This is how frame size and PD matter

What is PD?

PD stands for pupillary distance, which is the measurement of the distance between the pupils of the eyes. This distance is an important factor in determining the correct prescription for eyeglasses, as it allows the lenses to be positioned correctly in front of the eyes. Accurate measurement of PD is crucial for ensuring that eyeglasses or contact lenses provide optimal vision correction, as even a small deviation from the correct measurement can result in visual discomfort or even headaches. Optometrists and opticians have special instruments and training to get accurate PD measurements. While many online retailers and affiliate sites encourage consumers to measure their own PD, there is no reason - you can find an optometrist that will provide you with your PD on this site.

What is frame size?

Frame size refers to the physical dimensions of the eyeglasses or frames that hold lenses in front of the eyes. Different individuals have varying frame sizes, which can affect the position and orientation of the lenses relative to the eyes. Since PD is the measurement of the distance between the pupils of the eyes, it follows that individuals with different frame sizes may have different PD measurements. Specifically, larger frames tend to place the lenses further apart from each other. Such a frame is usually suitable for an individual with a larger head who would also usually have a larger PD measurement. Smaller frames tend to position the lenses closer together, suitable for an individual with a smaller head, and therefore who would also typically have a smaller PD measurement. An experienced eyewear professional will ensure that both the frame size and the correct PD measurements are used when providing glasses with corrective lenses.

What are typical frame sizes?

Typical frame sizes can vary widely depending on the individual’s physical characteristics, such as their bone structure, height, weight, and facial features. However, there are generally three categories of frame sizes: small, medium, and large. Small frames typically have a lens width of around 48-52mm, while medium frames range from 52-56mm, and large frames can be 56mm or larger. The height and bridge width of the frames can also vary within each size category, and some frames may be labeled as “wide” or “narrow” to indicate variations in these dimensions. It is important for individuals to select a frame size that is comfortable and fits securely on their face, as well as provides the appropriate lens placement for their PD measurement. Optometrists can help individuals determine the appropriate frame size for their PD measurement during an eye exam.

How is PD measured?

PD can be measured using several different methods. The most common method involves using a pupillometer, which is a handheld device that emits light and measures the distance between the centers of the pupils. The patient is typically instructed to look at a distant object while the optometrist takes the measurement. Another method involves using a millimeter ruler to measure the distance between the centers of the pupils while the patient looks at a mirror. However, manual methods such as this one are considered antiquated as they are more susceptible to error. Some optometrists may also use digital imaging technology to capture an image of the patient’s face and measure PD from the image. Accurate measurement of PD is important for ensuring that eyeglasses or contact lenses provide optimal vision correction, and optometrists typically take multiple measurements to ensure accuracy.

So does frame size affect PD?

Frame size and PD are two different measurements, but they are related because they are both related to the size of the person's head and the relative distance between their eyes. Lenses are made for a specific frame with a patient's specific PD because the distance between the centers of the lenses in the eyeglasses or frames can impact the measurement of the distance between the pupils of the eyes. When the lenses are positioned closer together, the PD measurement will be smaller, while lenses positioned further apart will result in a larger PD measurement. This is because the lenses need to be aligned with the centers of the pupils in order to provide optimal visual correction, and the distance between the lenses can affect this alignment. Therefore, individuals with larger frame sizes may require a larger PD measurement to ensure proper alignment of the lenses, while individuals with smaller frame sizes may require a smaller PD measurement. It is important for optometrists to consider frame size when measuring PD to ensure that the eyeglasses or contact lenses provide the appropriate visual correction.

What should a smart consumer do when purchasing glasses?

When purchasing glasses, it is important for consumers to consider the impact of frame size on PD and to consult with an optometrist to ensure that they receive an accurate measurement. Optometrists are trained to measure PD using specialized tools and techniques, and can provide guidance on selecting the appropriate frame size and style for an individual’s specific needs. Consumers should schedule an appointment with an optometrist for an eye exam and PD measurement, and should discuss their preferences and concerns regarding frame size and style. The optometrist can take into account the individual’s facial features and measurements when recommending a frame size, and can also provide advice on the most appropriate lens material and coatings based on the individual’s lifestyle and vision needs.

In addition to consulting with an optometrist, consumers should also consider the fit and comfort of the glasses when selecting a frame size. A frame that is too large or too small can cause discomfort or even headaches, and may not provide optimal visual correction. Consumers should try on several sizes and styles of frames, taking into account their facial features and PD measurement, to find the best fit and comfort. They should also consider the durability and material of the frames, as well as the type of lenses and coatings that are available. By consulting with an optometrist and considering these factors, consumers can make an informed decision when purchasing glasses and ensure that they receive the best possible visual correction and eye care.

Where can I find an optometrist that will provide my PD?

We maintain a directory at pdplease.com of optometry practices who provide PD measurements as part of their standard eye exam, on request after an eye exam for free, or on request for a fee. Use the map on the main page, or look at our directory to find a location near you!