Pupillary Distance & Frame Size. Does It Matter? All You Need to Know

Last Updated on May 16, 2023 by amy

Understanding your pupillary distance might seem overwhelming, especially when it is only one of the many words used in terminology related to your eye health. Simply stated, pupillary distance is the distance between the pupils of the eyes, center to center, measured in millimeters. If you are in the market to purchase new eyeglasses, whether in-store or online, you will be asked about your pupillary distance measurement. This measurement is crucial because it determines the shape and alignment of your corrective lenses for your prescription eyeglasses. Your corrective lenses may not be efficient if you don’t have a proper pupillary distance measurement. Here is everything you need to know about your pupillary distance.

Reading Your Pupillary Distance
There are different ways to measure your pupillary distance. Most adults have a pupillary distance of 54-68 mm. In comparison, a child’s pupillary distance might be within the range of 41-55 mm. The different measurement methods to determine your pupillary distance are binocular and monocular. The binocular method is a pupil-to-pupil measurement; the monocular method is a per-eye measurement. The monocular measurement for pupillary distance is often used when a face is not symmetrical, i.e. one eye is closer or farther from the middle of one’s face. Your eye care professional will determine the best method to produce an accurate pupillary distance measurement. Once they determine your pupillary distance, they may document it in your medical chart. Sometimes eye care professionals do not include your pupillary distance on your prescription. If this is the case, it is best to request a measurement of your pupillary distance and/or for them to specify what it is on your prescription. However, you can also obtain an accurate pupillary distance measurement independently.

Measuring Your Pupillary Distance
Eye doctors may be reluctant to release your pupillary distance because they don’t want you to purchase corrective eyewear other than in their office. If this is the case, you can conduct a pupillary distance measurement on your own. This is also very important to get your pupillary distance measurement if you purchase eyewear online. Every set of lenses has an optical center determined by pupillary distance, which you must provide to ensure precise lenses. You will need a mirror and a millimeter ruler to measure your pupillary distance accurately.

First, stand eight inches from a well-lit mirror to measure your pupillary distance. Begin by looking straight forward in the mirror. Stand straight and hold the millimeter ruler against your brow line. It is good practice to pretend the ruler is like a pair of glasses, ensuring an exact pupillary distance measurement. Then close your right eye. Align the ruler’s zero to the center of your left pupil. While looking forward, close your left eye, then open your right eye. Next, read the millimeter line. The line aligned with the center of your right pupil is your pupillary distance.

It is good practice to measure three to four times for an accurate pupillary distance before using your measurements to make a purchase.

Another way to measure your pupillary distance is to use a friend. The method is like measuring your pupillary distance yourself, except your friend will assist you by reading the ruler. The first step in measuring your pupillary distance with a friend is to look straight ahead with both eyes open. Ensure your friend accurately measures your pupillary distance by aligning the millimeter ruler’s zero over the center of one pupil. Then measure the distance to the center of the other pupil. This method may be used in addition to measuring your pupillary distance on your own as it can declare accuracy. Be sure to write down your pupillary distance once you are done measuring so you have it for future purchases. Your pupillary distance shouldn’t change over time, but checking if you change frame shapes is a good idea.

Your pupillary distance must be as accurate as possible. Sometimes even your eye care professional can make a mistake in the measurements, and checking for accuracy is always a good idea. The important thing to consider about your pupillary distance is its relevance to correcting your vision. Many think a corrective lens alone can be an effective way to adjust someone’s sight. However, the corrective lenses would be useless without a correct pupillary distance measurement. The pupillary distance is needed to make a pair of prescription eyeglasses align with the optical center of each lens. This means if an accurate pupillary distance measurement is not taken, your eyes won’t be able to focus correctly. Opticians strongly suggest taking an accurate measurement and not estimating your pupillary distance.

Mistaken Pupillary Distance
Inaccurate pupillary distance measurement can affect your overall well-being. This is especially true if you wear corrective lenses because of being myopic or have exceptionally high astigmatism. Symptoms of an improper pupillary distance might include blurry vision, double-vision images, headaches, nausea, and even fatigue. Even the slightest error in a pupillary distance measurement for a strong prescription could cause frequent headaches. The discomfort caused by an incorrect pupillary distance may be hard to diagnose because the symptoms mimic other conditions.

An accurate pupillary distance measurement is important in high myopia or astigmatism correction because of the eye’s changing optical properties, which is also directly related to what part of the lens you look through. Consider an experiment to see how a varied optical center affects your vision. Begin by moving your glasses slowly in front of your eyes while focusing on something. Things may look a bit pinched, or the clarity may be different. This is because your eyes are not fixated on their optical center. The light hits your retina differently the further you are from the optical center of the lens, and any variation will make objects appear dissimilar. Any prolonged obscurity in the optical center makes the visual cortex in your brain work overtime. Thus, the brain becomes fatigued, which can result in headaches since vision happens in your brain. Therefore, the brain must work harder when an inaccurate pupillary distance is prescribed.

Another thing to consider is pupillary distance can be a varied occurrence, i.e., it is not static. This is because we are constantly viewing objects at different distances. When you view something at a distance, your pupils are slightly wider apart; on the contrary, the pupils are closer together when looking at images close-up. Your pupillary distance is always lower when viewing things close-up.

Visually Correct
One thing that is often overlooked regarding pupillary distance is the frame measurements. Different frames can affect a pupillary distance because of the differentiation in the optical center. This is especially true with larger lenses and frames that may rest on a face differently. This makes finding an adequately fitted frame as important as taking an accurate pupillary distance measurement. The best way to do this is to refer to an older pair of eyewear that fits well. Getting the right frame fit is very important to purchase any eyewear online.

There are five areas to consider when measuring your frames for an accurate fit: the frame width, lens height, lens width, temple arms, and the bridge. The frame width measures the entire horizontal front of the frame. Extend from one side to the next when measuring this area. The vertical height of the lens is the lens height. Often referred to as “eye size,” the lens width is the horizontal diameter of a lens. The part “arms” connecting the frame to your ear are the temple arms. Finally, the bridge area is part of the frame that rests on the bridge of your nose. Be sure to check an old frame, as they might include frame dimensions to assist you in determining the frame size.

Before making your next purchase, determine what type of frame fits your style and function best. The next step is to compare that frame shape to an old pair of frames. Then you can begin to measure the frames and your pupillary distance accurately. It is important to remember to be prepared with accurate measurements no matter where you decide to buy frames and lenses. Pupillary distance is the measurement that specifies the space between your two pupils and will assist in creating your optical center. Thus, offering your eyes the best opportunity to focus. An accurate pupillary distance shared with a proper frame fit will drastically enhance your experience in your next pair of eyewear.