Go the Distance: Understanding Vertex Distance
- BY Catherine Ong
- IN Eye Care
Have you ever wondered why some people push up their glasses to see clearly? Have you wondered why your contact lens and glasses prescriptions don’t match? Why is it important to have the proper fitting for high prescription glasses? The answer can be found in vertex distance and we’ll dive into it in this blog post.
Photo by Mikhail Nilov
What is Vertex Distance?
Vertex distance refers to the distance between the back surface of your eyeglass lenses or contact lenses and your eyes when you are wearing them. It’s an essential factor in ensuring that your prescription lenses provide you with clear and comfortable vision.
How does Vertex Distance Work?
Vertex distance has everything to do with how light bends. Light can converge or diverge through a lens and will continue in that same direction until it reaches another refractive body such as your cornea or your crystalline lens. The farther one your lenses are from your eye, the more time the light has to converge or diverge, thus affecting the perceived power of the lens.
Photo by SHVETS production
Who Does Vertex Distance Impact?
The higher your prescription is, the greater effect any changes in vertex distance will have on your perception. For prescriptions lower in magnitude than ±4.00 (either plus or minus), the difference is almost negligible and you don’t have to worry as much.
However, prescriptions higher than ±4.00 can be more susceptible to changes in vertex distance. This can also come into play especially with contact lenses. People with glasses prescriptions at or above ±4.00 may notice that their glasses prescription and contact lens prescriptions don’t always match – minus powers become lower and plus powers become higher. It’s all due to vertex distance!
Photo by PNW Production
Importance of Correct Vertex Distance
1. Vision Accuracy:
Maintaining the correct vertex distance is crucial for ensuring that your prescription lenses provide you with accurate vision correction. If the lenses are too far from your eyes, the effective power of a minus lens will be minimized and the effective power of a plus lens will be amplified, leading to blurry or distorted vision. The opposite is true when the lenses are too close to your eyes. The difference in power will also affect how the focusing mechanism in your eyes have to compensate, which can lead to increased eye strain and discomfort.
2. Comfort and Fit:
In addition to affecting vision accuracy, the vertex distance also plays a role in the comfort and fit of your eyewear. Lenses that are positioned too far from your eyes may feel loose or unstable, while lenses that are too close may cause discomfort or irritation. Ensuring the proper vertex distance can help optimize the fit of your glasses or contact lenses, ensuring a comfortable wearing experience.
Photo by Ksenia Chernaya
Vertex distance is a critical factor in the effectiveness of your prescription lenses. By understanding its impact on vision correction and comfort, you can ensure that your glasses or contact lenses provide you with the clear and comfortable vision you need for your daily activities. If you have any concerns about the vertex distance of your prescription lenses, be sure to consult with your optometrist or eye care professional for guidance and assistance.
