Contact Lenses -1.75 | What does it stand for

Contact Lenses -1.75 - What Does It Stand For

Contact Lenses -1.75 >> It is the power of the contact lenses you are going to buy for your eyes. This is done by the Contact lenses Prescription. It is done by the EYE Doctor. There are Few Tests, measurements & Calculation while contact lenses Prescription test takes place. It is measured to get the right selection of the contact lenses with right power which one's eyes need for correcting the visionary effects.

First of all, just take a look at the simple chart below. Since we already know that lens power of 4.00 D or greater requires vertexing at each meridian, so we start with 4.00 D = add vertex factor of +0.25 D. For every 2 D power change, you will require a vertex factor change of +0.25 D.
Power of lens Vertex Factor (VF)
4.00 D +0.25 D
6.00 D +0.50 D
8.00 D +0.75 D
10.00 D +1.00 D
12.00 D +1.25 D
14.00 D +1.50 D
16.00 D +1.75 D
Example #1:
OD: -10.00 – 5.00 x 180
OS: +5.00 – 1.00 x 180
Given: Spectacle Rx for OD: -10.00 – 5.00 x 180. What’s the contact lens Rx?
1) Sphere power = -10.00 D –> -10.00 + vertex factor of +1.00 D = -9.00 D at 180th meridian
2) Sphere + Cylinder power = -10.00 – 5.00 = -15.00 D –> -15.00 + VF of +1.50 = -13.50 D at 90th meridian
3) Adjusted Cylinder power = -5.00 D + VF of +1.50 = -3.50 D
4) Estimated Rx = -9.00 – 3.50 x 180 (Need to ADD -0.25 to cylinder power to obtain the Final Rx)
5) Final Rx = -9.00 – 3.75 x 180

Given: Spectacle Rx for OS: +5.00 – 1.00 x 180. What’s the contact lens Rx?
1) Sphere power = +5.00 D –> +5.00 + vertex factor of +0.25 D = +5.25 D at 180th meridian
2) Sphere + Cylinder power = +5.00 – 1.00 = +4.00 D –> +4.00 + VF of +0.25 = +4.25 D at 90th meridian
3) Adjusted Cylinder power = -1.00 D + VF of +0.25 = -0.75 D
4) Estimated Rx = +5.25 – 0.75 x 180 (Need to ADD -0.25 to cylinder power to obtain the Final Rx)
5) Final Rx = +5.25 – 1.00 x 180

Useful Notes:
a) Spectacle plane –> Contact lens plane
(Remember: “CAP” = Closer ADD Plus!!!)
b) Minus spectacle Rx –> contact lens Rx (CLRx) = expect contact lens Rx to be LESS minus.
Ex: SRx = -4.50 D –> CL Rx = -4.25 D
c) Plus spectacle Rx –> contact lens Rx = expect contact lens Rx to be MORE plus.
Ex: SRx = +5.00 D –> CLRx = +5.25 D
- See more at: http://www.optometrystudents.com/pearl/how-to-rapidly-determine-a-contact-lens-prescription/#sthash.vWKP6NKA.dpuf

The formula for a contact lens prescription describes the amount of refractive error from normal vision. This article will show you how to read a contact lens prescription.

O.D. : -  This stands for Oculus Dexter, a Latin term for right eye. All of the numbers next to this row or column indicate the strength of correction needed for your right eye.

O.S. : - This stands for Oculus Sinister, a Latin term for left eye. All of the numbers following this row or column indicate the strength of correction needed for your left eye.

Power (PWR) or Sphere. They are usually the first set of numbers listed in the OD and OS rows/columns. It is common for the correction to differ between the right and left eyes. If you find the term PL, this stands for Plano, and it means the number is 0 and no correction is needed .

A negative number in this field indicates myopia, otherwise known as nearsightedness or the ability to see things clearly when they are close to you, but not when they are far away. For example, if the field under OD reads -1.75 D, this indicates the person has  diopters of nearsightedness in the right eye.

A positive number in this field indicates hyperopia, otherwise known as farsightedness, or the ability to see well in the distance, but not nearby. For example, if the field under OD reads +1.75, this indicates the person has 1.75 diopters of farsightedness in the right eye.

CYL and AXIS. These numbers indicate astigmatism, a common condition. It is usually caused by an irregularly shaped cornea, but can also be caused by an irregularly shaped lens inside the eye.

CLY stands for cylinder and it is the measure of astigmatism in diopters. Most doctors use a positive number, but if a negative number is given, a lens store may need to convert to a positive number.

AXIS is the degree measurement that is required to bend light to correct the irregular shape of the cornea.

All of the above calculation are taken place before prescribing for contact lenses for particular eyes. There are some other factors which also necessary for the right prescription of the contact lenses. 

First of all, just take a look at the simple chart below. Since we already know that lens power of 4.00 D or greater requires vertexing at each meridian, so we start with 4.00 D = add vertex factor of +0.25 D. For every 2 D power change, you will require a vertex factor change of +0.25 D.
Power of lens Vertex Factor (VF)
4.00 D +0.25 D
6.00 D +0.50 D
8.00 D +0.75 D
10.00 D +1.00 D
12.00 D +1.25 D
14.00 D +1.50 D
16.00 D +1.75 D
Example #1:
OD: -10.00 – 5.00 x 180
OS: +5.00 – 1.00 x 180
Given: Spectacle Rx for OD: -10.00 – 5.00 x 180. What’s the contact lens Rx?
1) Sphere power = -10.00 D –> -10.00 + vertex factor of +1.00 D = -9.00 D at 180th meridian
2) Sphere + Cylinder power = -10.00 – 5.00 = -15.00 D –> -15.00 + VF of +1.50 = -13.50 D at 90th meridian
3) Adjusted Cylinder power = -5.00 D + VF of +1.50 = -3.50 D
4) Estimated Rx = -9.00 – 3.50 x 180 (Need to ADD -0.25 to cylinder power to obtain the Final Rx)
5) Final Rx = -9.00 – 3.75 x 180

Given: Spectacle Rx for OS: +5.00 – 1.00 x 180. What’s the contact lens Rx?
1) Sphere power = +5.00 D –> +5.00 + vertex factor of +0.25 D = +5.25 D at 180th meridian
2) Sphere + Cylinder power = +5.00 – 1.00 = +4.00 D –> +4.00 + VF of +0.25 = +4.25 D at 90th meridian
3) Adjusted Cylinder power = -1.00 D + VF of +0.25 = -0.75 D
4) Estimated Rx = +5.25 – 0.75 x 180 (Need to ADD -0.25 to cylinder power to obtain the Final Rx)
5) Final Rx = +5.25 – 1.00 x 180

Useful Notes:
a) Spectacle plane –> Contact lens plane
(Remember: “CAP” = Closer ADD Plus!!!)
b) Minus spectacle Rx –> contact lens Rx (CLRx) = expect contact lens Rx to be LESS minus.
Ex: SRx = -4.50 D –> CL Rx = -4.25 D
c) Plus spectacle Rx –> contact lens Rx = expect contact lens Rx to be MORE plus.
Ex: SRx = +5.00 D –> CLRx = +5.25 D
- See more at: http://www.optometrystudents.com/pearl/how-to-rapidly-determine-a-contact-lens-prescription/#sthash.vWKP6NKA.dpuf

Contact Lenses | Benefits | Uses | What is It?

Contact Lenses

Contact lenses are closer to natural sight than eyeglasses. They move with your eye and correct the refractive error closer to the eye to allow for a more natural field of vision. They don't get in the way of your line of sight, like glasses can. Contact lenses can be worn all day, or even several weeks at a time, so you don't have to worry about putting them on and taking them off.

What is the Principal Behind Contact Lenses

The principles of refraction and related to optics are similarly applied to contact lenses. This contains the correction of current defect by replacing the contact lens surface with corneal curvature which accured in accordance with the degree of myopia and hypermetropia. Since the major part of astigmatic defects develop due to the distortion of frontal layer of cornea, either hard or special soft lenses produced only for astigmatism shall be used. 

Cases In which Contact Lenses are Used

Farsightedness / Hyperopia: -  People with hyperopia can see clearly far away, but their close-up vision is blurry. To correct hyperopia, the lens is thicker at the center and thinner at the edges. These lenses are called plus, or convex. The lens bends the light toward the center and moves the focal point back so that light is focused on, rather than behind, the retina.

2 Types of Contact Lenses

• The Gas permeable hard lenses
• Soft Lenses   

Contact lenses are not one-size-fits-all, and constant "lens awareness" could indicate a poorly fitting lens. Lenses come in thousands of combinations of diameter and curvature. If your lenses have the wrong diameter or curve, you'll likely feel that something is always in your eye. If the lenses are too large, your eyelids will tend to dislodge them when you blink. The wrong size lenses can even cause abrasion of your cornea.

Wearing contact lenses should be a comfortable alternative to wearing regular glasses to aid in improving vision.  Yet sometimes people don't receive the desired benefits of wearing contact lenses.  So Make sure you are not getting any problem after wearing Contact lenses.