina, and we achieve this by giving lenses. Lenses could be in the form of spectacle lenses or contact lenses. 

0.25, 0.5, 0.75, and 1.25 are different eye powers, and it means that you have to wear lenses of these powers so that you see clearly. It does not mean that your eyes have a defect or are weak; it only means that the shape of the eye is slightly different than what it should ideally be. 

A person with an eye power of 5 or -5 has an eye that is much longer than somebody who has a power of -1 or -2. Similarly, a person having a power of -7 has an eye that is much longer than a person who has a power of -5.

PRO TIP: 0.25 and 0.50 are considered very small numbers, and there is a high chance that a person with such numbers would be able to see almost everything without glasses too. Not wearing glasses is not going to harm your eyes in any way, so if you prefer not to wear glasses for such small numbers, it is totally okay to do so.At Eye Solutions, we specialise in providing comprehensive eye care services, ranging from thorough eye examinations to advanced surgical procedures, in Mumbai & Chennai. In case you are facing any &#;Eye Conditions,&#; we urge you to schedule an appointment with our esteemed eye hospital in Mumbai & Chennai, where our top-notch team of eye specialists is ready to assist you.

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