Table of Contents

## What does the negative and positive mean in eye prescription?

A “plus” (+) sign in front of the number means you are farsighted, and a “minus” (-) sign means you are nearsighted. These numbers represent diopters, the unit used to measure the correction, or focusing power, of the lens your eye requires.

**How do I convert my glasses prescription?**

Specifically, you would take your right eye sphere power of -3.50 and add it to your add (1.50), resulting in -2.00. For your left eye, you would take -2.75 and add it to 1.50, equalling -1.25. This would result in a right eye of -2.00, -0.75 at 140, and a left eye of -1.25, -0.75 at 140. It is as simple as that.

### Can I convert my contact prescription to glasses?

The answer is no. While they both have the same objective — to correct what eye doctors call “refractive errors” that prevent you from seeing correctly — prescriptions for eyeglasses and contact lenses are distinctly different.

**How do I transpose an opthamologist prescription?**

Transposing a Rx prescription is simply converting the prescription from minus cylinder notation to plus cylinder notation….Transposition

- Add the cylinder power to the sphere power to arrive at the new sphere power.
- Change the sign of the cylinder power.
- Add or subtract 90 from the axis.

## Can you have a positive and negative SPH?

SPH is measured in dioptres and can be written as positive (+) or negative (-) values for each of your eyes.

**Is my contact lens prescription same as glasses?**

Your Two Different Prescriptions However, contacts and glasses prescriptions are actually slightly different because of their distance from your eyes. Eyeglass lenses are placed approximately 12 millimeters away from your eyes, while contact lenses sit directly on your corneas.

### How do I know my glasses prescription from my contacts?

You can find your prescription on the piece of paper given to you by your optician during a check-up, on the end/side of your contact lens box or on the blister packs that contain your contact lenses.

**When do you transpose a prescription?**

Depending on the equipment used by the doctor, a prescription may be in plus or minus cylinder form. For surfacing, the lab uses the minus form, meaning if a prescription is written in a plus cylinder form it must be transposed before processing.

## What does negative cylinder mean in eye prescription?

A plus sign indicates you are farsighted, a minus sign indicates you are nearsighted. The higher the number, the stronger your prescription. Cylinder measures what degree of astigmatism you have, or how flat or irregular the shape of your cornea is.

**Do ophthalmologists use plus or minus cylinder?**

Ophthalmologists work in “plus” cylinder while optometrists like “minus” cylinder. Mathematically, they are the same. Glasses are made to correct a certain amount of spherical error. However, people also have a certain amount of astigmatism that also needs to be corrected.

### What happens if you wear contacts with the wrong prescription?

One of the most common effects of wearing the wrong contact lens prescription is blurry vision. Since contacts are meant to improve vision, the wrong prescription will typically cause impairment in a person’s vision, says the U.S. Food and Drug Administration.

**What do the numbers on my contacts mean?**

One number that remains the same will be the sphere power (like a spherical lens). The second number is the amount of astigmatism, sometimes listed as cylinder or CYL. The third number is meridian or where the astigmatism lies. This is called the axis.

## What does the negative number on contacts mean?

SPHAlso referred to as Power or PWR, this field references the corrective factor of the contact lenses. A negative number, such as -2.25, in this field indicates myopia, (nearsightedness), while a positive number like +2.25 indicates hyperopia (farsightedness).

**Why do I need to convert my cylinder prescription to negative?**

Nowadays the majority of labs, including ours, cut lenses in the negative (-), and require that any positive (+) cylinder prescriptions be converted into the negative (-) equivalent. Rest assured this conversion does not alter the type or quality of the vision correction that your doctor prescribed you.

### What is the positive cylinder for astigmatism?

Eyeglass Prescription Positive Cylinder Conversion Ophthalmologists write astigmatism prescriptions with positive (+) cylinders. Most eyeglass labs, including ours, cut lenses in the negative (-), and require that any positive (+) cylinder prescriptions be converted into the negative (-) equivalent.

**Why do ophthalmologists write positive cylinder prescriptions?**

Eyeglass Prescription Positive Cylinder Conversion. Ophthalmologists and a few older optometrists (different types of eye doctors), write astigmatism prescriptions with positive (+) cylinders. This is because many years ago the instruments used to measure and cut lenses were only able to do so in positive increments.